Differential Regulation of ZEB1 and EMT by MAPK-Interacting Protein Kinases (MNK) and eIF4E in Pancreatic Cancer

Abstract

Human pancreatic ductal adenocarcinoma (PDAC) tumors are associated with dysregulation of mRNA translation. In this report, it is demonstrated that PDAC cells grown in collagen exhibit increased activation of the MAPK-interacting protein kinases (MNKs) that mediate eIF4E phosphorylation. Pharmacologic and genetic targeting of MNKs reverse epithelial-mesenchymal transition (EMT), decrease cell migration and reduce protein expression of the EMT-regulator ZEB1 without affecting ZEB1 mRNA levels. Paradoxically, targeting eIF4E – the best-characterized effector of MNKs – increases ZEB1 mRNA expression through repression of ZEB1-targeting microRNAs miR-200c and miR-141. In contrast, targeting the MNK effector hnRNPA1, which can function as a translational repressor, increases ZEB1 protein without increasing ZEB1 mRNA levels. Importantly, treatment with MNK inhibitors blocks growth of chemoresistant PDAC cells in collagen and decreases the number of aldehyde dehydrogenase activity-positive (Aldefluor+) cells. Significantly, MNK inhibitors increase E-cadherin mRNA levels and decrease vimentin mRNA levels in human PDAC organoids without affecting ZEB1 mRNA levels. Importantly, MNK inhibitors also decrease growth of human PDAC organoids. Implications These results demonstrate differential regulation of ZEB1 and EMT by MNKs and eIF4E, and identify MNKs as potential targets in pancreatic cancer.

BET inhibitors block pancreatic stellate cell collagen I production and attenuate fibrosis in vivo

“…The stellate cell line and the primary cancer-associated PSCs were transfected with siRNA against BRD2, BRD3, BRD4, c-MYC, FOSL1, or control siRNA (20 nM) using RNAimax (Invitrogen) according to the manufacturer's instructions (20,47). qRT-PCR analysis.…”

“…Quantitative gene expression was performed with gene-specific TaqMan probes, TaqMan Universal PCR Master Mix, and the 7500 Fast Real-time PCR System from Applied Biosystems. The data were then quantified with the comparative C T method for relative gene expression (20,47).…”

“…Immunoblotting for BRD2, BRD3, BRD4, c-MYC, FOSL1, α-SMA, α-tubulin, and collagen I was done as described previously (20,47).…”

“…Collagen I mixture (2 mg/ml) was made by adding the appropriate volumes of sterile water, 10× DMEM, and NaOH, and the mixture was kept on ice until needed (20,47). Primary cancer-associated PSCs were then suspended in the collagen solution and allowed to gel at 37°C.…”

Research Article MiR-200c inhibits metastasis of breast tumor via the downregulation of Foxf2.

“…According to the subtyping guidelines by St. Gallen International Breast Cancer Congress (Goldhirsch et al, 2011), basal-like type (triple-negative breast cancer type mainly) is more invasive due to the lack of estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2 expressions and overexpression of basal-like molecular markers in breast cancer cells, making them insensitive to either molecular targeting or endocrine treatment (Goldhirsch et al, 2011). Recent studies have shown that epithelial-mesenchymal transition (EMT) plays a critical role in the invasion-metastasis cascade (Kumar et al, 2016). EMT represses cell-cell adhesion through inhibition of epithelial (E)-cadherin, zonula occludens-1, occludin, claudin-1, and claudin-7, and facilitates multiple immunosuppression, drug resistance, and evasion of apoptosis, thus promoting cancer progression and metastasis (Chaffer and Weinberg, 2011).…”