Fig. 6

5-Nonyloxytryptamine (5-NL) can be successfully combined with immunotherapy in vivo. Transcriptomic data from melanoma samples of therapy naïve patients was mined from the Cancer Immunome Atlas. A Responders to checkpoint inhibitors (anti-PD1 and anti-CTL4) expressed higher mRNA levels of B2M. B Expression of CREB1 positively correlated with HLA A-C and B2M. C C57BL/6 J mice were subcutaneously injected with 5 × 10⁵ B16.GP33 cells. 7 days post-tumor injection mice were randomized and treated daily with 6.25 mg/kg of 5-NL or with vehicle for five consecutive days. Additionally, mice were intravenously injected with murine anti-PD1 antibody or isotype control on days -1, 1, 3, 5 and 7 pre and post tumor inoculation. Tumor volume was measured (n = 5–9). Data is pooled from two independent in vivo experiments. D Combination index (CI) was calculated from dose response curves of human melanoma cell lines treated with 5-NL, Vemurafenib or in a combination in ratio 1:1. CI < 1 indicates synergy, CI = 1 indicates additivity, and CI > 1 indicates antagonism. The EC50 (50% effective concentration) and EC75 (75% effective concentration) are shown (n = 3). Error bars indicate SEM; *P < 0.05 as determined by a Student´s t-test (unpaired, 2 tailed) or a two-way ANOVA with a Tukey’s post-hoc test. E A schematic diagram summarizing 5-NL’s anti-tumoral and pro-immune effects is shown. The diagram created with BioRender.com