The HPV-positive tumors are not more curable based on increased epithelial sensitivity to cisplatin or radiation therapy. Instead, radiation and cisplatin induce an immune response to this antigenic cancer. The implications of these results may lead to novel therapies that enhance tumor eradication for HPV-positive cancers.

Human papillomaviruses (HPV's) are a causative factor in over 90% of cervical and 25% of head and neck squamous cell carcinomas (HNSCC's). The C-terminus of the high risk HPV 16 E6 oncoprotein physically associates with and degrades a non-receptor protein tyrosine phosphatase (PTPN13), and PTPN13 loss synergizes with H-RasV12 or ErbB2 for invasive growth in vivo. Oral keratinocytes that have lost PTPN13 and express H-RasV12 or ErbB2 show enhanced Ras/RAF/MEK/Erk signaling. In co-transfection studies, wild type PTPN13 inhibited Ras/RAF/MEK/Erk signaling in HEK 293 cells that over-express ErbB2, EGFR, or H-RasV12, while an enzymatically inactive PTPN13 did not. Twenty percent of HPV negative HNSCC's had PTPN13 phosphatase mutations that did not inhibit Ras/RAF/MEK/Erk signaling. Inhibition of Ras/RAF/MEK/Erk signaling using the MEK inhibitor U0126 blocked anchorage independent growth in cells lacking PTPN13. These findings show PTPN13 phosphatase activity plays a physiologically significant role in regulating MAP kinase signaling.

No abstract