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A novel pathogenic variant of the LDLR gene in the Asian population and its clinical correlation with familial hypercholesterolemia

Chahil JK, Lye SH, Bagali PG, Alex L

Mol Biol Rep, 2012 Jul;39(7):7831-8.
PMID: 22544571 DOI: 10.1007/s11033-012-1626-8

Familial hypercholesterolemia (FH) is a disease implicated with defects in either, Low density lipoprotein receptor gene (LDLR), Apolipoprotein B-100 gene (APOB), the Proprotein convertase subtilisin/kexin type 9 gene (PCSK9) or other related genes of the lipid metabolism pathway. The general characterization of heterozygous FH is by elevated low-density lipoprotein (LDL) cholesterol and early-onset cardiovascular diseases, while the more severe type, the homozygous FH results in extreme elevated levels of LDL cholesterol and usually death of an affected individual by early twenties. We present here a novel non-synonymous, missense mutation in exon 14 of the LDLR gene in two siblings of the Malay ethnicity discovered during an in-house genetic test. We postulate that their elevated cholesterol is due to this novel mutation and they are positive for homozygous FH. This is the first report of a C711Y mutation in patients with elevated cholesterol in Asia.
Differences in allele frequencies of autosomal dominant hypercholesterolemia SNPs in the Malaysian population

Alex L, Chahil JK, Lye SH, Bagali P, Ler LW

J Hum Genet, 2012 Jun;57(6):358-62.
PMID: 22534770 DOI: 10.1038/jhg.2012.34

Hypercholesterolemia is caused by different interactions of lifestyle and genetic determinants. At the genetic level, it can be attributed to the interactions of multiple polymorphisms, or as in the example of familial hypercholesterolemia (FH), it can be the result of a single mutation. A large number of genetic markers, mostly single nucleotide polymorphisms (SNP) or mutations in three genes, implicated in autosomal dominant hypercholesterolemia (ADH), viz APOB (apolipoprotein B), LDLR (low density lipoprotein receptor) and PCSK9 (proprotein convertase subtilisin/kexin type-9), have been identified and characterized. However, such studies have been insufficiently undertaken specifically in Malaysia and Southeast Asia in general. The main objective of this study was to identify ADH variants, specifically ADH-causing mutations and hypercholesterolemia-associated polymorphisms in multiethnic Malaysian population. We aimed to evaluate published SNPs in ADH causing genes, in this population and to report any unusual trends. We examined a large number of selected SNPs from previous studies of APOB, LDLR, PCSK9 and other genes, in clinically diagnosed ADH patients (n=141) and healthy control subjects (n=111). Selection of SNPs was initiated by searching within genes reported to be associated with ADH from known databases. The important finding was 137 mono-allelic markers (44.1%) and 173 polymorphic markers (55.8%) in both subject groups. By comparing to publicly available data, out of the 137 mono-allelic markers, 23 markers showed significant differences in allele frequency among Malaysians, European Whites, Han Chinese, Yoruba and Gujarati Indians. Our data can serve as reference for others in related fields of study during the planning of their experiments.
Association of genetic and non-genetic risk factors with the development of prostate cancer in Malaysian men

Munretnam K, Alex L, Ramzi NH, Chahil JK, Kavitha IS, Hashim NA, et al.

Mol Biol Rep, 2014;41(4):2501-8.
PMID: 24443231 DOI: 10.1007/s11033-014-3107-8

There is growing global interest to stratify men into different levels of risk to developing prostate cancer, thus it is important to identify common genetic variants that confer the risk. Although many studies have identified more than a dozen common genetic variants which are highly associated with prostate cancer, none have been done in Malaysian population. To determine the association of such variants in Malaysian men with prostate cancer, we evaluated a panel of 768 SNPs found previously associated with various cancers which also included the prostate specific SNPs in a population based case control study (51 case subjects with prostate cancer and 51 control subjects) in Malaysian men of Malay, Chinese and Indian ethnicity. We identified 21 SNPs significantly associated with prostate cancer. Among these, 12 SNPs were strongly associated with increased risk of prostate cancer while remaining nine SNPs were associated with reduced risk. However, data analysis based on ethnic stratification led to only five SNPs in Malays and 3 SNPs in Chinese which remained significant. This could be due to small sample size in each ethnic group. Significant non-genetic risk factors were also identified for their association with prostate cancer. Our study is the first to investigate the involvement of multiple variants towards susceptibility for PC in Malaysian men using genotyping approach. Identified SNPs and non-genetic risk factors have a significant association with prostate cancer.
Identification of genetic and non-genetic risk factors for nasopharyngeal carcinoma in a Southeast Asian population

Nor Hashim NA, Ramzi NH, Velapasamy S, Alex L, Chahil JK, Lye SH, et al.

Asian Pac J Cancer Prev, 2012;13(12):6005-10.
PMID: 23464394

BACKGROUND: Nasopharyngeal carcinoma (NPC) is endemic in Southern Chinese and Southeast Asian populations. Geographical and ethnic clustering of the cancer is due to genetic, environmental, and lifestyle risk factors. This case-control study aimed to identify or confirm both genetic and non-genetic risk factors for NPC in one of the endemic countries, Malaysia.
MATERIALS AND METHOD: A panel of 768 single-nucleotide polymorphisms (SNPs) previously associated with various cancers and known non-genetic risk factors for NPC were selected and analyzed for their associations with NPC in a case-control study.
RESULTS: Statistical analysis identified 40 SNPs associated with NPC risk in our population, including 5 documented previously by genome-wide association studies (GWAS) and other case-control studies; the associations of the remaining 35 SNPs with NPC were novel. In addition, consistent with previous studies, exposure to occupational hazards, overconsumption of salt-cured foods, red meat, as well as low intake of fruits and vegetables were also associated with NPC risk.
CONCLUSIONS: In short, this study confirmed and/or identified genetic, environmental and dietary risk factors associated with NPC susceptibility in a Southeast Asian population.
Fulltext Genetic polymorphisms associated with breast cancer in malaysian cohort

Chahil JK, Munretnam K, Samsudin N, Lye SH, Hashim NA, Ramzi NH, et al.

Indian J Clin Biochem, 2015 Apr;30(2):134-9.
PMID: 25883419 DOI: 10.1007/s12291-013-0414-0

Genome-wide association studies have discovered multiple single nucleotide polymorphisms (SNPs) associated with the risk of common diseases. The objective of this study was to demonstrate the replication of previously published SNPs that showed statistical significance for breast cancer in the Malaysian population. In this case-control study, 80 subjects for each group were recruited from various hospitals in Malaysia. A total of 768 SNPs were genotyped and analyzed to distinguish risk and protective alleles. A total of three SNPs were found to be associated with increased risk of breast cancer while six SNPs showed protective effect. All nine were statistically significant SNPs (p ≤ 0.01), five SNPs from previous studies were successfully replicated in our study. Significant modifiable (diet) and non-modifiable (family history of breast cancer in first degree relative) risk factors were also observed. We identified nine SNPs from this study to be either conferring susceptibility or protection to breast cancer which may serve as potential markers in risk prediction.
Fulltext Genetic polymorphisms in LDLR, APOB, PCSK9 and other lipid related genes associated with familial hypercholesterolemia in Malaysia

Lye SH, Chahil JK, Bagali P, Alex L, Vadivelu J, Ahmad WA, et al.

PLoS One, 2013;8(4):e60729.
PMID: 23593297 DOI: 10.1371/journal.pone.0060729

Familial hypercholesterolemia (FH) is an autosomal dominant disorder characterized by elevations in total cholesterol (TC) and low density lipoprotein cholesterol (LDLc). Development of FH can result in the increase of risk for premature cardiovascular diseases (CVD). FH is primarily caused by genetic variations in Low Density Lipoprotein Receptor (LDLR), Apolipoprotein B (APOB) or Proprotein Convertase Subtilisin/Kexin type 9 (PCSK9) genes. Although FH has been extensively studied in the Caucasian population, there are limited reports of FH mutations in the Asian population. We investigated the association of previously reported genetic variants that are involved in lipid regulation in our study cohort. A total of 1536 polymorphisms previously implicated in FH were evaluated in 141 consecutive patients with clinical FH (defined by the Dutch Lipid Clinic Network criteria) and 111 unrelated control subjects without FH using high throughput microarray genotyping platform. Fourteen Single Nucleotide Polymorphisms (SNPs) were found to be significantly associated with FH, eleven with increased FH risk and three with decreased FH risk. Of the eleven SNPs associated with an increased risk of FH, only one SNP was found in the LDLR gene, seven in the APOB gene and three in the PCSK9 gene. SNP rs12720762 in APOB gene is associated with the highest risk of FH (odds ratio 14.78, p<0.001). Amongst the FH cases, 108 out of 141 (76.60%) have had at least one significant risk-associated SNP. Our study adds new information and knowledge on the genetic polymorphisms amongst Asians with FH, which may serve as potential markers in risk prediction and disease management.
Influences of multiple genetic polymorphisms on ovarian cancer risk in Malaysia

Velapasamy S, Alex L, Chahil JK, Lye SH, Munretnam K, Hashim NA, et al.

Genet Test Mol Biomarkers, 2013 Jan;17(1):62-8.
PMID: 23113749 DOI: 10.1089/gtmb.2012.0223

The identification of high-risk individuals can help to improve early cancer detection and patient survival. Risk assessment, however, can only be accomplished if the risk factors are known. To date, the genetic risk factors for ovarian cancer, other than mutations in the BRCA1/2 genes, have never been systematically explored in Malaysia. The present study aims to identify from a panel of cancer-associated single-nucleotide polymorphisms (SNPs), those associated with ovarian cancer risk in Malaysia.
Fulltext Role of genetic & environment risk factors in the aetiology of colorectal cancer in Malaysia

Ramzi NH, Chahil JK, Lye SH, Munretnam K, Sahadevappa KI, Velapasamy S, et al.

Indian J Med Res, 2014 Jun;139(6):873-82.
PMID: 25109722

Colorectal cancer (CRC) is second only to breast cancer as the leading cause of cancer-related deaths in Malaysia. In the Asia-Pacific area, it is the highest emerging gastrointestinal cancer. The aim of this study was to identify single nucleotide polymorphisms (SNPs) and environmental factors associated with CRC risk in Malaysia from a panel of cancer associated SNPs.