Induction of apoptosis determined using Nicoletti assay in HPV-positive and HPV-negative cells after radiation, hyperthermia and combined treatment in the presence or absence of P53-siRNA,cDDP, chloroquine or MG-132.
ARTICLE ABSTRACT
Human papillomavirus (HPV) is associated with cervical cancer, the third most common cancer in women. The high-risk HPV types 16 and 18 are found in over 70% of cervical cancers and produce the oncoprotein, early protein 6 (E6), which binds to p53 and mediates its ubiquitination and degradation. Targeting E6 has been shown to be a promising treatment option to eliminate HPV-positive tumor cells. In addition, combined hyperthermia with radiation is a very effective treatment strategy for cervical cancer. In this study, we examined the effect of hyperthermia on HPV-positive cells using cervical cancer cell lines infected with HPV 16 and 18, in vivo tumor models, and ex vivo–treated patient biopsies. Strikingly, we demonstrate that a clinically relevant hyperthermia temperature of 42°C for 1 hour resulted in E6 degradation, thereby preventing the formation of the E6–p53 complex and enabling p53-dependent apoptosis and G2-phase arrest. Moreover, hyperthermia combined with p53 depletion restored both the cell-cycle distribution and apoptosis to control levels. Collectively, our findings provide new insights into the treatment of HPV-positive cervical cancer and suggest that hyperthermia therapy could improve patient outcomes. Cancer Res; 75(23); 5120–9. ©2015 AACR.
