Chemotherapy-Induced Macrophage Infiltration into Tumors Enhances Nanographene-Based Photodynamic Therapy.

Increased recruitment of tumor-associated macrophages (TAM) to tumors following chemotherapy promotes tumor resistance and recurrence and correlates with poor prognosis. TAM depletion suppresses tumor growth, but is not highly effective due to the effects of tumorigenic mediators from other stromal sources. Here, we report that adoptive macrophage transfer led to a dramatically enhanced photodynamic therapy (PDT) effect of 2-(1-hexyloxyethyl)-2-devinyl pyropheophor-bide-alpha (HPPH)-coated polyethylene glycosylated nanographene oxide [GO(HPPH)-PEG] by increasing its tumor accumulation. Moreover, tumor treatment with commonly used chemotherapeutic drugs induced an increase in macrophage infiltration into tumors, which also enhanced tumor uptake and the PDT effects of GO(HPPH)-PEG, resulting in tumor eradication. Macrophage recruitment to tumors after chemotherapy was visualized noninvasively by near-infrared fluorescence and single-photon emission CT imaging using F4/80-specific imaging probes. Our results demonstrate that chemotherapy combined with GO(HPPH)-PEG PDT is a promising strategy for the treatment of tumors, especially those resistant to chemotherapy. Furthermore, TAM-targeted molecular imaging could potentially be used to predict the efficacy of combination therapy and select patients who would most benefit from this treatment approach. .