Activin A controls angiogenesis and influences oral squamous cell carcinoma development

Objectives: Angiogenesis is essential for tumor development, as solid tumors must develop ways to induce angiogenesis in order to continue progression and expansion. Previous studies have shown that activin A, a member of the TGF-β superfamily, controls important events related to development and progression of oral squamous cell carcinomas (OSCC), but its effects on angiogenesis are unknown. Here we examine the role of activin A in oral tumor angiogenesis.
Methods: The effect of activin A on human umbilical vein endothelial cells (HUVECs) tubulogenesis was investigated using matrigel assays, cellular proliferation was assessed by BrdU incorporation index, cellular apoptosis was analysed by flow cytometry and cellular migration was investigated using transwell assays. The influence of endogenous activin A was evaluated in HUVEC cells stably expressing shRNA targeting activin A (shINHBA). The effect of activin A released from OSCC cells on HUVECs was assessed using conditioned medium collected from OSCC shINHBA cells. We also investigated the effects of activin A on oral tumor growth in vivo using a mouse xenograft model.
Results: We demonstrate increased tubulogenesis activity concomitantly with high proliferation in activin A-treated HUVECs; however, it did not alter the rates of apoptosis or cell migration. Conversely, follistatin, an activin A antagonist, and activin A knock down in HUVECs significantly inhibited proliferation, induced apoptosis, cell migration and decreases tube formation. Similarly, conditioned media harvested from control shScramble OSCC cells increased the proliferative rate and the tubulogenic activity, whereas the ability of proliferation and tube formation of HUVECs was significantly decreased in tumor conditioned media of shINHBA OSCC cells. In vivo, tumors incorporating shINHBA HUVECs were significantly smaller than tumors incorporating shScamble HUVECs.
Conclusions: These results presented here highlight a role for activin A in oral tumor angiogenesis, suggesting that activin A signaling could be an important target for tumor vascular disruption in oral carcinomas. Financial support: FAPESP.