Myosin VI is a modulator of androgen-dependent gene expression.

Myosin VI, one of the so-called unconventional myosins, is an actin-based molecular motor involved in intracellular vesicle and organelle transport. In human prostate, myosin VI is expressed in prostate epithelium. We examined the effect of myosin VI downregulation in the LNCaP human prostate cancer cell line using an RNA interference approach. Further, the expression of myosin VI in human prostate tissue was examined using immunohistochemistry. The expression of androgen receptor (AR) and E-cadherin was examined in myosin VI knocked-down cells and control cells. We determined 3H-testosterone uptake in the myosin knocked-down LNCaP cells. Next, we cotransfected LNCaP cells with the myosin VI-specific small interfering RNA (siRNA) duplex and an androgen-responsive luciferase reporter construct and then measured luciferase activity after androgen induction. To clarify whether myosin VI and the AR are interacting proteins, we performed immunoprecipitation studies using myosin VI and AR polyclonal antibodies in androgen-induced LNCaP cells. We confirmed previous results of myosin VI overexpression in human prostate cancer tissue, as in some cases malignant epithelium was more intensively stained than benign epithelium. We found that the expression of AR decreased as a result of myosin VI knock-down. Decreased myosin VI levels did not significantly influence the testosterone uptake of the LNCaP cell line. Instead, we noted a decreased activity of the androgen-regulated mouse mammary tumor virus promoter-reporter vector construct in LNCaP cells cotransfected with myosin VI siRNA duplexes. Finally, we detected the interaction between AR and myosin VI by immunoprecipitation. We propose that myosin VI is a modulator of androgen-dependent gene transcription via interaction with the AR. Thus, myosin VI is a potential therapeutic target for prostate cancer as it could be used as a modulator of AR-dependent gene expression.

The androgen receptor CAG repeat length polymorphism associates with prostate volume in Finnish men with benign prostatic hyperplasia.

The development of benign prostatic hyperplasia requires the presence of testicular androgens during prostate development, puberty, and ageing. We thus examined the association of three polymorphisms, namely, CYP3A5 6986A>G, CYP19A1 1531C>T, and androgen receptor (AR) gene CAG repeat length, which have previously been linked to the androgen pathway and with clinical characteristics of benign prostatic hyperplasia. Tissue samples from 262 consecutive prostate operations were used for genotyping. Prostate volumes and prostate-specific antigen values were collected from patient records. Linear regression analysis was performed to study the polymorphisms in an age-adjusted model. We did not find any association between the CYP3A5 6986A>G polymorphism and clinical characteristics of benign prostatic hyperplasia. Further, the previously published CYP19A1 1531C>T polymorphism association with an enlarged prostate could not be confirmed with this material. However, we detected an association between short AR gene CAG repeat length and a small prostate volume, which confirms a previous finding in the Finnish population. The data presented suggest a negligible role for the CYP3A5 6986A>G polymorphism in benign prostate enlargement in the Finnish population. However, the results presented do provide further evidence for potentially different genetic mechanisms behind benign prostatic hyperplasia in Finnish and other Caucasian populations. This is based on the conflicting results for AR gene CAG repeat length associations with benign prostatic hyperplasia found in published works.

Expression of cytosolic acetyl-CoA synthetase gene is developmentally regulated.

Acetyl-CoA synthetase (AceCS) provides acetyl-CoA for different physiological processes, such as fatty acid and cholesterol synthesis, as well as the citric acid cycle. We show here that the cytosolic isoform of this enzyme, AceCS1, is expressed during mouse development. In the embryonic stage E9.5 AceCS1 transcripts localize in the cephalic region. At E10.5 the cephalic expression intensifies and transcripts appear also in the spinal cord and in the dorsal root ganglions. During organogenesis AceCS1 is expressed in the liver from E11.5. The AceCS1 gene is expressed also in the testes from E12.5 onwards and expression localizes in the interstitial Leydig cells. In the ovaries, expression is transient and AceCS1 transcripts are detected from E13.5 to E15.5 in the ovarian interstitial component. In the kidneys AceCS1 transcripts appear in a subset of the renal tubules at E16.5 and remains in these structures in newborns. Hence, expression of AceCS1 is developmentally regulated suggesting a role for AceCS1 during embryogenesis.

Sorbitol dehydrogenase expression is regulated by androgens in the human prostate.

Sorbitol is an intermediate in the polyol pathway, which converts from glucose to fructose by sorbitol dehydrogenase (SORD). Androgens are essential for the development of prostate cancer. We studied castration-induced gene expression changes in the human prostate using the GeneChip array, and identified SORD as being androgen-regulated in the human prostate. A putative androgen-responsive regulatory region at the SORD 5' promoter was identified using promoter deletion constructs in a luciferase reporter assay in COS-7 cells. Chromatin immunoprecipitation assay was used to assess the binding of androgen receptor to suggested androgen responsive regulatory region. Finally, the expression of SORD in the human prostate was evaluated in 29 prostate tissue samples by immunohistochemistry. The expression of SORD decreased after castration. Androgen supplementation to the LNCaP prostate cancer cell line led to a 7.5-fold increase in SORD mRNA expression. Furthermore, a chromatin immunoprecipitation assay proved that the androgen receptor can bind to this putative androgen-responsive regulatory region. Finally, the expression of SORD in the human prostate was localised to epithelial cells of both benign and malignant prostate tissue by immunohistochemistry. In prostate cancer, increased immunostaining was associated with high Gleason patterns and high serum prostate-specific antigen concentrations. These results show that SORD is a novel androgen-regulated gene in the human prostate and suggest the need for more detailed analysis of the physiological role of SORD in the prostate.

Polyamines are involved in murine kidney development controlling expression of c-ret, E-cadherin, and Pax2/8 genes.

Polyamines play an important role in cell growth and differentiation. We studied changes in morphogenesis and the expression of the developmental control genes in the embryonic mouse kidney in response to polyamine depletion, using a kidney organ culture approach and reducing the polyamine pools with alpha-difluoromethylornithine (DFMO), an irreversible suicide inhibitor of ornithine decarboxylase (ODC). We found that inhibition of ODC results in a systematic kidney organogenesis phenotype, in that the DFMO-treated kidney specimens were of smaller size, had less epithelial ureteric bud branches, and their mesenchymal-derived tubule formation was retarded. These dysmorphologies were shown to be associated with changes in cell proliferation. Whole-mount in situ experiments revealed that inhibition of ODC causes increases in epithelial c-ret and E-cadherin and a decrease in mesenchymal Pax-8 expression, whereas levels of epithelial Wnt-11, mesenchymal GDNF, FoxD1, and Pax-2 transcripts remain unchanged. We studied regulation of the Pax-2 gene by analyzing a mouse line in which lacZ was driven by an 8.5 kb Pax-2 enhancer in the epithelial ureteric bud, and found that Pax-2 expression, as indicated by lacZ expression, increased after DFMO treatment. Transient transfection experiments in HEK 293 cells with the minimal Pax-2 promoter showed enhanced transcription upon reduction of the polyamine pools. We propose that ODC and polyamines have an important role in kidney organogenesis, being involved in the regulation of the expression of genes implicated in epithelial-mesenchymal tissue interactions.