(A) In vivo primary human colorectal xenograft model HCOX4087 treated with trametinib (0.3 mg/kg QD), SHP099 (100 mg/kg QD), and a pan-RTK inhibitor, Dovitinib (100 mg/kg QD). (B-C) In vivo efficacy of selective VEGFR2 inhibitor, BFH772 (3 mg/kg QD) in MIA PaCA-2 and T3M-4 cells implanted subcutaneously. Data plotted are tumor volume means {plus minus} s.e.m (T3M-4, n=8. MIA PaCA-2, n=7) (D) Evaluation of SHP099 in firefly- luciferase labeled MIA PaCa-2 pancreatic cells implanted surgically into the mouse pancreas. Data plotted are mean bioluminescent signal (BLI) {plus minus} s.e.m (n=6). (E-F) Immunoblot of SHP2 and soft agar assay with MIA Paca-2 cells with Dox-inducible shRNA targeting SHP2 or control non-targeting shRNA after Dox treatment. (G) In vivo SHP2 expression levels evaluated by Western blot and levels of MAPK pathway suppression by DUSP6, 3 hours after the last dose of SHP099 from MIA PaCa-2 tumors in Fig. 4F (n=3).
ARTICLE ABSTRACT
KRAS, an oncogene mutated in nearly one third of human cancers, remains a pharmacologic challenge for direct inhibition except for recent advances in selective inhibitors targeting the G12C variant. Here, we report that selective inhibition of the protein tyrosine phosphatase, SHP2, can impair the proliferation of KRAS-mutant cancer cells in vitro and in vivo using cell line xenografts and primary human tumors. In vitro, sensitivity of KRAS-mutant cells toward the allosteric SHP2 inhibitor, SHP099, is not apparent when cells are grown on plastic in 2D monolayer, but is revealed when cells are grown as 3D multicellular spheroids. This antitumor activity is also observed in vivo in mouse models. Interrogation of the MAPK pathway in SHP099-treated KRAS-mutant cancer models demonstrated similar modulation of p-ERK and DUSP6 transcripts in 2D, 3D, and in vivo, suggesting a MAPK pathway–dependent mechanism and possible non-MAPK pathway–dependent mechanisms in tumor cells or tumor microenvironment for the in vivo efficacy. For the KRASG12C MIAPaCa-2 model, we demonstrate that the efficacy is cancer cell intrinsic as there is minimal antiangiogenic activity by SHP099, and the effects of SHP099 is recapitulated by genetic depletion of SHP2 in cancer cells. Furthermore, we demonstrate that SHP099 efficacy in KRAS-mutant models can be recapitulated with RTK inhibitors, suggesting RTK activity is responsible for the SHP2 activation. Taken together, these data reveal that many KRAS-mutant cancers depend on upstream signaling from RTK and SHP2, and provide a new therapeutic framework for treating KRAS-mutant cancers with SHP2 inhibitors.
