Prostate cancer stem cells: from theory to practice

WDR3 promotes stem cell-like properties in prostate cancer by inhibiting USF2-mediated transcription of RASSF1A

BACKGROUND

WD repeat domain 3 (WDR3) is involved in tumor growth and proliferation, but its role in the pathological mechanism of prostate cancer (PCa) is still unclear.

METHODS

WDR3 gene expression levels were obtained by analyzing databases and our clinical specimens. The expression levels of genes and proteins were determined by a real-time polymerase chain reaction, western blotting and immunohistochemistry, respectively. Cell-counting kit-8 assays were used to measure the proliferation of PCa cells. Cell transfection was used to investigate the role of WDR3 and USF2 in PCa. Fluorescence reporter and chromatin immunoprecipitation assays were used to detect USF2 binding to the promoter region of RASSF1A. Mouse experiments were used to confirm the mechanism in vivo.

RESULTS

By analyzing the database and our clinical specimens, we found that WDR3 expression was significantly increased in PCa tissues. Overexpression of WDR3 enhanced PCa cell proliferation, decreased cell apoptosis rate, increased spherical cell number and increased indicators of stem cell-like properties. However, these effects were reversed by WDR3 knockdown. WDR3 was negatively correlated with USF2, which was degraded by promoting ubiquitination of USF2, and USF2 interacted with promoter region-binding elements of RASSF1A to depress PCa stemness and growth. In vivo studies showed that WDR3 knockdown reduced tumor size and weight, reduced cell proliferation and enhanced cell apoptosis.

CONCLUSIONS

WDR3 ubiquitinated USF2 and inhibited its stability, whereas USF2 interacted with promoter region-binding elements of RASSF1A. USF2 transcriptionally activated RASSF1A, which inhibited the carcinogenic effect of WDR3 overexpression.

ALCAM/CD166: A pleiotropic mediator of cell adhesion, stemness and cancer progression

Activated Leukocyte Cell Adhesion Molecule (ALCAM/CD166) is a glycoprotein involved in homotypic and heterotypic cell adhesion. ALCAM can be proteolytically cleaved at the cell surface by metalloproteases, which generate shedding of its ectodomain. In various tumors, ALCAM is overexpressed and serves as a valuable prognostic marker of disease progression. Moreover, CD166 has been identified as a putative cancer stem cell marker in particular cancers. Herein, we summarize biochemical aspects of ALCAM, including structure, proteolytic shedding, alternative splicing, and specific ligands, and integrate this information with biological functions of this glycoprotein including cell adhesion, migration and invasion. In addition, we discuss different patterns of ALCAM expression in distinct tumor types and its contribution to tumor progression. Finally, we highlight the role of ALCAM as a cancer stem cell marker and introduce current clinical trials associated with this molecule. Future studies are needed to define the value of shed ALCAM in biofluids or ALCAM isoform expression as prognostic biomarkers in tumor progression.

Tumor Microenvironment in Prostate Cancer: Toward Identification of Novel Molecular Biomarkers for Diagnosis, Prognosis, and Therapy Development

Prostate cancer (PCa) is by far the most commonly diagnosed cancer in men worldwide. Despite sensitivity to androgen deprivation, patients with advanced disease eventually develop resistance to therapy and may die of metastatic castration-resistant prostate cancer (mCRPC). A key challenge in the management of PCa is the clinical heterogeneity that is hard to predict using existing biomarkers. Defining molecular biomarkers for PCa that can reliably aid in diagnosis and distinguishing patients who require aggressive therapy from those who should avoid overtreatment is a significant unmet need. Mechanisms underlying the development of PCa are not confined to cancer epithelial cells, but also involve the tumor microenvironment. The crosstalk between epithelial cells and stroma in PCa has been shown to play an integral role in disease progression and metastasis. A number of key markers of reactive stroma has been identified including stem/progenitor cell markers, stromal-derived mediators of inflammation, regulators of angiogenesis, connective tissue growth factors, wingless homologs (Wnts), and integrins. Here, we provide a synopsis of the stromal-epithelial crosstalk in PCa focusing on the relevant molecular biomarkers pertaining to the tumor microenvironment and their role in diagnosis, prognosis, and therapy development.

IL-17F facilitates prostate cancer cell malignant phenotypes via activation of the PI3K/AKT signalling pathway

Prostate cancer (PCa) is known as one of the most common cancers in men all over the world. Previous studies have identified that the pro-inflammatory mediator interleukin-17F (IL-17F) aggravates the progression of several diseases. However, whether IL-17F plays a role in PCa is still lack of enough exploration. In this study, IL-17F expression was strikingly upregulated in PCa tissues. Treatment of IL-17F promoted cell viability at a dose-dependent manner. Further, functional assays were implemented by treatment of 100 ng/ml of IL-17F. Cell viability, proliferation, migration, invasion and stemness were promoted by 100 ng/ml of IL-17F. IL-17F increased the expression of p-PI3K and p-AKT in PCa cells, indicating that IL-17F might activate the PI3K/AKT signalling pathway in PCa cells. LY294002 (the inhibitor of the PI3K/AKT signalling pathway) could reverse the facilitating effects of IL-17F treatment on PCa cell viability, proliferation, migration, invasion and stemness. Taken together, current study revealed that IL-17F facilitated PCa cell malignant phenotypes via activation of the PI3K/AKT signalling pathway, offering a potential therapeutic target for PCa.

THBS4 silencing regulates the cancer stem cell-like properties in prostate cancer via blocking the PI3K/Akt pathway

BACKGROUND

Although thrombospondins 4 (THBS4) participates in controlling the biology of prostate cancer (PCa), the mechanism underlying this regulation remains unknown. Hence, this study aims to identify the regulatory effects of THBS4 on the PCa stem cell-like properties and the potential mechanism associated with the phosphatidylinositol 3'-kinase (PI3K)/protein kinase B (Akt) pathway.

METHODS

PCa stem cells were sorted and identified using flow cytometry and THBS4 expression in the identified PCa stem cells was measured using Western blot assay. THBS4 was overexpressed or silenced in PCa stem cells, following which, self-renewal, proliferation, cell cycle distribution, and apoptosis of PCa stem cells were assessed as well as tumorigenicity in vivo was evaluated. PI3K/Akt pathway inhibitor was applied to identify its involvement in the regulatory roles of THBS4 in PCa stem cells.

RESULTS

THBS4 was expressed at a higher level in PCa stem cells than in PCa cells. The overexpression of THBS4 promoted the self-renewal and proliferation, curbed the apoptosis of PCa stem cells, and enhanced the in vivo tumorigenicity, which was achieved by activating the PI3K/Akt pathway. On the contrary, short-hairpin RNA-mediated silencing of THBS4 exhibited suppressive effects on those cancer stem cell (CSC)-like properties and promotive effects on their apoptosis.

CONCLUSION

THBS4 silencing can impede the CSC-like properties in PCa via blockade of the PI3K/Akt pathway, which provides patients with PCa a new therapeutic target.

PreImplantation Factor immunohistochemical expression correlates with prostate cancer aggressiveness

BACKGROUND

The PreImplantation Factor (PIF)-a peptide secreted by viable embryos-exerts autotrophic protective effects, promotes endometrial receptivity and controls trophoblast invasion. Synthetic PIF (sPIF) has both immune-protective and regenerative properties, and reduces oxidative stress and protein misfolding. PIF is detected by immunohistochemistry (IHC) in hyperplastic endometriotic lesions and advanced uterine cancer. sPIF reduces graft-versus-host disease while maintaining a graft-versus-leukemia effect.

METHODS

PIF detection in prostate cancer was assessed in 50 human prostate samples following radical prostatectomy using tumor-microarray-based IHC correlating PIF immune staining with Gleason score (GS) and cancer aggressiveness.

RESULTS

PIF was detected in moderate-to-high risk prostate cancer (GS 4+3 and beyond, prognostic groups 3 to 5). In prostate cancer (GS (WHO Grade Group (GG)5), PIF was detected in 50% of cases; in prostate cancer (GS 4+4 GG4), PIF was observed in 62.5% of cases; in prostate cancer (GS 4+3 GG3), PIF immunostaining was observed in 57.1% of cases. In prostate cancer, (GS 3+4 GG2) and (GS 3+3 GG1) cases where PIF staining was negative to weak, membranous staining was observed in 20% of cases (staining pattern considered negative). High-grade prostate intraepithelial neoplasia PIF positive stain in 28.57% of cases (6 of 21) was observed. In contrast, PIF was not detected in normal prostate glands. Importantly, sPIF added to the PC3 cell line alone or combined with prostate cancer fibroblast feeder-cells did not affect proliferation. Only when peripheral blood mononuclear cells were added to the culture, a minor increase in cell proliferation was noted, reflecting local proliferation control.

CONCLUSIONS

Collectively, PIF assessment could be a valuable, simple-to-use immunohistochemical biomarker to evaluate aggressiveness/prognosis in specimens from prostate cancer patients.

Cancer stem cell and mesenchymal cell cooperative actions in metastasis progression and hormone resistance in prostate cancer: Potential role of androgen and gonadotropin‑releasing hormone receptors (Review)

Prostate cancer (PCa) is the leading cause of male cancer‑associated mortality worldwide. Mortality is associated with metastasis and hormone resistance. Cellular, genetic and molecular mechanisms underlying metastatic progression and hormone resistance are poorly understood. Studies have investigated the local effects of gonadotropin‑releasing hormone (GnRH) analogs (used for androgen deprivation treatments) and the presence of the GnRH receptor (GnRH‑R) on PCa cells. Furthermore, cell subpopulations with stem‑like properties, or cancer stem cells, have been isolated and characterized using a cell culture system derived from explants of human prostate tumors. In addition, the development of preclinical orthotopic models of human PCa in a nonobese diabetic/severe combined immunodeficiency mouse model of compromised immunity has enabled the establishment of a reproducible system of metastatic progression in vivo. There is increasing evidence that metastasis is a complex process involving the cooperative actions of different cancer cell subpopulations, in which cancer stem‑like cells would be responsible for the final step of colonizing premetastatic niches. It has been hypothesized that PCa cells with stemness and mesenchymal signatures act cooperatively in metastatic progression and the inhibition of stemness genes, and that overexpression of androgen receptor (AR) and GnRH‑R decreases the rate the metastasis and sensitizes tumors to hormone therapy. The aim of the present review is to analyze the evidence regarding this cooperative process and the possible influence of stem‑like cell phenotypes, AR and GnRH‑R in metastatic progression and hormone resistance. These aspects may represent an important contribution in the understanding of the mechanisms underlying metastasis and hormone resistance in PCa, and potential routes to blocking these processes, enabling the development of novel therapies that would be particularly relevant for patients with metastatic and castration‑resistant PCa.

Human Endogenous Formaldehyde as an Anticancer Metabolite: Its Oxidation Downregulation May Be a Means of Improving Therapy

Malignant cells are characterized by an increased content of endogenous formaldehyde formed as a by-product of biosynthetic processes. Accumulation of formaldehyde in cancer cells is combined with activation of the processes of cellular formaldehyde clearance. These mechanisms include increased ALDH and suppressed ADH5/FDH activity, which oncologists consider poor and favorable prognostic markers, respectively. Here, the sources and regulation of formaldehyde metabolism in cancer cells are reviewed. The authors also analyze the participation of oncoproteins such as fibulins, FGFR1, HER2/neu, FBI-1, and MUC1-C in the control of genes related to formaldehyde metabolism, suggesting the existence of two mutually exclusive processes in cancer cells: 1) production and 2) oxidation and elimination of formaldehyde from the cell. The authors hypothesize that the study of the anticancer properties of disulfiram and alpha lipoic acid - which affect the balance of formaldehyde in the body - may serve as the basis of future anticancer therapy.

Oncological effect of palliative transurethral resection of the prostate in patients with advanced prostate cancer: a propensity score matching study

PURPOSE

We investigated the oncologic effect of palliative transurethral resection of the prostate (pTURP) in patients with prostate cancer who received primary androgen deprivation therapy.

METHODS

We reviewed 614 patients, including 83 who underwent pTURP; those with incidental prostate cancer were excluded. Patients were divided into the TURP group and non-TURP group. Propensity score matching was performed for comorbidity, initial prostate-specific antigen (PSA), TNM stage, and Gleason score (GS). The Kaplan-Meier method was used to confirm castration-resistant prostate cancer (CRPC), cancer-specific survival (CSS), and overall survival (OS). Cox regression was performed to confirm factors affecting CSS.

RESULTS

Before matching, the TURP group had a worse TNM stage (p < 0.01) and GS (p = 0.028) and larger prostate volume (50.1 vs. 39.0 cc, p = 0.005) than the non-TURP group. The most common reason for pTURP was acute urinary retention. After matching, the TURP group showed worse outcomes in CRPC (p = 0.003), CSS (p = 0.003), and OS (p = 0.026). In multivariate analysis, factors for predicting CSS were a positive core percent [hazard ratio (HR) 1.015, p = 0.0272], GS (10 vs. ≤8; HR 6.716, p = 0.0008), and TURP within 3 months after biopsy (HR 2.543, p = 0.0482). The resection weight (HR 1.000, p = 0.9730), resection time (HR 1.000, p = 0.3670), and blood transfusion (HR 0.630, p = 0.1860) were not associated with CSS.

CONCLUSIONS

The oncologic effect of pTURP as cytoreductive operation seems to be limited. Patients who had to receive pTURP due to cancer-related symptoms, especially early necessity of pTURP (within 3 months after biopsy), showed worse clinical courses; therefore, they should be treated more carefully and actively.