High expression of intratumoral stromal proteins is associated with chemotherapy resistance in breast cancer

// Tingting Wang 1 , Supriya Srivastava 1 , Mikael Hartman 3, 4 , Shaik Ahmad Buhari 3 , Ching-Wan Chan 3 , Philip Iau 3 , Lay Wai Khin 4 , Andrea Wong 2 , Sing-Huang Tan 2 , Boon-Cher Goh 1, 2 , Soo-Chin Lee 1, 2 1 Cancer Science Institute, National University of Singapore, Singapore 2 Department of Haematology and Oncology, National University Cancer Institute, National University Health System, Singapore 3 Department of Surgery, National University Cancer Institute, National University Health System, Singapore 4 Saw Swee Hock School of Public Health, National University of Singapore, Singapore Correspondence to: Soo-Chin Lee, email: csilsc@nus.edu.sg Keywords: breast cancer, chemotherapy resistance, cancer-associated stromal protein, integrin β, mTOR pathway Received: December 29, 2015 Accepted: July 06, 2016 Published: July 28, 2016 ABSTRACT We studied the changes of intratumoral stromal proteins including THBS1, TNC, FN, SPARC and α-SMA, following neoadjuvant chemotherapy. The underlying mechanisms by which THBS1 and TNC regulated resistance to docetaxel were further studied using functional studies. 100 patients with newly diagnosed breast cancer were treated with alternating sequential doxorubicin and docetaxel. Immunohistochemistry (IHC) staining for stromal proteins was performed on pre- and post-treatment core biopsies respectively. THBS1 and TNC were further validated with IHC in an independent cohort of 31 patients. A high baseline combined expression score of the 5 stromal proteins predicted independently for poor progression-free (HR adjusted 2.22, 95% CI 1.06–4.64) and overall survival (HR adjusted 5.94, 95% CI 2.25–15.71). After 1–2 cycles of chemotherapy, increased expression of THBS1, TNC, FN, SPARC and α-SMA was seen in patients with subsequent pathological lymph node involvement at surgery. Increased expression of THBS1 and TNC compared to baseline was also seen in intrinsically resistant tumors, but not in sensitive ones. Both THBS1 and TNC-associated chemoresistance were confirmed in an independent validation cohort. Exogenous THBS1 and TNC protected MCF-7 cells against proliferation inhibition induced by docetaxel through activating integrin β1/mTOR pathway. Thus, up-regulation of THBS1, TNC, FN, SPARC and α-SMA following neoadjuvant chemotherapy was associated with chemotherapy resistance in breast cancer patients. Functional studies showed THBS1 and TNC to mediate chemoresistance through the integrin β1/mTOR pathway, suggesting that therapies targeting integrin β1/mTOR pathway may be a promising strategy to overcome chemotherapy resistance.