Decreased expression of the pro-apoptotic protein Par-4 in renal cell carcinoma.
(1/8107)
Par-4 is a widely expressed leucine zipper protein that confers sensitization to apoptosis induced by exogenous insults. Because the expression of genes that promote apoptosis may be down-regulated during tumorigenesis, we sought to examine the expression of Par-4 in human tumors. We present here evidence that Par-4 protein levels were severely decreased in human renal cell carcinoma specimens relative to normal tubular cells. Replenishment of Par-4 protein levels in renal cell carcinoma cell lines conferred sensitivity to apoptosis. Because apoptosis may serve as a defense mechanism against malignant transformation or progression, decreased expression of Par-4 may contribute to the pathophysiology of renal cell carcinoma. (+info)
Tumour ablation and hepatic decompensation rates in multi-agent chemoembolization of hepatocellular carcinoma.
(2/8107)
Thirty-seven cirrhotic patients with 62 hepatocellular carcinoma (HCC) foci--most Child-Pugh class B or C and/or with large, inoperable tumours--underwent 148 sessions of transcatheter arterial chemoembolization (TACE) using lipiodol, doxorubicin and cisplatin. Treatment efficacy was assessed by serial hepatic arteriography in 34/37 (91.9%) patients and abdominal CT scanning in 3/37 (8.1%) patients. Child-Pugh status was determined prior to each treatment session. Varying degrees of control of tumour neovascularity occurred for a median 390 days (range 90 to > 1680 days) in 33/34 (97.1%) patients in whom progress hepatic arteriography was performed. Ablation of tumour neovascularity occurred in 6/6 (100%), 4/12 (33.3%) and 6/16 (37.5%) patients with HCC diameters < 4 cm, 4-7 cm and > 8 cm, respectively (p < 0.02). Significantly more sessions were required for ablation of larger tumours (p < 0.05). Recurrent HCC was detected in 50% of patients after a median 240 days (range 60-1120 days). Deterioration in Child-Pugh status followed a session of TACE on 19/148 (12.8%) occasions but resulted in unscheduled hospitalization on only 4/148 (2.7%) occasions, the highest incidence (8.3%) in Child-Pugh C patients. Actuarial survival was 27/36 (75.0%) at 6 months, 17/34 (50.0%) at 12 months, 14/34 (41.2%) at 18 months, 9/31 (29.0%) at 24 months and 4/27 (14.8%) at 36 months. Multi-agent TACE with lipiodol, doxorubicin and cisplatin provides a useful anti-tumour effect, even in cirrhotic patients with large HCCs. The incidence of clinically significant deterioration in hepatic function due to ischaemia of non-tumorous liver is acceptably low, even in Child-Pugh C patients. (+info)
Inhibition of doxorubicin toxicity in cultured neonatal mouse cardiomyocytes with elevated metallothionein levels.
(3/8107)
Controversial results have been reported regarding whether metallothionein (MT) functions in doxorubicin (DOX) detoxification in the heart. To determine unequivocally the role of MT in cardiac protection against the toxicity of DOX, ventricular cardiomyocytes isolated from 1- to 3-day neonatal transgenic mice with high levels of cardiac MT and from nontransgenic control animals were applied. On the 6th day of culturing, MT concentrations in the transgenic cardiomyocytes were about 2-fold higher than those in the nontransgenic cells. DOX was added directly into the cultures. Compared with nontransgenic controls, transgenic cardiomyocytes displayed a significant (p <.05) resistance to DOX cytotoxicity, as measured by morphological alterations, cell viability, and lactate dehydrogenase leakage from the cells. This cytoprotective effect of MT correlated with its inhibition of DOX-induced lipid peroxidation. These observations demonstrate unequivocally that elevation of MT concentrations in the cardiomyocytes of 2-fold higher than normal provides efficient protection against DOX toxicity. (+info)
1,25-Dihydroxyvitamin D3 enhances the susceptibility of breast cancer cells to doxorubicin-induced oxidative damage.
(4/8107)
1,25-Dihydroxyvitamin D3 (1,25(OH)2D3), the hormonal form of vitamin D, has anticancer activity in vivo and in vitro. Doxorubicin exerts its cytotoxic effect on tumor cells mainly by two mechanisms: (a) generation of reactive oxygen species (ROS); and (b) inhibition of topoisomerase II. We studied the combined cytotoxic action of 1,25(OH)2D3 and doxorubicin on MCF-7 breast cancer cells. Pretreatement with 1,25(OH)2D3 resulted in enhanced cytotoxicity of doxorubicin. The average enhancing effect after a 72-h pretreatment with 1,25(OH)2D3 (10 nM) followed by a 24-h treatment with 1 microg/ml doxorubicin was 74+/-9% (mean +/- SE). Under these experimental conditions, 1,25(OH)2D3 on its own did not affect cell number or viability. 1,25(OH)2D3 also enhanced the cytotoxic activity of another ROS generating quinone, menadione, but did not affect cytotoxicity induced by the topoisomerase inhibitor etoposide. The antioxidant N-acetylcysteine slightly reduced the cytotoxic activity of doxorubicin but had a marked protective effect against the combined action of 1,25(OH)2D3 and doxorubicin. These results indicate that ROS are involved in the interaction between 1,25(OH)2D3 and doxorubicin. 1,25(OH)2D3 also increased doxorubicin cytotoxicity in primary cultures of rat cardiomyocytes. Treatment of MCF-7 cells with 1,25(OH)2D3 alone markedly reduced the activity, protein, and mRNA levels of the cytoplasmic antioxidant enzyme Cu/Zn superoxide dismutase, which indicated that the hormone inhibits its biosynthesis. This reduction in the antioxidant capacity of the cells could account for the synergistic interaction between 1,25(OH)2D3 and doxorubicin and may also suggest increased efficacy of 1,25(OH)2D3 or its analogues in combination with other ROS-generating anticancer therapeutic modalities. (+info)
Cell adhesion mediated drug resistance (CAM-DR): role of integrins and resistance to apoptosis in human myeloma cell lines.
(5/8107)
Integrin-mediated adhesion influences cell survival and may prevent programmed cell death. Little is known about how drug-sensitive tumor cell lines survive initial exposures to cytotoxic drugs and eventually select for drug-resistant populations. Factors that allow for cell survival following acute cytotoxic drug exposure may differ from drug resistance mechanisms selected for by chronic drug exposure. We show here that drug-sensitive 8226 human myeloma cells, demonstrated to express both VLA-4 (alpha4beta1) and VLA-5 (alpha5beta1) integrin fibronectin (FN) receptors, are relatively resistant to the apoptotic effects of doxorubicin and melphalan when pre-adhered to FN and compared with cells grown in suspension. This cell adhesion mediated drug resistance, or CAM-DR, was not due to reduced drug accumulation or upregulation of anti-apoptotic Bcl-2 family members. As determined by flow cytometry, myeloma cell lines selected for drug resistance, with either doxorubicin or melphalan, overexpress VLA-4. Functional assays revealed a significant increase in alpha4-mediated cell adhesion in both drug-resistant variants compared with the drug-sensitive parent line. When removed from selection pressure, drug-resistant cell lines reverted to a drug sensitive and alpha4-low phenotype. Whether VLA-4-mediated FN adhesion offers a survival advantage over VLA-5-mediated adhesion remains to be determined. In conclusion, we have demonstrated that FN-mediated adhesion confers a survival advantage for myeloma cells acutely exposed to cytotoxic drugs by inhibiting drug-induced apoptosis. This finding may explain how some cells survive initial drug exposure and eventually express classical mechanisms of drug resistance such as MDR1 overexpression. (+info)
Combination of theanine with doxorubicin inhibits hepatic metastasis of M5076 ovarian sarcoma.
(6/8107)
Theanine is a peculiar amino acid existing in green tea leaves, which was previously indicated to enhance the antitumor activity of doxorubicin. In the present study, the effect of combination of theanine with doxorubicin against hepatic metastasis of M5076 ovarian sarcoma was investigated. The primary tumor was significantly reduced by the combined treatment on M5076 transplanted (s.c.) mice. The liver weight of control mice increased to twice the normal level because of hepatic metastasis of M5076. In contrast, the injection of doxorubicin alone or theanine plus doxorubicin suppressed the increase in liver weight and inhibited hepatic metastasis. Moreover, the liver weights and metastasis scores demonstrated that theanine enhanced the inhibition of hepatic metastasis induced by doxorubicin. Furthermore, in vitro experiments indicated that theanine increased the intracellular concentration of doxorubicin remaining in M5076 cells. This action suggests that theanine leads the enhancement of the suppressive efficacy of doxorubicin on hepatic metastasis in vivo. Therefore, it was proved that theanine increased not only the antitumor activity on primary tumor but also the metastasis-suppressive efficacy of doxorubicin. The effect of theanine on the efficacy of antitumor agents is expected to be applicable in clinical cancer chemotherapy. (+info)
Inhibition of p53 transcriptional activity by Bcl-2 requires its membrane-anchoring domain.
(7/8107)
We show here that the anti-apoptosis protein Bcl-2 potently inhibits p53-dependent transcriptional activation of various p53-responsive promoters in reporter gene co-transfection assays in human embryonic kidney 293 and MCF7 cells, without affecting nuclear accumulation of p53 protein. In contrast, Bcl-2(Deltatransmembrane (TM)), which lacks a hydrophobic membrane-anchoring domain, had no effect on p53 activity. Similarly, in MCF7 cells stably expressing either Bcl-2 or Bcl-2(DeltaTM), nuclear levels of p53 protein were up-regulated upon treatment with the DNA-damaging agents doxorubicin and UV radiation, whereas p53-responsive promoter activity and expression of p21(CIP1/WAF1) were strongly reduced in MCF7-Bcl-2 cells but not in MCF7-Bcl-2(DeltaTM) or control MCF7 cells. The issue of membrane anchoring was further explored by testing the effects of Bcl-2 chimeric proteins that contained heterologous transmembrane domains from the mitochondrial protein ActA or the endoplasmic reticulum protein cytochrome b5. Both Bcl-2(ActA) and Bcl-2(Cytob5) suppressed p53-mediated transactivation of reporter gene plasmids with efficiencies comparable to wild-type Bcl-2. These results suggest that (a) Bcl-2 not only suppresses p53-mediated apoptosis but also interferes with the transcriptional activation of p53 target genes at least in some cell lines, and (b) membrane anchoring is required for this function of Bcl-2. We speculate that membrane-anchored Bcl-2 may sequester an unknown factor necessary for p53 transcriptional activity. (+info)
MycN sensitizes neuroblastoma cells for drug-induced apoptosis.
(8/8107)
Amplification of the MYCN gene is found in a large proportion of neuroblastoma and considered as an adverse prognostic factor. To investigate the effect of ectopic MycN expression on the susceptibility of neuroblastoma cells to cytotoxic drugs we used a human neuroblastoma cell line harboring tetracycline-controlled expression of MycN. Neither conditional expression of MycN alone nor low drug concentrations triggered apoptosis. However, when acting in concert, MycN and cytotoxic drugs efficiently induced cell death. Apoptosis depended on mitochondrial permeability transition and activation of caspases, since the mitochondrion-specific inhibitor bongkrekic acid and the caspase inhibitor zVAD-fmk almost completely abrogated apoptosis. Loss of mitochondrial transmembrane potential and release of cytochrome c from mitochondria preceded activation of caspase-8 and caspase-3 and cleavage of PARP. CD95 expression was upregulated by treatment with cytotoxic drugs, while MycN cooperated with cytotoxic drugs to increase sensitivity to CD95-induced apoptosis and enhancing CD95-L expression. MycN overexpression and cytotoxic drugs also synergized to induce p53 and Bax protein expression, while Bcl-2 and Bcl-X(L) protein levels remained unchanged. Since amplification of MYCN is usually associated with a poor prognosis, these findings suggest that dysfunctions in apoptosis pathways may be a mechanism by which MycN-induced apoptosis of neuroblastoma cells is inhibited. (+info)