Suppression of Smad2/3-TSP1 Axis in HCC Tissues and Its Correlation with Tumor Angiogenesis

The Smad2/3-TSP1 axis is suppressed in TEC from HCC tissues and is negatively associated with tumor angiogenesis. We analyzed the expression of the Smad2/3-TSP1 axis in clinical samples, specifically using freshly isolated TEC from HCC tissues and NEC from adjacent non-tumor livers of patients. Compared to NEC, mRNA and protein levels of Smad2, Smad3, and TSP1 were decreased in TEC (Fig. 8A–C), which was further validated by the transcriptome profile of HCC TEC and NEC from GEO datasets (Fig. 8D). Additionally, the level of miR145 was significantly elevated in TEC from HCC tissues (Fig. 8E). Immunohistochemistry staining of embedded HCC and adjacent non-tumor liver tissues indicated that the expression of Smad3 and TSP1 were jointly downregulated in TEC of HCC tissues, and both were negatively correlated with MVA of HCC tissues (Fig. 8F–K). Furthermore, a significant positive correlation between Smad3 and TSP1 expression in tumor vessels was observed (Fig. 8L), further validating the anti-angiogenesis role of TGFβ signaling and the inactivation of TGFβ pathway in TEC. Collectively, our data suggest that TGFβ inhibits physiological angiogenesis via the TGFβR1-Smad2/3-TSP1 signaling under normoxia condition. However, in the hypoxic tumor microenvironment, miR145 is transactivated by HIF1α and then attenuates the anti-angiogenesis role of TGFβ by repressing Smad2 and Smad3 expression in EC.