miR27a, a fine-tuning molecule, interacts with growth hormone (GH) signaling and ornithine decarboxylase (ODC) via targeting STAT5.

Autocrine growth hormone (GH) expression triggers cell proliferation, invasion-metastasis in vitro and in vivo models, but GH gene mutations inhibit postnatal growth. Natural polyamines (PA); putrescine, spermidine, spermine trigger cell growth and differentiation. The importance of miR27a has shown to exert a suppressive effect on ornithine decarboxylase (ODC) expression in dwarf mice models. We aimed to modulate the role of A13S, F166Δ, T24 GH gene mutations' impact on PA metabolism and epithelial-mesencyhmal transition (EMT) pathway through miR27a. Biologically active GH signaling triggered cell viability, growth, and colony formation, but T24A alteration significantly decreases aggressive profiles due to inactive GH signaling through a decline in STAT5 activity and expressions of STAT5, c-myc and ODC. Although statistically significant increase in intracellular PA levels in wt GH signaling HEK293 cells compared to HEK293 cells with a lack of GH signaling, a sharp decline in PA levels measured in each mutant GH expressing HEK293 cells. When we inhibited miR27a, proliferation and colony formation accelerated through a significant increase in putrescine levels and upregulation of ODC, STAT5 expression. In contrast, a substantial decline in GH-mediated colony enlargement observed via ODC, STAT5 downregulation, and PA depletion in both wt and mutant GH expressing HEK293 cell lines by miR27a mimic transfection. In conclusion, T24A mutant GH expression declines the GH signaling through STAT5 activity, and mutant GH signaling decreased cell proliferation, division, and colony formation via EMT inhibition. The autocrine GH-mediated proliferative profiles were under the control of miR27a that depletes intracellular putrescine levels via targeting ODC.

Palbociclib negatively regulates fatty acid synthesis due to upregulation of AMPKα and miR-33a levels to increase apoptosis in Panc-1 and MiaPaCa-2 cells.

Fatty acids (FAs) synthesis mechanism has various regulators such as fatty acid synthase (FASN), AMP-regulated protein kinase (AMPK), or mammalian target of rapamycin (mTOR), which are aberrantly dysregulated in various pancreatic cancer cells. In this study, we aim to understand the regulatory role of palbociclib, a CDK4/6 inhibitor, on the cellular energy metabolism through regulation of AMPK/mTOR signaling by modulation of intracellular miR-33a levels in Panc-1 and MiaPaCa-2 cells. Palbociclib downregulated FAs metabolism more effectively in MiaPaCa-2 cells than Panc-1 cells. Moreover, palbociclib treatment increased the levels of miR-33a in each cell line albeit a higher increase was evident in MiaPaCa-2 cells. Stress-mediated activation of mTOR signaling axis was found associated with palbociclib-mediated AMPKα activation and miR33a upregulation. These findings provided that a deeper understanding about possible interactions of cell cycle activity and reduction of FAs synthesis may facilitate the enhancement of cell death mechanisms in pancreatic cancer cells.

Palbociclib, a selective CDK4/6 inhibitor, restricts cell survival and epithelial-mesenchymal transition in Panc-1 and MiaPaCa-2 pancreatic cancer cells.

The mortality rate of pancreatic cancer has close parallels to its incidence rate because of limited therapeutics and lack of effective prognosis. Despite various novel chemotherapeutics combinations, the 5-year survival rate is still under 5%. In the current study, we aimed to modulate the aberrantly activated PI3K/AKT pathway and epithelial-mesenchymal transition (EMT) signaling with the treatment of CDK4/6 inhibitor PD-0332991 (palbociclib) in Panc-1 and MiaPaCa-2 pancreatic cancer cells. It was found that PD-0332991 effectively reduced cell viability and proliferation dose-dependently within 24 hours. In addition, PD-0332991 induced cell cycle arrest at the G1 phase by downregulation of aberrant expression of CDK4/6 through the dephosphorylation of Rb in each cell lines. Although PD-0332991 treatment increased epithelial markers and decreased mesenchymal markers, the nuclear translocation of ß-catenin was not prevented by PD-0332991 treatment, especially in MiaPaCa-2 cells. Effects of PD-0332991 on the regulation of PI3K/AKT signaling and its downstream targets such as GSK-3 were cell type-dependent. Although the activity of AKT was inhibited in both cell lines, the phosphorylation of GSK-3ß at Ser9 increased only in Panc-1. In conclusion, PD-0332991 induced cell cycle arrest and reduced the cell viability of Panc-1 and MiaPaCa-2 cells. However, PD-0332991 differentially affects the regulation of the PI3K/AKT pathway and EMT process in cells due to its distinct influence on Rb and GSK-3/ß-catenin signaling. Understanding the effect of PD-0332991 on the aberrantly activated signaling axis may put forward a new therapeutic strategy to reduce the cell viability and metastatic process of pancreatic cancer.

Inhibition of autophagy enhances DENSpm-induced apoptosis in human colon cancer cells in a p53 independent manner.

PURPOSE: One of the recently developed polyamine (PA) analogues, N 1 ,N11-diethylnorspermine (DENSpm), has been found to act as an apoptotic inducer in melanoma, breast, prostate and colon cancer cells. Also, its potential to induce autophagy has been established. Unfolded protein responses and starvation of amino acids are known to trigger autophagy. As yet, however, the molecular mechanism underlying PA deficiency-induced autophagy is not fully clarified. Here, we aimed to determine the apoptotic effect of DENSpm after autophagy inhibition by 3-methyladenine (3-MA) or siRNA-mediated Beclin-1 silencing in colon cancer cells. METHODS: The apoptotic effects of DENSpm after 3-MA treatment or Beclin-1 silencing were determined by PI and AnnexinV/PI staining in conjunction with flow cytometry. Intracellular PA levels were measured by HPLC, whereas autophagy and the expression profiles of PA key players were determined in HCT116, SW480 and HT29 colon cancer cells by Western blotting. RESULTS: We found that DENSpm-induced autophagy was inhibited by 3-MA treatment and Beclin-1 silencing, and that apoptotic cell death was increased by PA depletion and spermidine/spermine N1-acetyltransferase (SSAT) upregulation. We also found that autophagy inhibition led to DENSpm-induced apoptosis through Atg5 down-regulation, p62 degradation and LC3 lipidation in both HCT116 and SW480 cells. p53 deficiency did not alter the response of the colon cancer cells to DENSpm-induced apoptotic cell death under autophagy suppression conditions. CONCLUSIONS: From our results we conclude that DENSpm-induced apoptotic cell death is increased when autophagy is inhibited by 3-MA or Beclin-1 siRNA through PA depletion and PA catabolic activation in colon cancer cells, regardless p53 mutation status.