Identification of differentially expressed genes in tobacco chewing-mediated oral cancer by differential display-polymerase chain reaction.

BACKGROUND: Identification of changes in gene expression that occur in oral squamous cell carcinoma (OSCC), after sufficient characterization, may yield novel molecular markers that may be useful in the diagnosis and disease management of oral cancer.
MATERIALS AND METHODS: We used differential display-polymerase chain reaction (DD-PCR) to study critically the global gene expression profile of the oral tumour versus normal epithelium. The differential expression of fished out cDNA were confirmed by Northern blot and reverse transcription-PCR. The differentially expressed cDNA were cloned, sequenced and matched for homology in the GenBank database.
RESULTS: We identified 13 cDNA that showed differential expression. Out of these we selected four cDNA showing consistent reproducibility. One of the cDNA expressed exclusively in tumour had a homology to DEK, a putative oncogene, and is linked to leukaemia, various cancers, HIV infection and several autoimmune disorders. Another cDNA expressed only in tumour had homology to sorcin protein. Sorcin is a 22-kDa calcium-binding protein and is associated with drug resistance in various cell lines. Apparently, sorcin expression might be responsible for drug resistance of OSCC and poor prognosis. Another cDNA showing 10 times overexpression in cheek tumour as compared to normal had homology to CDK6 gene. Hence, it seems from our results that CDK6 is dysregulated during oral carcinogenesis. The fourth cDNA was overexpressed in normal as compared to cheek tumour, but did not show any match in BLAST search.
CONCLUSIONS: We conclude that there is an enormous significance of these differentially expressed cDNA in oral cancer progression as they can serve as cancer markers to be used for diagnosis and therapeutic intervention.