Citations

Abstract Background: Microsatellite instability (MSI) and BRAF mutation status are associated with colorectal cancer survival, whereas the role of body mass index (BMI) is less clear. We evaluated the association between BMI and colorectal cancer survival, overall and by strata of MSI, BRAF mutation, sex, and other factors. Methods: This study included 5,615 men and women diagnosed with invasive colorectal cancer who were followed for mortality (maximum: 14.7 years; mean: 5.9 years). Prediagnosis BMI was derived from self-reported weight approximately one year before diagnosis and height. Tumor MSI and BRAF mutation status were available for 4,131 and 4,414 persons, respectively. Multivariable hazard ratios (HR) and 95% confidence intervals (CI) were estimated from delayed-entry Cox proportional hazards models. Results: In multivariable models, high prediagnosis BMI was associated with higher risk of all-cause mortality in both sexes (per 5-kg/m2; HR, 1.10; 95% CI, 1.06–1.15), with similar associations stratified by sex (Pinteraction: 0.41), colon versus rectum (Pinteraction: 0.86), MSI status (Pinteraction: 0.84), and BRAF mutation status (Pinteraction: 0.28). In joint models, with MS-stable/MSI-low and normal BMI as the reference group, risk of death was higher for MS-stable/MSI-low and obese BMI (HR, 1.32; P value: 0.0002), not statistically significantly lower for MSI-high and normal BMI (HR, 0.86; P value: 0.29), and approximately the same for MSI-high and obese BMI (HR, 1.00; P value: 0.98). Conclusions: High prediagnosis BMI was associated with increased mortality; this association was consistent across participant subgroups, including strata of tumor molecular phenotype. Impact: High BMI may attenuate the survival benefit otherwise observed with MSI-high tumors. Cancer Epidemiol Biomarkers Prev; 24(8); 1229–38. ©2015 AACR.

Abstract Introduction: Peripheral blood leukocyte (PBL) telomere length is associated with colon cancer (CC) risk, but the relationship of PBL telomere length to survival in CC patients receiving chemotherapy is unknown. Methods: We measured relative telomere length (RTL) by qPCR of PBL DNA from 2,748 cases (53% male, 85% white, median age 58 yrs) in the North American Phase III Intergroup Trial N0147 that compared disease-free survival (DFS) among completely resected Stage III CC treated with mFOLFOX6 +/- cetuximab. Tumor markers were assessed, and 12% were BRAF mutant; 35% Kras mutant, and 12% deficient mismatch repair (dMMR). Linear and non-linear prognostic associations of PBL RTL to the primary endpoint of DFS were assessed by Cox models. Optimal categories of RTL were developed using cumulative martingale residual plots, designated from shortest to longest RTL (Table 1). Results: Never smokers had longer PBL RTL (p = 0.0006) than past or current smokers. Those with diabetes mellitus (DM) had longer PBL RTL than those without DM (p = 0.0165). PBL RTL was not associated with any tumor markers (MMR status; p = 0.7174; BRAF mutant vs wild-type (wt); p =0.4039; Kras mutant vs wt; p= 0.1149). PBL RTL was significantly associated with DFS in a non-linear form (p = 0.0389). Cases in the longer RTL category had more favorable DFS than those with shorter or longest RTL, (Table), which remained after adjusting for age, sex , T/N stage, grade, tumor markers, and treatment (p = 0.0230). We observed no significant interaction (p = 0.1490) between RTL categories and treatment. Conclusion: We observed a non-linear association between RTL and DFS in stage III CC, suggesting that an optimal range telomere length can influence tumor behavior in CC patients. Future studies of telomere maintenance mechanisms may help to explain the association of RTL with improved DFS. RTL is associated with smoking and DM in CC cases but further studies are needed to determine if either tobacco use or DM affect survival from CC by modulating PBL telomere length. Citation Format: Nivedita Basu, Ruth A. Johnson, Qian Shi, Garth D. Nelson, Julie M. Cunningham, Richard M. Goldberg, Frank A. Sinicrope, Daniel J. Sargent, Steven R. Alberts, Gloria M. Petersen, Stephen N. Thibodeau, Halcyon G. Skinner, Kristin Litzelman, Songwon Seo, Russell J. Vanderboom, Ronald E. Gangnon, Corinne D. Engelman, David N. Rider, Lisa A. Boardman. Telomeres and survival in stage III colon cancers: Findings from NCCTG N0147 (Alliance) study. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5102. doi:10.1158/1538-7445.AM2014-5102

Abstract BACKGROUND. Proteosome inhibition is associated with induction of the proapoptotic BH3 protein NOXA. Therefore, we hypothesize that the combination of the irreversible proteosome inhibitor, carfilzomib, will cooperatively enhance apoptosis induction by the BH3 mimetic drug, ABT-263. Given that nononcogenic addiction to proteosome activity has been reported in KRAS mutant cells, we utilized isogenic colorectal cancer (CRC) cell lines in which the endogenous wild-type (wt) or mutant alleles had been inactivated through targeted homologous recombination. Since proteasome blockade results in proteotoxic stress, we determined whether an autophagy inhibitor can enhance chemosensitivity. EXPERIMENTAL METHODS. Isogenic KRAS mutant (MUT) CRC cells (HCT116, DLD1; obtained from B. Vogelstein, JHU) were incubated with carfilzomib (25,50nM) alone or combined with ABT-263 (1 µM) and apoptosis was measured by caspase cleavage and annexin V+ labeling. Synergy was measured by calculation of the combination index. Effect of carfilzomib on Bcl-2 family proteins was determined by immunoblotting. Interaction of NOXA with MCL-1 was examined by immunoprecipitation. Knockdown of NOXA was achieved by lentiviral shRNA. Cells were incubated with drugs alone or combined with chloroquine, and autophagy (LC3I/II conversion) and apoptosis were analyzed. RESULTS. Carfilzomib was shown to potently and synergistically enhance ABT-263-induced apoptosis (2-fold) in both KRAS MUT and wild type (WT) cell lines, with the effect being modestly higher in wild type cells, as shown by annexin V+ staining and caspase cleavage. Carfilzomib induced NOXA expression in both KRAS MUT and WT cells, and reduced MCL-1 expression. Induced NOXA was shown to bind and sequester MCL-1 proteins. Knockdown of NOXA attenuated drug-induced apoptosis. Autophagy inhibition by chloroquine accumulated LC3II, but only modestly increased carfilzomib-induced cell death. CONCLUSION. Irreversible proteasome inhibition by carfilzomib synergistically enhanced ABT-263-induced cell death that is mediated by NOXA upregulation and its sequestration/neutralization of MCL-1. The finding of similar efficacy in KRAS MUT vs WT cells suggests that this combination may represent a novel therapeutic strategy in this tumor subset. Citation Format: Shengbing Huang, Koichi Okamoto, Frank A. Sinicrope. Carfilzomib synergistically enhances ABT-263-induced apoptosis due to NOXA induction in KRAS wild type and mutant colorectal cancer cell lines. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 337. doi:10.1158/1538-7445.AM2014-337

Background and aim Although Non-steroidal anti-inflammatory drugs reduce colorectal adenoma burden in familial adenomatous polyposis (FAP), the utility of combining chemopreventive agents in FAP is not known. We conducted a randomised trial of celecoxib (CXB) versus CXB+diflouromethylornithine (DFMO) to determine the synergistic effect, if any. Methods The primary endpoint was % change in adenoma count in a defined field. Secondary endpoints were adenoma burden (weighted by adenoma diameter) and video review of entire colon/rectal segments. Adverse event (AEs) were monitored by National Cancer Institution toxicity criteria. Results 112 subjects were randomised: 60 men and 52 women at a mean age of 38 years. For the 89 patients who had landmark-matched polyp counts available at baseline and 6 months, the mean % change in adenoma count over the 6 months of trial was −13.0% for CXB+DFMO and −1.0% for CXB (p=0.69). Mean % change in adenoma burden was −40% (CXB+DFMO) vs −27% (CXB) (p=0.13). Video-based global polyp change was −0.80 for CXB+DFMO vs −0.33 for CXB (p=0.03). Fatigue was the only significant AE, worse on the CXB arm (p=0.02). Conclusions CXB combined with DFMO yielded moderate synergy according to a video-based global assessment. No significant difference in adenoma count, the primary endpoint, was seen between the two study arms. No evidence of DFMO-related ototoxicity was seen. There were no adverse cardiovascular outcomes in either trial arm and no significant increase in AEs in the CXB+DFMO arm of the trial. Differences in outcomes between primary and secondary endpoints may relate to sensitivity of the endpoint measures themselves. Trial registration number ClinicalTrials.gov number N01-CN95040.

Abstract KRAS mutations are frequently detected in human colorectal cancer and contribute to de novo apoptosis resistance and ultimately therapeutic failure. To overcome KRAS-mediated apoptosis resistance, the irreversible proteasome inhibitor, carfilzomib, was evaluated and found to potently induce Noxa, which was dependent upon c-Myc, and Bik. Isogenic mutant versus wild-type KRAS carcinoma cells showed elevated Bcl-xL, confirmed by KRAS siRNA or ectopic expression. Upregulated Bcl-xL by mutant KRAS was mediated by ERK as indicated by ERK knockdown. Bcl-xL expression was regulated at the level of mRNA and protein as shown using actinomycin D and cyclohexamide, respectively. Suppression of Bcl-xL by shRNA sensitized mutant KRAS cells to carfilzomib. Concurrent Bcl-xL antagonism by the BH3 mimetic ABT-263 combined with carfilzomib synergistically enhanced apoptosis that was dependent on Bax or p53, and was attenuated by Noxa or Bik shRNA. In support of this strategy, ectopically expressed Noxa enhanced apoptosis by ABT-263. Carfilzomib-induced Noxa and Bik sequestered Mcl-1 and ABT-263 released Bik and Bak from Bcl-xL, suggesting a mechanism for drug synergy. These preclinical findings establish mutant KRAS-mediated Bcl-xL upregulation as a key mechanism of apoptosis resistance in KRAS-mutant colorectal cancer. Furthermore, antagonizing Bcl-xL enabled carfilzomib-induced Noxa and Bik to induce synergistic apoptosis that reversed KRAS-mediated resistance. Implications: This novel study reveals a promising treatment strategy to overcome apoptosis resistance in KRAS-mutant colorectal cancer by concurrent upregulation of Noxa/Bik and antagonism of Bcl-xL. Mol Cancer Res; 13(4); 659–69. ©2014 AACR.

Abstract Background: Autophagy and apoptosis regulate cancer cell viability in response to cytotoxic stress; however, the functional relationship between these processes is unclear. During autophagy, the multifunctional p62/sequestosome 1 protein shuttles ubiquitinated proteins to the lysosome. Previously, we found that ectopic p62 can promote chemotherapy-induced apoptosis. Since Bcl-2 can regulate both autophagy and apoptosis, we determined whether ABT-263-induced apoptosis is regulated by p62. Methods: Human colorectal cancer cell lines (HCT116, DLD1) were incubated with ABT-263 (0-2 μM) and caspase cleavage (immunoblotting), caspase-8 activation (luminescence), apoptosis (annexin V labeling), and autophagy (localization of GFP-LC3 by confocal microscopy) were analyzed. Caspase-8 was suppressed by siRNA or using caspase-8-deficient Jurkat cells. P62 mutants were generated by site-directed mutagenesis. Caspase-8 self aggregation and colocalization with p62 were studied in cells with lentiviral mCherry-p62, transfected with a non-cleavable caspase-8 fused with fluorescent Venus proteins (BiFC). Results: We demonstrate that ABT-263 induces autophagy and a caspase-8-mediated apoptosis, shown using caspase-8 siRNA or caspase-8-deficient cells. Regulation of this process by p62 was demonstrated by the ability of ectopic p62 expression to enhance apoptosis and caspase-8 activation that were disrupted by mutations at p62 functional domains. In contrast, p62 shRNA was shown to attenuate ABT-263-induced apoptosis. ABT-263 treatment enhanced binding between caspase-8 and p62, and triggered caspase-8 self aggregation that colocalized with p62, shown by Biomolecular Fluorescence Complementation (BiFC) assay using confocal microscopy. Consistent with ectopic p62, accumulation of p62 by the lysosomal autophagy inhibitors, chloroquine or bafilomycin A1, enhanced ABT-263-mediated caspase cleavage. Conclusion: p62 can regulate caspase-8 self aggregation/activation by ABT-263 to enable crosstalk between autophagy and apoptosis. Citation Format: Shengbing Huang, Jae Myung Park, Chunrong Yu, Frank A. Sinicrope. p62/sequestosome 1 regulates caspase-8 activation by the Bcl-2 antagonist ABT-263 to enable crosstalk between autophagy and apoptosis. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1733. doi:10.1158/1538-7445.AM2013-1733

AbstractPurpose: A let-7 microRNA-complementary site (LCS6) polymorphism in the 3′ untranslated region of the KRAS gene has been shown to disrupt let-7 binding and upregulate KRAS expression. We evaluated the LCS6 genotype and its association with KRAS mutation status, clinicopathologic features, and disease-free survival (DFS) in patients with stage III colon cancer who enrolled in a phase III clinical trial (NCCTG N0147).Experimental Design: The LCS6 genotype was assayed by real-time PCR in DNA extracted from whole blood (n = 2,834) and compared with paired tumor tissue (n = 977). χ2 and two-sample t tests were used to compare baseline factors and KRAS mutation status between patients defined by LCS6 variant status. Log-rank tests and multivariate Cox models assessed associations between LCS6 status and DFS, respectively.Results: We identified 432 (15.2%) blood samples and 143 (14.6%) tumor samples heterozygous or homozygous for the LCS6 G-allele, and 2,402 of 2,834 (84.8%) blood samples and 834 of 977 (85.4%) tumor samples homozygous for the LCS6 T-allele. Genotype results were highly concordant (99.8%) in cases with paired blood and tumor tissue (n = 977). G-allele carriers were significantly more frequent in Caucasians versus other races (χ2 test, P < 0.0001). The LCS6 genotype was not associated with KRAS mutation status, clinicopathologic features (all P > 0.2), or DFS (log-rank P = 0.49; HR, 0.929; 95% confidence interval, 0.76–1.14), even after combining LCS6 genotype with KRAS mutation status.Conclusions: In the largest association study investigating the LCS6 polymorphism in colon cancers, the germline LCS6 genotype was not associated with KRAS mutation status or with clinical outcome in patients with stage III tumors. Clin Cancer Res; 20(12); 3319–27. ©2014 AACR.

Abstract Purpose: We examined the prognostic impact of specific KRAS mutations in patients with stage III colon adenocarcinoma receiving adjuvant FOLFOX alone or combined with cetuximab in a phase III trial (N0147). Analysis was restricted to BRAF–wild-type tumors, because BRAF mutation was associated with poor prognosis, and BRAF and KRAS mutations are mutually exclusive. Experimental Design: The seven most common KRAS mutations in codon 12 and codon 13 were examined in 2,478 BRAF–wild-type tumors. Because KRAS mutations in codon 12 (n = 779) or 13 (n = 220) were not predictive of adjuvant cetuximab benefit, study arms were pooled for analysis. Disease-free survival (DFS) was evaluated by HRs using Cox models. Results: KRAS mutations in codon 12 (multivariate HR, 1.52; 95% confidence interval, CI, 1.28–1.80; P < 0.0001) or codon 13 (multivariate HR, 1.36; 95% CI, 1.04–1.77; P = 0.0248) were significantly associated with shorter DFS compared with patients with wild-type KRAS/BRAF tumors, independent of covariates. KRAS codon 12 mutations were independently associated with proficient mismatch repair (P < 0.0001), proximal tumor site (P < 0.0001), low grade, age, and sex, whereas codon 13 mutations were associated with proximal site (P < 0.0001). Conclusion: KRAS mutations in either codon 12 or 13 are associated with inferior survival in patients with resected stage III colon cancer. These data highlight the importance of accurate molecular characterization and the significant role of KRAS mutations in both codons in the progression of this malignancy in the adjuvant setting. Clin Cancer Res; 20(11); 3033–43. ©2014 AACR.

Abstract Abundant epidemiologic evidence indicates that regular and long-term use of aspirin is associated with a significant reduction in the incidence of colorectal cancer. The long duration of aspirin needed to prevent colorectal cancer is believed to be due to inhibition of precursor lesions known as adenomas, the recurrence of which is inhibited by aspirin in randomized trials. Aspirin intake has also been associated with a statistically significant improvement in patient survival after curative resection of colorectal cancer in large observational studies. In these cohorts, the survival benefit of aspirin was shown to depend upon the level of COX-2 expression in the primary colorectal cancer. More recent analysis of patient tumors from these observational cohorts suggests that the benefit of aspirin may be limited to specific molecular subtypes. Aspirin intake following colorectal cancer resection was associated with a significant improvement of survival in patients whose tumors carried mutant, but not wild-type, copies of the phosphoinositide 3-kinase (PI3KCA) gene, especially tumors that overexpressed COX-2. A mechanistic explanation is suggested by the finding that inhibition of COX-mediated prostaglandin E2 synthesis by aspirin attenuates PI3K signaling activity that is known to regulate cancer cell proliferation and survival. Aspirin has also been shown to reduce the incidence of colorectal cancers bearing wild-type, but not mutant alleles of the BRAFV600E oncogene. Although provocative, the potential utility of these molecular markers for predicting aspirin efficacy awaits prospective evaluation in clinical trials. If validated, these findings may support a personalized approach to using aspirin for the therapy of colorectal cancer. Clin Cancer Res; 20(5); 1087–94. ©2013 AACR.