br Introduction br Compared to the U S oral cancer
1. Introduction
Compared to the U.S. oral cancer development is high in India (Kekatpure and Kuriakose, 2010). In India, 20 per 100,000 people are affected by oral cancer which accounts for about 30% of all types of cancers. Invasive oral cancer is usually introduced by the presence of clinically known dysplasia of the oral mucosa or oral pre cancerous lesions. These oral pre cancers include, Lichen Planus, Leukoplakia, and Oral submucous fibrosis (OSMF). 
An oral pre cancerous lesion is de-fined as a benign, morphologically altered tissue that has a greater than normal risk of cancer transformation (Warnakulasuriya et al., 2007). Caffeine, tobacco, alcohol are known to be associated with a high number of cases of OSMF which are potentially malignant. Carcino-genic molecules from such substances are known to cause oxidative DNA damage to epithelial cells, and can be repaired by cell's own DNA
E-mail address: ssanyal@lko.amity.edu (S. Sanyal).
repair mechanisms (Frosina, 2000; Wood et al., 2001). However, faulty DNA repair systems, primarily occurring due to genetic polymorphisms may play a role in the development of oral pre cancer as well as oral cancer (Scully and Bagan, 2009).
DNA repair X-Gal are of four different categories depending on the repair pathways in which they are involved; Nucleotide Excision repair (NER), Base Excision repair (BER), Mismatch Repair (MMR) and double strand break repair. Xeroderma Pigmentosum group C (XPC) belongs to the NER pathway and polymorphisms in this gene are reported to be associated with oral pre cancerous lesion as well as oral cancer (Bootsma et al., 2002). The NER participates in the elimination of variety of stocky DNA-like ultra violet light-induced pyrimidine dimers, other photoproducts, larger chemical adducts and crosslinks. The Xer-oderma Pigmentosum group C is involved in the recognition and in-itiation of nucleotide excision repair pathway and binds to HR23B to
form a stable XPC-HR23B complex, which identifies and binds to da-maged DNA (Sugasawa et al., 1998). XPC polymorphisms may change the NER ability and affect genetic predisposition to cancer. It has been reported that polymorphisms in XPC may play an important role in lung cancer (Hollander et al., 2005),lymphomagenesis (Soufir et al., 2002) and urinary bladder neoplasm (Sanyal et al., 2004).
The present study was conducted to investigate any association of XPC A > C (Lys939Gln, rs2228001), C > T (Ala499Val, rs2228000) and intron 9 PAT (D > I) polymorphisms with the risk of oral pre cancer and cancer.
2. Material and methods
This study evaluated a total of 302 patients (with previously treated and pathologically confirmed oral pre cancer and cancer) who were registered at the department of Oral Pathology & Microbiology, King George's Medical University and 300 healthy controls after obtaining ethical clearance from the Institutional Ethics Committee of the King George's Medical University, Lucknow. Informed written consents were obtained from all subjects. Venous blood samples were collected in EDTA tubes and stored at −80 °C till DNA extraction. Genomic DNA extraction from blood samples was carried out by salting out method.
Genotyping for XPC PAT (D > I) polymorphisms were done by PCR method, while, genotypes for XPC A > C and, C > T polymorphisms were studied by polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) technique. PCR products (both undigested and di-gested) were resolved on a 2% agarose gel and stained with ethidium bromide for visualization under UV light. PCR products were generated in 10 μl reaction volumes containing 10 ng of genomic DNA, 2.0 mM MgCl2, 0.11 mM each dNTP, 0.3 mM each primer (Table 1) and 0.5 U Taq DNA polymerase (Sigma Aldrich, USA). PCR products were digested with re-striction enzymes listed in Table 1 and gel image of representative geno-types for each polymorphisms are shown in Fig 1, 2 and 3.