Cancer research
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The majority of p53 mutations are located in the DNA-binding domain of the protein. However, recently a family suffering from Li-Fraumeni syndrome (LFS) has been discovered, some of whom harbor a p53 mutation in exon 4, outside of the core domain. How this mutation affects p53 function and subsequently leads to malignant transformation is not yet clear. ⋯ Here we demonstrate that a mutation in this region is associated not only with resistance of the mutant p53 to Mdm2-mediated degradation, but also with an impaired response of mutant protein to DNA damage. In addition, the p53(LFS) mutant was found to be defective in its transactivation function, which correlated with its inability to suppress cell growth and to induce apoptosis. The molecular basis for p53(LFS) functional impairment appears to be its predominantly cytoplasmic localization caused by faulty nuclear import mechanism, which, at least in part, resulted from the mutant's decreased affinity to importin.
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We have reported previously that among human prostate cancer cell lines LNCaP but not PC-3 cells undergo apoptosis after treatment with the protein kinase inhibitor staurosporine (STS). We have now further investigated this model to uncover the molecular mechanism causing resistance to STS-induced apoptosis in PC-3 cells. S-100 lysates of both cell lines showed biochemical changes typical of apoptosis after the addition of cytochrome c and dATP, suggesting that the postmitochondrial phase of apoptosis was intact. ⋯ A wide search among the antiapoptotic Bcl-2 family members was performed, and Bcl-X(L) was found to be overexpressed in PC-3 cells. Experiments down-regulating Bcl-X(L) expression by using the tyrosine kinase inhibitor genistein, sodium butyrate, or an antisense Bcl-X(L) oligonucleotide restored sensitivity to apoptosis in PC-3 cells. Thus, Bcl-X(L) overexpression is one of the mediators of resistance to STS-induced apoptosis in the prostate cancer cell line PC-3.
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Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is a TNF family member and potent apoptosis inducer. In contrast to TNF-alpha or Fas ligand, relatively little is known about the signaling events activated by TRAIL. In particular, the initial caspase(s) required for TRAIL-induced apoptosis remains to be determined Caspase-3-like protease but not caspase-1-like protease (YVADase) activity rapidly increased in HeLa cells in response to TRAIL treatment. ⋯ The caspase-8-reintro duced caspase-8-deficient Jurkat cells acquired normal susceptibility to both TRAIL and agonistic Fas antibody. Reverse transcription-PCR and sequence analyses have revealed that these caspase-8-deficient Jurkat cell express wild-type caspase-10. Therefore, our data indicate that caspase-8 is required for TRAIL-induced apoptosis and suggest that caspase-10 may play a minor role, if any, in TRAIL-induced apoptosis.
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We have demonstrated that Apo-2 ligand (Apo-2L)/tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) induces apoptosis of human prostate cancer PC-3, DU145, and LNCaP cells in a dose-dependent manner, with PC-3 cells displaying the greatest sensitivity to Apo-2L/TRAIL. Susceptibility of the prostate cancer cell types to Apo-2L/TRAIL-induced apoptosis did not appear to correlate with the levels of the Apo-2L/TRAIL receptors death receptor (DR) 4 (TRAIL receptor 1) or DR5 (TRAIL receptor 2), decoy receptor (DcR) 1 and DcR2, Flame-1, or the inhibitors of apoptosis proteins family of proteins. Apo-2L/TRAIL-induced apoptosis of PC-3 cells was associated with the processing of caspase-8, caspase-10, and the proapoptotic Bid protein, resulting in the cytosolic accumulation of cytochrome c as well as the processing of procaspase-9 and procaspase-3. ⋯ Importantly, sequential treatment of PC-3, DU145, and LNCaP cells with paclitaxel followed by Apo-2L/TRAIL induced significantly more apoptosis than Apo-2L/TRAIL treatment alone (P < 0.01). This was also associated with greater processing of procaspase-8 and Bid, as well as greater cytosolic accumulation of cytochrome c and the processing of caspase-3. These findings indicate that up-regulation of DR4 and DR5 protein levels by treatment with paclitaxel enhances subsequent Apo-2L/TRAIL-induced apoptosis of human prostate cancer cells.
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The acquisition of genetic alterations in tumor cells is a hallmark of cancer progression. Genetic alterations, including chromosomal sequence alterations and abnormal gene expression, increase the malignant potential of tumors by affecting pathways that regulate cell growth, cell death, tumor angiogenesis, and invasion/metastasis. We used an expression profiling technique, representational difference analysis, to identify genes the expressions of which are aberrantly increased in invasive breast carcinomas as compared with adjacent normal breast tissue from the same individual. ⋯ We then measured GIRK1 mRNA expression in benign breast tissues, primary invasive breast carcinomas, and metastatic breast carcinomas from axillary lymph nodes using quantitative TaqMan reverse transcription-PCR and correlated the results with clinical parameters. We found that GIRK1 overexpression correlated with lymph node metastasis (P < 0.0029), and overexpression was greatest in tumors with more than one positive lymph node. These results indicate that GIRK1 may be useful as a biomarker for lymph node metastasis and possibly a pharmaceutical target.