Faruqi, Fahad

e13106 Background: Chemotherapy resistance remains a significant barrier in the effective treatment of patients with triple negative breast cancer (TNBC). TGF-β signaling is a well characterized oncogenic pathway in TNBC that promotes chemoresistance by inducing epithelial to mesenchymal transition (EMT) and tumor stemness. Aurora-A kinase (AURKA) is a serine/threonine kinase responsible for chromosomal stability during mitosis. Significantly, aberrant expression of AURKA induces breast cancer progression. We hypothesized that aberrant activation of TGF-β and AURKA signaling pathways contributes to chemoresistance in TNBC by promoting EMT and tumor stemness and that dual-targeting of these oncoproteins will enhance chemosensitivity. Methods: RNA-Seq data were analyzed from patient derived xenografts (PDx) established from patients with Stage I-III TNBC who received pre-operative taxane and anthracycline based chemotherapy. Chemoresistance was defined as an RCB score of 1-3, and chemosensitivity was defined as an RCB score of 0. Unique TNBC cell lines developed from brain metastasis PDxs (TNBC M14, TNBC M25) were treated in vitro with 10nM docetaxel (DTX), 50nM LY2157299 (TGF-β inhibitor) and 50nM MLN8237 (AURKA inhibitor). EMT reprogramming was determined by measuring the expression of vimentin, ALDH activity and mammosphere growth. Apoptotic cells following drug treatment were labeled with Red Annexin-V marker and monitored in real time using the IncuCyte instrument. Results: RNA-Seq revealed that there was no baseline difference in expression of AURKA between chemoresistant and chemosensitive TNBC PDxs. However, there was a 2.7-fold increase in AURKA expression in the post-treatment PDx models compared to pre-treatment PDx models. In vitro treatment of the M14 and M25 cell lines with DTX demonstrated no significant increase in apoptotic cells compared to control, whereas treatment with the combination of DTX, LY2157299 and MLN8237 resulted in a two-fold increase in apoptosis compared to treatment with DTX alone (p = 0.0068 M14, p = 0.003 M25). Dual-targeting with LY2157299 and MLN8237 reduced the expression of vimentin and ALDH activity. Conclusions: TGF-β and AURKA play a central role inducing EMT and a stem-cell-like phenotype in TNBC that confers chemoresistance. AURKA is up-regulated after exposure to chemotherapy in chemoresistant TNBC PDx models. LY2157299 and MLN8237 reduce TNBC stemness in M14 and M25 cell lines and enhance DTX chemosensitivity. Dual-targeting of TGF-β and AURKA is a potentially promising approach in chemoresistant TNBC.

e23089 Background: Taxanes (paclitaxel and docetaxel) are commonly administered as part of chemotherapy for breast cancer, but long-term data on chemotherapy-induced peripheral neuropathy (CIPN) are limited in this population. We aimed to assess CIPN approximately three years after an initial exposure to paclitaxel or docetaxel. Methods: In a cross-sectional observation study, which surveyed consented enrollees annually after receipt of care at Mayo Clinic for a new breast cancer diagnosis over age 18, we collected patient-reported EORTC CIPN20 data by mailed questionnaire at baseline and three years after a breast cancer diagnosis. We then confirmed patient-reported chemotherapy data by chart abstraction and only included those who had received a standard course of docetaxel-based or paclitaxel-based chemotherapy, but had not had other neurotoxic treatment for cancer. CIPN20 overall and sensory scale raw scores were converted to a 0-100 linear scale with lower scores indicating more severe symptoms. Results: 84 women who received a taxane for breast cancer completed the survey. 82 were treated in the adjuvant or neo-adjuvant setting, while 2 received a taxane for metastatic breast cancer. 67 women received paclitaxel, while 17 received docetaxel. The median age at diagnosis was 51.5 years (range 31-86). 37 had estrogen receptor (ER) and/or progesterone receptor (PR) positive and human epidermal growth factor receptor-2 (Her2) negative, 31 Her2 positive, and 16 triple negative breast cancer. The median CIPN20 score was 92.98 (range 33.33-100). The median sensory CIPN score was 92.59 (range 25.94-100). 81% of women had an overall CIPN20 score of less than 100, and 68% had a sensory score of less than 100. Conclusions: The majority of women who received a taxane based chemotherapy regimen for breast cancer reported at least mild neuropathic symptoms three years out from treatment. Additional research is needed to help tailor chemotherapy decisions to toxicity risks and to reduce the likelihood of long-term CIPN, which can impair quality of life.