43P - Examination of the role of integrin β3 in chemoresistance by analysis of residual NACT tumor specimens and knock-in experiments

Date 04 May 2017
Event IMPAKT 2017
Session Welcome reception and Poster Walk
Topics Breast Cancer
Pathology/Molecular Biology
Presenter Madhumathy Nair
Authors M.G. Nair1, J.S. Prabhu1, J. Remacle1, H.P. S1, A. Korlimarla1, R.S. Kaluve1, A. Alexander1, S. Patil2, S.B. S2, S.T. Srinivas1
  • 1Molecular Medicine, St. John's Research Institute, 560 034 - Bangalore/IN
  • 2Medical Oncology, Sri Shankara Cancer Hospital and Research Centre, 560004 - Bangalore/IN

Abstract

Body

Introduction

Integrin β3/CD61 is known to be involved in breast tumor initiation and progression. We have recently reported that integrin β3 signalling inhibits apoptosis induced by an anthracycline in breast cancer cells by repression of the pro-apoptotic BAD [Nair MG et al, Experimental Cell Research, (2016):346(1), 137-145]. In the present study we have evaluated the levels of integrin β3 and Bcl-2 in NACT treated residual tumor samples. We also over-expressed integrin β3 in a luminal cell line, MCF7 and examined the consequence on chemosensitivity.

Methods:

Tumor collection, immunohistochemistry and gene expression : We tested 54 stage III & IV specimens from non and partial responders to NACT regimens containing anthracyclines and/or taxanes. 43 had adequate tissue for further analysis. Of the 43, 37 qualified for gene expression analysis and 34 had sufficient tissue for performing IHC for integrin β3 and Bcl-2.

Transfection and evaluation of drug cytotoxicity : Transient over-expression of integrin β3 in MCF7 cells was accomplished with integrin β3 CRISPR Activation Plasmid. Over-expression was confirmed using western blot, immunofluorescence, flow cytometry and q-RT PCR. Cells were exposed to multiple doses of epirubicin and response evaluated by MTT 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay.

Results:

More than half (19/34) of the residual tumors showed expression of integrin β3. 68% of the integrin β3 positive tumors had Bcl-2 protein positivity indicating the prescence of an anti-apoptotic response. The proportion of integrin β3 expressing tumors differed by ER status with three quarters of ER positives (12/17) having high expression compared to only half of ER negatives (7/17). Transient transfection of integrin β3 in MCF7 led to a decreased sensitivity to epirubicin supporting a direct relationship between the levels of integrin β3 and chemoresistance to anthracyclines.

Discussion

Our results suggest a role for integrin β3 in intrinsic chemoresistance to breast tumors in general and luminal tumors in particular. Patients with high level of integrin β3 can be targeted with specific inhibitors that are currently in clinical trials.

Clinical trial identification

NOT APPLICABLE