Background
Retroperitoneal liposarcoma (RPLS) is a specific soft tissue sarcoma with a high recurrence rate. The short isoform of transient receptor potential cation channel subfamily M member 2 (TRPM2-S) plays an important role in the regulation of reactive oxygen species (ROS). However, the association between TRPM2-S and RPLS and its underlying mechanisms remains unclear.
Conclusion
TRPM2-S exerts Janus-faced effects in RPLS by increasing the ROS levels via inhibition on FOXO3a, which promotes cell proliferation under normoxia but induces apoptosis under oxidative stress. Video abstract.
Methods
The expression of both TRPM2-S and TRPM2-L in RPLS tissues was verified by kimmunohistochemistry (IHC). The regulation on Ca2+ influx by TRPM2-S was evaluated by Fluo-4 AM staining. The effect of TRPM2-S on cell proliferation and apoptosis was tested by 5-Ethynyl-2'-deoxyuridine (EdU) staining and Flow cytometry respectively. The level of cellular ROS was assessed by the DCFH-DA probe. Different concentrations of H2O2 were used to provide oxidative stress on RPLS cells. The underlying mechanisms were further explored by Western blotting.
Results
The IHC assays showed that TRPM2-S, but not TRPM2-L, was prognostic in RPLS. Low TRPM2-S level was associated with poor disease-free survival (DFS). Calcium influx signal intensity was significantly decreased under TRPM2-S overexpression, which resulted in a decrease in the levels of FOXO3a and PTEN. Correspondingly, the levels of pERK, pAKT, pP65, pGSK-3β, Bcl-2, and β-catenin were upregulated, and cellular ROS was gently increased under TRPM2-S overexpression. Moreover, TRPM2-S slightly promoted cell proliferation and inhibited apoptosis of RPLS cell lines under normoxia, but largely increased apoptosis rates under oxidative stress. The cleaved caspase3 was significantly upregulated by TRPM2-S overexpression under oxidative stress. N-Acetyl-L-cysteine (NAC), a small molecule antioxidant, could largely rescue RPLS cells from the apoptosis induced by H2O2.