Aim: To elucidate the biological effects of transforming growth factor-beta1 (TGF-beta1) on intrahepatic cholan-giocarcinoma (ICC).
Methods: We investigated the effects of TGF-beta1 on human ICC cell lines (HuCCT1, MEC, and HuH-28) by monitoring the influence of TGF-beta1 on tumor growth and interleukin-6 (IL-6) expression in ICC cells.
Results: All three human ICC cell lines produced TGF-beta1 and demonstrated accelerated growth in the presence of TGF-beta1 with no apoptotic effect. Studies on HuCCT1 revealed a TGF-beta1-induced stimulation of the expression of TGF-beta1, as well as a decrease in TGF-beta1 mRNA expression induced by neutralizing anti-TGF-beta1 antibody. These results indicate that TGF-beta1 stimulates the production and function of TGF-beta1 in an autocrine fashion. Further, IL-6 secretion was observed in all three cell lines and exhibited an inhibitory response to neutralizing anti-TGF-beta1 antibody. Experiments using HuCCT1 revealed a TGF-beta1-induced acceleration of IL-6 protein expression and mRNA levels. These findings demonstrate a functional interaction between TGF-beta1 and IL-6. All three cell lines proliferated in the presence of IL-6. In contrast, TGF-beta1 induced no growth effect in HuCCT1 in the presence of small interfering RNA against a specific cell surface receptor of IL-6 and signal transducer and activator of transcription-3.
Conclusion: ICC cells produce TGF-beta1 and confer a TGF-beta1-induced growth effect in an autocrine fashion. TGF-beta1 activates IL-6 production, and the functional interaction between TGF-beta1 and IL-6 contributes to ICC cell growth by TGF-beta1.