Induced growth inhibition, cell cycle arrest and apoptosis in CD133+/CD44+ prostate cancer stem cells by flavopiridol

Abstract

Flavopiridol is a flavone that inhibits several cyclin-dependent kinases and exhibits potent growth-inhibitory activity, apoptosis and G1-phase arrest in a number of human tumor cell lines. Flavopiridol is currently undergoing investigation in human clinical trials. The present study focused on the effect of flavopiridol in cell proliferation, cell cycle progression and apoptosis in prostate cancer stem cells (CSCs). Therefore, cluster of differentiation 133 (CD133)+high/CD44+high prostate CSCs were isolated from the DU145 human prostate cancer cell line. The cells were treated with flavopiridol in a dose- and time-dependent manner to determine the inhibitory effect. Cell viability and proliferation were analyzed and the efficiency of flavopiridol was assessed using the sphere-forming assay. Flavopiridol was applied to monolayer cultures of CD133high/CD44high human prostate CSCs at the following final concentrations: 100, 300, 500 and 1000 nM. The cultures were incubated for 24, 48 and 72 h. The half maximal inhibitory concentration (IC50) value of the drug was determined as 500 nM for monolayer cells. Dead cells were analyzed prior and subsequent to exposure to increasing flavopiridol doses. Annexin-V and immunofluorescence analyses were performed for the evaluation of apoptotic pathways. According to the results, flavopiridol treatment caused significant growth inhibition at 500 and 1000 nM when compared to the control at 24 h. G0/G1 analysis showed a statistically significant difference between 100 and 500 nM (P<0.005), 100 and 1000 nM (P<0.001), 300 and 1000 nM (P<0.001), and 500 and 1000 nM (P<0.001). Flavopiridol also significantly influenced the cells in the G2/M phase, particularly at high-dose treatments. Flavopiridol induced growth inhibition and apoptosis at the IC50 dose (500 nM), resulting in a significant increase in immunofluorescence staining of caspase-3, caspase-8 and p53. In conclusion, the present results indicated that flavopiridol could be a useful therapeutic agent for prostate CSCs by inhibiting tumor growth and malignant progression, and inducing apoptosis.

SOX2OT variant 7 contributes to the synergistic interaction between EGCG and Doxorubicin to kill osteosarcoma via autophagy and stemness inhibition

“…CD133 is considered to be the most common CSC marker, and has been used repeatedly for the successful isolation of osteosarcoma stem cells [19]. A growing number of studies have found that using immunomagnetic double positive screening could obtain CSCs with higher purity and stemness [20,21]. In this study, stem cell like cells were obtained from osteosarcoma cells by CD133+/CD44+ immunomagnetic beads double positive screening method and the isolated CD133+/CD44+ CSCs were identified by flow cytometry analysis.…”

Targeting CDK9: a promising therapeutic opportunity in prostate cancer

“…Following the demonstration of promising cytotoxic activities in preclinical models (Drees et al 1997, Soner et al 2014, flavopiridol was introduced to several clinical trials to various cancers such as gastric (Schwartz et al 2001), lung (Shapiro et al 2001), colon (Aklilu et al 2003), renal cell (Stadler et al 2000) and prostate (Liu et al 2004) cancers. Particularly, a multicenter phase II clinical trial was conducted using flavopiridol against hormoneindependent PCa and the results showed that flavopiridol was unsatisfactory as a stand-alone therapeutic agent (Liu et al 2004), due to its narrow therapeutic index which made drug scheduling and administration challenging.…”

Ribosome biogenesis mediates antitumor activity of flavopiridol in CD44+/CD24‑ breast cancer stem cells

“…The number of publications involving the effect of flavopiridol on CSC is quite limited. Soner et al ( 19 ) demonstrated that flavopiridol induced growth inhibition and apoptosis by the upregulation of p53 and caspases 3 and 8 in CD133 + /CD44 + prostrate CSCs.…”

“…This flavonoid is a promising anticancer drug that is undergoing phase I and II clinical trials for chronic myeloid leukemia and pancreatic cancer ( 17 , 18 ). Our previous study demonstrated that flavopiridol induced growth inhibition and apoptosis in CD133 + /CD44 + prostate CSCs ( 19 ).…”