Association of polymorphisms in VDR, CYP27B1 and CYP24A1 genes with etiological factors and disease outcomes in patients with oral squamous cell carcinoma

Abstract

Oral Squamous Cell Carcinoma (OSCC) is characterized with a high mortality, low survival rate and rising incidences among members of younger age groups. Despite efforts in prevention, the survival rate remains unchanged for the last few decades, which indicates the need for oral cancer molecular characterization. The well-known risk factors are tobacco smoking and chewing, alcohol consumption, poor oral hygiene and infection with high risk human papilloma virus types. The fact that only a small percentage of people exposed to the risk factors really develops OSCC indicates the importance of genetic background in the process of oral cancerogenesis. Numerous studies have demonstrated the anticancerogen effects of vitamin D, which is reflected in cell cycle arrest, induction of cell differentiation, apoptosis induction, inhibition of malignant cell invasion and antiangiogenic effect. Vitamin D exerts it’s physiological function after binding to the Vitamin D Receptor (VDR), which is encoded by the VDR gene. A great number of Single Nucleotide Polymorphisms (SNPs) have been identified in the VDR gene, among which a small number have functional effects. Members of the huge protein cytochrome P450 family are involved in vitamin D metabolism: 1α-hydroxylase is involved in anabolism (encoded by the CYP27B1 gene) and 24-hydroxylase is involved in catabolism (encoded by the CYP24A1 gene). Since SNPs investigation is of great importance in the genetic association studies, it is interesting to consider whether genetic variants in genes, involved in vitamin D functioning and metabolism, could be associated with oral cancer risk, clinicopathological characteristics and patient survival. Aim. The aim of the doctoral dissertation was to determine the association between polymorphisms EcoRV, FokI, TaqI, ApaI, BsmI and rs11574085 in VDR gene, rs4646536 in CYP27B1 and rs2296241 polymorphisms in CYP24A1 gene with oral cancer risk, etiological factors and overall patients’ survival. Besides that, the aim was to determine the existence of haplotype blocks in the study group and to determine the association between detected haplotypes with risk of oral cancer development and survival. Material and methods. The study group consisted of 110 patients with diagnosed oral squamous cell carcinoma and 122 healthy individuals in the control group, matched in gender and age. DNA was isolated from the tumour tissue samples in the patients group and from peripheral blood samples, in the control group. VDR gene polymorphisms EcoRV, FokI, TaqI and ApaI were determined using the PCR- RFLP method and PCR Real Time method in the case of rs11574085 in VDR and polymorphisms in CYP27B1 and CYP24A1 genes. Obtained results were analysed by the statistical program SPSS. Linkage disequilibrium values as well as haplotype frequencies were calculated using the Haploview program, while association between detected haplotypes and survival were performed by the program Thesias. Associations were considered as significant when…