Fig. 2

TM induces apoptosis independently of serotonin signaling (a) Expression of the different serotonin receptors (5-HTRs) in our panel of human melanoma cell lines. Data was mined from the Cancer Cell Line Encyclopedia. b, upper panel mRNA expression of 5-HTR4 which is targeted by TM is shown. Expression values are represented as Log10 (CTHTR4- CTGAPDH) and visualized through Morpheus software (Broad Institute) (n = 3–5). b, lower panel Protein expression of HTR4 in melanoma cell lines is shown using mouse brain as a positive control (A representative immunoblot of n = 3 is shown). c, upper panel Changes in phosphorylation of the transcription factor CREB 8 and 18 h post TM treatment are shown (A representative immunoblot of n = 3–5 is shown). Quantification of immunoblots is shown in C (lower panel). d Treatment with serotonin (5-HT) for 72 h did not have anti-proliferative effects in melanoma cells (n = 3–4). e Co-treatment of TM (3 μM for B16F10 and A375 and 5 μM for RPMI, SH4, MeWo and MelJuso melanoma cells) with serotonin (5-HT, 100 μM) did not impact the anti-melanoma effects of TM and did not alter TM induced apoptosis as assessed 72 h post treatment using the Annexin V/7AAD assay (n = 3–6). Error bars in the all experiments indicate SEM; *P < 0.05 as determined by a Student’s t-test (unpaired, 2 tailed), or a one-way ANOVA with a Dunnett’s post-hoc test