(A) Immunoblot of p-RSK3 and qPCR for DUSP6 from MIA PaCa-2 xenografts collected 3 hours after the last dose from Fig 5C. (B) Immunoblot for the designated proteins from MIA PaCa-2 cells grown in 2D, 3D and from in vivo xenografts without compound treatment. Protein loading amount was normalized and verified by tubulin loading control. Each separate column represents an individual treated tumor. (C) Dependency of MET by DRIVE pooled shRNA screen (y axis, ATARIS Quantile score of less than -0.5 indicates a significant effect) and expression of HGF (x-axis) by RNAseq in pancreatic cancer cell lines in CCLE (n=21). (D) Immunoblot of p-RSK3 and qPCR for DUSP6 from KP4 xenografts collected 3 hours after the last dose from Fig 5E. Protein loading amount was normalized and verified by tubulin loading control. Each separate column represents an individual treated tumor (E) Immunoblot for the designated proteins from KP4 cells grown in 2D, 3D and from in vivo xenografts without compound treatment (F) Schematic of RTK-SHP2 signaling highlighting that SHP2 acts downstream of one or more activated RTKs to elicit downstream signaling in KRAS mutant and also additional SHP2-specific, non-MAPK signaling. SHP2 inhibition by SHP099 can serve as a surrogate for cancers where KRAS mutant cancers are dependent on upstream RTKs.
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.
