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Biomedical subjects

Michael B Cohen

Publications and source records attributed to Michael B Cohen.

At least 19 recordsLinked to original sources
PubMed2003

Cooperation of two mutant p53 alleles contributes to Fas resistance of prostate carcinoma cells.

Both inactivation of p53 function and loss of sensitivity to Fas contribute to a malignant phenotype and frequently occur during tumor progression. Although in the majority of cases only one of the p53 alleles is mutated, some tumors acquire mutations in both alleles of the p53 gene. To determine the biological significance of this phenomenon, we analyzed p53 mutants, p53(223Leu) and p53(274Phe), from Fas-resistant prostate carcinoma cell line DU145. Both mutants differed from wild-type p53 in their conformation, transactivation ability, and effect on the growth of p53-deficient cells, with p53(223Leu) being more similar to wild-type p53 than was p53(274Phe). Interestingly, the biological effect of coexpression of the DU145-derived mutants was dramatically different from that of each mutant expressed alone. Whereas neither of the two mutants was found to be dominant-negative against wild-type p53, each neutralized the other's growth-suppressive effects and, in combination, were capable of down-regulating Fas expression and converting Fas-sensitive prostate carcinoma cells PC3 into Fas-resistant ones. These results indicate that two different p53 mutants that are separately rather weak can cooperate to generate p53 protein with anti-Fas function that is likely to provide additional selective advantages to the tumor.

Alleles↗
PubMed2003

Implementation of virtual microscope slides in the annual pathobiology of cancer workshop laboratory.

Virtual slides are digital facsimiles of glass microscope slides that, when viewed with a pan and zoom viewer, can emulate viewing a glass slide with a traditional microscope. Based on successful implementation of virtual slides in medical student histology and pathology courses at the University of Iowa, we developed a plan to evaluate the use of virtual slides in the American Association for Cancer Research's annual Pathobiology of Cancer Workshop. In this Workshop, nonphysician predoctoral students and postdoctoral fellows working in cancer research explore the morphological, clinical, and molecular aspects of human cancer. Over the course of a week, students examine approximately 100 glass slides in microscope laboratories, facilitated by senior cancer investigators. The goal of the present study was to evaluate virtual slides as a teaching modality in these laboratories, not as a replacement for traditional microscopy, but rather in terms of their utility in facilitating student learning as they examine glass slides with a traditional microscope. Evaluation by questionnaire indicated that virtual slides enhanced students' ability to grasp morphological features better than the traditional photomicrographs. The results of this implementation suggest that virtual slide technology may be successfully extended to other educational venues where traditional microscopy and photomicrographs are currently used.

Computer-Assisted Instruction↗
PubMed2003

p53 Is required for 1,25-dihydroxyvitamin D3-induced G0 arrest but is not required for G1 accumulation or apoptosis of LNCaP prostate cancer cells.

1,25-Dihydroxyvitamin D(3) [1,25-(OH)(2)D(3)] is an effective agent for inhibiting the growth of prostate cancer cells including LNCaP and PC-3 cell lines. However, the extent of growth inhibition in these cell lines differs because LNCaP cells are much more responsive than PC-3 cells. Previous studies in LNCaP cells have shown that 1,25-(OH)(2)D(3) treatment results in G(0)/G(1) cell cycle accumulation, loss of Ki67 expression, and induction of apoptosis. One difference between the two cell lines is that PC-3 cells lack functional p53, a protein that plays roles both in cell cycle regulation and induction of apoptosis. In this study, the role of p53 in 1,25-(OH)(2)D(3) action was examined using the p53-negative PC-3 cells and a line of LNCaP cells, called LN-56, in which p53 function was shut off using a dominant negative p53 fragment. We found that treatment with 1,25-(OH)(2)D(3) extensively inhibits growth of LN-56 prostate cancer cells lacking p53, but in contrast to the parental LNCaP cells, the LN-56 cells recover rapidly. Moreover, in prostate cancer cells, the synergism between 1,25-(OH)(2)D(3) and 9-cis retinoic acid appears to be dependent on the presence of functional p53; however, 1,25-(OH)(2)D(3)-mediated induction of G(1) cell cycle accumulation and induction of apoptosis is not.

Alitretinoin↗
PubMed2003

Overexpression of BAD potentiates sensitivity to tumor necrosis factor-related apoptosis-inducing ligand treatment in the prostatic carcinoma cell line LNCaP.

Here we show that LNCaP, which is resistant to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis, becomes sensitive to TRAIL after overexpression of full-length, wild-type BAD (BAD WT). TRAIL induces caspase-dependent cleavage of BAD WT that results in generation of a M(r) 15,000 protein. LNCaP stably expressing truncated BAD (tBAD) and cells expressing mutated BAD at the caspase cleavage site were less sensitive to TRAIL treatment when compared to LNCaP expressing BAD WT. Cytochrome c and Smac/DIABLO release from mitochondria into cytosol was found after TRAIL treatment only in cells overexpressing BAD WT. Furthermore, differences in phosphorylation of serine residues for BAD WT and tBAD were identified. BAD WT was phosphorylated at positions S136 and S155, whereas tBAD was phosphorylated at positions S112, S136, and S155. LNCaP stably expressing BAD mutated at serine 112 to alanine was less sensitive to TRAIL treatment when compared to LNCaP expressing BAD WT. Lastly, recombinant BAD cleaved by caspase-3 is a more potent inducer of cytochrome c and Smac/DIABLO release than BAD WT. In summary, BAD-mediated sensitivity of LNCaP to TRAIL depends on the phosphorylation status of BAD WT and tBAD.

Animals↗
PubMed2002

Fibroblast growth factor 8 isoform B overexpression in prostate epithelium: a new mouse model for prostatic intraepithelial neoplasia.

Fibroblast growth factor 8 isoform b (FGF8b), a mitogenic and transforming polypeptide, was demonstrated to be naturally up-regulated in prostatic premalignant and malignant lesions in men. We generated four independent lines of transgenic mice with targeted overexpression of FGF8b in the prostatic epithelium using an improved rat probasin promoter, ARR(2)PB. Transgene expression in the prostate tissue was readily demonstrated by reverse transcription-PCR and localized to the prostatic epithelium by in situ hybridization. The histopathology of the prostate tissues was followed in different age groups of the various lines but most extensively in one line (line 3), starting from 1 month of age up to 24 months. Prostatic hyperplasia appeared in the lateral and ventral prostates in some animals as early as 2-3 months and in other lobes between 6 and 16 months. Beginning at 5-7 months, dysplasia, akin to what may be considered low-grade prostatic intraepithelial neoplasia (LGPIN) in humans, was detected. During the first 14 months, 100% of animals exhibited multifocal epithelial hyperplasia; 35% also had areas of LGPIN. This profile changed in subsequent months (15-24 months) to a higher incidence of LGPIN (66%) along with high-grade PIN (HGPIN) lesions (51%). Similar to HGPIN, stromal proliferation and appearance of papillary hyperplasia with atypia displayed a delayed pattern. The affected stroma consisted primarily of the smooth muscle cell component. The incidence of chronic inflammation, mostly involving T cells, was higher in the prostate of the transgenic mice relative to controls; however, the presence of a direct correlation between inflammation and hyperplasia or preneoplastic lesions was not identified. These transgenic mice represent a "natural" animal model for investigating the mechanism of development and progression of prostatic diseases, such as prostatic hyperplasia and preneoplastic lesions.

Animals↗
PubMed2002

Prostatic intraepithelial neoplasia in mice with conditional disruption of the retinoid X receptor alpha allele in the prostate epithelium.

Retinoids, which are important regulators of cell growth, differentiation, and apoptosis, have been used in treatment or chemoprevention of multiple cancers including prostate cancer. To elucidate the mechanism of action of retinoids in the context of the prostate, we used the Cre-loxP system to disrupt the retinoid X receptor alpha (RXRalpha) gene specifically in the prostatic epithelium of the mouse. Evidence for tissue-specific gene inactivation was obtained at DNA, RNA, and protein levels. Phenotypic changes in the prostate in the homozygous animals of different age groups ranging from 1 to 15 months were investigated. Developmentally, prostatic ductal branching appeared to be increased from the loss of RXRalpha function. There was also a significant change in the profile of secretory proteins in the RXRalpha mutant prostate relative to littermate controls with intact RXRalpha allele. Histopathologically, homozygous RXRalpha-deficient prostates showed multifocal hyperplasia as early as 4 months of age. Lesions, which could be described as low-grade prostatic intraepithelial neoplasias, were detected after 5 months. Subsequently, beginning at approximately 10 months, high-grade prostatic intraepithelial neoplasias developed in some animals. The incidences of low-grade prostatic intraepithelial neoplasias and high-grade prostatic intraepithelial neoplasias among the animals 10-15 months of age were 62 and 17%, respectively. The heterozygous mutant mice also developed similar prostatic phenotypes but in a delayed manner, implying a role of haploinsufficiency. Together, these results indicated for the first time that a major component of retinoid action in the prostate is mediated by a retinoid receptor, RXRalpha, the inactivation of which in the prostatic epithelium leads to the development of preneoplastic lesions.

Alleles↗
PubMed2002

Bisindolylmaleimide IX facilitates tumor necrosis factor receptor family-mediated cell death and acts as an inhibitor of transcription.

Bisindolylmaleimides (Bis) were originally described as protein kinase C inhibitors. Several studies have shown that Bis potentiate tumor necrosis factor (TNF) receptor family-mediated apoptosis in lymphoid and dendritic cells, but the inhibition of protein kinase C cannot account for these effects (Zhou, T., Song, L., Yang, P., Wang, Z., Lui, D., and Jope, R. S. (1999) Nat. Med. 5, 42-48). We investigated the effect of four Bis derivatives (I, II, VIII, and IX) in human prostatic carcinoma cell lines and found that Bis IX was the most potent inducer of apoptosis under simultaneous treatment with TNF-alpha, agonistic anti-Fas monoclonal antibody, and TNF-related apoptosis-inducing ligand (TRAIL). Bis IX synergistically induced caspase activity in combination with apoptosis-inducing ligands and converted the phenotype of cell lines from apoptosis-resistant to -sensitive. Bis IX induced p53 accumulation in LNCaP (lymph node carcinoma of prostate), which expresses wild-type p53 that was not accompanied by the induction of p53-responsive genes, p21/WAF1, and Mdm2. Moreover, the induction of p21/WAF1 and Mdm2 by doxorubicin was abrogated by simultaneous treatment with Bis IX. These effects apparently result from general inhibition of transcription by Bis IX. We have shown by Northern blot analysis that the transcription activity of the hygromycin gene after transient transfection of pcDNA3.1-Hygro plasmid in 293 and HeLa cells was inhibited by Bis IX in a dose-dependent manner. Moreover, DNA binding activity of Bis IX was prevented by actinomycin D, suggesting that actinomycin D and Bis IX have similar mechanisms of interaction with DNA. In addition, we found that actinomycin D and Bis IX induced caspase activity to the same extent during TRAIL-mediated apoptosis. In summary, these results suggest that Bis IX potentiates TNF receptor family-mediated cell death in part as an inhibitor of transcription.

Apoptosis↗
PubMed2002

Caspase-8 activation is necessary but not sufficient for tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-mediated apoptosis in the prostatic carcinoma cell line LNCaP.

BACKGROUND: The differential sensitivity of tumor cells to TRAIL-induced apoptosis may be mediated by different intracellular inhibitors of apoptosis, and only a few reports have described the pathway(s) that are activated in response to TRAIL in prostate cells. METHODS: LNCaP was transfected with a dominant-negative form of FADD (FADD-DN) and cells were selected in the presence of hygromycin. Cell viability was estimated by calcein assay. Apoptosis was estimated by caspase activation using both fluorogenic substrates and Western blot analysis of activated caspases. To detect cytochrome c release, mitochondria-free cytosol was prepared and Western blot analysis was performed. RESULTS: LNCaP is resistant to TRAIL but TRAIL transiently induces DEVDase activity and activation of caspase-8; caspase-2, -3, -7, and -9 were not activated. Wortmannin, an inhibitor of the PI3K/Akt pathway, converted the phenotype of LNCaP from TRAIL-resistant to -sensitive. In the presence of wortmannin TRAIL induced activation of caspase-2, -3, -7, -8, and -9, as well as dissipation of mitochondrial transmembrane potential and release of cyto-chrome c from mitochondria into the cytosol. In addition, combined TRAIL and wortmannin treatment resulted in cleavage of several proteins: PARP, Akt, p21/WAF1, and MDM2 as well as dephosphorylation of Akt. The proteolysis of p21/WAFI and Akt, which are known survival factors, presumably amplify the apoptotic cascade in LNCaP. Transfection of FADD-DN in LNCaP resulted in inhibition of caspase activation as well as in resistance to combined treatment with TRAIL and wortmannin. CONCLUSIONS: These results suggest that caspase-8 activation is necessary but not sufficient for TRAIL-mediated apoptosis and is presumably blocked downstream of caspase-8 by the PI3K/Akt pathway.

Adaptor Proteins, Signal Transducing↗
PubMed2002

Contribution of death receptor and mitochondrial pathways to Fas-mediated apoptosis in the prostatic carcinoma cell line PC3.

BACKGROUND: Two main pathways of apoptosis in mammalian cells have been described: the death receptor pathway and the mitochondrial pathway. Two different cell types have been identified for Fas-mediated apoptosis, each using almost exclusively one of two different signaling pathways. Human prostatic carcinoma cell line, PC3 is sensitive to Fas-mediated apoptosis, but relation of receptor and mitochondrial pathways is not clear. METHODS: Cell viability was estimated by calcein assay. Apoptosis was determined by preparation of DNA ladder. Expression of Fas-associated death domain-dominant negative (FADD-DN) and Bcl-2, activation of caspases, PARP, DFF45, Bid cleavage, and cytochrome c release were assessed using Western blotting techniques. [(35)S] Methionine-labeled caspase-3 was transcribed in vitro and translated using the TNT kit (Promega). A vector containing caspase-3 was prepared by the ligation of EcoR I/BamHI flanked PCR fragment of full size caspase-3 cDNA into pBlusckript II SK(+/-) (Stratagen). RESULTS: Overexpression of both FADD-DN and Bcl-2 genes prevent Fas-mediated apoptosis in PC3. As predicted, overexpression of FADD-DN prevented activation of caspase-8 and Bid cleavage and attenuated the release of cytochrome c and activation of caspases -2, -7, and -9. Bcl-2 overexpression did not affect caspase-8 activation and cleavage of Bid but blocked the release of cytochrome c and activation of mitochondria localized caspases -2, -7, and-9. Overexpression of FADD-DN and Bcl-2 affected the activation of caspase-3 and PARP cleavage differently: FADD-DN attenuated the activation of caspase-3 and PARP cleavage whereas Bcl-2 overexpression prevented caspase-3 activation and completely blocked cleavage of PARP. CONCLUSIONS: These data suggest that activation of caspase-8 is necessary but not sufficient to complete Fas-mediated apoptosis in PC3 cells without activation of the mitochondrial pathway. In addition, caspase-3 activation after Fas-receptor ligation involves two steps and is dependent on mitochondrial activation.

Apoptosis↗
PubMed2002

Prostatic tumor cell plasticity involves cooperative interactions of distinct phenotypic subpopulations: role in vasculogenic mimicry.

BACKGROUND: Tumor cell plasticity represents a significant clinical challenge in that the fate and function of tumor cells can be elusive until a tumor mass is evident. A remarkable example of plasticity is tumor cell vasculogenic mimicry, recently described in aggressive uveal and cutaneous melanoma, in addition to ovarian carcinoma, whereby tumor cells express endothelial-associated genes and form de novo vasculogenic-like networks in three-dimensional (3-D) culture. In the current investigation, we examined whether there is evidence for vasculogenic mimicry in heterogeneous prostatic neoplasms. METHODS: Dunning rat and human prostate cancer cell lines (comprised of epithelial- and fibroblastic-like tumor subpopulations) were tested for their ability to express selected endothelial-associated genes, laminin, the alpha6beta1 laminin-binding integrin, and for their potential to form perfusable tubular networks in 3-D culture. Simultaneous morphological analysis of tumor-lined channels in rat and human tumors was also performed. RESULTS: Green fluorescent protein labeling of prostatic clonal subpopulations revealed unique cooperative interactions of epithelial- and fibroblastic-like tumor cells in the formation of perfusable vasculogenic-like networks. Furthermore, while these cell lines were shown to express various vascular markers, prostatic tumor cell-lined channels were also detected in vivo in high grade tumors, and occurred in some cases in close proximity to conventional endothelial-lined vasculature. CONCLUSIONS: A multidisciplinary approach to assess vasculogenic mimicry by prostatic tumor cells has revealed supportive evidence that it occurs in invasive, heterogeneous prostate cancer cell lines, and circumstantially in aggressive rat and human tumors. These results reflect the plasticity of aggressive prostatic tumor cells and may provide new prognostic markers for clinical diagnosis and new therapeutic intervention strategies.

Animals↗
PubMed2002

Nondestructive near-infrared spectroscopic measurement of multiple analytes in undiluted samples of serum-based cell culture media.

An adaptive calibration procedure is used to build selective multivariate calibration models for the measurement of glucose, lactate, glutamine, and ammonia in undiluted serum-based cell culture media. This adaptive procedure removes metabolism-induced covariance between these analytes in a series of calibration samples collected during the cultivation of PC-3 human prostate cancer cells. Partial least-squares calibration models are generated from single-beam near-infrared (NIR) spectra collected over the 4800- to 4200-cm(-1) combination spectral range. Calibration models were generated with both the full spectral range and optimized spectral ranges. In both cases, the number of model factors was optimized and model validity was determined by comparing analyte concentrations predicted from a series of independent and unaltered samples that were obtained during a subsequent cultivation of the PC-3 cells. Similar analytical performance was achieved with fewer model factors when the optimized spectral range was used. The lowest standard errors of prediction were 0.82, 0.94, 0.55, and 0.76 mM for glucose, lactate, glutamine, and ammonia, respectively. Different spectral ranges were optimal for each analyte and the optimized spectral range coincided with the distinguishing spectral features of the analyte. The results of this study demonstrate that NIR spectroscopy can be used effectively in the off-line measurement of important nutrients (glucose and glutamine) and byproducts (lactate and ammonia) in a serum-based animal cell culture medium.

Algorithms↗
PubMed2002

Expression of prostate specific antigen (PSA) is negatively regulated by p53.

Although prostate-specific antigen (PSA) is considered a uniquely important tumor marker and is broadly used for early detection of prostate cancer, the molecular mechanisms underlying its elevated expression in tumors have been unknown. By using cDNA microarray gene expression profiling, we found a fourfold increase in the PSA mRNA level in prostatic carcinoma cell line LNCaP, in which the p53 pathway was suppressed by a dominant negative p53 mutant. Consistently, p53 suppression caused a 4-8-fold increase in secretion of PSA protein in culture medium, suggesting that PSA gene expression is under negative control of p53. While wild type p53 strongly repressed, dominant negative p53 mutants stimulated PSA promoter-driven transcription and secretion of PSA in transient transfection experiments. The inhibitory effect of wild type p53 was undetectable in the presence of trichostatin A, suggesting the involvement of histone deacetylation in negative regulation of PSA promoter activity. Thus, PSA is likely to be a tissue specific indicator of transformation-associated p53 suppression in prostate cells. This finding provides a plausible explanation for a frequent increase of PSA levels in advanced prostate cancer.

Acetylation↗
PubMed2002

Cytologic diagnosis of adenocarcinoma in biliary and pancreatic duct brushings.

Biliary and pancreatic duct brush specimens are relatively uncommon specimens seen by pathologists. Not only can the findings of malignancy be subtle, the implications of a malignant diagnosis can be significant. This review focuses on cholangiocarcinoma and pancreatic ductal adenocarcinoma sampled by endoscopic brush cytology, with an emphasis on diagnostic criteria for adenocarcinoma. In addition, assessment of specimen adequacy, utilization of liquid-based preparations, molecular diagnosis, and timing of liver transplantation in patients with primary sclerosing cholangitis are also briefly discussed.

Carcinoma, Pancreatic Ductal↗
PubMed2002

Improving Pap test turnaround time using external benchmark data and engineering process improvement tools.

Turnaround time for Papanicolaou (Pap) tests became an important service quality issue at our institution. We studied Pap test turnaround time using engineering process improvement tools and benchmarked turnaround time against data published as a College of American Pathologists Q-Probes study. An IDEF3 process map revealed the complexity of the Pap test process and the opportunities for process improvement. We used these data and the action-research method to initiate changes in cytopathology laboratory operations with the goal of reducing turnaround time. Before intervention, mean Pap test turnaround time was highly variable; during a 6-month period, monthly means ranged from 2.5 to 10.8 days. A cycle time study conducted over a 2-week period validated these data. After system improvements were implemented, the monthly mean turnaround time decreased and became more consistent, with 11 of 12 months having a mean turnaround time of 3 days or less (range, 1.5-3.9 days). Our study illustrates the value of publishing Q-Probes data for use as external benchmarks and the benefits of using tools from other disciplines to improve laboratory processes.

Benchmarking↗
PubMedDate not supplied

Aberration in the expression of the retinoid receptor, RXRalpha, in prostate cancer.

There is ample evidence for a role for retinoids in the development and maturation of prostatic epithelium. In recent experiments with conditional disruption of a specific retinoid receptor, namely, RXRalpha in the prostatic epithelium of the mouse, we observed that a major component of retinoid action in the prostate is indeed mediated by RXRalpha. The results clearly indicated that the inactivation of RXRalpha in the prostate epithelium leads to the development of preneoplastic lesions (Huang et al. Cancer Res 62: 4812-9, 2002). To determine the relation of this finding to human prostate cancer, we examined the expression of RXRalpha protein in human prostate cancer cell lines by western blotting and prostate cancer specimens by immunohistochemistry. Relative to the "normal" prostate epithelial cells, there was approximately two- to nine-fold decrease in the full-length 54 kD RXRalpha protein in each of the seven different prostate cancer cell lines tested. Similarly, while RXRalpha immunostaining was uniformly strong in the nuclei of most of the benign prostatic epithelial cells of the thirteen adenocarcinoma specimens tested, a highly heterogeneous pattern of expression was detected in the malignant epithelium, with some areas with low or no staining, others with mostly cytoplasmic staining, and some with both nuclear and cytoplasmic immunoreactivity. To evaluate the effect of RXRalpha modulation on the biologic properties of prostate cancer cell lines, we used a lentivirus expression system to overexpress RXRalpha in CWR22R prostate cancer cells that basally expressed a marginal level of the receptor. The sorted RXRalpha-transduced cells were compared to the corresponding vector control cells for proliferative and apoptotic properties. A correlation of reduction of cell growth or increased susceptibility to apoptosis with increases in the level of RXRalpha nuclear receptor was demonstrated. These effects were further enhanced when the cell culture medium was supplemented with a retinoid receptor panagonist, 9-cis retinoic acid. Together, these data support the notion that, like in mouse prostate, loss or reduction of RXRalpha activity might be a critical factor in prostate tumorigenesis in humans.

Alitretinoin↗
PubMedDate not supplied

Bisindolylmaleimide IX Induces Reversible and Time-Dependent Tumor Necrosis Factor Receptor Family-Mediated Caspase Activation and Cell Death.

We have previously shown that Bisindolylmaleimide (Bis) IX is localized in mitochondria but also acts as an inhibitor of transcription and facilitates tumor necrosis factor receptor family-mediated apoptosis. In this study, we found that Bis IX is freely distributed both within cells and extracellular medium and acts as a reversible apoptosis-inducing agent. Bis IX was found to induce time-dependent apoptosis in combination with TNF-a, TRAIL, and anti-Fas Ab. Using human prostatic carcinoma cell lines DU145 and LNCaP that are resistant to treatment with TNF family death-inducing ligands, we have shown that different, albeit still unidentified, inhibitory factors are responsible for the resistance to TRAIL-, Fas-, and TNF-a-mediated apoptosis. Our data also suggest that the turnover of apoptosis suppressor factors is much faster in DU145 compared to LNCaP. Lastly, we have found that Bis IX can override the apoptosis-inhibitory effects of Bcl-2 overexpression. In conclusion, Bis IX could be used as a drug to facilitate apoptosis of cancer cells that are resistant to treatment with death-inducing ligands as well as a valuable tool to discern the factors that mediate resistance to different death-inducing ligands.

Apoptosis↗
PubMedDate not supplied

TRAIL-DISC formation is androgen-dependent in the human prostatic carcinoma cell line LNCaP.

We and others have previously described that the androgen-responsive human prostatic carcinoma cell line LNCaP is resistant to TRAIL and that TRAIL-mediated apoptosis in LNCaP is PI3K/Akt-dependent. In this study, we found that LNCaP remained resistant to treatment with TRAIL after androgen deprivation even in the presence of the PI3K/Akt pathway inhibitor wortmannin. This resistance was determined by failure to form the TRAIL-DISC and by decreased TRAIL-R1 and TRAIL-R2 levels after androgen deprivation; the capacity of TRAIL to induce DISC formation was completely restored in the presence of DHT. TRAIL and wortmannin together accelerated processing of caspase-8 on the DISC and apparently the release of caspase-8 from the DISC into the cytoplasm. Surprisingly, we found that wortmannin decreased the total amount of TRAIL-R1, but not TRAIL-R2, in the cells as well as the amount of TRAIL-R1 precipitated by TRAIL. Our data suggest that TRAIL-DISC formation and sensitivity to TRAIL treatment are androgen-dependent in LNCaP.

Adaptor Proteins, Signal Transducing↗