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Simple Summary: In this paper, we report on the inhibition of glioblastoma (GBM) cell growth and migration by the putative S1PR1 modulator ACT-2009905, using appropriate in vitro models. This work is based on our previously published finding that S1PR1 expression is strongly up-regulated in human glioblastoma samples and the fact that there is an association between S1PR1 with patients' survival times. We now show that pharmacological modulation by the putative S1PR1 modulator ACT-209905 inhibits GBM cell growth and migration. Furthermore, we investigated the influence of co-culture of GBM cells with THP-1 cells as a model for human monocytes, showing pro-tumoral effects and arguing for a complex interplay between GBM cells, immune cells and underlying signaling pathways. We believe that this manuscript fits the interests of the readership of the journal Cancers as it addresses the impact of alternative therapeutic options using ACT-209905 for improving GBM therapy. Glioblastoma (GBM) is still a deadly tumor due to its highly infiltrative growth behavior and its resistance to therapy. Evidence is accumulating that sphingosine-1-phosphate (S1P) acts as an important tumor-promoting molecule that is involved in the activation of the S1P receptor subtype 1 (S1PR1). Therefore, we investigated the effect of ACT-209905 (a putative S1PR1 modulator) on the growth of human (primary cells, LN-18) and murine (GL261) GBM cells. The viability and migration of GBM cells were both reduced by ACT-209905. Furthermore, co-culture with monocytic THP-1 cells or conditioned medium enhanced the viability and migration of GBM cells, suggesting that THP-1 cells secrete factors which stimulate GBM cell growth. ACT-209905 inhibited the THP-1-induced enhancement of GBM cell growth and migration. Immunoblot analyses showed that ACT-209905 reduced the activation of growth-promoting kinases (p38, AKT1 and ERK1/2), whereas THP-1 cells and conditioned medium caused an activation of these kinases. In addition, ACT-209905 diminished the surface expression of pro-migratory molecules and reduced CD62P-positive GBM cells. In contrast, THP-1 cells increased the ICAM-1 and P-Selectin content of GBM cells which was reversed by ACT-209905. In conclusion, our study suggests the role of S1PR1 signaling in the growth of GBM cells and gives a partial explanation for the pro-tumorigenic effects that macrophages might have on GBM cells. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]