We developed a novel treatment strategy for metastatic
cancer by synergizing
photothermal therapy (PTT),
chemotherapy, and
immunotherapy through a nanosystem to trigger host antitumor immunity. The nanosystem was constructed by loading
mitoxantrone (MTX), a chemotherapeutic agent, and
SB-431542 (SB), a
transforming growth factor beta (TGF-β) inhibitor, onto reduced
graphene oxide (rGO). Intratumoral administration of rGO/MTX/SB, followed by non-invasive irradiation of a near-infrared
laser, destroyed local primary
tumors and inhibited distant
metastases in 4T1 mouse mammary
tumor model, which is poorly immunogenic and highly metastatic.
After treatment, 70% of the
tumor-bearing mice became long-term survivors and developed a
tumor type-specific immunity to resist rechallenged
tumor cells. We found that rGO-based PTT provided an immunogenic
antigen source, forming in situ vaccination with rGO as an immune-adjuvant. The use of SB changed the tumor microenvironment and improved the
therapeutic effect of MTX-generated
chemotherapy and rGO-based PTT. The immunological functions of MTX, SB, and rGO acted synergistically to induce an effective
tumor vaccination, as evidenced by the increased infiltration of
tumor-specific cytotoxic CD8+ T lymphocytes and decreased infiltration of regulatory T cells (Tregs) in distal
tumors. Collectively, we demonstrated that rGO/MTX/SB combined with
laser irradiation provided a synergistic chemo-immuno-photothermal effect against
tumors by in situ vaccination and inhibition of immunosuppressive microenvironment. This unique combination embodies a promising approach to treat metastatic
cancers by inducing a systemic antitumor response through a local intervention.