Additional file 4. Figure S3. LC-MS/MS detected cytoplasmic 5-HT in colon cancer cells. Cytoplasmic 5-HT is observable in colon cancer cells following 5-HT stimulation. Subsequently, LC–MS/MS identified a prominent dissociative peak at 1.49 min in both SW480 and SW1116 cell lysates after 10 μM 5-HT stimulation, similar to the standard