SLC22A3/OCT3 drives serotonin-mediated stemness in pancreatic cancer.

Pancreatic cancer (PC) is a highly aggressive malignancy, with cancer stem cells (CSCs) playing a critical role in metastasis, therapy resistance, and recurrence, thereby presenting significant treatment challenges. Emerging evidence suggests that normal embryonic and adult progenitor stem cells share common gene signatures with CSCs. However, the early pluripotency-associated factors and stemness programs that become aberrantly reactivated during oncogenic transformation remain poorly defined. Here, we identify SLC22A3/OCT3 (Solute Carrier Family 22 Member 3) as a reactivated embryonic-associated signature that regulates PC stemness. SLC22A3 is markedly upregulated in CSC-enriched populations, and its silencing in PC cells grown in both 2D cultures and 3D organoid models significantly reduces key stemness features. Moreover, serotonin (5-HT) transport, mediated by SLC22A3, enhances overall stemness via downstream histone modifications, linking serotonin signaling to CSC regulation. Collectively, these findings establish SLC22A3 as a regulator of serotonin-driven stemness and a potential therapeutic target in PC.