STAT3 is Activated by CTGF-mediated Tumor-stroma Cross Talk to Promote HCC Progression
Yuki Makino, Hayato Hikita, Seiya Kato, Masaya Sugiyama, Minoru Shigekawa, Tatsuya Sakamoto, Yōichi Sasaki, Kazuhiro Murai, Sadatsugu Sakane, Takahiro Kodama, Ryotaro Sakamori, Shogo Kobayashi, Hidetoshi Eguchi, Nobuyuki Takemura, Norihiro Kokudo, Hideki Yokoi, Masashi Mukoyama, Tomohide Tatsumi, Tetsuo Takehara
Abstract
Background & Aims Signal transducer and activator of transcription 3 (STAT3) is known as a pro-oncogenic transcription factor. Regarding liver carcinogenesis, however, it remains controversial whether activated STAT3 is pro- or anti-tumorigenic. This study aimed to clarify the significance and mechanism of STAT3 activation in hepatocellular carcinoma (HCC). Methods Hepatocyte-specific Kras-mutant mice (Alb-Cre Kras LSL-G12D/+ ; Kras G12D mice) were used as a liver cancer model. Cell lines of hepatoma and stromal cells including stellate cells, macrophages, T cells, and endothelial cells were used for culture. Surgically resected 12 HCCs were used for human analysis. Results Tumors in Kras G12D mice showed up-regulation of phosphorylated STAT3 (p-STAT3), together with interleukin (IL)-6 family cytokines, STAT3 target genes, and connective tissue growth factor (CTGF). Hepatocyte-specific STAT3 knockout (Alb-Cre Kras LSL-G12D/+ STAT3 fl/fl ) downregulated p-STAT3 and CTGF and suppressed tumor progression. In coculture with stromal cells, proliferation, and expression of p-STAT3 and CTGF, were enhanced in hepatoma cells via gp130/STAT3 signaling. Meanwhile, hepatoma cells produced CTGF to stimulate integrin/nuclear factor kappa B signaling and up-regulate IL-6 family cytokines from stromal cells, which could in turn activate gp130/STAT3 signaling in hepatoma cells. In Kras G12D mice, hepatocyte-specific CTGF knockout (Alb-Cre Kras LSL-G12D/+ CTGF fl/fl ) downregulated p-STAT3, CTGF, and IL-6 family cytokines, and suppressed tumor progression. In human HCC, single cell RNA sequence showed CTGF and IL-6 family cytokine expression in tumor cells and stromal cells, respectively. CTGF expression was positively correlated with that of IL-6 family cytokines and STAT3 target genes in The Cancer Genome Atlas. Conclusions STAT3 is activated by CTGF-mediated tumor-stroma crosstalk to promote HCC progression. STAT3-CTGF positive feedback loop could be a therapeutic target.