BIGH3 promotes apoptosis in osteosarcoma tumor spheroids

Date
2015
Authors
Reza Poor, Fatemeh
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Abstract

Transforming Growth Factor Beta Induced Gene Human Clone 3, BIGH3, is an extra cellular matrix protein expressed by different cell types. BIGH3 promotes cell adhesion and has been recognized as a tumor suppressor protein in many studies, a function consistent with the finding that the expression of BIGH3 is reduced in various tumors and transformed cells when compared to healthy counterparts. In the present study, we found that BIGH3 induces MG63 multi tumor spheroid (MTS) cells apoptosis and antagonized the development of tumor cells into large aggregate, supporting BIGH3 tumor suppressor role. MG63 spheroids were cultured in recombinant BIGH3 and vascular smooth muscle cells (VSMCs) conditioned medium . We have shown BIGH3 to be abundantly expressed by VSMCs. In addition, stimulation of BIGH3 gene by TGF-β1 in MG63 cells resulted in overexpression of BIGH3 and subsequent increase in apoptosis by almost 3 fold. TUNEL assay was performed to detect apoptotic cells. Smaller and scattered tumor spheroids were observed in TGF-β1 treated cells. Importantly, in-house developed anti- BIGH3 antibody reduced apoptosis percentage by almost one-half and antagonized the development of osteosarcoma cells into large aggregate spheroids. Within the formed spheroids, BIGH3 was immunologically detected in in the stroma and at cell bodies, suggesting a possible binding of BIGH3 to the cell surface. Collectively, these data suggest that BIGH3 plays a suppressive role in development of osteosarcoma tumor spheroids. MG63 were cultured in agar-coated wells, where they developed into 3D aggregates. Unlike classical monolayer-based models (2D), multicellular tumor spheroid (MTS) cell culture system mimics the in vivo 3D structure of a solid tumor.

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Integrative Biology