The small-molecule drug NT157 has demonstrated promising efficacy in preclinical models of a number of different
cancer types, reflecting activity against both
cancer cells and the tumor microenvironment. Two known mechanisms of action are degradation of
insulin receptor substrates (IRS)-1/2 and reduced Stat3 activation, although it is possible that others exist. To interrogate the effects of this drug on cell signaling pathways in an unbiased manner, we have undertaken mass spectrometry-based global
tyrosine phosphorylation profiling of NT157-treated A375
melanoma cells. Bioinformatic analysis of the resulting dataset resolved 5 different clusters of
tyrosine-phosphorylated
peptides that differed in the directionality and timing of response to drug treatment over time. The
receptor tyrosine kinase AXL exhibited a rapid decrease in phosphorylation in response to drug treatment, followed by
proteasome-dependent degradation, identifying an additional potential target for NT157 action. However, NT157 treatment also resulted in increased activation of
p38 MAPK α and γ, as well as the JNKs and specific
Src family kinases. Importantly, cotreatment with the
p38 MAPK inhibitor
SB203580 attenuated the antiproliferative effect of NT157, while synergistic inhibition of cell proliferation was observed when NT157 was combined with a Src inhibitor. These findings provide novel insights into NT157 action on
cancer cells and highlight how globally profiling the impact of a specific drug on cellular signaling networks can identify effective combination treatments. Mol
Cancer Ther; 17(5); 931-42. ©2018 AACR.