Establishment and characterization of a prostate cancer cell line from a prostatectomy specimen for the study of cellular interaction.

Though human prostate cancer (PCa) heterogeneity can best be studied using multiple cell types isolated from clinical specimens, the difficulty of establishing cell lines from clinical tumors has hampered this approach. In this proof-of-concept study, we established a human PCa cell line from a prostatectomy surgical specimen without the need for retroviral transduction. In a previous report, we characterized the stromal cells derived from PCa specimens. Here, we characterized the epithelial cells isolated from the same tumors. Compared to the ease of establishing prostate stromal cell lines, prostatic epithelial cell lines are challenging. From three matched pairs of normal and tumor tissues, we established one new PCa cell line, HPE-15. We confirmed the origin of HPE-15 cells by short tandem repeat microsatellite polymorphism analysis. HPE-15 cells are androgen-insensitive and express marginal androgen receptor, prostate-specific antigen and prostate-specific membrane antigen proteins. HPE-15 expresses luminal epithelial markers of E-cadherin and cytokeratin 18, basal cell markers of cytokeratin 5 and p63 and neuroendocrine marker of chromogranin A. Interestingly, HPE-15 Cells exhibited no tumorigenicity in different strains of immune-deficient mice but can become tumorigenic through interaction with aggressive cancer cell types. HPE-15 cells can thus serve as an experimental model for the study of PCa progression, metastasis and tumor cell dormancy.

Retinoic acid activates monoamine oxidase B promoter in human neuronal cells.

Monoamine oxidase (MAO) B deaminates a number of biogenic and dietary amines and plays an important role in many biological processes. Among hormonal regulations of MAO B, we have recently found that retinoic acid (RA) significantly activates both MAO B promoter activity and mRNA expression in a human neuroblastoma BE(2)C cell line. RA activates MAO B promoter in both concentration- and time-dependent manners, which is mediated through retinoic acid receptor alpha (RARalpha) and retinoid X receptor alpha (RXRalpha). There are four retinoic acid response elements (RAREs) as identified in the MAO B 2-kb promoter, and mutation of the third RARE reduced RA-induced MAO B promoter activation by 50%, suggesting this element is important. Electrophoretic mobility shift analysis and chromatin immunoprecipitation assay demonstrated that RARalpha specifically binds to the third RARE both in vitro and in vivo. Moreover, transient transfection and luciferase assays revealed that Sp1 enhances but not essentially required for the RA activation of MAO B through two clusters of Sp1-binding sites in the MAO B promoter. RARalpha physically interacts with Sp1 via zinc finger domains in Sp1 as determined by co-immunoprecipitation assay. Further, RARalpha was shown to be recruited by Sp1 and to form a transcriptional regulation complex with Sp1 in the Sp1-binding sites of natural MAO B promoter. Taken together, this study provides evidence for the first time showing the stimulating effect of RA on MAO B and new insight into the molecular mechanisms of MAO B regulation by hormones.

Regulation of monoamine oxidase A by the SRY gene on the Y chromosome.

Monoamine oxidase A (MAO A), encoded by the X chromosome, catalyzes the oxidative deamination of monoamine neurotransmitters, such as serotonin, and plays a critically important role in brain development and functions. Abnormal MAO A activity has been implicated in several neuropsychiatric disorders, such as depression, autism, and attention deficit hyperactivity disorder, which show sexual dimorphism. However, the molecular basis for these disease processes is unclear. Recently, we found that MAO A was a putative target gene directly regulated by a transcription factor encoded by the sex-determining region Y (SRY) gene located on the Y chromosome. We demonstrated that SRY activates both MAO A-promoter and catalytic activities in a human male neuroblastoma BE(2)C cell line. A functional SRY-binding site in the MAO A core promoter was identified and validated by electrophoretic mobility shift and chromatin immunoprecipitation (ChIP) analyses. Coimmunoprecipitation and ChIP assays showed that SRY and Sp1 form a transcriptional complex and synergistically activate MAO A transcription. This is the first study demonstrating that the Y-encoded transcription factor SRY is capable of regulating an X-located gene, suggesting a novel molecular mechanism for sexual dimorphism in neural development, brain functions, and initiation/progression of neural disorders associated with MAO A dysfunction.

Keratin 13 expression reprograms bone and brain metastases of human prostate cancer cells.

Lethal progression of prostate cancer metastasis can be improved by developing animal models that recapitulate the clinical conditions. We report here that cytokeratin 13 (KRT13), an intermediate filament protein, plays a directive role in prostate cancer bone, brain, and soft tissue metastases. KRT13 expression was elevated in bone, brain, and soft tissue metastatic prostate cancer cell lines and in primary and metastatic clinical prostate, lung, and breast cancer specimens. When KRT13 expression was determined at a single cell level in primary tumor tissues of 44 prostate cancer cases, KRT13 level predicted bone metastasis and the overall survival of prostate cancer patients. Genetically enforced KRT13 expression in human prostate cancer cell lines drove metastases toward mouse bone, brain and soft tissues through a RANKL-independent mechanism, as KRT13 altered the expression of genes associated with EMT, stemness, neuroendocrine/neuromimicry, osteomimicry, development, and extracellular matrices, but not receptor activator NF-κB ligand (RANKL) signaling networks in prostate cancer cells. Our results suggest new inhibitors targeting RANKL-independent pathways should be developed for the treatment of prostate cancer bone and soft tissue metastases.