31 research outputs found
Histone deacetylases 1, 2 and 3 are highly expressed in prostate cancer and HDAC2 expression is associated with shorter PSA relapse time after radical prostatectomy
High activity of histone deacetylases (HDACs) causes epigenetic alterations associated with malignant cell behaviour. Consequently, HDAC inhibitors have entered late-phase clinical trials as new antineoplastic drugs. However, little is known about expression and function of specific HDAC isoforms in human tumours including prostate cancer. We investigated the expression of class I HDACs in 192 prostate carcinomas by immunohistochemistry and correlated our findings to clinicopathological parameters including follow-up data. Class I HDAC isoforms were strongly expressed in the majority of the cases (HDAC1: 69.8%, HDAC2: 74%, HDAC3: 94.8%). High rates of HDAC1 and HDAC2 expression were significantly associated with tumour dedifferentiation. Strong expression of all HDACs was accompanied by enhanced tumour cell proliferation. In addition, HDAC2 was an independent prognostic marker in our prostate cancer cohort. In conclusion, we showed that the known effects of HDACs on differentiation and proliferation of cancer cells observed in vitro can also be confirmed in vivo. The class I HDAC isoforms 1, 2 and 3 are differentially expressed in prostate cancer, which might be important for upcoming studies on HDAC inhibitors in this tumour entity. Also, the highly significant prognostic value of HDAC2 clearly deserves further study
Persistent ER Stress Induces the Spliced Leader RNA Silencing Pathway (SLS), Leading to Programmed Cell Death in Trypanosoma brucei
Trypanosomes are parasites that cycle between the insect host (procyclic form) and mammalian host (bloodstream form). These parasites lack conventional transcription regulation, including factors that induce the unfolded protein response (UPR). However, they possess a stress response mechanism, the spliced leader RNA silencing (SLS) pathway. SLS elicits shut-off of spliced leader RNA (SL RNA) transcription by perturbing the binding of the transcription factor tSNAP42 to its cognate promoter, thus eliminating trans-splicing of all mRNAs. Induction of endoplasmic reticulum (ER) stress in procyclic trypanosomes elicits changes in the transcriptome similar to those induced by conventional UPR found in other eukaryotes. The mechanism of up-regulation under ER stress is dependent on differential stabilization of mRNAs. The transcriptome changes are accompanied by ER dilation and elevation in the ER chaperone, BiP. Prolonged ER stress induces SLS pathway. RNAi silencing of SEC63, a factor that participates in protein translocation across the ER membrane, or SEC61, the translocation channel, also induces SLS. Silencing of these genes or prolonged ER stress led to programmed cell death (PCD), evident by exposure of phosphatidyl serine, DNA laddering, increase in reactive oxygen species (ROS) production, increase in cytoplasmic Ca2+, and decrease in mitochondrial membrane potential, as well as typical morphological changes observed by transmission electron microscopy (TEM). ER stress response is also induced in the bloodstream form and if the stress persists it leads to SLS. We propose that prolonged ER stress induces SLS, which serves as a unique death pathway, replacing the conventional caspase-mediated PCD observed in higher eukaryotes
Serum depletion induces changes in protein expression in the trophoblast-derived cell line HTR-8/SVneo
Dual Inhibitors of Inosine Monophosphate Dehydrogenase and Histone Deacetylases for Cancer Treatment
Therapeutic Concentrations of Mitoxantrone Elicit Energetic Imbalance in H9c2 Cells as an Earlier Event
Mitoxantrone (MTX) is a chemotherapeutic
agent that emerged as an alternative to anthracycline therapy.
However, MTX also causes late cardiotoxicity, being
oxidative stress and mitochondrial-impaired function proposed
as possible mechanisms. This work aimed to investigate
the relevance of these mechanisms to the MTX
toxicity in H9c2 cells, using therapeutic concentrations. The
observed cytotoxicity of MTX was time and concentration
dependent in both lactate dehydrogenase leakage assay and
MTT reduction assay. Two therapeutic concentrations (100
nM and 1 lM) and three time points were selected (24, 48,
and 96 h) for further studies. Both MTX concentrations
caused a significant increase in caspase-3 activity, which
was not prevented by inhibiting MTX CYP450-metabolism.
Significant decreases were observed in the total and reduced
glutathione levels only in MTX 100 nM at 96 h; however,
neither alterations in oxidized glutathione nor increases in
the malondialdehyde levels were observed at any time or
concentrations tested. On the other hand, changes in the
intracellular ATP levels, mitochondrial membrane potential,
and intracellular calcium levels were observed in both
concentrations and all time tested. Noteworthy, decreased
levels of ATP-synthase expression and activity and
increases in the reactive species generation were observed
at 96 h in both working concentrations. However, the radical
scavenger N-acetylcysteine or the mitochondrial function
enhancer L-carnitine did not prevent MTX cytotoxicity.
Thus, this work evidenced the early MTX-induced energetic
crisis as a possible key factor in the cell injury.This work received financial support from
‘‘Fundação para a Ciência e Tecnologia (FCT),’’ Portugal (EXPL/
DTP-FTO/0290/2012) and by ‘‘Fundo Comunitário Europeu’’
(FEDER) under the frame of ‘‘Eixo I do Programa Operacional Fatores
de Competitividade (POFC) do QREN’’ (COMPETE: FCOMP-
01-0124-FEDER-027749). The work was also supported by FCT
within the framework of Strategic Projects for Scientific Research
Units of R&D (project PEst-C/EQB/LA0006/2011). LGR and VVB
thank FCT for their PhD Grant (SFRH/BD/63473/2009 and SFRH/
BD/82556/2011, respectively) and VMC thank FCT for her Post-doc
Grant (SFRH/BPD/63746/2009)
Perifosine induces cell cycle arrest and apoptosis in human hepatocellular carcinoma cell lines by blockade of Akt phosphorylation
Hepatocellular carcinoma (HCC) is one of the most common solid cancers, representing the third cause of cancer-related death among cirrhotic patients. Treatment of advanced HCC has become a very active area of research. Perifosine, a new synthetic alkylphospholipid Akt inhibitor, has shown anti-tumor activity by inhibition of Akt phosphorylation. In this study, the effect of perifosine on the cell proliferation and apoptosis in hepatoma cells has been investigated. Cell growth inhibition was detected by MTT assay, cell cycle was analyzed by flow cytometry, AnnexinV-FITC apoptosis detection kit was used to detect cell apoptosis, and protein expression was examined by Western blotting analysis. Our present studies showed that Akt phosphorylation was inhibited by perifosine in HepG2 and Bel-7402 human hepatocellular carcinoma cells. Perifosine inhibited the growth of HepG2 cells and Bel-7402 cells in a dose-dependent manner, and arrested cell cycle progression at the G2 phase. Apoptosis induction became more effective with increasing perifosine concentration. The caspase cascade and its downstream effectors, Poly (ADP-ribose) polymerase (PARP), were also activated simultaneously upon perifosine treatment. The proapoptotic effect of perifosine was in part depending on regulation of the phosphorylation level of ERK and JNK. Perifosine cotreatment substantially increased cytotoxic effects of cisplatin in HepG2 cells. Down-regulating the expression of Bcl-2 and up-regulating the level of Bax may be the potential mechanism for this synergistic effect. Our findings suggest that the small molecule Akt inhibitor perifosine shows substantial anti-tumor activity in human hepatoma cancer cell lines, and is a good candidate for treatment combinations with classical cytostatic compounds in hepatocellular carcinoma