TGFβ signaling regulates epithelial–mesenchymal plasticity in ovarian cancer ascites-derived spheroids

Abstract

Epithelial-mesenchymal transition (EMT) serves as a key mechanism driving tumor cell migration, invasion, and metastasis in many carcinomas. Transforming growth factor-beta (TGFb) signaling is implicated in several steps during cancer pathogenesis and acts as a classical inducer of EMT. Since epithelial ovarian cancer (EOC) cells have the potential to switch between epithelial and mesenchymal states during metastasis, we predicted that modulation of TGFb signaling would significantly impact EMT and the malignant potential of EOC spheroid cells. Ovarian cancer patient ascites-derived cells naturally underwent an EMT response when aggregating into spheroids, and this was reversed upon spheroid re-attachment to a substratum. CDH1/E-cadherin expression was markedly reduced in spheroids compared with adherent cells, in concert with an up-regulation of several transcriptional repressors, i.e., SNAI1/Snail, TWIST1/2, and ZEB2. Treatment of EOC spheroids with the TGFb type I receptor inhibitor, SB-431542, potently blocked the endogenous activation of EMT in spheroids. Furthermore, treatment of spheroids with SB-431542 upon re-attachment enhanced the epithelial phenotype of dispersing cells and significantly decreased cell motility and Transwell migration. Spheroid formation was significantly compromised by exposure to SB-431542 that correlated with a reduction in cell viability particularly in combination with carboplatin treatment. Thus, our findings are the first to demonstrate that intact TGFb signaling is required to control EMT in EOC ascites-derived cell spheroids, and it promotes the malignant characteristics of these structures. As such, we show the therapeutic potential for targeted inhibition of this pathway in ovarian cancer patients with late-stage disease.

Malignant Pleural Effusion and ascites Induce Epithelial-Mesenchymal Transition and Cancer Stem-like Cell Properties via the Vascular Endothelial Growth Factor (VEGF)/Phosphatidylinositol 3-Kinase (PI3K)/Akt/Mechanistic Target of Rapamycin (mTOR) Pathway

“…Indeed, VEGF was reported to induce EMT in human pancreatic cancer cells (35). Previous investigations reported that cancer cell EMT and gain of CSC properties in malignant PE/ascites depended on TrkB and TGF-␤ signaling, respectively (9,45). TrkB is a well established regulator that promotes VEGF expression (46).…”

Tumor-associated macrophages drive spheroid formation during early transcoelomic metastasis of ovarian cancer

“…Many studies have suggested that the process of transcoelomic metastasis could be divided into several steps: (a) cell detachment, survival, and resistance of anoikis; (b) evasion of immunological surveillance; (c) epithelial-mesenchymal transition; (d) spheroid formation; (e) ascites formation; and (f) peritoneal implantation (8)(9)(10). However, it remains unclear how free detached tumor cells survive in the transcoelomic environment and form spheroids in the initial steps of transcoelomic metastasis.…”

ASK1-dependent endothelial cell activation is critical in ovarian cancer growth and metastasis

“…The primary metastasis mode of OC is transcoelomic, which involves a tumor cell that is detached from the primary tumor and is transported and implanted in peritoneum and pelvic organs. In this process, detached tumor cells aggregate as spheroids within the abdominal cavity to overcome anoikis, immune attack, and chemotherapy (24)(25)(26). These spheroids can spread over the peritoneal cavity, invade the peritoneum, and implant in pelvic organs and omentum.…”