Theranostic CuS/ALA Nanoprobes Modulate Drug Efflux Pumps and Synergize the Photoacoustics-Guided Photothermal Breast Cancer Therapy.

Breast cancer remains a clinical hurdle despite technoclinical advancements, primarily due to drug resistance mechanisms, from overexpression of drug efflux pumps. Modulating drug efflux/influx transporters like ABCG2 and HCP-1 can improve anticancer therapeutic approaches. Our study reports CuS-ALA metal-organic nanoprobes combining 5-aminolevulinic acid (5-ALA), a tumor targeting biomolecule, and near-infrared (NIR) light-absorbing copper sulfide (CuS) nanoparticles. These ALA-CuS nanoprobes (NPs) had excellent near-infrared (NIR) absorption properties along with high photothermal profile, stability, photoacoustic and fluorescence imaging properties. In vitro studies in breast cancer cell lines revealed uniform internalization and exhibited a synergistic cytotoxic effect in the case of ALA-CuS NPs when exposed to a NIR 808 nm light. Further mechanistic studies have revealed that these nanoprobes could target and modulate drug transporters, such as ABCG2 and HCP1, indicating their efficient role in targeted downregulation of resistance pathways and activating photodynamic and photothermal therapies-mediated intrinsic apoptotic cell death pathways in breast cancer. Furthermore, the ALA-CuS NPs were effective for the photoacoustic image-guided delivery when evaluated in a preclinical 4T1 syngeneic breast tumor model. The fluorescence biodistribution profile revealed that these nanoprobes were preferentially accumulated in the tumor, liver, and kidneys and revealed negligible toxic effects. However, following the NIR irradiation, the ALA-CuS NPs treated tumors were effectively ablated without obvious tumor recurrence within 21 days. Moreover, they reduced hypoxia, promoting tumor regression when combined with NIR light. Overall, the proposed ALA-CuS NPs could be a promising translational formulation for targeting drug resistance and aiding in synergizing multimodal theranostics-based breast cancer therapy.