Invasion Of Human Prostate Cancer Cells Research Articles

Circular RNA cir-ITCH Is a Potential Therapeutic Target for the Treatment of Castration-Resistant Prostate Cancer.

cir-ITCH, a well-known tumor-suppressive circular RNA, plays a critical role in different cancers. However, its expression and functional role in prostate cancer (PCa) are unclear. Herein, we explored the potential mechanism and tumor-inhibiting role of cir-ITCH in PCa. Using reverse transcriptase polymerase chain reaction assay, we analyzed the expression of cir-ITCH in PCa and paired adjacent nontumor tissue samples resected during surgical operation, as well as in two cell lines of human PCa (LNCaP and PC-3) and the immortalized normal prostate epithelial cell line (RWPE-1). Cell viability and migration of PCa cell lines were evaluated using CCK-8 and wound-healing assays. Expression of key proteins of the Wnt/β-catenin and PI3K/AKT/mTOR pathways was detected using western blotting. We found that cir-ITCH expression was typically downregulated in the tissues and cell lines of PCa compared to that in the peritumoral tissue and in RWPE-1 cells, respectively. The results showed that cir-ITCH overexpression significantly inhibits the proliferation, migration, and invasion of human PCa cells and that reciprocal inhibition of expression occurred between cir-ITCH and miR-17. Proteins in the Wnt/β-catenin and PI3K/AKT/mTOR pathways were downregulated by overexpression of cir-ITCH both in androgen receptor-positive LNCaP cells and androgen receptor-negative PC-3 cells. Taken together, these data demonstrated that cir-ITCH plays a tumor-suppressive role in human PCa cells, partly through the Wnt/β-catenin and PI3K/AKT/mTOR pathways. Thus, cir-ITCH may serve as a novel therapeutic target for the treatment of PCa, especially castration-resistant prostate cancer.

Development of a 3D Tissue Culture–Based High-Content Screening Platform That Uses Phenotypic Profiling to Discriminate Selective Inhibitors of Receptor Tyrosine Kinases

3D tissue cultures provide a more physiologically relevant context for the screening of compounds, compared with 2D cell cultures. Cells cultured in 3D hydrogels also show complex phenotypes, increasing the scope for phenotypic profiling. Here we describe a high-content screening platform that uses invasive human prostate cancer cells cultured in 3D in standard 384-well assay plates to study the activity of potential therapeutic small molecules and antibody biologics. Image analysis tools were developed to process 3D image data to measure over 800 phenotypic parameters. Multiparametric analysis was used to evaluate the effect of compounds on tissue morphology. We applied this screening platform to measure the activity and selectivity of inhibitors of the c-Met and epidermal growth factor (EGF) receptor (EGFR) tyrosine kinases in 3D cultured prostate carcinoma cells. c-Met and EGFR activity was quantified based on the phenotypic profiles induced by their respective ligands, hepatocyte growth factor and EGF. The screening method was applied to a novel collection of 80 putative inhibitors of c-Met and EGFR. Compounds were identified that induced phenotypic profiles indicative of selective inhibition of c-Met, EGFR, or bispecific inhibition of both targets. In conclusion, we describe a fully scalable high-content screening platform that uses phenotypic profiling to discriminate selective and nonselective (off-target) inhibitors in a physiologically relevant 3D cell culture setting.

The effects of different concentrations of sevoflurane on proliferation and invasion in humanprostate cancer cells

The effects of different concentrations of sevoflurane on proliferation and invasion in humanprostate cancer cells

Effects of upregulatioon of trophoblast cell-surface antigens 2 on migration, invasion and epithelial-mesenchymaltransition of human prostate cancer cells

Objective To explore the effects of over-expression of trophoblast cell-surface antigens 2(TROP-2)gene on the migration and invasion of human prostate cancer cells and the action mechanism. Methods The TROP-2 gene was cloned into the eukaryotic expression vector pcDNA3. 1, and TROP-2 over-expression of eukaryotic gene expression plasmid was constructed. All PC-3 cells were divided into three groups: the control group(Con-A), empty vector control group(Con-B)and over-expression group TROP-2(pcDNA3. 1-TROP-2).After PC-3 cells in three groups were transfected with phosphate buffer(PBS), vector pcDNA3. 1, or pcDNA3. 1-TROP -2, the protein levels of TROP-2 were determined by Western blotting, respectively.The migration and invasion ability was evaluated by Transwell.The E-Cadherin and N-Cadherin protein expression in PC-3 cells was examined by Western blotting. Results TROP-2 gene eukaryotic expression vector was successfully constructed. The Western blotting showed that the expression levels of TROP-2 protein were greatly increased in PC-3 cancer cells transfected with pcDNA3. 1-TROP -2.The Transwell migration assay revealed that the number of migrating cells in Con-A,Con-B, and pcDNA3. 1-TROP-2 groups was 132. 6±2. 2, 130. 8±1. 8 and 189. 6±2. 6, respectively (P< 0. 01).The Transwell invasion assay indicated that the number of migrating cells in Con-A, Con-B, and pcDNA3. 1-TROP-2 groups was 118. 16±1. 96, 117. 52±1. 85 and 166. 38±1. 65, respectively(P< 0. 01).As Compared with the Con-A group, the E-cadherin protein expression was decreased,and the N-cadherin protein expression was increased in PC-3 cancer cells transfected with pcDNA3. 1-TROP-2. Conclusion TROP-2 overexpression can promote migration and invasion of human prostate cancer cells probably promoting the epithelial-mesenchymal transition. Key words: Trophoblast cell-surface antigens 2; Prostate carcinoma; Invasion; Epithelialmesenchymal transition

Pharmacological methyl group donors block skeletal metastasis in vitro and in vivo.

DNA hypomethylation was previously implicated in metastasis. In the present study, we examined whether methyl supplementation with the universal methyl donor S-adenosylmethionine (SAM) inhibits prostate cancer associated skeletal metastasis. Highly invasive human prostate cancer cells PC-3 and DU-145 were treated with vehicle alone, S-adenosylhomocysteine (SAH) or SAM and their effects on tumour cell proliferation, invasion, migration and colony formation were monitored. For in vivo studies, control (SAH) and SAM-treated PC-3 cells were injected into the tibia of Fox chase SCID mice and skeletal lesions were determined by X-ray and μCT. To understand possible mechanisms involved, we delineated the effect of SAM on the genome-wide methylation profile of PC-3 cells. Treatment with SAM resulted in a dose-dependent inhibition of tumour cell proliferation, invasion, cell migration, colony formation and cell cycle characteristics. Animals injected with 250 μM SAM-treated cells developed significantly smaller skeletal lesions, which were associated with increases in bone volume to tumour volume ratio and connectivity density as well as decreased trabecular spacing. Genome-wide methylation analysis showed differential methylation in several key signalling pathways implicated in prostate cancer including the signal transducer and activator of transcription 3 (STAT3) pathway. A selective STAT3 inhibitor decreased tumour cell invasion, effects which were less pronounced as compared with SAM. These studies provide a possible mechanism for the role of DNA demethylation in the development of skeletal metastasis and a rationale for the use of hypermethylation pharmacological agents to impede the development and progression of skeletal metastasis.

Broccoli bioactives inhibit human prostate cancer cell invasions in vitro (1045.5)

Previous studies have found that various bioactives in broccoli may have anti‐cancer activities, including anti‐invasion ability. We hypothesized that regular consumption of broccoli may inhibit prostate cancer via inhibition of invasion. Thus, the invasive human prostate cancer cell line, DU145, was treated with two broccoli bioactives—sulforaphane and indole‐3‐carbinol. Cells were seeded in matrigel inserts in 24‐well plates containing complete medium as the chemoattractant. Treatments were renewed at the 24th hour. After a total of 48 hours treatment, the matrigel layer was removed, and cells on the bottom membrane were stained and counted. The invasive ability of DU145 was significantly suppressed in a dose‐dependent manner by treatment with sulforaphane at concentrations as low as 3µM. Indole‐3‐carbinol also significantly reduced invasion, but at concentration as low as 0.2µM. In summary, two major bioactives in broccoli show anti‐invasion activity in vitro, at physiologically‐achievable concentrations.

Finasteride Inhibits Human Prostate Cancer Cell Invasion through MMP2 and MMP9 Downregulation

IntroductionThe use of the 5-alpha reductase inhibitors (5-ARIs) finasteride and dutasteride for prostate cancer prevention is still under debate. The FDA recently concluded that the increased prevalence of high-grade tumors among 5-ARI-treated patients must not be neglected, and they decided to disallow the use of 5-ARIs for prostate cancer prevention. This study was conducted to verify the effects of finasteride on prostate cell migration and invasion and the related enzymes/proteins in normal human and tumoral prostatic cell lines.Materials and MethodsRWPE-1, LNCaP, PC3 and DU145 cells were cultivated to 60% confluence and exposed for different periods to either 10 µM or 50 µM finasteride that was diluted in culture medium. The conditioned media were collected and concentrated, and MMP2 and MMP9 activities and TIMP-1 and TIMP-2 protein expression were determined. Cell viability, migration and invasion were analyzed, and the remaining cell extracts were submitted to androgen receptor (AR) detection by western blotting techniques. Experiments were carried out in triplicate.ResultsCell viability was not significantly affected by finasteride exposure. Finasteride significantly downregulated MMP2 and MMP9 activities in RWPE-1 and PC3 cells and MMP2 in DU145 cells. TIMP-2 expression in RWPE-1 cells was upregulated after exposure. The cell invasion of all four tested cell lines was inhibited by exposure to 50 µM of finasteride, and migration inhibition only occurred for RWPE-1 and LNCaP cells. AR was expressed by LNCaP, RWPE-1 and PC3 cells.ConclusionsAlthough the debate on the higher incidence of high-grade prostate cancer among 5-ARI-treated patients remains, our findings indicate that finasteride may attenuate tumor aggressiveness and invasion, which could vary depending on the androgen responsiveness of a patient’s prostate cells.

The Function of Vacuolar ATPase (V-ATPase) a Subunit Isoforms in Invasiveness of MCF10a and MCF10CA1a Human Breast Cancer Cells

The vacuolar H(+) ATPases (V-ATPases) are ATP-driven proton pumps that transport protons across both intracellular and plasma membranes. Previous studies have implicated V-ATPases in the invasiveness of various cancer cell lines. In this study, we evaluated the role of V-ATPases in the invasiveness of two closely matched human breast cancer lines. MCF10a cells are a non-invasive, immortalized breast epithelial cell line, and MCF10CA1a cells are a highly invasive, H-Ras-transformed derivative of MCF10a cells selected for their metastatic potential. Using an in vitro Matrigel assay, MCF10CA1a cells showed a much higher invasion than the parental MCF10a cells. Moreover, this increased invasion was completely sensitive to the specific V-ATPase inhibitor concanamycin. MCF10CA1a cells expressed much higher levels of both a1 and a3 subunit isoforms relative to the parental line. Isoforms of subunit a are responsible for subcellular localization of V-ATPases, with a3 and a4 targeting V-ATPases to the plasma membrane of specialized cells. Knockdown of either a3 alone or a3 and a4 together using isoform-specific siRNAs inhibited invasion by MCF10CA1a cells. Importantly, overexpression of a3 but not the other a subunit isoforms greatly increased the invasiveness of the parental MCF10a cells. Similarly, overexpression of a3 significantly increased expression of V-ATPases at the plasma membrane. These studies suggest that breast tumor cells employ particular a subunit isoforms to target V-ATPases to the plasma membrane, where they function in tumor cell invasion.

Abstract 3861: Downregulation of protein phosphatase 2A promotes prostate cancer progression and metastasis.

Abstract Clinical progression of prostate cancer (PCa) is characterized by a transition from castration-sensitive (CS) to castration-resistant (CR) phenotype. The resulting CR tumors are highly aggressive and metastatic, and thus pose increased risk of morbidity and death to PCa patients. Therefore, identification of novel gene targets associated with CR growth and metastatic behavior remain a priority area in PCa research. Previously, we identified that PPP2CA, which encodes for the α–isoform of catalytic subunit of PP2A (a serine/threonine phosphatase), is downregulated in CRPCa. In additional findings, we reported that PP2A downregulation sustained the growth of PCa cells under steroid–deprived conditions. In the present study, we examined the role of PP2A in malignant behavior of PCa cells using in vitro and in vivo functional assays. Furthermore, we also delineated the underlying molecular mechanisms. Our data demonstrated that downregulation of PPP2CA (in CS LNCaP cells) promoted, whereas its overexpression (in CR C4-2 and PC3 cells) decreased the migration and invasion of human PCa cells. Similarly, we observed a loss of homotypic interactions in PPP2CA-silenced LNCaP cells, while it increased in PPP2CA-overexpressing C4-2 and PC3 cells. These changes were associated with epithelial to mesenchymal transition (EMT) or vice versa in PPP2CA-silenced or overexpressing PCa cells, respectively. When examined in vivo in an orthotopic mouse model, PPP2CA-overexpressing PC3 cells exhibited dramatic decrease in tumorigenesis due to diminished proliferation and enhanced apoptosis as compared to the control cells. Moreover, significant reduction in metastatic incidence was also observed. Mechanistic studies revealed that PPP2CA downregulation increases nuclear accumulation of β-catenin and NF-κB and subsequent activation of transcriptional activity of the responsive gene promoters. We also observed cooperative involvement of both β-catenin and NF-κB in the PPP2CA downregulation-induced EMT and invasiveness of PCa cells. Lastly, our data demonstrated a role of PP2A/Akt axis in enhanced nuclear accumulation of β-catenin and NF-κB through phosphorylation-induced inactivation of Gsk3-β and IkB-α, respectively. Altogether, our data suggest that loss of PPP2CA is associated with PCa progression and metastasis, and restoration of PP2A activity could serve as an effective preventive and/or therapeutic approach against the advanced disease. Citation Format: Arun Bhardwaj, Seema Singh, Sanjeev K. Srivastava, Sumit Arora, Stephen J. Hyde, Richard E. Honkanen, William E. Grizzle, Ajay P. Singh. Downregulation of protein phosphatase 2A promotes prostate cancer progression and metastasis. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3861. doi:10.1158/1538-7445.AM2013-3861

Inhibitors of vacuolar ATPase proton pumps inhibit human prostate cancer cell invasion and prostate-specific antigen expression and secretion.

Vacuolar ATPases (V-ATPases) comprise specialized and ubiquitously distributed pumps that acidify intracellular compartments and energize membranes. To gain new insights into the roles of V-ATPases in prostate cancer (PCa), we studied the effects of inhibiting V-ATPase pumps in androgen-dependent (LNCaP) and androgen-independent (C4-2B) cells of a human PCa progression model. Treatment with nanomolar concentrations of the V-ATPase inhibitors bafilomycin A or concanamycin A reduced the in vitro invasion in both cell types by 80%, regardless that V-ATPase was prominent at the plasma membrane of C4-2B cells and only traces were detected in the low-metastatic LNCaP parental cells. In both cell types, intracellular V-ATPase was excessive and co-localized with prostate-specific antigen (PSA) in the Golgi compartment. V-ATPase inhibitors reversibly excluded PSA from the Golgi and led to the accumulation of largely dispersed PSA-loaded vesicles of lysosomal composition. Inhibition of acridine orange staining and transferrin receptor recycling suggested defective endosomal and lysosomal acidification. The inhibitors, additionally, interfered with the AR-PSA axis under conditions that reduced invasion. Bafilomycin A significantly reduced steady-state and R1881-induced PSA mRNA expression and secretion in the LNCaP cells which are androgen-dependent, but not in the C4-2B cells which are androgen ablation-resistant. In the C4-2B cells, an increased susceptibility to V-ATPase inhibitors was detected after longer treatments, as proliferation was reduced and reversibility of bafilomycin-induced responses impaired. These findings make V-ATPases attractive targets against early and advanced PCa tumors.

Abstract 2000: Curcumin prevents human prostate cancer cell invasion by inhibiting of matriptase activity

Abstract Curcumin has been shown with potent chemopreventive and antitumor effects on prostate cancer. However, the molecular mechanism how curcumin suppresses prostate cancer cell migration and invasion is not well understood. In this study we showed that curcumin could significantly suppress prostate cancer PC3 cell migration and invasion. Moreover, our data also showed that curcumin was able to suppress EGF- or heregulin-stimulated PC-3 cell invasion, as well as androgen-induced LNCaP cell invasion. Curcumin treatment resulted in not only significant reductions on MMP-9 and MMP-2 activities, but also on activated level of matriptase which is a membrane-bound serine protease and has been proposed to play important roles in tumor invasion and malignancy. Matriptase is synthesized as a full length zymogen, which is rapidly stepped into the maturation process, mature form through a cleavage within the SEA domain to from a latent matriptase. Our data further showed that curcumin can inhibit the latent matriptase formation in the maturation process to affect matriptase activity. Furthermore, the reduction of activated matriptase by curcumin was also partly due to curcumin promoting the shedding of activated matriptase into extracellular environment, but not due to curcumin effect on matriptase gene expression. In addition, we established the stable pools of CWR22Rv1 cells with matriptase overexpression and found that expression of matriptase in CWR22Rv1 cells enhanced their invasive ability. With curcumin treatment, the invasive ability induced by matriptase overexpression was significantly suppressed. In summary, the data indicated that curcumin exhibits a suppressive effect on prostate cancer cell invasion, at least in part by down-regulating matriptase activity. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2000. doi:1538-7445.AM2012-2000

FAK/c-Src signaling pathway mediates the expression of cell surface HSP90 in cultured human prostate cancer cells and its association with their invasive capability

To investigate the expression of heat shock protein 90 (HSP90) on the cell surface of highly invasive human prostate cancer cells PC3 and its possible molecular mechanisms of its effect on cell invasion through analyzing FAK/Src signaling pathway. The expression of cell surface HSP90 on PC3 cells was studied by immunofluorescence staining and surface biotinylation assay respectively. A specific HSP90 antibody was used to inhibit the cell surface HSP90. In vitro cell invasion was assessed by modified Boyden chambers. Phosphorylated FAK on tyr 397, 576, 577 and 925, and phosphorylated c-Src on tyr 416 were examined by Western blot assay. The association between FAK and c-Src was analyzed by immunoprecipitation. The effects of FAK knockdown by siRNA or Src kinases inhibitor PP2, with or without anti-HSP90 antibody, on PC3 cell invasion were also evaluated. A pool of HSP90 was detected on the cell surface of PC3 cells. A specific HSP90 antibody significantly retarded tumor cell invasion. Concomitant with this finding, targeting cell surface HSP90 significantly inhibited the phosphorylations of FAK and c-Src, and also the interactions between FAK and c-Src. FAK knockdown or PP2 dramatically suppressed cell invasion, however, anti-HSP90 antibody didn't further inhibit cell invasion. Cell surface HSP90 promotes human prostate cancer cell invasion through a FAK/c-Src signaling, with may be a novel therapeutic target against metastatic tumors.

Cell surface heat shock protein 90 modulates prostate cancer cell adhesion and invasion through the integrin-β1/focal adhesion kinase/c-Src signaling pathway

Heat shock protein (Hsp) 90 is a molecular chaperone that maintains the active conformation and function of numerous client oncoproteins in cancer cells. Hsp90 has also been detected on the plasma membrane of cells, and its expression has been suggested to correlate with metastatic potential. We studied the PC3 cell line, which is a highly invasive human prostate cancer cell line, and confirmed that Hsp90 is present on the cell surface of PC3 cells. Interestingly, cell surface Hsp90 was also specifically localized at the leading edge of migrating cells. By using a specific antibody that inhibited cell surface Hsp90, adhesion and invasion of PC3 cells were significantly suppressed invitro. Concomitantly with these findings, we demonstrated that the inhibition of cell surface Hsp90 not only inhibited the FN-dependent association between FAK, c-Src and integrin β1, but also significantly inhibited the phosphorylation of FAK and c-Src, as well as their downstream targets paxillin and p130Cas. Additionally, the Hsp90 antibody reversed cell invasion stimulated by overexpression of FAK. These data indicate that cell surface Hsp90 is involved in prostate cancer cell invasion through the integrin β1/FAK/c-Src signaling pathway. Our study provides new insights into the mechanisms of cell surface Hsp90 in cancer invasion. These results suggest that molecular targeting of cell surface Hsp90 may therefore be a novel target for the effective treatment of metastatic prostate cancer.

Abstract CN02-04: Phase II study of genistein in men with prostate cancer

Abstract Progression of cells to a metastatic phenotype begins in the primary organ and represents an important chemoprevention target. In preclinical studies, genistein induces reversion of human prostate cancer (PCa) cells to a less metastatic phenotype. In a phase II study, men with localized PCa were randomized between genistein treatment versus not prior to radical prostatectomy. Analysis of prostate epithelial cells within harvested organs revealed that genistein had the following effects: 1) it decreased matrix metalloproteinase 2 (MMP-2) expression; 2) it induced nuclear spreading; a surrogate marker of inhibition of cell detachment; and 3) gene expression profiling demonstrated selective modulation of genes associated with regulation of cell motility in other cell types. By engineering the expression of these genes in cell lines, we demonstrated that they were important regulators of human PCa cell invasion. Genistein increased the expression of genes that suppress invasion and decreased the expression of genes that enhance invasion. Together, this study demonstrates that genistein induces reversion of human prostate cells in man to a less metastatic phenotype. Importantly, this study demonstrates the proof-of-principal concept that the conduct of molecular screens in human chemoprevention trials has the ability to identify the mechanism of action of investigational agents. Citation Information: Cancer Prev Res 2010;3(12 Suppl):CN02-04.

An Anti-Urokinase Plasminogen Activator Receptor Antibody (ATN-658) Blocks Prostate Cancer Invasion, Migration, Growth, and Experimental Skeletal Metastasis In Vitro and In Vivo

Urokinase plasminogen activator receptor (uPAR) is a multidomain protein that plays important roles in the growth, invasion, and metastasis of a number of cancers. In the present study, we examined the effects of administration of a monoclonal anti-uPAR antibody (ATN-658) on prostate cancer progression in vitro and in vivo. We examined the effect of treatment of ATN-658 on human prostate cancer cell invasion, migration, proliferation, and regulation of intracellular signaling pathways. For in vivo studies, PC-3 cells (1 x 106) were inoculated into the right flank of male Balb C nu/nu mice through subcutaneous or through intratibial route (2 x 105) of male Fox Chase severe combined immunodeficient mice to monitor the effect on tumor growth and skeletal metastasis. Treatment with ATN-658 resulted in a significant dose-dependent decrease in PC-3 cell invasion and migration without affecting cell doubling time. Western blot analysis showed that ATN-658 treatment decreased the phosphorylation of serine/threonine protein kinase B (AKT), mitogen-activated protein kinase (MAPK), and focal adhesion kinase (FAK) without affecting AKT, MAPK, and FAK total protein expression. In in vivo studies, ATN-658 caused a significant decrease in tumor volume and a marked reduction in skeletal lesions as determined by Faxitron x-ray and micro-computed tomography. Immunohistochemical analysis of subcutaneous and tibial tumors showed a marked decrease in the levels of expression of pAKT, pMAPK, and pFAK, consistent with the in vitro observations. Results from these studies provide compelling evidence for the continued development of ATN-658 as a potential therapeutic agent for the treatment of prostate and other cancers expressing uPAR.

SKI-606 (Bosutinib) Blocks Prostate Cancer Invasion, Growth, and Metastasis In vitro and In vivo through Regulation of Genes Involved in Cancer Growth and Skeletal Metastasis

In the current study, we have examined the efficacy of a Src/Abl kinase inhibitor SKI-606 (Bosutinib) for its effect on prostate cancer growth and skeletal metastasis. Treatment of highly invasive human prostate cancer cells PC-3 and DU-145 with different doses of SKI-606 decreased Src activation, cell proliferation, migration, and invasion as determined by Matrigel Boyden chamber invasion assay. For in vivo studies, PC-3 cells were inoculated through s.c. or i.t. route into male BALB/c nu/nu or Fox Chase severe combined immunodeficient mice, respectively. Experimental animals treated with SKI-606 developed tumors of a significantly smaller volume and a significant decrease (50%) in experimental skeletal lesion area. A marked increase (32%) in bone volume to tumor volume ratio was also seen by micro-computed tomography analysis of tibias from control and experimental groups of animals. Western blot analysis showed the ability of SKI-606 to significantly decrease the phosphorylation of signaling molecules (AKT, mitogen-activated protein kinase, focal adhesion kinase) and the expression of tumor progression-associated genes uPAR, MMP-2, MMP-9, N-cadherin, fibronectin, BMP-2 (bone morphogenetic protein 2), BMP-6 (bone morphogenetic protein 6), IL-8 (interleukin 8), and TGF-beta (transforming growth factor beta) in prostate cancer cells. SKI-606 is currently in clinical trials for breast cancer and chronic myelogenous leukemia. Results from these studies provide convincing evidence for evaluating its efficacy in prostate cancer patients.

Increased potency of the PHSCN dendrimer as an inhibitor of human prostate cancer cell invasion, extravasation, and lung colony formation

Activated alpha5beta1 integrin occurs specifically on tumor cells and on endothelial cells of tumor-associated vasculature, and plays a key role in invasion and metastasis. The PHSCN peptide (Ac-PHSCN-NH(2)) preferentially binds activated alpha5beta1, to block invasion in vitro, and inhibit growth, metastasis and tumor recurrence in preclinical models of prostate cancer. In Phase I clinical trial, systemic Ac-PHSCN-NH(2) monotherapy was well tolerated, and metastatic disease progression was prevented for 4-14 months in one-third of treated patients. We have developed a significantly more potent derivative, the PHSCN-polylysine dendrimer (Ac-PHSCNGGK-MAP). Using in vitro invasion assays with naturally serum-free basement membranes, we observed that the PHSCN dendrimer was 130- to 1900-fold more potent than the PHSCN peptide at blocking alpha5beta1-mediated invasion by DU 145 and PC-3 human prostate cancer cells, whether invasion was induced by serum, or by the Ac-PHSRN-NH(2) peptide, under serum-free conditions. The PHSCN dendrimer was also approximately 800 times more effective than PHSCN peptide at preventing DU 145 and PC-3 extravasation in the lungs of athymic mice. Chou-Talalay analysis suggested that inhibition of both invasion in vitro and extravasation in vivo by the PHSCN dendrimer are highly synergistic. We found that many extravasated DU 145 and PC-3 cells go onto develop into metastatic colonies, and that a single pretreatment with the PHSCN dendrimer was 100-fold more affective than the PHSCN peptide at reducing lung colony formation. Since many patients newly diagnosed with prostate cancer already have locally advanced or metastatic disease, the availability of a well-tolerated, nontoxic systemic therapy, like the PHSCN dendrimer, which prevents metastatic progression by inhibiting invasion, could be very beneficial.

Targeted knockdown of Notch1 inhibits invasion of human prostate cancer cells concomitant with inhibition of matrix metalloproteinase-9 and urokinase plasminogen activator.

Notch, a type 1 transmembrane protein, plays a key role in the development of many tissues and organ types. Aberrant Notch signaling, found in a wide variety of human cancers, contributes to tumor development. Because Notch1 was found to be overexpressed in prostate cancer (PCa) cells and human PCa tissue, we therefore tested our hypothesis that overexpression of Notch1 in PCa promotes tumor invasion. Notch1 expression was evaluated in human PCa cells and human PCa tissues. PCa cells were transiently transfected with Notch1-specific small interfering RNAs in concentrations ranging from 30 to 120 nmol/L and subsequently evaluated for effects on invasion and expression analysis for molecules involved in invasion. Small interfering RNA-mediated knockdown of Notch1 in PC3 and 22Rnu1 PCa cells dramatically decreased their invasion. Focused cDNA array revealed that Notch1 knockdown resulted in significant reduction in the expression of urokinase plasminogen activator (uPA) and matrix metalloproteinase-9 (MMP9) gene transcripts. These data were further verified by reverse transcription-PCR, real-time reverse transcription-PCR, and immunoblot analysis. Knockdown of Notch1 was also observed to significantly reduce the mRNA expression and protein levels of uPA and its receptor uPAR. A significant reduction in MMP9 expression in Notch1 knockdown cells suggested a role for Notch1 in augmenting MMP9 transcription. Our data show the involvement of Notch1 in human PCa invasion and that silencing of Notch1 inhibits invasion of human PCa cells by inhibiting the expression of MMP9 and uPA. Thus, targeting of Notch1 could be an effective therapeutic approach against PCa.

Tumor growth inhibition by synthetic and expressed siRNA targeting focal adhesion kinase

Focal adhesion kinase (FAK) was first identified as a viral Src substrate, and substantial experimental data have significantly correlated the elevated FAK expression in human tumor cells with an increased cell adhesion and invasion potential. However, studies investigating the role of FAK in cell proliferation have been limited. Recently, a technique known as RNA interference (RNAi) was successfully adapted to mammalian cells to decrease specifically the expression of targeted cellular genes. In this study, we investigated the role of FAK in cell proliferation, adhesion, and migration by using small interfering RNA (siRNA) technique. Firstly, we constructed a plasmid library expressing short hairpin RNAs (shRNAs) targeting FAK and selected clones substantially suppressing FAK expression in HeLa and HT1080 cells. We then studied the function of FAK in the highly invasive human prostate cancer cell line, PC3M, and mouse breast cancer cell line 4T1, by using selected shRNA clones (#40 and #42) and siRNAs chemically synthesized following the target sequences of #40 and #42. We demonstrated that the decrease of FAK protein expression by treatment with shRNA/siRNA targeting FAK inhibited cell adhesion on a fibronectin/laminin-coated plate, cell migration in a haptotactic migration assay, and cell proliferation in vitro. Furthermore, it suppressed tumor growth in vivo in heterotopic/orthotopic mice models. These results support our hypothesis that FAK plays a crucial role in tumor formation and growth in vivo by regulation of cell adhesion and proliferation by FAK-dependent signals.

Membrane Type 1 Matrix Metalloproteinase Induces Epithelial-to-Mesenchymal Transition in Prostate Cancer

By mining DNA microarray data bases at GenBank, we identified up-regulation of membrane type 1 matrix metalloproteinase (MT1-MMP) in human primary and metastatic prostate cancer specimens as compared with nonmalignant prostate tissues. To explore the role of up-regulated MT1-MMP in early stage cancer progression, we have employed a three-dimensional cell culture model. Minimally invasive human prostate cancer cells (LNCaP) were transfected with MT1-green fluorescent protein (GFP) chimeric cDNA as compared with GFP cDNA, and morphologic and phenotypic changes were characterized. GFP-expressing LNCaP cells formed multicellular spheroids with cuboidal-like epithelial morphology, whereas MT1-GFP-expressing cells displayed a fibroblast-like morphology and a scattered growth pattern in type I collagen gels. Cell morphologic changes were accompanied by decreased epithelial markers and enhanced mesenchymal markers, consistent with epithelial-to-mesenchymal transition. MT1-MMP-induced morphologic change and cell scattering were abrogated by target inhibition of either the catalytic domain or the hemopexin domain. We further demonstrated that MT1-MMP-induced phenotypic changes were dependent upon up-regulation of Wnt5a, which has been implicated in epithelial-to-mesenchymal transition. We conclude that MT1-MMP plays an important role in early cancer dissemination by converting epithelial cells to migratory mesenchymal-like cells.