Safiya Abdullah

Analysis of molecular aberrations of Wnt pathway gladiators in colorectal cancer in the Kashmiri population

The development and progression of colorectal cancer (CRC) is a multi-step process, and the Wnt pathways with its two molecular gladiators adenomatous polyposis coli (APC) and β-catenin plays an important role in transforming a normal tissue into a malignant one. In this study, we aimed to investigate the role of aberrations in the APC and β-catenin genes in the pathogenesis of CRC in the Kashmir valley, and to correlate it with various clinicopathological variables. We examined the paired tumour and normal-tissue specimens of 86 CRC patients for the occurrence of aberrations in the mutation cluster region (MCR) of the APC gene and exon 3 of the β-catenin gene by polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP) and/or PCR-direct sequencing. Analysis of promoter hypermethylation of the APC gene was also carried out using methylation-specific PCR (MS-PCR). The overall mutation rate of the MCR of the APC gene among 86 CRC cases was 12.8 per cent (11 of 86). Promoter hypermethylation of APC was observed in 54.65 per cent (47 of 86) of cases. Furthermore, we found a significant association between tumour location, tumour grade and node status and the methylation status of the APC gene (p ≤ 0.05). Although the number of mutations in the APC and β-catenin genes in our CRC cases was very low, the study confirms the role of epigenetic gene silencing of the pivotal molecular gladiator, APC, of the Wnt pathway in the development of CRC in the Kashmiri population.

DNA Repair Gene 8-Oxoguanine DNA Glycosylase Ser326Cys Polymorphism and Colorectal Cancer Risk in a Kashmiri Population

8-Oxoguanine DNA glycosylase (OGG1) is one of the important base excision repair enzymes that repair 8-oxoguanine lesion incorporated within the DNA of an individual by reactive oxygen species. The aim of this study was to detect the role of OGG1 Ser326Cys polymorphism in susceptibility to colorectal cancer (CRC) in a Kashmiri population. We investigated the genotype distribution of the OGG1 gene in 114 CRC cases in comparison with 200 healthy subjects. There was no significant association between OGG1 Ser326Cys polymorphism and CRC, but the homozygous Cys/Cys variant genotype was associated with an increased risk of colon cancer (p<0.05). This study suggests that the OGG1 polymorphism is not associated with the risk of development of CRC in the Kashmiri population in general but modulates the risk of cancer development in colon via interaction with many dietary factors.

Mutational spectrum of conserved regions of TP53 and PTEN genes in Kangri cancer (of the skin) in the Kashmiri population

Kangri cancer is a unique, thermally induced squamous cell carcinoma (SCC) of the skin that develops due to persistent use of a Kangri (a brazier) by the Kashmiri people to combat the cold temperature during winter. Unlike classical UV-induced SCC of the skin, Kangri cancer appears on the legs and abdomen. Its common features are erythematous patches, recurrence and metastasis. In the absence of any molecular etiology, we made a preliminary attempt to estimate the nature and frequency of mutations in the TP53 and PTEN genes in Kangri cancer patients from Kashmir. PCR-SSCP analysis followed by direct sequencing revealed that TP53 mutations account for 40% (12/30) of sporadic Kangri cancer patients and that PTEN mutations account for only 6.6% (2/30). There were 16 mutations in TP53 exons 5 and 7, found in 12 patients. They consisted of 11 substitutions (7 transitions, 3 transversions and 1 double-base) and 5 insertions. The 11 substitutions represent 8 distinct missense mutations, 3 of which were silent mutations. The mutations detected in the PTEN gene consisted of one insertion and one C>T transition. This high percentage of TP53 mutations (especially A>G) showed a statistically significant association with age and positive lymph node status. Our results indicate that TP53 is a predominant target of chronic hyperthermia in the development of Kangri cancer in the moderate risk Kashmiri population. The differences in the TP53 mutation spectrum of UV-induced SCC of the skin and Kangri cancer are probably due to the nature of the respective environmental carcinogens. The study also suggests that TP53 may function as a potential molecular marker and prognostic tool, at least in a subset of sporadic Kangri tumors.

P53- The Molecular Guardian Crashes in Gastric Adenocarcinomas - A Study in an Ethnic Kashmiri Population

Genetic instability underlies the etiology of multistep gastric carcinogenesis. The p53 mutations observed in tumors represent the expression of such instability by allowing the accumulation of genetic alterations caused by multiple mechanisms. The present study was conducted to investigate the nature and frequency of TP53 mutations in patients with gastric adenocarcinomas of Kashmir valley. Tumor samples from 30 patients with primary gastric adenocarcinomas undergoing radical gastrectomy were evaluated. The mutational status of the p53 (exons 5 to 8) was screened by PCR-SSCP analysis followed by direct sequencing. Of all 30 gastric adenocarcinomas including ten intestinal types and twenty diffuse types, 20% patients (6/30) harbored mutations in the p53 gene. Overall, twenty-one mutations were found in TP53 in 30 patients included in this study. Mutations were found at codon 142 (3 cases) of exon 5, codon 144 (1 case) in exon 5, codon 147 (1 case) in exon 5, codon 157 (1 case) in exon 5, codon 169 (2 cases) in exon 5, codon 170 (3 cases) in exon 5, codon 172 (1 case) in exon 5, codon 173 (3 cases) in exon 5, codon 179 (3 cases) in exon 5, codon 180 (1 case) in exon 5, codon 213 (1 case) in exon 6, the insertional mutation was between codon 216 & 217 (1 case) in exon 6 and codon 287 in exon 8 (1 case). The mutation pattern comprised of 12 insertions, 6 substitutions (all transversions) and 3 deletions. All the twelve insertions represented frame-shift mutations. The six single-base substitutions leading to aminoacid substitution included four missense mutations and a single silent mutation. The mutation effect data was found to be significant (p< 0.05). This study exhibited signifi cant amount of mutation in exon 5 (OR=90.25 and p<0.05 within the CI of 12.47-652.89) of TP53 in the gastric adenocarcinoma patients from Kashmir valley. Comparison of mutation profi le with other ethnic populations and regions refl ected both differences and similarities indicating co-exposure to a unique set of risk factors. The differences could be due to exposure to explicit environmental carcinogens, different lifestyle, dietary or cultural practices of Kashmiris being an ethnic population that need further investigations. The direct sequencing results, therefore, shall help in understanding the molecular events associated with progression and metastasis in gastric carcinoma. Conclusions: p53 gene mutation incites the pathogenesis of human gastric adenocarcinomas.

The blues of P(16)INK(4a): aberrant promoter methylation and association with colorectal cancer in the Kashmir valley.

Hypermethylation of the promoter region of the p16INK4a (p16) gene plays a significant role in the development and progression of colorectal cancer (CRC). The aim of the present study was to establish the role of the methylation status of the p16 gene in 114 CRC cases and to correlate it with the various clinicopathological parameters. Analysis of p16 promoter methylation was performed by methylation-specific PCR. Forty-eight (42.1%) of the CRC cases were found to be methylated for the p16 gene in our population. The methylation status was found to be associated with the gender, lymph node status, tumour stage, smoking status and tumour grade of the CRC patients. p16 plays a pivotal role in tumour development and progression to advanced stages.

ACE gene polymorphism in breast cancer patients of ethnic Kashmiri population

Background: The mitogenic and angiogenic effect of angiotensin II has been shown in breast cancer. Angiotensin II is converted from its inactive form to active form by the angiotensin I converting enzyme (ACE). Materials and Methods: To evaluate the effect of ACE gene in breast cancer patients and its effect on healthy control subjects, we studied 130 breast cancer patients and 220 healthy controls. Results: During our study, we found, the ACE genotype distribution in breast cancer patients were as follows: 62 (47.6%) had Deletion (DD), 43 (33.07%) had ID, and 25 (19.23%) had II (Insertion) genotypes, whereas in controls, 96 (43.63%) had DD, 107 (48.63%) had ID, and 25 (7.7%) had II genotypes. Conclusion: We conclude that our results implicate that ACE level/activity has been suggested to be protective against breast cancer, and therefore renin-angiotensin system may serve as a curative target for breast cancer detection, treatment, and prevention. Impact: Our study is the first report from India on Kashmiri population, suggesting that ACE activity can be a protective tool against breast cancer.