Intratumoural Delivery of mRNA Loaded on a Cationic Hyper-Branched Cyclodextrin-Based Polymer Induced an Anti-Tumour Immunological Response in Melanoma

Simple Summary The frequency of metastatic melanoma, an extremely deadly malignancy, is rapidly increasing worldwide. Recently, messenger RNA (mRNA) injections have emerged as a promising treatment option. While mRNA therapies have demonstrated significant promise, the stability of the naked form remains a barrier, as naked mRNAs are vulnerable to common ribonucleases, and are unable to effectively penetrate plasma membranes and escape from endosomes. Thus, for this paper, we used a hyper-branched cyclodextrin-based polymer (Ppoly) as a carrier to enhance mRNA delivery for melanoma cancer. The in vitro results demonstrated that Ppoly was able to deliver the EGFP-mRNA effectively in both 2D and 3D melanoma cell lines compared to naked mRNA; in addition, Ppoly did not show any cytotoxicity. The anti-tumour effect of intratumourally injected OVA-mRNA loaded on Ppoly results showed a significant decrease in both tumour size and weight compared to other formulations by inducing an efficient adaptive immune response and OVA-specific CD8+ T cells in both spleen and tumour tissues compared to other groups. mRNA technology has demonstrated potential for use as an effective cancer immunotherapy. However, inefficient in vivo mRNA delivery and the requirements for immune co-stimulation present major hurdles to achieving anti-tumour therapeutic efficacy. Therefore, we used a cationic hyper-branched cyclodextrin-based polymer to increase mRNA delivery in both in vitro and in vivo melanoma cancer. We found that the transfection efficacy of the mRNA-EGFP-loaded Ppoly system was significantly higher than that of lipofectamine and free mRNA in both 2D and 3D melanoma cancer cells; also, this delivery system did not show cytotoxicity. In addition, the biodistribution results revealed time-dependent and significantly higher mEGFP expression in complexes with Ppoly compared to free mRNA. We then checked the anti-tumour effect of intratumourally injected free mRNA-OVA, a foreign antigen, and loaded Ppoly; the results showed a considerable decrease in both tumour size and weight in the group treated with OVA-mRNA in loaded Ppoly compared to other formulations with an efficient adaptive immune response by dramatically increasing most leukocyte subtypes and OVA-specific CD8+ T cells in both the spleen and tumour tissues. Collectively, our findings suggest that the local delivery of cationic cyclodextrin-based polymer complexes containing foreign mRNA antigens might be a good and reliable concept for cancer immunotherapy.