Glycogen synthase kinase-3β inhibition depletes the population of prostate cancer stem/progenitor-like cells and attenuates metastatic growth

Abstract

Cancer cells with stem or progenitor properties play a pivotal role in the initiation, recurrence and metastatic potential of solid tumors, including those of the human prostate. Cancer stem cells are generally more resistant to conventional therapies thus requiring the characterization of key pathways involved in the formation and/or maintenance of this malignant cellular subpopulation.To this end, we identified Glycogen Synthase Kinase-3β (GSK-3β) as a crucial kinase for the maintenance of prostate cancer stem/progenitor-like cells and pharmacologic inhibition of GSK-3β dramatically decreased the size of this cellular subpopulation. This was paralleled by impaired clonogenicity, decreased migratory potential and dramatic morphological changes. In line with our in vitro observations, treatment with a GSK-3β inhibitor leads to a complete loss of tumorigenicity and a decrease in metastatic potential in preclinical in vivo models. These observed anti-tumor effects appear to be largely Wnt-independent as simultaneous Wnt inhibition does not reverse the observed antitumor effects of GSK-3β blockage. We found that GSK-3β activity is linked to cytoskeletal protein F-actin and inhibition of GSK-3β leads to disturbance of F-actin polymerization. This may underlie the dramatic effects of GSK-3β inhibition on prostate cancer migration. Furthermore, GSK-3β inhibition led to strongly decreased expression of several integrin types including the cancer stem cell-associated α2β1 integrin. Taken together, our mechanistic observations highlight the importance of GSK-3β activity in prostate cancer stemness and may facilitate the development of novel therapy for advanced prostate cancer.

Deficiency of Functional Iron-Sulfur Domains in ABCE1 Inhibits the Proliferation and Migration of Lung Adenocarcinomas By Regulating the Biogenesis of Beta-Actin In Vitro

“…Furthermore, the average fluorescent densities of these cells verified the morphological observations in accordance with previous studies by Visegrady et al [34]. Other authors found that reduced integrin-mediated adhesion was attributed to the disturbance of F-actin (formed by β-actin) and was responsible for prostate cancer stemness and bone metastasis [32]. …”

“…In gene function studies, the specific knockdown or upregulation of target genes without affecting other gene products is an important method for developing specific mutants for use in lentiviral packaging vectors [30-32]. In view of the vital function of ABCE1 in protein synthesis, translation termination and ribosome recycling, knockdown of ABCE1 may interfere with basic cellular metabolism.…”

“…Additionally, we found that the Fe-S cluster domains could affect cell shape and migratory behavior. Previous studies have indicated that cell migration is dependent on lamellipodia formation [32, 33]. Changes in cell polarity and actin organization may reflect alterations in cell migration.…”

A screen for transcription factor targets of Glycogen Synthase Kinase-3 highlights an inverse correlation of NFκB and Androgen Receptor Signaling in Prostate Cancer

“…One possibility is that stable inhibition of GSK-3 isoforms leads to selection for different cell subsets or types, or changes the proportions of precursor cells in the population. Consistent with this possibility, small molecule inhibition of GSK-3 was recently reported to deplete the population of prostate cancer stem/progenitor-like cells in PC3 and PC3M cells, as measured by the proportion of ALDH HIGH cells and reduced expression of stem/progenitor markers including NANOG and OCT4 [28]. However, this was not observed in LNCaP C4-2 and DU145 cells.…”

“…Several other spots were reproducibly altered with stable GSK-3α silencing, namely an increase in binding to the Sp1 binding site (row 11 columns 1/2), the Stat5/6 binding site (columns 13/14) and the Pbx1 binding site (row 7 columns 15/16), also observed upon acute silencing of GSK-3α. To address the possibility that stable inhibition of GSK-3 leads to selection for prostate cancer stem/progenitor-like cells, as was recently reported for PC3 cells [28], we measured the expression levels of three genes expressed in 22Rv1-derived stem/progenitor cells, SOX2, NANOG and BCRP [29], in the 22Rv1-derived cell clones. This revealed small reductions in expression of SOX2 in both GSK- 3-isoform silenced cell lines, a small increase in NANOG expression in the GSK-3α-silenced cell line and no change in expression of BCRP (Figure 1E).…”