p53 mRNA rescue of tumor suppressor function prevents tumor growth and restores PARPi sensitivity in p53-deficient cancers in vitro and in vivo

Background: Loss of function in tumor suppressor genes is commonly associated with the onset/progression of cancer and the development of therapeutic resistance. The p53 tumor suppressor mutations resulting in loss of function are common across variety of tumors and control tumor cell proliferation in more than 50% of cancers. P53 null mutations are present in about 10% of p53 driven cancers. However, to date there is no effective treatment for rescuing p53 function in cancers. We have developed a new potent strategy combing p53 mRNA with a tumor selective nanocarrier, to rescue p53 tumor suppressor function as potential therapeutic approach in cancers. Methods: ADGN-technology is based on short amphipathic peptides that form stable neutral nanoparticles with mRNA. ADGN-531 nanoparticles containing full length p53-mRNA were evaluated on 20 different cancer cell lines (osteosarcoma, pancreas, colorectal, ovarian, lung, breast and prostate cancers) harboring different types of p53 mutations (null, deletion, nonsense, missense). Cell proliferation, cell cycle level and apoptosis activation were determined by flow cytometry, Elisa and Tunel assay. In-vivo efficacy of IV-administered ADGN-531 nanoparticles (0.5 mg/kg) was evaluated on colorectal SW403 (p53 deleted) and osteosarcoma SaOs2 (p53 null) mouse xenografts. Sensitivity to Veliparib (PARPi) following ADGN-531 treatment in vitro was evaluated on PARPI resistant SUM-149PT and OVCAR-8 cells and on PARPi sensitive MDA-MB436 cells. Results: ADGN-531 NPs markedly delay the growth of a large panel of cancer cells harboring p53-null or nonsense mutations, by inducing cell cycle arrest in G1 due to p21 upregulation and apoptosis following PUMA activation. We demonstrated that ADGN-531 mediated p53 function rescue is directly correlated to the type and level of p53 mutation in the cancer cells. ADGN-531 induces 60% to 80% cell proliferation inhibition in p53 null or nonsense mutated cells and 20 to 50% in p53 missense mutated cells. Intravenous-administration ADGN-531 containing wild type p53-mRNA (0.5 mg/kg) resulted in tumor growth inhibition of 90% and 70% in SaOs2 and SW403 xenografted mouse model, respectively. ADGN-531 NPs treatments are well tolerated, without inducing clinical toxicity or inflammatory response. We demonstrated that ADGN-531 mediated p53 rescue markedly improves (200 fold) and restores the sensitivity of ovarian and breast cancer cells to the PARPi veliparib. Conclusions: ADGN-531 nanoparticles are effective in rescuing P53 functions both in vitro and in vivo. Our study provides a proof-of-concept that restoration of tumor suppressor function by the ADGN-531 NP targeted delivery strategy could be combined together with other therapies for potent combinatorial cancer treatment. No conflict of interest.