RESUMO
BACKGROUND: The purpose of this study was to characterise the oncogenic roles of C35, a novel protein binding partner of ΔNp73, in ovarian cancer and to investigate the functional significance of C35-ΔNp73 interaction in the regulation of chemo-resistance. METHODS: C35 expression was evaluated by quantitative real-time PCR in human ovarian cancer tissues and cell lines. The aggressiveness of ovarian cancer cells overexpressing C35 was examined by cell proliferation, migration, soft agar and nude mouse xenograft. The significance of C35-ΔNp73 interaction in chemo-resistance was evaluated by apoptosis assays and cell viability after cisplatin treatment. RESULTS: The expression of C35 was significantly enhanced in human ovarian cancer tissues. Overexpression of C35 augmented proliferation, migration and tumourigenicity in ovarian cancer cell lines. C35 knockdown inhibited cell motility and cell growth. The co-expression of C35 and ΔNp73 by transient or stable transfection in ovarian cancer cells induced greater resistance to cisplatin treatment than did transfection with C35 or ΔNp73 alone. The cisplatin resistance was demonstrated to be caused by increased AKT and NFκB activity induced by C35-ΔNp73. CONCLUSION: Our results suggest that ΔNp73 might cooperate with C35 to promote tumour progression and contribute to cisplatin resistance in ovarian cancer cells. Future studies of the functional roles of ΔNp73 and C35 will provide insight that will aid in the establishment of new strategies and more effective therapies.
Assuntos
Antineoplásicos , Cisplatino , Proteínas de Ligação a DNA/metabolismo , Resistencia a Medicamentos Antineoplásicos/fisiologia , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Proteínas de Neoplasias/metabolismo , Proteínas Nucleares/metabolismo , Neoplasias Ovarianas/metabolismo , Proteínas Supressoras de Tumor/metabolismo , Animais , Linhagem Celular Tumoral , Proteínas de Ligação a DNA/fisiologia , Feminino , Humanos , Peptídeos e Proteínas de Sinalização Intracelular/fisiologia , Camundongos , Camundongos Nus , NF-kappa B/metabolismo , Proteínas de Neoplasias/fisiologia , Proteínas Nucleares/fisiologia , Neoplasias Ovarianas/fisiopatologia , Proteínas Proto-Oncogênicas c-akt/metabolismo , Reação em Cadeia da Polimerase em Tempo Real , Proteína Tumoral p73 , Proteínas Supressoras de Tumor/fisiologia , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
Recent evidence from a comprehensive genome analysis and functional studies have revealed that FOXM1 is a crucial metastatic regulator that drives cancer progression. However, the regulatory mechanism by which FOXM1 exerts its metastatic functions in cancer cells remains obscure. Here, we report that DLX1 acts as a FOXM1 downstream target, exerting pro-metastatic function in ovarian cancers. Both FOXM1 isoforms (FOXM1B or FOXM1C) could transcriptionally upregulate DLX1 through two conserved binding sites, located at +61 to +69bp downstream (TFBS1) and -675 to -667bp upstream (TFBS2) of the DLX1 promoter, respectively. This regulation was further accentuated by the significant correlation between the nuclear expression of FOXM1 and DLX1 in high-grade serous ovarian cancers. Functionally, the ectopic expression of DLX1 promoted ovarian cancer cell growth, cell migration/invasion and intraperitoneal dissemination of ovarian cancer in mice, whereas small interfering RNA-mediated DLX1 knockdown in FOXM1-overexpressing ovarian cancer cells abrogated these oncogenic capacities. In contrast, depletion of FOXM1 by shRNAi only partially attenuated tumor growth and exerted almost no effect on cell migration/invasion and the intraperitoneal dissemination of DLX1-overexpressing ovarian cancer cells. Furthermore, the mechanistic studies showed that DLX1 positively modulates transforming growth factor-ß (TGF-ß) signaling by upregulating PAI-1 and JUNB through direct interaction with SMAD4 in the nucleus upon TGF-ß1 induction. Taken together, these data strongly suggest that DLX1 has a pivotal role in FOXM1 signaling to promote cancer aggressiveness through intensifying TGF-ß/SMAD4 signaling in high-grade serous ovarian cancer cells.