Galectin-1 binding to HER2+ human breast cancer cells induces cancer stemness and modulates sensitivity to Trastuzumab therapy

MARIÑO KV; PERROTA RM; RABINOVICH GA; DALOTTO-MORENO T; SALATINO, M; CAGNONI A

Conferencia; Second AACR International Conference TRANSLATIONAL CANCER MEDICINE; 2018

Galectins decode glycan-containing information in a number of cell receptors adjusting signaling thresholds and modulating cellular functions. In particular, galectin-1 (Gal1), a 14kD prototype galectin, binds to terminal N-acetyllactosamine residues on glycosylated proteins in the absence of α2-6 sialic acid (SA) capping (Gal1 permissive glycophenotype) promoting tumor immune suppression and sustaining aberrant angiogenesis. Here, we aim to explore the glycosylation signature of HER2+ breast cancer cells to investigate if Gal1 is involved in resistance to trastuzumab (TZ) targeted therapy. We first selected three HER2+ human breast cancer cell lines with different response to TZ: JIMT-1 (resistant-TZR), BT-474 and SK-BR-3 (sensitive-TZS). We found that TZS cell lines exhibited a Gal-1 restrictive glycophenotype characterized by high α2,6 SA capping and high expression of ST6GAL1 (glycosyltransferase responsible for adding α2,6 SA) compared to TZR JIMT-1.In accordance with the glycophenotype, TZR cell line bound and expressed higher levels of Gal1 when compared to TZS cell lines by Western blot, RT-PCR and ELISA of conditioned medium, suggesting a positive autocrine loop that could modulate TZ resistance.Additionally, in silico analysis of data from the Long HER Study (GSE44272) revealed that patients with poor response (PR) to TZ expressed higher levels of Gal1 mRNA than long-term responders. Cancer stem cells (CSC) represent a subpopulation of tumor cells with capacity of self-renewal and differentiation to drive initiation, growth and metastasis. Moreover,breast CSC (CD44+/CD24-/ALDH1+) exhibit resistance to anti-cancer treatments promoting tumor recurrence. Herein, exposure of TZRJIMT-1 cell lineto Gal-1, increase CD44+/CD24−/low/Aldh1hipopulation and, also increasing EMT (Snail, Slug, Vimentin) and differentiation (NANOG) markers. In addition, in vitro migration and mamosphere formation were induced upon Gal1 treatment. Moreover, BT-474 TZ sensitive cell line exposed to Gal1 showed an increase in Aldh1hi population only after sialic acid removal. Importantly, gal1-induced CSC phenotype was reversed by the addition of an anti-Gal-1 antibody indicating that the effect was specific. These results were supported by analysis of public databases arrays (GSE62327) showing that patients who presented complete response to TZ exhibited higher levels of ST6GAL1 than PR patients. Furthermore, PR patients displayed lower CD24 expression and higher Aldh1reinforcing our hypothesis from a clinical standpoint. In summary, our study demonstrates that individual HER2+ human breast cancer cells display particular ?glycosylation signatures? which in association with Gal1 expression and binding patterns, promote an increase in breast CSC favoring resistance to anti-HER2 targeted therapy. Our results suggest that in the futurethe information contained in the Gal1/glycan axis may be considered to predict breast cancer clinical outcome and response to targeted therapies.