Abstract LB-116: Neuromedin U drives increased expression of TGFβ1 in HER2-positive breast cancer cells and their extracellular vesicles: a novel biomarker of response to HER-targeted drugs
Authors: Martinez Vanesa G. , O’Driscoll Lorraine 
Published: July 2016

HER-targeted therapies are an attractive approach for HER2-overexpressing breast cancer; unfortunately, not all tumours are responsive and some that initially respond later develop resistance to therapy. Such drug-resistance is often associated with enhanced evasion from the anti-tumour immune response, further compromising the outcome for patients. Neuromedin U (NmU) is a neuropeptide belonging to the neuromedin family. Recently, a significant association between NmU signalling and cancer has been described by our group, with NmU expression correlated with increased aggressiveness and resistance to targeted anti-cancer therapy, although the mechanism through which it exerts this effect remains unexplained. To elucidate this mechanism and find out whether NmU also enhances immune evasion, HER2-positive breast cancer cells were cultured continuously in the presence of HER-targeting drugs lapatinib and neratinib to obtain resistant variants; cells stably transfected with NmU were also used. Extracellular vesicles (EVs) released by different cell variants were analysed for the presence of markers associated with immunosuppression. HER-targeted drug resistant cell lines showed increased secreted levels of TGFβ1, a well-known immunosuppressive cytokine produced by cancer stem cells. TGFβ1 levels were also increased in EVs derived from these cells; these effects were at least partly mediated by NmU, as overexpression of this peptide also resulted in increased TGFβ1 in cell supernatant and EVs. Blocking of TGFβ1 with a neutralising antibody decreased cell migration mediated by NmU, suggesting that TGFβ1 is a downstream mediator of NmU effects. Moreover, NmU-transfected cells also showed increased expression of EMT marker β-catenin, indicating increased function of TGFβ1 in NmU-overexpressing cells. Interestingly, TGFβ1 levels were substantially lower in EVs isolated from the serum of HER2-positive breast cancer patients showing complete (n = 13) or partial (n = 15) response to HER-targeting drug treatment compared to those that did not respond (n = 2). Altogether, our results show a new mechanism of action of NmU in HER2-positive breast cancer cells that promotes a more aggressive phenotype and likely enhances evasion of the anti-tumour immune response. Interestingly, EV levels of TGFβ1 correlate with levels of HER-targeted drug resistance, suggesting it could be used as a biomarker of response in breast cancer patients.

Acknowledgements: HRB's Health Research Award [HRA-POR-2014-658]; Irish Cancer Society's Breast-Predict [CCRC13GAL]; and HEA's PRTLI Cycle 5 support of TBSI.

Citation Format: Vanesa G. Martinez, Lorraine O’Driscoll. Neuromedin U drives increased expression of TGFβ1 in HER2-positive breast cancer cells and their extracellular vesicles: a novel biomarker of response to HER-targeted drugs. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr LB-116.