Galectin-3 enhances trastuzumab resistance by regulating cancer malignancy and stemness in HER2-positive breast cancer cells

Purpose: The aim of this study was to explore the role of Galectin-3 in human epidermal growth factor receptor 2 (HER2)-positive breast Cancer cells and the potential mechanism.

Methods: Kaplan-Meier (KM)-plot and The Cancer Genome Atlas (TCGA) databases were used to study the role of Galectin-3 in the prognosis of HER2-positive breast Cancer. The effects of Galectin-3 on cell proliferation, migration, invasion, and colony formation ability in HER2-positive breast Cancer cells were examined. The relationship between Galectin-3 and important components in the HER2 pathways, including HER2, epidermal growth factor receptor (EGFR), protein kinase B (Akt), and Phosphatase and tensin homolog (PTEN), was further studied. Lentivirus and CRISPR/Cas9 were used to construct stable cell lines. Cell counting kit-8 (CCK-8) and Apoptosis assays were used to study the relationship between Galectin-3 and trastuzumab. The effect of Galectin-3 on cell stemness was studied by mammosphere formation assay. The effects of Galectin-3 on stemness biomarkers and the Notch1 pathway were examined. Tumorigenic models were used to evaluate the effects of Galectin-3 on tumorigenesis and the therapeutic effect of trastuzumab in vivo.

Results: HER2-positive breast Cancer patients with a high expression level of LGALS3 (the gene encoding Galectin-3) messenger RNA (mRNA) showed a poor prognosis. Galectin-3 promoted Cancer malignancy through phosphoinositide 3-kinase (PI3K)/Akt signaling pathway activation and upregulated stemness by activating the Notch1 signaling pathway in HER2-positive breast Cancer cells. These two factors contributed to the enhancement of trastuzumab resistance in cells. Knockout of LGALS3 had a synergistic therapeutic effect with trastuzumab both in vitro and in vivo.

Conclusions: Galectin-3 may represent a prognostic predictor and therapeutic target for HER2-positive breast Cancer.