Methionine restriction inhibits pancreatic cancer proliferation while suppressing JAK2/STAT3 pathway.

[BACKGROUND] Methionine restriction (MR) has been demonstrated to exhibit anti-tumor effects in various types of cancer, including pancreatic cancer (PC). However, the detailed mechanism induced by MR remains still unclear. This study aims to reveal the underlying mechanism of MR on PC by proteomic analysis.

[MATERIAL & METHODS] Human PC cell lines were cultured in both standard and MR media to evaluate the effect of MR. The differences in protein expression were evaluated through proteomic analysis. Ingenuity Pathway Analysis (IPA) was performed to identify proteins potentially associated with tumor growth in vitro. The proteins associated with the anti-tumor effect were validated using western blotting, real-time PCR, and ELISA. An experimental model involving subcutaneous PC mice was established for the assessment of the effectiveness of the MR diet and the expression of target proteins through immunohistochemical staining.

[RESULTS] Cell proliferation was suppressed in the MR media compared to the standard media. IPA analysis showed that STAT3 was decreased in the Apoptotic Pathway of Pancreatic Cancer Cell lines in the MR group. Western blotting showed MR decreased STAT3 expression. Real-time PCR showed that MR decreased JAK2 and STAT3 mRNA expression in Panc-1 and Mia-PaCa 2, but not in Capan-1. ELISA revealed that NF-kB expression was decreased in the MR group. In the in vivo study, the final estimated tumor volume in the MR group was significantly lower than the control group (p < 0.01). Immunostaining of resected specimens showed that STAT3 expression was suppressed in the MR group.

[CONCLUSION] MR suppressed the JAK2/STAT3 pathway and decreased NF-kB in some PC cell lines.