An iRGD peptide fused superantigen mutant induced tumor-targeting and T lymphocyte infiltrating in cancer immunotherapy.

Solid tumors are intrinsically resistant to immunotherapy because of the major challenges including the immunosuppression and poor penetration of drugs and lymphocytes into solid tumors due to the complicated tumor microenvironment (TME). Our previous study has created a novel superantigen mutant ST-4 to efficiently active the T lymphocytes and alleviate immune suppression. In the present study, to accumulate ST-4 into the TME, we constructed a recombinant protein, ST-4-iRGD, by fusing ST-4 to a tumor-homing peptide, iRGD. We hypothesized that ST-4-iRGD could internalize into the TME through iRGD-mediated tumor targeting and tumor tissue penetrating to activate the regional immunoreaction. The results of in vitro studies showed that ST-4-iRGD achieved improved tumor targeting and cytotoxicity in mouse B16F10 melanoma cells. The iRGD-mediated tumor tissue penetration was further confirmed by imaging and immunofluorescence studies in vivo, wherein higher distribution of ST-4-iRGD was observed in the mouse 4T1 breast tumor model. Moreover, ST-4-iRGD exhibited enhanced anti-solid tumor characteristics and induced improved lymphocyte infiltration in the B16F10 and 4T1 models. In conclusion, using iRGD to facilitate better dissemination of the therapeutic agent ST-4 throughout a solid tumor mass is feasible, and ST-4-iRGD may be a potential candidate for efficient cancer immunotherapy in the future.