Near-infrared photothermal therapy using EGFR-targeted gold nanoparticles increases autophagic cell death in breast cancer.

Although triple negative breast cancer (TNBC) is a small percentage of all breast cancers, to date, TNBC is one of the most challenging types of breast cancer for basic and clinic research because TNBC patients display a high risk of relapse, shorter overall survival and limited therapeutic options after completion of conventional chemotherapy compared with patients with other breast cancer subtypes. The epidermal growth factor receptor (EGFR) is a promising target for TNBC treatment. Although near infrared-photothermal therapy (NIR-PTT) using anti-EGFR antibody-conjugated gold nanorods (anti-EGFR-GNs), has attracted considerable interest for non-invasive and targeted TNBC treatment through an activation of apoptotic pathway, it is unclear whether anti-EGFR-GNs-combined NIR-PTT modulates the induction of autophagy contributing to cell death. Therefore, we investigated the autophagic cell death in cultured TNBC cells and mouse xenograft tumors during anti-EGFR-GNs-combined NIR-PTT. We here found that the cytotoxicity induced by anti-EGFR-GNs-combined NIR-PTT was rescued by treatment with autophagy inhibitor, 3-methyladenine (3-MA). Anti-EGFR-GNs-combined NIR-PTT induced remarkable levels of autophagy activity as evidenced by a large number of autophagic vesicles and a significant increase in autophagy-specific proteins; microtubule-associated protein light chain 3 (LC3), p62, beclin-1, and autophagy-related gene5 (Atg5), accompanying the inhibition of AKT-mTOR signaling pathway responsible for inducing autophagy. Moreover, in mouse xenograft tumors, anti-EGFR-GNs-combined NIR-PTT also increased LC3 and beclin-1 levels. Our findings, for the first time, demonstrate that anti-EGFR-GNs-combined NIR-PTT remarkably induces autophagy leading to EGFR-targeted cancer cell death.