The expression of key cell cycle markers and presence of human papillomavirus in squamous cell carcinoma of the tonsil

Abstract: Background. Chemical carcinogens induce squa-mous cell carcinoma (SCC) of the head and neck by targeting the p53 and the retinoblastoma (pRb) pathways. Human papilloma-virus (HPV) might have an etiologic role in these cancers at par-ticular sites. Few studies have compared cell cycle protein ex-pression in HPV-positive and HPV-negative tumors in this region. Methods. Fifty tonsil SCCs were analyzed for HPV by PCR and for expression of cell cycle proteins (p53, pRb, p16INK4A, p21CIP1/WAF1, p27KIP1, and cyclinD1) by immunohistochemistry. Results. HPV was present in 42%; almost all were type 16. There were statistical associations between HPV positivity and reduced expression of pRb and cyclinD1, overexpression of p16, and younger patient age. Tumor with down-regulated p27 tended to have down-regulated pRb and p21. Conclusions. HPV-positive tonsil SCCs have distinct molecu-lar pathways. Their association with younger patient age sug-gests that they are biologically distinct from HPV-negative tu