Citations

3066 Background: The BRAFV600E mutation is associated with the hypermethylator phenotype CIMP, which can also lead to the MSI-H phenotype. BRAFV600E mutation and MSI-H/dMMR status seem to be biologically intertwined; however, the impact of coexisting BRAFV600E mutations on the TME and immunometabolomic features of MSI-H/dMMR CRC tumors is not well characterized. Methods: A retrospective review of deidentified records of patients with MSI-H/dMMR CRC tumors was conducted using next-generation sequencing data (Tempus |xT assay: DNA-seq of 595-648 genes at 500x coverage, and full transcriptome RNA-seq). Several immune markers of tumor immunogenicity in BRAF wild-type ( BRAFwt) vs. V600E-mutated (BRAFV600E) tumors were assessed, including tumor mutational burden (TMB), neoantigen tumor burden (NTB, ScanNeo), PD-L1 expression, immune infiltration, and canonical immuno-metabolomic pathways (82 geneset signatures). Results: A total of 459 MSI-H/dMMR CRC tumors were analyzed, of which 123 (27%) tumors harbored BRAFV600Emutations, and 336 (73%) were BRAFwt. MSI-H/dMMR BRAFV600E tumors were more frequently identified in females (69% vs. 55%; P= 0.01), non-Hispanic or non-Latino (100% vs. 73%; P =0.001), and older patients (median age: 76 yrs vs. 62 yrs; P< 0.001). Compared to BRAFWT, BRAFV600E tumors exhibited significantly higher TMB (Median: 49 mut/MB vs. 36 mut/MB; P < 0.001) and were more frequently associated with TMB-High status (> 10 mut/MB; 100% vs. 95%; P = 0.008); however, no significant differences were observed with tumor NTB, immune score, or T cell infiltration (CD4 or CD8). NK cell infiltration was higher in the BRAFV600Ecohort (< 0.001). When compared to BRAFWT tumors , BRAFV600E tumors harbored a greater frequency of mutations in MSH6(42% vs. 20%), B2M (33% vs. 16%), BRCA2 (31% vs. 12%), ATM (23% vs. 12%), and TP53 (30% vs. 19%) but a lower frequency of MSH2 (3.3% vs. 11%), all P< 0.05. Pathway enrichment analysis identified 10 significantly altered signaling pathways, most of which related to stromal/immune cell signaling and metabolism. Five were upregulated among BRAFV600E tumors: glycerophospholipid, galactose, cyclin-dependent cell signaling; Nucleotide, and TH1 inflammation. Five pathways were downregulated (Wnt, Notch, TH17 inflammation, amino sugar, and cancer stem cell signaling). Conclusions: MSI-H/dMMR BRAFV600E CRCs undergo broad metabolic reprogramming (e.g., glycerophospholipidgalactose, nucleotide). A rise in lipid metabolism, particularly with NK inflammation, suggests that BRAFV600Emutated tumors may be associated with a non-classical immune component. BRAFV600E and BRAFwt CRCs exhibited similar NTB and T cell infiltration, suggesting that both are likely to benefit from immune checkpoint inhibitors.

Colorectal cancer (CRC) with deficient DNA mismatch repair (dMMR) is characterized by hypermutation leading to abundant neoantigens that activate an antitumor immune response in the tumor microenvironment. Immune checkpoint inhibitors (ICIs) have transformed the treatment of this subset of CRC and other solid tumors with dMMR, by producing frequent and durable responses that extend patient survival. Recently, the anti–programmed death-1 (PD-1) antibody pembrolizumab was shown to produce significantly longer progression-free survival with fewer adverse events compared with chemotherapy as first-line treatment of metastatic CRC (mCRC) with dMMR. Accordingly, single-agent pembrolizumab represents a new standard of care for dMMR mCRCs including patients with Lynch syndrome and the more common sporadic cases. Furthermore, data indicate that the combination of PD-1 and cytotoxic T-cell lymphocyte-4 inhibitors was more effective than single-agent PD-1 inhibition in patients with dMMR mCRCs, suggesting nonredundant mechanisms of action. Although the benefit of ICIs is currently limited to metastatic disease, studies evaluating ICIs as neoadjuvant and adjuvant therapy in earlier-stage dMMR CRC are ongoing. Despite success of ICIs in the treatment of metastatic dMMR cancers, an appreciable proportion of these tumors demonstrate intrinsic or acquired resistance, and biomarkers to identify these patients are needed. Advances in the understanding of immunotherapy resistance mechanisms hold promise for both biomarker identification and development of novel strategies to circumvent treatment resistance. In this review, we present a comprehensive overview of the evidence for the role of immunotherapy in the treatment of dMMR CRC, discuss resistance mechanisms, and outline potential strategies to circumvent primary and secondary resistance with the goal of broadening the benefit of ICIs.

11 Background: Six months of oxaliplatin-based adjuvant chemotherapy in patients with stage III colon cancer (CC) remains a standard in high-risk stage III patients. Early treatment discontinuation (ETD) could worsen the prognosis. In addition, there is current lack of data on the prognostic impact of early oxaliplatin only discontinuation (EOD). Methods: We studied the prognostic impact of ETD and EOD in patients with stage III CC who participated in 11 relevant clinical trials of the ACCENT and IDEA databases, where patients were planned to receive 6 months of adjuvant fluoropyrimidine plus oxaliplatin (FOLFOX or CAPOX). ETD was defined as discontinuation of treatment before 75% of cycles of chemotherapy. EOD was defined as discontinuation of oxaliplatin only, while continuing the fluoropyrimidine, before 75% of cycles of oxaliplatin. Association between ETD/EOD and overall survival (OS) and disease-free survival (DFS) was assessed by Cox model adjusted for prognostic factors. Results: ETD analysis included 10,444 patients (FOLFOX n = 7,033; CAPOX n = 3,411), with 20.9% of patients with ETD (17.8% with FOLFOX and 27.2% with CAPOX, p < 0.001). Out of 7,243 patients, 18.8% experienced EOD (17.4% FOLFOX versus 21.4% with CAPOX, p < 0.001). Compared to patients without ETD or EOD, patients with ETD or EOD were statistically more likely to be women, older, with higher ECOG-PS ≥ 1, and in addition for ETD, a Body Mass Index (BMI) < 18.5 kg/m2. In multivariate analyses, ETD was associated with a decrease in DFS and OS in the overall population (HR: 1.40 95%CI 1.23-1.58, p < 0.001 and HR: 1.51 95%CI 1.31-1.74, p < 0.001, respectively). The same pattern was present with FOLFOX and CAPOX regimen, and also in low-risk and high-risk groups for each regimen with the exception of the CAPOX regimen in the low-risk group for DFS and OS. By contrast, EOD was not associated with reduced DFS or OS in the overall population (HR: 1.10 95%CI 0.77-1.58, p = 0.6 and HR: 0.97 95%CI 0.62-1.52, p = 0.9, respectively), in the low-risk group (HR: 0.97 95%CI 0.56-1.66, p = 0.9 and HR: 0.97 95%CI 0.51-1.82, p = 0.9, respectively) and high-risk group (HR: 1.22 95%CI 0.74-2.02, p = 0.4 and HR: 1.05 95%CI 0.53-2.08, p = 0.9, respectively) and for all subgroups of regimen. Conclusions: In patients treated with 6 months of oxaliplatin-based adjuvant chemotherapy for stage III CC, ETD was associated with a decrease in DFS and OS. By contrast, EOD was not significantly associated with poorer outcomes. In case of relevant neurotoxicity during a 6 months schedule, these data are not in favor of continuing oxaliplatin beyond 75% of planned cycles of adjuvant chemotherapy, and demonstrate that fluoropyrimidines remain the cornerstone of adjuvant chemotherapy in localized CC.

AbstractBackgroundAdipocyte-derived adiponectin may play a role in the host inflammatory response to cancer. We examined the association of plasma adiponectin with the density of tumor-infiltrating lymphocytes (TILs) in colon cancers and with vitamin D, clinicopathological features, and patient survival.MethodsPlasma adiponectin and 25-hydroxyvitamin D [25(OH)D] were analyzed by radioimmunoassay in 600 patients with stage III colon cancer who received FOLFOX-based adjuvant chemotherapy (NCCTG N0147 [Alliance]). TIL densities were determined in histopathological sections. Associations with disease-free survival (DFS), time to recurrence, and overall survival were evaluated by multivariable Cox regression adjusting for potential confounders (ie, body mass index, race, TILs, and N stage). All statistical tests were 2-sided.ResultsWe found a statistically significant reduction in adiponectin, but not 25(OH)D, levels in tumors with high vs low TIL densities (median = 6845 vs 8984 ng/mL; P = .04). A statistically significant reduction in adiponectin was also observed in obese (body mass index &gt;30 kg/m2) vs nonobese patients (median = 6608 vs 12 351 ng/mL; P &lt; .001), in men vs women (median = 8185 vs 11 567 ng/mL; P &lt; .001), in Blacks vs Whites or Asians (median = 6412 vs 8847 vs 7858 ng/mL; P &lt; .03), and in those with fewer lymph node metastases (N1 vs N2: median = 7768 vs 9253 ng/mL; P = .01). Insufficiency of 25(OH)D (&lt;30 ng/mL) was detected in 291 (48.5%) patients. In multivariable analyses, neither adiponectin nor 25(OH)D were associated with a statistically significant difference in DFS, overall survival , or time to recurrence in models adjusted for potential confounders. We found a statistically significant association of TILs with prognosis, yet no such interaction was observed for the association of adiponectin with TILs for DFS.ConclusionsLower circulating adiponectin levels were associated with a statistically significant increase in TIL densities in colon cancers, indicating an enhanced antitumor immune response. In contrast to TILs, neither adiponectin nor 25(OH)D was independently prognostic.

Abstract Current classification of colorectal cancer (CRC) is based on TNM staging which does not account for considerable within stage variability in clinical outcome. Currently, there is no immune-based classification of colon cancer although data suggest that intratumoral T-cell densities can provide prognostic information that is more robust than that has been provided by genomic or transcriptomic profiling. A subset of CRCs show microsatellite instability (MSI) that is a predictive biomarker for immune checkpoint inhibitors whose indication in CRC is limited to metastatic tumors. In a prior study, we compared the density and localization of CD3+ and cytotoxic CD8+ T-cell densities in non-metastatic colon cancers with deficient (dMMR) vs proficient (pMMR) DNA mismatch repair (MMR). CD3+ at the tumor invasive margin (IM) was most strongly associated with patient overall survival, and dichotomization of CD3+ prognostically stratified both dMMR and pMMR tumors. The ability to stratify dMMR tumors was a novel observation and revealed a poorer prognosis dMMR group. By multivariable (MV) analysis, CD3+ density and N (nodal) stage contributed the most to patient survival. In separate studies, expression of FOXP3+ Tregs in CRC has paradoxically been associated with more favorable survival. Interestingly, we found that colon cancers with low FOXP3+ and low CD8+ are a very poor prognostic subset. Immunoscore (IS; HalioDx) is a validated assay that examines CD3+ and CD8+ using digital pathology with conversion of densities into percentile scores using a software algorithm. In patients with stage III colon cancers from a completed adjuvant trial, recurrence rates were inversely related to IS score (0-4), and the dichotomized IS was associated with significantly better survival across all disease subgroups (Forest plot). Stage III colon cancers are categorized into low risk (T1-3N1) and high risk (T4 and/or N2) groups for guiding the duration of adjuvant chemotherapy (3 vs 6 months). IS was shown to prognostically stratify patients within both risk groups and was only a significant variable in low risk tumors by MV analysis. These data suggest the potential of IS to further risk stratify patients and to potentially inform treatment decisions. In patients with metastatic CRC, analysis of IS was shown to predict tumor metastatic burden which had prognostic value. Data also suggest that potential for IS to provide predictive information for chemotherapy (fluoropyrimidine + oxaliplatin) response in CRC, yet further studies are needed. A potential mechanism is immunogenic cell death induced by some anti-cancer drugs, including oxaliplatin. Regarding immune checkpoint inhibitors (ICPs), only 40-50% of patients with metastatic CRC respond to such therapy, and small studies in suggest that TIL densities may be a factor in observed variability in response to ICP inhibitors. To further explore this issue, we are examining tumor immunophenotypes in relationship to response and outcome in CRC patients treated with anti-PD-1 antibodies. We aim to develop a MV model, and to validate it in an independent dataset. Important and relevant issues include the fact that only a fraction of mutations result in neoantigens recognized by T-cells, the potential for poor presentation of neoantigens by MHC1, as well as activating or suppressive cytokines. Citation Format: Frank A. Sinicrope. Analysis of immune contexture to refine prognosis in patients with colon cancer: Implications for immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr SY17-01.

Abstract Background Colorectal cancers (CRCs) are intrinsically drug resistant tumors with frequent low or absent tumor cell PD-L1 expression. Previously, we reported that PD-L1 depletion in CRC cells can confer chemoresistance. Given that JNK signaling has been implicated in cell survival and drug resistance in CRC cells, we examined the role of JNK and its regulation in chemoresistance in CRC cells with loss of PD-L1. Materials & MethodsHuman CRC cell lines (RKO, DLD1 and HCT15) were utilized and parental and PD-L1 knockout/knockdown cells were generated. Cells were treated with a JNK1-3 inhibitor (JNK-IN-8) alone or combined with a MEK1/2 inhibitor (cobimetinib), CPT-11 or oxaliplatin. Protein/protein interaction was analyzed by immunoprecipitation (IP); protein/RNA interaction was analyzed by RNA IP assay. RNA level and half life were measured by QRT-PCR. Apoptosis was measured by cleaved caspase-3 and quantified by Annexin V labeling using FACS. Colony formation assay was performed. ResultsPD-L1 depletion in CRC cells was shown to enhance JNK activity that was due to reduced mRNA stability of the upstream CYLD deubiquitinase. Since PD-L1 competes with the ribonuclease EXOSC10 for binding to CYLD mRNA, loss of PD-L1 increases the interaction of EXOSC10 and CYLD mRNA resulting in its ribonuclease-mediated degradation and activation of JNK signaling. JNK activation increased BIM phosphorylation at Thr116 that promotes its sequestration by MCL-1 and BCL-2. Notably, a selective and irreversible JNK1-3 inhibitor (JNK-IN-8) reduces BIMThr116 phosphorylation and can release BIM from its sequestration by MCL-1 and BCL-2 to promote apoptosis. Furthermore, use of JNK-IN-8, an MCL-1 antagonist (AZD5991), or their combination in tumor cells lacking PD-L1 is shown to promote apoptosis and reduce long-term clonogenic survival induced by multiple anti-cancer drugs. As confirmation, knockdown of PD-L1 can confer drug resistance in a human colon cancer-derived organoid model that can be reversed by JNK-IN-8. Conclusion Tumor cells with low or absent PD-L1 expression show increased JNK activity that promotes BIM sequestration by MCL-1/BCL-2 to confer multiple drug resistance that can be reversed by a JNK inhibitor. Citation Format: Frank A. Sinicrope, Lei Sun, Arpad Patai, Tara L. Hogenson, Martin E. Fernandez-Zapico, Bo Qin. PD-L1-mediated resistance to chemotherapy is overcome by an irreversible JNK inhibitor in colorectal cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1085.

Abstract Background Colon cancer (CC) incidence in young adults (age 20-49 years), termed early-onset CC (EO-CC), is increasing. Methods Individual patient data on 35 713 subjects with stage III colon cancer from 25 randomized studies in the Adjuvant Colon Cancer ENdpoint database were pooled. The distributions of demographics, clinicopathological features, biomarker status, and outcome data were summarized by age group. Overall survival, disease-free survival, time to recurrence, and survival after recurrence were assessed by Kaplan-Meier curves and Cox models stratified by treatment arms within studies, adjusting for sex, race, body mass index, performance status, disease stage, grade, risk group, number of lymph nodes examined, disease sidedness, and molecular markers. All statistical tests were 2-sided. Results Using a 5% difference between age groups as the clinically meaningful cutoff, patients with stage III EO-CC had similar sex, race, performance status, risk group, tumor sidedness, and T stage compared with patients with late-onset CC (age 50 years and older). EO-CC patients were less likely to be overweight (30.2% vs 36.2%) and more commonly had 12 or more lymph nodes resected (69.5% vs 58.7%). EO-CC tumors were more frequently mismatch repair deficient (16.4% vs 11.5%) and less likely to have BRAFV600E (5.6% vs 14.0%), suggesting a higher rate of Lynch syndrome in EO-CC. Patients with EO-CC had statistically significantly better overall survival (hazard ratio [HR] = 0.81, 95% confidence interval [CI] = 0.74 to 0.89; P &lt; .001), disease-free survival (HR = 0.91, 95% CI = 0.84 to 0.98; P = .01), and survival after recurrence (HR = 0.88, 95% CI = 0.80 to 0.97; P = .008) in the analysis without molecular markers; however, age at onset of CC lost its prognostic value when outcome was adjusted for molecular markers. Conclusion Tumor biology was found to be a more important prognostic factor than age of onset among stage III colon cancer patients in the Adjuvant Colon Cancer ENdpoint database.

3597 Background: Colon cancer (CC) incidence and mortality have decreased since the 1970s, but the incidence in young adults (20-49 years) is increasing. There are limited data suggesting that, as a group, patients with early onset CRC (eoCC) may have different phenotypic characteristics compared to those with late onset CRC (loCC, age ≥ 50 years). Methods: Individual patient data on 35,713 subjects with stage III CC from 25 randomized studies (recruiting between 1987 and 2009) in the ACCENT database were pooled. The distributions of demographics, clinicopathological features, biomarkers, and outcome data were summarized by age group. Overall survival (OS), disease-free survival (DFS), recurrence free rate (RFR), and survival after recurrence (SAR) were assessed by Kaplan-Meier curves and Cox models stratified by treatment arms within studies, adjusting for gender, race, body mass index, performance status, disease stage, grade, risk group, number of lymph nodes examined, disease sidedness and molecular markers. Results: Using a 5% difference between age groups as the clinically meaningful cutoff, patients with stage III eoCC (n = 6246) had similar distributions according to gender, race, PS, risk group, tumor sidedness and T/N stage compared to those with loCC (n = 29467). Patients with eoCC were significantly less likely to be overweight (30.2% vs 36.2%) but more commonly had ≥ 12 lymph nodes resected (69.5% vs 58.7%). The eoCC tumors were more frequently mismatch repair deficient (16.4% vs 11.5%), and less likely to have BRAFV600E (5.6% vs 14.0%), suggesting a higher frequency of Lynch syndrome in eoCC. In univariate analysis, patients with stage III eoCC had significantly better OS, DFS, and SAR; the difference between 3-year DFS and RFR strongly suggests the OS/DFS difference between these the eoCC and loCC may be due to increased competing risks and comorbidities in patients with loCC. In multivariate analysis, age at onset lost its prognostic value when outcome was adjusted for molecular markers. The clear relation between age of onset and KRAS/BRAF status was confirmed in the interaction analysis. Conclusions: Tumor biology was an important determinant of prognosis regardless of patient age. In multivariate analysis age of onset was not a statistically significant determinant of outcome.[Table: see text]

3591 Background: Adiponectin is a peptide hormone exclusively secreted by adipocytes that plays a role in immune regulation and in the host inflammatory response to cancer. We examined postsurgical adiponectin levels in relationship to tumor infiltrating lymphocytes (TILs), clinicopathological features, vitamin D status, and patient survival in participants in a phase 3 trial of adjuvant chemotherapy. Methods: Plasma adiponectin and 25-hydroxyvitamin D [25(OH)D] were analyzed by radioimmunoassay in 600 patients with stage III colon carcinoma who received adjuvant FOLFOX +/- cetuximab. TIL densities were determined at light microscopy in routine histopathological sections. The associations between adiponectin and 25(OH)D, TILs, other factors were evaluated by Fisher’s Exact, Chi-squared, t-test, and Kruskal-Wallis tests where appropriate. The association between adiponectin or 25(OH)D with disease-free survival (DFS), time to recurrence (TTR) and overall survival (OS) were evaluated by multivariable Cox regression, adjusting for body mass index (BMI), race, T, N stage, performance status, tumor location, TILs, BRAF/KRAS, and mismatch repair status. Results: A statistically significant and inverse association between adiponectin level and BMI was observed with lower levels found with obesity (BMI > 30 kg/m2) [p < 0.001]. The level of adiponectin was significantly lower in men vs women (p < 0.001), in blacks vs whites or Asians (p < 0.032), and in patients with fewer regional lymph node metastases (N1 vs N2 stage, p = 0.011). A significantly lower level of adiponectin was found in patients whose tumors had high vs low TIL densities (p = 0.040), but was unrelated to 25(OH)D. Insufficiency of 25(OH)D ( < 30 ng/ml) was detected in 291 (49%) of patients and was not associated with TILs. By multivariable analysis, adiponectin was not associated significantly with patient DFS (HRadj= 0.98, 95% CI 0.74-1.29, padj= 0.88) nor with OS nor time-to-recurrence (TTR). TIL densities were significantly prognostic, but 25(OH)D was not (DFS: HRadj= 1.12, 95% CI 0.85-1.47, padj= 0.44). No significant interaction was observed for adiponectin with TILs for the association with DFS. Conclusions: Lower adiponectin levels were associated with significantly increased TIL densities in colon cancers, indicating an enhanced anti-tumor immune response. In contrast to TILs, adiponectin was not independently associated with patient outcome. Nearly one-half of stage III patients were vitamin D insufficient, although 25(OH)D was not prognostic.