A novel dual MEK/PDK1 inhibitor 9za retards the cell cycle at G0/G1 phase and induces mitochondrial apoptosis in non-small cell lung cancer cells

BX517, an inhibitor of the mammalian phospholipid-dependent kinase 1 (PDK1), antagonizes sucrose-induced plant growth and represses the target of rapamycin (TOR) signaling and the cell cycle through WEE1 kinase in Arabidopsis thaliana

The target of rapamycin (TOR) signaling pathway is critical for plant growth and stress adaptation through maintaining the proper balance between cell proliferation and differentiation. Here, by using BX517, an inhibitor of the mammalian phosphoinositide-dependent protein kinase 1 (PDK1), we tested the hypothesis that a plant ortholog of PDK1 could influence the TOR complex activity and its target, the S6 ribosomal protein kinase (S6K) in Arabidopsis seedlings. Through locally applying sucrose to leaves, which promotes root growth and plant biomass production via TOR signaling, we could demonstrate the opposite trend upon BX517 treatment, which antagonized sucrose-induced plant growth and overly decreased root development through inhibiting the expression of mitotic cyclins CYCB1 and CYCA3 in root meristems. Evidence was gathered that the WEE1 kinase, a master regulator of the DNA damage rescue system in meristems, operates downstream of a plant BX517 target(s). TOR protein activity and WEE1 expression were analyzed through protein blots and reporter gene activity, respectively, and their relationship with meristematic cell cycle progression was tested through genetic analyses. BX517 reduced TOR kinase activity, activated WEE1 expression in shoot, root, and lateral root meristems, and inhibited meristematic cell cycle progression in roots, suggesting that PDK1 is a critical element for plant responses to mitogenic factors through modulating TOR activity. Our data uncover a relation between a PDK1 ortholog with TOR activity and the expression of WEE1 kinase for growth and stress responses in plants.

Preclinical evaluation of avutometinib and defactinib in high-grade endometrioid endometrial cancer

BACKGROUND

High-grade endometrial cancers (EAC) are aggressive tumors with a high risk of progression after treatment. As EAC may harbor mutations in the RAS/MAPK pathways, we evaluated the preclinical in vitro and in vivo efficacy of avutometinib, a RAF/MEK clamp, in combination with the focal adhesion kinase (FAK) inhibitors defactinib or VS-4718, against multiple primary EAC cell lines and xenografts.

METHODS

Whole-exome sequencing (WES) was used to evaluate the genetic landscape of five primary EAC cell lines. The in vitro activity of avutometinib and defactinib as single agents and in combination was evaluated using cell viability, cell cycle, and cytotoxicity assays. Mechanistic studies were performed using Western blot assays while in vivo experiments were completed in UTE10 engrafted mice treated with either vehicle, avutometinib, VS-4718, or their combination through oral gavage.

RESULTS

WES results demonstrated multiple EAC cell lines to harbor genetic derangements in the RAS/MAPK pathway including KRAS/PTEN/PIK3CA/BRAF/ARID1A, potentially sensitizing to FAK and RAF/MEK inhibition. Five out of five of the EAC cell lines demonstrated in vitro sensitivity to FAK and/or RAF/MEK inhibition. By Western blot assays, exposure of EAC cell lines to defactinib, avutometinib, and their combination demonstrated decreased phosphorylated FAK (p-FAK) as well as decreased p-MEK and p-ERK. In vivo the combination of avutometinib/VS-4718 demonstrated superior tumor growth inhibition compared to single-agent treatment and controls starting at Day 9 (p < 0.02 and p < 0.04) in UTE10 xenografts.

CONCLUSIONS

Avutometinib, defactinib, and to a larger extent their combinations, demonstrated promising in vitro and in vivo activity against EAC cell lines and xenografts. These preclinical data support the potential clinical evaluation of this combination in high-grade EAC patients.

A Novel PDK1/MEK Dual Inhibitor Induces Cytoprotective Autophagy via the PDK1/Akt Signaling Pathway in Non-Small Cell Lung Cancer

In a preliminary study, we synthesized a series of new PDK1/MEK dual inhibitors. Antitumor activity screening showed that Compound YZT exerts a strong inhibitory action in A549 cells. However, the specific mechanism of YZT against non-small cell lung cancer (NSCLC) is largely unknown. This work confirmed the anti-proliferation and pro-apoptosis effects of YZT in NSCLC cells. Furthermore, YZT promotes autophagy and provokes complete autophagic flux in NSCLC cells. Notably, compared with YZT alone, the combination of YZT with the autophagy inhibitor chloroquine (CQ) or 3-methyladenine (3-MA) markedly strengthened the anti-proliferative and pro-apoptotic actions, suggesting that YZT-induced autophagy is cytoprotective. We further found that YZT-induced autophagy may exert a cytoprotective function by preserving the integrity of mitochondria and decreasing mitochondrial apoptosis. Moreover, Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis suggested that PDK1 is an upstream protein of the Akt/mTOR axis and western blotting verified that YZT induces autophagy by the PDK1/Akt/mTOR signaling axis. Finally, YZT plus CQ significantly enhanced the anticancer activities compared to YZT alone in an animal study and immunohistochemistry showed that the level of LC3 was increased by YZT, which is in line with the in vitro results. In short, our study provides reliable experimental basis for developing Compound YZT as a new chemotherapeutic drug candidate and suggests that combined administration of YZT with CQ is a potential therapy against NSCLC.

The overview of Mitogen-activated extracellular signal-regulated kinase (MEK)-based dual inhibitor in the treatment of cancers

Mitogen-activated extracellular signal-regulated kinase 1 and 2 (MEK1/2) are the critical components of the mitogen-activated protein kinase/extracellular signal-regulated kinase 1 and 2 (MAPK/ERK1/2) signaling pathway which is one of the well-characterized kinase cascades regulating cell proliferation, differentiation, growth, metabolism, survival and mobility both in normal and cancer cells. The aberrant activation of MAPK/ERK1/2 pathway is a hallmark of numerous human cancers, therefore targeting the components of this pathway to inhibit its dysregulation is a promising strategy for cancer treatment. Enormous efforts have been done in the development of MEK1/2 inhibitors and encouraging advancements have been made, including four inhibitors approved for clinical use. However, due to the multifactorial property of cancer and rapidly arising drug resistance, the clinical efficacy of these MEK1/2 inhibitors as monotherapy are far from ideal. Several alternative strategies have been developed to improve the limited clinical efficacy, including the dual inhibitor which is a single drug molecule able to simultaneously inhibit two targets. In this review, we first introduced the activation and function of the MAPK/ERK1/2 components and discussed the advantages of MEK1/2-based dual inhibitors compared with the single inhibitors and combination therapy in the treatment of cancers. Then, we overviewed the MEK1/2-based dual inhibitors for the treatment of cancers and highlighted the theoretical basis of concurrent inhibition of MEK1/2 and other targets for development of these dual inhibitors. Besides, the status and results of these dual inhibitors in both preclinical and clinical studies were also the focus of this review.