Mismatch Repair Proficient Colorectal Cancer Research Articles

Safety and efficacy of AMG 820, an anti-colony-stimulating factor 1 receptor antibody, in combination with pembrolizumab in adults with advanced solid tumors

BackgroundTo determine the safety and efficacy of the anti-colony-stimulating factor 1 receptor (anti-CSF1R) monoclonal antibody AMG 820 in combination with pembrolizumab in patients with select solid tumors.Patients and methodsPatients had...

Efficacy of Immunotherapy in Microsatellite-Stable or Mismatch Repair Proficient Colorectal Cancer—Fact or Fiction?

Efficacy of Immunotherapy in Microsatellite-Stable or Mismatch Repair Proficient Colorectal Cancer—Fact or Fiction?

A phase I/II study of Pexa-Vec oncolytic virus in combination with immune checkpoint inhibition in refractory colorectal cancer.

117 Background: The benefit of immune checkpoint inhibition is limited to the small percentage of advanced colorectal cancer (CRC) patients whose tumors present mismatch repair (MMR) gene abnormalities; immunotherapy has not shown benefit in patients with MMR proficient CRC. Oncolytic immunotherapy represents a unique therapeutic platform. This phase I trial tests the safety of the combination of pexastimogene devacirepvec (Pexa-Vec) plus durvalumab (durva) in patients with locally advanced or metastatic CRC. Methods: Eligible patients with advanced proficient mixed match repair (pMMR) CRC received intravenous infusion of Pexa-Vec at dose level 3 x 108 plaque forming units (pfu) (DL1) or at 109 pfu (DL2) every 2 weeks for 4 doses and durva 1500 mg every 28 days. Response was assessed with CT every 8 weeks. Adverse events were recorded and managed. The primary endpoint included safety, tolerability and feasibility of this combination therapy. Samples of tumor and peripheral blood were collected for assessment of immune parameters. Results: Sixteen patients (6 males and 10 females) enrolled with a median age of 52.1 years (range 39-69) from Dec, 2017 to Oct, 2018. Four patients were treated with Pexa-Vec at DL1 and durva;twelve patients were treated with Pexa-Vec at DL2 and durva.The most common treatment related adverse events (TRAE) included fever 15/16 (94 %), hypotension 12/16 (75 %), chills 12/16 (75%), fatigue 8/16 (50%), sinus tachycardia 7/16 (44%) and rash 6/16 (38%). Grade 3/4 TRAEs were reported in 8/16 (50%)patients; the most common were fever 7/16 (44 %), lymphopenia 2/16 (13%), neutropenia 1/16 (6%) and anemia 1/16 (6%). 14 patients were evaluable for response analysis; one patient 1/14 (7 %) achieved a confirmed partial response (lasting 7.1 months) and continues to receive treatment, while 13 patients had progressive disease. The median progression free survival (PFS) was 2.2 months (95% CI: 2.2-2.3 months) and the median overall survival (OS) was 7.5 months (CI: 4.9-10.1 months). Conclusions: Combination therapy of Pexa-Vec with durva ICI issafe, well tolerated and demonstrates possible activity in patients with advanced pMMR CRC. Clinical trial information: NCT03206073.

Biomarker analysis for UPCI 14-118: Phase II study of pembrolizumab in combination with azacitidine in patients with refractory metastatic colorectal cancer.

173 Background: DNA mismatch repair (MMR) proficient colorectal cancer (CRC) is resistant to immune checkpoint therapy compared to MMR deficient CRC. DNA hypomethylating agents may promote anti-tumor immune response by re-expression of cancer-testis antigen and reactivating immune genes suppressed by DNA methylation. This trial tested whether epigenetic modulation by concurrent treatment with azacitidine could enhance the anti-tumor activity of pembrolizumab in mCRC. Methods: Phase II trial was conducted to evaluate activity, safety, and tolerability of pembrolizumab in combination with azacitidine in patients with previously treated pMMR metastatic CRC. Patients received pembrolizumab 200 mg IV on day 1 and azacitidine 100 mg daily SQ injection on days 1-5 every 3 weeks. The primary endpoint of the study was ORR. Tumors were biopsied pre-treatment and on-treatment for biomarker studies. Results: 30 patients received at least one dose of therapy. One patient experienced a confirmed partial response, one experienced stable disease. ORR was 3% (1/30; 95% CI, 0.1-17%). Median PFS was 1.9 months, median OS was 6.3 months. Treatment was well tolerated with only one patient (3%) experiencing grade 3 adverse event. The patient with a PR had positive pre-treatment TILs, but no evaluable tumor from on-treatment biopsy. 2 of 6 patients who continued therapy despite PD on first restaging experienced temporary stabilization of disease later. 5 of 16 evaluable biopsy pairs demonstrated increased TILs on treatment compared to baseline; however, all of these patients experienced PD. 10 of 15 paired samples demonstrated decreased methylation of hypermethylated loci on-treatment. Clustering analysis demonstrated a correlation between pre-treatment methylation of immune activation genes with overall survival of the patients. Conclusions: Combining azacitidine and pembrolizumab is safe and tolerable for pMMR mCRC with only limited activity. DNA methylation and TIL changes are detectable after 3 cycles of therapy. DNA methylation of immune activation genes correlate with overall survival. RNA sequencing and peripheral immune cell flow cytometry are ongoing. Clinical trial information: NCT02260440.

Neoantigen-specific immunity in low mutation burden colorectal cancers of the consensus molecular subtype 4

BackgroundThe efficacy of checkpoint blockade immunotherapies in colorectal cancer is currently restricted to a minority of patients diagnosed with mismatch repair-deficient tumors having high mutation burden. However, this observation does not exclude the existence of neoantigen-specific T cells in colorectal cancers with low mutation burden and the exploitation of their anti-cancer potential for immunotherapy. Therefore, we investigated whether autologous neoantigen-specific T cell responses could also be observed in patients diagnosed with mismatch repair-proficient colorectal cancers.MethodsWhole-exome and transcriptome sequencing were performed on cancer and normal tissues from seven colorectal cancer patients diagnosed with mismatch repair-proficient tumors to detect putative neoantigens. Corresponding neo-epitopes were synthesized and tested for recognition by in vitro expanded T cells that were isolated from tumor tissues (tumor-infiltrating lymphocytes) and from peripheral mononuclear blood cells stimulated with tumor material.ResultsNeoantigen-specific T cell reactivity was detected to several neo-epitopes in the tumor-infiltrating lymphocytes of three patients while their respective cancers expressed 15, 21, and 30 non-synonymous variants. Cell sorting of tumor-infiltrating lymphocytes based on the co-expression of CD39 and CD103 pinpointed the presence of neoantigen-specific T cells in the CD39+CD103+ T cell subset. Strikingly, the tumors containing neoantigen-reactive TIL were classified as consensus molecular subtype 4 (CMS4), which is associated with TGF-β pathway activation and worse clinical outcome.ConclusionsWe have detected neoantigen-targeted reactivity by autologous T cells in mismatch repair-proficient colorectal cancers of the CMS4 subtype. These findings warrant the development of specific immunotherapeutic strategies that selectively boost the activity of neoantigen-specific T cells and target the TGF-β pathway to reinforce T cell reactivity in this patient group.

Mismatch Repair-Proficient Colorectal Cancer: Finding the Right TiME to Respond.

New approaches are required for addressing the important and unmet need to expand the benefits of checkpoint blockade to patients with mismatch repair proficient colorectal cancer. Systematic profiling of the tumor immune microenvironment provides insights into potential mechanisms of resistance, predictive biomarkers, and novel combinatorial strategies for overcoming resistance.See related article by Llosa et al., p. 5250.

Intratumoral Adaptive Immunosuppression and Type 17 Immunity in Mismatch Repair Proficient Colorectal Tumors.

Approximately 10% of patients with mismatch repair-proficient (MMRp) colorectal cancer showed clinical benefit to anti-PD-1 monotherapy (NCT01876511). We sought to identify biomarkers that delineate patients with immunoreactive colorectal cancer and to explore new combinatorial immunotherapy strategies that can impact MMRp colorectal cancer. We compared the expression of 44 selected immune-related genes in the primary colon tumor of 19 patients with metastatic colorectal cancer (mCRC) who responded (n = 13) versus those who did not (n = 6) to anti-PD-1 therapy (NCT01876511). We define a 10 gene-based immune signature that could distinguish responder from nonresponder. Resected colon specimens (n = 14) were used to validate the association of the predicted status (responder and nonresponder) with the immune-related gene expression, the phenotype, and the function of tumor-infiltrating lymphocytes freshly isolated from the same tumors. Although both IL17Low and IL17High immunoreactive MMRp colorectal cancers are associated with intratumor correlates of adaptive immunosuppression (CD8/IFNγ and PD-L1/IDO1 colocalization), only IL17Low MMRp tumors (3/14) have a tumor immune microenvironment (TiME) that resembles the TiME in primary colon tumors of patients with mCRC responsive to anti-PD-1 treatment. The detection of a preexisting antitumor immune response in MMRp colorectal cancer (immunoreactive MMRp colorectal cancer) is not sufficient to predict a clinical benefit to T-cell checkpoint inhibitors. Intratumoral IL17-mediated signaling may preclude responses to immunotherapy. Drugs targeting the IL17 signaling pathway are available in clinic, and their combination with T-cell checkpoint inhibitors could improve colorectal cancer immunotherapy.See related commentary by Willis et al., p. 5185.

Abstract 2793: Mismatch repair proficient colorectal cancer and adaptive immunosuppression of endogenous anti-tumor immune response: Implications for immunotherapy

Abstract The tumor immune microenvironment (TiME) of mismatch-repair deficient (MMRd) colorectal cancer (CRC) is characterized by a cytotoxic T cell immune signature and counter-expression of IFNγ -inducible T cell checkpoints, features underlining intratumoral adaptive immunosuppression and sensitivity to immune checkpoint blockade. Since single-agent checkpoint inhibitors have not demonstrated, so far, similar meaningful clinical activity for MMR proficient (MMRp) CRC, we compared the tumor immune microenvironment (TiME) in CRC patients that responded to anti-PD1 therapy with the TiME of patients that did not (NCT01876511) to identify immune signatures and biomarkers that could help deciding on combinatorial immunotherapies to treat patients with MMRp CRC. With this approach, we detected immunoreactive MMRp (irMMRp) tumors characterized by a dense infiltration with cytotoxic T cells (CTL) as well as high expression of IFNγ and CD274 (PD-L1), despite their low tumor mutation burden. We observed that these irMMRp colon tumors are characterized by a negative association between Indolamine 2,3 dioxygenase 1 (IDO1) expression and Th17 infiltration. Despite the high expression of CD8 and PD-L1 expression, only irMMRp CRC with high expression of IDO1 on tumor cells and low infiltration with Th17 cells have a TiME resembling the TiME of CRC responding to anti-PD1. Since IDO1-derived tryptophan metabolites, kynurenines, are known to repress Th17 differentiation, these results suggested that the use of IDO1 small molecule inhibitors may derepress Th17 infiltration in CRC and blunt the effect of anti-PD1. Combining therapy with IDO1/PD1 inhibitors with drugs inhibiting IL-17 signaling pathway may help to treat irMMRp CRC patients. Citation Format: Nicolas Llosa, Anas H. Awan, Ada J. Tam, Hongni Fan, Kellie N. Smith, Cynthia L. Sears, Hao Wang, Drew M. Pardoll, Robert A. Anders, Franck Housseau. Mismatch repair proficient colorectal cancer and adaptive immunosuppression of endogenous anti-tumor immune response: Implications for immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2793.

Abstract 579: Immune features and neoantigen recognition in mismatch repair-proficient colorectal cancer liver metastases

Abstract Immunotherapy for patients with non-highly mutated, mismatch repair-proficient (MMRprof) metastatic colorectal cancer has largely been unsuccessful thus far. Here, we used transcriptomics, genomics and in vitro analyses to study the adaptive immune features of colorectal cancer liver metastases (CRLMs), aiming to provide insights into the development of immunotherapies for this common malignancy. Analysis of the RNAseq data from 63 core biopsies obtained in patients enrolled in the Q-CROC-01 trial (NCT00984048) revealed 17 (27%) immune-reactive (IR) CRLMs, defined by concurrent relative high expression of antigen processing, immune cell, immune checkpoint, interferon-gamma response, cytokine, and chemokine transcripts. More T-cell receptor (TCR) sequences were found in IR vs. non-IR CRLMs (mean 89.8 ± 13.3 vs. 19.5 ± 4.0 CDR3 counts, p<0.0001), consistent with higher density of tumor-infiltrating T lymphocytes (TILs) confirmed by immunofluorescence. By whole exome analysis, no significant difference was found in non-synonymous somatic mutation (median 76) and neoantigen (neoAg) (median 18) counts comparing IR vs. non-IR CRLMs. High mutation or neoAg loads did not correlate with higher T cell infiltration. TILs were expanded in vitro from five CRLMs, one classified as high IR, two as moderate IR, and two as non-IR by immune gene expression profiling. TIL recognition of predicted neoAgs was tested in co-culture with autologous antigen-presenting cells pulsed with synthetic peptides. Only in the most immune reactive CRLM did we find CD8+ and CD4+ TIL clones (n=8) reactive to neoAg peptides derived from three single nucleotide variant genes, and none reactive to the wild-type peptide counterparts. In this case, by deep sequencing of intratumoral TCRs, the average frequency of neoAg-reactive TIL clones was estimated at 0.95% (range 0.003% to 3.3%), which represented a 3625 fold enrichment compared to the circulating blood. In general, expression of immune checkpoints was more highly correlated in IR vs. non-IR CRLMs. The following T cell-related conceptual pairs of immune checkpoint receptors & ligands were expressed at significantly higher levels in IR compared to non-IR CRLMs: HVEM/LTBR & BTLA/LIGHT, A2A & CD73, TIGIT & PVRL3, FAS & FASL, CD2/2B4 & CD48. Our results support that naturally occurring neoAg-reactive T cells may be therapeutically harnessed in a subgroup of metastatic MMRprof colorectal cancer patients selected based on the level of intratumoral immune reactivity, and potentially enhanced by targeting immune checkpoints more biologically relevant than PD-1/PD-L1 and CTLA-4/CD80. Citation Format: Steven Hébert, Mélissa Mathieu, David Henault, Maud Marques, Éric Audemard, Mathieu Courcelles, Scott D. Brown, Pratyaksha Wirapati, Sabine Tejpar, Michael I. D'Angelica, Robert A. Holt, Sylvie Mader, Pierre Thibault, Gerald Batist, Claudia Kleinman, Simon Turcotte. Immune features and neoantigen recognition in mismatch repair-proficient colorectal cancer liver metastases [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 579.

Combined prognostic value of CD274 (PD-L1)/PDCDI (PD-1) expression and immune cell infiltration in colorectal cancer as per mismatch repair status

The CD274 (programmed cell death ligand-1, PD-L1)/PDCD1 (programmed cell death-1, PD-1) pathway is crucial suppressor of the cytotoxic immune response. Antibodies targeting CD274 or PDCD1 have been revealed to be effective in several malignancies. In colorectal cancer, the response to CD274/PDCD1 blockage is associated with microsatellite instability. However, the value of CD274/PDCD1 for predicting response to treatment or survival benefit is still unclear. The aims of the study were (1) to clarify differences in immune microenvironment and expression of checkpoint proteins (CD274/PDCD1) in DNA mismatch repair-proficient, mismatch repair-deficient, and hereditary Lynch syndrome-associated colorectal cancer, and (2) to assess the prognostic value of these factors and their combinations. Ninety-four mismatch repair-deficient colorectal cancers, 100 age, sex, and AJCC/UICC stage-matched mismatch repair-proficient colorectal cancers, and 48 Lynch syndrome-associated colorectal cancers were analyzed. Using whole section samples, detailed analysis of immune cell score, PDCD1, and CD274 expression was performed. Overlapping of CD274 expression in tumor and immune cells was almost complete (95%). Immune cell score and CD274/PDCD1 positivity were significantly more frequent in mismatch repair-deficient than in mismatch repair-proficient colorectal cancers (70% vs. 41% (high immune cell score); 81% vs. 49% (PDCD1high), 23% vs. 1% (CD274 on tumor cells) and 68% vs. 30% (CD274 on immune cells), P < 0.001), and were associated strongly with each other. Although the independent impact of immune cell score, PDCD1, and CD274 on immune cells was moderate, the immunoprofile parameter combining the above three factors appeared to be a strong independent prognostic factor for disease-specific survival and overall survival (P = 0.001) and had suggestive impact on disease-free survival (P = 0.011). Our results encourage the use of immune cell score analysis together with PDCD1 and CD274 detection to improve the prognostic evaluation of colorectal cancer patients. Particularly, the analyses from whole tissue sections are encouraged to allow reliable and cell-specific analyses of CD274 expression.

Persistent mutant oncogene specific T cells in two patients benefitting from anti-PD-1

BackgroundSeveral predictive biomarkers are currently approved or are under investigation for the selection of patients for checkpoint blockade. Tumor PD-L1 expression is used for stratification of non-small cell lung (NSCLC) patients, with tumor mutational burden (TMB) also being explored with promising results, and mismatch-repair deficiency is approved for tumor site-agnostic disease. While tumors with high PD-L1 expression, high TMB, or mismatch repair deficiency respond well to checkpoint blockade, tumors with lower PD-L1 expression, lower mutational burdens, or mismatch repair proficiency respond much less frequently.Case presentationWe studied two patients with unexpected responses to checkpoint blockade monotherapy: a patient with PD-L1-negative and low mutational burden NSCLC and one with mismatch repair proficient colorectal cancer (CRC), both of whom lack the biomarkers associated with response to checkpoint blockade, yet achieved durable clinical benefit. Both maintained T-cell responses in peripheral blood to oncogenic driver mutations – BRAF-N581I in the NSCLC and AKT1-E17K in the CRC – years after treatment initiation. Mutation-specific T cells were also found in the primary tumor and underwent dynamic perturbations in the periphery upon treatment.ConclusionsThese findings suggest that T cell responses to oncogenic driver mutations may be more prevalent than previously appreciated and could be harnessed in immunotherapeutic treatment, particularly for patients who lack the traditional biomarkers associated with response. Comprehensive studies are warranted to further delineate additional predictive biomarkers and populations of patients who may benefit from checkpoint blockade.

A phase II study of GVAX colon vaccine with cyclophosphamide and pembrolizumab in patients with mismatch repair–proficient (MMR-p) advanced colorectal cancer.

563 Background: Mismatch repair proficient (MMRp) colorectal cancer (CRC) is refractory to single-agent programmed cell death protein 1 (PD1) inhibitors. Cancer vaccines may prime the tumor microenvironment for anti-PD1 therapy. Colon GVAX is an allogeneic, whole-cell, GM-CSF-secreting vaccine that induces T-cell immunity against tumor-associated antigens. GVAX has previously been studied in combination with low-dose cyclophosphamide (Cy) to inhibit regulatory T cells. Methods: We conducted an open label, single-arm, phase 2 study of GVAX/Cy in combination with the PD1 inhibitor pembrolizumab in patients with MMRp CRC who had received at least two prior lines of therapy in the metastatic setting. Patients received pembrolizumab plus Cy on day 1, GVAX on day 2, of a 21 day cycle through 4 cycles, and were then continued on a maintenance regimen of pembolizumab every 3 weeks with cy/GVAX given every 12 weeks. Results: Seventeen patients were enrolled. There were no objective responses, and the disease control rate was 18% by RECIST and 29% by irRC. The median progression free survival was 2.7 months and the median overall survival was 7.0 months. Biochemical responses (≥30% decline in CEA) were observed in 7/17 (41%) of patients. Two patients (12%) had grade 3/4 adverse events that were attributed to study therapy. To test the hypothesis that the induction of a humoral response against CEA protein had resulted in the observed biochemical responses, we measured patient titers of anti-CEA antibodies. Anti-CEA antibody titers increased 13 of 13 patients (100%) with available paired pre- and on-treatment research blood samples, but the change in anti-CEA antibody titers were similar among CEA responders and non-responders. Multiplex immunohistochemistry performed on pre- and post- biopsy specimens will be reported at the conference. Conclusions: GVAX/Cy plus pembrolizumab is well tolerated in advanced MMRp CRC and resulted in CEA responses but not radiographic responses. PFS and OS compare favorably to historical controls in this small cohort. CEA responses were not observed with PD1 monotherapy in MMRp CRC, suggesting GVAX can modulate the antitumor immune response. Clinical trial information: NCT02981524.

A KRAS mutation is associated with an immunosuppressive tumor microenvironment in mismatch-repair proficient colorectal cancer.

609 Background: KRAS-mutant (KRASmut) colorectal cancers (CRCs) are associated with worse prognosis and resistance to therapy. We have previously shown that KRASmut CRCs have different transcriptomic signature of stromal and immune-related genes compared to KRAS-wild type (KRASwt) tumors. Here, we validated the immune-related changes in the tumor microenvironment associated with the KRAS mutation in CRC to guide the design of novel immunotherapy strategies. Methods: The expression of different immune markers (T cells, B cells, macrophages, natural killer cells, and immune check ligands) were assessed using multiplex immunofluorescence (M-IF) technique in both tumor core (TC) and invasive margin (IM). Sequential slides were cut from paraffin blocks of CRC resected at our institute. Each slide was stained with 4 immune markers using M-IF technique. The stained slides were scanned, and quantification of immune cells was done using ImageJ software. Student’s t test was used for statistical analyses. DNA was extracted from each tumor and profiled for 420 cancer genes using targeted exome-capture sequencing (MSK-IMPACT assay). DNA mismatch-repair (MMR) proteins deficiency were analyzed by immunohistochemistry. Only MMR-proficient (pMMR) tumors were included. Results: A total of 39 patients with pMMR CRC were included. AJCC stages (I-III) were not different between KRASmut (n = 15) and KRASwt (n = 25) tumors. M2-macrophages (CD68+CD163+ cells) and IL-17-producing cells (IL17+ cells) were significantly higher (p = 0.002, and 2.9e-6 respectively), while T-helper cells (CD3+CD4+cells) were significantly lower (p = 3.9e-4) in TC of KRASmut tumors compared to KRASwt. Treg (CD3+CD4+FOXP3+cells) were significantly higher in IM of KRASmut tumors (p = 0.01). KRASmut tumors had significantly higher ratios of Treg:T-helper cells, and Treg:T cytotoxic cell (p = 0.008, and p = 0.04; respectively). Conclusions: KRAS oncogene is associated with more pro-tumorigenic (M2 macrophages, IL17 and Treg) and less anti-tumorigenic (CD4 T-helper) immune cells in CRC. These results can be used to guide further research to design novel immunotherapy strategies against KRASmut CRC.

Expression of secreted frizzled-related protein 4 in DNA mismatch repair-deficient and mismatch repair-proficient colorectal cancers

To investigate the expressions of secreted frizzled-related protein 4 (SFRP4) in stage Ⅱ DNA mismatch repair-deficient (dMMR) and mismatch repair- proficient (pMMR) colorectal cancers and explore their clinical significance. We collected fresh stage Ⅱ colon cancer tissues with different MMR status detected by immunohistochemistry (IHC). The differentially expressed mRNAs between dMMR and pMMR tumors were identified by Affymetrix Human oeLncRNA gene chip, and the expression of SFRP4 in these cancer tissues and in colorectal cancer cell lines were detected using Western blotting and real- time quantitative PCR. The apoptosis rates of HCT116 cells with and without siRNA- mediated transient SFRP4 knockdown were determined using flow cytometry. We further investigated the expression pattern of Ki-67 and its correlation with SFRP4 expression. Compared with pMMR colon cancer tissues or cells, both dMMR colon cancer tissues (P=0.014) and cells (P=0.0079) showed significantly increased expression of SFRP4, which was in negative correlation with Ki-67 (P=0.041). In HCT116 cells, transient SFRP4 knockdown resulted in decreased cell apoptosis, including both early apoptosis (P=0.003) and late apoptosis (P=0.024). Up-regulation of SFRP4 in dMMR stage Ⅱ colon cancer promotes apoptosis and inhibits proliferation of the cancer cells, and may improve the prognosis of dMMR colon cancer.

POLD1 and POLE Gene Mutations in Jewish Cohorts of Early-Onset Colorectal Cancer and of Multiple Colorectal Adenomas.

Germline mutations in the DNA polymerase genes POLD1 and POLE confer high risk for multiple colorectal adenomas and colorectal cancer. However, prevalence and the clinical phenotype of mutation carriers are still not fully characterized. The purpose of this study was to assess the prevalence of germline mutations and to describe the genotype-phenotype correlation in POLD1 and POLE genes in Jewish subjects with multiple colorectal adenomas and/or early-onset mismatch repair proficient colorectal cancers. This study is a comparison of genetic and clinical data from affected and control groups. The study was conducted at a high-volume tertiary referral center. The study cohort included 132 subjects: 68 with multiple colorectal adenomas and 64 with early-onset mismatch repair proficient colorectal cancers. The control group included 5685 individuals having no colorectal cancer or colorectal adenomas. Study and control subjects were tested for POLD1 and POLE mutations and a clinical correlation was assessed. Eleven of the 132 study subjects (8.3%) carried either a POLD1 or a POLE mutation: 7 of 68 (10.3%) subjects with multiple colorectal adenomas and 4 of 64 (6.2%) subjects with early-onset mismatch repair proficient colorectal cancer. Three mutations were detected, showing statistical significance in frequency between study and control groups (p < 0.001). Eight of the 11 mutation carriers were Ashkenazi Jews carrying the same POLD1 mutation (V759I), implicating it as a possible low-to-moderate risk founder mutation. Phenotype of mutation carriers was notable for age under 50 at diagnosis, a propensity toward left-sided colorectal cancer, and extracolonic tumors (64%, 100%, and 27% of cases). The study cohort was limited by its relatively small size. Germline mutations in POLD1 and POLE were found to be relatively frequent in our Jewish cohorts. Further studies are needed to clarify the importance of POLD1 and POLE mutations and to define the most suitable surveillance program for Jewish and other POLD1 and POLE mutation carriers. See Video Abstract at http://links.lww.com/DCR/A658.

Immune checkpoint inhibitors for patients with colorectal cancer: mismatch repair deficiency and perspectives

Harnessing the immune system to fight tumor cells is becoming a promising and innovative therapeutic strategy for a large spectrum of malignancies. The evaluation of immunotherapy in the context of colorectal cancers (CRCs) has brought to light mismatch repair deficiency as a major predictive biomarker for the efficacy of immune checkpoint blockade. In this review, we summarize the promising results of immune checkpoint inhibitors for patients with metastatic CRCs harboring mismatch repair deficiency, with special emphasis on further clinical development. Given the biological determinants of sensitivity to immune checkpoint blockade, we will also elucidate points that could unlock the potential of immunotherapy for patients with mismatch repair-proficient CRC.

Prognostic implications of TAMs in colorectal cancer hepatic metastases.

3574 Background: A limited understanding of the immune microenvironment of mismatch repair-proficient metastatic colorectal cancer (mCRC) impedes efforts to develop effective immunotherapy treatments for the majority of CRC patients. Liver metastatic disease is common and associated with poor outcomes. While T-cell infiltration of liver metastases positively correlates with survival, most mCRC patients do not benefit from checkpoint-blockade therapy. Tissue associated macrophages (TAMs) have been associated with an immune suppressive environment, but their prognostic role in mCRC is largely unknown. Methods: Comprehensive analysis of gene expression and immunohistochemistry (IHC) in 25 microsatellite stable (MSS) untreated liver metastatectomy (LM) specimens was performed. Clinical outcomes including recurrence, immunologic data, and tumor microsatellite status were evaluated and correlated. Results: Principal component analysis of immune and cancer pathway related genes were performed and compared with recurrence status. All samples were confirmed MSS. There were distinct differences in gene expression between patients who remained disease free and those who recurred. Among immune related genes CXCL5, IRF4, IL6R, TNF, CTLA4, ICOS, and ARG1 were relatively over-expressed in non-recurrent tumors, while PPARG, AIRE, and EPCAM were over-expressed in recurrent tumors (FDR 0.2, p &lt; 0.05). Cibersort analysis predicts a significantly higher number of M2 versus M1 macrophages regardless of recurrence status (p &lt; 0.05), with an approximate M1:M2 ratio of 1:2 and a higher total number of M1/M2 macrophages in tumors that recur. On IHC, an average of 29% of cells per sample expressed macrophage marker CD68. Relatively fewer CD3, CD4, and CD8 T cells were observed with average infiltration rates of 7.4%, 3.6%, and 2.6% respectively. Conclusions: CRC liver metastases demonstrate evidence of a large TAM population with significant M2 component and a smaller T cell population. A greater number of TAMs appear to correlate with recurrence, while a more immunogenic phenotype correlates with lower recurrence risk.

Somatic POLE proofreading domain mutation, immune response, and prognosis in colorectal cancer: a retrospective, pooled biomarker study

Precision cancer medicine depends on defining distinct tumour subgroups using biomarkers that may occur at very modest frequencies. One such subgroup comprises patients with exceptionally mutated (ultramutated) cancers caused by mutations that impair DNA polymerase epsilon (POLE) proofreading. We examined the association of POLE proofreading domain mutation with clinicopathological variables and immune response in colorectal cancers from clinical trials (VICTOR, QUASAR2, and PETACC-3) and colorectal cancer cohorts (Leiden University Medical Centre 1 and 2, Oslo 1 and 2, Bern, AMC-AJCC-II, and Epicolon-1). We subsequently investigated its association with prognosis in stage II/III colorectal cancer by Cox regression of pooled individual patient data from more than 4500 cases from these studies. Pathogenic somatic POLE mutations were detected in 66 (1·0%) of 6517 colorectal cancers, and were mutually exclusive with mismatch repair deficiency (MMR-D) in the 6277 cases for whom both markers were determined (none of 66 vs 833 [13·4%] of 6211; p<0·0001). Compared with cases with wild-type POLE, cases with POLE mutations were younger at diagnosis (median 54·5 years vs 67·2 years; p<0·0001), were more frequently male (50 [75·8%] of 66 vs 3577 [55·5%] of 6445; p=0·0010), more frequently had right-sided tumour location (44 [68·8%] of 64 vs 2463 [39·8%] of 6193; p<0·0001), and were diagnosed at an earlier disease stage (p=0·006, χ2 test for trend). Compared with mismatch repair proficient (MMR-P) POLE wild-type tumours, POLE-mutant colorectal cancers displayed increased CD8+ lymphocyte infiltration and expression of cytotoxic T-cell markers and effector cytokines, similar in extent to that observed in immunogenic MMR-D cancers. Both POLE mutation and MMR-D were associated with significantly reduced risk of recurrence compared with MMR-P colorectal cancers in multivariable analysis (HR 0·34 [95% CI 0·11-0·76]; p=0·0060 and 0·72 [0·60-0·87]; p=0·00035), although the difference between the groups was not significant. POLE proofreading domain mutations identify a subset of immunogenic colorectal cancers with excellent prognosis. This association underscores the importance of rare biomarkers in precision cancer medicine, but also raises important questions about how to identify and implement them in practice. Cancer Research UK, Academy of Medical Sciences, Health Foundation, EU, ERC, NIHR, Wellcome Trust, Dutch Cancer Society, Dutch Digestive Foundation.

Characterisation of the oxysterol metabolising enzyme pathway in mismatch repair proficient and deficient colorectal cancer.

Oxysterols are oxidised derivatives of cholesterol, formed by the enzymatic activity of several cytochrome P450 enzymes and tumour-derived oxysterols have been implicated in tumour growth and survival. The aim of this study was to profile the expression of oxysterol metabolising enzymes in primary colorectal cancer and assess the association between expression and prognosis.Immunohistochemistry was performed on a colorectal cancer tissue microarray containing 650 primary colorectal cancers using monoclonal antibodies to CYP2R1, CYP7B1, CYP8B1, CYP27A1, CYP39A1, CYP46A1 and CYP51A1, which we have developed. Unsupervised hierarchical cluster analysis was used to examine the overall relationship of oxysterol metabolising enzyme expression with outcome and based on this identify an oxysterol metabolising enzyme signature associated with prognosis.Cluster analysis of the whole patient cohort identified a good prognosis group (mean survival=146 months 95% CI 127-165 months) that had a significantly better survival (δ2=12.984, p<0.001, HR=1.983, 95% CI 1.341-2.799) than the poor prognosis group (mean survival=107 months, 95% CI 98-123 months). For the mismatch repair proficient cohort, the good prognosis group had a significantly better survival (δ2=8.985, p=0.003, HR=1.845, 95% CI 1.227-2.774) than the poor prognosis group. Multi-variate analysis showed that cluster group was independently prognostically significant in both the whole patient cohort (p=0.02, HR=1.554, 95% CI 1.072-2.252) and the mismatch repair proficient group (p=0.04, HR=1.530, 95% CI 1.014-2.310).Individual oxysterol metabolising enzymes are overexpressed in colorectal cancer and an oxysterol metabolising enzyme expression profile associated with prognosis has been identified in the whole patient cohort and in mismatch repair proficient colorectal cancers.

Association of a let-7 miRNA binding region of TGFBR1 with hereditary mismatch repair proficient colorectal cancer (MSS HNPCC).

The purpose of this study was to identify novel colorectal cancer (CRC)-causing alleles in unexplained familial CRC cases. In order to do so, coding regions in five candidate genes (MGMT, AXIN2, CTNNB1, TGFBR1 and TGFBR2) were sequenced in 11 unrelated microsatellite-stable hereditary non-polyposis CRC (MSS HNPCC) cases. Selected genetic variants were genotyped in a discovery set of 27 MSS HNPCC cases and 85 controls. One genetic variant, rs67687202, in TGFBR1 emerged as significant (P = 0.002), and it was genotyped in a replication set of 87 additional MSS HNPCC-like cases and 338 controls where it was also significantly associated with MSS HNPCC cases (P = 0.041). In the combined genotype data, rs67687202 was associated with a moderate increase in CRC risk (OR = 1.68; 95% CI = 1.13-2.50; P = 0.010). We tested a highly correlated SNP rs868 in 723 non-familial CRC cases compared with 629 controls, and it was not significantly associated with CRC risk (P = 0.370). rs868 is contained in a let-7 miRNA binding site in the 3'UTR of TGFBR1, which might provide a functional basis for the association in MSS HNPCC. In luciferase assays, the risk-associated allele for rs868 was associated with half the luciferase expression in the presence of miRNA let-7b-5p compared with protective allele, suggesting more binding of let-7b-5p and less TGFBR1 expression. Thus, rs868 potentially is a CRC risk-causing allele. Our results support the concept that rs868 is associated with lower TGFBR1 expression thereby increasing CRC risk.