Basic Study
Copyright ©The Author(s) 2021. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastrointest Oncol. Dec 15, 2021; 13(12): 2101-2113
Published online Dec 15, 2021. doi: 10.4251/wjgo.v13.i12.2101
MutL homolog 1 methylation and microsatellite instability in sporadic colorectal tumors among Filipinos
Loraine Kay D Cabral, Cynthia A Mapua, Filipinas F Natividad, Caecilia H C Sukowati, Edgardo R Cortez, Ma Luisa D Enriquez
Loraine Kay D Cabral, Cynthia A Mapua, Filipinas F Natividad, Ma Luisa D Enriquez, Research and Biotechnology Group, St. Luke's Medical Center, Quezon City 1112, Philippines
Loraine Kay D Cabral, Caecilia H C Sukowati, Centro Studi Fegato, Fondazione Italiana Fegato ONLUS, Trieste 34149, Italy
Edgardo R Cortez, Department of Surgery, St. Luke's Medical Center, Quezon City 1112, Philippines
Ma Luisa D Enriquez, Center for Natural Science and Environmental Research, De La Salle University, Manila 1004, Philippines
Author contributions: Enriquez MLD conceptualized the project; Cabral LKD designed and optimized the experiments; Mapua CA screened data of the colorectal cancer databank and performed statistical analysis; Cabral LKD and Sukowati CHC analyzed data and wrote the manuscript; Cortez ER and Natividad FF coordinated specimen collection and funds allocation as study group head and division head respectively; all authors read and approved the manuscript.
Supported by Department of Science and Technology and the Philippine Council for Health Research and Development (DOST-PCHRD) (to Cabral LKD); St. Luke’s Medical Center, Manila, Philippines; and Regione Autonomo FVG in Progetti Internazionali 2021 to the FIF, No. DGR 189 dd 12/2/21.
Institutional review board statement: The clinical study protocol and the revised clinical study protocol (Ref. No. 06-015) had been approved by the St. Luke's Medical Center Institutional Ethics Review Board.
Conflict-of-interest statement: All authors declared that they have no conflicts of interest.
Data sharing statement: The authors may share the data for justified reason.
Open-Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/Licenses/by-nc/4.0/
Corresponding author: Loraine Kay D Cabral, BSc, MSc, Research Associate, Research and Biotechnology Group, St. Luke's Medical Center, 279 E Rodriguez Sr. Avenue, Quezon City 1112, Philippines. kay.cabral@fegato.it
Received: May 11, 2021
Peer-review started: May 11, 2021
First decision: June 12, 2021
Revised: June 24, 2021
Accepted: September 14, 2021
Article in press: September 14, 2021
Published online: December 15, 2021
Abstract
BACKGROUND

Colorectal cancer (CRC) ranks third in terms of incidence and second in mortality worldwide. In CRC, the silencing of mismatch repair genes, including the mutL homolog 1 (hMLH1) has been linked to microsatellite instability (MSI), the lengthening or shortening of microsatellite repeats. Very limited data have been presented so far on the link of hMLH1 methylation and MSI in Southeast Asia populations with sporadic CRC, and on its clinical significance.

AIM

To investigate the significance of the MSI status and hMLH1 methylation in CRC Filipino patients.

METHODS

Fifty-four sporadic CRC patients with complete clinical data were included in this study. Genomic DNA from CRC tumor biopsies and their normal tissue counterparts were profiled for MSI by high resolution melting (HRM) analysis using the Bethesda Panel of Markers (BAT25, BAT26, D2S123, D5S346, and D17S250). hMLH1 methylation screening was performed using bisulfite conversion and methylation specific polymerase chain reaction. Statistical analysis was conducted to calculate their associations to clinicopathological characteristics and survival relevance (Kaplan-Meier curves and the log-rank test).

RESULTS

hMLH1 methylation was observed in 9% and 35% of CRC and normal samples, respectively. Higher incidence of consistently methylated hMLH1 found in both normal and CRC was noticed for relation to location of tumor (P < 0.05). As for MSI status, D2S123 the most common unstable microsatellite and MSI-high (MSI-H) was the most common MSI profile, counted for 46% and 50% of normal and CRC tissues, respectively. The presence of MSI-low (MSI-L) and microsatellite stable (MSS) was 43% and 11% for normal, and 31% and 19% for CRC samples. The mean month of patients’ survival was shorter in patients whose normal and tumor tissues had methylated compared to those with unmethylated hMLH1 and with MSI-H compared to those with MSI-L/MSS (P < 0.05). This was supported by significant difference in Kaplan-Meier with log-rank analysis. This data indicated that hMLH1 methylation and high MSI status have prognostic value.

CONCLUSION

This study showed the clinical significance of hMLH1 methylation and MSI status in sporadic CRC Filipino patients, especially in the normal part of the tumor.

Keywords: Sporadic colorectal cancer, DNA methylation, Microsatellite instability, Population genetic, Colorectal cancer

Core Tip: Colorectal cancer (CRC) ranks third in terms of incidence and second in mortality worldwide. In CRC, the silencing of mismatch repair genes, including the mutL homolog 1 (hMLH1) has been linked to microsatellite instability (MSI). This study investigated the status of hMLH1 methylation and MSI in normal and tumor tissues of Filipinos sporadic CRC patients and their clinical significances.