Identification and Characterization of a Novel Chemotype MEK Inhibitor Able to Alter the Phosphorylation State of MEK1/2

Abstract

A small molecule compound, JTP-74057/GSK1120212/trametinib, had been discovered as a very potent antiproliferative agent able to induce the accumulation of CDK inhibitor p15INK4b. To conduct its drug development rationally as an anticancer agent, molecular targets of this compound were identified as MEK1/2 using compound-affinity chromatography. It was shown that JTP-74057 directly bound to MEK1 and MEK2 and allosterically inhibited their kinase activities, and that its inhibitory characteristics were similar to those of the known and different chemotype of MEK inhibitors PD0325901 and U0126. It was further shown that JTP-74057 induced rapid and sustained dephosphorylation of phosphorylated MEK in HT-29 colon and other cancer cell lines, while this decrease in phosphorylated MEK was not observed in PD0325901-treated cancer cells. Physicochemical analyses revealed that JTP-74057 preferentially binds to unphosphorylated MEK (u-MEK) in unique characteristics of both high affinity based on extremely low dissociation rates and ability stabilizing u-MEK with high thermal shift, which were markedly different from PD0325901. These findings indicate that JTP-74057 is a novel MEK inhibitor able to sustain MEK to be an unphosphorylated form resulting in pronounced suppression of the downstream signaling pathways involved in cellular proliferation.

Coadministration of Trametinib and Palbociclib Radiosensitizes KRAS-Mutant Non–Small Cell Lung Cancers In Vitro and In Vivo

“…Ã , P < 0.05, ÃÃ , P < 0.01, ÃÃÃ , P < 0.001, compared with vehicle. mutant tumor cells (41). Mutations in KRAS lead to constitutive activation of the RAS pathway, which allows for downstream effectors of ERK1/2 (e.g., cyclin D1, cyclin D1-CDK4 complex) to also be upregulated (42).…”

Network Architecture Predisposes an Enzyme to Either Pharmacologic or Genetic Targeting

“…Transduction and selection of NIH 3T3 cells expressing the first shMEK hairpin yielded knockdown of 80% compared with control cells (Figure 3A). Given this level of MEK perturbation, our goal was to determine whether ERK –| Raf feedback influenced the potency of shMEK relative to the selective and established MEK inhibitor U0126 (Davies et al, 2000; Favata et al, 1998), whose mechanism of action is similar to MEK-targeted drugs used clinically (Yoshida et al, 2012). …”

Dual-targeting of MEK and CDK4/6 in KRAS-mutated Non-Small Cell Lung Cancer

“…As shown in Figure 1, MEK1/2 kinases play an integral role in the RAS-RAF-MEK-ERK pathway involved in cellular growth and proliferation [18] . Mutated KRAS constitutively activates downstream effectors such as cyclin D1 and ERK1/2 [19] .…”