Combined antitumor activity of 7-hydroxystaurosporine (UCN-01) and tamoxifen against human breast carcinoma in vitro and in vivo

CDK/CCN and CDKI alterations for cancer prognosis and therapeutic predictivity

The regulation of cell growth and division occurs in an accurate sequential manner. It is dictated by the accumulation of cyclins (CCNs) and cyclin-dependent kinases (CDKs) complexes and degradation of CCNs. In human tumors, instead, the cell cycle is deregulated, causing absence of differentiation and aberrant cell growth. Oncogenic alterations of CCNs, CDKs, and CDKIs have been reported in more than 90% of human cancers, and the most frequent are those related to the G1 phase. Several molecular mechanisms, including gene overexpression, chromosomal translocations, point mutations, insertions and deletions, missense and frame shift mutation, splicing, or methylation, may be responsible for these alterations. The cell cycle regulators are involved in tumor progression given their association with cancers characterized by higher incidence of relapses and chemotherapy resistance. In the last decade anticancer drug researches focused on new compounds, able to target molecules related to changes in genes associated with tumor status. Recently, the studies have focused on the restoration of cell cycle control modulating molecular targets involved in cancer-cell alterations. This paper aims to correlate alterations of cell cycle regulators with human cancers and therapeutic responsivity.

PUMA induction by FoxO3a mediates the anticancer activities of the broad-range kinase inhibitor UCN-01

Most targeted anticancer drugs are inhibitors of kinases that are aberrantly activated in cancer cells. However, the mechanisms by which kinase inhibitors suppress tumor growth remain unclear. In this study, we found that UCN-01, a staurosporine analogue and broad-range kinase inhibitor used in clinical trials, inhibits colon cancer cell growth by inducing apoptosis via PUMA, a BH3-only Bcl-2 family member and a p53 target. PUMA expression was markedly elevated in a p53-independent fashion following UCN-01 treatment. The induction of PUMA by UCN-01 was mediated by direct binding of FoxO3a to the PUMA promoter following inhibition of AKT signaling. Deficiency in PUMA abrogated UCN-01-induced apoptosis, caspase activation, and mitochondrial dysfunction, and rendered UCN-01 resistance in a clonogenic assay, whereas elevated PUMA expression or a BH3 mimetic sensitized UCN-01 induced apoptosis. Chemosensitization by UCN-01 seemed to involve simultaneous PUMA induction through both p53-dependent and p53-independent mechanisms. Furthermore, deficiency in PUMA suppressed the antitumor effects of UCN-01 in a xenograft model, concurrent with reduced apoptosis and caspase activation in vivo. These results suggest that PUMA-mediated apoptosis is pivotal for the anticancer activities of UCN-01, and possibly other clinically used kinase inhibitor drugs, and that PUMA manipulation may be useful for improving their anticancer activities.

Elesclomol, counteracted by Akt survival signaling, enhances the apoptotic effect of chemotherapy drugs in breast cancer cells

Elesclomol is a small-molecule investigational agent that selectively induces apoptosis in cancer cells by increasing oxidative stress. Elesclomol plus paclitaxel was shown to prolong progression-free survival compared with paclitaxel alone in a phase II clinical trial in patients with metastatic melanoma. However, the therapeutic potential of elesclomol in human breast cancer is unknown, and the signaling mechanism underlying the elesclomol effect is unclear. Here, we show that elesclomol alone modestly inhibited the growth of human breast cancer cells but not normal breast epithelial cells. Elesclomol potentiated doxorubicin- or paclitaxel-induced apoptosis and suppression of breast cancer cell growth. While both c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase were activated by elesclomol, elesclomol-induced apoptosis was only in part mediated by JNK1. The additive effect of elesclomol on chemotherapy drug-induced apoptosis was associated with increases in cleaved caspase-3, p21(Cip1), and p27(Kip1) and decreases in the Inhibitor of Apoptosis Protein levels and NF-kappaB activity. We also found that Akt/Hsp70 survival signaling was induced by elesclomol, which may reflect a cellular feedback mechanism. Blockade of Akt activation using a small-molecule inhibitor enhanced elesclomol-elicited apoptosis, while expression of a hyperactive Akt abolished the elesclomol effect. These data suggest that elesclomol's interaction with conventional chemotherapeutic and Akt-targeting agents may be exploited to induce apoptosis in breast cancer cells, and clinical trials of combined treatment of elesclomol and chemotherapy drugs or Akt-targeting agents in breast cancer patients, especially the estrogen receptor negative subgroup, may be warranted.

Antiestrogenic effect of 20S-protopanaxadiol and its synergy with tamoxifen on breast cancer cells

BACKGROUND

20S-protopanaxadiol (aPPD) is a major gastrointestinal metabolic product of ginsenosides. The latter share structural similarity with steroids and are the main pharmacologically active component in ginseng.

METHODS

The authors investigated the interaction between aPPD and estrogen receptors (ER) in human breast adenocarcinoma MCF-7 cells through receptor binding assay, ER-induced gene expression, and cell proliferation both in vitro and in vivo.

RESULTS

aPPD, but not its close analog ginsenosides, competed with the [(3)H]-17-beta estradiol (E2) for ER with IC(50) at 26.3 microM. aPPD alone weakly induced luciferase reporter-gene expression controlled by an estrogen-regulated element, which was completely blocked by tamoxifen. aPPD alone, or in synergy with tamoxifen, blocked E2-induced transcriptional activation. aPPD also inhibited colony formation of endometrial cancer cells. aPPD potently inhibited estrogen-stimulated MCF-7 cell proliferation and synergistically enhanced the cytotoxicity of tamoxifen on both ER+ MCF-7 and ER- MDA-MB231 cells. Furthermore, aPPD, but not tamoxifen, inhibited Akt phosphorylation. Growth of MCF-7 xenograft tumor supplemented with E2 was completely inhibited in animals treated with aPPD, tamoxifen, or aPPD plus tamoxifen.

CONCLUSIONS

These results suggested that aPPD inhibits estrogen-stimulated gene expression and cell proliferation in ER-positive breast cancer cells. In addition, aPPD synergistically enhances cytotoxicity of tamoxifen in an ER-independent fashion, probably by down-regulating Akt activity.

Effect of 7-hydroxystaurosporine on glioblastoma cell invasion and migration

AIM

To investigate the effect of 7-hydroxystaurosporine (UCN-01), a selective protein kinase C (PKC) inhibitor, on cell growth, migration, and invasion in invasive human glioblastoma U-87MG cells.

METHODS

PKC activity was determined based on the PKC-catalyzed transfer of the (32)P-phosphate group from [g-(32)P]ATP into a PKC-specific peptide substrate. Cell viability was measured by MTT assay. Cell invasion and migration were evaluated by a Boyden chamber assay and scratch wound assay, respectively. Protein expression was analyzed using Western blot assay. The formation of 3-dimensional cellular aggregates was examined by a cell-cell aggregation assay.

RESULTS

UCN-01 treatment resulted in concentration- and time-dependent inhibition of U-87MG cell growth at higher doses (>100 nmol/L), and reduced cell invasion and migration capability at less cytotoxic doses (<100 nmol/L). UCN-01 significantly repressed PKC activity. Consistent with this result, UCN-01 blocked cell invasion stimulated by phorbel 12-myristate-13-acetate (PMA) and ethanol (EtOH), 2 PKC activators. Enforced expression of the tumor suppressor genes BRCA1 and PTEN increased the anti-invasion potential of UCN-01. Exposure to UCN-01 caused a dose-dependent increase in cell adhesion molecule E-cadherin. The effect of UCN-01 on the formation of cell-cell aggregation was significantly reduced by the addition of an anti-E-cadherin antibody.

CONCLUSION

UCN-01 inhibits the invasion and migration of human glioma cells. Accordingly, UCN-01 can have potential clinical applications for the treatment of human glioma metastasis.