Resistance to HER2-targeted anti-cancer drugs is associated with immune evasion in cancer cells and their derived extracellular vesicles

ABSTRACT

Neuromedin U (NmU) -a neuropeptide belonging to the neuromedin family– plays a substantial role in HER2-positive breast cancer, correlating with increased aggressiveness, resistance to HER2-targeted therapies and overall significantly poorer outcome for patients. However, the mechanism through which it exerts these effects remains unclear. To elucidate this, initially we used HER2-positive breast cancer cells stably over-expressing NmU. These cells and their released extracellular vesicles (EVs) had increased amounts of the immunosuppressive cytokine TGFβ₁ and the lymphocyte activation inhibitor PD-L1. Furthermore, these cells also showed enhanced resistance to antibody-dependent cell cytotoxicity (ADCC) mediated by trastuzumab, indicating a role of NmU in enhancing immune evasion. All these features were also found in HER2-targeted drug-resistant cells which we previously found to express higher levels of NmU than their drug-sensitive counterparts. Interestingly, EVs from drug-resistant cells were able to increase levels of TGFβ₁ in drug-sensitive cells. In our neo-adjuvant clinical trial, TGFβ₁ levels were significantly higher in EVs isolated from the serum of patients with HER2-overexpressing breast cancers who went on to not respond to HER2-targeted drug treatment, compared with those who experienced complete or partial response. Taken together, our results report a new mechanism-of-action for NmU in HER2-overexpressing breast cancer that enhances resistance to the anti-tumor immune response. Furthermore, EV levels of TGFβ₁ correlating with patients' response versus resistance to HER2-targeted drugs suggests a potential use of EV-TGFβ₁ as a minimally-invasive companion diagnostic for such treatment in breast cancer.

KEYWORDS:

• biomarker
• extracellular vesicles: exosomes
• immune evasion
• neo-adjuvant clinical trial
• Neuromedin U

Disclosure statement

JC has acted in a consultancy role for GSK and has received honoraria and other remuneration from Roche and GSK. None of these monies were used for any of these studies and no drugs used were received as a gift from any company. There is no other disclosure to report.

Acknowledgments

The authors wish to acknowledge the All Ireland Cooperative Oncology Research Group (ICORG/Cancer Trials Ireland) for facilitating the neo-adjuvant clinical trial (ICORG: 10–05; NCT01485926) and Ms. Laura Ivers for help with specimen collection. We wish to thank Mr. Neal Leddy for his transmission electron microscopy expertise.

Funding details

This work was supported by HRB's Health Research Award under grant HRA-POR-2014–658; Breast Cancer Now under grant 2015NovSP68; Irish Cancer Society's Breast-Predict under grant CCRC13GAL; H2020 COST Action ME-HaD under grant BM1202; and Science Foundation Ireland's support, under grant 12/RI/2340(7) of the FACS equipment used.