Whole genome expression profiling in chewing-tobacco-associated oral cancers: a pilot study.

The current study was undertaken with a view to identify differential biomarkers in chewing-tobacco-associated oral cancer tissues in patients of Indian ethnicity. The gene expression profile was analyzed in oral cancer tissues as compared to clinically normal oral buccal mucosa. We examined 30 oral cancer tissues and 27 normal oral tissues with 16 paired samples from contralateral site of the patient and 14 unpaired samples from different oral cancer patients, for whole genome expression using high-throughput IlluminaSentrix Human Ref-8 v2 Expression BeadChip array. The cDNA microarray analysis identified 425 differentially expressed genes with >1.5-fold expression in the oral cancer tissues as compared to normal tissues in the oral cancer patients. Overexpression of 255 genes and downregulation of 170 genes (p < 0.01) were observed. Further, a minimum twofold overexpression was observed in 32 genes and downregulation in 12 genes, in 30-83% of oral cancer patients. Biological pathway analysis using Kyoto Encyclopedia of Genes and Genome Pathway database revealed that the differentially regulated genes were associated with critical biological functions. The biological functions and representative deregulated genes include cell proliferation (AIM2, FAP, TNFSF13B, TMPRSS11A); signal transduction (FOLR2, MME, HTR3B); invasion and metastasis (SPP1, TNFAIP6, EPHB6); differentiation (CLEC4A, ELF5); angiogenesis (CXCL1); apoptosis (GLIPR1, WISP1, DAPL1); and immune responses (CD300A, IFIT2, TREM2); and metabolism (NNMT; ALDH3A1). Besides, several of the genes have been differentially expressed in human cancers including oral cancer. Our data indicated differentially expressed genes in oral cancer tissues and may identify prognostic and therapeutic biomarkers in oral cancers, postvalidation in larger numbers and varied population samples.