1165 PDT-resistant skin tumor cells secrete CCL2 to induce TAMs recruitment and suppressive tumor microenvironment

Photodynamic therapy (PDT) is a promising method for skin pre-cancerous lesions and tumors. During PDT, photosensitizer (PS) activated by the appropriate wavelength of light in an oxygen environment to produce reactive species tumor-killing. Generally, photodynamic requires repeated treatment cycles, which can potentially induce resistance become increasing awareness clinical work. However, its biological mechanism not fully elucidated. Our study demonstrated that tumor cells (murine melanoma cell line Yumm1.7) became PDT-resistant protect themselves against ROS had enhanced anti-oxidation migration capacities. Meanwhile, (Yumm1.7 R), CCL2 secretion increased 15.9-fold (p<0.01) vitro, recruit tumor-associated-macrophages (TAMs) into microenvironment, promote M2-type polarization PD-L1 expression C57BL/6 mice orthotopic models tumor. According animal studies, blocking strongly reduces growth preventing recruitment TAMs limiting density macrophages, inhibiting expression, therefore, potentiates antitumor efficacy CD8+ T break PDT barrier. Thus, our findings illustrate role influencing phenotypes functions overcoming suppressive microenvironment resistance. And also provide new insight immune evasion mediated TAMs, indicating potential TAMs-targeted strategies