Posttranslational remodeling micelle reverses cell-surface and exosomal PD-L1 immunosuppression in tumors resistant to PD-L1 antibody therapy

Abstract

Sustained replenishment of cell-surface and exosomal PD-L1 has been believed as the most important factor in the progression of PD-L1 antibody therapy resistance. Given that direct genetic blockade of PD-L1 may lead to unintended consequences and that posttranslational modifications (PTMs) are often used as pharmacological targets of cancer therapy, approaches targeting PD-L1 PTMs show great potential as new therapeutic paradigms. Palmitoylation has emerged as a critical PTM for modulating PD-L1 stability and distribution. In this work, it is found that disruption of palmitoylation by 2-bromopalmitate (2-BP) dual-impaired PD-L1 on the cell surface and exosomes. An amphiphilic TME-responsive micelle was fabricated to efficiently deliver 2-BP and the chemotherapeutic agent cisplatin to tumor milieu. The composite formulation unifying elimination of cell-surface and exosomal PD-L1 with chemotherapy synergistically relieved immunosuppression in the tumor bed and draining lymph node, thereby dramatically restraining growth, postsurgical relapse, and metastasis in melanoma resistant to PD-L1 antibody therapy. Moreover, the formulation elicits potent T cell memory responses for long-term protection against tumor rechallenge. In summary, our study takes advantage of an amphiphilic nanoformula combination of a posttranslational modifier and chemotherapy to target tumors resistant to PD-L1 antibody therapy, and paves a new path for multimodal cancer treatment.