The role of KRAS, when activated through canonical mutations, has been well established in cancer1. Here we explore a secondary means of KRAS activation in cancer, focal high-level amplification of the KRAS gene in the absence of coding mutations. These amplifications occur most commonly in esophageal, gastric and ovarian adenocarcinomas2–4. KRAS amplified gastric cancer models possess marked overexpression of KRAS protein and are insensitive to MAPK blockade due to their capacity to adaptively respond by rapidly increasing KRAS-GTP levels. We demonstrate that inhibition of guanine exchange factors SOS1/2 or protein tyrosine phosphatase, SHP2, can attenuate this adaptive process and that targeting of these factors, both genetically and pharmacologically, can enhance sensitivity of KRAS-amplified models to MEK inhibition both in in vitro and in vivo settings. These data demonstrate the relevance of copy number amplification as a mechanism of KRAS activation, and uncover the therapeutic potential for targeting of these tumors through combined SHP2 and MEK inhibition.

BackgroundEver since the first atomic structure of an enzyme was solved, the discovery of the mechanism and dynamics of reactions catalyzed by biomolecules has been the key goal for the understanding of the molecular processes that drive life on earth. Despite a large number of successful methods for trapping reaction intermediates, the direct observation of an ongoing reaction has been possible only in rare and exceptional cases.ResultsHere, we demonstrate a general method for capturing enzyme catalysis “in action” by mix-and-inject serial crystallography (MISC). Specifically, we follow the catalytic reaction of the Mycobacterium tuberculosis β-lactamase with the third-generation antibiotic ceftriaxone by time-resolved serial femtosecond crystallography. The results reveal, in near atomic detail, antibiotic cleavage and inactivation from 30 ms to 2 s.ConclusionsMISC is a versatile and generally applicable method to investigate reactions of biological macromolecules, some of which are of immense biological significance and might be, in addition, important targets for structure-based drug design. With megahertz X-ray pulse rates expected at the Linac Coherent Light Source II and the European X-ray free-electron laser, multiple, finely spaced time delays can be collected rapidly, allowing a comprehensive description of biomolecular reactions in terms of structure and kinetics from the same set of X-ray data.Electronic supplementary materialThe online version of this article (10.1186/s12915-018-0524-5) contains supplementary material, which is available to authorized users.

Highlights d Small molecules form a covalent bond with palmitate cysteine d Covalent engagement of cysteine inhibited TEAD4,Yap1 protein-protein interaction d Inhibition of TEAD4,Yap1 in mammalian cells blocked TEAD transcriptional activity d Small-molecule inhibition of TEAD4,Yap1 inhibited glioblastoma cell viability

Previous anti-EGFR trials in unselected gastroesophageal adenocarcinoma (GEA) patients were resoundingly negative. We identified EGFR amplification in 5% (19/363) of patients at the University of Chicago, including 6% (8/140) who were prospectively screened with intention-to-treat using anti-EGFR therapy. Seven pts received >1 dose of treatment: three first line FOLFOX plus ABT-806, one second line FOLFIRI plus cetuximab, and three third/fourth line cetuximab alone. Treatment achieved objective response in 58% (4/7) and disease control in 100% (7/7) with a median progression-free survival of 10 months. Pre and post-treatment tumor NGS, serial plasma ctDNA NGS, and tumor IHC/FISH for EGFR revealed pre-existing and/or acquired genomic events including EGFR negative clones, PTEN deletion, KRAS amplification/mutation, NRAS, MYC and HER2 amplification, and GNAS mutations serving as mechanisms of resistance. Two evaluable patients demonstrated interval increase of CD3+ infiltrate, including one who demonstrated increased NKp46+, and PD-L1 IHC expression from baseline, suggesting an immune therapeutic mechanism of action. EGFR amplification predicted benefit from anti-EGFR therapy, albeit until various resistance mechanisms emerged. Statement of Significance: This paper highlights the role of EGFR inhibitorsin EGFR amplified GEA -despite negative results in prior unselected phase III trials. Using serial ctDNA and tissue NGS, we identified mechanisms of primary and acquired resistance in all patients, as well as potential contribution of antibody-dependent cell-mediated cytotoxicity (ADCC) to their clinical benefit.

An siRNA screen targeting 89 IFN stimulated genes in 14 different cancer cell lines pointed to the RIG-I (retinoic acid inducible gene I)-like receptor Laboratory of Genetics and Physiology 2 (LGP2) as playing a key role in conferring tumor cell survival following cytotoxic stress induced by ionizing radiation (IR). Studies on the role of LGP2 revealed the following: (i) Depletion of LGP2 in three cancer cell lines resulted in a significant increase in cell death following IR, (ii) ectopic expression of LGP2 in cells increased resistance to IR, and (iii) IR enhanced LGP2 expression in three cell lines tested. Studies designed to define the mechanism by which LGP2 acts point to its role in regulation of IFNβ. Specifically (i) suppression of LGP2 leads to enhanced IFNβ, (ii) cytotoxic effects following IR correlated with expression of IFNβ inasmuch as inhibition of IFNβ by neutralizing antibody conferred resistance to cell death, and (iii) mouse embryonic fibroblasts from IFN receptor 1 knockout mice are radioresistant compared with wild-type mouse embryonic fibroblasts. The role of LGP2 in cancer may be inferred from cumulative data showing elevated levels of LGP2 in cancer cells are associated with more adverse clinical outcomes. Our results indicate that cytotoxic stress exemplified by IR induces IFNβ and enhances the expression of LGP2. Enhanced expression of LGP2 suppresses the IFN stimulated genes associated with cytotoxic stress by turning off the expression of IFNβ.innate immunity | cytoplasmic sensor | interferon beta | DHX58