Dados do Resumo

Título

Use of a molecular assay to detect microsatellite instability in an oncology referral hospital in the state of Amazonas

Introdução

Colorectal cancer (CRC) is characterized as a malignant neoplasm that arises in the large intestine. Around 80% of CRC cases are sporadic and approximately 20% are hereditary. CRC is considered a heterogeneous disease as a result of alterations in intestinal stem cells. Among the molecular markers studied, the observation of microsatellite instability (MSI) in CRC patients plays a crucial role in the clinical management and prognosis of this disease.

Objetivo

The aim of this study is to describe the use of a molecular assay to detect microsatellite instability in tumor samples from patients diagnosed with CRC adenocarcinom treated at the Amazonas State Oncology Control Center Foundation (FCecon).

Métodos

This is a descriptive analysis of the PCR technique and is part of the larger study entitled “Analysis of the molecular and clinical spectrum of colorectal cancer: from epidemiology and quality of life to genetics and omics analysis”, approved by the FCecon Ethics Committee (CAEE 52343821.2.0000.0004, opinion 5.180.654). Tumor tissue DNA was extracted using the Reliaprep gDNA Tissue Miniprep System kit (Promega). DNA quality and quantity were assessed by spectrophotometry and fluorometry. MSI loci were amplified by PCR and analyzed by capillary electrophoresis on the Applied Biosystems™ SeqStudio™ Genetic Analyzer. Using a panel of 13 markers from the True Mark™ MSI Assay Kit (BAT-25, NR-24, NR-2, BAT-40, CAT-25, NR-22, NR-27, ABI-19, ABI-20B, ABI-17, ABI-16, BAT-26, ABI-20A). The results were analyzed using MSI Analysis Software 1.0, classifying the samples as MSI-L (low instability), MSI-H (high) or MSS (stable), based on the percentage of instability of the markers.

Resultados

Six samples were analyzed, all of them female. Five showed the MSS phenotype and one, MSI-L in BAT-40. When compared with the Immunohistochemistry (IHC) results, the sample showed preservation of the DNA repair proteins (MLH1-PMS2-MSH2-MSH6), suggesting an absence of MSI phenotype. The concordance between IHC and TrueMark confirmed the MSS phenotype in all samples; however, the sample with MSI-L in TrueMark was classified as having no MSI phenotype by IHC, indicating a discrepancy between the methods. The MSI-L sample showed the tumor metastasized on the right side, while the others were on the left side of the intestine. As for the evolution of the patients, 5 are still undergoing neoadjuvant treatment and 1 died. Based on this and previous studies, we proposed that IHC and MSI PCR are complementary to each other, but the MSI TrueMark test plays a dominant role, allowing us to visualize loci not identified by IHC, corroborating a more favorable prognosis for the patient.

Conclusões

Despite the limitations due to the small sample size, this study suggests that the MSI test is crucial for categorizing CRC tumors into MSI-H, MSI-L and MSS. MSI-H tumors have the most favorable prognosis, making the MSI test a valuable prognostic marker. This study highlights the importance of MSI analysis in CRC and the effectiveness of the TrueMark™ kit to identify instability, such as in BAT-40. This advance could improve patient prognosis and reinforces the need for sensitive detection methods for clinical investigations and the development of personalized therapies.

Financiador do resumo

FAPEAM – Programa PAIC 23/24; EDITAL N. 002/2021 - PROGRAMA AMAZÔNIDAS; RESOLUÇÃO N. 002/2008, 007/2018 e 005/2019 - PRÓ-ESTADO REDE GENÔMICA DE VIGILÂNCIA EM SAÚDE: OTIMIZAÇÃO DA ASSISTÊNCIA E PESQUISA NO ESTADO DO AMAZONAS - REGESAM 002/2021 - PROGRAMA AMAZÔNIDAS; RESOLUÇÃO N. 002/2008, 007/2018 e 005/2019 - PRÓ-ESTADO REDE GENÔMICA DE VIGILÂNCIA EM SAÚDE: OTIMIZAÇÃO DA ASSISTÊNCIA E PESQUISA NO ESTADO DO AMAZONAS - REGESAM

Palavras Chave

Colorectal cancer; Microsatellite Instability; Molecular Test