Biomedical subjects

Kati P Porkka

Publications and source records attributed to Kati P Porkka.

7 recordsLinked to original sources

PubMed2006

Genetic aberrations in prostate cancer by microarray analysis.

The aim of this study was to screen genetic as well as expression alterations in prostate cancer. Array comparative genomic hybridization (aCGH) to a 16K cDNA microarray was performed to analyze DNA sequence copy number alterations in 5 prostate cancer cell lines and 13 xenografts. The aCGH confirmed the previously implicated common gains and losses, such as gains at 1q, 7, 8q, 16p and 17q and losses at 2q, 4p/q, 6q, 8p, 13q, 16q, 17p and 18q, which have previously been identified by chromosomal CGH (cCGH). Because of the higher resolution of aCGH, the minimal commonly altered regions were significantly narrowed-down. For example, the gain of 8q was mapped to three independent regions, 8q13.3-q21.11, 8q22.2 and 8q24.13-q24.3. In addition, a novel recurrent gain at 9p13-q21 was identified. The concomitant expression analysis indicated that genome-wide DNA sequence copy number (gene dosage) was significantly associated with the expression level (p < 0.0001). The analyses indicated several individual genes whose expression was associated with the gene copy number. For example, gains of PTK2 and FZD6, were associated with the increased expression, whereas losses of TNFRSF10B (alias DR5) and ITGA4 with decreased expression. In conclusion, the aCGH mapping data will aid in the identification of genes altered in prostate cancer. The combined expression and copy number analysis suggested that even a low-level copy number change may have significant effect on gene expression, and thus on the development of prostate cancer.

Animals↗

PubMed2005

Dual-specificity phosphatase 1 and serum/glucocorticoid-regulated kinase are downregulated in prostate cancer.

Inactivation of tumor suppressor genes through deletion, mutation and epigenetic silencing has been shown to occur in cancer. In our study, we combined DNA demethylation and histone deacetylation inhibition treatments with suppression subtraction hybridization (SSH) and cDNA microarrays to identify potentially epigenetically downregulated genes in PC-3 prostate cancer cell line. We found 11 genes whose expression was upregulated after relieving epigenetic regulation. Expression of 3 genes [dual-specificity phosphatase 1 (DUSP1), serum/glucocorticoid regulated kinase (SGK) and spermidine/spermine N1-acetyltransferase (SAT)] was subsequently studied in clinical sample material using real-time quantitative RT-PCR and immunohistochemistry. The DUSP1 and SGK mRNA expression was lower in hormone-refractory prostate carcinomas compared to benign prostate hyperplasia (BPH) or untreated prostate carcinomas. BPH, normal prostate and high-grade prostate intraepithelial neoplasia (PIN) expressed high levels of DUSP1 and SGK proteins. Ninety-two percent and 48% of the prostate carcinomas showed almost complete lack of DUSP1 and SGK proteins, respectively, indicating common downregulation of these genes. The genomic bisulphite sequencing did not reveal dense hypermethylation in the promoter regions of either DUSP1 or SGK. In conclusion, the data suggest that downregulation of DUSP1 and SGK is an early event and could be important in the tumorigenesis of prostate cancer.

Base Sequence↗

PubMed2004

Expression of androgen receptor coregulators in prostate cancer.

PURPOSE: The androgen receptor (AR)-mediated signaling pathway seems to be essentially involved in the development and progression of prostate cancer. In vitro studies have shown that altered expression of AR coregulators may significantly modify transcriptional activity of AR, suggesting that these coregulators could also contribute to the progression of prostate cancer. Here, our goal was to assess alterations in the expression of the AR coregulators in prostate cancer in vivo. EXPERIMENTAL DESIGN: The expression of 16 AR coactivators and corepressors (SRC1, beta-catenin, TIF2, PIAS1, PIASx, ARIP4, BRCA1, AIB1, AIB3, CBP, STAT1, NCoR1, AES, cyclin D1, p300, and ARA24) was measured in prostate cancer cell lines, xenografts, and clinical prostate tumor specimens by using real-time quantitative reverse transcription-PCR. In addition, gene copy number of SRC1 was analyzed by fluorescence in situ hybridization. RESULTS: Both AR-positive and AR-negative cell lines and xenografts expressed the coregulators. Most of the coregulators studied were expressed at equal levels in benign prostatic hyperplasia and untreated and hormone-refractory carcinomas. However, the expression of PIAS1 and SRC1 was significantly (P = 0.048 and 0.017, respectively) lower in hormone-refractory prostate tumors than in untreated prostate tumors. No overexpression of the coregulators was found in the clinical material. Paradoxically, the SRC1 gene was found to be amplified and highly expressed in a LuCaP 70 prostate cancer xenograft. CONCLUSIONS: These findings suggest that the decreased expression of PIAS1 and SRC1 could be involved in the progression of prostate cancer. In addition, gene amplification of SRC1 in one of the xenografts implies that, in some tumors, genetic alteration of SRC1 may provide a growth advantage.

Animals↗

PubMed2004

RAD21 and KIAA0196 at 8q24 are amplified and overexpressed in prostate cancer.

To detect genes that are overexpressed in prostate cancer, a subtracted cDNA library was first constructed from the PC-3 cell line and subsequently screened by using cDNA microarray hybridization. Sixty-eight genes were found to be overexpressed (ratio>3) in PC-3. Half of these genes were in chromosomal regions, which, using comparative genomic hybridization, we previously showed to be gained in PC-3. Subsequently, the expression and copy number of selected genes were studied by quantitative RT-PCR and fluorescence in situ hybridization in prostate cancer cell lines, xenografts, and clinical tumor specimens of benign prostate hyperplasia and untreated as well as hormone-refractory prostate carcinomas. Two genes from chromosomal region 8q24-RAD21 and KIAA0196-showed increased expression in clinical prostate carcinomas and were also amplified in 30-40% of xenografts and hormone-refractory tumors. In addition, the expression of KIAA0196 was significantly (P=0.0051) higher in tumors with the gene amplification than in those without it. The data suggest that KIAA0196 and possibly RAD21 are putative target genes for the common amplification of 8q23-24 in prostate cancer.

Blotting, Northern↗

PubMed2004

Molecular mechanisms of prostate cancer.

During the last ten years our knowledge of genetic alterations in prostate cancer has significantly increased. For example, several chromosomal loci possibly harboring predisposing or somatically mutated genes have been suggested. Still, we lack the comprehensive molecular model for the development and progression of prostate cancer. Only a few genes have been found to be aberrant in a significant proportion of prostate cancer. These include GSTP1, PTEN, TP53, and AR. Thus, they are natural targets for new treatment strategies.

Acyltransferases↗

PubMed2003

Human pHyde is not a classical tumor suppressor gene in prostate cancer.

A novel putative tumor suppressor gene, pHyde, was recently cloned from rat prostate. The rat gene has been shown to inhibit prostate cancer cell proliferation both in vitro and in vivo. However, the role of human pHyde in prostate cancer has not been studied before. Here, we analyzed human prostate cancer cell lines (LNCaP, DU145, PC-3, 22Rv1), xenografts (LuCaP 23.1, 35, 41, 49, 58, 69, 70 and 73) and clinical prostate carcinomas for genetic alterations and expression of pHyde. The expression of pHyde in normal human tissues as well as in prostate cancer was studied by Northern analysis and real-time quantitative RT-PCR. It was ubiquitously expressed in all normal tissues analyzed. Although, the expression was significantly (p=0.007) lower in poorly differentiated than in well and moderately differentiated carcinomas, there were no differences in the expression levels between benign prostate hyperplasia, untreated primary and recurrent hormone-refractory prostate carcinomas (p=0.607). Altogether, missense mutations were detected in 2 out of 68 samples studied ( approximately 3%) by denaturing high-performance liquid chromatography (DHPLC) and sequencing. One of the samples with the mutation also exhibited a loss of a gene copy by fluorescence in situ hybridization (FISH). This was the only sample that exhibited a genetic alteration in both alleles, suggesting that the human pHyde is not a classical prostate tumor suppressor gene. The reduced expression of the gene found in some tumors warrant further studies.

Animals↗

PubMed2002

Cloning and characterization of a novel six-transmembrane protein STEAP2, expressed in normal and malignant prostate.

By using subtraction and cDNA array hybridizations, we recently identified an anonymous transcript that was differentially expressed in benign prostate hyperplasia and prostate cancer cell line PC-3. Here, we report the cloning of the full-length cDNA of the gene, designated STEAP2 (six-transmembrane epithelial antigen of the prostate 2). The gene is located at the chromosomal region 7q21 and encodes for a 490-amino acid protein with six predicted transmembrane domains and is predominantly expressed in prostate epithelial cells. Green fluorescent protein fusion construct indicated that the STEAP2 protein is localized mainly in the plasma membrane. Real-time quantitative RT-PCR showed that the gene is expressed at levels more than 10 times higher in normal prostate than in other tissues studied. Of the prostate cancer cell lines, STEAP2 was expressed in significant levels only in androgen-responsive LNCaP. The expression of STEAP2 was significantly higher (p = 0.002) in both untreated primary and hormone-refractory prostate carcinomas than in benign prostate hyperplasias, suggesting that it may be involved in the development of prostate cancer. As a cell-surface antigen, STEAP2 is a potential diagnostic or therapeutic target in prostate cancer.

Amino Acid Sequence↗