The Study On The Effect And Mechanism Of Radiotherapy Combined With Erb-?IL10?₂ In The Treatment Of Malignant Melanoma

Purpose:Local high-dose radiotherapy?RT?effectively kills tumor cells and modifies the tumor microenvironment to influence the antitumor immunity of host.Interleukin-10?IL-10?is considered as an immune suppressive cytokine.However,higher local concentrations of IL-10 led to tumor rejections and inhibited tumor metastasis in mice.An anti-EGFR antibody and IL-10 heterodimeric fusion protein Erb-?IL10?₂ targeting the extracellular regions of tumor overexpressed epidermal growth factor receptor?EGFR?to enable local delivery of IL-10 into tumor microenvironment has the ability to inhibit tumor growth.We hypothesized that RT in combination with Erb-?IL10?₂ provides an synergistic antitumor effect dependent EGFR expression in a mouse malignant melanoma model.Methods:B16-EGFR-SIY malignant melanoma cells were injected subcutaneously?s.c.?into the both flanks of mice then administered single dose local RT and/or Erb-?IL10?₂ or equimolar controls to evaluate the therapeutic effect of combination therapy.Tumor growth,side effects,immunologic parameters,and underlying therapeutic mechanisms were evaluated after treatment.Results:The ability of eliminating tumors of local single high dose RT was enhanced with increasing dose from 5Gy to 30Gy.Local single dose RT 10Gy had no effect on the nonirradiated tumors.Conversely,the combination therapy of RT 10Gy and Erb-?IL10?₂1mg/kg not only reduced tumor cells on the primary radiated site?p=0.0349?,but also improved antitumor response on distant non-irradiated site?p=0.0009?.Moreover,administration of Erb-?IL10?₂ at 3 days post RT exerted most powerful synergistic therapeutic effect of the combination therapy.Depletion of CD4⁺T cells or NK cells only slightly reduced the synergistic effect of combination therapy,however,depletion of CD8⁺T cells drastically affected its therapeutic effect,leading to tumor growth rapidly?p=0.0376?.By detecting the frequency of SIY-specific IFN-?produced by CD8⁺T cells in tumor-draining lymph nodes?DLNs?,we found that combination therapy significantly enhanced tumor antigen-specific T cell responses compared with underwent RT or Erb-?IL10?₂ treatment alone.Conclusions:Our data provide the primary evidence for this finding the synergistic therapeutic potential for combining RT with Erb-?IL10?₂ in EGFR overexpressed tumors.And we found CD8⁺T cells are critical in the combination therapy.Tumor antigen–specific T cell responses were significantly enhanced to help remove the distant tumors.This study provides strong preclinical evidence for the combined trial of malignant melanoma patients.