Reconfiguration of tumor cells with LCOR transcription factor mRNA nanotherapy to enhance immunotherapy efficacy

Abstract Transcription factors (TFs) are generally deemed undruggable due to their structural complexity. mRNA technologies have paved the way to overcome this therapeutic limitation by enabling the development of mRNA protein replacement therapies. Here we explore the newly described TF activity of LCOR (Ligand-dependent corepressor), which suppresses tumor growth by inducing the antigen presentation machinery (APM) of the tumor cells and constrains cellular plasticity. These LCOR effects facilitate recognition of the tumor by the immune system and immune-mediated tumor cell death. To deliver Lcor mRNA into tumor cells, we have used poly β-(amino esters) (pBAE) nanoparticles (NPs) for local delivery of Lcor mRNA in breast cancer primary tumor models. We have engineered pBAE-NPs with high potential for efficiently encapsulate mRNA and facilitate cellular uptake. Our results show optimal endosomal escape, which results in high transfection efficiency in vitro and in vivo, restoring LCOR function in tumor cells and engaging their APM. In preclinical triple-negative breast cancer (TNBC) models, the intratumoral delivery of Lcor mRNA led to a reduction in tumor growth. Importantly, the combination of Lcor mRNA-loaded NPs with anti-PDL1 or anti-CTLA4 immunotherapies eradicated most of the tumors in our preclinical TNBC model. Overall, our nanotherapeutic strategy emerges as an innovative TF-replacement therapy, leveraging the immunogenic effects of LCOR to eradicate breast cancer tumors when combined with immunotherapy. Competing Interest Statement HMRI has filed three patents related to the findings of this study, with T.C.-T., G.S.-M., J.A.P., & S.B.-B. named as coinventors. List of abbreviations - 1HNMR - Proton nuclear magnetic resonance - 3D - Three-dimensional - 5-moU - 5-methoxyuracil - APM - Antigen presentation machinery - ATCC - American Type Culture Collection - BSA - Bovine Serum Albumin - CTLA4 - Cytotoxic T-lymphocyte associated protein 4 - Cy - Cyanine - DBD - DNA binding domain - DLS - Dynamic light scattering - DMEM - Dulbecco’s Modified Eagle’s Medium - DMSO - Dimethyl sulfoxide - ECL - Enhanced chemiluminescence - eGFP - Enhanced green fluorescent protein - FBS - Fetal bovine serum - Fluc - Firefly luciferase - FRET - Fluorescence resonance energy transfer - HTH - Helix-turn-helix - i.p. - Intraperitoneal - i.t. - Intratumoral - ICB - Immune checkpoint blockade - ICI - Immune-checkpoint inhibitor - IFN-γ - Interferon-gamma - LCOR - Ligand-dependent corepressor - NP - Nanoparticle - OVA - Ovalbumin - pBAE - Poly β-(amino esters) - PBS - Phosphate buffer saline - PDI - Poly-dispersity index - PDL1 - Programmed Death-ligand 1 - SOC - Standard-of-care - STR - Short tandem repeat - TF - Transcription factor - TNBC - Triple negative breast cancer - UTR - Untranslated regions