8-Chloro-cyclic AMP-induced growth inhibition and apoptosis is mediated by p38 mitogen-activated protein kinase activation in HL60 cells.
ABSTRACT 8-Chloro-cyclic AMP (8-Cl-cAMP), which is known to induce growth inhibition, apoptosis, and differentiation in various cancer cell lines, has been studied as a putative anticancer drug. However, the mechanism of anticancer activities of 8-Cl-cAMP has not been fully understood. Previously, we reported that the 8-Cl-cAMP-induced growth inhibition is mediated by protein kinase C (PKC) activation. In this study, we found that p38 mitogen-activated protein kinase (MAPK) also plays important roles during the 8-Cl-cAMP-induced growth inhibition and apoptosis. SB203580 (a p38-specific inhibitor) recovered the 8-Cl-cAMP-induced growth inhibition and apoptosis, whereas other MAPK inhibitors, such as PD98059 (an extracellular signal-regulated kinase-specific inhibitor) and SP600125 (a c-Jun NH2-terminal kinase-specific inhibitor), had no effect. The phosphorylation (activation) of p38 MAPK was increased in a time-dependent manner after 8-Cl-cAMP treatment. Furthermore, SB203580 was able to block PKC activation induced by 8-Cl-cAMP. However, PKC inhibitor (GF109203x) could not attenuate p38 activation, indicating that p38 MAPK activation is upstream of PKC activation during the 8-Cl-cAMP-induced growth inhibition. 8-Chloro-adenosine, a metabolite of 8-Cl-cAMP, also activated p38 MAPK and this activation was blocked by adenosine kinase inhibitor. These results suggest that 8-Cl-cAMP exerts its anticancer activity through p38 MAPK activation and the metabolite(s) of 8-Cl-cAMP mediates this process.
Article: The combination of gamma ionizing radiation and 8-Cl-cAMP induces synergistic cell growth inhibition and induction of apoptosis in human prostate cancer cells[show abstract] [hide abstract]
ABSTRACT: The antiproliferative and cytotoxic potential of the nucleotide analog 8-Cl-cAMP was tested in PC-3 and DU145 metastatic human prostate cancer cells. The drug was examined as the only therapeutic agent and in combination with ionizing irradiation (IR). Highly synergistic effects of IR and 8-Cl-cAMP were observed in both cell lines when examined by the MTT viability and BrdU proliferation assays. The combination of IR and 8-Cl-cAMP at clinically relevant doses exerted substantial growth inhibition. The combination of IR and 8-Cl-cAMP caused a significant disturbance in the distribution of cell cycle phases. Cell cycle arrest in the sub-G0/G1 phase predominated in both cell lines. The most striking observation was a significant increase in apoptotic PC-3 and DU145 cells. The DU145 cells were three times more sensitive to the combined treatment than PC-3 cells. The initial resistance to IR-induced apoptosis in these p53-deficient prostate cancer cell lines was overcome through an alternative proapoptotic pathway induced by 8-Cl-cAMP. Considering the low effective doses of treatments, improved tumor eradication rates and minimal undesirable side effects, the combination of IR and 8-Cl-cAMP could be the therapy of choice in treating prostate cancer.Investigational New Drugs 01/2008; 26(4):309-317. · 3.36 Impact Factor
Article: 8-Chloro-cyclic AMP and protein kinase A I-selective cyclic AMP analogs inhibit cancer cell growth through different mechanisms.[show abstract] [hide abstract]
ABSTRACT: Cyclic AMP (cAMP) inhibits the proliferation of several tumor cells. We previously reported an antiproliferative effect of PKA I-selective cAMP analogs (8-PIP-cAMP and 8-HA-cAMP) on two human cancer cell lines of different origin. 8-Cl-cAMP, another cAMP analog with known antiproliferative properties, has been investigated as a potential anticancer drug. Here, we compared the antiproliferative effect of 8-Cl-cAMP and the PKA I-selective cAMP analogs in three human cancer cell lines (ARO, NPA and WRO). 8-Cl-cAMP and the PKA I-selective cAMP analogs had similarly potent antiproliferative effects on the BRAF-positive ARO and NPA cells, but not on the BRAF-negative WRO cells, in which only 8-Cl-cAMP consistently inhibited cell growth. While treatment with the PKA I-selective cAMP analogs was associated with growth arrest, 8-Cl-cAMP induced apoptosis. To further investigate the actions of 8-Cl-cAMP and the PKA I-selective cAMP analogs, we analyzed their effects on signaling pathways involved in cell proliferation and apoptosis. Interestingly, the PKA I-selective cAMP analogs, but not 8-Cl-cAMP, inhibited ERK phosphorylation, whereas 8-Cl-cAMP alone induced a progressive phosphorylation of the p38 mitogen-activated protein kinase (MAPK), via activation of AMPK by its metabolite 8-Cl-adenosine. Importantly, the pro-apoptotic effect of 8-Cl-cAMP could be largely prevented by pharmacological inhibition of the p38 MAPK. Altogether, these data suggest that 8-Cl-cAMP and the PKA I-selective cAMP analogs, though of comparable antiproliferative potency, act through different mechanisms. PKA I-selective cAMP analogs induce growth arrest in cells carrying the BRAF oncogene, whereas 8-Cl-cAMP induce apoptosis, apparently through activation of the p38 MAPK pathway.PLoS ONE 01/2011; 6(6):e20785. · 4.09 Impact Factor
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ABSTRACT: To assess the cytogenetic effects in vitro and in vivo of a non-cytotoxic antitumor agent with biomodulator activity, 8-chloro-3',5' cyclic adenosine monophosphate (8-ClcAMP). Cytogenetic effects of 8-Cl-cAMP where evaluated using the in vitro chromosome cytogenetic assay (CA) on human peripheral blood lymphocytes of healthy individuals and by bone marrow micronucleus assay in adult BALB/c mice. In the in vitro chromosome CA, 8-Cl-cAMP (in all respective doses; 1.5 and 15 microm) induced mitotic inhibition and premature centromere separation (PCS) but no chromosomal damage in cultured human peripheral blood lymphocytes. In the in vivo test, single intraperitoneal (i.p.) injection of 8-Cl-cAMP in doses of 10, 80 and 150 mg/kg showed a dose-related effect on the frequency of micronuclei, detected in murine polychromatic erythrocytes (PCE). The results of the present study show that genotoxicity of 8-Cl-cAMP has a different matrix of response when comparing results in vitro and in vivo, suggesting that high metabolic activity in vivo is responsible for the clastogenic potential of 8-Cl-cAMP. These comparative results indicate a need of having an available battery of genotoxic tests in order to evaluate possible cytogenetic effects of novel antitumor agents.Journal of B.U.ON.: official journal of the Balkan Union of Oncology 01/2009; 14(1):71-77. · 0.61 Impact Factor