Allelic variations in CYP2D6 gene and susceptibility to cervical cancer

Epidemiological studies have identified a number of risk factors that contribute to the development of cervical cancer precursors and cervical cancer. These include infection with certain oncogenic types of human papillomaviruses (HPVs) and other socio-economic factors. Tobacco smoking is an independent risk-factor for cervical neoplasia. It has been found that polymorphism at loci that encode carcinogen-metabolizing enzyme such as cytochrome P450 2D6 (CYP2D6) catalyzing the detoxification of carcinogens may determine susceptibility to cervical cancer. Therefore, it is likely that an understanding of these allelic differences is important for determining an individual's risk of cancer and susceptibility to potentially toxic agents. The aim of the present study was to elucidate the role of CYP2D6 polymorphism and susceptibility to squamous cell carcinoma of the uterine cervix in Indian population. Therefore, the genotype frequencies at this locus in females suffering with low-grade CIN, high-grade CIN and squamous cell carcinoma were compared. The control group consisted of 77 females with normal cervical cytology and the cases comprised of 61 mild/moderate dysplasia, 48 severe dysplasia and 45 cases of squamous cell carcinoma of uterine cervix. The individuals were divided into poor metabolizers (PM) and extensive metabolizers (EM) on the basis of their ability to metabolize certain drugs and carcinogens. Comparison of the frequency distribution for the combination of CYP2D6 EM genotype and smoking between mild/moderate and severe dysplasia was statistically significant (p=0.047) suggesting that women with cervical intraepithelial neoplasia I/II (CIN I/ CIN II) and CYP2D6 EM genotype who smoke appears to have more chances for the lesions to progress to CIN III. Whereas, frequency distribution for the same combination between severe dysplasia and squamous cell carcinoma failed to attain any statistical significance suggesting that CIN III with CYP2D6 EM genotype has less chance to progress to cervical cancer. Increased frequency of CYP2D6 EM and tobacco smoking show strong association with CIN III, indicating that not all lesions with the histopathological high grade CIN are premalignant. Conversely some squamous cell carcinomas may not be preceded by CIN.