[Introduction] Tenascin-C (TN-C), an extracellular matrix molecules, is highly expressed in cancer stroma. Recent studies have demonstrated that cancer associated fibroblasts (CAFs) expressed TN-C in many tumors, including breast cancer. Here, we clarified the effects of TN-C on phenotype changes of the fibroblasts. [Methods] We examined the cell morphology, expression of CAFs markers, and contractile ability in the fibroblasts after TNC treatment in vitro, using human mammary gland fibroblasts (HMFs) and dermal ones (HDFs). We also investigated the correlation between the expression of the CAF markers and TNC deposition in human breast cancer tissues, using immunohistochemical staining. [Results] TN-C (10μg/mL) induced morphological changes of HMFs from spindle-shaped cells to stellate-shaped cells on plastic as well as on glass coverslips. After the treatment of TN-C, the protein expressions of α-SMA and calponin were significantly increased. Immunofluorescence analysis revealed TN-C increased the actin-stress fiber formation and the expression of α-SMA and calponin. Furthermore, TN-C promoted contraction of collagen gel by HMFs. These results indicated TN-C induces transformation of HMFs into high-contractile myofibroblasts. In human breast cancer tissues, α-SMA and calponin-positive fibroblasts were localized in TN-C-positive cancer stroma. Interestingly, calponin-expressing fibroblasts were not observed in the skin metastatic lesions of breast cancer. In addition, the increased expression of α-SMA and calponin after TN-C treatment in HDFs were significantly lower compared to HMFs in vitro. These results suggested the responses of TN-C on fibroblasts differs according to the residential tissues. Next, we examined the receptor to TNC and signaling pathway for TNC-induced change of HMFs. TN-C increased the colocalization of integrin αv and β1 in focal adhesion. Furthermore, phosphorylation of SMAD2 and SMAD3 were significantly increased and SMAD3 translocated from cytoplasm to nucleus after TN-C addition. Inhibition of TGF-β type I receptor (SB-505124) or SMAD3 (SIS3) suppressed the expression of α-SMA and calponin after TN-C treatment. [Conclusion] TNC could contribute cancer stroma formation characteristics of breast cancer tissues, following induction of phenotypical change to myofibroblasts and enhanced stromal contraction via integrin αvβ1/TGF-β/SMAD signaling. Phenotypic differences between HMFs and HDFs after TN-C administration may be present.

Citation Format: Daisuke Katoh, Aya Noro, Kyoko Imanaka-Yoshida, Tomoko Ogawa, Toshimichi Yoshida. Tenascin-C promotes the activation of mammary fibroblasts to calponin-expressing myofibroblasts [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1907.