Anti-cancer effects of metformin in a 3D co-culture model of pancreatic ductal adenocarcinoma.

Pancreatic ductal adenocarcinoma (PDAC) presents with condensed stroma that contributes to its high invasive capability. Although metformin adjuvant treatment has been suggested to improve the survival times of patients with PDAC, the mechanism responsible for that benefit has been investigated only in two-dimensional cell lines. We assessed the anti-cancer effect of metformin in a three-dimensional (3D) co-culture model to quantify the migration behavior of patient-derived PDAC organoids and primary pancreatic stellate cells (PSCs). At a concentration of 10 μM, metformin reduced the migratory ability of the PSCs by downregulating the expression of matrix metalloproteinase-2 (MMP2). In the 3D direct co-cultivation of PDAC organoids and PSCs, metformin attenuated the transcription of cancer stemness-related genes. The reduced stromal migratory ability of PSCs was associated with the downregulation of MMP2, and MMP2 knockdown in PSCs reproduced their attenuated migratory ability. The anti-migration effect of a clinically relevant concentration of metformin was demonstrable in a 3D indirect co-culture model of PDAC consisting of patient-derived PDAC organoids and primary human PSCs. The metformin suppressed PSC migration via MMP2 downregulation and attenuated cancer stemness factors. Furthermore, oral administration of metformin (30 mg/kg) strikingly suppressed the growth of PDAC organoids xenograft in immunosuppressed mice. These results indicate metformin could offer the potential approach as an effective therapeutic drug for PDAC.