Does metformin enhance anti-tumor effect of L-type amino acid transporter 1 ( LAT1 ) inhibitor?
By MTT assay, 0.5 mM metformin inhibited proliferation of Ca9-22 cells to 70% of control. In the presence of 100 μM JPH203, proliferation of Ca9-22 cells was inhibited to 60% of control. By combining these 2 drugs, proliferation of Ca9-22 was significantly inhibited to 40% of control. However, this regimen was not very effective against HEp-2 cells. This combination also suppressed in vivo growth of Ca9-22 cells in a xenotransplant model. A combination of anti-LAT1 drug with metformin may be an effective anti-proliferative therapy for certain subsets of cancers.
The presented study demonstrates that IL-12 and IL-18, or even more a combined application of both cytokines, induce IDO expression besides the known pathway via IFN-gamma. These mechanisms have been shown herein for the first time in human osteosacoma cell lines. Since IDO expression could still be shown after complete blocking of IFN-gamma, we conclude that at least a second pathway is responsible for inducing IDO activity. This is in contrast to the present knowledge about IDO activation.