Sinicrope, Frank A.

Abstract Polyphenon E (Poly E) is a green tea polyphenol preparation whose most active component is epigallocatechin gallate (EGCG). We studied the cancer preventive efficacy and safety of Poly E in subjects with rectal aberrant crypt foci (ACF), which represent putative precursors of colorectal cancers. Eligible subjects had prior colorectal advanced adenomas or cancers, and had ≥5 rectal ACF at a preregistration chromoendoscopy. Subjects (N = 39) were randomized to 6 months of oral Poly E (780 mg EGCG) daily or placebo. Baseline characteristics were similar by treatment arm (all P >0.41); 32 of 39 (82%) subjects completed 6 months of treatment. The primary endpoint was percent reduction in rectal ACF at chromoendoscopy comparing before and after treatment. Among 32 subjects (15 Poly E, 17 placebo), percent change in rectal ACF number (baseline vs. 6 months) did not differ significantly between study arms (3.7% difference of means; P = 0.28); total ACF burden was also similar (−2.3% difference of means; P = 0.83). Adenoma recurrence rates at 6 months were similar by arm (P > 0.35). Total drug received did not differ significantly by study arm; 31 (79%) subjects received ≥70% of prescribed Poly E. Poly E was well tolerated and adverse events (AE) did not differ significantly by arm. One subject on placebo had two grade 3 AEs; one subject had grade 2 hepatic transaminase elevations attributed to treatment. In conclusion, Poly E for 6 months did not significantly reduce rectal ACF number relative to placebo. Poly E was well tolerated and without significant toxicity at the dose studied. Prevention Relevance: We report a chemoprevention trial of polyphenon E in subjects at high risk of colorectal cancer. The results show that polyphenon E was well tolerated, but did not significantly reduce the number of rectal aberrant crypt foci, a surrogate endpoint biomarker of colorectal cancer.

Colorectal cancer (CRC) is the third most commonly diagnosed cancer worldwide. Universal MMR/MSI testing is standard of care for all patients with newly diagnosed CRC based on multi-society guidelines in the United States. Such testing is intended to identify patients with Lynch Syndrome due to a germline mutation in an MMR gene, but also detects those with sporadic dMMR/MSI-high CRCs. The prognostic utility of MMR/MSI status in non-metastatic colorectal cancer has been studied extensively, yet more limited data are available for its predictive utility. Results have not been entirely consistent due to potential stage-related differences and limited numbers of dMMR/MSI-H patients included in the studies. In this review, we summarize the current evidence for the prognostic and predictive value of dMMR/MSI-H in non-metastatic CRC, and discuss the use of this biomarker for patient management and treatment decisions in clinical practice.

PURPOSE: In patients with stage III colon cancer (CC) whose tumors demonstrate microsatellite instability (MSI), the efficacy of adjuvant fluoropyrimidine (FP) with or without oxaliplatin has not been clearly demonstrated and the prognostic value of MSI remains uncertain. MATERIALS AND METHODS: Individual patient data from the ACCENT database were used to evaluate the effect of FP with or without oxaliplatin on disease-free survival (DFS) and overall survival (OS) among patients with MSI stage III CC and the prognostic value of MSI in patients treated with FP plus oxaliplatin, by stratified Cox models adjusted for demographic and clinicopathological factors. RESULTS: MSI status was available for 5,457 patients (609 MSI, 11.2%; 4848 microsatellite stable [MSS], 88.8%) from 12 randomized clinical trials (RCTs). Oxaliplatin significantly improved OS of MSI patients from the two RCTs testing FP with or without oxaliplatin (n = 185; adjusted hazard ratio [aHR] = 0.52, 95% CI, 0.28 to 0.93). Among the 4,250 patients treated with FP plus oxaliplatin (461 MSI and 3789 MSS), MSI was associated with better OS in the N1 group compared with MSS (aHR = 0.66; 95% CI, 0.46 to 0.95) but similar survival in the N2 population (aHR = 1.13; 95% CI, 0.86 to 1.48; P interaction = .029). The main independent prognosticators of MSI patients treated with FP plus oxaliplatin were T stage (aHR = 2.09; 95% CI, 1.29 to 3.38) and N stage (aHR = 3.57; 95% CI, 2.32 to 5.48). Similar results were observed for DFS in all analyses. CONCLUSION: Adding oxaliplatin to FP improves OS and DFS in patients with MSI stage III CC. Compared with MSS, MSI patients experienced better outcomes in the N1 group but similar survival in the N2 group.

Abstract Background: Cetuximab, an EGFR inhibitor used to treat multiple cancer types, including colon cancer, causes severe skin toxicity in 5%–20% of patients, leading to decreased quality of life and treatment delays. Our understanding of which patients have an increased risk of severe toxicities is limited. We conducted a genome-wide association study to identify germline variants predictive of cetuximab-induced severe skin toxicity. Methods: Our study included 1,209 patients with stage III colon cancer randomized to receive cetuximab plus 5-fluorouracil and oxaliplatin as part of the NCCTG N0147 (Alliance) clinical trial. Skin toxicity outcomes were collected using the Common Toxicity Criteria for Adverse Events version 3.0. We performed genotyping, evaluating approximately 10 million genetic variants. We used logistic regression to evaluate the association of each genetic variant and severe (grade ≥ 3) skin toxicity, adjusting for age, sex, and genetic ancestry. Genome-wide significance was defined as P < 5 × 10−8. Results: Participants were predominantly middle-aged white men; 20% (n = 243) experienced severe skin toxicity. Two genetic variants in the retinoic acid receptor alpha (RARA) gene were significantly associated with severe skin toxicity [OR, 3.93; 95% confidence interval (CI), 2.47–6.25; P < 7.8 × 10−9]. Functional annotations indicate these variants are in the RARA promoter. Additional significantly associated variants were identified in chromosome 2 intergenic regions. Conclusions: Identified variants could represent a potential target for risk stratification of patients with colon cancer receiving cetuximab. Impact: Retinoids have shown promise in the treatment of cetuximab-induced skin toxicity, so follow-up work could evaluate whether individuals with the RARA variant would benefit from retinoid therapy.

Abstract Tumor mutational burden (TMB), defined as the number of somatic mutations per megabase of interrogated genomic sequence, varies across malignancies. Panel sequencing–based estimates of TMB have largely replaced whole-exome sequencing–derived TMB in the clinic. Retrospective evidence suggests that TMB can predict the efficacy of immune checkpoint inhibitors, and data from KEYNOTE-158 led to the recent FDA approval of pembrolizumab for the TMB-high tumor subgroup. Unmet needs include prospective validation of TMB cutoffs in relationship to tumor type and patient outcomes. Furthermore, standardization and harmonization of TMB measurement across test platforms are important to the successful implementation of TMB in clinical practice. Significance: Evaluation of TMB as a predictive biomarker creates the need to harmonize panel-based TMB estimation and standardize its reporting. TMB can improve the predictive accuracy for immunotherapy outcomes, and has the potential to expand the candidate pool of patients for treatment with immune checkpoint inhibitors.

Abstract Background: PD-L1 is an immune checkpoint protein that may display intrinsic, non-immune functions in human cancer cells. Previously, we discovered that PD-L1 is regulated by BRAFV600E via YAP and c-Jun, and whose deletion can confer chemoresistance due to a decrease in the BH3-only BIM protein in colorectal cancer (CRC) cells. Here, we hypothesize that release of pro-apoptotic BIM from its sequestration by MCL-1 or BCL-2 can overcomes drug resistance mediated by depletion of PD-L1. Materials and Methods: Parental and PD-L1 knockout human (RKO) and murine (MC38) CRC cells with or without reconstituted PD-L1 were utilized. RKO cells with knockdown of MCL-1 or BCL-2 by shRNA were generated. Cells were treated with the MCL-1 selective inhibitor AZD5591 or the BCL-2/BCL-xL inhibitor ABT-263 alone or combined with the MEK inhibitor, cobimetinib. Apoptosis was measured by immunoblotting of cleaved caspase-3 and by Annexin V labeling using FACS. Clonogenic cell survival assay was performed. Protein/protein interaction was analyzed by immunoprecipitation assay. Results: BIM induction by cobimetinib was insufficient to overcome chemoresistance due to loss of PD-L1. Using a potent and selective inhibitor of MCL-1 (AZD-5591), we demonstrate that concurrent antagonism of MCL-1 and MEK can overcome apoptosis resistance in both human and murine PD-L1 knockout CRC cells. Specifically, inhibition of MCL-1 by AZD-5591 or gene knockdown combined with cobimetinib suppresses clonogenic cell survival and enhances apoptosis in cells with PD-L1 knockout, wild type or those with reconstituted PD-L1. Mechanistically, the interaction of BIM with MCL-1 is increased in PD-L1 knockout (versus wild-type cells) in the presence of cobimetinib, and enhanced binding of BIM to MCL-1 is associated with BIM phosphorylation at Thr116. Targeting MCL-1 using AZD-5591 or MCL-1 shRNA releases BIM from its sequestration by MCL-1 and results in enhanced apoptotic signaling induced by cobimetinib to an equivalent extent in wild type and PD-L1 knockout cells with or without reconstitution of PD-L1. Similarly, targeting BCL-2 by ABT-263 or by BCL-2 shRNA releases BIM from its binding to BCL-2, and enhances apoptosis induction by cobimetinib independent of PD-L1 status. Enhanced binding of BIM to BCL-2 was also associated with BIM phosphorylation at Thr116. Conclusion: Chemoresistance mediated by loss of PD-L1 can be reversed by the use of BH3 mimetic drugs combined with MEK inhibition in CRC cells to exploit their apoptotic dependency on BIM expression. Citation Format: Lei Sun, Arpad Patai, Bo Qin, Frank A. Sinicrope. Reversal of PD-L1-mediated chemoresistance by MCL-1/BCL-2 antagonism in colon cancer cells [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 1821.

11093 Background: Defective DNA mismatch repair (MMR) results in microsatellite instability (MSI) and is detected in approximately 15% of sporadic colon cancers. MMR status has been shown to provide prognostic and predictive information in primary colon cancers. We sought to develop a model to predict MMR deficiency using clinically available data, and thereby facilitate patient selection for MMR or MSI testing. Methods: TNM stage II and III colon carcinomas (n= 982) were studied from six 5- fluorouracil-based adjuvant therapy trials conducted by the North Central Cancer Treatment Group. MMR status in tumors had been analyzed by MSI (using mono- and dinucleotide markers) or by immunohistochemistry for MMR proteins (hMLH1 and hMSH2). Logistic regression and a recursive partitioning and amalgamation (RPA) analysis was used to identify important predictive factors of MMR status. Factors explored included age, gender, histologic grade, tumor site, stage, lymph node metastases, and T-stage. Results: Defective MMR was found in147 (15%) cancers. Tumor site was the most important predictor of MMR status followed by histologic grade. Distal tumors had a low likelihood of defective MMR (3% rate overall; 13/468), whereas proximal tumors had a greater likelihood of defective MMR (26%; 130/506). For patients with proximal tumors, the addition of histologic grade and gender increased the prediction of defective MMR ( Table ). Using tumor site, histologic grade, and gender, the logistic regression model showed excellent discrimination (c- statistic = 0.81). Conclusions: Tumor site is an important predictor of defective MMR that is rare in distal and increased in proximal tumors. The combination of proximal site, poor differentiation, and female gender resulted in a 51% likelihood of defective MMR. Therefore, this model can facilitate the selection of sporadic colon cancers for MMR or MSI testing to enable its use in clinical decision-making. [Table: see text] No significant financial relationships to disclose.