TGF-β inhibition enhances chemotherapy action against triple-negative breast cancer
Neil E. Bhola, Justin M. Balko, Teresa C. Dugger, María Gabriela Kuba, Violeta Sánchez, Melinda Sanders, Jamie Stanford, Rebecca S. Cook, Carlos L. Arteaga
Neil E. Bhola, Justin M. Balko, Teresa C. Dugger, María Gabriela Kuba, Violeta Sánchez, Melinda Sanders, Jamie Stanford, Rebecca S. Cook, Carlos L. Arteaga
View: Text | PDF
Research Article Oncology

TGF-β inhibition enhances chemotherapy action against triple-negative breast cancer

Abstract

After an initial response to chemotherapy, many patients with triple-negative breast cancer (TNBC) have recurrence of drug-resistant metastatic disease. Studies with TNBC cells suggest that chemotherapy-resistant populations of cancer stem-like cells (CSCs) with self-renewing and tumor-initiating capacities are responsible for these relapses. TGF-β has been shown to increase stem-like properties in human breast cancer cells. We analyzed RNA expression in matched pairs of primary breast cancer biopsies before and after chemotherapy. Biopsies after chemotherapy displayed increased RNA transcripts of genes associated with CSCs and TGF-β signaling. In TNBC cell lines and mouse xenografts, the chemotherapeutic drug paclitaxel increased autocrine TGF-β signaling and IL-8 expression and enriched for CSCs, as indicated by mammosphere formation and CSC markers. The TGF-β type I receptor kinase inhibitor LY2157299, a neutralizing TGF-β type II receptor antibody, and SMAD4 siRNA all blocked paclitaxel-induced IL8 transcription and CSC expansion. Moreover, treatment of TNBC xenografts with LY2157299 prevented reestablishment of tumors after paclitaxel treatment. These data suggest that chemotherapy-induced TGF-β signaling enhances tumor recurrence through IL-8–dependent expansion of CSCs and that TGF-β pathway inhibitors prevent the development of drug-resistant CSCs. These findings support testing a combination of TGF-β inhibitors and anticancer chemotherapy in patients with TNBC.

Authors

Neil E. Bhola, Justin M. Balko, Teresa C. Dugger, María Gabriela Kuba, Violeta Sánchez, Melinda Sanders, Jamie Stanford, Rebecca S. Cook, Carlos L. Arteaga

×

Figure 6

TGF-β inhibition in vivo abrogates tumor-initiating potential after chemotherapy.

Options: View larger image (or click on image) Download as PowerPoint
TGF-β inhibition in vivo abrogates tumor-initiating potential after chem...
(A–C) Female athymic mice were injected with SUM159 cells in the number 4 mammary fat pad. (A) Once tumors reached a volume of ≥75 mm3, mice were randomized to 4 treatment groups (n = 10 mice per group): (a) vehicle (control), (b) LY2157299 (100 mg/kg/p.o. twice daily), (c) paclitaxel (20 mg/kg/d i.p. 5 times), and (d) both drugs. The arrow at day 5 represents the cessation of paclitaxel treatment. The arrow and star at day 15 indicate the cessation of LY2157299 treatment and the procurement of xenografts, respectively. The arrow at day 23 represents the cessation of monitoring for tumor growth. Lysates from xenografts harvested after (B) 5 days and (C) 14 days were assessed for total SMAD2/3 and P-SMAD2 levels by immunoblot analysis. (D) Tumor volumes calculated on day 14 (*P = 0.035; Mann-Whitney). Symbols indicate individual tumors; horizontal bars represent the mean. (E) Single cell suspensions derived from xenografts harvested on day 14 were analyzed for ALDH activity using the ALDEFLUOR assay (*P = 0.002). (F) Serum was collected from mice at the time of tumor harvesting and sacrifice and analyzed for IL-8 protein levels by ELISA. Each bar represents mean IL-8 levels over control ± SEM (n = 3). ns, not significant. (G) Progression of tumor volumes during days 14–23 in mice treated with paclitaxel with or without LY2157299 during days 1–14 (n = 5). Tumors treated with vehicle (controls) or LY2157299 alone are not included, as they had reached a volume of ≥1 cm3 on day 14 (start of x axis). Because of the large tumor burden, these mice had to be sacrificed as per institutional guidelines. Error bars indicate SEM.