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The CDK4/6 inhibitor palbociclib synergizes with irinotecan to promote colorectal cancer cell death under hypoxia.

ABSTRACT: Hypoxia is an inherent impediment to cancer therapy. Palbociclib, a highly selective inhibitor for CDK4/6, has been tested in numerous clinical trials and has been approved by the FDA. We previously reported that CDK inhibitors can destabilize HIF1? regardless of the presence of hypoxia and can sensitize tumor cells to TRAIL through dual blockade of CDK1 and GSK-3?. To translate this knowledge into a cancer therapeutic strategy, we investigated the therapeutic effects and molecular mechanisms of CDK inhibition against colon cancer cells under normoxia and hypoxia. We found that palbociclib sensitizes colon cancer cells to hypoxia-induced apoptotic resistance via deregulation of HIF-1? accumulation. In addition to inhibition of cell proliferation, we observed that palbociclib promotes colon cancer cell death regardless of the presence of hypoxia at a comparatively high concentration via regulating ERK/GSK-3? signaling and GSK-3? expression. Furthermore, palbociclib synergized with irinotecan in a variety of colon cancer cell lines with various molecular subtypes via deregulating irinotecan-induced Rb phosphorylation and reducing HIF-1? accumulation under normoxia or hypoxia. Collectively, our findings provide a novel combination therapy strategy against hypoxic colon cancer cells that may be further translated in the clinic.

SUBMITTER: Zhang J

PROVIDER: S-EPMC5499912 | biostudies-literature | 2017 Jun

REPOSITORIES: biostudies-literature

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The CDK4/6 inhibitor palbociclib synergizes with irinotecan to promote colorectal cancer cell death under hypoxia.

Zhang Jun J Zhou Lanlan L Zhao Shuai S Dicker David T DT El-Deiry Wafik S WS

Cell cycle (Georgetown, Tex.) 20170509 12

Hypoxia is an inherent impediment to cancer therapy. Palbociclib, a highly selective inhibitor for CDK4/6, has been tested in numerous clinical trials and has been approved by the FDA. We previously reported that CDK inhibitors can destabilize HIF1α regardless of the presence of hypoxia and can sensitize tumor cells to TRAIL through dual blockade of CDK1 and GSK-3β. To translate this knowledge into a cancer therapeutic strategy, we investigated the therapeutic effects and molecular mechanisms of ...[more]

PMID: 28486050

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Project description:BACKGROUND:Glioblastoma (GBM) is the most common primary tumor in the brain, and the median survival time for GBM patients is only about 14 months; therefore, there is an urgent need for new and more effective strategies. Since cell cycle disorder is a key factor in tumor progression and immortalization, there is great potential for controlling cell cycle disorders in tumor cells in GBM patients. We began to study a novel combination of AQB and palbociclib to evaluate its potential as a new therapeutic target. METHODS:Protein mass spectrometry was used to identify the tumor suppressor genes up-regulated by AQB.The effects of HOTAIR - EZH2 inhibitor AQB and CDK4/6 inhibitor Palbociclib on glioma cells lines were examined in vitro and in vivo experiments. RESULTS:The combination of AQB and palbociclib inhibitors has a more pronounced suppression effect on the cell cycle, especially gliomas with high expression of HOTAIR and EZH2 and low expression of CWF19L1. We performed protein mass spectrometry to identify AQB upregulated tumor suppressor genes and confirmed that CWF19L1 is regulated by H3K27ac through chromatin immunoprecipitation-quantitative PCR results. Univariate and multivariate Cox regression analysis and database analysis were performed to suggest CWF19L1 is a good prognostic factor. Our experimental results suggested that CWF19L1 can be significantly upregulated by AQB and lead to degradation of CDK4/6, resulting in G1 arrest. The combination of AQB and CDK4/6 inhibitor palbociclib is more effective in inhibiting the growth of glioma than in the single drug, both in vivo and in vitro. Similarly, we found that both AQB and palbociclib can inhibit Wnt/?-catenin signaling, and the combined use of the two inhibitors has a stronger inhibitory effect on tumor metastasis. CONCLUSIONS:The combination of AQB and CDK4/6 inhibitor palbociclib has been found to have significant antitumor effects, which is likely to become a new strategy for glioma treatment.

Project description:In this report, we systematically examined the role of telomerase activity in lung and ovarian cancer stem cell (CSC) propagation. For this purpose, we indirectly gauged telomerase activity, by linking the hTERT-promoter to eGFP. Using lung (A549) and ovarian (SKOV3) cancer cells, transduced with the hTERT-GFP reporter, we then employed GFP-expression levels to fractionate these cell lines into GFP-high and GFP-low populations. We functionally compared the phenotype of these GFP-high and GFP-low populations. More specifically, we now show that the cancer cells with higher telomerase activity (GFP-high) are more energetically activated, with increased mitochondrial mass and function, as well as increased glycolytic activity. This was further validated and confirmed by unbiased proteomics analysis. Cells with high telomerase activity also showed an increased capacity for stem cell activity (as measured using the 3D-spheroid assay) and cell migration (as measured using a Boyden chamber approach). These enhanced biological phenotypes were effectively inhibited by classical modulators of energy metabolism, which target either i) mitochondrial metabolism (i.e., oligomycin) or ii) glycolysis (i.e., 2-deoxy-glucose), or iii) by using the FDA-approved antibiotic doxycycline, which inhibits mitochondrial biogenesis. Finally, the level of telomerase activity also determined the ability of hTERT-high cells to proliferate, as assessed by measuring DNA synthesis via EdU incorporation. Consistent with these observations, treatment with an FDA-approved CDK4/6 inhibitor (PD-0332991/palbociclib) specifically blocked the propagation of both lung and ovarian CSCs. Virtually identical results were obtained with breast CSCs, which were also highly sensitive to palbociclib at concentrations in the nanomolar range. In summary, CSCs with high telomerase activity are among the most energetically activated, migratory and proliferative cell sub-populations. These observations may provide a mechanistic explanation for tumor metabolic heterogeneity, based on telomerase activity. FDA-approved drugs, such as doxycycline and palbociclib, were both effective at curtailing CSC propagation. Thus, these FDA-approved drugs could be used to target telomerase-high proliferative CSCs, in multiple cancer types. Finally, our experiments also allowed us to distinguish two different cellular populations of hTERT-high cells, one that was proliferative (i.e., replicative immortality) and the other that was non-proliferative (i.e., quiescent). We speculate that the non-proliferative population of hTERT-high cells that we identified could be mechanistically involved in tumor dormancy.

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The CDK4/6 inhibitor palbociclib synergizes with irinotecan to promote colorectal cancer cell death under hypoxia.

Publications

The CDK4/6 inhibitor palbociclib synergizes with irinotecan to promote colorectal cancer cell death under hypoxia.

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