Abstract 348: Development of an RNA based diagnostic panel to the tumor microenvironment to match cancer therapies for colorectal cancer
Kristen Strand-TibbittsKerry Culm-MerdekValerie Chamberlain SantpsLaura BenjaminJulia CarterLarry E. DouglassRoman LuštrikRobert CvitkovičLuka AusecRafael D. Rosengarten
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Abstract The most utilized targeted therapies in colorectal cancer (CRC) are focused on EGFR inhibition and anti-angiogenesis. In the ~5% of patients with microsatellite instability (MSI-H) or high tumor mutational burden (TMB), checkpoint inhibitors (CPIs) have been approved. Oncxerna has developed an RNA expression-based approach to characterize the ‘dominant' biology of a patient's tumor microenvironment with the diagnostic hypothesis to prospectively pair those patients with therapies and known mechanism of action that directly target these biologies. We developed an RNA-based gene expression panel (TME Panel-1) and machine learning (ML) algorithms to prospectively predict a patient's response to anti-angiogenesis or immune modulators, such as CPIs. In this study, we explore the potential of the TME Panel-1 to identify dominant biologies present in colorectal cancer specimens procured from the Wood-Hudson Cancer Research Lab. Total RNA expression counts from FFPE slides were analyzed with the ML algorithms and used to assign each sample into one of four subgroups. The respective prevalence of the subgroups are similar to those observed in gastric cancer and ovarian cancer samples, suggesting that the TME-Panel 1 has potential to be used to develop pan-tumor diagnostics. We will present these results, correlations with clinical outcomes and other relevant biomarkers for CRC. In summary, we conclude that RNA-based descriptors of biology may be a useful approach to enrich for better response to targeted therapies whose mechanism of action is to modify the TME biology. Citation Format: Kristen Strand-Tibbitts, Kerry Culm-Merdek, Valerie Chamberlain Santps, Laura Benjamin, Julia Carter, Larry Douglass, Roman Luštrik, Robert Cvitkovič, Luka Ausec, Rafael Rosengarten. Development of an RNA based diagnostic panel to the tumor microenvironment to match cancer therapies for colorectal cancer [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 348.Keywords:
Microsatellite Instability
In many countries, colorectal cancer is one of the common cancers. It has been confirmed that microsatellite instability (MSI) is one of the most important molecular changes in colorectal cancer. As the recognized precursor lesions of colorectal cancer, adenomas and some polyps also have MSI phenomenon. This article analyzes the MSI of colorectal cancer and its closely related adenomas and polyps in domestic and foreign literature, and further discusses how to identify colorectal cancer at an early stage and the impact of MSI on the prognosis and treatment of colorectal cancer.
Microsatellite Instability
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Microsatellite Instability
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Colorectal cancer is a heterogeneous disease with multiple epigenetic alterations and different molecular features. The molecular classification is based on 2 major distinct pathways: microsatellite stable pathway and the microsatellite instability pathway. Molecular profiling of colorectal cancer provides important information regarding treatment and prognosis. Aim of the study was to assess the frequency of microsatellite instability in colon cancer and the clinicopathological characteristics of the tumors with high level of microsatellite instability (MSI-H) in our region. The secondary outcome was to assess the frequency of v-raf murine sarcoma viral oncogene homolog B1 (BRAF) mutations in colon cancer.The study included 129 patients with colon cancer fit for surgery. Demographic data, clinical and pathological data, immunohistochemistry staining pattern (4 mismatch repair proteins were investigated), and BRAF gene mutations were assessed. According to microsatellite instability status by polymerase chain reaction, patients were divided into 3 groups: microsatellite stable (MSS) = 108 patients, high level of microsatellite instability (MSI-H) = 15 patients and low level of microsatellite instability (MSI-L) = 6 patients. Different clinicopathological comparisons between MSS and MSI-H patients, and between MSS and MSI-L patients were performed.Microsatellite instability was found in 16.3% patients: 11.6% had MSI-H and 4.7% had MSI-L. Significantly more patients in the MSI-H group than in the MSS group were female (P = .01) and had a family history of colon cancer (P < .001). MSI-H and MSI-L groups were associated with the ascending colon location of the tumors, were mostly type G3, T2, and stage I whereas MSS tumors were mostly G2, pT3, and stage III. Overall, BRAF mutations were identified in 18/129 patients (13.9%). BRAF mutant tumors were predominantly associated with MSI-H and MSI-L tumors. Immunohistochemistry had a sensitivity of 76% and a specificity of 89% in detecting MSI tumors and an accuracy of 87.6%.The frequency of microsatellite instability in our study was 16.3%. MSI-H is a distinct molecular phenotype of colon cancer with particular features: female gender, family history of colorectal cancer, a predilection for the ascending colon, poorly differentiated, predominantly T2, and stage I. The frequency of BRAF mutations was 13.9% and mutations were more often present in the MSI tumors.
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Widespread microsatellite instability (MSI) due to the defective DNA mismatch repair underlies the pathogenesis of the majority of hereditary non-polyposis colorectal cancer and a subset of various sporadic malignant tumors. Using 5 microsatellite markers and the criteria of MSI proposed by the National Cancer Institute (NCI) workshop, we analyzed 205 gastric adenocarcinomas for MSI. Based on the number of markers showing instability per tumor, the tumors were divided into three groups; those with two or more of the five markers displaying instability (high MSI, MSI-H), those with one of five markers displaying instability (low MSI, MSI-L), and those with no instability (microsatellite stable, MSS). Among 205 tumors, 30 (15%) were MSI-H. 15 (7%) were MSI-L, and 160 (78%) were MSS. All of the 30 MSI-H tumors demonstrated instability at BAT26, a sensitive marker for the widespread MSI, while none of the 15 MSI-L tumors did. MSI-H tumors were significantly associated with distal location and well or moderate differentiation, but MSI-H tumors were indistinguishable from MSS tumors. Bax frameshift mutations were detected in 60% of the 30 MSI-H tumors, while not in any of the 15 MSI-L tumors. These results suggest that microsatellite analysis using the criteria proposed by the NCI workshop may appropriate for gastric cancers because it unveils real differences in genotype and phenotype.
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Angiogenesis, a formation of neovessels, is regulated by the local balance between angiogenesis stimulators and inhibitors. A number of such endogenous regulators of angiogenesis have been found in the body. Recently, vasohibin-1 (VASH1) was isolated as a negative feedback regulator of angiogenesis produced by endothelial cells (ECs) and subsequently vasohibin-2 (VASH2) as a homologue of VASH1. It was then explored that VASH1 is expressed in ECs to terminate angiogenesis, whereas VASH2 is expressed in cells other than ECs to promote angiogenesis in the mouse model of angiogenesis. This review will focus on the vasohibin family members, which are novel regulators of angiogenesis.
Angiogenesis inhibitor
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Abstract Background Nearly 7 per cent of patients who undergo resection for colorectal cancer develop metachronous cancers several years later. A molecular marker that could identify patients susceptible to metachronous cancers would be of clinical importance. Methods Twenty-four colorectal cancers from 15 individuals with metachronous colorectal cancer were investigated for microsatellite instability at five loci by single stranded conformational polymorphism analysis. A control group of 14 colorectal cancers from individuals who had only developed one sporadic colorectal cancer each was analysed similarly. Results Microsatellite instability was demonstrated in 17 of 24 cancers from individuals with metachronous cancer compared with one of 14 cancers from individuals with a single colorectal cancer. Conclusion These results suggest that testing for microsatellite instability may be useful in recognizing patients at high risk of developing metachronous colorectal cancers.
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