Antitumor activity of pimasertib, a selective MEK 1/2 inhibitor, in combination with PI3K/mTOR inhibitors or with multi‐targeted kinase inhibitors in pimasertib‐resistant human lung and colorectal cancer cells

Abstract

The RAS/RAF/MEK/MAPK and the PTEN/PI3K/AKT/mTOR pathways are key regulators of proliferation and survival in human cancer cells. Selective inhibitors of different transducer molecules in these pathways have been developed as molecular targeted anti-cancer therapies. The in vitro and in vivo anti-tumor activity of pimasertib, a selective MEK 1/2 inhibitor, alone or in combination with a PI3K inhibitor (PI3Ki), a mTOR inhibitor (everolimus), or with multi-targeted kinase inhibitors (sorafenib and regorafenib), that block also BRAF and CRAF, were tested in a panel of eight human lung and colon cancer cell lines. Following pimasertib treatment, cancer cell lines were classified as pimasertib-sensitive (IC 50 for cell growth inhibition of 0.001 mM) or pimasertib-resistant. Evaluation of basal gene expression profiles by microarrays identified several genes that were up-regulated in pimasertib-resistant cancer cells and that were involved in both RAS/RAF/MEK/MAPK and PTEN/PI3K/ AKT/mTOR pathways. Therefore, a series of combination experiments with pimasertib and either PI3Ki, everolimus, sorafenib or regorafenib were conducted, demonstrating a synergistic effect in cell growth inhibition and induction of apoptosis with sustained blockade in MAPK-and AKT-dependent signaling pathways in pimasertib-resistant human colon carcinoma (HCT15) and lung adenocarcinoma (H1975) cells. Finally, in nude mice bearing established HCT15 and H1975 subcutaneous tumor xenografts, the combined treatment with pimasertib and BEZ235 (a dual PI3K/mTOR inhibitor) or with sorafenib caused significant tumor growth delays and increase in mice survival as compared to single agent treatment. These results suggest that dual blockade of MAPK and PI3K pathways could overcome intrinsic resistance to MEK inhibition.The RAS/RAF/MEK/MAPK and PTEN/PI3K/AKT/mTOR signaling pathways play central roles in the intracellular transduction of proliferative signals from activated cell membrane growth factor receptors to the nucleus in both normal and cancer cells. RAF is a serine/threonine kinase that activates down-stream signals in response to activated GTP-bound RAS by phosphorylating MEK1 and MEK2, which in turn phosphorylate and activate MAPK (or ERK1 and ERK2). ERK kinases phosphorylate a number of cellular substrates with key roles in cell proliferation and survival. The phosphoinositide 3-kinases (PI3Ks) are a family of lipid kinases that propagate intracellular signaling cascades regulating a wide range of cellular processes. PI3K phosphorylates the 3 0 -OH group on phosphatidylinositols in the plasma membrane. This leads to recruitment of AKT, a serine/ threonine kinase, to the cell membrane where it becomes

Primary and Acquired Resistance of Colorectal Cancer Cells to Anti-EGFR Antibodies Converge on MEK/ERK Pathway Activation and Can Be Overcome by Combined MEK/EGFR Inhibition

“…Protein lysates containing comparable amounts of proteins, estimated by a modified Bradford assay (BioRad), were subjected to Western blot analysis, as previously described (24). Immuno-complexes were detected with the Enhanced Chemiluminescence Kit (Pierce Biotechnology Inc.).…”

“…The day before transfection, the cells were plated in 35 mm dishes at 40% of confluence in medium supplemented with 5% FBS without antibiotics. Cells were harvested at different time points (24,48,72, and 96 hours) after transfection. Western blot analysis for MEK1/2 expression was done.…”

“…S1A and S1B and Table S3). To confirm the synergistic growth inhibitory effects of cetuximab in combination with BAY 86-9766, we have used other 2 selective MEK1/2 inhibitors, such as selumetinib and pimasertib (24,28). As depicted in Supplementary Table S1B, the combined treatment of cetuximab with selumetinib or pimasertib induced a clearly synergistic antitumor activity only in the colorectal cancer cell lines with either primary or acquired resistance to the anti-EGFR inhibitor.…”

3,6-Dihydroxyflavone Suppresses Breast Carcinogenesis by Epigenetically Regulating miR-34a and miR-21

“…The PI3K/Akt/mTOR signaling pathway is critical to normal cellular physical progress and also commonly overactivated in cancer progression, especially in breast carcinogenesis and metastasis (5,6). In fact, this signaling pathway acts as a key integration point between the extrinsic and intrinsic cellular environments (7,8); it regulates a broad spectrum of cellular processes and consequently plays an important role in breast tumorigenesis and development (9,10).…”

Targeting the PD-1 Pathway in MSI-Stable Metastatic Colorectal Cancer

“…Dual blockade of MEK and PI3K pathways could overcome resistance to MEK inhibition [25]. Triple therapy that includes MEKi, PD-1 pathway inhibition and PI3K inhibitor could be explored in MSI-S patients.…”