Prognostic Relevance of Transforming Growth Factor-beta Receptor Expression and Signaling in Glioblastoma, Isocitrate Dehydrogenase-Wildtype

The transforming growth factor (TGF)-beta signaling pathway has been recognized as a major factor in promoting the aggressive behavior of glioblastoma, isocitrate dehydrogenase-wildtype. However, there is little knowledge about the expression of TGF-beta receptors in glioblastoma. Here, we studied the expression patterns of TGF-beta receptor II (TGF beta RII), type I receptors activin receptor-like kinase (ALK)-5, and ALK-1, as well as of the transcriptional regulators inhibitor of differentiation (Id) 2, Id3, and Id4 in human glioblastoma. The expression of TGF beta RII, ALK-5, and ALK-1 varied greatly, with TGF beta RII and ALK-5 being the most abundant and ALK-1 being the least expressed receptor. None of the 3 receptors was preferentially expressed by tumor vasculature as opposed to the tumor bulk, indicating tumor bulk-governed mechanisms of TGF-beta signaling with regard to glioblastoma-associated angiogenesis. A positive correlation was found between ALK-1 and Id2, suggesting that Id2, broadly expressed in the tumor cells, is a downstream target of this receptor-dependent pathway. Furthermore, there was a trend for high expression of ALK-5 or Id2 to be associated with inferior overall survival. Hence, we propose that ALK-5 may be used for patient stratification in future anti-TGF-beta treatment trials and that Id2 might be a potential target for anti-TGF-beta interventions.

Automated summary

The expression patterns of TGF-beta receptors in glioblastoma were investigated in this study. The results showed that TGF beta RII and ALK-5 were highly expressed, while ALK-1 was lowly expressed. Additionally, a positive correlation was found between ALK-1 and Id2, and high expression of ALK-5 or Id2 was associated with inferior overall survival.