Microsatellite Instability-high Colorectal Cancer Research Articles

Gene mutation profiling in microsatellite instability colorectal cancer and its association with the efficacy of immunotherapy: A retrospective study.

Microsatellite instability-high (MSI-H) colorectal cancer (CRC) is known for its heightened responsiveness to immunotherapy. However, establishing robust predictive markers for immunotherapy efficacy remains imperative. This retrospective study aimed to elucidate the genetic landscape of MSI-H CRC and correlate these genetic alterations with immunotherapy outcomes in a cohort of 121 patients. We analyzed clinical and molecular data from 121 patients with MSI-H CRC. We conducted a thorough genetic analysis of MSI-H CRC patients, with a specific emphasis on the APC, TP53, RAS, and MMR genes. We further analyzed the relationship between gene mutations and immunotherapy efficacy. The primary endpoints analyzed were objective response rate (ORR) and progression-free survival (PFS). All statistical analysis was conducted using SPSS26.0 and R 4.2.0 software. Our findings underscored the complexity of the genetic landscape in MSI-H CRC, shedding light on the intricate interplay of these genes in CRC development. Notably, mutations in MMR genes exhibited a distinctive pattern, providing insights into the underlying mechanisms of MSI-H. Furthermore, our results revealed correlations between specific genetic alterations and immunotherapy outcomes, with a particular focus on treatment response rates and progression-free survival. This study represents a significant step toward unraveling the genetic nuances of MSI-H CRC. The distinctive pattern of MMR gene mutations not only adds depth to our understanding of MSI-H CRC but also hints at potential avenues for targeted therapies. This research sets the stage for future investigations aimed at refining therapeutic strategies and improving outcomes for patients with MSI-H CRC.

Chemoproteomic discovery of a covalent allosteric inhibitor of WRN helicase.

WRN helicase is a promising target for treatment of cancers with microsatellite instability (MSI) due to its essential role in resolving deleterious non-canonical DNA structures that accumulate in cells with faulty mismatch repair mechanisms1-5. Currently there are no approved drugs directly targeting human DNA or RNA helicases, in part owing to the challenging nature of developing potent and selective compounds to this class of proteins. Here we describe the chemoproteomics-enabled discovery of a clinical-stage, covalent allosteric inhibitor of WRN, VVD-133214. This compound selectively engages a cysteine (C727) located in a region of the helicase domain subject to interdomain movement during DNA unwinding. VVD-133214 binds WRN protein cooperatively with nucleotide and stabilizes compact conformations lacking the dynamic flexibility necessary for proper helicase function, resulting in widespread double-stranded DNA breaks, nuclear swelling and cell death in MSI-high (MSI-H), but not in microsatellite-stable, cells. The compound was well tolerated in mice and led to robust tumour regression in multiple MSI-H colorectal cancer cell lines and patient-derived xenograft models. Our work shows an allosteric approach for inhibition of WRN function that circumvents competition from an endogenous ATP cofactor in cancer cells, and designates VVD-133214 as a promising drug candidate for patients with MSI-H cancers.

Abstract ND11: Chemoproteomic-enabled discovery of VVD-214, a synthetic lethal allosteric inhibitor of WRN helicase

Abstract WRN helicase is a promising target for treating cancers with microsatellite instability (MSI) due to its essential role in resolving deleterious non-canonical DNA structures that accumulate in cells with faulty mismatch repair mechanisms. Currently, there are no approved drugs directly targeting human DNA or RNA helicases, in part due to the challenging nature of developing potent and selective compounds to this class of proteins. Here we describe the chemical proteomic-enabled discovery of a clinical-stage, covalent allosteric inhibitor of WRN. The clinical lead, VVD-214, covalently engages cysteine 727 of WRN in a nucleotide cooperative manner and inhibits ATP hydrolysis and helicase activity, resulting in widespread double-stranded DNA breaks, nuclear swelling, and cell death in MSI-high, but not microsatellite stable cells. VVD-214 provided robust tumor regression in multiple MSI-high colorectal cancer cell lines and patient derived xenograft models, including models derived from patients progressing on immune checkpoint therapies. VVD-214 was exceptionally well tolerated, and constitutes a promising oral drug candidate for patients with MSI-high cancers. Citation Format: Shota Kikuchi, Piergiorgio Pettazzoni, Kristen A. Baltgalvis, Kelsey N. Lamb, Kent T. Symons, Chu-Chiao Wu, Melissa A. Hoffman, Aaron N. Snead, Xiaodan Song, Thomas Glaza, Jason C. Green, Donald C. Rogness, Betty Lam, Maria E. Rodriguez-Aguirre, David R. Woody, Christie L. Eissler, Socorro Rodiles, Seth M. Negron, Steffen M. Bernard, Eileen Tran, Jonathan Pollock, Ali Tabatabaei, Victor Contreras, Heather N. Williams, Martha K. Pastuszka, John J. Sigler, Markus G. Rudolph, Moritz Classen, Doris Brugger, Christopher Claiborne, Jean-Marc Plancher, Isabel Cuartas, Joan Seoane, Laurence E. Burgess, Robert T. Abraham, David S. Weinstein, Gabriel M. Simon, Matthew P. Patricelli, Todd M. Kinsella. Chemoproteomic-enabled discovery of VVD-214, a synthetic lethal allosteric inhibitor of WRN helicase [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr ND11.

Transient TCR-based T cell therapy in a patient with advanced treatment-resistant MSI-high colorectal cancer

We previously demonstrated the anti-tumor effectiveness of transiently TCR redirected T cells recognizing a frameshift mutation in TGFβRII. We here describe a clinical protocol using mRNA TCR modified T cells to treat a patient with progressive, treatment-resistant metastatic MSI-H colorectal cancer. Following 12 escalating doses of autologous T cells electroporated with in vitro transcribed Radium-1 TCR mRNA we assessed T cell cytotoxicity, phenotype and cytokine production. Tumor markers and growth on CT scans were evaluated and immune cell tumor infiltrate at diagnosis assessed. At diagnosis tumor infiltrating CD8+ T cells had minimal expression of exhaustion markers, except for PD-1. Injected Radium-1 T cells were mainly naïve and effector memory T cells with low expression of exhaustion markers, except for TIGIT. We confirmed cytotoxicity of transfected Radium-1 T cells against target cells and found key cytokines involved in tumor metastasis, growth, and angiogenesis to fluctuate during treatment. The treatment was well tolerated, and despite his advanced cancer, the patient obtained a stable disease with 6 months' survival post treatment. We conclude that treatment of metastatic MSI-H colorectal cancer with autologous T cells electroporated with Radium-1 TCR mRNA is feasible, safe, well tolerated and warrants further investigation in a Phase I/II study.

The Expression Patterns of Immune Checkpoint Molecules in Colorectal Cancer: An Analysis Based on Microsatellite Status.

Recently, immunotherapy has arisen as a novel treatment approach for patients with colorectal cancer (CRC), but the effectiveness of immunotherapy varies in these patients. We hypothesized that immune checkpoint molecules (ICMs), which are the targets of immunotherapy, are often exhibited concomitantly. Our objective was to investigate the patterns of ICM expression in patients with CRC and the differences in ICM expression based on microsatellite instability status. The immunohistochemical expression of programmed cell death protein 1 (PD-1), programmed cell death ligand 1 (PD-L1), T cell immunoglobulin and mucin-domain containing-3 (TIM-3), and lymphocyte-activation gene 3 (LAG-3) in the tumor center and periphery was assessed in patients with non-metastatic colorectal cancer. We enrolled 83 patients with CRC: a total of 40 microsatellite-stable (MSS) and 43 microsatellite-instability-high (MSI-H) cancer patients. PD-L1 was more frequently expressed in the tumor center in the MSI-H patients with than that in the MSS patients (18 [41.9%] vs. 3 [7.5%], respectively; p < 0.001), and the same trend was observed for TIM-3 expression (30 [69.8%] vs. 19 [47.5%], respectively; p = 0.047). The concomitant expression of two or more ICMs was more frequently observed than no expression or the expression of a single molecule in both the MSS and MSI-H groups; a total of 34 (79.7%) patients with MSI-H cancer and 23 (57.5%) with MSS cancer showed ICM expression at the tumor center, whereas 34 (79.7%) patients with MSI-H cancer and 22 (55%) with MSS cancer showed expression at the tumor periphery. Patients with the genetic characteristics of MSI-H cancer showed higher expression levels of ICMs than those in patients with MSS cancer, and predominantly, two or more ICMs were concurrently expressed. Our findings highlight the potential efficacy of the dual-blockade approach in immunotherapy, particularly in patients with MSI-H CRC.

Microsatellite instability is highly prevalent in older patients with colorectal cancer.

Clinical guidelines suggest screening of colorectal cancer (CRC) for microsatellite instability (MSI). However, microsatellite instability-high (MSI-H) CRC is not rare in older patients. This study aimed to investigate the prevalence of MSI-H CRC in an unselected population in an age-based manner. A retrospective analysis of data from patients undergoing radical surgery for CRC was performed. Only cases with results from MSI testing using immunochemistry (IHC) were analyzed. Age-based analyses were performed using two cut-off ages: 50 years. as stated in Amsterdam II guidelines, and 60 years. as outlined in the revised Bethesda criteria. The study population included 343 (146 female and 197 male) patients with a median age of 70 years (range 21-90 years). The prevalence of MSI-H tumors in the entire cohort was 18.7%. The prevalence of MSI-H CRC was 22.5% in the group ≤50 years vs. 18.2% in the group >50 years using the age limit in the Amsterdam II guidelines. MSI-H CRC was present in 12.6% of the group aged ≤60 years compared to 20.6% in the control group >60 years. MSI screening of CRC based on age alone is associated with negative selection of a relevant number of cases. MSI-H CRC is also common in elderly patients, who may be negatively selected secondary to an age-based screening algorithm. Following the results of this study, screening based on clinical criteria should be omitted in favor of systematic screening as is already internationally practiced.

Abstract 5533: The difference of immune microenvironment betweende novometastatic and non-metastatic microsatellite instability-high colorectal cancer

Abstract Introduction: Microsatellite instability-high (MSI-H) colorectal cancer (CRC) consists of 15% of all CRC but only 2-4% of metastatic CRC. The favorable prognosis of non-metastatic (early-stage) MSI-H CRC may be related to vigorous immune reaction in tumor microenvironment. However, the mechanisms of immune evasion in metastatic (late stage) MSI-H CRC are largely unknown. Materials and Methods: We retrospectively collected patients with MSI-H CRC from National Taiwan University Hospital and Kaohsiung Chang Gung Memorial Hospital. The archival tumor specimens were used for immune cells analysis by Nanostring PanCancer Immune Panel, and spatial immune characterization by multiplex immunofluorescence stains. Only surgical resected primary tumors and metastatic tumors were included. Gene expression and immune cells composition were compared between non-metastatic and de novo metastatic tumors. Results: We enrolled 59 and 27 patients with early-stage and late-stage MSI-H CRC, respectively. Twelve metastatic site tumors were also collected. The clinicopathologic characteristics between patients who have early- and late-stage MSI-H CRC were not significantly different. There are heterogeneous immune cell compositions in these 98 MSI-H tumors. Compared to early-stage MSI-H tumors, there are significantly fewer cytotoxic (difference -0.497, p = 0.001) and dendritic cells (difference -0.528, p = 0.021) in late-stage MSI-H tumors. Gene set enrichment analysis disclosed significantly decrease in the expression of JAK-STAT-IFN-γ- and antigen processing-related pathways in late-stage MSI-H tumors. The top 5 genes with significantly differential expression between late-stage and early-stage tumors are C7, TNFRSF12A, MFGE8(up-regulated) and CXCL5, IFNL1, GZMH, HMGB1 and CXCR1 (down-regulated). Conclusions: There are significantly fewer cytotoxic and dendritic cells in late-stage MSI-H CRC, compared to early-stage MSI-H CRC, which is associated with decrease expression in JAK-STAT-IFN-γ- and antigen processing-related pathways. Citation Format: Kuo-Hsing Chen, Chia-Lang u Hs, Yu-Li Su, Chang-Tsu Yuan, Jia-Huei Tsai, Yi-Hsin Liang, Ann-Lii Cheng, Kun-Huei Yeh. The difference of immune microenvironment betweende novometastatic and non-metastatic microsatellite instability-high colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5533.

Imaging-guided prognostic score-based approach to assess the benefits of combotherapy versus monotherapy with immune checkpoint inhibitors in metastatic MSI-H colorectal cancer patients

BackgroundThis retrospective study determined survival responses to immune checkpoint inhibitors (ICIs), comparing mono- (mono) and combo-immunotherapy (combo) in patients with microsatellite instability-high (MSI-H) metastatic colorectal cancer (mCRC) by analyzing quantitative imaging data and clinical factors. MethodsOne hundred fifty patients were included from two centers and divided into training (n = 105) and validation (n = 45) cohorts. Radiologists manually annotated chest-abdomen-pelvis computed tomography and calculated tumor burden. Progression-free survival (PFS) was assessed, and variables were selected through Recursive Feature Elimination. Cutoff values were determined using maximally selected rank statistics to binarize features, forming a risk score with hazard ratio-derived weights. ResultsIn total, 2258 lesions were annotated with excellent reproducibility. Key variables in the training cohort included: total tumor volume (cutoff: 73 cm3), lesion count (cutoff: 20), age (cutoff: 60) and the presence of peritoneal carcinomatosis. Their respective weights were 1.13, 0.96, 0.91, and 0.38, resulting in a risk score cutoff of 1.36. Low-score patients showed similar overall survival and PFS regardless of treatment, while those with a high-score had significantly worse survivals with mono vs combo (P = 0.004 and P = 0.0001). In the validation set, low-score patients exhibited no significant difference in overall survival and PFS with mono or combo. However, patients with a high-score had worse PFS with mono (P = 0.046). ConclusionsA score based on total tumor volume, lesion count, the presence of peritoneal carcinomatosis, and age can guide MSI-H mCRC treatment decisions, allowing oncologists to identify suitable candidates for mono and combo ICI therapies.

Combining low-dose regorafenib with pembrolizumab for patients with MSI-H colorectal cancer: REGPEM-CRC-01.

TPS238 Background: Treatment for microsatellite instability-high (MSI-H)/mismatch repair deficient (MMR-D) colorectal cancer (CRC) has rapidly evolved in the last decade. The KEYNOTE 177 trial recently established pembrolizumab as a frontline therapy for patients with MSI-H CRC. However, in this study, approximately 40% of patients were noted to have disease progression within 6 months of treatment. Furthermore, an additional 10% of patients experienced acquired resistance to therapy. Therefore, there is an unmet need to improve outcomes for patients with MSI-H CRC. Preclinical studies have shown vascular endothelial growth factor (VEGF) signaling to be overactive in MSI-H compared to MSS CRC (Hansen et al. Colorectal Dis. 2011). Moreover, exploratory analysis of CALBG-80405 and PARADIGM trials showed that patients with MSI-H CRC were more likely to benefit from anti-VEGF therapy than those with MSS disease. Regorafenib, an FDA-approved agent for patients with mCRC, is a potent VEGF inhibitor with immune modulatory effects on the tumor microenvironment. We hypothesize that adding low-dose regorafenib to pembrolizumab as frontline therapy may create synergistic activity in addition to the known clinical activity of each agent in MSI-H CRC. Methods: In the lead-in arm of this prospective study, 22 patients will be enrolled. Patients will receive regorafenib 60 mg daily on days 1–14 (2 weeks on) followed by 7 days off (1 week off) in combination with pembrolizumab 200 mg in the cycle 1. In the following cycles, patients will receive regorafenib 90 mg daily for 2 weeks on 1 week off in combination with pembrolizumab 200 mg every 3 weeks. The primary outcome for the lead-in arm is overall response rate (ORR) within 12 months of treatment by RECIST 1.1. criteria. A formal one-sided hypothesis test will be conducted for futility, assuming that we will reject the null hypothesis of a target ORR only if we have strong evidence. In this study, we assume a null hypothesis that ORR is 0.60, which would reflect significant clinical improvement over the current standard of ORR = 0.43 from KEYNOTE 177. The alternative hypothesis is that ORR is less than 0.60. For the lead-in phase of the study, the emphasis is on controlling Type I error to be small, approximately 0.05. In the randomized phase of the study, patients will receive pembrolizumab monotherapy or pembrolizumab in combination with regorafenib 90 mg. The sample size for the randomized phase of trial was determined based on an assumed median of PFS of 28 months with pembrolizumab and regorafenib combination (investigational arm). The standard of care pembrolizumab monotherapy results in a median PFS of 16 months when given as a first-line therapy. We hypothesize the proposed treatment will increase median PFS to 28 months from 16 months (N=132; H0: 16 months vs., H1: 28 months; Type I error: 0.05, power 80%). Clinical trial information: NCT06006923 .

Outcomes with immunotherapy between Lynch syndrome vs non-Lynch syndrome microsatellite instability-high colorectal cancer.

175 Background: Alterations to mismatch repair (MMR) genes such as MLH1, MSH2, MSH6, and PMS2, can lead to microsatellite instability-high (MSI-H) tumors. MMR mutations can be inherited in Lynch syndrome (LS) but can also be a result of de novo alterations resulting in MSI-H malignancies. Treatment with immune checkpoint inhibitors (ICIs) have been shown to improve survival in such patients (pts) compared to systemic chemotherapy. However, there is a paucity of information in the literature with respect to outcomes of pts with germline vs somatic MMR mutations in MSI-H colorectal cancer (CRC). Furthermore, the presence of underlying BRAF mutation confers resistance to chemotherapy in pts with CRC, however data regarding outcomes with immunotherapy in such pts with MSI-H CRC is lacking. Methods: Pt records from the Mayo Clinic (AZ, MN, FL) between 2008-2023 denoted as MSI-H CRC, were included for retrospective review. Pt demographics, treatment courses, and genomic profiles were collected. Overall survival (OS) and progression-free survival (PFS) were estimated using the Kaplan-Meier method. Outcome differences between sub-groups were accessed with the log rank test and univariate analyses were assessed with Cox-regression. Results: A total of 81 pt records were identified (n = 18 LS, n = 63 non-LS). Stage IV disease was found in 28% of LS pts vs 59% of non-LS pts at diagnosis. Pembrolizumab was the most common ICI selected for metastatic CRC pts for both LS and non-LS pts (65% vs 94%) with median treatment duration for each group 11.7 vs 8.8 months. There were no differences in OS or PFS for any stage between LS vs non-LS. Median OS for all patients was 82 months. For all stage IV patients, median OS was 44 months, and median PFS was 19 months. Interestingly, for stage IV pts treated with immunotherapy, tumors that harbored BRAF V600E mutation (n = 21) vs BRAF wild type (n = 20) had a significantly lower median OS 19 vs 113 months (HR = 2.69, p = 0.043) as well as median PFS 12 vs 95 months (HR = 2.48, p = 0.041). Conclusions: In this study, we found that patient treated with ICIs have similar outcomes in the presence of germline vs. somatic MMR mutations in MSI-H CRC. The presence of an associated BRAF V600E mutation, which occurs in non-LS MSI-H CRC conferred worse outcomes.

Retrospective review of compliance with guideline-directed germline testing in microsatellite instability-high colorectal cancer treated at the Veterans Health Administration.

86 Background: Lynch syndrome (LS) is an autosomal dominant inherited cancer syndrome that confers an increased risk of colorectal cancer (CRC). As clinical and history features under-recognize LS cases (3-5% of CRC), universal screening of CRCs for LS is recommended. Patients whose CRCs are mismatch repair protein deficient (dMMR) and/or microsatellite instability high (MSI-H) are recommended to have subsequent genetics evaluation to screen for germline mutations. Confirmed LS changes cancer surveillance recommendations for affected patients and their relatives. Within Veterans Health Administration (VHA), GT is ordered by genetic counselors at genomic medicine telehealth centers (GMTC), after initial consultation. We aim to quantify rates at which CRC patients treated at the VHA complete germline testing (GT) when indicated. Methods: The electronic health records (EHRs) of VHA patients with known dMMR/MSI-H CRC were reviewed. Cases were extracted from both Veterans Affairs (VA) Puget Sound and referral VA MSI testing laboratories. Surgical pathology reports and clinical documentation were reviewed in Joint Longitudinal Viewer (JLV) to determine if GT was indicated and reason for non-testing, if not performed. Patients with known LS prior to development of CRC were excluded, and patients with dMMR in MLH1 or MSI-H with concurrent BRAFV600 mutation and/or MLH1 hypermethylation were considered to have sporadic CRC. Results: Of 110 patients with abnormal tumor LS screening; 39 (36%) patients’ tumor tissue underwent IHC for dMMR, 16 (14%) underwent PCR for MSI, and 55 (50%) had both. 45 (41%) patients were classified as somatic MSI-H. 65 (59%) patients met criteria for referral for GMTC and GT. Of these 65, 49 ultimately did not undergo GT and 16 did, which confirmed 4 cases of LS and revealed 1 variant of uncertain significance in the MLH1 gene. Reasons for non-testing were: 7 (14%) declined all cancer testing and treatment after CRC diagnosis or were lost to follow-up/declined establishment of cancer care, 3 (6%) declined referral to GMTC, 14 (29%) accepted referral to GMTC but never had consultation, 7 (14%) accepted referral to GMTC but declined GT when offered, and 18 (37%) were never offered GMTC referral or GT. Conclusions: A majority of dMMR/MSI-H cases with an indication for GT were referred for genetic counseling, but only a small subset completed testing. This analysis identified multiple areas for improvement, including a lack of recognition by providers for the need for GT, and lack of completion of testing by patients at multiple levels. Further evaluation of VHA-specific barriers is needed to improve the quality of delivered care.

Evaluation of mismatch-repair and microsatellite-instability status in a Chinese colorectal cancer Cohort

BackgroundImmunohistochemistry (IHC) and traditional polymerase chain reaction (PCR) are the methods of choice in clinical practice to identify the mismatch repair (MMR) and microsatellite instability (MSI) status in colorectal cancer (CRC). In some previous researches, the concordance rate between two methods was different and discordance existed in about 1 %–9.7 %. MethodsWe retrospectively reviewed 406 patients received surgical CRC resections and tests of both MMR IHC and MSI PCR from January 2019 to April 2022 in Shanghai Changzheng Hospital. The incidence of deficient mismatch repair (dMMR) or microsatellite instability-high (MSI-H) CRCs, the concordance rate between two methods, and the reasons for discordant results were evaluated with clinicopathological data, immunochemical staining, whole-exome sequencing, and MLH1 methylation analysis. ResultsAmong 406 patients, the incidence of MSI-H CRCs was 7.88 %. Nearly a quarter of the cases under reexamination of IHC was initial misinterpreted. Besides, the concordance rate between MMR IHC and MSI PCR was 99.26 % (401 of 404) and the Kappa value was 0.945 (p < 0.001). Finally, some somatic variants of MMR and POLE genes which may explain the discordance were identified. ConclusionThe incidence rate of MSI-H in Chinese patients with CRC might be relatively low owing to tumor location. Although MSI and IHC analyses are highly concordant, both MMR IHC and MSI PCR tests should be simultaneously performed and MMR IHC should be interpreted by experienced pathologists. In the future, further studies on discordant results should be carried out to improve the personalized management of CRC.

Clinical-Molecular characteristics and Post-Translational modifications of colorectal cancer in north China: Implications for future targeted therapies

This study delineated the elucidate molecular changes and their post-translational modifications (PTMs) in heterogenetic colorectal cancer (CRC) for a deeper understanding of the CRC pathophysiology and identifying potential therapeutic targets. In this retrospective study, the profiles of 13 hot spot gene mutations were analyzed and the microsatellite instability (MSI) status was determined.Employing the Circulating Single-Molecule Amplification and Resequencing Technology (cSMART) assay, the clinical-pathological features of CRC were characterized in 249 Chinese patients. PTMs were quantified online.Among the patients with CRC, the mutation frequencies of KRAS, NRAS, BRAF, PIK3CA, TP53, and APC genes were 47.8%, 3.6%, 4.8%, 13.7%, 55.8%, and 36.9%, respectively. The proportion of MSI-high (MSI-H) was 7.8%.Subsequent multiple logistic regression analysis showed significant associations including a link between lung metastasis and KRAS mutation, between liver metastasis and lymph node metastasis, between MSI-H and early-onset CRC (EOCRC) and KRAS mutation, between right-sided colon cancer and peritoneal metastasis, and between PIK3CA mutation and PTEN mutation. Patients with KRAS mutation presented with MSI-H, lung metastasis, and PIK3CA mutation. MSI-H, BRAF mutation, and PTEN mutation were more frequent in EOCRC. Phosphorylation and ubiquitylation were found in KRAS, BRAF, PTEN, and SMAD4; SUMOylation and ubiquitylation were observed in HRAS and NRAS; while phosphorylation was obvious in APC, P53, and MLH1. Notably, Phosphorylation and ubiquitylation were the two most common PTMs. The biological characteristics of CRC in Chinese patients have some unique clinical features, which can be explained by the genetic mutation profile, correlations among gene mutations and clinical characteristics. These distinctions set the Chinese patient population apart from their Western counterparts.

Immune checkpoint inhibitors for patients with microsatellite instability-high colorectal cancer: protocol of a pooled analysis of clinical trials.

Colorectal cancer (CRC) is the third most common cause of cancer and the second leading cause of cancer-related deaths worldwide. Microsatellite instability-high (MSI-H) is a distinct molecular subtype of CRC that occurs in approximately 15% of all cases. Recently, immune checkpoint inhibitors (ICIs) have emerged as a promising therapeutic approach for patients with MSI-H colorectal cancer, exhibiting higher response rates than standard chemotherapies. To assess the effectiveness and safety of ICIs for the treatment of patients with MSI-H CRC, we propose a comprehensive pooled analysis of clinical trial data. A systematic search of multiple electronic databases, including PubMed, EMBASE, Cochrane Library, and Clinicaltrials.gov, will be conducted from their inception until September, 2023 to identify eligible randomized controlled trials (RCTs) and non-randomized studies. Inclusion criteria comprise studies of adult patients with histologically confirmed MSI-H CRC treated with immune checkpoint inhibitors, with a comparison to a control group receiving conventional therapies. Outcomes of interest will be overall survival (OS), progression-free survival (PFS), objective response rate (ORR), disease control rate (DCR), and incidence of treatment-related adverse events (AEs). The Cochrane Risk of Bias tool and the Risk of Bias in Non-randomized Studies of Interventions (ROBINS-I) tool will be employed to evaluate the methodological quality of included studies. A random-effects model using the DerSimonian and Laird method will be applied for pooling the effect estimates, calculating hazard ratios (HRs) or risk ratios (RRs) with their corresponding 95% confidence intervals (CIs). Heterogeneity will be assessed using I² statistics, and subgroup analysis and meta-regression will be performed to explore potential effect modifiers in case of substantial heterogeneity. Publication bias will be evaluated with funnel plots and Egger's test. Sensitivity analysis will be conducted to assess the robustness of the results. This meta-analysis will synthesize available evidence from clinical trials on immune checkpoint inhibitors in treating MSI-H colorectal cancer. The findings will offer valuable information about the effectiveness and safety of ICIs in this patient population, contributing to the refinement of clinical guidelines and enhancing the decision-making process for healthcare providers, policy-makers, and patients. The comprehensive analysis of subgroups and sensitivity allows for an in-depth understanding of potential effect modification, providing essential directions for future research. This study will involve the use of published data; hence, ethical approval is not required. The results of the study will be disseminated through publications in peer-reviewed journals and presentations at relevant conferences. The findings will potentially impact clinical decision-making and contribute to the development of evidence-based treatment recommendations for patients with MSI-H colorectal cancer. Open Science Framework identifier, 10.17605/OSF.IO/ZHJ85.

Sustained Disease Control in Immune Checkpoint Blockade Responders with Microsatellite Instability-high Colorectal Cancer after Treatment Termination.

Outcomes for patients with MSI-H colorectal cancer stopping immunotherapy after disease control remain unknown. Sixty-four patients with MSI-H colorectal cancer from our institution stopping treatment for sustained benefit or toxicity were retrospectively assessed. After median follow up of 22 months and median immunotherapy exposure of 18 months, 88% patients remained without progression. All patients who recurred or progressed and were rechallenged with immunotherapy have continued to experience disease control.

Abstract B143: HRO761, a first-in-class, clinical stage WRN inhibitor with potent preclinical anti-tumor activity in MSIhigh models

Abstract Colorectal carcinoma (CRC) as well as other indications that have lost competence in mismatch repair and have a phenotype known as microsatellite instability (MSI), remain a significant unmet medical need. Large-scale functional genomics screens across cell line panels have identified the Werner Syndrome RecQ helicase (WRN) as being synthetic lethal with MSIhigh cancers. Thus, WRN inhibitors may offer a new therapeutic avenue in MSIhigh cancers. We report the preclinical characteristics of HRO761, a first-in-class, highly potent and selective inhibitor of WRN helicase, with optimized drug-like properties. We evaluated the pharmacokinetics and pharmacodynamics of HRO761 when administered orally once daily in MSIhigh and also assessed the efficacy as single agent across cell (CDX) and patient-derived (PDX) xenografts as well as in combination with irinotecan, a prodrug derivative of camptothecin which acts as topoisomerase I inhibitor. Daily oral administration of HRO761 was highly efficacious across the CDX and PDX models evaluated with a disease control rate of 70% across all indications. In the SW48 CDX model, tumor regression was sustained for 2 months at the highest dose followed by slow relapse. HRO761 also induced WRN degradation, activated the DNA damage response and induced p53 target genes in a dose dependent manner. In vitro combination with irinotecan deepened sensitivity to HRO761 with a more sustained response in MSIhigh CRC cell lines. Combining administration of HRO761 daily with irinotecan weekly was highly efficacious and beneficial over single agent in CDX and PDX models. In CDX models, the combination showed a robust benefit, translating into homogeneous, sustained regression leading to a dose-dependent tumor growth delay even after treatment discontinuation. Overall, we demonstrate that the novel, selective, first-in-class WRN inhibitor HRO761 is a promising therapeutic approach for the treatment of MSIhigh cancer patients either as single agent or in combination with irinotecan. Clinical development is currently ongoing to assess the safety, tolerability and preliminary anti-tumor activity in patients with MSIhigh colorectal cancer and other MSIhigh solid tumors [clinicaltrials.gov NCT05838768]. Citation Format: Stephane Ferretti, Isabel Jaco, Andrea Decker, Christelle Hemmerlin, Clemens Scheufler, Cornelia Quadt, Dario Sterker, Elena Gavioli, Eloisa Jimenez Nunez, Ernesta Dammassa, Fanny Schaeffer, Genevieve Albrecht, Giorgia Clementi, Hansjoerg Martus, Jacques Hamon, Juergen Hinrichs, Laurent Laborde, Marion Dourdoigne, Michele Moschetta, Ramona Stump, Rita Andraos-Rey, Sarah Welly, Stephanie Barbe, Vincent Romanet, Markus Reschke, Ruben De Kanter, Michael Jensen, Henrik Moebitz, Marta Cortes Cros. HRO761, a first-in-class, clinical stage WRN inhibitor with potent preclinical anti-tumor activity in MSIhigh models [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr B143.

Unraveling Resistance to Immunotherapy in MSI-High Colorectal Cancer.

Colorectal cancer (CRC) is the third most common cancer and the second leading cause of cancer-related deaths. Incidences of early CRC cases are increasing annually in high-income countries, necessitating effective treatment strategies. Immune checkpoint inhibitors (ICIs) have shown significant clinical efficacy in various cancers, including CRC. However, their effectiveness in CRC is limited to patients with mismatch-repair-deficient (dMMR)/microsatellite instability high (MSI-H) disease, which accounts for about 15% of all localized CRC cases and only 3% to 5% of metastatic CRC cases. However, the varied response among patients, with some showing resistance or primary tumor progression, highlights the need for a deeper understanding of the underlying mechanisms. Elements involved in shaping the response to ICIs, such as tumor microenvironment, immune cells, genetic changes, and the influence of gut microbiota, are not fully understood thus far. This review aims to explore potential resistance or immune-evasion mechanisms to ICIs in dMMR/MSI-H CRC and the cell types involved, as well as possible pitfalls in the diagnosis of this particular subtype.

Subclonal accumulation of immune escape mechanisms in microsatellite instability-high colorectal cancers.

Intratumor heterogeneity (ITH) in microsatellite instability-high (MSI-H) colorectal cancer (CRC) has been poorly studied. We aimed to clarify how the ITH of MSI-H CRCs is generated in cancer evolution and how immune selective pressure affects ITH. We reanalyzed public whole-exome sequencing data on 246 MSI-H CRCs. In addition, we performed a multi-region analysis from 6 MSI-H CRCs. To verify the process of subclonal immune escape accumulation, a novel computational model of cancer evolution under immune pressure was developed. Our analysis presented the enrichment of functional genomic alterations in antigen-presentation machinery (APM). Associative analysis of neoantigens indicated the generation of immune escape mechanisms via HLA alterations. Multiregion analysis revealed the clonal acquisition of driver mutations and subclonal accumulation of APM defects in MSI-H CRCs. Examination of variant allele frequencies demonstrated that subclonal mutations tend to be subjected to selective sweep. Computational simulations of tumour progression with the interaction of immune cells successfully verified the subclonal accumulation of immune escape mutations and suggested the efficacy of early initiation of an immune checkpoint inhibitor (ICI) -based treatment. Our results demonstrate the heterogeneous acquisition of immune escape mechanisms in MSI-H CRCs by Darwinian selection, providing novel insights into ICI-based treatment strategies.

Relationship Between ABO Blood Group and Microsatellite Instability in Colorectal Cancer: A Retrospective Single-Center Study.

Colorectal cancer (CRC) is the second most common cancer in both women and men. Microsatellite instability-high (MSI-H) CRC is a molecular subgroup and has distinct clinical and pathologic features from microsatellite stable (MSS) CRC. Studies have suggested an association between hereditary antigens in ABO blood group system and the risk of developing various cancers but the relationship between blood groups and MSI-H CRC has not been investigated. This study aimed to investigate this relationship and its possible effect on clinicopathological features in patients with CRC. This is a retrospective cross-sectional single-center study including pathology-confirmed CRC patients. Demographic and clinicopathological features, blood groups, and microsatellite status were examined among two groups. Microsatellite instability was examined by immunohistochemistry (IHC) in pathology specimen. A total of 144 patients, 72 patients with MSI-H CRC and 72 patients with MSS CRC, were included in the study. Among all patients, median age was 61.7 ± 12.9 (range 27-89) and 57.6% were male. MSI-H and MSS groups were similar in terms of age, gender distribution, and comorbidities. Patients with MSI-H CRC had significantly common O-blood group than control group (44.4% vs 18.1%, p: 0.001). In multivariate analysis, O-blood group was 4.2 times more common in the MSI-H patient group (95% CI: 1.514-11.819, p: 0.006). Also patients with MSI-H CRC were found to have significantly more right-sided, high-grade tumors and early-stage disease. MSI-H CRC is an important subgroup in colon cancer with different molecular and clinicopathological features. It was observed that O-blood group was 4.2 times more common in MSI-H CRC. We believe that clarifying the relationship between microsatellite instability and O-blood group and its possible genetic and epigenetic mechanismsin larger studies will enable us to better understand tumor behavior and prognosis, also affect our treatment choices of these patient groups.

Characterizing the landscape of RING-type E3 ubiquitin transferase-altered (RNF43 alt) colorectal cancer (CRC) and defining unique subsets with potential therapeutic vulnerabilities in microsatellite instability-high (MSI-H) CRC.

3134 Background: RNF43 is a tumor suppressor gene that represses the WNT/β-catenin pathway. Emerging data show that RNF43 alt are commonly present in MSI-H CRC with improved outcomes to immune checkpoint inhibitors (ICI). We evaluated whether genomic and transcriptomic analysis of MSI-H RNF43 alt CRC defines distinct subsets with potential therapeutic vulnerabilities. Methods: We analyzed CRC tumors (any stage/ subtype) sequenced with Tempus xT assay (DNA-seq of 648 genes at 500x coverage, full transcriptome RNA-seq). RNF43 alt were defined as pathogenic/likely pathogenic per OncoKB, or copy number aberrations (CNA); deep deletions, or amplifications (&gt;8x). RNF43 alt vs. wildtype (wt) were compared using Chi-squared/Fisher’s Exact tests or Wilcoxon rank-sum tests to evaluate differences in biomarkers. Gene Set Variation Analysis (GSVA) was applied to gene expression data to derive single-sample pathway enrichment scores. ICI-treated MSI-H CRC from the MSKCC cohort (n = 74), publicly available in AACR GENIE v13, was used to assess the overall survival (OS) using the Kaplan-Meier method. Results: RNF43 alt was identified in 5.2% (635 of 12,243) CRC tumors. CNA accounted for 6% of RNF43 alt CRC. RNF43 alt vs. RNF43 wt CRC was associated with older age (median 69 vs. 59 years, p &lt; 0.001), more prevalent in females (56% vs 43%; p &lt; 0.001). A detailed comparison of RNF43 alt vs. RNF43 wt CRC with p &lt; 0.001 are shown (Table). Of MSI-H CRC (n = 714), 51% were RNF43 alt, with 80% being RNF43 p.GLY659fs. Among MSI-H RNF43 alt CRC, BRAF alt was co-mutated in 59%, with BRAFV600E constituting 99%. Median TMB was higher for MSI-H RNF43 alt vs. MSI-H RNF43 wt (40 vs. 31 mut/MB, p &lt; 0.001). Among MSI-H CRC, GSVA identified significant downregulation of Cetuximab_benefit pathway and upregulation of IGF1R and PI3K/AKT pathways in RNF43 alt vs RNF43 wt. Among ICI-treated MSI-H CRC (n = 74) from the MSKCC cohort, no significant OS difference (HR 0.81 [95%CI: 0.34 – 1.97]; p = 0.65) was noted for RNF43 alt (n = 42) vs. wt (n = 32). Conclusions: RNF43 alt are common in MSI-H CRC and associated with potentially actionable genomic and transcriptomic signatures. Functional characterization of interplay between the WNT signaling and therapeutically relevant pathways (PI3K/AKT, BRAF, IGF1R, Cetuximab benefit) to better define optimal ICI combination approaches in MSI-H RNF43 alt CRC is ongoing. [Table: see text]