Sequential combination of flavopiridol and docetaxel reduces the levels of X-linked inhibitor of apoptosis and AKT proteins and stimulates apoptosis in human LNCaP prostate cancer cells

Clinical trials have shown that chemotherapy with docetaxel combined with prednisone can improve survival of patients with androgen-independent prostate cancer. It is likely that the combination of docetaxel with other novel chemotherapeutic agents would also improve the survival of androgen-independent prostate cancer patients. We investigated whether the combination of docetaxel and flavopiridol, a broad cyclin-dependent kinase inhibitor, can increase apoptotic cell death in prostate cancer cells. Treatment of DU 145 prostate cancer cells with 500 nmol/L flavopiridol and 10 nmol/L docetaxel inhibited apoptosis probably because of their opposing effects on cyclin B1-dependent kinase activity. In contrast, when LNCaP prostate cancer cells were treated with flavopiridol for 24 hours followed by docetaxel for another 24 hours (FD), there was a maximal induction of apoptosis. However, there was greater induction of apoptosis in DU 145 cells when docetaxel was followed by flavopiridol or docetaxel. These findings indicate a heterogeneous response depending on the type of prostate cancer cell. Substantial decreases in X-linked inhibitor of apoptosis (XIAP) protein but not survivin, both being members of the IAP family, were required for FD enhanced apoptosis in LNCaP cells. Androgen ablation in androgen-independent LNCaP cells increased activated AKT and chemoresistance to apoptosis after treatment with FD. The proteasome inhibitor MG-132 blocked FD-mediated reduction of XIAP and AKT and antagonized apoptosis, suggesting that the activation of the proteasome pathway is one of the mechanisms involved. Overall, our data suggest that the docetaxel and flavopiridol combination requires a maximal effect on cyclin B1-dependent kinase activity and a reduction of XIAP and AKT prosurvival proteins for augmentation of apoptosis in LNCaP cells

A role for GATA transcription factors in the androgen regulation of the prostate-specific antigen gene enhancer

The transgenic mouse line Gγ/T-15 containing the fetal globin promoter linked to SV40 T antigen unexpectedly results in androgen-independent prostate carcinomas. Given the key role of GATA-1 transcription factor in fetal globin gene promoter activity, we investigated whether specific GATA family members are expressed in the prostate and whether they can regulate prostate-specific genes. We found that GATA-2 and -3 are the predominant GATA family members expressed in human and mouse prostate and that GATA mRNA levels are not regulated by androgen. We identified six GATA sites flanking an androgen-response element located in the far-upstream enhancer of the prostate-specific antigen (PSA) gene. These GATA sites are targets for GATA factors and are essential for optimal androgen induction of transfected PSA enhancer/promoter plasmids in LNCaP, a PSA and androgen receptor expressing human prostate cancer cell line. Our results suggest that prostatic GATA-2 and -3 are involved in the androgen regulation of the PSA gene

Low dose combinations of 2-methoxyestradiol and docetaxel block prostate cancer cells in mitosis and increase apoptosis

Clinical trials have shown that chemotherapy with docetaxel (Doc) combined with prednisone can improve survival of patients with androgen-independent prostate cancer (AI-PC). It is likely that the combination of Doc with other novel agents would also improve the survival of AI-PC patients. We investigated whether the combination of Doc and 2-methoxyestradiol (2ME2), an endogenous metabolite of estradiol promising for cancer therapy, can increase apoptotic cell death in prostate cancer cells. Low concentration 2ME2 (0.5−1 μM) + Doc (0.05−0.1 nM) combinations inhibit cell growth, increase G2/M cell cycle arrest, and increase apoptosis more effectively than the single concentrations in a variety of human AI-PC cells. Effects on apoptosis were associated with an increase in p53 protein and a decrease in cyclin A-dependent kinase activity. We then investigated whether the combination of 2ME2 + Doc can increase apoptotic cell death and inhibit the growth of prostate tumors in the FG/Tag transgenic mouse model of AI-PC. Doses of 2ME2 and Doc that increase mitotic cell cycle arrest result in an increase in apoptosis and lower primary prostate tumor weights in FG/Tag mice. High dose 2ME2 + Doc combinations did not increase G2/M cell cycle arrest or apoptosis in AI-PC cell lines and in the FG/Tag mice more than the single drugs. Overall, our data indicate that low dose 2ME2 + Doc combinations may provide a treatment strategy that can improve therapeutic efficacy against AI-PC while reducing toxicity often seen in patients treated with Doc

El H20 como vapor estándar en la Mordenita natural cubana con cationes monovalentes

La Teoría del Llenado Volumétrico de Microporos de Dubinin (TLIVM), describe con buena aproximación la adsorción de diferentes sustancias, en adsorbentes microporosos, a temperaturas inferiores a la crítica. Esta teoría se basa en la existencia de un campo de adsorción en los microporos del sólido que determina su llenado volumétrico, por lo que el concepto de superficie específica deja de tener sentido y es sustituido por el de volumen de microporos (Vm). Como el espacio para la adsorción está restringido por este último, esto implica la existencia de una adsorción máxima o límite (Nm) que es el número máximo de moles que pueden acomodarse en Vm

Increased expression of cyclin B1 sensitizes prostate cancer cells to apoptosis induced by chemotherapy

Chemotherapeutic drugs ideally should take advantage of the differences between transformed and normal cells and induce apoptosis only in cancer cells. One such difference may be the overexpression of cyclin B1 protein in cancer cells, which is required for the proper progression through mitosis. Previously, we showed that treatment of human prostate cancer cells with 2-methoxyestradiol (2-ME) or docetaxel results in an accumulation of cyclin B1 protein and an increase in cyclin B1 kinase activity, followed by induction of apoptotic cell death. Inhibition of cyclin B1 kinase lowers apoptosis induced by 2-ME and docetaxel. In this study, we established a positive correlation between cyclin B1 protein and apoptosis induced by chemotherapy in prostate cancer cells. There is minimal cyclin B1 and induction of apoptosis by chemotherapy in nontransformed cells. LNCaP and PC-3 prostate cancer cells stably overexpressing cyclin B1 are more sensitive to apoptosis induced by chemotherapy. LNCaP cells expressing cyclin B1 small interfering RNA to lower cyclin B1 protein or dominant negative cyclin-dependent kinase 1 to inhibit cyclin B1 kinase show a decrease in apoptosis. Increased sensitivity to apoptosis by overexpression of cyclin B1 may be due to lower Bcl-2, higher p53, and decreased neuroendocrine differentiation. We suggest that a cancer-specific mechanism whereby 2-ME and docetaxel may exert anti-prostate cancer activity is the deregulated activation of cyclin B1 kinase, leading to the induction of apoptotic cell death. Our results also suggest that higher levels of cyclin B1 in prostate cancer cells may be a good prognostic marker for chemotherapy

Changes in the Expression of Genes Associated with Intraneuronal Amyloid-β and Tau in Alzheimer's Disease

The clinical hallmark of Alzheimer's disease (AD) is impairment of cognition associated with loss of synapses, accumulation of amyloid β (Aβ) both within neurons and as extracellular deposits, and neurofibrillary degeneration composed of phospho-tau. Neurons in the hippocampus are among those that are most vulnerable. The purpose of this study was to investigate the expression of genes associated with cognition, synapse, and mitochondrial function in hippocampal neurons of AD compared to normal individuals. Neurons from the hippocampus with intraneuronal Aβ immunoreactivity were captured with laser microdissection; RNA was extracted; and levels of brain-derived neurotrophic factor (BDNF), TrkB (BDNF receptor), dynamin-1 (DYN), and cytochrome C oxidase subunit II (COX2) were assessed with quantitative real time-polymerase chain reaction. We found no significant differences in the expression of these genes in AD between neurons associated with Aβ compared to those lacking Aβ immunoreactivity. Double immunofluorescence microscopy showed the number of hippocampal neurons coexpressing Aβ or phospho-tau and either BDNF, TrkB, or DYN was similar in AD and controls. Our results suggest that intraneuronal Aβ or phospho-tau do not have obligatory effects on reducing the expression of genes important for memory and cognition in hippocampus of AD