Calcium/calmodulin-dependent kinase I and calcium/calmodulin-dependent kinase kinase participate in the control of cell cycle progression in MCF-7 human breast cancer cells

alpha-CaMKII controls the growth of human osteosarcoma by regulating cell cycle progression

Osteosarcoma is the most frequent type of primary bone cancer in children and adolescents. These malignant osteoid forming tumors are characterized by their uncontrolled hyperproliferation. Here, we investigate the role of Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) in the growth of human osteosarcoma. We show that alpha-CaMKII is expressed in human osteosarcoma cell lines and in primary osteosarcoma tissue derived from patients. The pharmacologic inhibition of CaMKII in MG-63 and 143B human osteosarcoma cells by KN-93 resulted in an 80 and 70% decrease in proliferation, respectively, and induced cell cycle arrest in the G(0)/G(1) phase. The in vivo administration of KN-93 to mice xenografted with human osteosarcoma cells significantly decreased intratibial and subcutaneous tumor growth. Mechanistically, KN-93 and alpha-CaMKII siRNA increased p21((CIP/KIP)) gene expression, protein levels, and decreased the phosphorylation of retinoblastoma protein and E2F transactivation. Furthermore, the inhibition of CaMKII decreased membrane-bound Tiam1 and GTP-bound Rac1, which are known to be involved in p21 expression and tumor growth in a variety of solid malignant neoplasms. Our results suggest that CaMKII plays a critical role in the growth of osteosarcoma, and its inhibition could be an attractive therapeutic target to combat conventional high-grade osteosarcoma in children.

Development of a new Ca2+/calmodulin antagonist and its anti-proliferative activity against colorectal cancer cells

We previously identified a cellular target of a cell cycle inhibitor HBC as Ca(2+)/calmodulin (Ca(2+)/CaM) through chemical genetics approach. Using the mechanism-based drug design, we developed a new Ca(2+)/CaM antagonists based on the structure of HBC. The compound, (4-{3,5-bis-[2-(4-hydroxy-3-methoxy-phenyl)-vinyl]-4,5-dihydro-pyrazol-1-yl}-phenyl)-(4-methyl-piperazin-1-yl)-methanone (referred as HBCP), binds to Ca(2+)/CaM in vitro and inhibits the proliferation of HCT15 colon cancer cells. HBCP induced sustained phosphorylation of ERK1/2 and subsequently activated p21(WAF1) expression in HCT15 cells. Moreover, HBCP reversibly induced the G(0)/G(1) cell cycle arrest in the cells. These data demonstrate that HBCP is a new potent Ca(2+)/CaM antagonist and can be applied for CaM related therapeutic uses.

Proteomic analysis of pancreatic endocrine tumor cell lines treated with the histone deacetylase inhibitor trichostatin A

Effects of the histone-deacetylases inhibitor trichostatin A (TSA) on the growth of three different human pancreatic endocrine carcinoma cell lines (CM, BON, and QGP-1) have been assessed via dosage-dependent growth inhibition curves. TSA determined strong inhibition of cell growth with similar IC(50) values for the different cell lines: 80.5 nM (CM), 61.6 nM (BON), and 86 nM (QGP-1), by arresting the cell cycle in G2/M phase and inducing apoptosis. 2DE and nano-RP-HPLC-ESI-MS/MS analysis revealed 34, 33, and 38 unique proteins differentially expressed after TSA treatment in the CM, BON, and QGP-1 cell lines, respectively. The most important groups of modulated proteins belong to cell proliferation, cell cycle, and apoptosis classes (such as peroxiredoxins 1 and 2, the diablo protein, and HSP27). Other proteins pertain to processes such as regulation of gene expression (nucleophosmin, oncoprotein dek), signal transduction (calcium-calmodulin), chromatin, and cytoskeleton organization (calgizzarin, dynein, and lamin), RNA splicing (nucleolin, HNRPC), and protein folding (HSP70). The present data are in agreement with previous proteomic analyses performed on pancreatic ductal carcinoma cell lines (Cecconi, D. et al.., Electrophoresis 2003; Cecconi, D. et al., J. Proteome Res. 2005) and place histone-deacetylases inhibitors among the potentially most powerful drugs for the treatment of pancreatic tumors.

KN-93, a specific inhibitor of CaMKII inhibits human hepatic stellate cell proliferation in vitro

AIM: To investigate the effects of KN-93, a CaMKII selective inhibitor on cell proliferation and the expression of p53 or p21 protein in human hepatic stellate cells.

METHODS: Human hepatic stellate cells (LX-2) were incubated with various concentrations (0-50 μmol/L) of KN-93 or its inactive derivative, KN-92. Cell proliferation was measured by CCK-8 assay, and the expression of two cell cycle regulators, p53 and p21, was determined by SDS-PAGE and Western blotting.

RESULTS: KN-93 (5-50 μmol/L) decreased the proliferation of human hepatic stellate cells in a dose-dependent manner from 81.76% (81.76% ± 2.58% vs 96.63% ± 2.69%, P < 0.05) to 27.15% (27.15% ± 2.86% vs 96.59% ± 2.44%, P < 0.01) after 24 h treatment. Incubation of 10 μmol/L KN-93 induced the cell growth reduction in a time-dependent manner from 78.27% at 8 h to 11.48% at 48 h. However, KN-92, an inactive derivative of KN-93, did not inhibit cell proliferation effectively. Moreover, analysis of cell cycle regulator expression revealed that KN-93 rather than KN-92 reduced the expression of p53 and p21.

CONCLUSION: KN-93 has potent inhibitory effect on proliferation of LX-2 cells by modulating the expression of two special cell cycle regulators, p53 and p21.

Calcium/calmodulin-dependent protein kinases as potential targets in cancer therapy

In this review the authors discuss the expression and activation of a family of protein kinases known as the calcium/calmodulin-dependent kinases (CaM-kinase) and the role that these kinases have in the activation of antiapoptotic signalling pathways. In addition, the authors outline a novel mechanism of activation of these kinases by oxidative stress. Founded on this novel mechanism of activation and the role that these kinases have in activating antiapoptotic signalling pathways, the authors propose that the CaM-kinases would make very good targets for sensitising cancer cells to certain therapeutic treatments. Furthermore, the authors discuss the role that these kinases have in cell transformation and in the regulation of the cell cycle. Based on these roles the authors suggest that inhibition of the CaM-kinases not only has the potential to sensitise cancer cells, but also has the potential to induce cytostasis in these cells.

Nuclear localization of PTEN is regulated by Ca(2+) through a tyrosil phosphorylation-independent conformational modification in major vault protein

We have recently shown in MCF-7 cells that nuclear phosphatase and tensin homologue deleted on chromosome 10 (PTEN) down-regulates phosphorylation of p44/42 and cyclin D1 and induces G(1) cell cycle arrest, whereas cytoplasmic PTEN down-regulates phosphorylation of Akt, up-regulates p27, and induces apoptosis. In this manner, nucleocytoplasmic partitioning of PTEN seems to differentially regulate the cell cycle and apoptosis. We have also reported that PTEN has nuclear localization signal-like sequences required for major vault protein (MVP)-mediated nuclear translocation. To date, several other proteins are reported to interact with MVP, including extracellular signal-regulated kinases and steroid receptors, suggesting that MVP is likely to be involved in signal transduction through nucleocytoplasmic transport. However, the exact mechanism of MVP-mediated nucleocytoplasmic shuttling remains elusive. PTEN reportedly interacts in vitro with the EF hand-like motif of MVP in a Ca(2+)-dependent manner. The current study shows that small interfering RNA-mediated MVP silencing decreases the nuclear localization of PTEN and increases phosphorylation of nuclear p44/42. We show in situ that PTEN-MVP interaction is Ca(2+) dependent and is abolished by Mg(2+). Nuclear localization of PTEN is decreased by increasing Ca(2+) levels in culture medium in a dose-dependent manner. Ca(2+) ionophore A23187 increases nuclear localization of PTEN and decreases phosphorylation of nuclear p44/42. Finally, we show that Ca(2+)-dependent PTEN-MVP interaction is not related to MVP's tyrosil phosphorylation but rather due to its conformational modification. Our observations suggest that Ca(2+) regulates PTEN's nuclear entry through a tyrosil phosphorylation-independent conformational change in MVP. Collectively, our data present evidence of a novel crosstalk between the Ca(2+) signaling-mediated regulation of the cell cycle and MVP-mediated nuclear PTEN localization and function.

gamma-Aminobutyric acid inhibits cholangiocarcinoma growth by cyclic AMP-dependent regulation of the protein kinase A/extracellular signal-regulated kinase 1/2 pathway

We studied the effect of the inhibitory neurotransmitter, gamma-aminobutyric acid (GABA), in the regulation of cholangiocarcinoma growth. We determined the in vitro effect of GABA on the proliferation of the cholangiocarcinoma cell lines (Mz-ChA-1, HuH-28, and TFK-1) and evaluated the intracellular pathways involved. The effect of GABA on migration of Mz-ChA-1 cells was also evaluated. In vivo, Mz-ChA-1 cells were s.c. injected in athymic mice, and the effects of GABA on tumor size, tumor cell proliferation, apoptosis, collagen quantity, and the expression of vascular endothelial growth factor-A (VEGF-A) and VEGF-C (cancer growth regulators) were measured after 82 days. GABA decreased in vitro cholangiocarcinoma growth in a time-dependent and dose-dependent manner, by both cyclic AMP/protein kinase A- and D-myo-inositol-1,4,5-thriphosphate/Ca(2+)-dependent pathways, leading to down-regulation of extracellular signal-regulated kinase 1/2 phosphorylation. Blocking of GABA(A), GABA(B), and GABA(C) receptors prevented GABA inhibition of cholangiocarcinoma proliferation. GABA inhibited Mz-ChA-1 cell migration and, in vivo, significantly decreased tumor volume, tumor cell proliferation, and VEGF-A/C expression whereas increasing apoptosis compared with controls. An increase in collagen was evident in GABA-treated tumors. GABA decreases biliary cancer proliferation and reduces the metastatic potential of cholangiocarcinoma. GABA may represent a therapeutic agent for patients affected by malignancies of the biliary tract.

Calcium transport and signaling in the mammary gland: targets for breast cancer

The mammary gland is subjected to extensive calcium loads during lactation to support the requirements of milk calcium enrichment. Despite the indispensable nature of calcium homeostasis and signaling in regulating numerous biological functions, the mechanisms by which systemic calcium is transported into milk by the mammary gland are far from completely understood. Furthermore, the implications of calcium signaling in terms of regulating proliferation, differentiation and apoptosis in the breast are currently uncertain. Deregulation of calcium homeostasis and signaling is associated with mammary gland pathophysiology and as such, calcium transporters, channels and binding proteins represent potential drug targets for the treatment of breast cancer.