Fused toes homolog, a potential molecular regulator of human papillomavirus type 16 E6 and E7 oncoproteins in cervical cancer

Abstract

Human papillomavirus type 16 (HPV16) plays a major role in the development of cervical cancer. The oncogenic potential of HPV16 is attributed to E6 and E7 oncoproteins. Here, we investigated the relationship between fused toes homolog (FTS) and HPV16 E6 and E7 in cervical cancer cells. HPV16-positive CaSki and SiHa cell lines were used for in vitro studies. FTS silencing was performed using a small interfering RNA (siRNA)-based approach, and western blotting was performed to determine the protein expression of tumor suppressors and cell survival markers. Immunoprecipitation, immunofluorescence, in silico analysis, and immunohistochemistry were performed to determine the interaction between, and intracellular co-localization of, FTS and both the E6 and E7 proteins. Silencing of FTS reduced the expression of the E6 and E7 proteins in cervical cancer cell lines and conversely increased the expression of the tumor suppressor proteins p53 and retinoblastoma protein. However, the primary transcripts of HPV16 E6 and E7 were unaffected by FTS silencing; furthermore, FTS transcription was unaffected by silencing of either E6 or E7, suggesting their interaction occurs post-translationally. Immunofluorescence and immunohistochemistry analysis demonstrated co-localization of FTS with the HPV16 E6 and E7 proteins, while immunoprecipitation results suggested that FTS interacts with both E6 and E7. Furthermore, in silico structural analysis identified putative residues involved in the binding of FTS with E6 and E7. Taken together, these results show that FTS affects both HPV16 E6 and E7 oncogenes in cervical cancer. We propose FTS as a target for the prevention of cervical cancer development and progression.