Epithelial-to-Mesenchymal Transition and Oncogenic Ras Expression in Resistance to the Protein Kinase Cβ Inhibitor Enzastaurin in Colon Cancer Cells

Abstract

Identifying molecular factors of sensitivity and resistance of cancer cells to enzastaurin, a drug inhibiting protein kinase C (PKC) β, remains a major challenge to improve its clinical development. Investigating the cellular effects of enzastaurin in a panel of 20 human cancer cell lines, we found that most cells displaying oncogenic K-Ras mutations also display resistance to enzastaurin. Wild-type (WT) K-Ras cancer cells displaying high sensitivity to enzastaurin also expressed high mRNA levels of epithelial markers, such as E-cadherin (CDH1), and low mRNA expressions of mesenchymal markers, such as vimentin, N-cadherin (CDH2), and other genes frequently expressed in mesenchymal transition such as ZEB1, TWIST, SLUG, SNAIL, and TGFβ. WT K-Ras enzastaurin-resistant cells also expressed high levels of mesenchymal markers. Based on this observation, the effects of enzastaurin were investigated in epithelial colon COLO205-S cells that expressed WT Ras/Raf and its derived COLO205-R mesenchymal counterpart selected for resistance to most PKC modulators and displaying oncogenic K-Ras (G13D/exon 2). In COLO205-S cells, inhibition of phosphorylated PKCβ led to the inactivation of AKT and glycogen synthase kinase 3β and was associated with apoptosis without significant effect on cell cycle progression. In COLO205-R cells, enzastaurin induced mainly necrosis at high concentrations. In COLO205-R cells, a strong activation of extracellular signal-regulated kinase 1/2 possibly due to oncogenic K-Ras was predominantly associated with transcription of potent antiapoptotic genes, such as BCL2, GADD45B, and CDKN1A, as well as the multidrug resistance gene ABCB1. From this study, colon cancer cells undergoing apoptosis under enzastaurin exposure seem to frequently express a WT Ras and an epithelial phenotype. Mol Cancer Ther; 9(5); 1308-17. ©2010 AACR.

Consumption of high-fat diet induces tumor progression and epithelial–mesenchymal transition of colorectal cancer in a mouse xenograft model

“…EMT provides cells the ability to migrate and invade, and reflects the plasticity of epithelial cells [28]. While epithelial cells undergo EMT, they acquire a mesenchymal phenotype, including decreased cell-cell adherent junctions and increased motility and chemotherapeutic resistance [28].…”

“…EMT provides cells the ability to migrate and invade, and reflects the plasticity of epithelial cells [28]. While epithelial cells undergo EMT, they acquire a mesenchymal phenotype, including decreased cell-cell adherent junctions and increased motility and chemotherapeutic resistance [28]. It has been reported that EMT is involved in the progression of carcinomas of different sites including colon, head and neck, pancreas, liver, esophagus and lung [29][30][31][32][33][34][35][36][37].…”

Polycationic calixarene PTX013, a potent cytotoxic agent against tumors and drug resistant cancer

“…The Colo205-R cell line was derived from Colo205 cells with an acquired resistance to protein kinase C modulators like Enzastaurin (LY317615-HCI, Eli Lilly) [16, 21]. SQ20B-R cells were derived from inherent radio-resistant SQ20B head & neck squamous cancer cells with acquired resistance to PTX008 that developed after about 6 months of treatment.…”

Colon cancer subtypes: concordance, effect on survival and selection of the most representative preclinical models

“…Likewise, high expression of FAP has also been described to lead to poor patient prognosis17. Oncogenic K-RAS was associated with transcription of the antiapoptotic GADD45B18. However, no direct correlation between survival and GADD45B expression in colon cancer has been described earlier.…”