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Missense mutations in MLH1, MSH2, KRAS, and APC genes in colorectal cancer patients in Malaysia

Abdul Murad NA, Othman Z, Khalid M, Abdul Razak Z, Hussain R, Nadesan S, et al.

Dig Dis Sci, 2012 Nov;57(11):2863-72.
PMID: 22669205 DOI: 10.1007/s10620-012-2240-2

BACKGROUND: Colorectal cancer (CRC) is the third most common cancer worldwide with approximately 1 million cases diagnosed annually. In Malaysia, CRC is the second most common cancer in women and ranked first in men. The underlying cause of CRC remains unknown.
AIMS: The aim of this study was to analyze the mutations in genes involved in CRC including MLH1, MSH2, KRAS, and APC genes.
METHODS: A total of 76 patients were recruited. We used the polymerase chain reaction-denaturing high-performance liquid chromatography for the detection of mutations in the mismatch repair (MMR) and APC genes and the PCR single-strand conformation polymorphism for screening of the KRAS gene mutations.
RESULTS: We identified 17 types of missense mutations in 38 out of 76 patients in our patients. Nine mutations were identified in the APC gene, five mutations were detected in the KRAS gene, and two mutations were identified in the MSH2 gene. Only one mutation was identified in MLH1. Out of these 17 mutations, eight mutations (47 %) were predicted to be pathogenic. Seven patients were identified with multiple mutations (3: MSH2 and KRAS, 1: KRAS and APC, 1: MLH1 and APC, 2: APC and APC).
CONCLUSIONS: We have established the PCR-DHPLC and PCR-SSCP for screening of mutations in CRC patients. This study has given a snapshot of the spectrum of mutations in the four genes that were analyzed. Mutation screening in patients and their family members will help in the early detection of CRC and hence will reduce mortality due to CRC.

Matched MeSH terms: MutS Homolog 2 Protein/genetics
Fulltext Germline mutation analysis of MLH1 and MSH2 in Malaysian Lynch syndrome patients

Zahary MN, Kaur G, Abu Hassan MR, Singh H, Naik VR, Ankathil R

World J Gastroenterol, 2012 Feb 28;18(8):814-20.
PMID: 22371642 DOI: 10.3748/wjg.v18.i8.814

To investigate the protein expression profile of mismatch repair (MMR) genes in suspected cases of Lynch syndrome and to characterize the associated germline mutations.

Matched MeSH terms: MutS Homolog 2 Protein/genetics*
Microsatellite Instability and Altered Expressions of MLH1 and MSH2 in Gastric Cancer

Haron NH, Mohamad Hanif EA, Abdul Manaf MR, Yaakub JA, Harun R, Mohamed R, et al.

Asian Pac J Cancer Prev, 2019 Feb 26;20(2):509-517.
PMID: 30803214

Introduction: Microsatellite instability (MSI) is a hallmark of defective DNA mismatch repair (MMR) of genes
especially MLH1 and MSH2. It is frequently involved in the carcinogenesis of various tumours including gastric
cancer (GC). However, MSI in GCs have not been reported in Malaysia before. Objective: This study was conducted
to determine the microsatellite instability (MSI) status in gastric cancer by microsatellite analysis, sequencing, its
association with MLH1 and MSH2 protein expression and H.pylori infection by immunohistochemistry. Method:
A total of 60 gastric cancer cases were retrieved. DNA was extracted from paired normal and tumour tissues while
MLH1 and MSH2 protein expression as well as H. pylori status were determined by IHC staining. For microsatellite
analysis, polymerase chain reaction (PCR) was performed for paired tissue samples using a panel of five microsatellite
markers. MSI-positive results were subjected for DNA sequencing to assess mutations in the MLH1 and MSH2 genes.
Results: Microsatellite analysis identified ten MSI positive cases (16.7%), out of which only six cases (10.3%) showed
absence of MLH1 (n=3) or MSH2 (n=3) protein expression by IHC. The most frequent microsatellite marker in MSI
positive cases was BAT26 (90%). Nine of ten MSI positive cases were intestinal type with one diffuse and all were
located distally. H. pylori infection was detected in 13 of 60 cases (21.7%) including in three MSI positive cases. All
these results however were not statistically significant. Our sequencing data displayed novel mutations. However these
data were not statistically correlated with expression levels of MLH1 and MSH2 proteins by IHC. This may be due to
small sample size to detect small or moderately sized effects. Conclusion: The frequency of MSI in this study was
comparable with published results. Determination of affected MMR genes by more than two antibodies may increase
the sensitivity of IHC to that of MSI analysis.

Matched MeSH terms: MutS Homolog 2 Protein/genetics
Colorectal carcinoma in Malaysians: DNA mismatch repair pattern in a multiethnic population

Cheah PL, Looi LM, Teoh KH, Rahman NA, Wong LX, Tan SY

Asian Pac J Cancer Prev, 2014;15(7):3287-91.
PMID: 24815484

BACKGROUND: The interesting preponderance of Chinese with colorectal carcinoma (CRC) amongst the three major ethnic groups in Malaysia prompted a study to determine DNA mismatch repair (MMR) status in our CRC and attempt correlation with patient age, gender and ethnicity as well as location, grade, histological type and stage of tumour. Histologically re-confirmed CRC, diagnosed between 1st January 2005 and 31st December 2007 at the Department of Pathology, University of Malaya Medical Centre, were immunohistochemically stained with monoclonal antibodies to MMR proteins, MLH1, MSH2, MSH6 and PMS2 on the Ventana Benchmark XT autostainer. Of the 142 CRC cases entered into the study, there were 82 males and 60 females (M:F=1.4:1). Ethnically, 81 (57.0%) were Chinese, 32 (22.5%) Malays and 29 (20.4%) Indians. The patient ages ranged between 15-87 years (mean=62.4 years) with 21 cases <50-years and 121 ≥50-years of age. 14 (9.9%) CRC showed deficient MMR (dMMR). Concurrent loss of MLH1 and PMS2 occurred in 10, MSH2 and MSH6 in 2 with isolated loss of MSH6 in 1 and PMS2 in 1. dMMR was noted less frequently amongst the Chinese (6.2%) in comparison with their combined Malay and Indian counterparts (14.8%), and was associated with right sided and poorly differentiated tumours (p<0.05). 3 of the 5 (60.0%) dMMR CRC cases amongst the Chinese and 1 of 9 cases (11.1%) amongst the combined Malay and Indian group were <50-years of age. No significant association of dMMR was noted with patient age and gender, tumour stage or mucinous type.

Matched MeSH terms: MutS Homolog 2 Protein/genetics