The impact of altered annexin I protein levels on apoptosis and signal transduction pathways in prostate cancer cells

BACKGROUND: Although reduced expression levels of annexin I (ANX I) protein is a common finding in all stages of prostate cancer a causative relationship between ANX I dysregulation and prostate cancer development has yet to be established. METHODS: Annexin I expression was restored in LNCaP and MDA PCa 2b that normally express low or undetectable levels of ANX I protein. The impact of restoring ANX I expression on cell viability, colony formation in soft agar, apoptosis, and extracellular signal-regulated kinases (ERK), p38, c-Jun N-terminal kinases (JNK) activation was examined. RESULTS: Restoring ANX I expression reduced cell viability, colony formation, in addition to inducing apoptosis. The proliferative response of epidermal growth factor was blocked by restoring ANX I expression. Furthermore, increasing basal and induced levels of phosphorylated p38 and JNK were observed in prostate cancer cells following restoration of ANX I expression. CONCLUSIONS: Annexin I may have tumor suppressor functions in prostate cancer. The pro-apoptotic effect of ANX I involves the activation of p38 and JNK, which appears to shift the balance of signal transduction away from proliferation and toward apoptosis.     

FOXN2在前列腺癌组织的表达及对前列腺癌细胞生物学的影响

探讨双头框蛋白N2（FOXN2）在前列腺癌（PCa）组织中的表达以及对PCa细胞生物学的影响。方法 选取宜宾市第二人民医院50例接受手术治疗的PCa患者的标本及癌旁组织,通过RT-qPCR实验和Western blot实验分别检测PCa组织和癌旁组织中的FOXN2 mRNA及蛋白的表达水平,并分析PCa组织中FOXN2与患者临床病理特征的相关性。通过RT-qPCR实验检测正常前列腺细胞RWPE-1、PCa细胞PC-3、DU145、LNCaP中FOXN2 mRNA的表达水平。选取PC-3细胞为研究对象,分为FOXN2过表达组、空载体对照组以及对照组,分别通过MTT实验、流式细胞实验、Transwell实验以及Western blot实验检测各组细胞增殖、凋亡、迁移和侵袭情况以及相关蛋白Bax、CyclinD1、MMP-2的表达量。结果 与癌旁组织相比,FOXN2的mRNA和蛋白表达水平显著降低（P<0.05）,与TCGA数据库中结果一致。FOXN2低表达与PCa患者淋巴转移、TNM分期以及Gleason评分有关（P=0.003、0.005、0.002）。与人正常前列腺细胞RWPE-1相比,FOXN2在PCa细胞PC-3、DU145、LNCaP中均呈现低表达（P<0.05）,其中PC-3细胞中表达量最低。与对照组和空载体对照组相比,FOXN2过表达组的PC-3细胞在作用24 、48 、72 h后增殖能力显著下降（F=290.400、57.735、113.014,P<0.05）,CyclinD1蛋白表达水平显著下降（P<0.05）;PC-3细胞的凋亡率显著升高（P<0.05）,Bax蛋白表达水平显著升高（P<0.05）;PC-3细胞的迁移和侵袭能力显著下降（P<0.05）,MMP-2蛋白表达水平显著下降（P<0.05）。结论 FOXN2在PCa组织及细胞中低表达,过表达FOXN2可抑制PCa细胞的增殖、迁移和侵袭,并促进细胞凋亡。     

Two mutations identified in the androgen receptor of the new human prostate cancer cell line MDA PCa 2a

PURPOSE: We have characterized the androgen receptor (AR) in a new human prostate cancer cell line, MDA PCa 2a, that has recently been established from a bone metastasis of a patient whose cancer exhibited androgen-independent growth. MATERIALS AND METHODS: Androgen responsiveness of these cells was assessed by measuring the effect of DHT and R1881 on cell growth and PSA secretion. Scatchard analysis was used to characterize the affinity and abundance of AR protein. Using a PCR based strategy, genomic DNA of the entire coding region of AR gene was sequenced to identify possible mutations. RESULTS: These cells express abundant AR (Nmax = 685 +/- 149 fmol./mg. protein), but the AR binding affinity (Kd) for DHT is only 25 nM, approximately 50-fold lower affinity than the mutated AR in LNCaP prostate cancer cells (Kd = 0.5 nM) or the wildtype AR in MCF-7 breast cancer cells (Kd = 0.4 nM). Two mutations, L701H and T877A, were identified in the ligand binding domain of the AR gene. Compared with LNCaP cells, the new cell line is significantly less responsive to DHT and R1881 as well as to other androgens such as testosterone, androstenedione, and DHEA. Similar to LNCaP cells, the ligand specificity of the AR in MDA PCa 2a cells appears to be relaxed and non-androgens such as progesterone and estradiol act as agonists although with less potency than in LNCaP cells. Interestingly, in the absence of androgens, the new cell line expresses 15-fold higher baseline levels of PSA than LNCaP. CONCLUSIONS: Two mutations were identified in the AR gene of the MDA PCa 2a cell line that are likely responsible for the decreased androgen sensitivity and altered ligand specificity observed in these cells. Thus, this new cell line with partial androgen responsiveness and PSA expression can serve as a functionally relevant model system of bone metastatic prostate cancer, and can be used to investigate the role of AR mutations in prostate cancer and its progression to androgen independence.     

Differential retention of alpha-vitamin E is correlated with its transporter gene expression and growth inhibition efficacy in prostate cancer cells

BACKGROUND: Epidemiological studies showed Vit E has protective effects against prostate cancer (PCa). Interestingly, different prostate cancer cells have different sensitivity to alpha-Vit E or VES treatment. The goal of this study is to determine whether cellular Vit E bioavailability and its transport proteins are important contributing factors. METHODS: alpha-Vit E and its ester form, VES, were used to treat prostate cancer LNCaP, PC3, and DU145 cells, and their growth rates were determined by MTT assay. Cellular levels of Vit E were quantified using HPLC as the index of bioavailability. The expression levels of Vit E transport proteins were determined by real-time PCR. RESULTS: Among these PCa cells, only LNCaP cells were sensitive to 20 microM alpha-Vit E treatment, while both LNCaP and PC3 cells were sensitive to 20 microM VES treatment. Coordinately, cellular levels of alpha-Vit E and VES positively correlated to their inhibitory effects. Further study found expression levels of Vit E transport proteins, including tocopherol associated protein (TAP), scavenger receptor class B type I (SR-BI), alpha-tocopherol transfer protein (TTP), and ATP binding cassette transporter A1 (ABCA1), were different in various PCa cells, which may contribute to cellular Vit E bioavailability. This notion is further supported by the findings that overexpression or knockdown of TTP could coordinately alter cellular alpha-Vit E levels in PCa cells. CONCLUSION: Antiproliferative efficacy of alpha-Vit E is correlated with its cellular bioavailability in PCa cells. Modulating the expression of the efflux or influx transporters could sensitize the growth inhibition efficacy of Vit E in prostate cancer cells.     

硼替佐米增强前列腺癌细胞对NK细胞介导细胞杀伤作用的敏感性

目的:探讨硼替佐米是否能够增强前列腺癌细胞对NK细胞介导杀伤作用的敏感性,以及是否在不同类型的人前列腺癌细胞系中有相似的作用。方法:以激素依赖性的前列腺癌细胞株LNCaP和激素非依赖性的前列腺癌细胞株DU145为模型,不同浓度(0、5、10、15、20、25nmol/L)硼替佐米处理细胞后,CCK-8法检测肿瘤细胞的增殖,Annexin V/PI法检测细胞凋亡率。结果:15、20、25nmol/L硼替佐米处理DU145细胞48、72h后,各处理组细胞的增殖率分别为(82.79±2.04)%、(73.59±2.95)%、(74.16±6.16)%和(71.24±5.30)%、(51.20±2.91)%、(38.02±2.67)%,同样处理LNCaP细胞后,各处理组细胞的增殖率分别为(77.04±7.74)%、(42.61±6.62)%、(23.85±6.04)%和(36.45±7.02)%、(14.94±5.76)%、(11.65±5.87)%。与对照组相比,硼替佐米强烈抑制两种细胞系的增殖(P0.05)。15、20、25nmol/L硼替佐米处理DU145细胞24h后,DU145细胞的凋亡率分别为(14.41±1.32)%、(16.13±1.55)%、(14.48±1.42)%,而在LNCaP细胞,20、25nmol/L硼替佐米处理24h后,凋亡率为(12.77±1.28)%和(14.84±1.65)%,与对照组相比有统计学差异(P0.05),DU145细胞对硼替佐米诱导的凋亡作用较LNCaP细胞更加敏感。但是,在短期分析中硼替佐米不能致敏两种细胞系对NK细胞介导的杀伤作用。在长效分析中,用硼替佐米处理肿瘤细胞后,20nmol/L硼替佐米+NK组诱导的DU145细胞和LNCaP细胞凋亡率分别为(41.83±5.06)%和(30.31±3.62)%,较单独应用硼替佐米或者NK细胞更高(P0.05)。结论:硼替佐米能够应用于致敏前列腺癌细胞对NK细胞介导的杀伤作用的敏感性,提高当前前列腺癌的治疗水平。而且此治疗策略对雄激素非依赖性的前列腺癌患者更有效。     

Targeting of tumor cells expressing the prostate stem cell antigen (PSCA) using genetically engineered T-cells

BACKGROUND: Curative therapeutic options for minimal residual disease or advanced tumor stages in prostate cancer (PCa) are still missing. Adoptive transfer of cytotoxic T-cells that have been polyclonally rendered tumor-specific by genetic engineering appears to be a promising immunotherapeutic strategy. Among the numerous prostate tissue/tumor antigens identified during the last years, the "prostate stem cell antigen" (PSCA) is an attractive immunotherapeutic target. It is broadly expressed on the surface of primary PCa cells as well as on PCa metastases. METHODS: To generate a chimeric T-cell receptor (TCR) recognizing PSCA, a monoclonal anti-PSCA antibody was raised and a single-chain fragment (scFv) was prepared. The resulting anti-PSCA scFv 7F5 was fused to the beta2 constant region derived from the beta-chain of a TCR and to the CD3zeta-signaling domain. RESULTS: The chimeric alpha-PSCA-beta2/CD3zeta-TCR, expressed in Jurkat cells, was phosphorylated in the ITAMs of the CD3-zeta chain upon cross-linking by insolublized PSCA. When transduced into a mouse cytotoxic T-cell line, the chimeric receptor specifically activated cytotoxicity against PSCA-positive tumor cells. CONCLUSIONS: We developed a functional chimeric TCR against PSCA for treatment of PCa. The chimeric alpha-PSCA-beta2/CD3zeta-TCR might now be used for arming human cytotoxic T-cells for further studies towards a clinical treatment of PCa.     

Regulation of Bcl-2 during androgen-unresponsive progression of prostate cancer

The progression of prostate cancer from androgen-responsive to an androgen-unresponsive state remains the greatest obstacle in the treatment of this disease. Androgen-unresponsive prostate cancer is highly resistant to chemotherapy and radiation treatment that kill cells by the induction of apoptosis. Elucidating the molecular mechanisms of apoptosis regulation in prostate cancer can be useful in the development of new strategies for effective therapy of androgen-unresponsive cancer. We analyzed the Bcl-2 family of apoptosis regulators using various passages of the LNCaP prostate cancer cell line, which serve as an in vitro model for the progression of prostate cancer from androgen-responsive to androgen-unresponsive. In our model, progressively higher passages of LNCaP cells represent the progression to androgen-unresponsiveness. We examined the basal mRNA expression of the Bcl-2 family of apoptosis regulators. Under normal growth conditions, both androgen-responsive and androgen-unresponsive LNCaP cells express the Bcl-2 family of genes at similar levels. Western blot analysis showed the presence of Bcl-2 protein in androgen-responsive cells but not in androgen-unresponsive cells. Both androgen-responsive and androgen-unresponsive cells expressed Bax protein at similar levels. When exposed to oxidative stress, androgen-responsive cells underwent apoptosis but androgen-unresponsive cells exhibited resistance suggesting that the progression to androgen-unresponsiveness was associated with altered regulation of apoptosis. Treatment with paclitaxel or sodium butyrate induced apoptosis in both androgen-responsive and androgen-unresponsive cells suggesting that the apoptotic machinery is still intact in androgen-unresponsive LNCaP cells.     

The role of survivin and Bcl-2 in zinc-induced apoptosis in prostate cancer cells

ObjectivesTo study the effects of zinc treatment on the gene expression levels of survivin and Bcl-2 in prostate cancer cells.Materials and methodsThe effects of zinc exposure on apoptosis were assessed using two human prostate cancer cell lines, LNCaP and PC-3. Zinc-induced apoptosis was measured by Annexin V staining. The direct effect of zinc on the expression levels of zinc transporters (ZnT-1 and ZnT-4) and apoptosis-related genes (Bax, Bcl-2, and survivin) was determined by RT-PCR analysis.ResultsWhen LNCaP and PC-3 cells were exposed to various concentrations of zinc sulfate for 48 hors, their growth was inhibited in a dose-dependent manner. The levels of zinc in both cell lines treated with zinc sulfate for 24 hours were higher than in untreated cells. Exposure to zinc induced apoptosis and necrosis in LNCaP and PC-3 cells. Apoptosis became more extensive as the treatment time with zinc increased. There was a significant increase in the gene expression levels of ZnT-1 and ZnT-4 in both cell lines treated with zinc sulfate compared with untreated cells. The expression of Bax mRNA was up-regulated, while the expression of Bcl-2 and survivin were decreased in both cell lines following zinc treatment.ConclusionsExposure to zinc sulfate in human prostate cancer cells increased intracellular levels of zinc, which resulted in increased apoptosis. The apoptogenic effect of elevated concentration of zinc could be due either to increased expression of zinc transporters and increased levels of Bax or decreased Bcl-2 and survivin expression.     

Molecular targeting of Bcl-2 overcomes prostate cancer cell adaptation to XIAP gene downregulation

X-linked inhibitor of apoptosis (XIAP) is a suppressor of apoptosis that supports an increased survival and resistance to chemotherapy of human prostate cancer (PCa) cells. Effects of transient (24 h) and chronic (beyond 1 month) downregulation of XIAP in DU145 hormone refractory prostate cancer (HRPC) cells were studied. We found that transient downregulation of XIAP by siRNAs resulted in an increase of apoptosis and a decrease in Bcl-2 levels and sensitized PCa cells to cisplatin. XIAP downregulation by shRNA vector stable transfection led to upregulation of Bcl-2 protein. Our results identify the adaptability of PCa cells to chronic loss of XIAP in part through upregulation of Bcl-2 and indicate that multitargeting approach is the most effective application in the chemotherapy of human HRPC.     

Androgen receptor down-regulation in prostate cancer with phosphorodiamidate morpholino antisense oligomers

PURPOSE: Androgen receptor (AR) has a pivotal role in the growth and proliferation of prostate cancer (PCa). Even in advanced stages of PCa AR continues to be expressed and appears to be functional. Since the mechanisms of AR activation in androgen independent PCa have yet to be clearly defined, the decrease in AR protein by antisense compounds is an attractive therapeutic option. In this study we evaluated a novel antisense phosphorodiamidate morpholino oligomer (PMO) targeting the translational start site of AR mRNA in vitro and in vivo in a PCa xenograft and murine prostate. MATERIALS AND METHODS: AR antisense PMOs targeting the AR initiation AUG were tested in vitro and in LNCaP cells, and in vivo in LAPC-4 xenografts and normal mouse prostate. Effects on AR protein and PSA expression were assessed. RESULTS: AR antisense PMOs specifically down-regulated AR protein levels in a plasmid based screening system and also decreased endogenous AR levels in androgen responsive LNCaP cells in culture compared to control nonspecific PMOs. Pretreatment and posttreatment biopsies in the LAPC-4 xenograft model demonstrated that the antisense AR PMO administered intraperitoneally specifically decreased AR protein levels and serum PSA. Analysis of tissue distribution of the AR PMO by high performance liquid chromatography based methodology showed significant PMO levels in tumor tissue and mouse prostate, and there was a dose dependent decrease in AR protein levels in murine AR antisense PMO treated mouse prostates. CONCLUSIONS: An AR antisense PMO with unique chemical properties administered once daily can decrease AR protein levels and PSA in vivo. The reduction of AR protein with an antisense PMO may be an effective method of interfering with AR mediated growth in advanced human PCa.     

Cyclooxygenase-2 promotes prostate cancer progression

BACKGROUND: Cyclooxygenase (COX) -2, an inducible isoform of COX, has been observed to be expressed in prostate cancer. Several studies have reported that COX-2 overexpression is associated with carcinogenesis, cell growth, angiogenesis, apoptosis, and invasiveness in a variety of tumor types. METHODS: To investigate the function of COX-2 in prostate cancer directly, we stably transfected human full-length COX-2 cDNA into LNCaP cells (LNCaP-COX-2), which express low levels of endogenous COX-2. RESULTS: The level of COX-2 mRNA and protein and the COX activity in COX-2 LNCaP-COX-2 cells was significantly increased compared with parent and control-transfected cells. Overexpression of COX-2 increased both proliferation in vitro and tumor growth rate in vivo. However, the pro-tumor effect was neither associated with changes of androgen receptor (AR) expression level nor AR activity. Furthermore, addition of the major metabolites of COX-2-mediated arachidonic acid metabolism did not alter the proliferation of LNCaP-COX-2 cells in vitro. LNCaP-COX-2 cells had increased secretion of vascular endothelial growth factor (VEGF) protein, suggesting that angiogenesis induced by COX-2 stimulates tumor growth in vivo. CONCLUSION: These data demonstrate that COX-2 contributes to prostate cancer progression and suggest that it mediates this effect, in part, through increased VEGF.     

Gene expression in prostate cancer cells treated with the dual 5 alpha-reductase inhibitor dutasteride

We sought preclinical data on the cellular and molecular effects of dutasteride in androgen-responsive, human prostate cancer (PCa) cells to better understand the mechanisms of action of 5 alpha-reductase inhibition in these cells. We used the human prostate cancer cell line LNCaP, which exhibits most features of PCa cells including androgen responsiveness. Our findings show that dutasteride kills PCa cells in vitro; it dramatically reduced viability and proliferation and disrupted genes and cellular pathways involved in metabolic, cell cycle, and apoptotic responses besides those expected in androgen-signaling pathways. Microchip gene array expression analysis revealed activation of genes in the FasL/tumor necrosis factor alpha (TNF-alpha) apoptotic and cell-survival pathways, correlating with the growth and survival effects in the LNCaP cells. Real-time polymerase chain reaction confirmed expression level changes seen by microarray analysis of candidate genes such as PLA2G2A, CDK8, CASP7, MDK, and NKX3.1. Collectively, our findings delineate the cellular and molecular effects of dutasteride in androgen-responsive PCa cells in vitro and may lead to its better therapeutic and chemopreventive use in PCa.     

High expression of PSM-E correlated with tumor grade in prostate cancer: a new alternatively spliced variant of prostate-specific membrane antigen

BACKGROUND: Prostate-specific membrane antigen (PSMA) overexpressed in prostate cancer (PCa) has been targeted for therapy and diagnosis of PCa. In the current study, PSMA cDNA was cloned from PCa tissue by RT-PCR. After sequencing, a new spliced variant of PSMA (PSM-E) was discovered and its specificity in PCa was evaluated. METHODS: PSM-E and PSMA mRNA were measured in LNCaP, PC-3 and prostate or nonprostatic malignancies. Following transfection of PC-3 with PSM-E cDNA in the pcDNA3.0 vector, PSM-E expression was measured by immunofluorescence and Western-blot. PSM-E and PSMA mRNA levels were quantified by a real-time PCR assay in normal prostate (n = 7), benign prostatic hyperplasia (BPH) (n = 22) and PCa (n = 41). The correlation between their levels and tumor grade was analyzed. RESULTS: PSM-E cDNA is identical to PSMA except for a 97-nucleotide region and a 93-nucleotide region. PSM-E and PSMA mRNA were detected in PCa and LNCaP, not in PC-3; PSMA could be detected in some nonprostatic tumors whereas PSM-E not. The expression of PSM-E protein was detected in transfected cells. Significant difference of PSM-E mRNA levels was observed among normal prostate, BPH and PCa (P < 0.001), and PSM-E levels increased with increasing Gleason score (r = 0.514, P < 0.001). PSMA mRNA levels were higher in BPH and PCa than in normal prostate (P < 0.001), but no difference between BPH and PCa, no significant correlation was observed between PSMA levels and Gleason score (r = 0.229, P = 0.057). CONCLUSIONS: PSM-E may be a potential prognostic indicator for PCa progression and may be a new target antigen for therapy of PCa.     

Expression of CCL5 (RANTES) and CCR5 in prostate cancer

BACKGROUND: Expression of the inflammatory chemokine CCL5 (RANTES) by tumor cells is thought to correlate with the progression of several cancers. CCL5 was shown to induce breast cancer cell migration, mediated by the receptor CCR5. A CCR5 antagonist was demonstrated to inhibit experimental breast tumor growth. Recently, CCL5 and CCR5 mRNA expression was reported in prostate cancer (PCa) tissues. Herein, we characterized CCL5 and CCR5 expression in cultures of PCa cells and explored possible functions of CCL5 in PCa progression. METHODS: Quantitative RT-PCR, ELISA, and immunohistochemical staining were performed to examine CCL5 expression in prostate cell lines. CCR5 expression was measured by flow cytometry. Proliferation and invasion assays were performed to determine potential functions of CCL5 and CCR5 in PCa. RESULTS: Expression of CCL5 mRNA and protein was found in human PCa cell lines (PC-3; DU-145; LNCaP) and primary prostate adenocarcinoma cells. CCL5 and CCR5 were also detected in human PCa tissues. CCR5 expression was demonstrated on the cell surface of PCa cells, as well as in intracellular pools. Incubation with CCL5 (10-100 ng/ml) induced PCa cell proliferation, and the CCR5 antagonist TAK-779 inhibited CCL5-induced proliferation. CCL5 was found to stimulate PCa cell invasion, and TAK-779 blocked the effects of CCL5. CONCLUSIONS: In light of evidence that inflammation influences the pathogenesis of PCa, these results suggest that inflammatory chemokines, such as CCL5, expressed by prostate cells may act directly on the growth and survival of PCa cells. Chemokine receptor antagonists may thus block autocrine mechanisms of PCa progression.     

Silencing of pi-class glutathione S-transferase in MDA PCa 2a and MDA PCa 2b cells

BACKGROUND: Loss of expression of the glutathione S-transferase-pi (GSTP1) is the most common genetic alteration described in human prostate cancer, occurring in virtually all tumors regardless of grade or stage. Of the available human prostate cancer cell lines, only LNCaP mirrors this phenotype. We investigated whether the prostate cancer cell lines MDA PCa 2a and MDA PCa 2b share this phenotype. METHODS: GSTP1 protein and mRNA levels were assessed in the MDA PCa 2a and MDA PCa 2b cell lines by Western and Northern blot. DNA methylation was evaluated by Southern blot analysis of genomic DNA digested with the methylation-sensitive restriction enzymes BssHII, NotI, and SacII. Re-expression of GSTP1 was determined by RT-PCR following treatment with 5-azacytidine, a DNA methyltransferase inhibitor, and/or the histone deacetylase inhibitor trichostatin A (TSA). RESULTS: Like all human prostatic carcinomas in vivo, both the MDA PCa 2a and 2b cell lines lack protein and mRNA expression of GSTP1. This lack of expression is associated with methylation in the GSTP1 gene promoter. Treatment with the methyltransferase inhibitor 5-azacytidine resulted in re-expression of GSTP1. By itself, TSA did not result in re-expression of GSTP1, nor did it augment expression induced by 5-azacytidine. CONCLUSIONS: MDA PCa 2a and 2b appear to be useful models of human prostatic carcinoma in that they lack expression of GSTP1 due to gene silencing via promoter methylation. Inhibition of histone acetylation does not appear to affect GSTP1 expression.     

Increased expression and differential phosphorylation of stathmin may promote prostate cancer progression

BACKGROUND: Proteins which regulate normal development may promote tumorigenesis, tumor progression, or metastasis through dysregulation of these functions. We postulate that proteins, which regulate prostate growth also promote prostate cancer (PCa) progression. METHODS: Two Dimensional Gel Electrophoresis was utilized to compare patterns of protein expression in 12T-7f prostates (LPB-Tag mouse model for PCa) during tumor development and progression with those of normal developing and adult wild type CD-1 prostates. Stathmin expression and phosphorylation patterns were analyzed in mouse and human PCa cell lines as well as in human PCa tissue arrays. RESULTS: Stathmin was identified by two-dimensional gel electrophoresis and mass spectrometry. Stathmin levels increase early during normal mouse prostate development and again during prostate tumor development and progression. In human prostate adenocarcinoma, stathmin increases in Gleason pattern 5. Further, stathmin is differentially phosphorylated in androgen-dependent LNCaP cells compared to androgen-independent PC-3 and DU145 cells. This differential phosphorylation is modulated by androgen and anti-androgen treatment. CONCLUSION: Stathmin expression is highest when the prostate is undergoing morphogenesis or tumorigenesis and these processes may be regulated through differential phosphorylation. Furthermore, modulation of stathmin phosphorylation may correlate with the development of androgen-independent PCa.