Molecular, Metabolic, and Subcellular Mapping of the Tumor Immune Microenvironment via 3D Targeted and Non-Targeted Multiplex Multi-Omics Analyses

Most platforms used for the molecular reconstruction of the tumor-immune microenvironment (TIME) of a solid tumor fail to explore the spatial context of the three-dimensional (3D) space of the tumor at a single-cell resolution, and thus lack information about cell-cell or cell-extracellular matrix (ECM) interactions. To address this issue, a pipeline which integrated multiplex spatially resolved multi-omics platforms was developed to identify crosstalk signaling networks among various cell types and the ECM in the 3D TIME of two FFPE (formalin-fixed paraffin embedded) gynecologic tumor samples. These platforms include non-targeted mass spectrometry imaging (glycans, metabolites, and peptides) and Stereo-seq (spatial transcriptomics) and targeted seqIF (IHC proteomics). The spatially resolved imaging data in a two- and three-dimensional space demonstrated various cellular neighborhoods in both samples. The collection of spatially resolved analytes in a voxel (3D pixel) across serial sections of the tissue was also demonstrated. Data collected from this analytical pipeline were used to construct spatial 3D maps with single-cell resolution, which revealed cell identity, activation, and energized status. These maps will provide not only insights into the molecular basis of spatial cell heterogeneity in the TIME, but also novel predictive biomarkers and therapeutic targets, which can improve patient survival rates.

Obesity is associated with improved progression-free survival in Microsatellite-Instability-High endometrial cancer treated with pembrolizumab

OBJECTIVES

To determine the clinical predictors of response rate, progression-free survival (PFS), and overall survival (OS) to pembrolizumab in advanced or recurrent, mismatch repair deficient (MMRd) or Microsatellite Instability-High (MSI-H) endometrial adenocarcinomas.

METHODS

A retrospective, single institution study was conducted among women with recurrent or advanced MMRd or MSI-H endometrial adenocarcinomas treated with single-agent pembrolizumab at our institution from 2017 to 2021. Logistic regression was used for univariable and multivariable analyses. PFS and OS were estimated using the methods of Kaplan and Meier and modeled via Cox proportional hazards regression. Log-rank test was used for intergroup comparisons based on body mass index (BMI).

RESULTS

Among the 44 patients included in the analysis, the median BMI was 32.9 (range 18.5-51.8). Median cycles of pembrolizumab given was 11.5 (range 2-37). Median follow-up was 33 months (range 5-61) with a response rate of 63.6% and stable disease rate of 75%. When stratified by obesity status (BMI≥30), disease control rate was 59.8% in patients with a BMI < 30 and 85.2% in patients with a BMI≥30 patients (p = 0.05). On multivariable analysis, obesity was associated with increased rate of disease control (OR 4.03, 95%CI 1.09, 28) while prior smoking was associated with decreased rate of disease control (OR 0.18, 95%CI 0.03, 0.85). PFS was significantly increased among patients with a BMI≥30 (p = 0.03) but OS was similar (p = 0.5).

CONCLUSION

In this retrospective study, obesity is associated with increased rates of disease control and improved PFS in patients treated with pembrolizumab for recurrent or advanced MMRd/MSI-H endometrial adenocarcinomas.

TIME for Bugs: The Immune Microenvironment and Microbes in Precancer

Major advances in our understanding of the tumor immune microenvironment (TIME) in established cancer have been made, including the influence of host-intrinsic (host genomics) and -extrinsic factors (such as diet and the microbiome) on treatment response. Nonetheless, the immune and microbiome milieu across the spectrum of precancerous tissue and early neoplasia is a growing area of interest. There are emerging data describing the contribution of the immune microenvironment and microbiota on benign and premalignant tissues, with opportunities to target these factors in cancer prevention and interception. Throughout this review, we provide rationale for not only the critical need to further elucidate the premalignant immune microenvironment, but also for the utility of pharmacologic and lifestyle interventions to alter the immune microenvironment of early lesions to reverse carcinogenesis. Novel research methodologies, such as implementing spatial transcriptomics and proteomics, in combination with innovative sampling methods will advance precision targeting of the premalignant immune microenvironment. Additional studies defining the continuum of immune and microbiome evolution, which emerges in parallel with tumor development, will provide novel opportunities for cancer interception at the earliest steps in carcinogenesis.

Abstract P015: Mechanisms of mitochondrial dysfunction in development of mismatch repair-deficient endometrial cancer

Background: Lynch syndrome (LS) is a hereditary cancer syndrome carrying roughly 60% lifetime risk of endometrial cancer (EC) development. LS-EC is caused by mutations in mismatch repair genes (most commonly MSH2), which lead to DNA repair deficiency and hypermutability. Identifying mechanisms that impact cancer development could provide novel opportunities for EC prevention. Our recent studies in Msh2-deficient mice identified mitochondrial dysfunction in EC pathogenesis. The objective of this study is to define the impact of MSH2 loss on mitochondrial function and oxidative DNA damage to identify targets for EC prevention. We hypothesized that MSH2 loss disrupts mitochondrial function and increases oxidative DNA damage in EC cells. Methods: The effects of MSH2 loss on EC pathogenesis were evaluated using our novel mouse model for EC development (PR-Cre+Msh2flox/flox, abbreviated Msh2KO) and primary cell lines derived from this model. Mitochondrial stress tests (MSTs) compared mitochondrial function in murine and human MSH2-deficient and -intact EC cell lines. Western blots compared mitochondrial protein expression between cell lines. Transcriptomic data of human ECs from The Cancer Genome Atlas (TCGA) were probed using cBioPortal. To examine direct effects of MSH2 loss on oxidative stress and mitochondrial function, we performed lentiviral shRNA knockdown (KD) of MSH2 in two human EC cell lines (KLE, Hec1a) and MSH2 overexpression (MSH2++) in MFE280 cells. MSTs and Western blots were utilized as above. Immunofluorescent staining compared oxidative DNA damage in MSH2-KD, MSH2++, and control cell lines after pharmacologically induced oxidative stress via H2O2. RESULTS Transcriptomic signatures of histologically normal endometrium and EC from Msh2KO mice versus control mice reveal mitochondrial dysfunction as a key aberrant pathway. MSTs show reduced baseline and induced mitochondrial function in murine and human MSH2-deficient EC cells compared to MSH2-intact (p&lt;0.0001). Western blots show that MSH2-deficient EC cells exhibit loss of mitochondrial complex II compared to MSH2-intact cells (p&lt;0.05). TCGA data confirm MSH2-deficient human ECs have reduced complex II subunits (p&lt;0.05). Isogenic in vitro studies show MSH2-KD reduces complex II expression yet has variable effects on mitochondrial function. MSH2 overexpression increases complex II expression and mitochondrial function. Oxidative DNA damage did not differ at baseline, but H2O2-induced DNA damage increased after MSH2-KD in one of two cell lines. Conclusions: MSH2 and complex II loss are strongly associated in EC. Further studies on the downstream effects of complex II loss are necessary to determine the contribution to LS-EC development. Complex II loss could result in disruptions to oxidative phosphorylation, the citric acid cycle, metabolic reprogramming, and oncometabolite production. Defining direct effects of MSH2 loss on these potential cancer susceptibility mechanisms will open new avenues for LS-associated EC prevention.

Citation Format: Diana L. Moreno, Mikayla S. Borthwick, Leah Peralta, Wai Kin Chan, Brenda Melendez, Qian Zhang, Nisha Gokul, Melinda S. Yates. Mechanisms of mitochondrial dysfunction in development of mismatch repair-deficient endometrial cancer. [abstract]. In: Proceedings of the AACR Special Conference: Precision Prevention, Early Detection, and Interception of Cancer; 2022 Nov 17-19; Austin, TX. Philadelphia (PA): AACR; Can Prev Res 2023;16(1 Suppl): Abstract nr P015.

Abstract 1248: Predictors of innate resistance to pembrolizumab in patients with microsatellite instability-high endometrial cancer

Introduction: Despite FDA approval of pembrolizumab in microsatellite instability-high (MSI-H)/mismatch repair deficient solid tumors, approximately half of patients with MSI-H endometrial cancer are treatment-refractory. We sought to evaluate pre-treatment MSI-H endometrial tumor samples to examine cell subpopulation differences in the tumor microenvironment (TME) associated with resistance to pembrolizumab.

Methods: Archival tumor samples from MSI-H endometrial cancer patients treated with pembrolizumab at MD Anderson Cancer Center were obtained under an IRB-approved protocol. Twenty-one patients were identified, and pre-treatment archival tumor samples were collected and submitted for RNA-seq and imaging mass cytometry (IMC) with an optimized 38-antibody panel to identify predictive immuno-genomic signatures and cell subpopulations associated with treatment response.

Results: Among the 21 patients treated with pembrolizumab, there were 14 responders and 7 non-responders. Based on transcriptomic signatures, TME heterogeneity was observed. The 14 responders consisted of samples with immunologically “hot” (5/5; 100%), “cold” (6/8; 75%), and “warm” TMEs (3/8; 37.5%) while the 7 non-responders consisted of only “cold” (2/8; 25%) and “warm” (5/8; 62.5%) TME samples. There was an enrichment of fibroblasts and endothelial cell transcriptomic signatures in the samples of the non-responders compared to responders (p=0.018) with a trend of increasing enrichment in those signatures as response strength decreased. IMC performed on archival tissue from 20 patients demonstrated similar trend of higher population of activated fibroblasts (SMA+, MFAP5+) and endothelial cells (CD31+) in non-responders. Furthermore, non-responders had significantly higher total regulatory T cells (CD4+FOXP3+) in the tumor (p=0.027) and stroma (p=0.0282) compared to responders. Additionally, significantly higher activated regulatory T cells (CD4+FOXP3+CD25+) were observed in the tumor (p=0.016) and stroma (p=0.008) of non-responders compared to responders. Similar abundance of total and subpopulations of CD8+ T cells were observed between responders and non-responders.

Conclusion: The MSI-H endometrial TME is heterogeneous. Increased presence of fibroblasts, endothelial cells, and regulatory T-cells in the TME correlate with innate resistance to pembrolizumab. Treatment aimed toward the reduction of these cellular subpopulations may improve sensitivity to PD-1 inhibitors. Future studies are needed to validate these findings.

Citation Format: Jeffrey A. How, Minghao Dang, Sammy Ferri-Borgogno, Elizabeth Euscher, Melinda S. Yates, Weiyi Peng, Shrina D. Patel, Jared J. Burks, Ivo Vletic, Javier Gomez, Karen Lu, Samuel C. Mok, Linghua Wang, Amir A. Jazaeri. Predictors of innate resistance to pembrolizumab in patients with microsatellite instability-high endometrial cancer [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 1248.

Androgen receptor blockade promotes response to BRAF/MEK-targeted therapy

Treatment with therapy targeting BRAF and MEK (BRAF/MEK) has revolutionized care in melanoma and other cancers; however, therapeutic resistance is common and innovative treatment strategies are needed^1,2. Here we studied a group of patients with melanoma who were treated with neoadjuvant BRAF/MEK-targeted therapy ( NCT02231775 , n = 51) and observed significantly higher rates of major pathological response (MPR; ≤10% viable tumour at resection) and improved recurrence-free survival (RFS) in female versus male patients (MPR, 66% versus 14%, P = 0.001; RFS, 64% versus 32% at 2 years, P = 0.021). The findings were validated in several additional cohorts^2-4 of patients with unresectable metastatic melanoma who were treated with BRAF- and/or MEK-targeted therapy (n = 664 patients in total), demonstrating improved progression-free survival and overall survival in female versus male patients in several of these studies. Studies in preclinical models demonstrated significantly impaired anti-tumour activity in male versus female mice after BRAF/MEK-targeted therapy (P = 0.006), with significantly higher expression of the androgen receptor in tumours of male and female BRAF/MEK-treated mice versus the control (P = 0.0006 and P = 0.0025). Pharmacological inhibition of androgen receptor signalling improved responses to BRAF/MEK-targeted therapy in male and female mice (P = 0.018 and P = 0.003), whereas induction of androgen receptor signalling (through testosterone administration) was associated with a significantly impaired response to BRAF/MEK-targeted therapy in male and female patients (P = 0.021 and P < 0.0001). Together, these results have important implications for therapy.

Novel polymer-based system for intrauterine delivery of everolimus for anti-cancer applications

Non-surgical treatment options for low-grade endometrial cancer and precancerous lesions are a critical unmet need for women who wish to preserve fertility or are unable to undergo hysterectomy. The PI3K/AKT/mTOR pathway is frequently activated in endometrial cancers and has been associated with resistance to endocrine therapy, making it a compelling target for early stage disease. Oral everolimus, an inhibitor against mTORC1, has shown clinical benefit in advanced or recurrent disease but has severe adverse effects that may lead to treatment interruption or dose reduction. To overcome this, we developed a polymer-based intrauterine delivery system to achieve persistent, local delivery of everolimus without systemic exposure. In vivo studies, using a rat model, showed that a poly(propylene fumarate)-based rod loaded with everolimus achieved everolimus delivery to the endometrium with levels similar to oral administration, but with limited systemic exposure and up to 84 days of release. Biological activity of everolimus delivered with this system was confirmed, measured by reduced lumen epithelial cell height and PI3K pathway biomarkers. This study shows a promising new delivery approach for anti-cancer drugs for non-surgical treatment of low-grade endometrial cancer.

Endometrial biomarkers in premenopausal women with obesity: an at-risk cohort

BACKGROUND

Obesity is a well-known risk factor for endometrial cancer, but the mechanisms of obesity-related carcinogenesis are not well defined, particularly for premenopausal women. With the continuing obesity epidemic, increases in the incidence of endometrial cancer and a younger age of diagnosis are often attributed to a hyperestrogenic state created by hormone production in adipose tissue, but significant knowledge gaps remain. The balance of estrogen-responsive signals has not been defined in the endometrium of premenopausal women with obesity, where obesity may not create hyperestrogenism in the context of ovaries being the primary source of estrogen production. Obesity is associated with a state of low-grade, chronic inflammation that can promote tumorigenesis, and it is also known that hormonal changes alter the immune microenvironment of the endometrium. However, limited research has been conducted on endometrial immune-response changes in women who have an increased risk for cancer due to obesity.

OBJECTIVE

Endometrial estrogen-regulated biomarkers, previously shown to be dysregulated in endometrial cancer, were evaluated in a cohort of premenopausal women to determine if obesity is associated with differences in the biomarker expression levels, which might reflect an altered risk of developing cancer. The expression of a multiplexed panel of immune-related genes was also evaluated for expression differences related to obesity.

STUDY DESIGN

Premenopausal women with a body mass index of ≥30 kg/m² (n=97) or a body mass index of ≤25 kg/m² (n=33) were prospectively enrolled in this cross-sectional study, which included the assessment of serum metabolic markers and a timed endometrial biopsy for pathologic evaluation, hormone-regulated biomarker analysis, and immune response gene expression analysis. Medical and gynecologic histories were obtained. Endometrial gene expression markers were also compared across the body mass index groups in a previous cohort of premenopausal women with an inherited cancer risk (Lynch syndrome).

RESULTS

In addition to known systemic metabolic differences, histologically normal endometria from women with obesity showed a decrease in gene expression of progesterone receptor (P=.0027) and the estrogen-induced genes retinaldehyde dehydrogenase 2 (P=.008), insulin-like growth factor 1 (P=.016), and survivin (P=.042) when compared with women without obesity. The endometrial biomarkers insulin-like growth factor 1, survivin, and progesterone receptor remained statistically significant in multivariate linear regression models. In contrast, women with obesity and Lynch syndrome had an increased expression of insulin-like growth factor 1 (P=.017). There were no differences in endometrial proliferation, and limited endometrial immune differences were observed.

CONCLUSION

When comparing premenopausal women with and without obesity in the absence of endometrial pathology or an inherited cancer risk, the expression of the endometrial biomarkers does not reflect a local hyperestrogenic environment, but it instead reflects a decreased cancer risk profile that may be indicative of a compensated state. In describing premenopausal endometrial cancer risk, it may be insufficient to attribute a high-risk state to obesity alone; further studies are warranted to evaluate individualized biomarker profiles for differences in the hormone-responsive signals or immune response. In patients with Lynch syndrome, the endometrial biomarker profile suggests that obesity further increases the risk of developing cancer.

Abstract PO049: Compartment-specific profiling for evaluation of disrupted signaling in early stage, low-grade endometrial cancer

Understanding tumor microenvironment is critical to improving conservative management (non-surgical) strategies for early stage, low grade endometrial cancer (EC). This remains an unmet clinical need for women who wish to maintain fertility and those who cannot undergo surgery due to medical co-morbidities. Current regimens rely on progestin treatment, but resistance and early relapse require improved therapeutic strategies. We sought to evaluate alterations in gene expression in the epithelial and stromal compartment of EC compared to normal endometrium to identify targets for combination therapies. RNA was extracted from microdissected epithelial and stromal compartments of formalin fixed paraffin embedded early stage, low grade EC and normal endometrium (NE). Comprehensive transcriptome profiling was performed with Affymetrix Clariom D assay and pathway analysis was performed. Immunohistochemistry (IHC) was used for validation. Functional studies of differentially expressed genes were performed in Hec1A EC cell lines. Among differentially expressed genes in EC vs NE, multiple altered signaling pathways were identified. EIF2 signaling, eIF4 and p70S6K signaling, and PI3K/AKT/mTOR were the most significant pathways activated in both epithelial and stromal compartments. In the epithelia compartment, the most significant gene expression changes included reduced expression of RBPMS (RNA Binding Protein with Multiple Splicing), SORD (Sorbitol Dehydrogenase), DDX17 (DEAD-Box Helicase 17), and TPT1 (Translationally-Controlled Tumor Protein) in EC, while MTDH (Metadherin) was significantly increased in EC. Similar changes were observed in the stroma compartment, but with lower fold changes than that observed in gland. Together with decreased RBPMS expression, decreased RBPMS-interacting molecules IGF2, TCF7L2 (Transcription Factor 7 Like 2), FOS (Proto-Oncogene C-Fos) and increased GPS2 (G protein Pathway Suppressor 2) were also observed. Differential expression of proteins in gland and stroma was also confirmed by IHC. An inverse correlation of RBPMS expression and EC proliferation was also observed in EC at the protein level. Enhanced AKT and S6 protein phosphorylation were observed by RBPMS silencing in Hec1A endometrial cells. Reverse Phase Protein Array demonstrated activation of Caveolin 1, FOXO3 (Forkhead Box O3), MT-CO1 (Mitochondrially Encoded Cytochrome C Oxidase I), L1CAM (L1 Cell Adhesion Molecule) with RBPMS silencing in Hec1A cell. These molecules are involved in pathways such as molecular mechanisms of cancer, estrogen receptor signaling, and senescence pathway. While estrogen-regulated changes were prominent in early stage low-grade EC, the identification of additional signaling changes provide support for an ongoing trial of levonorgestrel IUD + everolimus (mTOR inhibitor) and can be probed further to identify new targets for combination conservative management strategies. Additionally, biomarkers from these pathways, such as RBPMS, can be studied to guide the selection of progestin-only therapy versus combination therapy.

Citation Format: Qian Zhang, Xiaoping Su, Joseph Celestino, Ying Yuan, Samuel C. Mok, Karen H. Lu, Melinda S. Yates. Compartment-specific profiling for evaluation of disrupted signaling in early stage, low-grade endometrial cancer [abstract]. In: Proceedings of the AACR Virtual Special Conference: Endometrial Cancer: New Biology Driving Research and Treatment; 2020 Nov 9-10. Philadelphia (PA): AACR; Clin Cancer Res 2021;27(3_Suppl):Abstract nr PO049.

Abstract 3421: Identifying mechanisms of immune evasion in microsatellite instable endometrial cancers

Inherited or sporadic defects in mismatch repair genes (MLH1, MSH2, MSH6, and PSM2) can lead to microsatellite instable (MSI) tumors, most commonly colon, endometrial or gastric tumors. High mutation rates in MSI tumors have been associated with greater immunogenicity, but these tumors can evade immune response. Recently developed mouse models of MSI endometrial cancer (EC) were used to evaluate immune surveillance mechanisms.

Uterine-targeted MSH2 knockout (PR-Cre+MSH2flox/flox) mice were characterized and determined that 22% of mice develop spontaneous EC by 12-16 months of age. Microsatellite instability was evaluated by PCR. Immune infiltration was quantified by immunohistochemistry (IHC) using FoxP3 (Tregs), CD11b (myeloid cells) and CD8 (tumor infiltrating lymphocytes, TILs) antibodies. Tumors were divided into TILHigh and TILLow (&lt;5 TIL/mm2). Comprehensive transcriptome analysis of tumor and normal controls was performed using the Affymetrix Clariom D assay. A subset of candidate gene changes were validated by RT-PCR and at the protein level by IHC. Cell lines were generated from spontaneous tumors and used for orthotopic syngeneic tumor studies of advanced EC. Immune infiltration in orthotopic tumors was characterized using flow cytometry.

All endometrial tumors from PR-Cre+MSH2flox/flox mice were MSI and included endometrioid, serous, and mixed histologies. Tumors showed varying degrees of immune infiltrate, irrespective of histology. Of 7 tumors, 4 (57%) were TILHigh and 3 (43%) were TILLow. Transcriptome analysis showed TILHigh tumors upregulated innate immunity related pathways including, pattern recognition-associated factors, Type I IFN signaling molecules and CXCL5. Activation of adaptive immunity was observed by an increase in T cell chemoattractants, CXCL9 and CCL21. TILHigh tumors displayed at least a 2-fold increase in MHC class I molecules and CD86 needed for T cell activation. IL1A, CSF1, and TGFB2 (cytokines involved in immunosuppressive cell recruitment and induction) were also highly expressed. IHC confirmed co-localization of TILs with myeloid cells and Tregs in TILHigh tumors. TILLow tumors had decreased expression of several members in the IFN family responsible for initiating innate responses. Primary cell lines from TILHigh and TILLow tumors used in an orthotopic syngeneic mouse model retained the immune profile of the original tumor.

Understanding mechanisms of immune evasion is critical for improving immunotherapy. This model of MSI EC reflects the spectrum of immunogenicity observed in clinical studies. TILHigh tumors express a wide range of factors involved in innate and adaptive anti-tumor responses, while TILLow tumors lack key mediators needed for immune activation. These new models for MSI EC will be essential to test the efficacy of immunotherapies and study mechanisms of resistance.

Citation Format: Brenda Melendez, Emily Hinchcliff, Nisha Gokul, Elizabeth Whitley, Russell R. Broaddus, Rosemarie E. Schmandt, Karen H. Lu, Melinda S. Yates. Identifying mechanisms of immune evasion in microsatellite instable endometrial cancers [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3421.

Abstract NG14: Proteome instability is an immunogenic therapeutic vulnerability in mismatch repair deficient cancer

Deficient DNA mismatch repair (dMMR) induces a hypermutator phenotype, leaving a genomic scar known as microsatellite instability (MSI). MSI is observed in approximately 30% of endometrial cancers, 20% of gastric cancers, 15% of colorectal cancers, and in a smaller fraction of other tumor types. This hypermutator phenotype is thought to produce large numbers of immunogenic neoantigens, leading to the approval of MSI status as a clinical biomarker for immunotherapy. However, more than 60% of patients with MSI tumors fail to respond to immune checkpoint therapy. To uncover alternative therapeutic vulnerabilities for these patients, we used transcriptome signature-guided approaches to identify MLN4924 (pevonedistat), a Nedd8-activating enzyme inhibitor, as a potential therapy for dMMR/MSI cancers. We discover that destabilizing mutations from the dMMR mutation process lead to rampant proteome instability in MSI tumors, resulting in an abundance of misfolded protein aggregates. To compensate, MSI cancer cells activate a Nedd8-mediated degradation pathway to facilitate clearance of misfolded proteins, which is blocked by treatment with MLN4924. The accumulation of misfolded proteins in MSI cancer cells following MLN4924 treatment activated the unfolded protein response, promoted immune cell migration, and induced immunogenic cell death. Antitumor vaccination with MLN4924-treated cells stimulated the generation of endogenous tumor antibodies and prevented tumor incidence upon re-challenge. Based on this immunostimulation, we combined MLN4924 with PD1 blockade, finding that the combination increased recruitment of CD8+ lymphocytes and improved therapeutic efficacy beyond either treatment alone. Taken together, our results indicate that targeting proteome instability is a novel therapeutic avenue for MSI patients and may potentiate immune checkpoint blockade, potentially increasing the depth and duration of response, as well as the fraction of dMMR/MSI patients who can benefit.

Citation Format: Nidhi Sahni, Daniel J. McGrail, Jeannine Garnett, Jun Yin, Hui Dai, David J. H. Shih, Guang Peng, David Menter, Melinda S. Yates, Scott Kopetz, Karen Lu, Russell Broaddus, Gordon B. Mills, Shiaw Y. Lin. Proteome instability is an immunogenic therapeutic vulnerability in mismatch repair deficient cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr NG14.

Improving response to progestin treatment of low-grade endometrial cancer

OBJECTIVES

This review examines how response rates to progestin treatment of low-grade endometrial cancer can be improved. In addition to providing a brief overview of the pathogenesis of low-grade endometrial cancer, we discuss limitations in the current classification of endometrial cancer and how stratification may be refined using molecular markers to reproducibly identify 'low-risk' cancers which may represent the best candidates for progestin therapy. We also discuss constraints in current approaches to progestin treatment of low-grade endometrial cancer and perform a systematic review of predictive biomarkers.

METHODS

PubMed, ClinicalTrials.gov, and Cochrane Library were searched for studies reporting pre-treatment biomarkers associated with outcome in women with low-grade endometrial cancer or endometrial hyperplasia with an intact uterus who received progestin treatment. Studies of fewer than 50 women were excluded. The study protocol was registered in PROSPERO (ID 152374). A descriptive synthesis of pre-treatment predictive biomarkers reported in the included studies was conducted.

RESULTS

Of 1908 records reviewed, 19 studies were included. Clinical features such as age or body mass index cannot predict progestin response. Lesions defined as 'low-risk' by FIGO criteria (stage 1A, grade 1) can respond well; however, the reproducibility and prognostic ability of the current histopathological classification system is suboptimal. Molecular markers can be reproducibly assessed, have been validated as prognostic biomarkers, and may inform patient selection for progestin treatment. DNA polymerase epsilon (POLE)-ultramutated tumors and a subset of p53 wild-type or DNA mismatch repair (MMR)-deficient tumors with 'low-risk' features (eg, progesterone and estrogen receptor-positive) may have improved response rates, though this needs to be validated.

DISCUSSION

Molecular markers can identify cases which may be candidates for progestin treatment. More work is needed to validate these biomarkers and potentially identify new ones. Predictive biomarkers are anticipated to inform future research into progestin treatment of low-grade endometrial cancer and ultimately improve patient outcomes.

Proteome Instability Is a Therapeutic Vulnerability in Mismatch Repair-Deficient Cancer

Deficient DNA mismatch repair (dMMR) induces a hypermutator phenotype that can lead to tumorigenesis; however, the functional impact of the high mutation burden resulting from this phenotype remains poorly explored. Here, we demonstrate that dMMR-induced destabilizing mutations lead to proteome instability in dMMR tumors, resulting in an abundance of misfolded protein aggregates. To compensate, dMMR cells utilize a Nedd8-mediated degradation pathway to facilitate clearance of misfolded proteins. Blockade of this Nedd8 clearance pathway with MLN4924 causes accumulation of misfolded protein aggregates, ultimately inducing immunogenic cell death in dMMR cancer cells. To leverage this immunogenic cell death, we combined MLN4924 treatment with PD1 inhibition and found the combination was synergistic, significantly improving efficacy over either treatment alone.

Everolimus, Letrozole, and Metformin in Women with Advanced or Recurrent Endometrioid Endometrial Cancer: A Multi-Center, Single Arm, Phase II Study

PURPOSE

Treatment for patients with recurrent endometrioid endometrial cancer (EEC) are limited as paclitaxel is the only second-line chemotherapy with a response rate >13%. Targeting PIK3/mTOR in combination with hormonal therapy has shown promise. The addition of metformin may enhance this response. We conducted a phase II study evaluating everolimus, letrozole, and metformin in advanced/recurrent EEC.

PATIENTS AND METHODS

A Simon two-stage design was employed. Women with ≤2 prior chemotherapy regimens for recurrence were eligible. Pretreatment biopsy was required, followed by everolimus 10 mg orally, letrozole 2.5 mg orally, and metformin 500 mg orally twice a day on a 4-week cycle. The primary endpoint was clinical benefit (CB), defined as complete response (CR), partial response (PR), or stable disease (SD) confirmed at 16 weeks. Patients were treated until progression or toxicity.

RESULTS

Sixty-two patients were enrolled. Median age was 62 years (40-77) with 401 cycles completed, median of 6 cycles (1-31). Fifty-four patients were evaluable for response with a CB rate of 50% (27/54). Best overall response (OR) was PR 28% (15/54) and SD 22% (12/54). Thirteen patients received >12 cycles. Median follow-up was 17.9 months (2-47). Median progression-free survival was 5.7 [95% confidence interval (CI), 3.0-8.1] and OS was 19.6 months (95% CI, 14.2-26.3). Positive progesterone receptor expression was associated with CB (89.5% vs. 27.3%, P = 0.001).

CONCLUSIONS

Everolimus, letrozole, and metformin resulted in 50% CB and 28% OR in women with recurrent EEC. Progesterone receptor-positive tumors may have better response; validation studies are needed.See related commentary by Madariaga et al., p. 523.

Ubiquitin Carboxyl-Terminal Hydrolase L1 (UCHL1) Promotes Uterine Serous Cancer Cell Proliferation and Cell Cycle Progression

Uterine serous carcinoma (USC) is the most aggressive form of endometrial cancer, with poor survival rates and high recurrence risk. Therefore, the purpose of this study was to identify therapeutic targets that could aid in the management of USC. By analyzing endometrial cancer samples from The Cancer Genome Atlas (TCGA), we found Ubiquitin Carboxyl-Terminal Hydrolase L1 (UCHL1) to be highly expressed in USC and to correlate with poorer overall survival. UCHL1 silencing reduced cell proliferation in vitro and in vivo, cyclin B1 protein levels and cell cycle progression. Further studies showed that UCHL1 interacts with cyclin B1 and increases cyclin B1 protein stability by deubiquitination. Treatment of USC-bearing mice with the UCHL1-specific inhibitor reduced tumor growth and improved overall survival. Our findings suggest that cyclin B1 is a novel target of UCHL1 and targeting UCHL1 is a potential therapeutic strategy for USC.

Prospective Randomized Biomarker Study of Metformin and Lifestyle Intervention for Prevention in Obese Women at Increased Risk for Endometrial Cancer

Obesity increases risk of endometrial cancer through dysregulation of estrogen and insulin signaling. The primary aim of this study was to evaluate the impact of metformin or lifestyle intervention on endometrial proliferation in postmenopausal obese women. Secondary aims included evaluating obesity-related biomarkers and adverse events experienced. Obese, postmenopausal women with prediabetes were randomized into four groups for a 16-week intervention using a 2 (metformin 1700 mg/day vs. placebo) × 2 (lifestyle intervention vs. no lifestyle intervention) factorial design. Pre- and postintervention endometrial proliferation, anthropometrics, body composition, and serum biomarkers (sex hormones, sex hormone binding globulin, IGF-I, adiponectin, omentin, insulin, glucose, and others) were assessed. Data were analyzed with linear regression models and false-discovery rate correction. Of 576 women approached for the study, 52 attended initial screening, 29 were eligible and randomized, and 26 completed the study. Lifestyle intervention resulted in significant loss of weight (-4.23 kg, P = 0.006) and total fat mass (-3.23 kg, P < 0.001). Participants receiving metformin lost 3.43 kg of weight (P = 0.023), but this was not statistically significant after multiple comparisons adjustment controlling false-discovery rate to 10%. Endometrial proliferation was low at baseline (mean 7.1%) and remained unchanged by 16 weeks, but included substantial variability. Metformin and lifestyle intervention produced minor changes to serum biomarkers. Lifestyle intervention produced the most significant changes in weight and body composition. While it is known that obese postmenopausal women are at increased risk for endometrial cancer, improved biomarkers are needed to stratify risk and test prevention strategies, particularly at the endometrial tissue level. Cancer Prev Res; 11(8); 477-90. ©2018 AACR.

Predicting high-risk endometrioid carcinomas using proteins

Background

The lethality of endometrioid endometrial cancer (EEC) is primarily attributable to advanced-stage diseases. We sought to develop a biomarker model that predicts EEC surgical stage at the time of clinical diagnosis.

Results

PSES was significantly correlated with surgical stage in the TCGA cohort (P < 0.0001) and in the validation cohort (P = 0.0003). Even among grade 1 or 2 tumors, PSES was significantly higher in advanced than in early stage tumors in both the TCGA (P = 0.005) and MD Anderson Cancer Center (MDACC) (P = 0.006) cohorts. Patients with positive PSES score had significantly shorter progression-free survival than those with negative PSES in the TCGA (hazard ratio [HR], 2.033; 95% CI, 1.031 to 3.809; P = 0.04) and validation (HR, 3.306; 95% CI, 1.836 to 9.436; P = 0.0007) cohorts. The ErbB signaling pathway was most significantly enriched in the PSES proteins and downregulated in advanced stage tumors.

Methods

Using reverse-phase protein array expression profiles of 170 antibodies for 210 EEC cases from TCGA, we constructed a Protein Scoring of EEC Staging (PSES) scheme comprising 6 proteins (3 of them phosphorylated) for surgical stage prediction. We validated and evaluated its diagnostic potential in an independent cohort of 184 EEC cases obtained at MDACC using receiver operating characteristic curve analyses. Kaplan-Meier survival analysis was used to examine the association of PSES score with patient outcome, and Ingenuity pathway analysis was used to identify relevant signaling pathways. Two-sided statistical tests were used.

Conclusions

PSES may provide clinically useful prediction of high-risk tumors and offer new insights into tumor biology in EEC.

Bringing Cancer Prevention Research Competencies to the Classroom

The field of cancer prevention incorporates research all along the spectrum from basic science studies at the laboratory bench to epidemiology, behavioral sciences, and clinical studies, with the convergence of evidence from these different approaches aimed at implementing public health interventions that reduce the burden of this disease. Due to the necessity of multiple disciplines interacting in order to achieve a public health outcome, traditional discipline-specific training may not be adequately preparing the cancer prevention research workforce. We propose that cancer prevention researchers establish defined professional competencies which will allow them to shape the future directions of the field as well as to collaborate effectively in multidisciplinary teams, disseminate new findings beyond their own scientific circles, and advocate for their implementation for the public good. We previously proposed that these core competencies focus on knowledge of issues in other research fields, interdisciplinary communication, and leadership/teamwork. Here, we describe the reorganization of an existing course to incorporate activities deliberately designed to foster these competencies. We provide details about the course structure, student feedback, and ideas for future versions of this course. We hope this framework will be useful to others who are engaged in the collective effort to develop leaders in the field of cancer prevention research.

Endometrial Cancers With Activating KRas Mutations Have Activated Estrogen Signaling and Paradoxical Response to MEK Inhibition

OBJECTIVES

The aims of this study were to determine if activating KRas mutation alters estrogen signaling in endometrial cancer (EC) and to explore the potential therapeutic impact of these alterations.

METHODS

The Cancer Genome Atlas was queried for changes in estrogen-regulated genes in EC based on KRas mutation status. In vitro studies were conducted to evaluate estrogen receptor α (ERα) phosphorylation changes and related kinase changes in KRas mutant EC cells. The resulting effect on response to MEK inhibition, using trametinib, was evaluated. Immunohistochemistry was performed on KRas mutant and wild-type EC tumors to test estrogen signaling differences.

RESULTS

KRas mutant tumors in The Cancer Genome Atlas showed decreased progesterone receptor expression (P = 0.047). Protein analysis in KRas mutant EC cells also showed decreased expression of ERα (P < 0.001) and progesterone receptor (P = 0.001). Although total ERα is decreased in KRas mutant cells, phospho-ERα S118 was increased compared with wild type. Treatment with trametinib in KRas mutant cells increased phospho-ERα S167 and increased expression of estrogen-regulated genes. While MEK inhibition blocked estradiol-stimulated phosphorylation of ERK1/2 and p90RSK in wild-type cells, phospho-ERK1/2 and phospho-p90RSK were substantially increased in KRas mutants. KRas mutant EC tumor specimens showed similar changes, with increased phospho-ERα S118 and phospho-ERα S167 compared with wild-type EC tumors.

CONCLUSIONS

MEK inhibition in KRas mutant cells results in activation of ER signaling and prevents the abrogation of signaling through ERK1/2 and p90RSK that is achieved in KRas wild-type EC cells. Combination therapy with MEK inhibition plus antiestrogen therapy may be necessary to improve response rates in patients with KRas mutant EC.

Prospective randomized biomarker study of metformin and lifestyle intervention for prevention in obese postmenopausal women at increased risk for endometrial cancer

1551

Background: Obesity significantly increases risk of endometrial cancer (EC) through systemic metabolic effects and local tissue action, driven by estrogen and dysregulated insulin signaling. EC is most commonly diagnosed in postmenopausal women. Metformin, an antidiabetes drug, and lifestyle intervention were evaluated for effects on endometrial proliferation and serum biomarkers, in parallel with weight loss. Methods: Obese postmenopausal women were randomized into 4 groups for a 16 week intervention using a 2 (metformin 1700 mg/day vs placebo) x 2 (lifestyle intervention vs no lifestyle intervention) factorial design based on the Diabetes Prevention Program. Pre- and post-intervention endometrial biopsies were assessed for proliferation (% Ki67+). Body weight and serum markers were measured pre- and post-intervention (estrone, FSH, DHEA-S, SHBG, IGF-1, adiponectin, omentin, insulin, glucose, A1C, ALT, triglycerides, and others). Results: Of 576 women approached for the study, 29 women were randomized and 26 completed the study. Similar adherence was seen for placebo and metformin, with 88% and 94% of doses taken, respectively. Adverse events were grade 1 or 2, most commonly flatulence, headache, and diarrhea. Metformin+lifestyle group lost the most weight (-7.4%), followed by lifestyle (-5.2%), metformin only (-3.1%), and placebo (+0.1%). Endometrial proliferation was not changed. Overall proliferation was low (7.1% at baseline) with substantial variability even in this postmenopausal cohort. Biopsies produced limited endometrium, precluding evaluation of other tissue markers. Metformin significantly increased serum DHEA (p = 0.002). SHBG increased (p = 0.031) and insulin decreased with lifestyle intervention (p = 0.035) but were not statistically significant after multiple comparisons correction. Conclusions: Metformin and lifestyle intervention produced positive changes in serum markers and weight loss. While it is known that obese postmenopausal women are at increased risk for EC, improved biomarkers are needed to stratify risk and test prevention strategies, particularly at the endometrial tissue level. Clinical trial information: NCT01697566.

Evaluation of BRCA1/2 and homologous recombination defects in ovarian cancer and impact on clinical outcomes

5511

Background: Recent studies show that germline or somatic BRCA1/2 mutations and homologous recombination (HR) defects can be used to predict response to PARP inhibitors in recurrent ovarian cancer. However, the impact of defects in BRCA1/2 and HR genes on overall clinical outcomes are not yet defined for patients undergoing neoadjuvant chemotherapy (NACT) versus upfront surgical debulking (USD). Methods: Previously untreated ovarian cancer patients were prospectively enrolled under approved IRB protocol. Germline and tumor BRCA1/2 mutation testing and methylation were analyzed when sufficient tumor and blood was available. Mutation in 21 additional hereditary cancer genes (including HR genes) was also evaluated. Tumor HR defects were scored on LOH, telomeric allelic imbalance, and large-scale state transitions (as previously described). Presence of germline or somatic BRCA1/2 mutations, BRCA1 methylation, HR score ≥42, or germline mutation in other HR genes were defined together as HRD positive. Results: Of 299 enrolled patients, 129 (43%) received USD and 170 (57%) received NACT. Patients receiving USD had better outcomes compared to NACT, including overall survival (OS, 65.8 vs 45.2 months, p = 0.0003) and event free survival (EFS, 24.8 vs 15.6 months, p < 0.0001). In the overall cohort, EFS was significantly longer for HRD positive patients vs HRD negative (20.5 vs 16.3 months, p = 0.0268). Patients with somatic and germline BRCA1/2 mutations had longer OS vs BRCA1/2 negative (65.3 vs 46.1 months, p = 0.0403). Overall outcomes were worse in NACT compared to USD, but impact of BRCA1/2 mutations and HR defects was stronger in this group. NACT patients with any HR defect had longer EFS (19.7 vs 14.5 months, p = 0.0247). NACT patients with BRCA1/2 germline mutations had longer OS (65.3 vs 38.3 months, p = 0.0230). NACT patients with BRCA1/2 germline mutation had longer EFS (22.6 vs 14.6 months, p = 0.0047). OS and EFS in USD patients were significantly changed based on only debulking status; mutation or HR status did not have a statistically significant effect. Conclusions: While HR defects and BRCA1/2 mutations influence overall outcomes for ovarian cancer patients, the impact is stronger in NACT compared to USD.

Immune Microenvironment in Microsatellite-Instable Endometrial Cancers: Hereditary or Sporadic Origin Matters

Purpose: Recent studies show that colorectal tumors with high microsatellite instability (MSI-H) have increased immunogenicity and response to immunotherapy compared with microsatellite-stable (MSS) tumors. It is not yet clear whether MSI-H endometrial cancer may also benefit from these therapies. It is also unknown whether immune response is equivalent in MSI-H endometrial cancer with sporadic or inherited Lynch syndrome origins.Experimental Design: Multiplexed fluorescent IHC was used to compare matched MSI-H (n = 60) and MSS (n = 96) endometrial cancer specimens by evaluating immune cell populations in tumor and stroma compartments. Sporadic MSI-H and Lynch syndrome-associated (LS) MSI-H endometrial cancers were also directly compared.Results: Increased immune cells were present in stroma of MSI-H endometrial cancer compared with MSS, including granzyme B⁺ cells, activated CTLs (CD8⁺granzyme B⁺), and PD-L1⁺ cells. Granzyme B⁺ cells and activated CTLs were also increased in the tumor compartment of MSI-H endometrial cancers. Comparing sporadic and LS MSI-H endometrial cancer showed distinct differences in immune cell populations, indicating that mechanisms underlying microsatellite instability alter immune response. Specifically, LS MSI-H endometrial cancer showed increased CD8⁺ cells and activated CTLs in stroma, with reduced macrophages in stroma and tumor compared with sporadic MSI-H. Sporadic MSI-H had increased PD-L1⁺ macrophages in stroma and tumor compared with LS MSI-H endometrial cancer.Conclusions: MSI-H endometrial cancer has increased immune cell infiltration compared with MSS endometrial cancer and the hereditary or sporadic origin of microsatellite instability impacts immune response. Clinical trials to determine the role of immunotherapy in patients with MSI-H endometrial cancer must evaluate Lynch syndrome-related and sporadic MSI-H tumors separately. Clin Cancer Res; 23(15); 4473-81. ©2017 AACR.

Lean Body Weight and Metformin Are Insufficient to Prevent Endometrial Hyperplasia in Mice Harboring Inactivating Mutations in PTEN

OBJECTIVES

Obesity is a major risk factor for endometrial cancer. We evaluated whether obesity exacerbates progression of endometrial hyperplasia (EH) using the PRCre/+ PTENflox/+ mouse model and examined if the type 2 diabetes drug, metformin, could prevent EH.

METHODS

Twenty obese (PRCre/+ PTENflox/+) mice were maintained on a high-fat diet, while 20 lean mice ate a matching low-fat diet. Ten mice from each group received metformin (1,000 mg/day) in drinking water. Mice were euthanized at 26 weeks. Uterine tissue was scored for degree of EH. Immunohistochemical staining for Ki67 was used to evaluate cellular proliferation. Markers of PI3K/AKT/mTOR activity were evaluated by immunohistochemistry using activation-specific antibodies. Serum adiponectin was quantified by ELISA.

RESULTS

Obesity had no effect on the extent of EH in (PRCre/+ PTENflox/+) mice. While metformin significantly altered circulating adiponectin levels in obese and lean animals, it had no effect on EH. There were no differences in endometrial proliferation as measured by Ki67 staining. Neither obesity nor metformin altered PI3K/AKT/mTOR activity in these animals.

CONCLUSIONS

Weight and metformin did not affect the severity of EH resulting from PTEN inactivation. Alternative mouse models of early endometrial cancer are required for preclinical cancer prevention studies.

Chemopreventive promise of targeting the Nrf2 pathway

The Kelch ECH associating protein 1-nuclear factor-E2-related factor 2-antioxidant response element (Keap 1-Nrf2-ARE) signaling pathway regulates several protective mechanisms including expression of conjugating and antioxidative genes, antiinflammatory responses, the molecular chaperone/stress response system and the ubiquitin/proteasome system. The Nrf2-mediated response alters susceptibility to carcinogenesis, acute chemical toxicity, oxidative stress, asthma, acute inflammation, septic shock and neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease. Studies using natural and synthetic chemical inducers that activate Nrf2 signaling have demonstrated protective efficacy in many animal models of disease. Conversely, studies in Nrf2-disrupted mice indicate they exhibit increased sensitivity to many of these diseases. Thus, activation of Keap1-Nrf2-ARE signaling constitutes a broad protective response, making Nrf2 and its interacting partners important targets for chemoprevention. However, additional studies are needed to characterize Keap1-Nrf2-ARE signaling in humans to further develop exceptionally potent activators of the pathway and further understand the potential consequences of altering this system.

Phase II study of everolimus and letrozole in patients with recurrent endometrial carcinoma

PURPOSE

The phosphoinositol-3 kinase (PI3K) pathway is frequently dysregulated in endometrial cancer (EC). Hormonal manipulation leads to response in some patients with EC, but resistance derived from PI3K pathway activation has been documented. Targeting mammalian target of rapamycin (mTOR) may overcome endocrine resistance. We conducted a two-institution phase II trial of everolimus and letrozole in women with recurrent EC.

PATIENTS AND METHODS

Patients were considered incurable, had measurable disease, and were treated with up to two prior cytotoxic regimens. Everolimus was administered orally at 10 mg daily and letrozole was administered orally at 2.5 mg daily. Each cycle consisted of 4 weeks of therapy. Patients were treated until progression, toxicity, or complete response (CR). The primary end point was the clinical benefit rate (CBR), which was defined as CR, partial response, or stable disease (≥ 16 weeks) by RECIST 1.0 criteria. Translational studies were performed to correlate biomarkers with response.

RESULTS

Thirty-eight patients were enrolled (median age, 62 years; range, 24 to 82 years). Thirty-five patients were evaluable for response. The CBR was 40% (14 of 35 patients); the median number of cycles among responders was 15 (range, seven to 29 cycles). The confirmed objective response rate (RR) was 32% (11 of 35 patients; nine CRs and two partial responses; median, 15 cycles; range, eight to 29 cycles). Twenty percent of patients (seven of 35 patients) were taken off treatment after a prolonged CR and at the discretion of the treating clinician. None of the patients discontinued treatment as a result of toxicity. Serous histology was the best predictor of lack of response. Patients with endometrioid histology and CTNNB1 mutations responded well to everolimus and letrozole.

CONCLUSION

Everolimus plus letrozole results in a high CBR and RR in patients with recurrent EC. Further development of this combination in recurrent endometrioid EC is under way.

Salpingectomy as a means to reduce ovarian cancer risk

Bilateral salpingo-oophorectomy (BSO) has become the standard-of-care for risk reduction in women at hereditary risk of ovarian cancer. Although this procedure significantly decreases both the incidence of and mortality from ovarian cancer, it affects quality of life, and the premature cessation of ovarian function may have long-term health hazards. Recent advances in our understanding of the molecular pathways of ovarian cancer point to the fallopian tube epithelium as the origin of most high-grade serous cancers (HGSC). This evolving appreciation of the role of the fallopian tube in HGSC has led to the consideration of salpingectomy alone as an option for risk management, especially in premenopausal women. In addition, it is postulated that bilateral salpingectomy with ovarian retention (BSOR), may have a public health benefit for women undergoing benign gynecologic surgery. In this review, we provide the rationale for salpingectomy as an ovarian cancer risk reduction strategy.

CGRRF1 as a novel biomarker of tissue response to metformin in the context of obesity

OBJECTIVE

Obesity-associated hyperestrogenism and hyperinsulinemia contribute significantly to the pathogenesis of endometrial cancer. We recently demonstrated that metformin, a drug long used for treatment of type 2 diabetes, attenuates both insulin- and estrogen-mediated proliferative signaling in the obese rat endometrium. In this study, we sought to identify tissue biomarkers that may prove clinically useful to predict tissue response for both prevention and therapeutic studies. We identified CGRRF1 (cell growth regulator with ring finger domain 1) as a novel metformin-responsive gene and characterized its possible role in endometrial cancer prevention.

METHODS

CGRRF1 mRNA expression was evaluated by RT-qPCR in the endometrium of obese and lean rats, and also in normal and malignant human endometrium. CGRRF1 levels were genetically manipulated in endometrial cancer cells, and its effects on proliferation and apoptosis were evaluated by MTT and Western blot.

RESULTS

CGRRF1 is significantly induced by metformin treatment in the obese rat endometrium. In vitro studies demonstrate that overexpression of CGRRF1 inhibits endometrial cancer cell proliferation. Analysis of human endometrial tumors reveals that CGRRF1 expression is significantly lower in hyperplasia, Grade 1, Grade 2, Grade 3, MMMT, and UPSC endometrial tumors compared to normal human endometrium (p<0.05), suggesting that loss of CGRRF1 is associated with the presence of disease.

CONCLUSION

CGRRF1 represents a novel, reproducible tissue marker of metformin response in the obese endometrium. Furthermore, our preliminary data suggests that up-regulation of CGRRF1 expression may prove clinically useful in the prevention or treatment of endometrial cancer.

Another surprise from Metformin: novel mechanism of action via K-Ras influences endometrial cancer response to therapy

Metformin is an oral biguanide commonly used for the treatment of type II diabetes and has recently been demonstrated to possess antiproliferative properties that can be exploited for the prevention and treatment of a variety of cancers. The mechanisms underlying this effect have not been fully elucidated. Using both in vitro and in vivo models, we examined the effects of metformin on endometrial tumors with defined aberrations in the PI3K/PTEN/mTOR and MAPK signaling pathways to understand metformin mechanism of action and identify clinically useful predictors of response to this agent. In vitro assays of proliferation, cytotoxicity, and apoptosis were used to quantify the effects of metformin on endometrial cancer cell lines with mutations in the PI3K/PTEN/mTOR and MAPK signaling pathways. The in vivo effects of oral metformin on tumor progression were further examined using xenograft mouse models of endometrial cancer. K-Ras localization was analyzed by confocal microscopy using GFP-labeled oncogenic K-Ras and by immunoblot following subcellular fractionation. Metformin inhibited cell proliferation, induced apoptosis, and decreased tumor growth in preclinical endometrial cancer models, with the greatest response observed in cells harboring activating mutations in K-Ras. Furthermore, metformin displaces constitutively active K-Ras from the cell membrane, causing uncoupling of the MAPK signaling pathway. These studies provide a rationale for clinical trials using metformin in combination with PI3K-targeted agents for tumors harboring activating K-Ras mutations, and reveal a novel mechanism of action for metformin.

Chemopreventive effects of metformin on obesity-associated endometrial proliferation

OBJECTIVE

Obesity is a significant contributing factor to endometrial cancer risk. We previously demonstrated that estrogen-induced endometrial proliferation is enhanced in the context of hyperinsulinemia and insulin resistance. In this study, we investigate whether pharmacologic agents that modulate insulin sensitivity or normalize insulin levels will diminish the proliferative response to estrogen.

STUDY DESIGN

Zucker fa/fa obese rats and lean controls were used as models of hyperinsulinemia and insulin resistance. Insulin levels were depleted in ovariectomized rats following treatment with streptozotocin, or modulated by metformin treatment. The number of BrdU-incorporated cells, estrogen-dependent proliferative and antiproliferative gene expression, and activation of mTOR and ERK1/2 MAPK signaling were studied. A rat normal endometrial cell line RENE1 was used to evaluate the direct effects of metformin on endometrial cell proliferation and gene expression in vitro.

RESULTS

Streptozotocin lowered circulating insulin levels in obese rats and decreased the number of BrdU-labeled endometrial cells even in the presence of exogenous estrogen. Treatment with the insulin-sensitizing drug metformin attenuated estrogen-dependent proliferative expression of c-myc and c-fos in the obese rat endometrium compared to untreated controls and was accompanied by inhibition of phosphorylation of the insulin and IGF1 receptors (IRβ/IGF1R) and ERK1/2. In vitro studies indicated metformin inhibited RENE1 proliferation in a dose-dependent manner.

CONCLUSION

These findings suggest that drugs that modulate insulin sensitivity, such as metformin, hinder estrogen-mediated endometrial proliferation. Therefore, these drugs may be clinically useful for the prevention of endometrial cancer in obese women.

Molecular pathogenesis of endometrial cancers in patients with Lynch syndrome

BACKGROUND

The authors hypothesized that Lynch syndrome (LS)-associated endometrial cancer (EC) develops from morphologically normal endometrium that accumulates enough molecular changes to progress through a continuum of hyperplasia to carcinoma, similar to sporadic EC. The primary objective of the current study was to determine whether LS-associated EC involves progression through a preinvasive lesion. The secondary objective was to identify molecular changes that contribute to endometrial carcinogenesis in patients with LS.

METHODS

Women with a confirmed mismatch repair gene mutation for LS who were undergoing a prophylactic or therapeutic hysterectomy were eligible. Cases and controls were matched for EC and hyperplasia based preferentially on age and histology. Mutation status of phosphatidylinositol 3-kinase (PIK3CA); KRAS; AKT; LKB1; catenin (cadherin-associated protein), beta 1, 88kDa (CTNNB1); and phosphatase and tensin homolog (PTEN) protein loss was assessed.

RESULTS

Concurrent complex atypical hyperplasia (CAH) was found in EC in 11 cases of LS (39.3%) and 21 sporadic cases (46.6%). Loss of PTEN expression was common in both sporadic (69%) and LS-associated EC (86.2%). There was no significant difference noted with regard to the frequency of KRAS mutations in cases of sporadic EC (10.3%) compared with LS-associated EC (3.4%). AKT and LKB1 mutations were rarely observed. Mutations in PIK3CA and CTNNB1 occurred more frequently in cases of sporadic EC compared with LS-associated EC.

CONCLUSIONS

Hyperplasia, particularly CAH, is part of the preinvasive spectrum of disease in LS-associated EC, as indicated by the presence of complex hyperplasia and CAH in cases of LS. Although loss of PTEN is common in both LS and sporadic EC cases, there was a lack of additional mutations in LS-associated EC cases. This suggests that in the context of the mismatch repair defects in LS, fewer additional molecular changes are required to progress from preinvasive lesions to cancer.

Prospective multicenter randomized intermediate biomarker study of oral contraceptive versus depo-provera for prevention of endometrial cancer in women with Lynch syndrome

Women with Lynch syndrome have a 40% to 60% lifetime risk for developing endometrial cancer, a cancer associated with estrogen imbalance. The molecular basis for endometrial-specific tumorigenesis is unclear. Progestins inhibit estrogen-driven proliferation, and epidemiologic studies have shown that progestin-containing oral contraceptives (OCP) reduce the risk of endometrial cancer by 50% in women at general population risk. It is unknown whether they are effective in women with Lynch syndrome. Asymptomatic women ages 25 to 50 with Lynch syndrome were randomized to receive the progestin compounds Depo-Provera (depo-MPA) or OCP for three months. An endometrial biopsy and transvaginal ultrasound were conducted before and after treatment. Endometrial proliferation was evaluated as the primary endpoint. Histology and a panel of surrogate endpoint biomarkers were evaluated for each endometrial biopsy as secondary endpoints. A total of 51 women were enrolled, and 46 completed treatment. Two of the 51 women had complex hyperplasia with atypia at the baseline endometrial biopsy and were excluded from the study. Overall, both depo-MPA and OCP induced a dramatic decrease in endometrial epithelial proliferation and microscopic changes in the endometrium characteristic of progestin action. Transvaginal ultrasound measurement of endometrial stripe was not a useful measure of endometrial response or baseline hyperplasia. These results show that women with Lynch syndrome do show an endometrial response to short-term exogenous progestins, suggesting that OCP and depo-MPA may be reasonable chemopreventive agents in this high-risk patient population.

Microscopic and early-stage ovarian cancers in BRCA1/2 mutation carriers: building a model for early BRCA-associated tumorigenesis

Risk-reducing salpingo-oophorectomy (RRSO) is the cornerstone of ovarian cancer prevention in BRCA1/2 mutation carriers. Occult fallopian tube and ovarian cancers have been reported in a small percentage of BRCA1/2 mutation carriers undergoing RRSO. Here, we review our single-institution experience with RRSO in BRCA1/2 mutation carriers to characterize cases of microscopic cancers in these patients. At the time of RRSO, 7.9% of BRCA1 mutation carriers were diagnosed with microscopic fallopian tube or ovarian cancers and no cases were diagnosed in BRCA2 mutation carriers. The majority of the microscopic cancers include cases that were confined to the fallopian tubes, although there were also cases involving ovaries only or peritoneal washings only. This suggests that the site of origin may be in the ovary, fallopian tube, or peritoneum for BRCA-associated serous cancers. However, an analysis of early-stage (stages I and II) ovarian and fallopian tube cancers diagnosed in BRCA1/2 mutation carriers confirms that the ovary is a preferred site for tumor growth with 11 of 14 early-stage cancers having a dominant ovarian mass. Overall, these data suggest that cancer initiation may occur in the ovary, fallopian tube, or peritoneum, but tumor growth and progression are favored in the ovary. We present an updated model for BRCA1/2 mutation-associated ovarian and fallopian tube carcinogenesis, which may aid in identifying improved prevention strategies for high-risk women who delay or decline RRSO.

Abstract 3132: Proliferative effects of FGF1 on ovarian cancer cells correlate with FGFR4 over expression and are mediated by MAPK/ERK signaling

Objectives: To identify the effect of FGF1 on cell proliferation in ovarian cancer and endothelial cells, its relation to FGFR4 over expression and signaling pathways involved

Methods: Amplification of FGFR4 on 5q31-35, which was previously shown to be associated with poor survival in patients with advanced stage high-grade serous ovarian cancer (HGSC), was validated by quantitative PCR in 52 HGSC. Association between DNA copy numbers of FGFR4 and FGF1 located on the same segment was performed by Spearman correlation analysis. Over expression of FGFR4 protein was confirmed in ovarian cancer cell lines and tissue by western blot analysis and immunohistochemistry, respectively. Endogenous FGF1 production by several ovarian cancer cell lines in conditioned medium was quantified using ELISA. Effect of exogenous FGF1 on cell proliferation of high and low-FGFR4 expressing ovarian cancer cell lines and an immortalized microvascular endothelial cell line was determined by WST-1 assay. Signaling pathways activation was screened by treating ovarian cancer cell lines and endothelial cells transduced with six different transcription response elements using the Cignal-Lenti reporter system with exogenous FGF1.

Results: FGFR4 was amplified and over-expressed in a majority of ovarian cancer cell lines and tumor tissue and FGFR4 DNA copy number was significantly correlated with that of FGF1 (r=0.4, p=0.04). Endogenous FGF1 production was detected by ELISA in 2 of 5 screened ovarian cell lines. FGF1 significantly induced cell proliferation in high FGFR4 expressing ovarian cancer cells (20%, p&lt;0.001) and in endothelial cells (15%, p&lt;0.001); but not in low FGFR4 expressers. Significant activation of MAPK/ERK signal transduction pathways was noted after treatment of ovarian(1.43 fold, P &lt; 0.001) and endothelial(1.33 fold, P &lt; 0.001) cell lines transduced with the Cignal-Lenti reporter system.

Conclusions: Our report provides preliminary evidence that poor survival associated with FGF1 amplification and over expression appears to be mediated through FGFR4, which is also amplified and over-expressed in ovarian cancer cell. In addition, FGF1 produced by ovarian cancer cells may exert both autocrine and paracrine effect on cancer cells and endothelial cells through the activation of MAPK/ERK pathway. These data suggests that new regimens targeting FGF1, FGFR4 and downstream signaling pathways may improve ovarian cancer patient survival.

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 3132.

The monkey, the hen, and the mouse: models to advance ovarian cancer chemoprevention

This perspective on Romero et al. (beginning on p. 792 in this issue of the journal) discusses the available animal models of ovarian cancer, including the laying hen, non-human primate, and transgenic rodent models, and their relevance to ovarian cancer chemoprevention studies.

The triterpenoid CDDO-imidazolide confers potent protection against hyperoxic acute lung injury in mice

RATIONALE

Oxygen supplementation (e.g., hyperoxia) is used to support critically ill patients with noninfectious and infectious acute lung injury (ALI); however, hyperoxia exposure can potentially further contribute to and/or perpetuate preexisting ALI. Thus, developing novel therapeutic agents to minimize the side effects of hyperoxia is essential to improve the health of patients with severe ALI and respiratory dysfunction. We have previously shown that mice with a genetic disruption of the Nrf2 transcription factor, which squelches cellular stress by up-regulating the induction of several antioxidant enzymes and proteins, have greater susceptibility to hyperoxic lung injury. Moreover, we have recently demonstrated that Nrf2-deficiency impairs the resolution of lung injury and inflammation after nonlethal hyperoxia exposure.

OBJECTIVES

To test the hypothesis that amplification of endogenous Nrf2 activity would prevent or dampen ALI induced by hyperoxia.

METHODS

Here, we tested our hypothesis using a synthetic triterpenoid compound CDDO-imidazole (CDDO-Im) (1-[2-cyano-3-,12-dioxooleana-1,9(11)-dien-28-oyl] imidazole) in Nrf2-sufficient and Nrf2-deficient mice subjected to hyperoxia-induced ALI.

MEASUREMENTS AND MAIN RESULTS

We demonstrate that oral administration of CDDO-Im at a dose of 30 micromol/kg body weight during the hyperoxic exposure is sufficient to markedly attenuate hyperoxia-induced ALI in Nrf2-sufficient but not Nrf2-deficient mice. This protection by the CDDO-Im against hyperoxic insult was accompanied by increased levels of Nrf2-regulated cytoprotective gene expression and reduced levels of DNA damage in the lung.

CONCLUSIONS

These results suggest that up-regulation of Nrf2 signaling by CDDO-Im or its analogs may provide a novel therapeutic strategy to minimize the adverse effects of hyperoxia.

Genetic versus chemoprotective activation of Nrf2 signaling: overlapping yet distinct gene expression profiles between Keap1 knockout and triterpenoid-treated mice

Loss of NF-E2-related factor 2 (Nrf2) signaling increases susceptibility to acute toxicity, inflammation and carcinogenesis in mice due to the inability to mount adaptive responses. In contrast, disruption of Keap1 (a cytoplasmic modifier of Nrf2 turnover) protects against these stresses in mice, although inactivating mutations in Keap1 have been identified recently in some human cancers. Global characterization of Nrf2 activation is important to exploit this pathway for chemoprevention in healthy, yet at-risk individuals and also to elucidate the consequences of hijacking the pathway in Keap1-mutant human cancers. Liver-targeted conditional Keap1-null, Albumin-Cre:Keap1((flox/-)) (CKO) mice provide a model of genetic activation of Nrf2 signaling. By coupling global gene expression analysis of CKO mice with analysis of pharmacologic activation using the synthetic oleanane triterpenoid 1-[2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oyl]imidazole (CDDO-Im), we are able to gain insight into pathways affected by Nrf2 activation. CDDO-Im is an extremely potent activator of Nrf2 signaling. CKO mice were used to identify genes modulated by genetic activation of Nrf2 signaling. The CKO response was compared with hepatic global gene expression changes in wild-type mice treated with CDDO-Im at a maximal Nrf2 activating dose. The results show that genetic and pharmacologic activation of Nrf2 signaling modulates pathways beyond detoxication and cytoprotection, with the largest cluster of genes associated with lipid metabolism. Genetic activation of Nrf2 results in much larger numbers of detoxication and lipid metabolism gene changes. Additionally, analysis of pharmacologic activation suggests that Nrf2 is the primary mediator of CDDO-Im activity, though other cell-signaling targets are also modulated following an oral dose of 30 micromol/kg.

Targeting Nrf2 with the triterpenoid CDDO-imidazolide attenuates cigarette smoke-induced emphysema and cardiac dysfunction in mice

Chronic obstructive pulmonary disease (COPD), which comprises emphysema and chronic bronchitis resulting from prolonged exposure to cigarette smoke (CS), is a major public health burden with no effective treatment. Emphysema is also associated with pulmonary hypertension, which can progress to right ventricular failure, an important cause of morbidity and mortality among patients with COPD. Nuclear erythroid 2 p45 related factor-2 (Nrf2) is a redox-sensitive transcription factor that up-regulates a battery of antioxidative genes and cytoprotective enzymes that constitute the defense against oxidative stress. Recently, it has been shown that patients with advanced COPD have a decline in expression of the Nrf2 pathway in lungs, suggesting that loss of this antioxidative protective response is a key factor in the pathophysiological progression of emphysema. Furthermore, genetic disruption of Nrf2 in mice causes early-onset and severe emphysema. The present study evaluated whether the strategy of activation of Nrf2 and its downstream network of cytoprotective genes with a small molecule would attenuate CS-induced oxidative stress and emphysema. Nrf2(+/+) and Nrf2(-/-) mice were fed a diet containing the potent Nrf2 activator, 1-[2-cyano-3-,12-dioxooleana-1,9(11)-dien-28-oyl]imidazole (CDDO-Im), while being exposed to CS for 6 months. CDDO-Im significantly reduced lung oxidative stress, alveolar cell apoptosis, alveolar destruction, and pulmonary hypertension in Nrf2(+/+) mice caused by chronic exposure to CS. This protection from CS-induced emphysema depended on Nrf2, as Nrf2(-/-) mice failed to show significant reduction in alveolar cell apoptosis and alveolar destruction after treatment with CDDO-Im. These results suggest that targeting the Nrf2 pathway during the etiopathogenesis of emphysema may represent an important approach for prophylaxis against COPD.

A novel acetylenic tricyclic bis-(cyano enone) potently induces phase 2 cytoprotective pathways and blocks liver carcinogenesis induced by aflatoxin

A novel acetylenic tricyclic bis-(cyano enone), TBE-31, is a lead compound in a series of tricyclic compounds with enone functionalities in rings A and C. Nanomolar concentrations of this potent multifunctional molecule suppress the induction of the inflammatory protein, inducible nitric oxide synthase, activate phase 2 cytoprotective enzymes in vitro and in vivo, block cell proliferation, and induce differentiation and apoptosis of leukemia cells. Oral administration of TBE-31 also significantly reduces formation of aflatoxin-DNA adducts and decreases size and number of aflatoxin-induced preneoplastic hepatic lesions in rats by >90%. Because of the two cyano enones in rings A and C, TBE-31 may directly interact with DTT and protein targets such as Keap1 that contain reactive cysteine residues. The above findings suggest that TBE-31 should also be tested for chemoprevention and chemotherapy in relevant models of cancer and against other chronic, degenerative diseases in which inflammation and oxidative stress contribute to disease pathogenesis.

Genetic or pharmacologic amplification of nrf2 signaling inhibits acute inflammatory liver injury in mice

Oxidative stress-mediated destruction of normal parenchymal cells during hepatic inflammatory responses contributes to the pathogenesis of immune-mediated hepatitis and is implicated in the progression of acute inflammatory liver injury to chronic inflammatory liver disease. The transcription factor NF-E2-related factor 2 (Nrf2) regulates the expression of a battery of antioxidative enzymes and Nrf2 signaling can be activated by small-molecule drugs that disrupt Keap1-mediated repression of Nrf2 signaling. Therefore, genetic and pharmacologic approaches were used to activate Nrf2 signaling to assess protection against inflammatory liver injury. Profound increases in indicators of cell death were observed in both Nrf2 wild-type (Nrf2-WT) mice and Nrf2-disrupted (Nrf2-KO) mice 24 h following intravenous injection of concanavalin A (12.5 mg/kg, ConA), a model for T cell-mediated acute inflammatory liver injury. However, hepatocyte-specific conditional Keap1 null (Alb-Cre:Keap1(flox/-), cKeap1-KO) mice with constitutively enhanced expression of Nrf2-regulated antioxidative genes as well as Nrf2-WT mice but not Nrf2-KO mice pretreated with three daily doses of a triterpenoid that potently activates Nrf2 (30 mumol/kg, cyano-3,12-dioxooleana-1,9(11)-dien-28-oyl-imidazolide [CDDO-Im]) were highly resistant to ConA-mediated inflammatory liver injury. CDDO-Im pretreatment of both Nrf2-WT and Nrf2-KO mice resulted in equivalent suppression of serum proinflammatory soluble proteins suggesting that the hepatoprotection afforded by CDDO-Im pretreatment of Nrf2-WT mice but not Nrf2-KO mice was not due to suppression of systemic proinflammatory signaling, but instead was due to activation of Nrf2 signaling in the liver. Enhanced hepatic expression of Nrf2-regulated antioxidative genes inhibited inflammation-mediated oxidative stress, thereby preventing hepatocyte necrosis. Attenuation of hepatocyte death in cKeap1-KO mice and CDDO-Im pretreated Nrf2-WT mice resulted in decreased late-phase proinflammatory gene expression in the liver thereby diminishing the sustained influx of inflammatory cells initially stimulated by the ConA challenge. Taken together, these results clearly illustrate that targeted cytoprotection of hepatocytes through Nrf2 signaling during inflammation prevents the amplification of inflammatory responses in the liver.

Pharmacodynamic characterization of chemopreventive triterpenoids as exceptionally potent inducers of Nrf2-regulated genes

Synthetic triterpenoids have been developed, which are potent inducers of cytoprotective enzymes and inhibitors of inflammation, greatly improving on the weak activity of naturally occurring triterpenoids. An imidazolide triterpenoid derivative, 1-[2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oyl]imidazole (CDDO-Im or TP235), has been previously shown to potently protect against hepatic tumorigenesis, acting in part by inducing cytoprotective genes through Keap1-Nrf2-antioxidant response element (ARE) signaling. In these studies, the pharmacodynamic activity of CDDO-Im is characterized in two distinct lines of ARE reporter mice and by measuring increases in Nqo1 transcript levels as a marker of cytoprotective gene induction. Oral administration of CDDO-Im induces ARE-regulated cytoprotective genes in many tissues in the mouse, including liver, lung, kidney, intestines, brain, heart, thymus, and salivary gland. CDDO-Im induces Nqo1 RNA transcripts in some organs at doses as low as 0.3 mumol/kg body weight (orally). A structure activity evaluation of 15 additional triterpenoids (a) confirmed the importance of Michael acceptor groups on both the A and C rings, (b) showed the requirement for a nitrile group at C-2 of the A ring, and (c) indicated that substituents at C-17 dramatically affected pharmacodynamic action in vivo. In addition to CDDO-Im, other triterpenoids, particularly the methyl ester CDDO-Me (TP155) and the dinitrile TP225, are extremely potent inducers of cytoprotective genes in mouse liver, lung, small intestine mucosa, and cerebral cortex. This pharmacodynamic characterization highlights the chemopreventive promise of several synthetic triterpenoids in multiple target organs.

Potent protection against aflatoxin-induced tumorigenesis through induction of Nrf2-regulated pathways by the triterpenoid 1-[2-cyano-3-,12-dioxooleana-1,9(11)-dien-28-oyl]imidazole

Synthetic triterpenoid analogues of oleanolic acid are potent inducers of the phase 2 response as well as inhibitors of inflammation. We show that the triterpenoid, 1-[2-cyano-3-,12-dioxooleana-1,9(11)-dien-28-oyl]imidazole (CDDO-Im), is a highly potent chemopreventive agent that inhibits aflatoxin-induced tumorigenesis in rat liver. The chemopreventive potency of CDDO-Im was evaluated by measuring inhibition of formation of putative preneoplastic lesions (glutathione S-transferase P positive foci) in the liver of rats exposed to aflatoxin B1. CDDO-Im produces an 85% reduction in the hepatic focal burden of preneoplastic lesions at 1 micromol/kg body weight and a >99% reduction at 100 micromol/kg body weight. CDDO-Im treatment reduces levels of aflatoxin-DNA adducts by approximately 40% to 90% over the range of 1 to 100 micromol/kg body weight. Additionally, changes in mRNA levels of genes involved in aflatoxin metabolism were measured in rat liver following a single dose of CDDO-Im. GSTA2, GSTA5, AFAR, and EPHX1 transcripts are elevated 6 hours following a 1 micromol/kg body weight dose of CDDO-Im. Microarray analysis using wild-type and Nrf2 knockout mice confirms that many phase 2 and antioxidant genes are induced in an Nrf2-dependent manner in mouse liver following treatment with CDDO-Im. Thus, low-micromole doses of CDDO-Im induce cytoprotective genes, inhibit DNA adduct formation, and dramatically block hepatic tumorigenesis. As a point of reference, oltipraz, an established modulator of aflatoxin metabolism in humans, is 100-fold weaker than CDDO-Im in this rat antitumorigenesis model. The unparalleled potency of CDDO-Im in vivo highlights the chemopreventive promise of targeting Nrf2 pathways with triterpenoids.

Immunolocalisation of adenosine A(1) receptors in the rat kidney

The location of adenosine A(1) receptors in the rat kidney was investigated using immunolabelling with antibodies raised to a 15-amino-acid sequence near the C-terminus of the receptor (antibody I) and to a 14-amino-acid sequence in the second extracellular loop (antibody II). In the cortex, antibody I bound to adenosine A(1) receptors in mesangial cells and afferent arterioles, whilst antibody II bound to receptors in proximal convoluted tubules. In the medulla, both antibodies bound to receptors in collecting ducts and the papillary surface epithelium. These observations provide support for the diverse functional roles previously proposed for the adenosine A(1) receptor in the kidney. The labelling of distinct but different structures in the cortex by antibodies raised to different amino acid sequences on the A(1) receptor protein suggests that differing forms of the receptor are present in this region of the kidney.

Differential expression of renal adenosine A(1) receptors induced by acute renal failure

The distribution of renal adenosine A(1) receptors was investigated in rats with glycerol- or mercuric chloride (HgCl(2))-induced acute renal failure. Receptors were localised by autoradiography using [(3)H]8-cyclopentyl-1,3-dipropylxanthine ([(3)H]DPCPX), a selective A(1) adenosine receptor antagonist. In saline-injected control animals, significant labelling with [(3)H]DPCPX was detected in glomeruli, the inner stripe of outer medulla, and the inner medulla. Sixteen hours following induction of glycerol-induced acute renal failure (ARF), a 34% increase in labelling in glomeruli was noted compared to saline-injected controls, and by 48 hr, glomerular labelling had increased by 200%. In addition, 48 hr following glycerol injection, significant labelling was now detected in the cortical labyrinth and medullary rays whilst, in the inner medulla, labelling had decreased by 34%. By contrast to glycerol-induced ARF, the only significant change noted 48 hr following induction of HgCl(2)-induced ARF was a 39% decrease in labelling in the inner medulla. It is concluded that glycerol-induced ARF results in differential expression of renal adenosine A(1) receptors with increased expression in the cortex and reduced expression in the inner medulla. Increased density of A(1) receptors in glomeruli may account, at least in part, for the increased renal vasoconstrictor response to adenosine and depressed glomerular filtration rate noted previously in this type of acute renal failure.

Effects of adenosine receptor antagonists on the responses to contrast media in the isolated rat kidney

Contrast media can induce both a decrease in renal blood flow and a reduction in glomerular filtration rate (GFR) when administered to both experimental animals and humans. In the present study we have examined the role of adenosine in mediating these effects using the isolated perfused rat kidney. Kidneys were perfused with a 6. 7%-(w/v)-albumin-based perfusate supplemented with glucose and amino acids (n=6 per group). They were exposed to diatrizoate [20 mg of iodine (mgI)/ml; osmolality 1650 mOsm/kg of water] or iotrolan (20 mgI/ml; osmolality 320 mOsm/kg of water) in the presence or absence of theophylline (10.8 microg/ml), or to diatrizoate in the presence or absence of a specific adenosine A(1) receptor antagonist (KW-3902; 2 microg/ml) or a specific A(2) receptor antagonist (KF17837; 6 microg/ml). Diatrizoate (n=6) produced a fall in GFR from 0.65+/-0.04 to 0.42+/-0.03 ml.min(-1).g(-1) (P<0.05); renal perfusate flow (RPF) also declined, from 36.5+/-3.8 to 22.0+/-3.2 ml. min(-1).g(-1) (P<0.05). Iotrolan (n=6) produced a fall in GFR from 0. 64+/-0.02 to 0.48+/-0.04 ml.min(-1).g(-1) (P<0.05) and in RPF from 33.3+/-3.8 to 24.0+/-3.0 ml.min(-1).g(-1) (P<0.05). Theophylline (10.8 microg/ml) prevented the fall in GFR caused by either diatrizoate (baseline, 0.63+/-0.05 ml.min(-1).g(-1); diatrizoate+theophylline, 0. 60+/-0.04 ml.min(-1).g(-1)) or iotrolan (baseline, 0.64+/-0.04 ml. min(-1).g(-1); iotrolan+theophylline, 0.67+/-0.05 ml.min(-1).g(-1)), but did not affect the decreases in RPF caused by either agent. KW-3902 (2 microg/ml) also prevented the fall in GFR produced by diatrizoate (baseline, 0.66+/-0.05 ml.min(-1).g(-1); diatrizoate+KW-3902, 0.61+/-0.05 ml.min(-1).g(-1)), while the fall in RPF remained unaffected. KF17837 (6 microg/ml) had no effect on the decreases in either GFR or RPF induced by diatrizoate (n=6 per group). The results suggest a role for adenosine acting at the A(1) receptor in mediating the decrease in GFR induced by contrast media. This effect is independent of a change in renal vascular resistance, and possibly secondary to mesangial cell contraction causing a decrease in the ultrafiltration coefficient.

Regulation of renal adenosine A(1) receptors: effect of dietary sodium chloride

The influence of dietary NaCl on the regulation of renal adenosine A(1) receptors was investigated in the rat. Renal membranes from rats fed on a diet low (0.04%) in NaCl showed a 46% increase in B(max) for the binding of [3H]-1,3-dipropyl-8-cyclopentylxanthine ([3H]DPCPX), a selective adenosine A(1) receptor antagonist, compared to membranes from rats fed on a normal diet (0.4% NaCl). Conversely, a high NaCl diet (4.0%) resulted in a 37% decrease in B(max). Levels of renal adenosine A(1) receptor mRNA were 65% lower in rats on a high salt diet. Autoradiographic studies showed that, for the inner medullary collecting ducts, a low NaCl diet resulted in a 30% increase in [3H]DPCPX binding with a 39% decrease noted in rats maintained on a high salt diet. The results indicate that changes in adenosine A(1) receptor density may represent a novel mechanism whereby the kidneys adapt to changes in salt load.

Role of K+ channels in A2A adenosine receptor-mediated dilation of the pressurized renal arcuate artery

1. Adenosine A2A receptor-mediated renal vasodilation was investigated by measuring the lumenal diameter of pressurized renal arcuate arteries isolated from the rabbit. 2. The selective A2A receptor agonist CGS21680 dilated the arteries with an EC50 of 130 nM. The CGS21680-induced vasodilation was, on average, 34% less in endothelium-denuded arteries. 3. The maximum response and the EC50 for CGS21680-induced vasodilation in endothelium-intact arteries were not significantly affected by incubation with the K+ channel blockers apamin (100 nM), iberiotoxin (100 nM), 3,4-diaminopyridine (1 mM), glibenclamide (1 microM) or Ba2+ (10 microM). However, a cocktail mixture of these blockers did significantly inhibit the maximum response by almost 40%, and 1 mM Ba2+ alone or 1 mM Ba2+ in addition to the cocktail inhibited the maximum CGS21680-response by 58% and about 75% respectively. 4. CGS21680-induced vasodilation was strongly inhibited when the extracellular K+ level was raised to 20 mM even though the dilator response to 1 microM levcromakalim, a K(ATP) channel opener drug, was unaffected. 5. CGS21680-induced vasodilation was inhibited by 10 microM ouabain, an inhibitor of Na+/K(+)-ATPase, but ouabain had a similar inhibitory effect on vasodilation induced by 30 nM nicardipine (a dihydropyridine Ca2+ antagonist) or 1 microM levcromakalim. 6. The data suggest that K+ channel activation does play a role in A(2A) receptor-mediated renal vasodilation. The inhibitory effect of raised extracellular K+ levels on the A(2A) response may be due to K(+)-induced stimulation of Na+/K(+)-ATPase.

The haemodynamic effects of iodinated water soluble radiographic contrast media: a review

All classes of iodinated water-soluble radiographic contrast media (RCM) are vasoactive with the iso-osmolar dimers inducing the least changes in the vascular tone. The mechanisms responsible for RCM-induced changes in the vascular tone are not fully understood and could be multifactorial. A direct effect on the vascular smooth muscle cells causing alterations in the ion exchanges across the cell membrane is thought to be an important factor in RCM-induced vasodilatation. The release of the endogenous vasoactive mediators adenosine and endothelin may also play a crucial role in the haemodynamic effects of RCM particularly in the kidney. In addition, the effects of RCM on blood rheology can cause a reduction in the blood flow in the microcirculation. The purpose of this review is to discuss the pathophysiology of the haemodynamic effects of RCM and to offer some insight into the biology of the endothelium and vascular smooth muscle cells as well as the pharmacology of the important vasoactive mediators endothelin and adenosine.