Adenovirus and Oxaliplatin cooperate as agnostic sensitizers for immunogenic cell death in colorectal carcinoma

Treatments with cytotoxic agents or viruses may cause Immunogenic Cell Death (ICD) that immunize tumor-bearing hosts but do not cause complete regression of tumor. We postulate that combining two ICD inducers may cause durable regression in immunocompetent mice. ICD was optimized in vitro by maximizing calreticulin externalization in human colorectal carcinoma (CRC) cells by exposure to mixtures of Oxaliplatin (OX) and human adenovirus (AdV). Six mm diameter CT26 or 4T1 carcinomas in flanks of BALB/c mice were injected once intratumorally (IT) with OX, AdV or their mixture. Tumor growth, Tumor-Infiltrating Lymphocytes (TIL), nodal cytotoxicity, and rejection of a viable cell challenge were measured. Tumors injected IT once with an optimum mixture of 80 µM OX - AdV 25 Multiplicity of Infection (MOI) in PBS buffer were 17-29% the volume of control tumors. When buffer was changed from PBS to 5% dextrose in water (D5W), volumes of tumors injected IT with 80 µM OX-AdV 25 MOI were 10% while IT OX or AdV alone were 32% and 40% the volume of IT buffer-treated tumors. OX-AdV IT increased CD3+ TIL by 4-fold, decreased CD8+ PD-1+ TIL from 79% to 19% and induced cytotoxicity to CT26 cells in draining node lymphocytes while lymphocytes from CT26-bearing untreated mice were not cytotoxic. OX-AdV IT in D5W caused complete regression in 40% of mice. Long-term survivors rejected a contralateral challenge of CT26. The buffer for Oxaliplatin is critical. The two ICD inducer mixture is promising as an agnostic sensitizer for carcinomas like colorectal carcinoma.

Epigenetic re-wiring of breast cancer by pharmacological targeting of C-terminal binding protein

The C-terminal binding protein (CtBP) is an NADH-dependent dimeric family of nuclear proteins that scaffold interactions between transcriptional regulators and chromatin-modifying complexes. Its association with poor survival in several cancers implicates CtBP as a promising target for pharmacological intervention. We employed computer-assisted drug design to search for CtBP inhibitors, using quantitative structure-activity relationship (QSAR) modeling and docking. Functional screening of these drugs identified 4 compounds with low toxicity and high water solubility. Micro molar concentrations of these CtBP inhibitors produces significant de-repression of epigenetically silenced pro-epithelial genes, preferentially in the triple-negative breast cancer cell line MDA-MB-231. This epigenetic reprogramming occurs through eviction of CtBP from gene promoters; disrupted recruitment of chromatin-modifying protein complexes containing LSD1, and HDAC1; and re-wiring of activating histone marks at targeted genes. In functional assays, CtBP inhibition disrupts CtBP dimerization, decreases cell migration, abolishes cellular invasion, and improves DNA repair. Combinatorial use of CtBP inhibitors with the LSD1 inhibitor pargyline has synergistic influence. Finally, integrated correlation of gene expression in breast cancer patients with nuclear levels of CtBP1 and LSD1, reveals new potential therapeutic vulnerabilities. These findings implicate a broad role for this class of compounds in strategies for epigenetically targeted therapeutic intervention.

Two ICD Inducers are better than one for induction of anti-tumor immunity in cold carcinomas

Background

Cytotoxic agents and viruses cause Immunogenic Cell Death (ICD), which initiates a primary immune response in tumor-bearing hosts by releasing cellular antigens with immune chaperones. We postulate that two ICD inducers are better than one in immune competent mouse models of colorectal and breast cancer.

Methods

Approximately 6 mm diameter CT26 rectal or 4T1 breast carcinomas were established in groups of 5–7 BALB/c mice and injected once intratumorally (IT) with oxaliplatin (OX) mixed with a human adenovirus AdV optimized for calreticulin externalization in 3-D spheroids of human carcinomas. Tumor volumes were measured every other day and rate of growth analyzed by Rate-Based T/C Ratio at 19–21 days. Tumor-Infiltrating Lymphocytes (TIL) and nodal cytotoxicity were assessed 11 days after treatment.

Results

In 3 experiments with OX-AdV IT in PBS buffer the T/C ratios were 0.17–0.29 those of the volume of PBS IT injected mice. The T/C Ratio for OX-AdV IT in D5W (used to stabilize the OX) was 0.10 of the IT control volume with 0.32–0.40 for OX or AdV alone and with all groups different by P<0.05 by 2-way ANOVA. OX-AdV IT increased TIL by 4-fold and decreased CD8+PD-1+EOMES+ from 79% to 19% with a dramatic influx of CD8+PD-1-Eomes- T cells compared to PBS IT controls. Draining node lymphocytes were cytotoxic to CT26 cells from OX-AdV IT mice while lymphocytes from PBS IT mice were not. OX-AdV IT in D5W caused 40% of mice to be complete responders that later rejected a contralateral challenge of CT26.

Conclusions

The buffer for IT treatment with OX is critical. The two ICD inducer formulation with D5W is promising as a checkpoint therapy sensitizer for carcinomas that lack TIL or resist checkpoint inhibitor therapy like colorectal carcinoma.

Abstract 1156: Epigenetic re-wiring of breast cancer by pharmacological targeting of C-terminal binding protein

The C-terminal binding protein (CtBP) is a family of dimeric nuclear proteins whose levels are increased in cancers of the colon, ovaries, prostate and breast. Elevated CtBP expression is associated with poor cancer survival and can also distinguish those node negative breast cancer patients who will show worse survival. This implicates CtBP as both a biomarker and a promising candidate for therapeutic intervention. As a dimer, CtBP provides a scaffold that couples multiple different DNA-binding transcriptional regulators with a variety of chromatin modifying protein complexes to alter the epigenetic landscape throughout the nucleus. These properties provide the rationale for pharmacological targeting of CtBP to change epigenetically regulated gene expression in cancer cells. In this study, we employ computer assisted drug design to screen for optimal quantitative structure-activity relationships (QSARs) between small molecules and CtBP to identify 24 potential CtBP inhibitors. Functional screening of these compounds identifies 4 lead compounds with low toxicity and high water solubility. Treatment of breast cancer cells at micro-molar concentrations of these small molecular inhibitors induces significant de-repression of epigenetically silenced pro-epithelial genes in the mesenchymal, triple negative breast cancer cell line, MDA-MB-231. This re-activation is associated with eviction of CtBP from the respective gene promoters, disrupted recruitment of CtBP-chromatin modifying protein complexes, increased deposition of activating epigenetic histone marks, and upregulation of both pro-epithelial gene mRNA and protein expression. In functional assays, CtBP inhibition by these small molecular inhibitors decreases cellular invasion, and improves DNA repair. FRET (Förster resonance energy transfer) analysis demonstrates that CTBP inhibition results in decreased FRET intensity, suggesting that CTBP dimerization is repressed by CTBP inhibition. In addition, pharmacological inhibition of CtBP combines with established epigenetically targeted drugs to synergistically decrease cell migration and potentiate the reactivation of silenced pro-epithelial gene expression in triple negative cancer cells. Finally, CTBP inhibition results in transcriptional repression of MDR1 expression and reduces the population of Doxorubicin resistant cells in the triple negative breast cancer cell lines. These findings implicate the possible use of this class of compounds in strategies for therapeutic intervention that may increase the efficacy and decrease the acquired resistance to targeted therapeutic intervention in breast cancer.

Citation Format: Jung S. Byun, Samson Park, Dae IK Yi, Mohamed Kabbout, Genqing Liang, Kevin L. Gardner. Epigenetic re-wiring of breast cancer by pharmacological targeting of C-terminal binding protein [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1156. doi:10.1158/1538-7445.AM2017-1156

MicroRNA 17-92 cluster mediates ETS1 and ETS2-dependent RAS-oncogenic transformation

The ETS-family transcription factors Ets1 and Ets2 are evolutionarily conserved effectors of the RAS/ERK signaling pathway, but their function in Ras cellular transformation and biology remains unclear. Taking advantage of Ets1 and Ets2 mouse models to generate Ets1/Ets2 double knockout mouse embryonic fibroblasts, we demonstrate that deletion of both Ets1 and Ets2 was necessary to inhibit Hras^G12V induced transformation both in vitro and in vivo. Hras^G12V expression in mouse embryonic fibroblasts increased ETS1 and ETS2 expression and binding to cis-regulatory elements on the c-Myc proximal promoter, and consequently induced a robust increase in MYC expression. The expression of the oncogenic microRNA 17-92 cluster was increased in Hras^G12V transformed cells, but was significantly reduced when ETS1 and ETS2 were absent. MYC and ETS1 or ETS2 collaborated to increase expression of the oncogenic microRNA 17-92 cluster in Hras^G12V transformed cells. Enforced expression of exogenous MYC or microRNA 17-92 rescued Hras^G12V transformation in Ets1/Ets2-null cells, revealing a direct function for MYC and microRNA 17-92 in ETS1/ETS2-dependent Hras^G12V transformation.

Transcriptomic architecture of the adjacent airway field cancerization in non-small cell lung cancer

BACKGROUND

Earlier work identified specific tumor-promoting abnormalities that are shared between lung cancers and adjacent normal bronchial epithelia. We sought to characterize the yet unknown global molecular and adjacent airway field cancerization (FC) in early-stage non-small cell lung cancer (NSCLC).

METHODS

Whole-transcriptome expression profiling of resected early-stage (I-IIIA) NSCLC specimens (n = 20) with matched tumors, multiple cytologically controlled normal airways with varying distances from tumors, and uninvolved normal lung tissues (n = 194 samples) was performed using the Affymetrix Human Gene 1.0 ST platform. Mixed-effects models were used to identify differentially expressed genes among groups. Ordinal regression analysis was performed to characterize site-dependent airway expression profiles. All statistical tests were two-sided, except where noted.

RESULTS

We identified differentially expressed gene features (n = 1661) between NSCLCs and airways compared with normal lung tissues, a subset of which (n = 299), after gene set enrichment analysis, statistically significantly (P < .001) distinguished large airways in lung cancer patients from airways in cancer-free smokers. In addition, we identified genes (n = 422) statistically significantly and progressively differentially expressed in airways by distance from tumors that were found to be congruently modulated between NSCLCs and normal lung tissues. Furthermore, LAPTM4B, with statistically significantly increased expression (P < .05) in airways with shorter distance from tumors, was upregulated in human immortalized cells compared with normal bronchial epithelial cells (P < .001) and promoted anchorage-dependent and -independent lung cancer cell growth.

CONCLUSIONS

The adjacent airway FC comprises both site-independent profiles as well as gradient and localized airway expression patterns. Profiling of the airway FC may provide new insights into NSCLC oncogenesis and molecular tools for detection of the disease.

ETS2 mediated tumor suppressive function and MET oncogene inhibition in human non-small cell lung cancer

PURPOSE

The ETS2 transcription factor is an evolutionarily conserved gene that is deregulated in cancer. We analyzed the transcriptome of lung adenocarcinomas and normal lung tissue by expression profiling and found that ETS2 was significantly downregulated in adenocarcinomas. In this study, we probed the yet unknown functional role of ETS2 in lung cancer pathogenesis.

EXPERIMENTAL DESIGN

Lung adenocarcinomas (n = 80) and normal lung tissues (n = 30) were profiled using the Affymetrix Human Gene 1.0 ST platform. Immunohistochemical (IHC) analysis was conducted to determine ETS2 protein expression in non-small cell lung cancer (NSCLC) histologic tissue specimens (n = 201). Patient clinical outcome, based on ETS2 IHC expression, was statistically assessed using the log-rank and Kaplan-Meier tests. RNA interference and overexpression strategies were used to assess the effects of ETS2 expression on the transcriptome and on various malignant phenotypes.

RESULTS

ETS2 expression was significantly reduced in lung adenocarcinomas compared with normal lung (P < 0.001). Low ETS2 IHC expression was a significant predictor of shorter time to recurrence in NSCLC (P = 0.009, HR = 1.89) and adenocarcinoma (P = 0.03, HR = 1.86). Moreover, ETS2 was found to significantly inhibit lung cancer cell growth, migration, and invasion (P < 0.05), and microarray and pathways analysis revealed significant (P < 0.001) activation of the HGF pathway following ETS2 knockdown. In addition, ETS2 was found to suppress MET phosphorylation and knockdown of MET expression significantly attenuated (P < 0.05) cell invasion mediated by ETS2-specific siRNA. Furthermore, knockdown of ETS2 augmented HGF-induced MET phosphorylation, cell migration, and invasion.

CONCLUSION(S)

Our findings point to a tumor suppressor role for ETS2 in human NSCLC pathogenesis through inhibition of the MET proto-oncogene.

Abstract 2367: Transcriptomic architecture of the airway field cancerization in early-stage non-small cell lung cancer

Earlier work has identified in lung cancer a field cancerization (FC) phenomenon in which tumors and adjacent normal appearing tissues share specific molecular abnormalities (e.g., loss of heterozygosity) that may be highly pertinent to cancer pathogenesis. We sought to characterize the global molecular airway FC adjacent to early-stage non-small cell lung cancer (NSCLC) in an attempt to unravel profiles that may help to explain the development of the disease. We performed whole-transcript expression profiling of a set of resected early-stage NSCLC specimens (n=20 patients) with matched histologically normal airways of varying distance from the tumor and paired uninvolved normal lung tissue (n=194 samples). Using linear mixed-effects models, we derived FC profiles signifying genes concordantly differentially expressed between tumors and airways compared to normal lung tissues. Gene set enrichment analysis demonstrated that a subset of the genes (n=299) was significantly and congruently modulated between large airways of smokers with and without lung cancer. We then questioned whether the airway FC exhibits site from tumor-dependent expression patterns.

Ordinal regression analysis identified airway profiles (n=422 genes) that were significantly progressively expressed by distance from tumors and topologically organized into canonical cancer-associated pathways, such as eukaryotic initiation factor, p70S6K kinase, polo-like kinase and mammalian target of rapamycin signaling (all p&lt;0.001). In addition, the site-dependent airway profiles recapitulated NSCLC expression patterns and were concordantly modulated between tumors and uninvolved normal lung tissues pinpointing their probable roles in lung cancer pathogenesis. Quantitative real-time PCR (QRTPCR) analysis confirmed the differential expression of FC markers selected by both pathways analysis and statistical criteria. Notably, lysosome associated protein transmembrane 4 beta (LAPTM4B), a putative oncogene with no known role in lung carcinogenesis, was among the top 5 site-dependent FC markers and was significantly elevated in NSCLC and immortalized bronchial epithelial cell lines compared to normal cells. Furthermore, transient or stable knockdown of LAPTM4B by RNA interference decreased

NSCLC cell growth as well as anchorage-dependent and -independent colony formation. In conclusion, our efforts in understanding the adjacent molecular

FC in NSCLC unraveled airway profiles that 1) are, in part, relevant to lung cancer detection; 2) are modulated by distance from corresponding tumors; 3) recapitulate NSCLC expression patterns and 4) harbor markers engaged in mediating the lung malignant phenotype. Profiling the adjacent airway FC in conjunction with tumors, may provide additional insights into the molecular pathology of NSCLC. Funded in part by Department of Defense award W81XWH-10-1-1007.

Citation Format: Yuho Maki, Junya Fujimoto, Suk-Young Yoo, Adam Gower, Li Shen, Melinda M. Garcia, Mohamed Kabbout, Chi-Wan Chow, Waun Ki Hong, Neda Kalhor, Jing Wang, Cesar Moran, Avrum Spira, Kevin R. Coombes, Ignacio I. Wistuba, Humam Kadara. Transcriptomic architecture of the airway field cancerization in early-stage non-small cell lung cancer . [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 2367. doi:10.1158/1538-7445.AM2013-2367

Characterizing the molecular spatial and temporal field of injury in early-stage smoker non-small cell lung cancer patients after definitive surgery by expression profiling

Gene expression alterations in response to cigarette smoke have been characterized in normal-appearing bronchial epithelium of healthy smokers, and it has been suggested that adjacent histologically normal tissue displays tumor-associated molecular abnormalities. We sought to delineate the spatial and temporal molecular lung field of injury in smoker patients with early-stage non-small cell lung cancer (NSCLC; n = 19) who were accrued into a surveillance clinical trial for annual follow-up and bronchoscopies within 1 year after definitive surgery. Bronchial brushings and biopsies were obtained from six different sites in the lung at the time of inclusion in the study and at 12, 24, and 36 months after the first time point. Affymetrix Human Gene 1.0 ST arrays were used for whole-transcript expression profiling of airways (n = 391). Microarray analysis identified gene features (n = 1,165) that were nonuniform by site and differentially expressed between airways adjacent to tumors relative to more distant samples as well as those (n = 1,395) that were significantly altered with time up to 3 years. In addition, gene interaction networks mediated by phosphoinositide 3-kinase (PI3K) and extracellular signal-regulated kinase (ERK)1/2 were modulated in adjacent compared with contralateral airways and the latter network with time. Furthermore, phosphorylated AKT and ERK1/2 immunohistochemical expression were significantly increased with time (nuclear pAKT, P = 0.03; cytoplasmic pAKT, P < 0.0001; pERK1/2, P = 0.02) and elevated in adjacent compared with more distant airways (nuclear pAKT, P = 0.04; pERK1/2, P = 0.03). This study highlights spatial and temporal cancer-associated expression alterations in the molecular field of injury of patients with early-stage NSCLCs after definitive surgery that warrant further validation in independent studies.

Abstract 1721: Gene expression profiling of lung tumors and matched normal airways reveals common and disparate aberrant pathways in squamous cell carcinoma and adenocarcinoma development and potential markers for detection and targets for chemoprevention in early stage lung cancer

Detection and chemoprevention of non-small cell lung cancer (NSCLC) have been unsuccessful in part due to our limited knowledge of the pathogenesis of the disease. It has been suggested that normal airway epithelia share molecular abnormalities with tumors and may serve as progenitors for lung malignancies. We sought to analyze molecular profiles of lung adenocarcinomas and squamous cell carcinomas (SCCs), two major subtypes of NSCLC, and matched normal airways to elucidate aberrant expression patterns in early phases of lung tumorigenesis. All specimens were obtained from primary early stage NSCLC consented patients who did not receive neoadjuvant therapy (n=20). We profiled RNA isolated from tumors and normal lung as well as from brushings of multiple matched airways that were histologically confirmed to lack neoplastic or preneoplastic cells (n=194). Expression signatures signifying genes significantly and concurrently differentially expressed between both tumors and airways compared to normal lung tissue (tumor-airway-normal/TAN signatures) were then derived independently for SCC and smoker adenocarcinoma cases and were comprised of 1,803 and 1,938 genes, respectively. The TAN signatures effectively clustered tumor and airways from normal lung samples (p&lt;0.001). Further analysis showed that a subset of the genes separated SCC- and adenocarcinoma-adjacent airways. Moreover, pathways and gene-network analysis using Ingenuity pathways software highlighted similarities and differences in pathway modulation between airway epithelial fields of SCCs and adenocarcinomas. Embryonic stem cell and eicosanoid signaling pathways were most significantly modulated among those common to both TAN signatures (p&lt;0.001). Retinoic acid receptor and stem cell signaling pathways mediated by NANOG and lineage oncogene SOX2 were most significantly modulated in the SCC TAN signature, whereas NF-kB and PTEN signaling pathways were most prevalent in the adenocarcinoma TAN airway signature (all p&lt;0.001). Gene networks mediated by lineage oncogene NKX2-1/TITF-1 down-regulation and TP63 up-regulation, and networks mediated by increased expression of the MET and ERBB2 oncogenes were predominantly functionally modulated in the SCC and adenocarcinoma TAN signatures, respectively. Quantitative PCR analysis confirmed up-regulation of MET in adenocarcinomas and normal airways compared to normal lung. These findings highlight expression patterns and pathways that are deregulated differentially in the pathogenesis of lung adenocarcinomas and SCCs and thus offer detection markers as well as therapeutic targets to guide personalized chemoprevention in early stage NSCLC patients. Supported by DoD grant W81XWH-10-1-1007.

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 1721. doi:1538-7445.AM2012-1721

Abstract 2177: Tumor suppressor effects of ETS2 transcriptional factor in human non-small cell lung cancer

Advances in prevention and treatment of non-small cell lung cancer (NSCLC) are dependent in part on the characterization of tumor suppressor genes and oncogenes and the roles they elicit in the pathogenesis of this malignancy. Although v-ets erythroblastosis virus E26 oncogene homolog 2 (ETS2) is a canonical transcription factor that regulates various cancer-associated cellular and developmental processes including proliferation and migration, its function in lung carcinogenesis is still unknown. In this study we sought to examine the role of ETS2 in NSCLC pathogenesis. We first examined ETS2 mRNA expression in lung adenocarcinomas (n=80) and normal lung (n=30) which we profiled using microarrays, and in seven matched adenocarcinoma and normal lung pairs analyzed using next-generation sequencing technology. Both array and sequencing datasets revealed that ETS2 mRNA was significantly lower in lung adenocarcinomas relative to normal lung (p&lt;0.001) which was confirmed by quantitative PCR analysis. Moreover and in the microaray dataset, ETS2 mRNA expression was significantly anti-correlated with that of the proliferation marker KI67 (R=−0.59, p&lt;0.001). In addition, in silico analysis of publicly available datasets demonstrated that ETS2 mRNA was lower in NSCLC compared to normal lung (all p&lt;0.001), and interestingly, was also lower in airways of healthy smokers relative to non-smokers (p&lt;0.001). We next assessed ETS2 immunohistochemical protein expression using tissue microarrays comprised of 342 formalin-fixed paraffin-embedded NSCLC (adenocarcinoma, n=226; SCC, n=116) tissue specimens. There were no statistically significant differences in ETS2 expression by histology, stage or age. We then assessed the association of ETS2 protein expression with clinical outcome. Non-treated all stage (n=206) or stage-I (n=157) patients with relatively lower ETS2 protein expression exhibited significantly shortened disease-free survival compared to patients with higher expression (p=0.008 and p=0.004 of the log-rank test, respectively). In addition, patients with relatively lower ETS2 expression exhibited significantly poorer response to adjuvant therapy compared to patients with higher ETS2 expression (p=0.01). We then probed the effect of modulating ETS2 expression in NSCLC cells. Knockdown of ETS2 expression by RNA interference significantly increased anchorage-dependent colony formation (p=0.004) as well as augmented cellular migration (p=0.01) and invasion through matrigel (p=0.02) compared to cells transfected with control siRNA. Our findings provide evidence that ETS2 may function as a tumor suppressor gene in NSCLC that can aid clinically in identification of aggressive tumors and biologically in increasing our understanding of the pathogenesis of this malignancy (Supported by DoD PROSPECT W81XWH-07-1-0306 and Lung Cancer Research Foundation grants).

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 2177. doi:1538-7445.AM2012-2177

Pulmonary adenocarcinoma: a renewed entity in 2011

Lung cancer, of which non-small-cell lung cancer comprises the majority, is the leading cause of cancer-related deaths in the United States and worldwide. Lung adenocarcinomas are a major subtype of non-small-cell lung cancers, are increasing in incidence globally in both males and females and in smokers and non-smokers, and are the cause for almost 50% of deaths attributable to lung cancer. Lung adenocarcinoma is a tumour with complex biology that we have recently started to understand with the advent of various histological, transcriptomic, genomic and proteomic technologies. However, the histological and molecular pathogenesis of this malignancy is still largely unknown. This review will describe advances in the molecular pathology of lung adenocarcinoma with emphasis on genomics and DNA alterations of this disease. Moreover, the review will discuss recognized lung adenocarcinoma preneoplastic lesions and current concepts of the early pathogenesis and progression of the disease. We will also portray the field cancerization phenomenon and lineage-specific oncogene expression pattern in lung cancer and how both remerging concepts can be exploited to increase our understanding of lung adenocarcinoma pathogenesis for subsequent development of biomarkers for early detection of adenocarcinomas and possibly personalized prevention.

Stage-specific effect of N-(4-hydroxyphenyl)retinamide on cell growth in squamous cell carcinogenesis

Squamous cell carcinoma (SCC) is the most prevalent form of epithelial cancer. SCC results when normal epithelial cells undergo multiple neoplastic changes that culminate in the evolution of an invasive cancer. Retinoids are commonly used as chemopreventive and treatment agents in skin cancer; however, SCC progression is accompanied by a gradual loss of retinoid responsiveness. The synthetic retinoid N-(4-hydroxyphenyl)retinamide (HPR) has shown promising anti-neoplastic activity in a variety of tumor cells, including those that are resistant to all-trans retinoic acid (t-RA). We investigated the effect of HPR on growth and apoptosis of squamous cells at different stages of carcinogenesis. We then determined if retinoic acid receptor (RAR) overexpression affected the outcome of HPR treatment. To model SCC malignant progression, we used a panel of murine keratinocytes representing different stages of squamous cell carcinogenesis. This panel consisted of primary keratinocytes, SP1 and 308 papilloma cell lines, the PAM-212 squamous carcinoma cell line, and the spindle I7 cell line. With the exception of the primary keratinocytes, all cells were unresponsive to t-RA treatment. Pharmacological concentrations of HPR were non-cytotoxic to all keratinocytes tested and HPR sensitivity was stage-dependent, with the papilloma cell lines being the most sensitive, and the spindle cells being the most resistant. Overexpression of RARgamma in SP1 papilloma cells enhanced growth suppression and apoptosis induction by HPR. HPR-induced growth suppression was accompanied by a simultaneous block in the G(1) phase of the cell cycle in RAR-transduced and control SP1 cells and differential regulation of cell cycle and apoptotic mediators.