Phase II Randomized Trial of Carboplatin, Pemetrexed, and Bevacizumab With and Without Atezolizumab in Stage IV Nonsquamous Non-Small-Cell Lung Cancer Patients Who Harbor a Sensitizing EGFR Mutation or Have Never Smoked

INTRODUCTION

Patients with non-small-cell lung cancer (NSCLC) who have never smoked or have tumors with mutations in EGFR generally derive minimal benefit from single-agent PD-1/PD-L1 checkpoint inhibitors. Prior data indicate that adding PD-L1 inhibition to anti-VEGF and cytotoxic chemotherapy may be a promising approach to overcoming immunotherapy resistance in these patients, however prospective validation is needed. This trial in progress (NCT03786692) is evaluating patients with stage IV NSCLC who have never smoked or who have tumors with sensitizing EGFR alterations to determine if a 4-drug combination of atezolizumab, carboplatin, pemetrexed, and bevacizumab can improve outcomes compared to carboplatin, pemetrexed and bevacizumab without atezolizumab.

METHODS

This is a randomized, phase II, multicenter study evaluating carboplatin, pemetrexed, bevacizumab with and without atezolizumab in 117 patients with stage IV nonsquamous NSCLC. Randomization is 2 to 1 favoring the atezolizumab containing arm. Eligible patients include: 1) those with tumors with sensitizing EGFR alterations in exons 19 or 21 or 2) patients who have never smoked and have wild-type tumors (ie, no EGFR, ALK or ROS1 alterations). Patients are defined as having never smoked if they have smoked less than 100 cigarettes in a lifetime. Patients with EGFR-mutated tumors must have disease progression or intolerance to prior tyrosine kinase inhibitor (TKI) therapy. The primary endpoint is progression-free survival (PFS). Secondary endpoints include overall survival (OS), response rate, duration of response, and time to response.

CONCLUSION

This phase II trial is accruing patients at U.S. sites through the National Comprehensive Cancer Network (NCCN). The trial opened in August 2019 and accrual is expected to be completed in the Fall of 2024.

Phthalocyanine-Blue Nanoparticles for the Direct Visualization of Tumors with White Light Illumination

The current standard of care for colon cancer surveillance relies heavily on white light endoscopy (WLE). However, dysplastic lesions that are not visible to the naked eye are often missed when conventional WLE equipment is used. Although dye-based chromoendoscopy shows promise, current dyes cannot delineate tumor tissues from surrounding healthy tissues accurately. The goal of the present study was to screen various phthalocyanine (PC) dye-loaded micelles for their ability to improve the direct visualization of tumor tissues under white light following intravenous administration. Zinc PC (tetra-tert-butyl)-loaded micelles were identified as the optimal formulation. Their accumulation within syngeneic breast tumors led the tumors to turn dark blue in color, making them clearly visible to the naked eye. These micelles were similarly able to turn spontaneous colorectal adenomas in Apc+/Min mice a dark blue color for easy identification and could enable clinicians to more effectively detect and remove colonic polyps.

Folic Acid Supplementation Promotes Hypomethylation in Both the Inflamed Colonic Mucosa and Colitis-Associated Dysplasia

PURPOSE

The purpose of this study was to assess the effect of folic acid (FA) supplementation on colitis-associated colorectal cancer (CRC) using the azoxymethane/dextran sulfate sodium (AOM/DSS) model.

METHODS

Mice were fed a chow containing 2 mg/kg FA at baseline and randomized after the first DSS treatment to receive 0, 2, or 8 mg/kg FA chow for 16 weeks. Colon tissue was collected for histopathological evaluation, genome-wide methylation analyses (Digital Restriction Enzyme Assay of Methylation), and gene expression profiling (RNA-Seq).

RESULTS

A dose-dependent increase in the multiplicity of colonic dysplasias was observed, with the multiplicity of total and polypoid dysplasias higher (64% and 225%, respectively) in the 8 mg FA vs. the 0 mg FA group (p < 0.001). Polypoid dysplasias were hypomethylated, as compared to the non-neoplastic colonic mucosa (p < 0.05), irrespective of FA treatment. The colonic mucosa of the 8 mg FA group was markedly hypomethylated as compared to the 0 mg FA group. Differential methylation of genes involved in Wnt/β-catenin and MAPK signaling resulted in corresponding alterations in gene expression within the colonic mucosa.

CONCLUSIONS

High-dose FA created an altered epigenetic field effect within the non-neoplastic colonic mucosa. The observed decrease in site-specific DNA methylation altered oncogenic pathways and promoted colitis-associated CRC.

Abstract 1797: Impact of estrogen depletion using an aromatase inhibitor (AI) on EGFR-mutated non-small cell lung cancer (NSCLC) in a murine model

EGFR-mutated lung tumors respond poorly to checkpoint (PD-1/PD-L1) inhibitors. Resistance to such therapies has been attributed to the prototypic immunosuppressed “cold” tumor microenvironment (TME) of EGFR-mutated NSCLCs, which is characterized by low levels of tumor infiltrating lymphocytes. Growing evidence from breast cancer studies demonstrates the ability of 17β-estradiol to regulate several species of immune cells within an immunosuppressive TME. Furthermore, treatment of breast cancers with AIs or estrogen receptor antagonists promotes lymphocyte infiltration and enhances immune reactivity. While the role of estrogen species in lung tumorigenesis is well documented, little attention has been given to their contribution to the immunosuppressed lung TME or the use of estrogen-modulating agents to attenuate these effects. The goal of this study was to evaluate the impact of estrogen depletion, using the AI exemestane (Exe), on levels of tumor infiltrating immune cells and other tumor endpoints in the murine model of mutated EGFRL858R NSCLC. Male (n = 42) and female (n = 39) mutEGFRL858R mice were gonadectomized at 6 weeks of age and doxycycline-supplemented chow was given to induce lung tumor development. Daily treatment with Exe (250 μg/kg) or vehicle was initiated at 8 weeks of age, and continued for the duration of the experiment (7 weeks). Body weights were recorded twice per week. At the time of euthanasia, lung tissues were processed for histopathological analysis and assessment of tumor CD8+ lymphocyte concentrations by immunohistochemistry was performed. Lung tumors from Exe-treated mice exhibited higher concentrations (median, Q1 - Q3) of CD8+ T cells per 20x field (77.5, 60.3 - 114.0) vs. those of vehicle-treated controls (61.0, 48.8 - 80.8) (P = 0.035). A trend of a decreased incidence of solid adenocarcinoma lesions within the lungs of Exe-treated vs. vehicle-treated control mice was observed in both males (26.3% vs. 38.1%) and females (26.3% vs. 35.0%). Among females, the incidence of continuous weight loss (over 3 consecutive weeks) was lower among Exe-treated (16.7%) vs. vehicle-treated (40.0%) mice. Early findings suggest that administration of AI therapy to mutEGFRL858R mice stimulates CD8+ lymphocyte infiltration within lung tumors, and inhibits both the formation of lung adenocarcinomas and disease-associated weight loss. Murine studies to further optimize the dose and schedule of AI treatment, as well as evaluate the ability of AI therapy to enhance the activity of checkpoint inhibitors in mutated EGFRL858R NSCLC are underway. (Supported by an In Vino Vita Award from Fox Chase Cancer Center and a R01 CA217161 from the NCI/NIH.)

Citation Format: J. Nicholas Bodor, Rodrigo T. Macedo, Kristen Harvey, Lisa A. Vanderveer, Daniel D. Krzizike, Martin J. Edelman, Joseph Treat, Margie L. Clapper. Impact of estrogen depletion using an aromatase inhibitor (AI) on EGFR-mutated non-small cell lung cancer (NSCLC) in a murine model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1797.

Inflammation as a chemoprevention target in asbestos-induced malignant mesothelioma

Malignant mesothelioma (MM) is an incurable cancer of the serosal lining that is often caused by exposure to asbestos. Therefore, novel agents for the prevention and treatment of this disease are urgently needed. Asbestos induces the release of pro-inflammatory cytokines such as IL-1β and IL-6, which play a role in MM development. IL-6 is a component of the JAK-STAT3 pathway that contributes to inflammation-associated tumorigenesis. Glycoprotein 130 (gp130), the signal transducer of this signaling axis, is an attractive drug target because of its role in promoting neoplasia via the activation of downstream STAT3 signaling. The anticancer drug, SC144, inhibits the interaction of gp130 with the IL-6 receptor (IL6R), effectively blunting signaling from this inflammatory axis. To test whether the inflammation-related release of IL-6 plays a role in the formation of MM, we evaluated the ability of SC144 to inhibit asbestos-induced carcinogenesis in a mouse model. The ability of sulindac and anakinra, an IL6R antagonist/positive control, to inhibit MM formation in this model was tested in parallel. Asbestos-exposed Nf2+/-;Cdkn2a+/- mice treated with SC144, sulindac or anakinra showed significantly prolonged survival compared to asbestos-exposed vehicle-treated mice. STAT3 activity was markedly decreased in MM specimens from SC144-treated mice. Furthermore, SC144 inhibited STAT3 activation by IL-6 in cultured normal mesothelial cells, and in vitro treatment of MM cells with SC144 markedly decreased the expression of STAT3 target genes. The emerging availability of newer, more potent SC144 analogs showing improved pharmacokinetic properties holds promise for future trials, benefitting individuals at high risk of this disease.

Dysregulation of miR-1-3p: An Early Event in Colitis-Associated Dysplasia

Detection of colorectal dysplasia during surveillance colonoscopy remains the best method of determining risk for colitis-associated colorectal cancer (CAC). miRNAs (miRs) show great promise as tissue-specific biomarkers of neoplasia. The goal of this study was to explore the miR expression profile of precancerous dysplastic lesions in the AOM/DSS mouse model and identify early molecular changes associated with CAC. Epithelial cells were laser-microdissected from the colonic mucosa (inflamed versus dysplastic) of mice with AOM/DSS-induced colitis. A miR signature that can distinguish inflamed non-neoplastic mucosa from dysplasia was identified. Bioinformatic analyses led to the discovery of associated miR gene targets and enriched pathways and supported the construction of a network interaction map. miR-1a-3p was one of the miRs with the highest number of predicted targets, including Cdk6. Interestingly, miR-1a-3p and Cdk6 were down- and up-regulated in dysplastic lesions, respectively. Transfection of HCT116 and RKO cells with miR-1a-3p mimics induced apoptosis and cell cycle arrest in G1, suggesting its biological function. A slight reduction in the level of CDK6 transcripts was also observed in cells transfected with miR-1. These data provide novel insight into the early molecular alterations that accompany the development of CAC and identify a miR signature that represents a promising biomarker for the early detection of colitis-associated dysplasia.

Real-world progression-free survival (rwPFS) and the impact of PD-L1 and smoking in driver-mutated non-small cell lung cancer (NSCLC) treated with immunotherapy

PURPOSE

Prior data suggest driver-mutated NSCLC, especially EGFR and ALK tumors, poorly respond to immunotherapy. However, little research using real-world cohorts have been performed, nor is it clear whether PD-L1 and smoking history are predictive of outcomes in such tumors. This study assessed rwPFS in a large cohort with driver-mutated advanced NSCLC treated with single-agent PD-1/PDL-1 inhibitors.

METHODS

Real-world data from 1746 patients were analyzed and rwPFS with immunotherapy was determined for EGFR, ALK, BRAF, and KRAS tumors. Kaplan-Meier curves characterized rwPFS and correlated with PD-L1 and smoking history. Comparisons were tested using log-rank.

RESULTS

Median rwPFS and the percent progression-free at 12 months were greater among KRAS (3.3 months, 21.1%) and BRAF (3.6 months, 20.6%) as compared to EGFR (2.5 months, 8.1%) and ALK tumors (2.3 months, 11.2%). KRAS tumors with PD-L1 ≥ 1% had longer rwPFS than PD-L1 < 1% tumors (4.1 versus 3.2 months, p = 0.001). PD-L1 positivity did not predict rwPFS in EGFR, ALK, or BRAF tumors. However, a smoking history was associated with longer rwPFS in EGFR (2.6 versus 2.3 months, p = 0.048) and ALK tumors (3.0 versus 2.1 months, p = 0.049) as compared to no smoking history.

CONCLUSION

Real-world PFS with immunotherapy was greater in KRAS and BRAF as compared to EGFR and ALK tumors. PD-L1 positivity was predictive in KRAS and not associated with rwPFS in other mutation types. While median rwPFS was short for EGFR and ALK tumors, small subsets were progression-free at 12 months. Better characterizing these subsets that benefit, along with developing strategies to overcome immunotherapy resistance in EGFR/ALK tumors are needed.

Abstract 2696: Catechol estrogen profiles of patients with EGFR- and ALK-positive non-small cell lung cancer (NSCLC)

Prior research from this group indicates that the human lung extensively metabolizes parent estrogens to reactive catechols. Estrone (E1) and estradiol (E2) are converted to the putative carcinogens, 4-hydroxyestrone (4-OHE1) and 4-hydroxyestradiol (4-OHE2), by cytochrome P450 1B1 (CYP1B1). In contrast, CYP1A1 metabolizes parent estrogens to 2-OHE1 and 2-OHE2, which may ultimately be converted to anti-proliferative derivatives. Our previous data strongly indicate that 4-OHEs contribute to lung tumorigenesis. However, their role in oncogene-driven NSCLC has not been investigated. The goal of this study was to compare the urinary profile of catechol estrogens in patients with EGFR- and ALK-positive NSCLC with those of cancer-free controls. The resulting levels of estrogen derivatives were correlated with genotypic variants in the estrogen metabolizing enzymes CYP1B1 and COMT. Patients with EGFR- and ALK-mutated NSCLC were recruited from the recently established Never-Smokers Lung Cancer Clinic at our institution. Study participants were 50 years of age or older to circumvent any confounding impact of pre-menopausal status on estrogen profiles. Mutation status was determined from tumor tissue biopsies. Cancer-free control subjects were Caucasian post-menopausal women with no prior smoking history. To date, 34 patients with tumors possessing EGFR mutations, 10 patients with ALK mutations, and 17 cancer-free control subjects have been enrolled. Urine specimens were collected from all participants and urinary estrogen species (E1, E2, E3, 4-OHE1, 4-OHE2, 2-OHE1, 2-OHE2, 16α-OHE1, 2-OME1, 4-OME1, OME2) were quantified using a newly established UPLC-MS/MS method. Blood lymphocytes, collected from NSCLC subjects, were genotyped for SNPs in CYP1B1 (L432V/rs1056836, R48G/rs10012, N453S/rs1800440) and COMT (V158M/rs4680) by real-time PCR. Preliminary investigation of the E1 metabolic pathway suggests a trend of higher ratios of 4-OHE1 to 2-OHE1 in patients with EGFR- and ALK-positive NSCLC as compared to cancer-free controls. Among NSCLC subjects, those possessing the high activity Leu432 variant of CYP1B1 (Leu/Leu + Leu/Val) tended to have higher ratios of 4-OHE1 to 2-OHE1 as compared to patients with the low activity Val/Val genotype. Early findings suggest enhanced production of C4 estrogen derivates may contribute to the development of oncogene-driven lung tumors. Targeting CYP1B1 may be of preventive and therapeutic interest. Recruitment of study participants is ongoing to validate these early findings in a larger cohort.

(Supported by an In Vino Vita Award from Fox Chase Cancer Center)

Citation Format: J. Nicholas Bodor, Joseph Treat, Daniel D. Krzizike, Carolyn L. Zawislak, Lisa Vanderveer, Sarah Eidbo, Eric A. Ross, Martin J. Edelman, Andrew J. Andrews, Margie L. Clapper. Catechol estrogen profiles of patients with EGFR- and ALK-positive non-small cell lung cancer (NSCLC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2696.

Abstract 4119: Genomic and immune characteristics of EGFR subtypes in non-small cell lung cancer (NSCLC)

Background: While most EGFR-mutant NSCLC tumors are resistant to checkpoint inhibitors, a small subset has durable responses. Certain molecular subtypes of EGFR may be more responsive. There is a lack of clarity on the genomic and immune profiles of EGFR subtypes, and further elucidation of this may assist in optimally identifying those likely to respond to immune-based therapies.

Methods: Profiles of 5,510 lung adenocarcinoma specimens were obtained utilizing next-generation sequencing of 592 genes (Caris Life Sciences) and categorized by EGFR subtype. PD-L1 expression (Ab: 22c3), tumor mutational burden (TMB), immune cell type fractions, and co-mutations in TP53 were assessed by EGFR subtype and compared to wild-type (WT) tumors.

Results: Of the total cohort, 791 (14.4%) were EGFR-mutant (Table). Among EGFR-mutant tumors, exon 19 deletions were most common (49.7%), followed by L858R, (32.9%), exon 20 insertions (13.0%), L861Q (2.9%), and G719X (1.5%). PD-L1 positivity of each EGFR subtype as compared to WT did not vary, except for L858R tumors which had a significantly lower percentage of PD-L1 positive cases. Exon 19 deletion, L858R, and exon 20 insertion tumors were significantly less likely to have high PD-L1 or high TMB compared to WT. Among the EGFR subtypes, L861Q and G719X tumors had the greatest percentage with high TMB. TP53 co-mutations were frequent in EGFR tumors, especially among L861Q and G719X tumors. Exon 19 deletion and L858R tumors had significantly less CD8+ and greater CD4+ T cell fractions compared to WT. Neutrophil and M2 macrophage cell fractions were significantly higher in exon 19 deletion, L858R, and exon 20 insertion tumors compared to WT.

Conclusions: Most subtypes of EGFR have profiles consistent with decreased immunogenicity; however L861Q and C719X tumors have a greater percentage with high TMB or TP53 co-mutations. Such features in uncommon EGFR subtypes may correlate with responsiveness to immune-based therapies and warrant further study.

Tumor Characteristic EGFR WT(n=4719) Exon 19 del(n=393) L858R(n=260) Exon 20 ins(n=103) L861Q(n=23) G719X(n=12) PD-L1 positive (≥1%) 57.7% 51.0% 49.0% a 49.5% 47.8% 50.0% PD-L1 high (≥50%) 30.6% 19.7% a 18.8% a 14.4% a 21.7% 16.7% TMB high (≥10 mut/Mb) 35.3% 1.0% a 3.7% a 1.0% a 9.5% 18.2% TP53 co-mutation 53.9% 61.7% 63.6% a 59.2% a 69.6% a 83.3% a Median % cell fraction CD8+ 0.7 0.3 a 0.4 a 0.3 0.6 0.2 CD4+ 0.0 0.6 a 0.8 a 1.3 a 1.7 1.1 Neutrophils 5.5 8.0 a 7.3 a 7.8 a 7.4 6.4 M2 macrophages 5.5 6.4a 6.9a 6.7a 5.8 4.3 aq-value &lt; 0.05 when compared to EGFR WT (corrected for multiple comparisons)

Citation Format: J. Nicholas Bodor, Joanne Xiu, Vinicius Ernani, Supreet Kaur, Hirva Mamdani, Pavel Brodskiy, Sai-Hong I. Ou, Patrick C. Ma, Margie L. Clapper, W. Michael Korn, Joseph Treat. Genomic and immune characteristics of EGFR subtypes in non-small cell lung cancer (NSCLC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 4119.

Abstract 2345: Specificity of catechol-O-methyltransferase (COMT) for hydroxyestrogens favors 2-OHEs over 4-OHEs

The contribution of estrogen receptor-mediated signaling to cancer progression and metastasis has been well documented. However, much less attention has been given to the role of estrogen metabolism in carcinogenesis. Parent estrogens are metabolized to 2- and 4-hydroxyestrogens (2-OHEs and 4-OHEs) that can retain their estrogenic activity, form reactive quinones that cause DNA damage, or become inactivated primarily by the rate-limiting conjugation enzyme catechol-O-methyltransferase (COMT). The ability of 4-OHEs to induce genomic instability and the malignant transformation of human breast epithelial cells has been reported. Glucuronidation or sulfation of methylated hydroxyestrogens, produced by COMT, increases their solubility and facilitates their excretion via urine or feces. The extent to which catechol estrogens are methylated dictates, in part, their ability to initiate carcinogenesis verses protect against tumor formation. COMT is a ubiquitous polymorphic enzyme that is expressed in humans in both peripheral tissues (soluble, s-COMT) and the central nervous system (membrane-bound). The goal of the present study was to compare the rate at which human wild type (WT) s-COMT and its major polymorphic variant (V108M s-COMT) transfer the methyl group from S-adenosylmethionine to 2-OHE and 4-OHE. This was accomplished by expressing COMT in E. coli, followed by protein purification and steady state Michaelis-Menten kinetics. Production of methylated hydroxyestrogens (2-MeOEs and 4-MeOEs) was quantified using LC-MS/MS methodology. The resulting data indicate that WT s-COMT methylates catechol estrogens more efficiently than V108M s-COMT. In addition, the specificity constant (kcat/KM) of WT s-COMT for methylation of 4-OHE2 was 12-fold greater than that of V108M s-COMT. The kcat/KM of V108M s-COMT was 4-fold greater for 2-OHE2 vs. 4-OHE2. Based on the enhanced catalytic efficiency of WT s-COMT in converting 2-OHEs to 2-MeOEs, 4-OHEs may have greater potential to cause DNA damage. Additional studies are needed to determine if the V108M s-COMT variant contributes to increased risk for cancer. These data provide novel insight into the potential mechanism by which 4-OHEs promote hormone-induced carcinogenesis.

This work was supported by an In Vino Vita Award from Fox Chase Cancer Center.

Citation Format: Daniel D. Krzizike, Margie L. Clapper, Andrew J. Andrews. Specificity of catechol-O-methyltransferase (COMT) for hydroxyestrogens favors 2-OHEs over 4-OHEs [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2345.

Abstract 1553: miR-1 targets Cdk6 and controls cell cycle progression and apoptosis in colitis-associated dysplasia

Detection of colorectal dysplasia during surveillance colonoscopy is currently the best method of determining risk of colitis-associated colorectal cancer (CAC). An understanding of the early molecular changes associated with the development of these lesions will inform the identification of new biomarkers for earlier detection. miRNAs (miRs), highly conserved noncoding RNAs, show great promise as stable, tissue-specific biomarkers of neoplasia. We previously identified 12 miRs that are differentially-expressed in colitis-associated dysplasias (flat and polypoid) vs. inflamed colonic mucosa from mice treated with AOM/DSS. miR-1, a putative tumor suppressor, was downregulated in colitis-associated dysplasias. Analysis of the mRNA expression profile of AOM/DSS-induced dysplasias and prediction of the interactions between the miRs and their targets led to the selection of the Cdk6 as the target of miR-1 to be further investigated, based on its: 1) upregulation in AOM/DSS-induced dysplasia; and 2) association with cell cycle progression and inflammatory signaling. The goal of the present study was to validate the predicted interaction between miR-1 and Cdk6 and assess the biological function of miR-1 in vitro. The ability of miR-1 to interact with the 3’UTR of Cdk6 mRNA was assessed using a dual luciferase assay. Co-transfection of HCT116 or RKO colon carcinoma cells with Cdk6-WT and miR-1 mimics led to a significant reduction in relative luciferase activity in both cell lines (30%, p=0.0117 and 47%, p=0.0269; respectively). Transfection with the Cdk6-Mut did not alter relative luciferase activity, confirming the Cdk6 binding site was specific for miR-1. The biological function of miR-1 was assessed in HCT116 and RKO cells reverse-transfected with miR-1 and cel-miR-67 (negative control) for 48 hrs. Apoptosis (AnnexinV+ cells) and cell cycle progression (% of cells in G0/G1, G2/M and S phase) were evaluated by flow cytometry, and proliferation by cell count (Trypan Blue). HCT116 and RKO transfected with the miR-1 mimic exhibited a higher proportion of apoptotic cells than the negative control (30% and 20% increase, p=0.0022 and 0.0013, respectively). Cell cycle analyses revealed the miR-1 mimic induced cell cycle arrest (G0/G1) in both cell lines (p&lt;0.05). In HCT116 cells, this was accompanied by a reduction in the percentage of cells in G2/M (p=0.002) and S (p&lt;0.001) phase. No effect of miR-1 on total cell number was observed. These results demonstrate that Cdk6 is a direct target of miR-1, and suggest that downregulation of this miR in dysplastic lesions contributes to CAC by inducing cell cycle progression and inhibiting apoptosis. These data provide novel insight into the early molecular changes that accompany the development of colitis-associated dysplasia and may serve as biomarkers for early detection of neoplasia. Supported by the Timothy P. and Aurora M. Hughes Fund for Colon Cancer Research.

Citation Format: Mariana F. Fragoso, Geysson J. Fernandez, Lisa Vanderveer, Harry S. Cooper, Michael Slifker, Margie L. Clapper. miR-1 targets Cdk6 and controls cell cycle progression and apoptosis in colitis-associated dysplasia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1553.

Suppression of Colon Tumorigenesis in Mutant Apc Mice by a Novel PDE10 Inhibitor that Reduces Oncogenic β-Catenin

Previous studies have reported that phosphodiesterase 10A (PDE10) is overexpressed in colon epithelium during early stages of colon tumorigenesis and essential for colon cancer cell growth. Here we describe a novel non-COX inhibitory derivative of the anti-inflammatory drug, sulindac, with selective PDE10 inhibitory activity, ADT 061. ADT 061 potently inhibited the growth of colon cancer cells expressing high levels of PDE10, but not normal colonocytes that do not express PDE10. The concentration range by which ADT 061 inhibited colon cancer cell growth was identical to concentrations that inhibit recombinant PDE10. ADT 061 inhibited PDE10 by a competitive mechanism and did not affect the activity of other PDE isozymes at concentrations that inhibit colon cancer cell growth. Treatment of colon cancer cells with ADT 061 activated cGMP/PKG signaling, induced phosphorylation of oncogenic β-catenin, inhibited Wnt-induced nuclear translocation of β-catenin, and suppressed TCF/LEF transcription at concentrations that inhibit cancer cell growth. Oral administration of ADT 061 resulted in high concentrations in the colon mucosa and significantly suppressed the formation of colon adenomas in the Apc^+/min-FCCC mouse model of colorectal cancer without discernable toxicity. These results support the development of ADT 061 for the treatment or prevention of adenomas in individuals at risk of developing colorectal cancer. PREVENTION RELEVANCE: PDE10 is overexpressed in colon tumors whereby inhibition activates cGMP/PKG signaling and suppresses Wnt/β-catenin transcription to selectively induce apoptosis of colon cancer cells. ADT 061 is a novel PDE10 inhibitor that shows promising cancer chemopreventive activity and tolerance in a mouse model of colon cancer.

High Variability in Cellular Proliferation, Gene Expression, and Cytokine Production in the Nonneoplastic Colonic Epithelium of Young Apc+/Min-FCCC Mice

An urgent need exists to identify efficacious therapeutic preventive interventions for individuals who are at high risk of developing colorectal cancer. To maximize the benefits of preventive intervention, it is vital to identify the time interval during which the initiation of a preventive intervention will lead to an optimal outcome. The goal of the present study was to determine if oncogenic events can be detected in the nonneoplastic colonic mucosa of Apc+/Min-FCCC mice prior to formation of the first adenoma, thus defining an earlier point of intervention along the cancer continuum. Tissues taken at three potential points of intervention were characterized: prior to Apc mutation (wild type Apc+/+-FCCC mice); after initiation but prior to colon adenoma formation (tumor-free Apc+/Min-FCCC mice); and after formation of the first colon adenoma (tumor-bearing Apc+/Min-FCCC mice). Experimentation focused on molecular processes that are dysregulated in early colon lesions: 1) cellular proliferation (proliferative index and size of the proliferative zone); 2) cellular stemness (expression of Ascl2, Grem1, Lgr5 and Muc2); 3) EGFR signaling (expression of Ereg); and 4) inflammation (expression of Mmp9, Ptsg2, and Reg4, as well as secretion of 18 cytokines involved in immune activation and response). Interestingly, the nonneoplastic colonic mucosa of wild type, tumor-free Apc+/Min-FCCC , and tumor-bearing Apc+/Min-FCCC mice did not display significant differences in average epithelial cell proliferation (fold change 0.8-1.3, p≥0.11), mucosal gene expression (fold change 0.8-1.4, p≥0.22), or secretion of specific cytokines from colonic mucosa (fold change 0.2-1.5, p≥0.06). However, the level of cytokine secretion was highly variable, with many (22% of wild type, 31% of tumor-free Apc+/Min-FCCC , and 31% of tumor-bearing Apc+/Min-FCCC ) mice categorized as outliers (> 1.5 x interquartile ranges below the first quartile or above the third quartile) due to elevated expression of at least one cytokine. In summary, no differences were observed in proliferation, stemness, and EGFR signaling in the colonic mucosa of wild type vs Apc+/Min-FCCC mice, with low baseline cytokine expression, prior to the formation of the first colon adenoma. The results of this study provide valuable baseline data to inform the design of future cancer prevention studies.

Abstract 2374: Identification of altered miRNA-gene interactions in AOM/DSS induced colitis-associated dysplasia

Although significant progress has been made in delineating the pathways that contribute to ulcerative colitis (UC)-associated tumorigenesis, the early molecular alterations that fuel disease progression remain poorly understood. microRNAs (miRs) have emerged as important modulators of inflammatory pathways and their aberrant expression has been associated with initiation and progression of malignancy. The goal of this study is to identify gene-miR interactions that occur early in experimental UC and contribute to the development of colitis-associated dysplasia. The mRNA and miR expression profile of laser microdissected colon specimens (inflamed mucosa vs. dysplasia) from Swiss Webster mice with AOM/DSS-induced colitis was interrogated using the Mouse Gene Expression Microarrays 4x44K v2 (Agilent®) and miRNA Mouse platform (NanoString®). Data were analyzed using R/Bioconductor and nSolverTM (NanoString®). Differentially expressed miRs (n=12, p&lt;0.001) were validated by RT-qPCR (n=9) and used for target prediction (TargetScan v. 7.2). The differential expression of the predicted target genes (mRNA array) vs. miRs was compared and filtered to include only those with contrasting changes in expression (e.g. downregulated miR and upregulated mRNA). The resulting list of 98 genes was subjected to pathway enrichment analysis using EnrichR. Network interactions were calculated using STRING and visualized on Cytoscape v.3.8.0. Gene ontology analyses revealed 23 terms associated with the pathogenesis and progression of UC, including TNFα signaling via NF-kB, G1 to S cell cycle control, Wnt and Hedgehog signaling. Analyses of miR targets revealed that miR-30c, miR-145a and miR-1a controlled the largest number of predicted target genes (35%, 26% and 18%, respectively). These data suggest an important role of these top miRs (putative tumor suppressors) in UC-associated tumorigenesis, based on their downregulation in dysplasias and corresponding upregulation of their oncogenic targets (Sox9, Ccnd2 and Cdk6). Consistent with our findings, Sox9 contributes to carcinogenesis through its effect on stem cells. The Ccnd2/Cdk6 complex is considered a central component of signaling pathways that regulate cell cycle G1/S transition during neoplastic development. Therefore, early interaction of these miRs with their respective target genes may contribute to the transition of inflamed colonic mucosa to dysplasia in mice with experimental colitis. Additional in vitro validation of the predicted interactions remains in progress. (Supported by a generous donation from Aurora and Timothy Hughes).

Citation Format: Mariana F. Fragoso, Geysson J. Fernandez, Lisa Vanderveer, Harry S. Cooper, Wen-Chi Chang, Michael Slifker, Karthik Devarajan, Yan Zhou, Eric Ross, Margie L. Clapper. Identification of altered miRNA-gene interactions in AOM/DSS induced colitis-associated dysplasia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2374.

Meeting Report: Translational Advances in Cancer Prevention Agent Development Meeting

The Division of Cancer Prevention of the National Cancer Institute (NCI) and the Office of Disease Prevention of the National Institutes of Health co-sponsored the Translational Advances in Cancer Prevention Agent Development Meeting on August 27 to 28, 2020. The goals of this meeting were to foster the exchange of ideas and stimulate new collaborative interactions among leading cancer prevention researchers from basic and clinical research; highlight new and emerging trends in immunoprevention and chemoprevention as well as new information from clinical trials; and provide information to the extramural research community on the significant resources available from the NCI to promote prevention agent development and rapid translation to clinical trials. The meeting included two plenary talks and five sessions covering the range from pre-clinical studies with chemo/immunopreventive agents to ongoing cancer prevention clinical trials. In addition, two NCI informational sessions describing contract resources for the preclinical agent development and cooperative grants for the Cancer Prevention Clinical Trials Network were also presented.

Dysplastic Aberrant Crypt Foci: Biomarkers of Early Colorectal Neoplasia and Response to Preventive Intervention

The discovery of aberrant crypt foci (ACF) more than three decades ago not only enhanced our understanding of how colorectal tumors form, but provided new opportunities to detect lesions prior to adenoma development and intervene in the colorectal carcinogenesis process even earlier. Because not all ACF progress to neoplasia, it is important to stratify these lesions based on the presence of dysplasia and establish early detection methods and interventions that specifically target dysplastic ACF (microadenomas). Significant progress has been made in characterizing the morphology and genetics of dysplastic ACF in both preclinical models and humans. Image-based methods have been established and new techniques that utilize bioactivatable probes and capture histologic abnormalities in vivo are emerging for lesion detection. Successful identification of agents that target dysplastic ACF holds great promise for intervening even earlier in the carcinogenesis process to maximize tumor inhibition. Future preclinical and clinical prevention studies should give significant attention to assessing the utility of dysplastic ACF as the earliest identifiable biomarker of colorectal neoplasia and response to therapy.See all articles in this Special Collection Honoring Paul F. Engstrom, MD, Champion of Cancer Prevention.

Novel Protein-Based Vaccine against Self-Antigen Reduces the Formation of Sporadic Colon Adenomas in Mice

Simple Summary

Colorectal cancer remains a leading cause of cancer-related mortality worldwide. However, high-risk populations with a genetic predisposition for colorectal cancer could benefit greatly from novel and efficacious immunopreventive strategies that afford long-lasting protection. The achaete-scute family bHLH transcription factor 2 (Ascl2) has been identified as a promising target for immunoprevention of colorectal cancer, based on its induction during the formation and progression of colorectal tumors and its minimal expression observed in healthy tissue. The goal of the present study was to determine the efficacy of a protein-based vaccine targeting Ascl2 in combination with an anti-PD-1 treatment in a spontaneous colorectal cancer mouse model. This novel vaccine strategy promotes potent tumor-specific immunity, and prevents the formation of colon adenomas in mice. The results demonstrate that Ascl2 is a promising target for immunoprevention for individuals at elevated risk of developing colorectal cancer.

Abstract

Novel immunopreventive strategies are emerging that show great promise for conferring long-term protection to individuals at high risk of developing colorectal cancer. The KISIMA vaccine platform utilizes a chimeric protein comprising: (1) a selected tumor antigen; (2) a cell-penetrating peptide to improve antigen delivery and epitope presentation, and (3) a TLR2/4 agonist to serve as a self-adjuvant. This study examines the ability of a KISIMA vaccine against achaete-scute family bHLH transcription factor 2 (Ascl2), an early colon cancer antigen, to reduce colon tumor formation by stimulating an anti-tumor immune response. Vaccine administrations were well-tolerated and led to circulating antibodies and antigen-specific T cells in a mouse model of colorectal cancer. To assess preventive efficacy, the vaccine was administered to mice either alone or in combination with the immune checkpoint inhibitor anti-PD-1. When delivered to animals prior to colon tumor formation, the combination strategy significantly reduced the development of colon microadenomas and adenomas, as compared to vehicle-treated controls. This response was accompanied by an increase in the intraepithelial density of CD3+ T lymphocytes. Together, these data indicate that the KISIMA-Ascl2 vaccine shows great potential to be a safe and potent immunopreventive intervention for individuals at high risk of developing colorectal cancer.

Honoring Paul F. Engstrom, MD: A Pioneer of Cancer Prevention

See all articles in this Special Collection Honoring Paul F. Engstrom, MD, Champion of Cancer Prevention

Gut Microbiota Influences Experimental Outcomes in Mouse Models of Colorectal Cancer

Colorectal cancer (CRC) is a leading cause of cancer-related deaths worldwide. Mouse models are a valuable resource for use throughout the development and testing of new therapeutic strategies for CRC. Tumorigenesis and response to therapy in humans and mouse models alike are influenced by the microbial communities that colonize the gut. Differences in the composition of the gut microbiota can confound experimental findings and reduce the replicability and translatability of the resulting data. Despite this, the contribution of resident microbiota to preclinical tumor models is often underappreciated. This review does the following: (1) summarizes evidence that the gut microbiota influence CRC disease phenotypes; (2) outlines factors that can influence the composition of the gut microbiota; and (3) provides strategies that can be incorporated into the experimental design, to account for the influence of the microbiota on intestinal phenotypes in mouse models of CRC. Through careful experimental design and documentation, mouse models can continue to rapidly advance efforts to prevent and treat colon cancer.

Abstract 3864: A novel PDE10/β-catenin pathway inhibitor, MCI-030, for the treatment of colorectal cancer

Over 90% of colorectal cancers harbor mutations in β-catenin or pathway components (e.g. APC) that stabilize β-catenin, causing nuclear translocation and constitutive Tcf-mediated transcription of genes encoding proteins essential for the proliferation and survival of tumor cells. We recently reported that the cyclic nucleotide degrading phosphodiesterase (PDE) isozyme PDE10 is overexpressed in colorectal cancers relative to normal tissue. Its expression and enzymatic activity are essential for colon tumor cell growth, as evidenced by knockdown of PDE10 expression using siRNA or inhibition of enzyme activity using known inhibitors such as PF-2545920. PDE10 inhibition in tumor cells expressing high levels of PDE10 causes increased intracellular cGMP levels to activate PKG and phosphorylate β-catenin, which induces ubiquitination and proteasomal degradation to suppress nuclear translocation and Tcf transcriptional activity. Conversely, ectopic expression of PDE10 in normal colonocytes or precancerous adenoma cells causes increased levels of β-catenin and the expression of proteins (e.g. cyclin D and survivin) essential for the proliferation and survival of tumor cells. To identify novel antitumor PDE10 inhibitors, we screened a chemically diverse library of indenes for PDE10 and tumor cell growth inhibitory activity. Following extensive chemical optimization, MCI-030 emerged as a potent and selective inhibitor of tumor cell growth. Similar to PF-2545920, but with appreciably greater potency and tumor cell selectivity, MCI-030 inhibited colon tumor cell growth by activating cGMP/PKG signaling to phosphorylate and induce β-catenin degradation. MCI-030 also inhibited colon tumor cell spheroid formation and reduced spheroid size and growth at concentrations that inhibit PDE10. Oral administration of MCI-030 significantly inhibited colon tumor formation in the Apc+/min-FCCC mouse model without discernable toxicity. Importantly, unlike PDE10 inhibitors developed to cross the blood-brain barrier for the treatment of CNS disorders, MCI-030 lacks the sedation side effects. Together, these findings support preclinical development of MCI-030 for the treatment of colorectal cancer as a novel PDE10 inhibitor capable of selectively inhibiting the growth of tumors harboring β-catenin or APC mutations. Funding provided by NCI grants R01CA131378, R01CA148817, R01CA197147, and R01CA155638.

Citation Format: Antonio B. Ward, Xi Chen, Jacob Valiyaveettil, Kevin Lee, Wen-Chi L. Chang, Yulia Maxuitenko, Veronica Ramirez-Alcantara, Kristy Berry, Luciana Madeira da Silva, Bing Zhu, Tyler Mattox, Michael R. Boyd, Adam B. Keeton, Margie L. Clapper, Harry S. Cooper, Gary A. Piazza. A novel PDE10/β-catenin pathway inhibitor, MCI-030, for the treatment of colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3864.

Self-antigen MASH2 combined with the AS15 immunostimulant induces tumor protection in colorectal cancer mouse models

Human achaete scute homolog 2 (HASH2) and its murine ortholog MASH2 are potential targets for colorectal cancer immunotherapy. We assessed immunogenicity and antitumor potential of recombinant MASH2 protein combined with AS15 immunostimulant (recMASH2+AS15) in CB6F1 and Apc^+/Min-FCCC mice. CB6F1 mice received 4 injections of recMASH2+AS15 or AS15 alone before challenge with TC1-MASH2 tumor cells (Tumor Challenge). Apc^+/Min-FCCC mice received 9 injections of recMASH2+AS15 or vehicle (phosphate buffer saline [PBS] or AS15 alone), before (two independent Prophylactic Studies) or after (Immunotherapy) colon adenomas were detectable by colonoscopy. CB6F1 mice immunized with recMASH2+AS15 had a significantly smaller mean tumor size and improved survival rate compared to controls (104 mm² vs. 197 mm² [p = 0.009] and 67% vs. 7% [p = 0.001], respectively). In Prophylactic Study 1, the mean number of colon adenomas was significantly lower in Apc^+/Min-FCCC mice receiving recMASH2+AS15 compared to PBS (1.8 [95% confidence interval 1.0–3.3] vs. 5.2 [3.7–7.4], p = 0.003). Fewer microadenomas were observed in recMASH2+AS15 groups compared to PBS in both Prophylactic Studies (Study 1: mean 0.4 [0.2–1.0] vs. 1.5 [0.9–2.4], p = 0.009; Study 2: 0.4 [0.2–0.6] vs. 1.1 [0.8–1.5], p = 0.001). In the Immunotherapy Study, fewer colon adenomas tended to be observed in recMASH2+AS15-treated mice (4.1 [2.9–6.0]) compared to controls (AS15 4.7 [3.3–6.6]; PBS 4.9 [3.5–6.9]; no significant difference). recMASH2+AS15 induced MASH2-specific antibody and CD4+ responses in both mouse models. recMASH2+AS15 partially protected mice against MASH2-expressing tumors and reduced spontaneous colorectal adenomas in Apc^+/Min-FCCC mice, indicating that MASH2/HASH2 antigens are targets for colorectal cancer immunotherapy.

Differential preventive activity of sulindac and atorvastatin in Apc+/Min-FCCCmice with or without colorectal adenomas

OBJECTIVE

The response of subjects to preventive intervention is heterogeneous. The goal of this study was to determine if the efficacy of a chemopreventive agent differs in non-tumour-bearing animals versus those with colorectal tumours. Sulindac and/or atorvastatin was administered to Apc^+/Min-FCCC mice with known tumour-bearing status at treatment initiation.

DESIGN

Male mice (6-8 weeks old) underwent colonoscopy and received control chow or chow with sulindac (300 ppm), atorvastatin (100 ppm) or sulindac/atorvastatin. Tissues were collected from mice treated for 14 weeks (histopathology) or 7 days (gene expression). Cell cycle analyses were performed on SW480 colon carcinoma cells treated with sulindac, atorvastatin or both.

RESULTS

The multiplicity of colorectal adenomas in untreated mice bearing tumours at baseline was 3.6-fold higher than that of mice that were tumour free at baseline (P=0.002). Atorvastatin completely inhibited the formation of microadenomas in mice that were tumour free at baseline (P=0.018) and altered the expression of genes associated with stem/progenitor cells. Treatment of tumour-bearing mice with sulindac/atorvastatin led to a 43% reduction in the multiplicity of colorectal adenomas versus untreated tumour-bearing mice (P=0.049). Sulindac/atorvastatin increased the expression of Hoxb13 and Rprm significantly, suggesting the importance of cell cycle regulation in tumour inhibition. Treatment of SW480 cells with sulindac/atorvastatin led to cell cycle arrest (G0/G1).

CONCLUSIONS

The tumour status of animals at treatment initiation dictates response to therapeutic intervention. Atorvastatin eliminated microadenomas in tumour-free mice. The tumour inhibition observed with Sul/Atorva in tumour-bearing mice was greater than that achieved with each agent.

Abstract 5045: Inflammation is upregulated in the normal colonic epithelium and stroma of Apc+/Min-FCCCmice with colon tumors

The Apc+/Min-FCCC mouse harbors a point mutation in the Apc tumor suppressor gene and is highly susceptible to the development of multiple colon tumors. Despite being maintained for many years as an inbred colony, Apc+/Min-FCCC mice are heterogeneous with respect to the time to colon tumor development and the number of colon tumors that ultimately form. This model therefore serves as a powerful tool with which to better understand the earliest events that lead to tumorigenesis. Identification of early alterations in these animals may provide targets for effective, long-term tumor prevention. The goal of this study was to characterize early changes in gene expression in the nonneoplastic colonic epithelium and stroma that may contribute to tumor formation in Apc +/Min-FCCC mice. Animals were defined as ‘tumor-bearing' if they harbored at least one gross colon tumor at necropsy. No lesions were detected at necropsy in the remaining animals (‘tumor-free'). Normal tissue was collected for analysis from the distal colon at least 1 cm away from the nearest tumor. Histologically-normal epithelial and stromal cells were microdissected from frozen tissue sections. Gene expression profiling was performed using the Agilent Mouse 4x44K microarray chip. Differentially expressed genes were selected using an FDR of 10% and a ≥ 2-fold change in gene expression. Gene set enrichment analyses confirmed the enrichment of stromal genes in samples of isolated stroma (p&lt; 0.05). Numerous genes were differentially expressed in tumor-free vs. tumor-bearing ApcMin/+ mice, in both the epithelial and stromal compartments. Gene Ontology enrichment analyses revealed the associated biological processes that were dysregulated, including inflammation, immune cell migration, and response to bacterium (FDR&lt;0.1%). These findings indicate that inflammatory processes are altered in the nonneoplastic colon well in advance of tumor formation and represent promising targets for preventive intervention.

Citation Format: Alyssa A. Leystra, Lisa Vanderveer, Yan Zhou, Harry S. Cooper, Sergei Grivennikov, Margie L. Clapper. Inflammation is upregulated in the normal colonic epithelium and stroma of Apc+/Min-FCCCmice with colon tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5045.

On meta- and mega-analyses for gene-environment interactions

Gene-by-environment (G × E) interactions are important in explaining the missing heritability and understanding the causation of complex diseases, but a single, moderately sized study often has limited statistical power to detect such interactions. With the increasing need for integrating data and reporting results from multiple collaborative studies or sites, debate over choice between mega- versus meta-analysis continues. In principle, data from different sites can be integrated at the individual level into a "mega" data set, which can be fit by a joint "mega-analysis." Alternatively, analyses can be done at each site, and results across sites can be combined through a "meta-analysis" procedure without integrating individual level data across sites. Although mega-analysis has been advocated in several recent initiatives, meta-analysis has the advantages of simplicity and feasibility, and has recently led to several important findings in identifying main genetic effects. In this paper, we conducted empirical and simulation studies, using data from a G × E study of lung cancer, to compare the mega- and meta-analyses in four commonly used G × E analyses under the scenario that the number of studies is small and sample sizes of individual studies are relatively large. We compared the two data integration approaches in the context of fixed effect models and random effects models separately. Our investigations provide valuable insights in understanding the differences between mega- and meta-analyses in practice of combining small number of studies in identifying G × E interactions.

Estrogen metabolism in the human lung: impact of tumorigenesis, smoke, sex and race/ethnicity

Previous data from this group demonstrate that the murine lung metabolizes estrogen. Production of the putative carcinogen 4-hydroxyestrogen (4-OHE) is elevated within the lungs of female vs. male mice and accelerated by tobacco smoke. The goal of this study was to determine if the human lung metabolizes estrogen and evaluate the impact of tumor formation, smoke, sex and race/ethnicity on metabolism. Urine and lung tissue (normal, tumor) were obtained from 49 non-small cell lung cancer patients. Healthy postmenopausal Caucasian (n = 19) and Chinese (n = 20) American women (never-smokers) donated urine. Quantitative RT-PCR analyses indicate that multiple estrogen synthesis and metabolism genes are expressed in human bronchoalveolar cells. Estrogen and its metabolites were measured in lung tissue and urine using liquid chromatography/tandem mass spectrometry. Wilcoxon rank tests were used for statistical comparisons. E₁, E₂, E₃ and estrogen metabolites 2-OHE₁, 2-OHE₂, 4-OHE₁, 4-OHE₂, 2-OME₁ and 2-OME₂ were detected at higher levels in tumor vs. adjacent normal tissue and in women vs. men (P < 0.05). The proportion of 4-OHEs was higher in tumors than in normal lung tissue (P < 0.05), and elevated in normal tissue from current- vs. never-smoking women (P = 0.006); similar trends were observed in urine. The proportion of 4-OHEs in the urine of postmenopausal Chinese American women was 1.8-fold higher than that of Caucasian women (P = 0.015). These data indicate that estrogen metabolites are present in the human lung. A shift towards 4-hydroxylation during lung tumorigenesis may contribute to the risk conferred by smoking, sex or race/ethnicity.

Haploinsufficiency in tumor predisposition syndromes: altered genomic transcription in morphologically normal cells heterozygous for VHL or TSC mutation

Tumor suppressor genes and their effector pathways have been identified for many dominantly heritable cancers, enabling efforts to intervene early in the course of disease. Our approach on the subject of early intervention was to investigate gene expression patterns of morphologically normal one-hit cells before they become hemizygous or homozygous for the inherited mutant gene which is usually required for tumor formation. Here, we studied histologically non-transformed renal epithelial cells from patients with inherited disorders that predispose to renal tumors, including von Hippel-Lindau (VHL) disease and Tuberous Sclerosis (TSC). As controls, we studied histologically normal cells from non-cancerous renal epithelium of patients with sporadic clear cell renal cell carcinoma (ccRCC). Gene expression analyses of VHLmut/wt or TSC1/2mut/wt versus wild-type (WT) cells revealed transcriptomic alterations previously implicated in the transition to precancerous renal lesions. For example, the gene expression changes in VHLmut/wt cells were consistent with activation of the hypoxia response, associated, in part, with the Warburg effect. Knockdown of any remaining VHL mRNA using shRNA induced secondary expression changes, such as activation of NF?B and interferon pathways, that are fundamentally important in the development of RCC. We posit that this is a general pattern of hereditary cancer predisposition, wherein haploinsufficiency for VHL or TSC1/2, or potentially other tumor susceptibility genes, is sufficient to promote development of early lesions, while cancer results from inactivation of the remaining normal allele. The gene expression changes identified here are related to the metabolic basis of renal cancer and may constitute suitable targets for early intervention.

Lack of chemopreventive efficacy of metformin in rodent models of urinary bladder, head and neck, and colon/intestine cancer

Metformin is a biguanide employed in treating type II diabetes. Its potential efficacy for treating cancer has been demonstrated epidemiologically (lower cancer incidence in metformin users compared with users of sulfonylureas or insulin) and mechanistically, primarily in cell culture. Metformin decreases the levels of insulin-like growth factor 1 and secondarily inhibits the mammalian target of rapamycin pathway to exhibit anticancer effects. The current study examined its cancer preventive efficacy in multiple standard in situ arising cancer models. Metformin was administered orally by gavage or in the diet, at human equivalent doses, in numerous cancer models. In the hydroxybutyl(butyl)nitrosamine-induced model of invasive urinary bladder cancer, metformin (50 or 150 mg/kg body weight/day, intragastric) was ineffective despite high urinary concentrations of metformin. Metformin (250 or 500 ppm in diet) failed to decrease the incidence or invasiveness of squamous cell cancer of the tongue in a 4-nitroquinoline-1-(4NQO)-induced model. Finally, in the Min mouse model of gastrointestinal cancer, metformin (400 or 1,200 ppm in diet) was ineffective. Notably, a slight increase in intestinal tumor multiplicity was observed at the higher dose. Therefore, metformin lacked efficacy in multiple standard cancer models in non-diabetic rodents. This lack of efficacy may discourage any large phase clinical cancer trials in non-diabetic individuals in the absence of clear phase-II studies.

Plecanatide-mediated activation of guanylate cyclase-C suppresses inflammation-induced colorectal carcinogenesis in Apc+/Min-FCCC mice

AIM

To evaluate the effect of orally administered plecanatide on colorectal dysplasia in Apc^+/Min-FCCC mice with dextran sodium sulfate (DSS)-induced inflammation.

METHODS

Inflammation driven colorectal carcinogenesis was induced in Apc^+/Min-FCCC mice by administering DSS in their drinking water. Mice were fed a diet supplemented with plecanatide (0-20 ppm) and its effect on the multiplicity of histopathologically confirmed polypoid, flat and indeterminate dysplasia was evaluated. Plecanatide-mediated activation of guanylate cyclase-C (GC-C) signaling was assessed in colon tissues by measuring cyclic guanosine monophosphate (cGMP) by ELISA, protein kinase G-II and vasodilator stimulated phosphoprotein by immunoblotting. Ki-67, c-myc and cyclin D1 were used as markers of proliferation. Cellular levels and localization of β-catenin in colon tissues were assessed by immunoblotting and immunohistochemistry, respectively. Uroguanylin (UG) and GC-C transcript levels were measured by quantitative reverse transcription polymerase chain reaction (RT-PCR). A mouse cytokine array panel was used to detect cytokines in the supernatant of colon explant cultures.

RESULTS

Oral treatment of Apc^+/MinFCCC mice with plecanatide produced a statistically significant reduction in the formation of inflammation-driven polypoid, flat and indeterminate dysplasias. This anti-carcinogenic activity of plecanatide was accompanied by activation of cGMP/GC-C signaling mediated inhibition of Wnt/β-catenin signaling and reduced proliferation. Plecanatide also decreased secretion of pro-inflammatory cytokines (IL-6, IL1 TNF), chemokines (MIP-1, IP-10) and growth factors (GCSF and GMCSF) from colon explants derived from mice with acute DSS-induced inflammation. The effect of plecanatide-mediated inhibition of inflammation/dysplasia on endogenous expression of UG and GC-C transcripts was measured in intestinal tissues. Although GC-C expression was not altered appreciably, a statistically significant increase in the level of UG transcripts was detected in the proximal small intestine and colon, potentially due to a reduction in intestinal inflammation and/or neoplasia. Taken together, these results suggest that reductions in endogenous UG, accompanied by dysregulation in GC-C signaling, may be an early event in inflammation-promoted colorectal neoplasia; an event that can potentially be ameliorated by prophylactic intervention with plecanatide.

CONCLUSION

This study provides the first evidence that orally administered plecanatide reduces the multiplicity of inflammation-driven colonic dysplasia in mice, demonstrating the utility for developing GC-C agonists as chemopreventive agents.

Abstract A25: Inhibition or delay of microadenoma development by atorvastatin, naproxen and ED-71 in mice genetically predisposed to colorectal adenomas

Previous studies by this group demonstrate the ability of chemopreventive agents to differentially inhibit morphological subtypes (flat and polypoid) of colorectal adenomas. Recent efforts have focused on the response of microadenomas, a lesion not routinely evaluated by others, to therapeutic intervention. Microadenomas, or dysplastic aberrant crypt foci (ACFs), are direct precursors of colorectal adenomas and represent the earliest microscopic aberration that can be detected prior to colon tumor formation. The goal of the present study was to: 1) characterize the incidence and multiplicity of microadenomas (≤4 crypts) in Apc+/Min-FCCC mice that spontaneously develop multiple colorectal adenomas, and 2) compare the effect of three classes of chemopreventive agents on microadenoma formation. Animals for baseline histological characterization were subjected to colonoscopic examinations at 7 weeks of age (standard time of treatment initiation) and categorized as tumor-free or tumor-bearing. Forty five percent of the Apc+/Min-FCCC mice without gross colon tumors (N=11) possessed microadenomas at baseline, with an overall average of 0.63 ± 0.29 (Mean ± SEM) per mouse. Among mice with gross tumors at baseline (N=10), 30% had microadenomas (0.3 ± 0.16). Results from treatment studies demonstrate that several agents have the ability to modulate microadenoma formation or progression when administered chronically for 14 weeks. First, atorvastatin (100 ppm), a cholesterol-lowering agent, completely eliminated the formation of microadenomas in mice that were free of gross tumors at baseline (as compared to controls, P = 0.007). In addition, a 33% reduction in tumor incidence was observed among atorvastatin-treated animals at 14 weeks as compared to controls (atorvastatin vs. controls: 55.6% vs. 88.5%, P = 0.017). Second, administration of the non-steroidal anti-inflammatory drug naproxen (400 ppm) caused a significant reduction (89.3%) in the multiplicity of microadenomas as compared to that of animals receiving unsupplemented control diet (0.06 ± 0.06 vs. 0.56 ± 0.24, respectively). Inhibition of microadenomas by naproxen translated into a significant reduction in tumor incidence, (naproxen - 64.7%, controls - 100%, P = 0.0076). Third, ED-71 (eldecalcitol; 1α,25-dihydroxy-2β;-(3-hydroxypropyloxy) Vitamin D3), a novel analog of calcitriol, at a dose of 0.1 μg/kg bw, unexpectedly increased the multiplicity of microadenomas in drug-treated mice as compared to controls (0.9 ± 0.22 vs. 0.5 ± 0.25 P = 0.06, respectively). In contrast, ED-71 reduced the mean incidence of adenomas (&gt; 4 crypts) by 47% (ED-71 - 45.5%, controls 92.3%; P = 0.02) and adenoma multiplicity by 47.6% (ED-71 - 1.1 ± 0.39, controls - 2.1 ± 0.72; P &gt; 0.05) in mice that were free of gross tumors at baseline. These data suggest that ED-71 is effective in preventing the progression of microadenomas to adenomas. In summary, these findings demonstrate the importance of evaluating the response of microadenomas to therapy and suggest that microadenomas represent a promising target for chemopreventive intervention.

Supported by CA129467, N01CN43309 and HHSN2610005. * Equal contribution to the abstract.

Citation Format: Wen-Chi L. Chang, Harry S. Cooper, Harvey Hensley, Tianyu Li, Karthik Devarajan, Margie L. Clapper. Inhibition or delay of microadenoma development by atorvastatin, naproxen and ED-71 in mice genetically predisposed to colorectal adenomas. [abstract]. In: Proceedings of the AACR Special Conference on Colorectal Cancer: From Initiation to Outcomes; 2016 Sep 17-20; Tampa, FL. Philadelphia (PA): AACR; Cancer Res 2017;77(3 Suppl):Abstract nr A25.

Abstract B21: PDE10A overexpression in colon cancer cells and tumors relative to normal colonocytes and colon mucosa

Phosphodiesterase 10A (PDE10A) is a cGMP and cAMP degrading PDE isozyme expressed in areas of the brain controlling motor function and cognition. PDE10A has been strongly linked to diseases such as schizophrenia and Huntington's disease, for which PDE10A inhibitors are currently in clinical trials and appear to be well tolerated. Although, PDE10A has limited expression and no known function in peripheral tissues, high levels were measured in colon tumor cells in vitro and in vivo compared with cells derived from normal colon and colonic mucosa (Li et al., Oncogene 2015). PDE10A inhibition by small molecules or genetic silencing attenuated colon tumor cell growth by a mechanism involving cGMP/PKG activation, the suppression of oncogenic β-catenin, and a decrease in TCF transcriptional activity (Li et al., Oncogene 2015). These observations suggest that PDE10A may play an unrecognized role in tumorigenesis and provide a novel therapeutic target for colorectal cancer chemoprevention or therapy. The human colon tumor cell lines, HCT116, HT29, Caco2, and SW480, show elevated expression of PDE10A as compared to the normal colon mucosal epithelial cell line, NCM460, and are more sensitive to PDE10 inhibitors relative to NCM460 cells. Subcutaneous tumors established from HT29 colon tumor cells in athymic mice expressed elevated levels of PDE10A as compared to normal mouse colon tissue. Colon tumors collected from heterozygous APCmin/+FCCC mice displayed an elevation in PDE10A levels as compared to uninvolved mucosa from the APCmin/+FCCC mice and wild type colon mucosa. Overexpression of PDE10A mRNA and protein levels was also observed in colon adenocarcinomas relative to uninvolved colon mucosa in specimens obtained from colorectal cancer patients. These observations, along with recent findings that a novel sulindac derivative (ADT-061) with PDE10A inhibitory activity suppresses tumor formation in the APCmin/+FCCC mouse model of colon cancer without apparent toxicity, suggests that PDE10A provides a novel therapeutic target for cancer cell specific inhibition of tumor growth.

Citation Format: Ashley S. Lindsey, Kevin Lee, Joel Andrews, Wen-Chi L. Chang, Veronica Ramirez-Alcantara, Marcus Tan, William Grizzle, Margie L. Clapper, Gary Piazza. PDE10A overexpression in colon cancer cells and tumors relative to normal colonocytes and colon mucosa. [abstract]. In: Proceedings of the AACR Special Conference on Colorectal Cancer: From Initiation to Outcomes; 2016 Sep 17-20; Tampa, FL. Philadelphia (PA): AACR; Cancer Res 2017;77(3 Suppl):Abstract nr B21.

Abstract A30: Novel non-COX inhibitory sulindac derivative with PDE10 inhibitory activity reduces incidence and multiplicity of colorectal adenomas in the APC+/min-FCCC mouse model

Sulindac has been reported to reduce the number and size of precancerous colonic adenomas in patients with familial adenomatous polyposis (FAP), but is not recommended for long-term use as a cancer chemopreventive drug because of potentially fatal toxicities associated with cyclooxygenase (COX) inhibition. We report here a novel sulindac derivative, ADT-061, that lacks COX-1 and COX-2 inhibitory activity, yet potently and selectively inhibits colon tumor cells with IC50 values of 0.3-0.5 μM with no significant effect on the growth of normal colonocytes. By comparison, sulindac sulfide inhibits colon tumor cell growth with IC50 values of 40-60 μM, and has only modest tumor cell selectivity. ADT-061 inhibits phosphodiesterase 10A (PDE10), which increases intracellular cGMP levels, thus activates protein kinase G, suppresses nuclear levels of β-catenin, and induces cell cycle arrest and apoptosis, all within the same concentration range that inhibits tumor cell growth. ADT-061was evaluated for chemopreventive activity in the APC+/min-FCCC mouse model of colon cancer, which harbors colorectal adenomas that express PDE10. Colonoscopy exams were initially performed on all mice to ensure the absence of colorectal adenomas prior to treatment. At 7-8 weeks of age, male mice were treated with ADT-061 (1000ppm and 1500ppm) in the diet for 14 weeks. ADT-061 reduced the incidence of colorectal adenomas from 95.8% in the control group to 73.9% in the 1000ppm group (p=0.048), and 59.1% (p=0.004) in the 1500ppm group. Control untreated mice had an average of 2.98 colorectal adenomas per mouse, while mice treated with 1000ppm and 1500ppm ADT-061 had an average of 2.04 (p=0.102) and 1.91 (p=0.039) adenomas per mouse, respectively. These observations suggest that ADT-061, or analogs thereof, merit further drug development efforts for colorectal cancer chemoprevention.

Citation Format: Kevin J. Lee, Xi Chen, Jacob Valiyaveettil, Ashley S. Lindsey, Joel Andrews, Veronica Ramirez-Alcantara, Adam B. Keeton, Gary A. Piazza, Margie L. Clapper, Wen-Chi L. Chang. Novel non-COX inhibitory sulindac derivative with PDE10 inhibitory activity reduces incidence and multiplicity of colorectal adenomas in the APC+/min-FCCC mouse model. [abstract]. In: Proceedings of the AACR Special Conference on Colorectal Cancer: From Initiation to Outcomes; 2016 Sep 17-20; Tampa, FL. Philadelphia (PA): AACR; Cancer Res 2017;77(3 Suppl):Abstract nr A30.

Fixed-Dose Combinations of Pioglitazone and Metformin for Lung Cancer Prevention

Combination treatment with pioglitazone and metformin is utilized clinically in the treatment of type II diabetes. Treatment with this drug combination reduced the development of aerodigestive cancers in this patient population. Our goal is to expand this treatment into clinical lung cancer chemoprevention. We hypothesized that dietary delivery of metformin/pioglitazone would prevent lung adenoma formation in A/J mice in a benzo[a]pyrene (B[a]P)-induced carcinogenesis model while modulating chemoprevention and anti-inflammatory biomarkers in residual adenomas. We found that metformin (500 and 850 mg/kg/d) and pioglitazone (15 mg/kg/d) produced statistically significant decreases in lung adenoma formation both as single-agent treatments and in combination, compared with untreated controls, after 15 weeks. Treatment with metformin alone and in combination with pioglitazone resulted in statistically significant decreases in lung adenoma formation at both early- and late-stage interventions. Pioglitazone alone resulted in significant decreases in adenoma formation only at early treatment intervention. We conclude that oral metformin is a viable chemopreventive treatment at doses ranging from 500 to 1,000 mg/kg/d. Pioglitazone at 15 mg/kg/d is a viable chemopreventive agent at early-stage interventions. Combination metformin and pioglitazone performed equal to metformin alone and better than pioglitazone at 15 mg/kg/d. Because the drugs are already FDA-approved, rapid movement to human clinical studies is possible. Cancer Prev Res; 10(2); 116-23. ©2017 AACR.

Imaging Matrix Metalloproteases in Spontaneous Colon Tumors: Validation by Correlation with Histopathology

The use of fluorescent probes in conjunction with white-light colonoscopy is a promising strategy for improving the detection of precancerous colorectal lesions, in particular flat (sessile) lesions that do not protrude into the lumen of the colon. We describe a method for determining the sensitivity and specificity of an enzymatically activated near-infrared probe (MMPSense680) for the detection of colon lesions in a mouse model (APC^+/Min-FCCC) of spontaneous colorectal cancer. Fluorescence intensity correlates directly with the activity of matrix metalloproteinases (MMPs). Overexpression of MMPs is an early event in the development of colorectal lesions. Although the probe employed serves as a reporter of the activity of MMPs, our method can be applied to any fluorescent probe that targets an early molecular event in the development of colorectal tumors.

Abstract 5248: ED-71, an analogue of Vitamin D3, blocks the promotion but not the initiation of colorectal tumors in the Apc+/Min-FCCC mouse model

Results from several studies demonstrate an inverse relationship between circulating levels of Vitamin D and risk of colorectal cancer. Eldecalcitol (1α,25-dihydroxy-2β-(3-hydroxypropyloxy) Vitamin D3; ED-71) is a novel analog of calcitriol, the most active form of Vitamin D3. ED-71 is more potent in stimulating bone remodeling and has been approved in Japan for the treatment of osteoporosis. The goal of this study was to assess the ability of ED-71 to inhibit spontaneous colorectal adenomas in a unique strain of multiple intestinal neoplasia (Apc+/Min-FCCC) mice. Male mice (6 wks of age) were randomized to treatment groups based on colon tumor status (endoscopic confirmation as tumor-free or -bearing) and body weight (bw) and administered: vehicle (MCT), calcitriol (0.25 μg/kg bw), or ED-71 (0.05 or 0.1 μg/kg bw) by gavage. Mice were treated every other day and bws were recorded weekly. After 14 wks of treatment, the small intestines and colons were excised and examined for gross tumors. Colorectal tumors &gt;3 mm in diameter were frozen for gene expression analyses. The remaining tissue was fixed in formalin and processed for histological review. The multiplicity of gross small intestinal tumors in animals treated with ED-71 (both doses) was comparable to that of vehicle-treated controls. In contrast, the multiplicity of small intestinal tumors was elevated 34.6% over that of controls in animals treated with calcitriol (Mean ± SEM: 28.4 ± 2.6 vs. 21.1 ± 2.8, respectively; P = 0.034). The ability of ED-71 to inhibit colon tumorigenesis was evaluated independently in mice with vs. without tumors at treatment initiation. In tumor-bearing mice, neither calcitriol nor ED-71 (both doses) had any significant effect on the multiplicity of colorectal tumors as compared to control mice. However in tumor-free mice, ED-71 (0.1 μg/kg bw) reduced the mean incidence of adenomas (&gt; 4 crypts) by 47% (ED-71 - 45.5%, controls 92.3%; P = 0.02) and the multiplicity by 47.6% (Mean ± SEM: ED-71 - 1.1 ± 0.39, controls - 2.1 ± 0.72; P &gt; 0.05). In contrast, the multiplicity of microadenomas (≤ 4 crypts) was increased in mice treated with ED-71 (0.1 μg/kg bw) as compared to controls (0.9 ± 0.22 vs. 0.5 ± 0.25 P = 0.06, respectively). These findings suggest that ED-71 is effective in preventing the transition of microadenomas to mature adenomas. The lack of an effect of ED-71 on colon tumor development in mice bearing tumors at baseline could be due in part to loss of the Vitamin D receptor in colon adenomas, as confirmed by real-time PCR. Insight into the mechanism by which ED-71 inhibits adenoma development is being gained from analyses of Vitamin D signaling and microRNA expression in treated colonic epithelial cells. These promising data provide support for future studies to determine the potential utility of ED-71 in preventing colorectal cancer in high-risk patients found to be tumor-free during surveillance endoscopy. (Supported by NCI HHSN261201200015I)

Citation Format: Wen-Chi L. Chang, Harry S. Cooper, Esther Kaunga, Lisa Vanderveer, Jing Peng, Suen S. Chen, Margie L. Clapper. ED-71, an analogue of Vitamin D3, blocks the promotion but not the initiation of colorectal tumors in the Apc+/Min-FCCC mouse model. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 5248.

5MeCDDO Blocks Metabolic Activation but not Progression of Breast, Intestine, and Tongue Cancers. Is Antioxidant Response Element a Prevention Target?

The preventive efficacy of the triterpenoid 5MeCDDO was tested in two models of mammary cancer, the Min model of intestinal cancer, and a chemically induced model of head and neck cancer. In one model of mammary cancer, female Sprague-Dawley rats were administered MNU at 50 days of age, and 5MeCDDO (27 ppm) was administered in the diet beginning 5 days later for the duration of the study; 5MeCDDO was ineffective. In contrast, in a model examining initiation of mammary cancers by the procarcinogen dimethyl-benzanthracene, 5, 6-benzoflavone (500 ppm, an Ah receptor agonist) or 5MeCDDO (27 or 2.7 ppm) decreased tumor multiplicity by 90%, 80%, and 50%, respectively. This anti-initiating effect which is presumably mediated by altered metabolic activation parallels our observation that 5MeCDDO induced proteins of various antioxidant response element (ARE)-related phase II drug-metabolizing enzymes [e.g., GST Pi, AKR 7A3 (aflatoxicol), epoxide hydrolase, and quinone reductase] in the liver. 5MeCDDO tested in the 4-nitroquinoline-l-oxide (4-NQO) head and neck cancer model failed to decrease tumor incidence or invasiveness. In the Min mouse model of intestinal cancer, a high dose of 5MeCDDO (80 ppm) was weakly effective in reducing adenoma multiplicity [∼30% (P < 0.05)]; however, a lower dose was totally ineffective. These findings question whether measuring increased levels of certain ARE-related genes (e.g., quinone reductase, GST Pi), indicating decreased carcinogen activation are sufficient to imply general chemopreventive efficacy of a given agent or mixture. Cancer Prev Res; 9(7); 616-23. ©2016 AACR.

MMP-13 In-Vivo Molecular Imaging Reveals Early Expression in Lung Adenocarcinoma

Introduction

Several matrix metalloproteinases (MMPs) are overexpressed in lung cancer and may serve as potential targets for the development of bioactivable probes for molecular imaging.

Objective

To characterize and monitor the activity of MMPs during the progression of lung adenocarcinoma.

Methods

K-ras^LSL-G12D mice were imaged serially during the development of adenocarcinomas using fluorescence molecular tomography (FMT) and a probe specific for MMP-2, -3, -9 and -13. Lung tumors were identified using FMT and MRI co-registration, and the probe concentration in each tumor was assessed at each time-point. The expression of Mmp2, -3, -9, -13 was quantified by qRT-PCR using RNA isolated from microdissected tumor cells. Immunohistochemical staining of overexpressed MMPs in animals was assessed on human lung tumors.

Results

In mice, 7 adenomas and 5 adenocarcinomas showed an increase in fluorescent signal on successive FMT scans, starting between weeks 4 and 8. qRT-PCR assays revealed significant overexpression of only Mmp-13 in mice lung tumors. In human tumors, a high MMP-13 immunostaining index was found in tumor cells from invasive lesions (24/27), but in none of the non-invasive (0/4) (p=0.001).

Conclusion

MMP-13 is detected in early pulmonary invasive adenocarcinomas and may be a potential target for molecular imaging of lung cancer.

Sulindac selectively inhibits colon tumor cell growth by activating the cGMP/PKG pathway to suppress Wnt/β-catenin signaling

Nonsteroidal anti-inflammatory drugs (NSAID) display promising antineoplastic activity for colorectal and other cancers, but toxicity from COX inhibition limits their long-term use for chemoprevention. Previous studies have concluded that the basis for their tumor cell growth inhibitory activity does not require COX inhibition, although the underlying mechanism is poorly understood. Here, we report that the NSAID sulindac sulfide inhibits cyclic guanosine 3',5'-monophosphate phosphodiesterase (cGMP PDE) activity to increase intracellular cGMP levels and activate cGMP-dependent protein kinase (PKG) at concentrations that inhibit proliferation and induce apoptosis of colon tumor cells. Sulindac sulfide did not activate the cGMP/PKG pathway, nor affect proliferation or apoptosis in normal colonocytes. Knockdown of the cGMP-specific PDE5 isozyme by siRNA and PDE5-specific inhibitors tadalafil and sildenafil also selectively inhibited the growth of colon tumor cells that expressed high levels of PDE5 compared with colonocytes. The mechanism by which sulindac sulfide and the cGMP/PKG pathway inhibits colon tumor cell growth involves the transcriptional suppression of β-catenin to inhibit Wnt/β-catenin T-cell factor transcriptional activity, leading to downregulation of cyclin D1 and survivin. These observations suggest that safer and more efficacious sulindac derivatives can be developed for colorectal cancer chemoprevention by targeting PDE5 and possibly other cGMP-degrading isozymes.

Abstract 2273: Metformin promotes tumorigenesis in animal models of cancer prevention

Metformin is a bi-guanidine employed in treating Type II diabetes. Epidemiologic studies have suggested that diabetics receiving metformin vs thialidizones or insulin have a lower incidence of cancer. In addition, metformin decreases levels of AMPK and IGF1; encouraging its use in both cancer prevention and therapy settings. Most preclinical studies with metformin have employed cell culture or xenografts. We examined its efficacy in multiple in situ animal cancer models. The preventive effect of Metformin administered by gavage or in the diet, at roughly the human equivalent dose (HED), was determined in four standard animal models: (1) methylnitrosourea (MNU)-induced ER+ mammary cancers; (2) MMTV-Neu ER− mammary cancers; (3) hydroxybutyl(butyl)nitrosamine (OH-BBN) induced urinary bladder cancers; and (4) Min mouse model of intestinal tumorigenesis. In the MNU model, Metformin (150 or 50 mg/Kg BW/day) was ineffective as a preventive dose; decreasing neither tumor multiplicity nor latency. Furthermore, both doses increased final tumor weights in treated rats. PK studies at the higher dose of Metformin (150 mg/kg BW/day) showed serum levels slightly higher than humans taking 1.5 g per day. In the MMTV-Neu model, dietary metformin (1200 PPM in diet) decreased the latency of tumor development as well as slightly, but insignificantly, increasing the final tumor multiplicity. Metformin (1200 ppm in diet) in the Min mouse model marginally increased the multiplicity of intestinal adenomas. In contrast, the NSAID naproxen (400 ppm in diet) examined simultaneously in the min mouse strongly inhibited adenoma development. Metformin (150 mg/Kg BW/day) in the OH-BBN induced model of urinary bladder cancer failed to significantly reduce bladder cancers despite relatively high levels of Metformin in the urine. In the MNU model, when rats were placed on a high fat diet to induce a pre-diabetic state, we observed roughly a 20% decrease in tumor multiplicity in the metformin treated rats (P&gt; 0.10). In contrast, tamoxifen and Targretin (an RXR agonist) that were used as positive controls were highly effective in rats on a high fat diet. Metformin didn't decrease tumorigenesis in these standard models, but actually increased tumor formation (incidence, multiplicity, weight) in three of the four models at their HED. These results should particularly discourage any large phase clinical trials in individuals without insulin resistance. The final study certainly raises the question whether the agent might be effective in animals that are diabetic or show insulin resistance

Citation Format: Clinton J. Grubbs, Margie L. Clapper, Joel M. Reid, Vernon E. Steele, Ronald A. Lubet. Metformin promotes tumorigenesis in animal models of cancer prevention. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2273. doi:10.1158/1538-7445.AM2013-2273

Estrogen metabolism within the lung and its modulation by tobacco smoke

Although estrogen and the enzymes responsible for its metabolism have been detected within the lung, the ability of this tissue to metabolize estrogen has not been demonstrated previously. The goal of this study was to characterize the profile of estrogen metabolites within the murine lung and to determine the effect of tobacco smoke exposure on metabolite levels. Use of liquid chromatography-tandem mass spectrometry led to the detection of three estrogens (E1, E2 and E3) and five estrogen metabolites (2-OHE1, 4-OHE1, 4-OHE2, 2-OMeE1 and 2-OMeE2) within the perfused lung, with 4-OHE1 being the most abundant species. Levels of 4-OHEs, carcinogenic derivatives produced primarily by cytochrome P450 1B1 (Cyp1b1), were 2-fold higher in females than males. Deletion of Cyp1b1 in females led to a dramatic reduction (21-fold) in 4-OHEs, whereas levels of 2-OHE1 and the putative protective estrogen metabolite 2-OMeE2 were increased (2.4- and 5.0-fold, respectively) (P = 0.01). Similar quantitative differences in estrogen metabolite levels were observed between Cyp1b1 null and wild-type males. Exposure of female mice to tobacco smoke for 8 weeks (2h per day, 5 days per week) increased the levels of 4-OHE1 (4-fold) and 2-OHE2 (2-fold) within the lung while reducing the total concentration of 2-OMeEs to 70% of those of unexposed controls. These data suggest that tobacco smoke accelerates the production of 4-OHEs within the lung; carcinogenic metabolites that could potentially contribute to lung tumor development. Thus, inhibition of CYP1B1 may represent a promising strategy for the prevention and treatment of lung cancer.

Differential response of flat and polypoid colitis-associated colorectal neoplasias to chemopreventive agents and heterocyclic amines

Individuals with ulcerative colitis face an increased risk of developing colorectal cancer and would benefit from early chemopreventive intervention. Results from preclinical studies in the mouse model of dextran sulfate sodium-induced colitis demonstrate that flat and polypoid colitis-associated dysplasias arise via distinct genetic pathways, impacted by the allelic status of p53. Furthermore, flat and polypoid dysplasias vary in their response to induction by the heterocyclic amine 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) and inhibition by 5-aminosalicylic acid, a common therapy for the maintenance of colitis patients. These data suggest that use of combination therapy is essential for the optimal inhibition of colitis-associated colorectal cancer.

Estrogen and cytochrome P450 1B1 contribute to both early- and late-stage head and neck carcinogenesis

Squamous cell carcinoma of the head and neck (HNSCC) is the sixth most common type of cancer in the United States. The goal of this study was to evaluate the contribution of estrogens to the development of HNSCCs. Various cell lines derived from early- and late-stage head and neck lesions were used to characterize the expression of estrogen synthesis and metabolism genes, including cytochrome P450 (CYP) 1B1, examine the effect of estrogen on gene expression, and evaluate the role of CYP1B1 and/or estrogen in cell motility, proliferation, and apoptosis. Estrogen metabolism genes (CYP1B1, CYP1A1, catechol-o-methyltransferase, UDP-glucuronosyltransferase 1A1, and glutathione-S-transferase P1) and estrogen receptor (ER) β were expressed in cell lines derived from both premalignant (MSK-Leuk1) and malignant (HNSCC) lesions. Exposure to estrogen induced CYP1B1 2.3- to 3.6-fold relative to vehicle-treated controls (P = 0.0004) in MSK-Leuk1 cells but not in HNSCC cells. CYP1B1 knockdown by shRNA reduced the migration and proliferation of MSK-Leuk1 cells by 57% and 45%, respectively. Exposure of MSK-Leuk1 cells to estrogen inhibited apoptosis by 26%, whereas supplementation with the antiestrogen fulvestrant restored estrogen-dependent apoptosis. Representation of the estrogen pathway in human head and neck tissues from 128 patients was examined using tissue microarrays. The majority of the samples exhibited immunohistochemical staining for ERβ (91.9%), CYP1B1 (99.4%), and 17β-estradiol (88.4%). CYP1B1 and ERβ were elevated in HNSCCs relative to normal epithelium (P = 0.024 and 0.008, respectively). These data provide novel insight into the mechanisms underlying head and neck carcinogenesis and facilitate the identification of new targets for chemopreventive intervention.

Abstract 1602: Time-to-recurrence is decreased in head and neck cancer patients with a common cytochrome P450 1B1 variant (N453S); epidemiological and in vitro findings

Squamous cell carcinoma of the head and neck (HNSCC) is the sixth most common type of cancer. Major risk factors for HNSCC in Western countries include tobacco and alcohol use. Carcinogenic components of tobacco smoke and ethanol can be metabolized by cytochrome P450 1B1 (CYP1B1) into mutagenic intermediates. Several common single nucleotide polymorphisms (SNPs) that introduce an amino acid change have been identified in the coding region of CYP1B1. Two of these SNPs (R48G and A119S) are linked and their function is unclear. The L432V variant has been associated with increased CYP1B1 activity while the N453S variant has been shown to accelerate the degradation of CYP1B1. The goal of this study was to evaluate the contribution of common SNPs in CYP1B1 to both the recurrence of HNSCC and overall survival of patients with HNSCC. Patients (N=155) with HNSCC, excluding oropharynx and nasopharynx, were diagnosed at FCCC between 2001-2008 (median time of follow-up - 3.3 years). DNA samples were genotyped for CYP1B1 SNPs using standard TaqMan assays. The impact of polymorphic genotypes on overall survival and recurrence was assessed using the Kaplan-Meier estimation method and the Cox proportional hazards model. Time-to-recurrence for N453S carriers was significantly greater than that of those carrying the wild-type genotype (p = 0.03). Furthermore, among patients with wild-type CYP1B1, women had a shorter time-to-recurrence than men (p = 0.02). The latter result was consistent with the known ability of CYP1B1 to metabolize estrogens to potentially carcinogenic intermediates. No difference in either survival or recurrence was observed among carriers of either R48G or L432V, as compared to wild-type carriers. In order to begin to understand the mechanism by which the N453S polymorphism may confer a shorter time-to-recurrence, cultured HNSCC cells (SCC15 and UPCI:SCC56) were transfected with plasmids encoding either wild-type CYP1B1 or variant CYP1B1 (N453S) as well as cytochrome P450 oxidoreductase (required for electron transfer) and green fluorescent protein (to measure transfection efficiency). The impact of the variant (N453S) and wild-type CYP1B1 proteins on cell proliferation and apoptosis was compared using the Fluorescent DNA Quantitation kit and the Nexin reagent, respectively. Cells with abundant levels of the N453S variant exhibited a rate of proliferation that was 5 to 8-fold lower than that of cells that overexpressed wild-type CYP1B1. In contrast, the rate of apoptosis among cells overexpressing either wild-type or variant CYP1B1 was comparable. These data provide novel insight into the mechanisms underlying carcinogenesis of the head and neck. More accurate identification of HNSCC patients with a poor prognosis could lead to new opportunities for tailored intervention with more aggressive therapeutic and surveillance strategies.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1602. doi:1538-7445.AM2012-1602

Abstract 4816: Tobacco smoke modulates estrogen metabolism in the mouse lung

Tobacco smoke is the major risk factor for lung cancer; the leading cause of cancer death in both men and women in the US and worldwide. Recent studies suggest that the female hormone estrogen promotes lung cancer development. However, the relationship between tobacco smoke exposure and estrogen is not well studied. Previous data from our lab showed that whole-body exposure to tobacco smoke induced the expression of the phase I detoxification enzyme cytochrome P450 1B1 (CYP1B1) within the lungs of female A/J mice. CYP1B1 activates polyaromatic hydrocarbons in tobacco smoke and also converts estrogen to catechol metabolites, in particular 4-hydroxy estrogens (4-OHEs), which are known to be carcinogenic. The goal of this study was to characterize the profile of estrogen metabolites within the lung using a novel high-performance liquid chromatography/electrospray ionization/tandem mass spectrometry (HPLC/ESI/MS/MS) protocol. Three estrogens (E1, E2 and E3) and five estrogen metabolites (2-OHE1, 4-OHE1, 4-OHE2, 2-OMeE1 and 2-OMeE2) were detected in perfused murine lungs, with 4-OHE1 identified as the most abundant estrogen metabolite. The levels of both 4-OHE1 and 4-OHE2 were 2-fold higher within the lungs of female mice as compared to those of males. This elevation was maintained when total 4-OHE levels were normalized to total estrogen (sum of estrogen and its metabolites, p=0.009). In contrast, no gender difference was observed in 2-OHE1 levels. This estrogen metabolite profile is consistent with the results from gene expression analyses, which revealed that the ratio of CYP1B1 to CYP1A1 transcripts (CYP1A1 produces 2-OHE) was elevated (2-fold) in females as compared to males (p=0.05). To assess the impact of tobacco smoke on the profile of estrogen metabolites within the lung, female mice were exposed to tobacco smoke for 8 weeks and estrogen metabolite levels were measured by HPLC/ESI/MS/MS. As expected, the levels of 4-OHEs were significantly higher within the lungs of mice exposed to tobacco smoke (4-fold for 4-OHE1 and 2-fold for 2-OHE2) as compared to controls exposed to filtered air (p=0.00003 and 0.0007, respectively). Interestingly, the level of total 2-OMeE, a putative protective estrogen metabolite, was decreased to 70% of controls in mice exposed to tobacco smoke (p=0.005) while 2-OHE levels were comparable in control and smoke-exposed animals. These results suggest that tobacco smoke accelerates the production of carcinogenic 4-OHEs within the lung; metabolites that could potentially contribute to lung tumor development. Furthermore, CYP1B1 may represent a molecular target for therapeutic intervention in lung tumor formation. Future studies will focus on comparing the profile of estrogen metabolites in human lung tissue from never smokers and current smokers. This work was supported by funds from the Estate of Jane Villon and the Kitty Jackson Fund.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4816. doi:1538-7445.AM2012-4816

Chemopreventive efficacy of Targretin in rodent models of urinary bladder, colon/intestine, head and neck and mammary cancers

The chemopreventive efficacy of Targretin was evaluated in various rodent cancer models. In the rat model of 4-hydroxybutyl(butyl)nitrosamine (OH-BBN)-induced urinary bladder cancer, it was found that Targretin administered in the diet (beginning one week after the last OH-BBN treatment) for 5.5 months increased the number and size of urinary bladder cancers. In the azoxymethane (AOM)-induced model of colon carcinogenesis (in which rats develop minimally invasive colonic cancers), Targretin was ineffective as a chemopreventive agent, decreasing neither tumor incidence nor multiplicity. Treatment of Min mice with Targretin for 45 days similarly failed to decrease the multiplicity of small intestinal tumors. Similarly, no preventive efficacy was noted for Targretin when the incidence of tumors in the head and neck model (squamous cell tongue tumors) induced by 4-nitroquinoline 1-oxide (4-NQO) were examined. In contrast, use of even a suboptimal dose of Targretin (40 ppm) in a sensitive breast cancer model [methylnitrosourea (MNU)-induced ER+ mammary cancers] reduced cancer multiplicity by 60%. Finally, based on the hypothesis that Targretin may decrease the expression of COX‑2, the effects of Targretin and COX inhibitors were compared in these models. There was minimal overlap of efficacy. That is, models which were relatively susceptible to NSAIDs or COX-2 inhibitors tended not to be sensitive to Targretin and vice versa.

Abstract 856: Association of high levels of folate with increased risk for colitis-associated colorectal neoplasia

Low folate levels are known to be a risk factor for multiple human diseases including colorectal cancer. However, the relationship between folate levels and the prevention or development of colorectal cancer remains controversial. Patients with ulcerative colitis often possess low levels of folate due to inadequate intake and malabsorption of nutrients. Thus, folic acid supplementation is highly recommended despite very limited information regarding the effect of folic acid on the progression of colitis-associated colorectal cancer. The major objectives of the present study are to evaluate folate levels during the progression of colitis-associated colon cancer and to assess the potential functional role of folic acid supplementation on the growth of colon cancer cells. To study the effect of inflammation on levels of folate, acute and chronic colitis were induced within the mouse colon by administering 2 cycles of 3% dextran sulfate sodium (DSS) following one injection of azoxymethane (AOM; 7.4 mg/kg); a regimen that ultimately leads to the formation of colitis-associated dysplasias and carcinomas. At 10+, 12 and 19 wks of age, corresponding to acute colitis, chronic colitis, and colitis-associated dysplasia, respectively, blood samples were collected retro-orbitally and plasma folate levels were measured using stable isotope dilution liquid chromatography-multiple reaction monitoring/mass spectrometry. At sacrifice, the histopathology of the colon was correlated with plasma folate levels. Levels of plasma folate were reduced 33% (78.4 + 7.2 nM vs. 116.2 + 15.6 nM, p&lt;0.05) and 21% (110. 4 + 5.2 nM vs. 138.2 + 10.8 nM, p&lt;0.05) in AOM/DSS-treated mice at 10+ or 12 wks of age, respectively, as compared to age-matched mice treated with AOM alone. Surprisingly, plasma folate levels were elevated 12% in AOM/DSS-treated mice exhibiting multiple colitis-associated dysplasias (19 wks of age), as compared to control mice without tumors treated with AOM only. Administration of 5-aminosalicylic acid (5-ASA) to colitic mice at 75 mg/kg, a dose that inhibits the multiplicity of dysplasias by 50%, decreased plasma folate to a level lower than that of AOM/DSS controls (77.9 +10.7 nM vs. 199.0 + 25.1 nM, p&lt;0.001). The effect of folic acid supplementation on cellular signaling pathways was evaluated in SW480 colon carcinoma cells cultured in the presence of low- or high-dose folic acid. Western blot analyses using antibodies against phospho-ERK1/2 and phospho-GSK3β revealed that exposure to high-dose folic acid increased phosphorylated ERK1/2 and reduced phosphorylated GSK3β by 2.0- and 2.5-fold, respectively, as compared to cells exposed to low-dose folic acid. These in vitro and in vivo data, when combined, suggest that high levels of folic acid may increase risk for colitis-associated neoplasia via the ERK/MAPK and GSK3β pathways. Supported by NIH R01 CA124693.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 856. doi:10.1158/1538-7445.AM2011-856

Functional characterization of peroxisome proliferator-activated receptor-β/δ expression in colon cancer

This study critically examined the role of PPARβ/δ in colon cancer models. Expression of PPARβ/δ mRNA and protein was lower and expression of CYCLIN D1 protein higher in human colon adenocarcinomas compared to matched non-transformed tissue. Similar results were observed in colon tumors from Apc(+/Min-FCCC) mice compared to control tissue. Dietary administration of sulindac to Apc(+/Min-FCCC) mice had no influence on expression of PPARβ/δ in normal colon tissue or colon tumors. Cleaved poly (ADP-ribose) polymerase (PARP) was either increased or unchanged, while expression of 14-3-3ε was not influenced in human colon cancer cell lines cultured with the PPARβ/δ ligand GW0742 under conditions known to increase apoptosis. While DLD1 cells exhibited fewer early apoptotic cells after ligand activation of PPARβ/δ following treatment with hydrogen peroxide, this change was associated with an increase in late apoptotic/necrotic cells, but not an increase in viable cells. Stable over-expression of PPARβ/δ in human colon cancer cell lines enhanced ligand activation of PPARβ/δ and inhibition of clonogenicity in HT29 cells. These studies are the most quantitative to date to demonstrate that expression of PPARβ/δ is lower in human and Apc(+/Min-FCCC) mouse colon tumors than in corresponding normal tissue, consistent with the finding that increasing expression and activation of PPARβ/δ in human colon cancer cell lines inhibits clonogenicity. Because ligand-induced attenuation of early apoptosis can be associated with more late, apoptotic/necrotic cells, but not more viable cells, these studies illustrate why more comprehensive analysis of PPARβ/δ-dependent modulation of apoptosis is required in the future.

Abstract B39: Estrogen and cytochrome P450 1B1 contribute to early-stage head and neck carcinogenesis

Squamous cell carcinoma of the head and neck (HNSCC) is the sixth most common type of cancer in the U.S. Major risk factors for HNSCC include tobacco and alcohol use. Data from this group and others suggest that estrogens may also contribute to the development of HNSCCs. We demonstrated previously that various cell lines derived from both premalignant (MSK-Leuk1) and HNSCCs express estrogen metabolism genes, including cytochrome P450 1B1 (CYP1B1) and estrogen receptor β (ERβ). CYP1B1 is the major enzyme that catalyzes the formation of carcinogenic metabolites of both 17β-estradiol (E2) and constituents of tobacco smoke. The goal of the present study was to assess the impact of E2 exposure on CYP1B1 expression and evaluate the role of E2 and CYP1B1 in regulating motility, apoptosis and proliferation of epithelial cells of the head and neck. Cell lines established from a dysplastic leukoplakia of the oral cavity (MSK-Leuk1) and five human tongue SCCs were exposed to either vehicle (0.01% ethanol) or E2 (1 nM) for 24 hours and the level of CYP1B1 transcripts was analyzed by quantitative real-time PCR. Exposure to E2 induced CYP1B1 expression in MSK-Leuk1 cells (2.3-fold relative to vehicle-treated controls, P=0.0004) but not in HNSCC cells.

To further evaluate the contribution of CYP1B1 to early head and neck carcinogenesis, CYP1B1 was knocked down in MSK-Leuk1 cells by lentivirus encoded shRNA, and the effect of CYP1B1 depletion on cell motility, proliferation and apoptosis was analyzed. Cell motility was evaluated by monitoring the ability of vector and shRNA-expressing cells to close an evenly distributed gap in the cell monolayer over a 16-hour period. CYP1B1 knockdown inhibited the migration of MSK-Leuk1 cells by 57%. Proliferation and apoptosis were assessed in MSK-Leuk1 cells (expressing either vector or CYP1B1 shRNA) exposed to either vehicle or E2 (1 nM) for 3 days. CYP1B1 knockdown inhibited the proliferation of MSK-Leuk1 cells by 45%, relative to vector expressing cells, as measured by total DNA content. E2 inhibited apoptosis by 26%, as compared to vehicle-treated cells, as measured using a Nexin kit.

These data provide novel insight into the mechanisms underlying head and neck carcinogenesis and may facilitate the identification new targets for chemopreventive intervention.

Citation Information: Cancer Prev Res 2010;3(12 Suppl):B39.

Early changes in gene expression induced by tobacco smoke: Evidence for the importance of estrogen within lung tissue

Lung cancer is the leading cause of cancer deaths in the United States, surpassing breast cancer as the primary cause of cancer-related mortality in women. The goal of the present study was to identify early molecular changes in the lung induced by exposure to tobacco smoke and thus identify potential targets for chemoprevention. Female A/J mice were exposed to either tobacco smoke or HEPA-filtered air via a whole-body exposure chamber (6 h/d, 5 d/wk for 3, 8, and 20 weeks). Gene expression profiles of lung tissue from control and smoke-exposed animals were established using a 15K cDNA microarray. Cytochrome P450 1b1, a phase I enzyme involved in both the metabolism of xenobiotics and the 4-hydroxylation of 17beta-estradiol (E(2)), was modulated to the greatest extent following smoke exposure. A panel of 10 genes were found to be differentially expressed in control and smoke-exposed lung tissues at 3, 8, and 20 weeks (P < 0.001). The interaction network of these differentially expressed genes revealed new pathways modulated by short-term smoke exposure, including estrogen metabolism. In addition, E(2) was detected within murine lung tissue by gas chromatography-coupled mass spectrometry and immunohistochemistry. Identification of the early molecular events that contribute to lung tumor formation is anticipated to lead to the development of promising targeted chemopreventive therapies. In conclusion, the presence of E(2) within lung tissue when combined with the modulation of cytochrome P450 1b1 and other estrogen metabolism genes by tobacco smoke provides novel insight into a possible role for estrogens in lung cancer.

Abstract 5695: Nitric oxide-donating naproxen inhibits β-catenin-mediated TCF signaling in colorectal cancer cells more effectively than naproxen

Results from recent clinical and epidemiological studies continue to suggest that non-steroidal anti-inflammatory drugs (NSAIDs) are promising chemopreventive agents with activity against colorectal cancer. Nitric oxide (NO)-donating NSAIDs represent a novel class of agents that have been reported to have greater safety and higher efficacy in inhibiting the growth of cancer cells than the parent compounds. However, the mechanism of chemopreventive action of NO-NSAIDs is not well elucidated. Dysregulation of the WNT/ β-catenin pathway is one of the earliest events during tumorigenesis in the colon and thus an attractive molecular target for chemopreventive intervention. The major goal of the current study was to compare the effect of naproxen, an NSAID commonly used to reduce pain, fever and inflammation, and NO-naproxen on β-catenin-mediated TCF4 signaling in colon cancer cells. Human SW480 colon carcinoma cells that express mutant APC were transfected with either pGL3 basic plasmid or a luciferase reporter construct under the control of 3 copies of either wild-type (pGL3-OT) or mutated (pGL3-OF) TCF4 regulatory element using LipofectAmine 2000. Cells were treated with 0.01 - 0.4 mM naproxen or NO-naproxen or vehicle (water or DMSO, respectively) and harvested 48 hrs later. Cell lysates were prepared and luciferase activity was measured using the Promega Luciferase Assay kit. The results demonstrate that NO-naproxen reduces β-catenin-mediated TCF4 transcriptional activity in SW480 cells in a dose dependent manner. At a given dose, the luciferase activity of cells exposed to NO-naproxen was approximately 50% of that of cells treated with the parent compound. In conclusion, these data suggest that the chemopreventive activity of NO-naproxen is attributed in part to its ability to inhibit the transcriptional activation of TCF4; a response that is greater than that of the conventional drug naproxen. The availability of a multiple intestinal neoplasia mouse model that, unlike the conventional strain, develops multiple colorectal adenomas provides a unique opportunity to compare the efficacy of these agents against colorectal tumor growth in vivo. Supported by NIH N01 CN43309.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5695.

Abstract 2459: Early changes in gene expression induced by tobacco smoke: Evidence for the importance of estrogen within lung tissue

Lung cancer is the leading cause of cancer deaths in the U.S., surpassing breast cancer as the primary cause of cancer-related mortality in women. The goal of the present study was to identify early molecular changes in the lung induced by exposure to tobacco smoke and thus identify potential targets for chemoprevention. Female A/J mice were exposed to either tobacco smoke or HEPA-filtered air via a whole-body exposure chamber (6 h/day; 5 days/wk for 3, 8 and 20 wk). Gene expression profiles of lung tissue from control and smoke-exposed animals were established using a 15 K cDNA microarray. Cytochrome P450 1b1 (Cyp1b1), a Phase I enzyme involved in both the metabolism of xenobiotics and the 4-hydroxylation of 17β estradiol, was modulated to the greatest extent following smoke exposure. A panel of 10 genes were found to be differentially expressed between control and smoke-exposed animals at 3, 8 and 20 wk (P &lt; 0.001). The interaction network of these differentially expressed genes revealed new pathways modulated by short-term smoke exposure including estrogen metabolism. In addition, 17β-estradiol was detected within murine lung tissue by gas chromatography coupled mass spectroscopy and immunohistochemistry. Identification of the early molecular events that contribute to lung tumor formation is anticipated to lead to the development of promising targeted chemopreventive therapies. In conclusion, the presence of 17β-estradiol within lung tissue when combined with the modulation of Cyp1b1 and other estrogen metabolism genes by tobacco smoke provides novel insight into a possible role for estrogens in lung cancer. (Supported by fellowships from the AACR-Pennsylvania Department of Health and the ASPO/CRPF, the Estate of Jane Villon, the Jerome M. Spencer and Arnold Zaslow Family Foundation and NIH CA-96310).

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2459.