Prostate Cancer Stem Cell Markers Research Articles

Berbamine targets cancer stem cells and reverses cabazitaxel resistance via inhibiting IGF2BP1 and p-STAT3 in prostate cancer.

Cancer stem cells (CSCs) are a small subpopulation of tumor cells with the capability of self-renewal and drug resistance, leading to tumor progression and disease relapse. Our study aimed to investigate the antitumor effect of berbamine, extracted from berberis amurensis, on prostate CSCs. Sphere formation was used to collect prostate CSCs. The viability, proliferation, invasion, migration, and apoptosis assays were used to evaluate the antitumor effect of berbamine on prostate CSCs. Prostate CSC markers were analyzed by flow cytometry and qRT-PCR. Small RNA sequencing analysis was conducted to analyse miRNAs. Exosomes were extracted using the ExoQuick-TC kit and verified by testing exosomal markers using western blot. Berbamine targets prostate CSCs. Additionally, berbamine enhanced the antitumor effect of cabazitaxel, a second-line chemotherapeutic drug for advanced prostate cancer, and re-sensitized Cabazitaxel-resistant PCa cells (CabaR-DU145) to cabazitaxel by inhibiting ABCG2, CXCR4, IGF2BP1, and p-STAT3. Berbamine enhanced the expression of let-7 miRNA family and miR-26b and influenced the downstream targets IGF2BP1 and p-STAT3, respectively. Silencing CXCR4 and ABCG2 downregulated the expression of IGF2BP1 and p-STAT3, respectively. Importantly, berbamine enhanced also levels of exosomal let-7 family and miR-26b, suggesting that berbamine possibly influences the expression of let-7 family and miR-26b through exosome delivery. Exosomes derived from berbamine-treated CabaR-DU145 cells re-sensitized the cells to cabazitaxel. Berbamine enhanced the toxic activity of cabazitaxel and reversed cabazitaxel resistance potentially through CXCR4/exosomal let-7/IGF2BP1 and ABCG2/exosomal miR-26b/p-STAT3 axes.

Abstract 43: Heme Oxygenase 1 Counteracts Pro-Stemness and Pro-Invasive Effect Triggered by Communication With Bone Progenitors in Prostate Cancer Cells

Abstract Purpose: Mortality in prostate cancer (PCa) patients is mostly associated with bone metastasis and aggressive phenotypes promoted by prostate cancer stem cells (PCSCs). We have previously described that heme oxygenase 1 (HO-1), the rate-limiting enzyme in heme catabolism with antioxidant and antiinflammatory properties, presents an antitumoral role in PCa. In this work, we assessed the role of HO-1 as a modulator of stemness and metastasis associated genes in PCa cells conditioned by bone progenitor cells. Methods: An indirect transwell co-culture system of PC3 cells, a PCa cell line, with MC3T3 cells, an osteoblast precursor cell line, was developed as an in vitro model of PCa bone metastasis. Additionally, PC3 cells were pre-treated with hemin, a pharmacological HO-1 inductor. An RNA-seq was performed to analyze the transcriptome of PC3 cells. The expression of a curated list of 87 genes associated with stemness, metastasis and the STAT3 pathway, including PCSC and classic pluripotency markers, together with a gene signature previously described by our group (ADAM15, BCL2L1, LTBR, MBNL2, SPINT1), was assessed. Results were complemented with survival data of PCa patients (TCGA-PRAD, n=565). Results: Our results showed that PC3 cells co-cultured with MC3T3 cells displayed an upregulation of PCSC markers CD44, ALDH1A3 and ALDH1L2, pluripotency markers OCT4 and SOX2, and BCL2L1 and LTBR, two genes included in our signature, compared with non-co-cultured PC3 cells. Further, when comparing co-cultured PC3 cells vs. co-cultured PC3 cells pre-treated with hemin, in the latter group the expression of 71/87 genes associated with stemness, metastasis and STAT3 pathway decreased, including CD44, ALDH1A3, ALDH1L2, OCT4, MBNL2 and ADAM15. Moreover, when evaluating patients’ disease progression free survival, those with high expression of OCT4 showed a lower risk of the event. Conclusion: HO-1 expression modulates stemness and metastasis related genes in PCa, promoting a more differentiated state, counteracting the pro-stemness effect of communication with bone progenitors. This further supports the antitumoral role of HO-1 in PCa pointing out to its potential as a therapeutic target for the disease. Citation Format: Ines Achinelli, Agustina Sabater, Pablo Sanchis, Nicolás Anselmino, Sofía Lage-Vickers, Gaston Pascual, Rocio Seniuk, Pamela Freiria, Javier Cotignola, Elba Vazquez, María Sol Ruiz, Geraldine Gueron, Ayelen Toro. Heme Oxygenase 1 Counteracts Pro-Stemness and Pro-Invasive Effect Triggered by Communication With Bone Progenitors in Prostate Cancer Cells [abstract]. In: Proceedings of the 11th Annual Symposium on Global Cancer Research; Closing the Research-to-Implementation Gap; 2023 Apr 4-6. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2023;32(6_Suppl):Abstract nr 43.

Abstract 4757: TNFAIP8 facilitates metabolic reprogramming in prostate cancer cells

Abstract Tumor necrosis factor-α-induced protein 8 (TNFAIP8), a member of TIPE/TNFAIP8 family, has been associated with multiple oncogenic roles in human cancers. Here we investigated the role of TNFAIP8 in metabolic reprogramming in prostate cancer (PCa) cells. Ectopic expression of TNFAIP8 increased cell survival/proliferation by enhancing metabolic activity in PCa cells. TNFAIP8 activated the PI3K-AKT pathway and up-regulated the expression of cell proliferation markers, cell cycle-related proteins, and PCa stem cell markers. TNFAIP8 was also found to regulate the expression of glucose metabolizing enzymes, enhancing glucose consumption, and endogenous ATP production. Treatment with glycolysis inhibitor 2-deoxyglucose (2-DG) reduced TNFAIP8 mediated glucose consumption /ATP production and spheroid formation in PCa cells. Moreover, TNFAIP8 maintained mitochondrial membrane potential and increased glycolysis/oxidative phosphorylation. These changes were also consistent with an observed altered metabolomic profile in PCa cells transfected with TNFAIP8. Collectedly, our data suggest that TNFAIP8 exerts its oncogenic effects by enhancing glucose metabolism and by facilitating metabolic reprogramming in PCa cells. Citation Format: Suryakant Niture, Minghui Lin, Joab O. Odera, John Moore, Deepak Kumar. TNFAIP8 facilitates metabolic reprogramming in prostate cancer cells [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4757.

Abstract 282: MicroRNAs located at chromosome 8p21-22 region as novel factors underlying racial disparities in prostate cancer aggressiveness

Abstract The mechanistic basis of racial disparities in prostate cancer (PCa) aggressiveness between African American (AA) and Caucasian (CA) men are not yet fully understood. Further, molecular biomarkers to predict aggressive disease at its onset have been studied primarily in CAs, the relevance of these biomarkers to AAs are largely unknown. We propose a novel, paradigm-shifting hypothesis that expression of microRNA (miRNA) genes-miR-3622a and miR-383-located within frequently deleted chr8p21-22 region constitute important molecular factors contributing to racial disparities in PCa aggressiveness in AA vs CA men. Chromosome 8p deletions are a frequent alteration of PCa genome, with a common region of loss of heterozygosity at the chr8p21-22 locus. We previously showed that this region is associated with a set of tumor suppressive miRNAs (miR-3622a/b, -383, -4288) that are downregulated in PCa with important causal roles in tumor progression, recurrence and metastasis. Chr8p deletions increase significantly with tumor grade and are associated with poor prognosis. These deletions are well studied in CA men. However, there have been conflicting reports on frequency of chr8p deletions in AA men. In view of these conflicting studies and in light of our paradigm-shifting studies establishing the link between chr8p deletions and loss of miRNA genes in this region, we examined the expression of these miRNAs in AA vs CA clinical PCa tissues. We found that miR-3622a and miR-383 expression is significantly lower in AA men as compared to age, tumor stage and grade matched CAs. To examine if these miRNAs constitute causal factors contributing to PCa racial disparities, we overexpressed miR-3622a/miR-383/control miR in AA and CA PCa cell lines followed by functional assays. We found that these miRNAs exert more prominent effects on cellular proliferation and apoptosis in AA cell lines. To understand molecular mechanisms contributing to disparate functional effects of these miRNAs in AA vs CA cell lines, we examined potential miRNA target genes and found that miR-3622a regulates PCa stem cell marker, CD44 while miR-383 represses LEF1 and ZEB1 in a race-specific manner. Further, we determined the mechanistic basis of differential expression of miR-3622a in AAs vs CAs by examining copy number alterations (CNAs) and methylation at this locus using PCa clinical samples. Our analyses showed that while this locus is genomically altered at a lower frequency in AAs, significantly increased frequency of miRNA promoter hypermethylation was found in AAs as compared to CAs. In conclusion, our data suggests that miRNAs located in frequently deleted chr8p21-22 region constitute important causal factors contributing to racial disparities in PCa aggressiveness and clinical outcomes and are potential biomarkers to predict PCa aggressiveness and tumor recurrence in AA men. Citation Format: Divya Bhagirath, Nikhil Patel, Santu Ghosh, Roni Bollag, Sharanjot Saini. MicroRNAs located at chromosome 8p21-22 region as novel factors underlying racial disparities in prostate cancer aggressiveness [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 282.

Abstract B047: Advanced glycation end products promote prostate tumor growth and are a potential biologic consequence of lifestyle factors contributing to cancer disparity

Abstract Advanced glycation end-products (AGEs), are reactive metabolites produced endogenously as a consequence of glucose uptake during glycolysis. AGEs accumulate in tissues and organs as we grow older to promote multiple chronic disease phenotypes. AGE pathogenic effects are mediated through modification of protein function, genetic fidelity, stress responses and cellular signaling pathways. Critically, cancer disparity factors such as a sedentary lifestyle, obesity and an unhealthy diet are external influences that also contribute to the AGE accumulation pool in the body. This research group examined circulating and tumor AGE levels in clinical specimens of prostate cancer and identified a race specific, tumor-dependent pattern of accumulation. AGE levels were highest in aggressive tumors, especially those from men with African ancestry. Increased AGE levels correlated with an upregulation in the receptor for advanced glycation end products (RAGE) and activated NFkB. In a syngeneic subcutaneous prostate cancer mouse model, chronic consumption of AGE resulted in a 3-fold increase in tumor growth. Strikingly, dietary-AGE mediated increases in tumor growth were accompanied by a cytoplasmic accumulation of AR, elevation in MYC, RAGE, and AGE as well as increased cell proliferation. Cytoplasmic accumulation of AR is elevated in CRPC tissue and is an independent predictor of biochemical recurrence. Our data show that treatment of prostate cancer cells with AGEs induces a neuroendocrine differentiated phenotype by promoting a more mesenchymal morphology and increasing the expression of associated marker genes including ENO2, MYC and SYP and the prostate cancer stem cell marker CD44 as well as the downregulation of AR. The aberrant activation and recruitment of immune cells is a major pathogenic consequence of AGE accumulation, and a series of studies have highlighted the tumor-associated immune response as a critical pathway contributing to cancer disparity. Using patient-derived primary tumor cells, the investigators found that AGEs released into the extracellular matrix may recapitulate the tumor-associated immune response observed in ancestry-specific prostate tumor tissues. Further preliminary studies indicate that AGE treatment of prostate cancer cells can alter how cancer cells metabolize glucose to promote an aggressive phenotype. The investigators' studies support the concept that AGE metabolites represent a biologic consequence of the socioeconomic and environmental factors that promote cancer health disparity. As our understanding of tumor biology advances, it is becoming increasingly clear that these inter-related lifestyle factors have distinct molecular consequences on the biologic makeup of tumors, altering cell signaling events and gene expression profiles to contribute to cancer disparity outcomes such as its earlier development or its progression to more aggressive disease. Citation Format: Pamela Woods, Bradley A. Krisanits, Dion Foster, Lourdes M. Nogueira, Laura Spruill, Marvella E. Ford, Michael B. Lilly, Victoria J. Findlay, David P. Turner. Advanced glycation end products promote prostate tumor growth and are a potential biologic consequence of lifestyle factors contributing to cancer disparity [abstract]. In: Proceedings of the Eleventh AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2018 Nov 2-5; New Orleans, LA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(6 Suppl):Abstract nr B047.

Capsaicin suppressed activity of prostate cancer stem cells by inhibition of Wnt/β-catenin pathway.

Cancer stem cells (CSCs) are considered as the origin and driving cells of cancer, and play a key role in the progress of cancer. Studies have shown that capsaicin exerted inhibitory effect on prostate cancer cells, however, the effects of capsaicin on prostate CSCs remain undefined. In the present study, we showed that capsaicin could downregulate prostate CSCs markers and inhibit the growth of PC-3 and DU145 prostate cancer stem cells. Further, we found capsaicin suppressed the expression of Wnt-2, p-GSK3β and β-catenin, along with downregulation of Wnt/β-catenin pathway target genes c-myc and cyclinD1. Using LiCl, a activator of Wnt/β-catenin pathway, we found activation of Wnt/β-catenin pathway could ameliorate the downregulation of prostate CSCs markers and the growth inhibition induced by capsaicin in prostate cancer stem cells. Those data suggested that the inhibition effect of capsaicin on prostate cancer stem cells and the anti-cancer effect of capsaicin on prostate cancer stem cell may be mediated by Wnt/β-catenin pathway. Findings from this study reveals for the first time the potential role and mechanisms of capsaicin on prostate cancer stem cells.

Cancer stem cells in prostate cancer radioresistance.

Cancer stem cells (CSCs) in prostate cancer (CaP) are regarded as major contributors to radioresistance due to complex mechanisms including enhanced DNA repair, increased intracellular reactive oxygen species scavenging, activation of anti-apoptotic pathways, microenvironment hypoxia, epithelial-to-mesenchymal transition (EMT) and autophagy. They are also believed to cause tumour recurrence and metastasis due to their unique capability to survive and replicate the heterogeneity of the original tumour. Finding markers of prostate CSCs (PCSC) for identification, prognostication and targeting is key in enhancing therapeutic and clinical outcomes. Markers such as aldehyde dehydrogenase, CD44, integrins and EMT markers have been proved to show great potential in being sensitive and specific to the presence of PCSCs. Novel therapies such as Hedgehog and Wnt pathway inhibitors, angiogenesis inhibitors and metformin show potential in eliminating PCSCs to improve therapeutic outcomes. Here, we review the current state of the literature regarding mechanisms of PCSC radioresistance, promising PCSC markers and novel PCSC-specific therapeutic approaches and their implications in CaP treatment and prognosis.

Luteolin attenuates Wnt signaling via upregulation of FZD6 to suppress prostate cancer stemness revealed by comparative proteomics

The mechanisms underlying luteolin-induced inhibition of prostate cancer (PCa) stemness have remained elusive. Here, we report that luteolin suppresses PCa stemness through Wnt signaling by upregulation of FZD6 (frizzled class receptor 6). Luteolin inhibits PCa cell proliferation, migration, self-renewal as well as the expression of prostate cancer stem cell markers in vitro. Through iTRAQ-based quantitative proteomics study, we identified 208 differentially expressed proteins in luteolin-treated PC-3 cells. Subsequent mechanistic analysis revealed that luteolin inhibits Wnt signaling by transcriptional upregulation of FZD6, and thereby suppressing the stemness of PCa cells. Furthermore, we identified FZD6 as a tumor suppressor that can abolish PCa stemness. In summary, our findings demonstrate that suppression of Wnt signaling by upregulation of FZD6 is a mechanism underlying luteolin-induced inhibition of PCa stemness. Our work suggests a new therapeutic strategy against human prostate cancer caused by aberrant activation of Wnt signaling.

Abstract 1934: MicroRNA-383 located in frequently deleted chromosomal locus 8p22 regulates prostate cancer stem cell marker CD44

Abstract A major genomic alteration in prostate cancer (PCa) is frequent loss of chromosome (chr) 8p with a common region of loss of heterozygosity (LOH) at chr8p22 locus. Genomic studies implicate this locus in the initiation of clinically significant PCa and with progression to metastatic disease. However, the genes within this region have not been fully characterized to date. Here we demonstrate for the first time that a microRNA component of this region -miR-383- is frequently downregulated in prostate cancer, plays a critical role in determining tumor initiating potential and is involved in prostate cancer metastasis via direct regulation of CD44, a ubiquitous marker of PCa tumor initiating cells (TICs)/ stem cells. Expression analyses of miR-383 in PCa clinical tissues established that low miR-383 expression is associated with poor prognosis. Functional data suggests that miR-383 regulates PCa tumor initiating/ stem-like cells via CD44 regulation. Ectopic expression of miR-383 inhibited tumor initiating capacity of CD44+ PCa cells. Also, ‘anti-metastatic’ effects of ectopic miR-383 expression were observed in a PCa experimental metastasis model. In view of our results, we propose that frequent loss of miR-383 at chr8p22 region leads to tumor initiation and prostate cancer metastasis. Thus, we have identified a novel finding that associates a long observed genomic alteration to PCa stemness and metastasis. Our data suggests that restoration of miR-383 expression may be an effective therapeutic modality against PCa relapse and metastasis. Importantly, we identified miR-383 as a novel PCa diagnostic biomarker with potential that outperforms that of serum PSA. Citation Format: Nathan Bucay, Kiran Sekhon, Varahram Shahryari, Yozo Mitsui, Guoren Deng, Z. Laura Tabatabai, Shahana Majid, Soichiro Yamamura, Rajvir Dahiya, Yuichiro Tanaka, Sharanjot Saini. MicroRNA-383 located in frequently deleted chromosomal locus 8p22 regulates prostate cancer stem cell marker CD44. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1934.

Abstract 3871: Tie-2 regulates stemness and metastasis of prostate cancer cells

Abstract Introduction: Prostate cancer is the most commonly diagnosed male cancer in Western countries. Currently, the major treatment challenge for prostate cancer patients is the development of tumor metastasis. Ample evidence supports the idea that tumor metastasis originates from a rare population of cancer cells known as cancer stem cells (CSCs) [1]. Unfortunately, little is known about the identity of these cells, making it difficult to target prostate tumor metastasis. Here we reported the identification of a rare population of prostate cancer cells which express the Tie-2 protein, a tyrosine kinase receptor required for the bone marrow homing and colonization of hematopoietic stem cells. Notably, this Tie-2 positive population exists exclusively in highly metastatic prostate cancer cell lines. Methods:To study the role of Tie-2 in prostate tumor metastasis, we have performed fluorescence-activated cell sorting (FACS) to isolate the Tie-2+ population from a prostate cancer cell line (PC-3). We then performed cDNA microarray analysis to characterize the gene expression profile of these cells. Furthermore, we have performed cell adhesion assay to examine the ability of the Tie-2+ cells in adhering to osteoblasts and endothelial cells. Besides that, we have also performed quiescent staining and drug sensitivity assay to examine whether Tie-2+ cells are more quiescent, and thus become resistant to chemotherapeutic drug. Finally, we have injected both Tie-2+ and Tie-2- PC-3 cells intracardiacly into the NOD-SCID mice to determine if Tie-2 expression promote prostate tumor metastasis under in vivo condition. Results: Data from our study revealed that Tie-2+ cells express higher level of prostate CSC markers when compared to the Tie-2- population. Meanwhile, Tie-2+ cells are highly adhesive to both osteoblasts and endothelial cells, a characteristic necessary for tumor metastasis. We also found that Tie-2+ cells are more quiescent and resistant to the chemotherapeutic drug cabazitaxel, further support that these cells possess CSC-like characteristics. More importantly, we found that Tie-2+ cells, but not the Tie-2- cells population, developed metastatic tumor in vivo. Conclusions: Our data suggested that Tie-2 plays an importantly role in the development of drug resistance and prostate tumor metastasis. Thus, Tie-2 might be a novel therapeutic target for treatment of advanced prostate cancer patients.

Abstract 5311: Proteomic characterization of zoledronic acid-resistant prostate cancer cells identified key proteins in cytoskeleton organization and cancer stem cell markers associated with a very aggressive phenotype

Abstract The aminobiphosphonate Zoledronic acid (ZOL) inhibit osteoclast-mediated bone resorption and it is used to prevent skeletal complications from bone metastases. Accumulating evidences in both preclinical and clinical studies indicated that ZOL might also have anticancer activity. We have recently selected for the first time the ZOL-resistant DU145R80 prostate cancer (PCa) cell line that demonstrated an antiapoptotic and proangiogenic phenotype with increased invasive capability and epithelial to mesenchymal transition (EMT), compared to parental DU145 cells. Interestingly, we also demonstrated that both the acquired resistance to ZOL and the aggressive phenotype are mediated by p38-MAPK (Milone et al. Cell Death Dis. 2013, 4:e641). To further investigate the mechanism of ZOL-resistance and of the parallel acquisition of an aggressive phenotype in this novel syngeneic model of PCa, we took advantage of a two-dimensional difference gel electrophoresis (2D-DIGE)/mass spectrometry (MS) proteomic approach, to investigate differential expressed proteins between DU145R80 and DU145 cell lines. We found 21 statistically differentially expressed protein spots between the two cell lines (average volume ratio threshold of ±1.4-fold and 95% level of significance, p<0.05) and 15 of these were identified by MS and validated by real-time PCR, 1D or 2D immunoblots. The identified proteins were involved in cell metabolism, cytoskeleton, nuclear lamina organization, protein fate and RNA processing, such as ALDH7A1, ANXA1, Lamin A/C, Filamin A, Lamin B2, PSMA6 and eEF1γ. Several of these proteins are related with the acquisition of a cancer stem cells (CSC) phenotype and indeed we showed in DU145R80 also the overexpression of additional prostate CSC markers such as Nanog, Oct-4, Snail and Integrin-aV. Furthermore, in DU145R80 compared to DU145 cells, we observed the increased presence of numerous podosomes/invadopodia and membrane bleb protrusions where FLNA clearly co-localize with actin. Interestingly, by using publicly available genomic data on PCa (http://www.oncomine.org) we demonstrated statistically significant higher expression of the genes codifying the identified proteins, in PCa vs normal tissues. Finally, proteomic results were further processed by interactome pathway analysis demonstrating a strong relationships between the identified proteins and additional effectors in both direct/indirect analysis, including p38-MAPK, and generating a relevant statistically significant network associated with cancer disease as well as with cellular movement and organization. Overall we confirmed that ZOL-resistant PCa cells developed an aggressive phenotype related with stemness feature and identified novel potential prognostic markers and/or therapeutic targets for PCa. Citation Format: Maria Rita Milone, Biagio Pucci, Federica Iannelli, Rita Lombardi, Katia Bifulco, Francesca Bruzzese, Elena Di Gennaro, Antonio Avallone, Maria Vincenza Carriero, Alfredo Budillon. Proteomic characterization of zoledronic acid-resistant prostate cancer cells identified key proteins in cytoskeleton organization and cancer stem cell markers associated with a very aggressive phenotype. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5311. doi:10.1158/1538-7445.AM2014-5311

Detection and Phenotyping of Circulating Tumor Cells in High-Risk Localized Prostate Cancer

BackgroundIn this study, we aimed to determine the feasibility of identifying CTCs in patients with HRLPC, using a modified isolation procedure using the CellSearch (Veridex) platform, and to assess the expression of stem cell and epithelial-mesenchymal transition (EMT) markers on the CTCs. Patients and MethodsThirty-five patients with HRLPC who had chosen prostatectomy for definitive management were prospectively identified. After obtaining consent, four 30-mL blood draws were performed, 2 before surgery and 2 after surgery. The CTC-containing fraction was Ficoll-purified and transferred to a CellSave (Veridex) tube containing dilution buffer before standard enumeration using the CellSearch system. Loss of E-cadherin expression, a marker of EMT, and CD133, a putative prostate cancer stem cell marker, were characterized using the open channel of the CellSearch platform. CTC fragments were also enumerated. ResultsUsing the modified methodology, CTCs were detectable in 49% of patients before surgery. Although no correlation between CTC count and biochemical recurrence (BR) was observed, the percentages of CD133 and E-cadherin–positive CTC fragments were associated with BR at 1 year. ConclusionOur results suggest that further research into the development of CTCs as prognostic biomarkers in HRLPC is warranted.

OP0022 TIE-2 regulates stemness and metastasis of prostate cancer cells

Background Prostate cancer is the most commonly diagnosed male cancer in western countries. Currently, the major treatment challenge for prostate cancer patients is the development of tumour metastasis. Ample evidence supports the idea that tumour metastasis originates from a rare population of cancer cells known as cancer stem cells (CSCs). Unfortunately, little is known about the identity of these cells, making it difficult to target prostate tumour metastasis. Here we report the identification of a rare population of prostate cancer cells that express the Tie-2 protein, a tyrosine kinase receptor needed for bone marrow homing and colonisation of haemopoietic stem cells. Notably, this Tie-2-positive population exists exclusively in highly metastatic prostate cancer cell lines. Methods To study the role of Tie-2 in prostate tumour metastasis, we used fluorescence-activated cell sorting to isolate the Tie-2-positive population from a prostate cancer cell line (PC-3). We then used cDNA microarray analysis to characterise the gene expression profile of these cells. Furthermore, we did a cell adhesion assay to examine the ability of the Tie-2-positive cells in adhering to osteoblasts and endothelial cells. We also undertook quiescent staining and a drug sensitivity assay to examine whether Tie-2-positive cells are more quiescent, and thus become resistant to chemotherapeutic drugs. Finally, we injected both Tie-2-positive and Tie-2-negative PC-3 cells intracardiacly into NOD-SCID mice to establish whether Tie-2 expression promotes prostate tumour metastasis in vivo. Findings Data from our study revealed that Tie-2-positive cells express higher level of prostate CSC markers compared with the Tie-2-negative population. Meanwhile, Tie-2-positive cells are highly adhesive to both osteoblasts and endothelial cells, a characteristic necessary for tumour metastasis. We also found that Tie-2-positive cells are more quiescent and resistant to the chemotherapeutic drug cabazitaxel, providing further support that these cells possess CSC-like characteristics. More importantly, we found that Tie-2-positive cells, but not Tie-2-negative cells, developed metastatic tumours in vivo. Interpretation Our data suggest that Tie-2 plays an important part in the development of drug resistance and prostate tumour metastasis. Thus, Tie-2 might be a novel therapeutic target for treatment of patients with advanced prostate cancer.

Validation of stem cell markers in clinical prostate cancer: α6-Integrin is predictive for non-aggressive disease

Stem cells are postulated to mediate prostate cancer progression, and represent a small fraction of the entire tumor. Various proteins (α2-integrin, α6-integrin, CD117, CD133, EZH2, OCT3/4) are associated with a prostate cancer stem cell phenotype in cell lines and xenografts. Our objective was to investigate expression of stem cell markers in clinical prostate cancer in relation to outcome. We validated immunohistochemical expression of stem cell markers in 481 prostate cancer patients and correlated expression with clinicopathologic parameters. Sporadic expression of α2-integrin was present in a fraction of tumor cells (<5%) in 94.7% of tumors and associated with PSA > 10 ng/ml (P = 0.04). α6-Integrin expression (<5%) occurred in 28.4% patients, while ≥5% α6-integrin expression was associated with PSA≤10 ng/ml (P = 0.01), Gleason score <7 (P < 0.01) and pT2-disease (P = 0.02). α6-integrin was predictive for biochemical recurrence (P < 0.01), local recurrence (P = 0.03) and disease specific death (P = 0.03). EZH2 expression was generally low with 2.6% of tumors showing ≥1% positive cells. EZH2 was associated with Gleason score ≥7 (P = 0.01) and biochemical recurrence (P = 0.01). We did not identify expression of CD117, CD133, and OCT3/4 in prostate cancer samples. Expression of α2-integrin and EZH2 in a small fraction of prostate cancer cells is supportive for their role as stem cell marker. Although α6-integrin was not a unique stem cell marker, it was predictive for prostate cancer biochemical and local recurrence, and disease specific death. The validity of CD117, CD133, and OCT3/4 as prostate cancer stem cell marker is questionable since these proteins were not expressed in clinical prostate cancer.

Galiellalactone Inhibits Stem Cell-Like ALDH-Positive Prostate Cancer Cells

Galiellalactone is a potent and specific inhibitor of STAT3 signaling which has been shown to possess growth inhibitory effects on prostate cancer cells expressing active STAT3. In this study we aimed to investigate the effect of galiellalactone on prostate cancer stem cell-like cells. We explored the expression of aldehyde dehydrogenase (ALDH) as a marker for cancer stem cell-like cells in different human prostate cancer cell lines and the effects of galiellalactone on ALDH expressing (ALDH+) prostate cancer cells. ALDH+ subpopulations were detected and isolated from the human prostate cancer cell lines DU145 and long-term IL-6 stimulated LNCaP cells using ALDEFLUOR® assay and flow cytometry. In contrast to ALDH− cells, ALDH+ prostate cancer cells showed cancer stem cell-like characteristics such as increased self-renewing and colony forming capacity and tumorigenicity. In addition, ALDH+ cells showed an increased expression of putative prostate cancer stem cell markers (CD44 and integrin α2β1). Furthermore, ALDH+ cells expressed phosphorylated STAT3. Galiellalactone treatment decreased the proportion of ALDH+ prostate cancer cells and induced apoptosis of ALDH+ cells. The gene expression of ALDH1A1 was downregulated in vivo in galiellalactone treated DU145 xenografts. These findings emphasize that targeting the STAT3 pathway in prostate cancer cells, including prostate cancer stem cell-like cells, is a promising therapeutic approach and that galiellalactone is an interesting compound for the development of future prostate cancer drugs.

Human prostate cancer stem cells: new features unveiled

Human prostate cancer stem cells: new features unveiled

287 PALM GAMMA-T3 AS AN EFFECTIVE AGENT IN TARGETING PROSTATE CANCER STEM CELL-LIKE POPULATION

You have accessJournal of UrologyProstate Cancer: Basic Research1 Apr 2011287 PALM GAMMA-T3 AS AN EFFECTIVE AGENT IN TARGETING PROSTATE CANCER STEM CELL-LIKE POPULATION Daniel Yap and Ming Tat Ling Daniel YapDaniel Yap Singapore, Singapore More articles by this author and Ming Tat LingMing Tat Ling Brisbane, Australia More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2011.02.379AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Emerging evidences support that prostate cancer is originated from a sub-population of cells- prostate cancer stem cells (CSCs). Conventional therapies for prostate cancer are believed to target mainly the majority of differentiated tumor cells but spare CSCs, which may account for the subsequent disease relapse after the treatment. Therefore, successful elimination of CSCs may be an effective strategy to archive complete remission from this disease. Tocotrienols (T3) are vitamin-E constituents that naturally found in palm oil and have been shown to have anticancer effect against a wide-range of human cancers. Recently, we have reported that gamma-T3, one of the four T3 isomers, was the most potent form of T3 against prostate cancer. METHODS In this study, we used cell sorting method for isolation of prostate cancer stem cells, westen blotting for characterization of prostate cancer stem cell markers, stem cell assay to characterize stemness of the prostate cancer cells and in vivo experiments to quantify the rate of tumor initiation. RESULTS We found that gamma-T3 treatment not only inhibits prostate cancer cell invasion, but also sensitizes the cells to Docetaxel-induced apoptosis, suggesting that gamma-T3 may be an effective therapeutic agent against advanced stage prostate cancer. Here, we demonstrate for the first time that gamma-T3 can down-regulate the expression of prostate cancer stem cell markers (CD133/CD44) in androgen independent (AI) prostate cancer cell lines (PC-3 & DU145), as evident from Western blotting and flow cytometry analysis. Meanwhile, spheroid formation ability of the prostate cancer cells was significantly hampered by gamma-T3 treatment. More importantly, pre-treatment of PC-3 cells with gamma-T3 was found to interfere with the tumor initiation ability of the cells. CONCLUSIONS Our data suggest that gamma-T3 may be an effective agent in targeting prostate CSCs, which may account for its anti-cancer and chemosensitizing effects reported in previous studies. © 2011 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 185Issue 4SApril 2011Page: e116-e117 Advertisement Copyright & Permissions© 2011 by American Urological Association Education and Research, Inc.MetricsAuthor Information Daniel Yap Singapore, Singapore More articles by this author Ming Tat Ling Brisbane, Australia More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Gamma‐tocotrienol as an effective agent in targeting prostate cancer stem cell‐like population

Emerging evidence supports that prostate cancer originates from a rare subpopulation of cells, namely prostate cancer stem cells (CSCs). Conventional therapies for prostate cancer are believed to mainly target the majority of differentiated tumor cells but spare CSCs, which may account for the subsequent disease relapse after treatment. Therefore, successful elimination of CSCs may be an effective strategy to achieve complete remission from this disease. Gamma-tocotrienols (γ-T3) is one of the vitamin-E constituents, which have been shown to have anticancer effects against a wide range of human cancers. Recently, we have reported that γ-T3 treatment not only inhibits prostate cancer cell invasion but also sensitizes the cells to docetaxel-induced apoptosis, suggesting that γ-T3 may be an effective therapeutic agent against advanced stage prostate cancer. Here, we demonstrate for the first time that γ-T3 can downregulate the expression of prostate CSC markers (CD133/CD44) in androgen-independent prostate cancer cell lines (PC-3 and DU145), as evident from Western blotting analysis. Meanwhile, the spheroid formation ability of the prostate cancer cells was significantly hampered by γ-T3 treatment. In addition, pretreatment of PC-3 cells with γ-T3 was found to suppress tumor initiation ability of the cells. More importantly, although CD133-enriched PC-3 cells were highly resistant to docetaxel treatment, these cells were as sensitive to γ-T3 treatment as the CD133-depleted population. Our data suggest that γ-T3 may be an effective agent in targeting prostate CSCs, which may account for its anticancer and chemosensitizing effects reported in previous studies.

17-Beta-estradiol induces neoplastic transformation in prostatic epithelial cells

Although estrogens have been long implicated in the prostate carcinogenesis, direct evidence showing their carcinogenicity on prostatic epithelial cells has not yet been clearly demonstrated. In this study, we treated an immortalized, non-transformed and androgen-responsive rat prostatic epithelial cell line NRP-152 with 17β-estradiol (E 2) at concentrations 1–3 μM for period 2–6 weeks. After in vitro treatment, we evaluated the anchorage-independent growth of E 2-treated NRP-152 cells by soft agar assay and isolated the colonies formed by the transformed E 2-NRP-152 cells in soft agar for further growth phenotype characterization. Our results showed that the isolated E 2-NRP-152 clones displayed neoplastic transformation phenotype, as demonstrated by their capacity of forming colonies in soft agar and tumors in immunodeficient nude mice, while losing their spheroid formation capacity in Matrigel 3D-culture. Western blot and RT-PCR analyses showed that the transformed E 2-NRP-152 cells expressed increased levels of ERα and several putative prostate cancer stem cell markers (integrins α2β1, CD44, CD133, ABCG2 and CXCR4) but decreased levels of ERβ and AR. Comet assay revealed that E 2-treatment also induced formation of comet cells, indicating that E 2 caused DNA damage to the NRP-152 cells. Our present findings demonstrated that in vitro E 2 exposure could neoplastically transform the rat prostatic epithelial cells, indicating that E 2 is carcinogenic to the prostatic epithelial cells.

PC3 prostate tumor-initiating cells with molecular profile FAM65Bhigh/MFI2low/LEF1low increase tumor angiogenesis

BackgroundCancer stem-like cells are proposed to sustain solid tumors by virtue of their capacity for self-renewal and differentiation to cells that comprise the bulk of the tumor, and have been identified for a variety of cancers based on characteristic clonal morphologies and patterns of marker gene expression.MethodsSingle cell cloning and spheroid culture studies were used to identify a population of cancer stem-like cells in the androgen-independent human prostate cancer cell line PC3.ResultsWe demonstrate that, under standard culture conditions, ~10% of PC3 cells form holoclones with cancer stem cell characteristics. These holoclones display high self-renewal capability in spheroid formation assays under low attachment and serum-free culture conditions, retain their holoclone morphology when passaged at high cell density, exhibit moderate drug resistance, and show high tumorigenicity in scid immunodeficient mice. PC3 holoclones readily form spheres, and PC3-derived spheres yield a high percentage of holoclones, further supporting their cancer stem cell-like nature. We identified one gene, FAM65B, whose expression is consistently up regulated in PC3 holoclones compared to paraclones, the major cell morphology in the parental PC3 cell population, and two genes, MFI2 and LEF1, that are consistently down regulated. This molecular profile, FAM65Bhigh/MFI2low/LEF1low, also characterizes spheres generated from parental PC3 cells. The PC3 holoclones did not show significant enriched expression of the putative prostate cancer stem cell markers CD44 and integrin α2β1. PC3 tumors seeded with holoclones showed dramatic down regulation of FAM65B and dramatic up regulation of MFI2 and LEF1, and unexpectedly, a marked increase in tumor vascularity compared to parental PC3 tumors, suggesting a role of cancer stem cells in tumor angiogenesis.ConclusionsThese findings support the proposal that PC3 tumors are sustained by a small number of tumor-initiating cells with stem-like characteristics, including strong self-renewal and pro-angiogenic capability and marked by the expression pattern FAM65Bhigh/MFI2low/LEF1low. These markers may serve as targets for therapies designed to eliminate cancer stem cell populations associated with aggressive, androgen-independent prostate tumors such as PC3.