Hengji Zhang

Introduction. Melanoma occurs when melanocytes in the basal layer of epidermis become cancerous. Surgical resection of the tumor and surrounding tissue is the primary treatment for localized melanoma. Before the development of targeted therapies and immunotherapies, chemotherapy was often used for patients with metastatic cancer. The BRAF inhibitors, such as vemurafenib and dabrafenib, were approved targeted therapies for the treatment of metastatic and unresectable BRAF-mutated melanomas. Also, cancer immunotherapy (e.g. immune checkpoint inhibitors and cancer vaccines) provides promising approach to treat melanoma¹. Cancer immunotherapy relies on the immune system to recognize and kill cancer cells. Host immune system could be a powerful tool to enhance the cytotoxic therapy for cancer patients if the following strategies are developed: 1) neutralizing tumor-promoting inflammation; 2) modifying the tumor microenvironment to regulate T cell activity; 3) broadening T-cell repertories via vaccination.² Research studies have demonstrated that mRNA vaccines can induce a strong cytotoxic T Cells response to tumor cells.³ However, mRNA is known for poor stability in cells. Given this challenge, lipid nanoparticle assisting mRNA delivery emerges as a promising technology because: 1) its synthesis is robust, 2) it has high delivery efficiency but low toxicity, 3) adjuvants can be incorporated to further enhance the immune response. Methods. Lipid nanoparticles with mRNA, phospholipid, cholesterol, ionizable lipid, and lipid anchored PEG are produced with various size and compositions in a microfluidic chip device.⁴ The optimized formulation B-11 is shown to yield the highest immune response from the antigen specific CD8 T cells. To examine the location of mRNA transfection and protein synthesis, the firefly luciferase mRNA is incorporated in B-11 nanoparticle and injected in mouse. The mRNA encoding melanoma self-antigens, tyrosinase-related protein 2 and a point-mutated version of glycoprotein, is incorporated in nanoparticles to study its effect on the B16F10 tumor. The study also tests the effect of lipopolysaccharide (LPS) as an adjuvant. Results. Optimized lipid nanoparticles can deliver mRNA and transfect different immune cells, such as dendritic cells, macrophages, neutrophils, and B cells. For the aggressive B16F10 tumor mice model, mRNA coding (TRP2 and gp100) for the tumor associated self-antigens can overcome the self-tolerance effect and enhance the mice survival.⁴ Addition of lipopolysaccharide may increase the potency of mRNA delivered by lipid nanoparticles. Conclusions. These results demonstrate the potential of optimized lipid nanoparticles that can be used to deliver mRNA vaccines, induce a cytotoxic T cell response, and extend survival of animals with tumors.

1. Davis LE, Shalin SC, Tackett AJ. Current state of melanoma diagnosis and treatment. Cancer Biol Ther. 2019;20(11):1366-1379.
2. Palucka AK, Coussens LM. The Basis of Oncoimmunology. Cell. 2016;164(6):1233-1247. doi:10.1016/j.cell.2016.01.049.
3. Melief CJ, van Hall T, Arens R, Ossendorp F, van der Burg SH. Therapeutic cancer vaccines. J Clin Invest. 2015;125(9):3401-3412. doi:10.1172/JCI80009.
4. Oberli MA, Reichmuth AM, Dorkin JR, et al. Lipid Nanoparticle Assisted mRNA Delivery for Potent Cancer Immunotherapy. Nano Lett. 2017;17(3):1326-1335. doi:10.1021/acs.nanolett.6b03329