KRAS is the most frequently mutated driver of pancreatic, colorectal, and non-small cell lung cancers. Direct KRAS blockade has proven challenging and inhibition of a key downstream effector pathway, the RAF-MEK-ERK cascade, has shown limited success due to activation of feedback networks that keep the pathway in check. We hypothesized that inhibiting SOS1, a KRAS activator and important feedback node, represents an effective approach to treat KRAS-driven cancers. We report the discovery of a highly potent, selective and orally bioavailable small-molecule SOS1 inhibitor, BI-3406, that binds to the catalytic domain of SOS1 thereby preventing the interaction with KRAS. BI-3406 reduces formation of GTPloaded RAS and limits cellular proliferation of a broad range of KRAS-driven cancers.Importantly, BI-3406 attenuates feedback reactivation induced by MEK inhibitors and thereby enhances sensitivity of KRAS-dependent cancers to MEK inhibition. Combined SOS1 and MEK inhibition represents a novel and effective therapeutic concept to address KRAS-driven tumors.
SignificanceTo date, there are no effective targeted pan-KRAS therapies. In-depth characterization of BI-3406 activity and identification of MEK inhibitors as effective combination partners provide an attractive therapeutic concept for the majority of KRAS mutant cancers, including those fueled by the most prevalent mutant KRAS oncoproteins G12D, G12V, G12C and G13D.Research.
The natural function of cellobiose
dehydrogenase (CDH) to donate
electrons from its catalytic flavodehydrogenase (DH) domain via its
cytochrome (CYT) domain to lytic polysaccharide monooxygenase (LPMO)
is an example of a highly efficient extracellular electron transfer
chain. To investigate the function of the CYT domain movement in the
two occurring electron transfer steps, two CDHs from the ascomycete Neurospora crassa (NcCDHIIA and NcCDHIIB) and five chimeric CDH enzymes created by domain
swapping were studied in combination with the fungus’ own LPMOs
(NcLPMO9C and NcLPMO9F). Kinetic
and electrochemical methods and hydrogen/deuterium exchange mass spectrometry
were used to study the domain movement, interaction, and electron
transfer kinetics. Molecular docking provided insights into the protein–protein
interface, the orientation of domains, and binding energies. We find
that the first, interdomain electron transfer step from the catalytic
site in the DH domain to the CYT domain depends on steric and electrostatic
interface complementarity and the length of the protein linker between
both domains but not on the redox potential difference between the
FAD and heme b cofactors. After CYT reduction, a
conformational change of CDH from its closed state to an open state
allows the second, interprotein electron transfer (IPET) step from
CYT to LPMO to occur by direct interaction of the b-type heme and the type-2 copper center. Chimeric CDH enzymes favor
the open state and achieve higher IPET rates by exposing the heme b cofactor to LPMO. The IPET, which is influenced by interface
complementarity and the heme b redox potential, is
very efficient with bimolecular rates between 2.9 × 105 and 1.1 × 106 M–1 s–1.
The accurate determination of analyte concentrations with selective, fast, and robust methods is the key for process control, product analysis, environmental compliance, and medical applications. Enzyme-based biosensors meet these requirements to a high degree and can be operated with simple, cost efficient, and easy to use devices. This review focuses on enzymes capable of direct electron transfer (DET) to electrodes and also the electrode materials which can enable or enhance the DET type bioelectrocatalysis. It presents amperometric biosensors for the quantification of important medical, technical, and environmental analytes and it carves out the requirements for enzymes and electrode materials in DET-based third generation biosensors. This review critically surveys enzymes and biosensors for which DET has been reported. Single- or multi-cofactor enzymes featuring copper centers, hemes, FAD, FMN, or PQQ as prosthetic groups as well as fusion enzymes are presented. Nanomaterials, nanostructured electrodes, chemical surface modifications, and protein immobilization strategies are reviewed for their ability to support direct electrochemistry of enzymes. The combination of both biosensor elements—enzymes and electrodes—is evaluated by comparison of substrate specificity, current density, sensitivity, and the range of detection.
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