Human papillomavirus (HPV) infections play a crucial role in human carcinogenesis. Greater than 96% of all cervical carcinomas are positive for high-risk HPV infections; especially types 16 and 18. High-risk HPV onco-proteins, E6 and E7, are consistently expressed in such cancers and function by inactivating p53 and pRb tumor suppressors, respectively. The presence of high-risk HPVs is also correlated with anogenital cancers. In this study, we examined the effect of high-risk HPV type 16 E6 and E7 oncoproteins in two normal human colorectal epithelial cell lines, NCE1 and NCE5. We report that the expression of E6/E7 proteins, alone, induced cellular transformation of both cell lines; consequently, NCE1-E6/E7 and NCE5-E6/E7 form colonies in soft agar with respect to their wild type cells. This is accompanied by cell cycle deregulation, as is demonstrated by the over-expression of cyclin dependant kinases (cdks) and their respective cyclins. Furthermore, we demonstrate that E6/E7 oncoprotein transduction induces migration of colorectal epithelial cells. More still, well analyzed Id gene expression, a family member of the helix-loop-helix (HLH) transcription factors involved in the regulation of cell invasion and metastasis of human cancer cells. In parallel, using tissue microarray analysis we found that the four members of the Id protein family are correlated with the presence of HPV type 16 and 18 in human colon cancer tissues. Our data suggests that high-risk HPV infections are sufficient to induce cellular transformation of normal human colorectal cells, in vitro. Furthermore, the correlation with the Id family of proteins may present a novel set of markers associated with HPV induced colorectal carcinogenesis. Our results may suggest a new approach to detect and prevent colorectal cancer.

No description available.