Role of PAX8 in the tumorigenesis of ovarian cancer

Abstract

PAX8 is a member of the Paired box (PAX) multigene family of transcription factors, which are involved in the tissue-specific control of the expression of several genes during development of both vertebrates and invertebrates. Previously, PAX8 has been studied as key molecular marker and regulator of follicular thyrocyte differentiation, but recent evidence show that PAX8 is also expressed in specific types of tumors. In particular, PAX8 results to be expressed in human ovarian cancer subtypes and Fallopian tubal secretory cells from which the ovarian cancer may originate. However, the functional role of PAX8 in the carcinogenesis of ovarian cancer has not been addressed yet. In this study, we investigated the potential role of PAX8 in ovarian cancer progression, using in vitro ovarian cancer cells and in vivo mouse xenograft models. To this purpose, stable PAX8 depleted ovarian cancer cells (SKOV-3) were generated using short hairpin RNA (shRNA) constructs. Cell proliferation, motility and invasion potential of PAX8 silenced cells were analyzed by means of growth curves, wound healing and matrigel assays. Furthermore, PAX8 knockdown and control cells were injected into nude mice for xenograft tumorigenicity assay. The results obtained in vitro showed that PAX8 is involved in the regulation of proliferation, migration and invasion of ovarian cancer cells. In addition, PAX8 silencing strongly suppresses cellular anchorage-independent growth in vitro and, notably, tumorigenesis in vivo in the nude xenograft mouse model. Overall, these results indicate that PAX8 plays an important role in the tumorigenic phenotype of ovarian cancer cells.Finally, to identify new genes and pathways modulated by PAX8 in ovarian cancer, an expression profile analysis was performed by RNA sequencing (RNA-seq) of PAX8 knockdown ovarian cancer cell (SKOV-3) and Fallopian tube cells (FT-194). Twenty-four hours after PAX8 knockdown in SKOV-3 and FT-194, 182 and 164 genes were found to be modulated, respectively. These genes resulted to be correlated to different biological pathways involved in cancer progression. This is the first RNA-seq study that compares genes regulated by PAX8 in ovarian cancer cells and Fallopian tube cells. The identification of the biological pathways and target genes controlled by PAX8 will have considerable importance to understand ovarian cancer progression as well as to set up novel therapeutic strategies