Abstract C15: CRMP1 functions to suppress epithelial-mesenchymal transition and invasion capacity of prostate cancer cells

Collapsin response mediator protein 1 (CRMP1) is originally identified and characterized as a cytoplasmic phosphoprotein involved in the Semaphorin 3A (Sema3A)-regulated growth cone collapse during neural development, via its regulation of cytoskeleton dynamics, and then also characterized as an invasion suppressor in lung cancer. Thus, we hypothesize that CRMP1 may be involved in the epithelial-mesenchymal transition (EMT) process and invasion or metastasis via its regulation on cytoskeleton organization in prostate cancer cells. Results of immunohistochemistry study showed that CRMP1 exhibited a reduced expression pattern in high Gleason-scored clinical prostate cancer tissues. In vitro functional studies showed that stable CRMP1-knockdown could induce EMT in prostate cancer cells (DU145), while its ectopic expression could induce the reverse process mesenchymal-epithelial transition (MET) in both DU145 and PC-3 prostate cancer cells, as evidenced by significant change of cellular morphology and altered expression levels of epithelial and mesenchymal markers. Confocal immunofluorescence showed that reorganization of F-actin was seen after shRNA-mediated CRMP1-knockdown in DU145 cells. It was also revealed that CRMP1 overexpression could confer the resistance to TGF-β1- and Snail-induced EMT in prostate cells. Results of CRMP1 promoter-driven luciferase reporter and ChIP assays indicated that Snail was a direct transrepressor of CRMP1 gene, which showed a downregulation pattern in both prostate cancer cells (DU145) and immortalized prostatic epithelial cells (BPH1) with overexpression of Snail. Furthermore, wound healing and Matrigel invasion assays showed that CRMP1 could inhibit cell migration and invasion capacity in DU145 and PC-3 cells. Taken together, our findings suggest that CRMP1 could play a role in prostate cancer invasion and metastasis, via its regulation on EMT and MET process. (This work was supported by a Direct Grant for Research and a RGC-GRF grant 2009/2010)

Citation Format: Ganhui Cai, Shan Yu, Yanping Ji, Franky Leung Chan. CRMP1 functions to suppress epithelial-mesenchymal transition and invasion capacity of prostate cancer cells. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Invasion and Metastasis; Jan 20-23, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;73(3 Suppl):Abstract nr C15.

Abstract 950: Orphan nuclear receptor DAX1 exhibits suppressive effect on prostate cancer cell growth

The nuclear receptor superfamily comprises a large group of transcriptional factors involved broadly in many physiological functions including control of embryonic development and cellular homeostasis. In general, nuclear receptors can bind to specific DNA regulatory elements (REs) as homo- or heterodimers. DAX1 (Dosage sensitive sex reversal (DSS), adrenal hypoplasia congenita (AHC) critical region, on chromosome X, gene 1, NR0B1) is a unique ligand-independent orphan nuclear receptor, which lacks the conventional DNA-binding domain (DBD) and in some cases it functions as a coregulatory protein inhibiting the transcriptional activity of other nuclear receptors by forming heterodimers. Previous studies show that DAX1 may play an essential role in establishment and maintenance of the steroidogenic axis of development, maintenance of murine embryonic stem cell pluripotency and cancer development including ovarian, breast and endometrial cancers. A recent report identified the inverse correlation of immunoreactivity of DAX1 with Gleason score of prostate cancer. In a preliminary investigation of expression patterns of members of nuclear receptor superfamily in a panel of immortalized prostatic epithelial cell and prostate cancer cell lines by semi-quantitative and real-time PCR, we observed that DAX1 displayed a variable expression pattern with low or undetectable levels in most tested immortalized prostatic epithelial cell lines and prostate cancer cell lines (including the classical LNCaP and PC-3) but high levels in some prostate cancer cells (VCaP, DuCaP, RC-58T and DU145) and also an in vitro model of transformed immortalized human prostatic epithelial cells BPH-1CAFTD. In order to elucidate the possible functional roles of DAX1 in the prostate cancer cell growth regulation, we generated DAX1-stable expression clones in two prostate cancer cell lines, LNCaP and PC-3, which expressed low endogenous DAX1 levels, by retroviral transduction for in vitro growth characterization. Our results showed that overexpression of DAX1 in LNCaP and PC-3 cells suppressed their in vitro cell proliferation, single-cell colony formation and anchorage-independent growth capacity in soft agar. Moreover, luciferase reporter gene assay showed that DAX1 suppressed the ERRα-induced transactivation of VEGFA. Our results suggested that DAX1 might perform a suppressive growth regulatory role in prostate cancer cells. (Lin Jia is supported by a RGC Hong Kong-PhD Fellowship Scheme)

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 950. doi:1538-7445.AM2012-950

Chemopreventive effect of PSP through targeting of prostate cancer stem cell-like population

Recent evidence suggested that prostate cancer stem/progenitor cells (CSC) are responsible for cancer initiation as well as disease progression. Unfortunately, conventional therapies are only effective in targeting the more differentiated cancer cells and spare the CSCs. Here, we report that PSP, an active component extracted from the mushroom Turkey tail (also known as Coriolus versicolor), is effective in targeting prostate CSCs. We found that treatment of the prostate cancer cell line PC-3 with PSP led to the down-regulation of CSC markers (CD133 and CD44) in a time and dose-dependent manner. Meanwhile, PSP treatment not only suppressed the ability of PC-3 cells to form prostaspheres under non-adherent culture conditions, but also inhibited their tumorigenicity in vivo, further proving that PSP can suppress prostate CSC properties. To investigate if the anti-CSC effect of PSP may lead to prostate cancer chemoprevention, transgenic mice (TgMAP) that spontaneously develop prostate tumors were orally fed with PSP for 20 weeks. Whereas 100% of the mice that fed with water only developed prostate tumors at the end of experiment, no tumors could be found in any of the mice fed with PSP, suggesting that PSP treatment can completely inhibit prostate tumor formation. Our results not only demonstrated the intriguing anti-CSC effect of PSP, but also revealed, for the first time, the surprising chemopreventive property of oral PSP consumption against prostate cancer.

Abstract 4006: Orphan nuclear receptor tailless TLX performs an oncogenic function in prostate cancer cells via its promotion of androgen-independent growth and induction of epithelial – mesenchymal transition phenotype

The Tailless TLX gene (NR2E1), which was initially identified as a vertebrate homolog to the Drosophila terminal-gap gene tailless (tll), is an orphan nuclear receptor and functions mainly as a constitutive transcriptional repressor. Functional studies show that TLX plays important roles in the maintenance and self-renewal of both embryonic and adult neural stem cells. Transgenic mice with TLX overexpression show that in vivo ectopic TLX expression can lead to uncontrolled expansion of a subgroup of neural stem cells and cause initiation of glioma. In a preliminary screening of expression patterns of nuclear receptors in prostatic cell lines and clinical prostate cancer tissues, we identified that TLX transcripts were significantly overexpressed in many prostate cancer cell lines. Furthermore, by immunohistochemistry, increased TLX nuclear immunosignals were detected in high Gleason-scored (≥4) and also hormone-refractory (castration- and flutamide- resistant) prostate cancer, paired neoplastic human prostatic tissues, suggesting that TLX up-regulation may be positively associated with the advanced progression of prostate cancer. Based on these observations, we hypothesize that TLX may play growth regulatory roles in prostate cancer development. In order to elucidate the functional significance of TLX in prostate cancer growth, we generated stable TLX-infectants in a hormone-sensitive prostate cancer line LNCaP, which expressed low endogenous TLX levels, for growth phenotypic characterization. Our results showed that ectopic TLX expression could enhance the cell proliferation of LNCaP-TLX cells in either normal growth medium or medium with charcoal-stripped fetal bovine serum, accompanied with a decreased p21 expression. The LNCaP-TLX transduced clones, which expressed decreased androgen receptor (AR) and prostatic specific antigen (PSA) expressions, were less sensitive to AR agonist R1881 and antagonist bicalutamide, suggesting that LNCaP-TLX clones were less dependent on androgen but resistant to anti-androgen. Lastly, we also found that LNCaP-TLX infectants become apparently fusiform-shaped and expressed evaluated levels of two epithelial-mesenchymal transition (EMT) markers, Twist and Vimentin, suggesting that an EMT phenotype was induced in LNCaP-TLX cells. Taken together, our results demonstrated for the first time orphan nuclear receptor TLX may play an oncogenic regulatory role in the advanced growth of prostate cancer.

(This study was supported by a Direct Grant for Research CUHK, project code 2041534)

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4006. doi:10.1158/1538-7445.AM2011-4006

Differential effects of estrogen and progesterone on potassium channels expressed in Xenopus oocytes

HYPOTHESIS

Potassium (K(+)) channel activation contributes in part to estrogen-mediated vasorelaxation. However, the underlying mechanism is still unclear. We hypothesize that estrogen increases K(+) currents via membrane-associated, non-genomic interaction and that steroid hormones have differential effects on different types of K(+) channels.

EXPERIMENTAL

Human large-conductance Ca(2+)-activated K(+) channels (BK(Ca)) and human voltage-gated K(+) channels (K(V1.5)) were expressed in Xenopus oocytes, and K(+) currents elicited by voltage clamp were measured.

RESULTS

Both 17beta-estradiol and BSA-conjugated 17beta-estradiol increased the BK(Ca) current in a concentration-dependent manner and this effect was abolished by tetraethylammonium ions and iberiotoxin (putative BK(Ca) channel blockers). 17beta-estradiol-stimulated increase in the BK(Ca) current was unaffected by treatment with ICI 182,780 (classic estrogen receptor antagonist), tamoxifen (estrogen receptor agonist/antagonist), actinomycin D (RNA synthesis inhibitor), or cycloheximide (protein synthesis inhibitor). In contrast, progesterone reduced the BK(Ca) current in the absence or presence of NS 1619 (BK(Ca) channel activator). Progesterone also inhibited 17beta-estradiol-stimulated increase in the BK(Ca) current. Finally, progesterone but not 17beta-estradiol reduced the K(V1.5) current.

CONCLUSIONS

The present results show that 17beta-estradiol stimulates BK(Ca) channels without affecting K(V1.5) channels. This effect is ICI 182,780-insensitive and is likely mediated via a membrane-bound binding site. Progesterone inhibits both BK(Ca)- and K(V1.5)-encoded currents. The present results suggest that inhibition of K(+) channels may contribute in part to its reported antagonism against 17beta-estradiol-mediated vascular relaxation via BK(Ca) channels.

Tamoxifen and estrogen attenuate enhanced vascular reactivity induced by estrogen deficiency in rat carotid arteries

Recent clinical trials showed that estrogen usage in postmenopausal women did not affect coronary heart disease incidence, in contrast to several laboratory studies showing that estrogen decreased vascular reactivity. We speculated that, in some arteries, estrogen deficiency enhances endothelial function to compensate for the increased vascular smooth muscle reactivity. In this study, we examined the role of endothelium-derived vasoactive factors and the influence of in vivo estrogen and/or tamoxifen treatment on vascular reactivity of estrogen-deficient rats. Common carotid arteries were isolated from sham-operated (control), ovariectomized (Ovx), estrogen- or tamoxifen-treated Ovx rats, and Ovx rats co-treated with estrogen and tamoxifen. U46619 or phenylephrine induced similar contractions in endothelium-intact rings from all groups. Interestingly, removal of endothelium unmasked enhanced contractions in Ovx rats, which was prevented by estrogen, tamoxifen, or estrogen+tamoxifen treatment. Contractions to high K(+) were higher in both endothelium-intact and endothelium-denuded arteries from Ovx rats. Estrogen or tamoxifen treatment normalized high K(+)-induced contraction. A gap junction blocker, 18alpha-glycyrrhetinic acid, revealed enhanced contractions to U46619 in the absence or presence of l-NNA. Western blotting showed enhanced expressions of gap junctional connexin 43 in Ovx group. This study suggests that ovariectomy increases functional expression of gap junction-mediated endothelium-derived hyperpolarizing factor. Also, vascular effects of ovariectomy can be reversed by estrogen, tamoxifen or estrogen+tamoxifen treatment, suggesting that tamoxifen confers estrogenic effects in the vascular system.

Epigenetic silencing of cellular retinol-binding proteins in nasopharyngeal carcinoma

Aberrant retinoid signaling in human cancers is extending from the nucleus to the cytoplasm. Recently, we have demonstrated frequent epigenetic inactivation of a retinoic acid receptor (RAR), RARbeta2, in nasopharyngeal carcinoma (NPC). To further explore targets contributing to aberrant retinoid signaling in NPC, the expression of cellular retinol-binding proteins (CRBPs), cellular retinoic acid-binding proteins (CRABPs), RARs, and retinoid X receptors (RXRs) was examined. Apart from RARbeta2, transcriptional silencing of two CRBPs, CRBPI and CRBPIV, was observed in NPC cell lines and xenografts. Hypermethylation of CRBPI and CRBPIV CpG islands was found to be closely correlated with the loss of expression. Treatment with the DNA methyltransferase inhibitor, 5-aza-2'-deoxycytidine, resulted in reexpression of CRBP1 and CRBPIV gene expression in NPC cell lines. Both CRBPI and CRBPIV hypermethylations were also observed in 43/48 (87.8%) and 26/48 (54.2%) primary NPC tumors, respectively. Here, we reported for the first time that CRBPIV was transcriptionally inactivated by promoter hypermethylation in human cancer. Simultaneous methylation of CRBPI, CRBPIV, and RARbeta2 was commonly found in NPC primary tumors. Our findings implied that epigenetic disruption of the CRBPs, CRBPI and CRBPIV, is important in NPC tumorigenesis and may contribute to the loss of retinoic acid responsiveness in cancer.

The relaxant effect of urocortin in rat pulmonary arteries

Urocortin is a potent vasodilator, which plays physiological or pathophysiological roles in systemic circulation. However, little is known about its action on pulmonary circulation. The present study was aimed to characterize some cellular mechanisms underlying the relaxant effect of urocortin in isolated rat pulmonary arteries. Changes in isometric tension were measured on small vessel myographs. Urocortin inhibited U46619-induced contraction with reduction of the maximal response. Urocortin-induced relaxation was independent of the presence of endothelium. Inhibitors of nitric oxide (NO)-dependent dilator, NG-nitro-L-arginine methyl ester or 1H-[1,2,4]oxadizolo[4,3-a]quinoxalin-1-one, did not affect the relaxation. Astressin (100-500 nM), a corticotropin-releasing factor (CRF) receptor antagonist and KT5720, a protein kinase A (PKA) inhibitor reduced urocortin-induced relaxation. Urocortin produced less relaxant effect in 30 mM K+- than U46619-contracted arterial rings. Urocortin did not reduce CaCl2-induced contraction in 60 mM K+-containing solution. Ba2+ (100-500 microM) but not other K+ channel blockers reduced the relaxant responses to urocortin. Urocortin also relaxed the rings preconstricted by phorbol 12,13-diacetae in normal Krebs solution while this relaxation was less in a Ca2+-free solution. Our results show that urocortin relaxed rat pulmonary arteries via CRF receptor-mediated and PKA-dependent but endothelium/NO or voltage-gated Ca2+ channel-independent mechanisms. Stimulation of Ba2+-sensitive K+ channel may contribute to urocortin-induced relaxation. Finally, urocortin relaxed pulmonary arteries partly via inhibition of a PKC-dependent contractile mechanism.

Silencing of the retinoid response gene TIG1 by promoter hypermethylation in nasopharyngeal carcinoma

Tazarotene-induced gene 1 (TIG1) and Tazarotene-induced gene 3 (TIG3) are retinoid acid (RA) target genes as well as candidate tumor suppressor genes in human cancers. In our study, we have investigated the expression of TIG1 and TIG3 in nasopharyngeal carcinoma (NPC). Loss of TIG1 expression was found in 80% of NPC cell lines and 33% of xenografts, whereas TIG3 was expressed in all NPC samples and immortalized nasopharyngeal epithelial cells. In order to elucidate the epigenetic silencing of TIG1 in NPC, the methylation status of TIG1 promoter was examined by genomic bisulfite sequencing and methylation-specific PCR (MSP). We have detected dense methylation of TIG1 5'CpG island in the 5 TIG1-negative NPC cell lines and xenograft (C666-1, CNE1, CNE2, HONE1 and X666). Partial methylation was observed in 1 NPC cell line HK1 showing dramatic decreased in TIG1 expression. Promoter methylation was absent in 2 TIG1-expressed NPC xenografts and the normal epithelial cells. Restoration of TIG1 expression and unmethylated alleles were observed in NPC cell lines after 5-aza-2'-deoxycytidine treatment. Moreover, the methylated TIG1 sequence was detected in 39 of 43 (90.7%) primary NPC tumors by MSP. In conclusion, our results showed that TIG1 expression is lost in the majority of NPC cell lines and xenografts, while promoter hypermethylation is the major mechanism for TIG1 silencing. Furthermore, the frequent epigenetic inactivation of TIG1 in primary NPC tumors implied that it may play an important role in NPC tumorigenesis.

Differential regulation of K+ and Ca2+ channel gene expression by chronic treatment with estrogen and tamoxifen in rat aorta

The beneficial effect of estrogen on the vascular system is partly associated with its ability to reduce vascular contractility. Estrogen acutely activates large-conductance Ca(2+)-activated K(+) channel (BK(Ca)) and inhibits L-type voltage-gated Ca(2+) channel (VGCC) in vascular smooth muscle cells. However, a long-term influence of estrogen, estrogen deficiency, or selective estrogen receptor modulators on gene expression of these ion channels is unclear. This study was therefore aimed to determine the relative mRNA expression levels of alpha- and beta-subunits of BK(Ca), K(V)1.5 subtype of delayed rectifier K(+) channel (K(V)), and alpha(1C) subunit of L-type VGCC in endothelium-denuded aortas from female rats by a semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) analysis. Rats were divided into four experimental groups: (i) sham-operated control, (ii) ovariectomized, (iii) ovariectomized with 17 beta-estradiol treatment and (iv) ovariectomized with tamoxifen treatment. The results showed that ovariectomy decreased the mRNA expression of K(V)1.5 while it increased the mRNA expression of alpha(1C) subunit of L-type VGCC. Ovariectomy-induced modulation of gene expression of these ion channels was completely prevented in ovariectomized rats receiving chronic treatment with estrogen or tamoxifen. In contrast, the expression levels of genes encoding both alpha- and beta-subunits of BK(Ca) remained the same in the four animal groups. The present study has provided the first line of evidence suggesting the long-term beneficial effects of estrogen and tamoxifen therapy on vascular ion channel expressions, which may be an important mechanism by which the favorable modulation of vessel tone by estrogen or selective estrogen receptor modulators is mediated.

Nickel inhibits urocortin-induced relaxation in the rat pulmonary artery

Urocortin relaxes rat pulmonary arteries partly through a cyclic AMP-dependent but Ca(2+) channel-independent mechanism. However, other participating mechanisms are relatively unknown. The present study was designed to examine whether the forward mode of Na(+)-Ca(2+) exchangers play a role in the relaxant responses to urocortin in isolated rat small pulmonary arteries. Endothelium-denuded rings were mounted on small vessel myographs for measurement of changes in isometric tension. Urocortin inhibited 9,11-dideoxy-11alpha,9alpha-epoxy-methanoprostaglandin F(2alpha) (U46619)-induced contraction in a concentration-dependent manner and this inhibition was reversed by astressin, a corticotropin-releasing factor receptor antagonist. Micromolar concentrations of nickel (Ni(2+)) chloride, a putative inhibitor of the Na(+)-Ca(2+) exchanger, reduced the relaxant responses to urocortin. Urocortin-induced relaxation was abolished in a Na(+)-free solution, a condition that eliminates influence of the forward mode of Na(+)-Ca(2+) exchanger. In contrast, the relaxant responses to atrial natriuretic peptide or forskolin were unaffected by Ni(2+) or with removal of extracellular Na(+). The present results provide indirect evidence suggesting that stimulation of Na(+)-Ca(2+) exchangers may contribute to urocortin-induced endothelium-independent pulmonary artery relaxation.

Expression of olfactory-type cyclic nucleotide-gated channel (CNGA2) in vascular tissues

Cyclic nucleotide-gated (CNG) ion channels are Ca2+-permeable nonselective cation channels that are directly gated by the binding of cAMP or cGMP. Previous studies have identified the expression of CNGA1 channels in vascular endothelial cells. The opening of CNG channels is expected to result in a rise in endothelial cytosolic Ca2+, which may trigger multiple physiological changes. In the present study, we extensively studied the expression pattern of the functional subunit of olfactory-type CNG channels (CNGA2) in vascular tissues. Northern blot analysis detected a transcript of approximately 2.6 kb in mRNA isolated from rat aorta. RT-PCR amplified a 582-bp CNGA2 fragment from RNA samples isolated from rat aorta, bovine endothelia cell CCL-209, and rat smooth muscle cell A7r5. Furthermore, in situ hybridization and immunohistochemistry revealed that CNGA2 mRNA and proteins were expressed in the endothelium and smooth muscle layers of human coronary and cerebral arteries. In conclusion, our study indicates that CNGA2 channels are widely expressed in vascular tissues across different species. These results suggest a potential ubiquitous role of CNGA2 channels in mediating Ca2+ influx in vascular cells.

MRI of Neonatal Encephalopathy

We present the magnetic resonance imaging (MRI) findings in neonatal encephalopathy, including hypoxic-ischaemic encephalopathy, perinatal/neonatal stroke, metabolic encephalopathy from inborn errors of metabolism, congenital central nervous system infections and birth trauma. The applications of advanced MRI techniques, such as diffusion-weighted imaging and magnetic resonance spectroscopy are emphasized.

Persistent adrenal enhancement may be the earliest CT sign of significant hypovolaemic shock

AIM

To report two cases of intense and persistent adrenal enhancement on computed tomography (CT) examinations of the abdomen.

MATERIALS AND METHODS

Two patients presented with septic shock, one due to pyogenic liver abscess and the other strangulated obturator hernia with gangrenous bowel. Both patients were resuscitated with fluid before undergoing unenhanced and enhanced CT.

RESULTS

In both patients intravascular volume was not reduced as evident by normal calibre of the aorta and inferior vena cava. One patient had abnormal enhancement pattern in the liver and kidneys, suggesting hypoperfusion. The other patient had normal enhancement pattern of the other abdominal viscera. Both patient subsequently died with multi-organ failure.

CONCLUSION

We propose that adrenal enhancement may be a sign of hyperperfusion in early stage of shock due to the crucial role of the adrenal glands in this clinical situation. This may not persist with further circulatory compromise due to vasoconstriction. If confirmed, its recognition has potential value of identifying a therapeutic window before irreversible shock set in.

CT in acute mesenteric ischaemia

Enhanced computed tomography (CT) is frequently performed for possible bowel ischaemia. It has the distinct advantage of possible detection of the causes of ischaemia. Radiologists therefore need to be familiar with the spectrum of diagnostic CT signs. We present the CT imaging findings in surgically proven cases of small bowel ischaemia. In addition to signs pertaining to the underlying aetiological pathology, bowel dilatation, bowel wall thickening, mural gas, occlusion of mesenteric vessels, ascites and infarct of other abdominal organs were observed.

Roles of cyclic AMP and Ca2+-activated K+ channels in endothelium-independent relaxation by urocortin in the rat coronary artery

OBJECTIVE

Urocortin possesses cardioprotective properties against the damaging effects of ischemia/reperfusion injury. Our previous study demonstrated that urocortin can induce both endothelium-dependent and -independent coronary relaxation. However, the mechanisms thereby urocortin triggers endothelium-independent relaxation have not been investigated. The present study aimed to examine the role of cyclic AMP and Ca(2+)-activated K(+) channels in the relaxant response to urocortin in the isolated endothelium-denuded rat left anterior descending coronary arteries.

METHODS

Changes in vessel tension were measured by using a force transducer built in a Multi Myograph System.

RESULTS

In 9,11-dideoxy-11alpha,9alpha-epoxy-methanoprostaglandin F(2alpha) (U46619)-contracted rings, urocortin-induced relaxation (pD(2): 8.40+/-0.04) was significantly reduced by cyclic AMP-dependent protein kinase (PKA) inhibitors, Rp-cAMPS triethylamine (Rp-cAMPS) and KT 5720. Treatment with the large-conductance Ca(2+)-activated K(+) channel blockers, iberiotoxin or tetraethylammonium ions (TEA(+)) attenuated urocortin-induced relaxation; this effect was abolished in the presence of 200 nmol/l KT 5720. In contrast, apamin (small-conductance Ca(2+)-activated K(+) channel blocker), glibenclamide (ATP-sensitive K(+) channel blocker), or BaCl(2) (inwardly rectifier K(+) channel blocker) had no effect. Urocortin-induced relaxation was reduced in rings contracted with increasing concentrations of extracellular K(+) (35 and 50 mmol/l). Treatment with TEA(+) or Rp-cAMPS inhibited the relaxant effect of urocortin in 35 mmol/l K(+)-contracted rings. Combined treatment with TEA(+) and Rp-cAMPS had no additional effect. Similarly, forskolin produced significantly less relaxant response in 50 mmol/l K(+)-contracted than U46619-contracted rings. Forskolin-induced relaxation was attenuated by pretreatment with 3 mmol/l TEA(+).

CONCLUSION

Urocortin relaxed the rat coronary artery in substantial part via activation of the vascular Ca(2+)-activated K(+) channels and this effect appears to be primarily mediated through PKA-dependent intracellular mechanisms.

Prostate targeting: PSP94 gene promoter/enhancer region directed prostate tissue-specific expression in a transgenic mouse prostate cancer model

To date, only a few prostate-specific vector genes have been tested for prostate targeting in gene therapy of prostate cancer (CaP). Current clinical trials of gene therapy of CaP utilize the only two available vector genes with a combination of a rat probasin promoter and a human PSA promoter sequence in an adenovirus vector to target CaP. There is an urgent need to establish additional vector gene systems to sustain and propagate the current research. Since PSP94 (prostate secretory protein of 94 amino acids) is one of the three most abundant proteins secreted from the human prostate and is generally considered to be prostate tissue-specific in both human and rodents, we performed a transgenic experiment to assess the promoter/enhancer region of PSP94 gene-directed prostate targeting. Firstly, a series of progressive deletion mutants of a 3.84 kb PSP94 gene promoter/enhancer region (including parts of the intron 1 sequence) linked with a reporter LacZ gene was constructed and assessed in vitro in cell culture. Next, transgenic mice were generated with two transgene constructs using the SV40 early region (Tag oncogene) as a selection marker. PSP94 gene promoter/enhancer region-directed SV40 Tag expression specifically in the mouse was demonstrated in three breeding lines (A, B, C, n = 374) by immunohistochemistry staining of Tag expression. Specific targeting to the prostate in the PSP94 gene-directed transgenic CaP model was characterized histologically by correlation of SV40 Tag-induced tumorigenesis (tumor grading) with puberty and age (10-32 weeks). Prostatic hyperplasia was observed as early as 10 weeks of age, with subsequent emergence of prostatic intraepithelial neoplasia (PIN) and eventually high grade carcinoma in the prostate. The PSP94 transgenic mouse CaP model was further characterized by its tumor progression and metastatic tendency at 20 weeks of age and also by its responsiveness and refractoriness to androgen manipulation. This study indicates that the PSP94 gene promoter/enhancer has the potential for prostate specific targeting and may ultimately be of use in gene therapy of CaP.

(-)epicatechin induces and modulates endothelium-dependent relaxation in isolated rat mesenteric artery rings

AIM

The present study was aimed to examine the role of endothelial nitric oxide in the relaxant response to green tea (-)epicatechin and its modulation of endothelium-mediated relaxation in the isolated rat mesenteric artery rings.

METHODS

Changes in the isometric tension were measured with Grass force-displacement transducers.

RESULTS

The (-)epicatechin-induced relaxation was largely dependent on the presence of intact endothelium and was reversed by NG-nitro-L-arginine methyl ester 10 micromol/L or methylene blue 10 micromol/L, the inhibitors of nitric oxide-mediated relaxation. L-Arginine at 1 mmol/L antagonized the effect of L-NAME or methylene blue. Pretreatment of endothelium-intact rings with (-)epicatechin 10 micromol/L enhanced the relaxation induced by endothelium-dependent vasodilator, acetylcholine, while this concentration did not influence the endothelium-independent relaxation induced by sodium nitroprusside in the endothelium-denuded artery rings.

CONCLUSION

The results indicate that the endothelium-dependent vasodilation by (-)epicatechin is mainly mediated through nitric oxide and low concentration of (-)epicatechin augments endothelium-dependent vasorelaxation in the rat mesenteric arteries.

Endothelium-dependent and -independent coronary relaxation induced by urocortin

Urocortin, a newly identified polypeptide, possesses cardiac effects. However, the underlying mechanism of its coronary action is still unclear. In the present study we investigated the possible role of endothelial nitric oxide and Ba2+-sensitive K+ channels in the endothelium-dependent relaxant response to urocortin in the isolated rat left anterior descending coronary arteries. Changes of vessel tone were measured in microvessel myographs. Urocortin produced both endothelium-dependent and -independent relaxation with IC50 of 2.52 nM and 16.5 nM, respectively. Denuation of endothelium decreased the relaxing potency of urocortin. In the endothelium-intact rings pretreated with 100 microM N(G)-nitro-L-arginine methyl ester (L-NAME) or 10 microM 1H-[1,2,4]oxadiazolo[4,2-alpha]quinoxalin-1-one (ODQ), the urocortin-induced relaxation was similar to that observed in endothelium-denuded rings. The relaxant response to urocortin was markedly reduced in endothelium-intact rings preconstricted by 35 mM K+. Pretreatment with 100 microM BaCl2 significantly reduced urocortin-induced relaxation without an effect on the maximum relaxation. Combined treatment with BaCl2 plus L-NAME did not produce additive inhibition. In contrast, BaCl2 did not alter urocortin-induced relaxation in the endothelium-denuded rings. In the endothelium-denuded rings, BaCl2 at 100 microM also inhibited nitric oxide donor-induced relaxation. In conclusion, our results suggest that urocortin-induced endothelium-dependent relaxation of rat coronary arteries is primarily mediated by endothelial nitric oxide and subsequent activation of Ba2+-sensitive K+ channels. The urocortin-induced endothelium-dependent relaxation appears to be cyclic GMP-dependent.

Imaging of peripheral PNET: common and uncommon locations

AIM

We present the imaging features of peripheral primitive neuroectodermal tumour (PNET) in eight children, highlighting the unusual locations of this tumour in three children.

MATERIALS AND METHODS

At presentation, the tumours were studied with magnetic resonance imaging (MRI; n = 6), computed tomography (CT; n = 7) and ultrasound (US; n = 1). The diagnoses were confirmed histologically (n = 8), immunohistochemically (n = 8), by cytogenetics (n = 3) and electron microscopy (n = 1). Correlation with gross pathology, histology, treatment and outcome were obtained.

RESULTS

The tumours were located in the chest wall (n = 2), shoulder, pelvis, small bowel mesentery, adrenal gland, dura mater and skin and subcutaneous tissue of the abdominal wall (n = 1 each). Peripheral PNET arising from the small bowel mesentery, adrenal gland and dura mater have not been previously reported in the English literature. The tumours were mainly large (mean size: 10.6 cm) and infiltrative. All tumours were heterogeneously hyperintense on T2-weighted MRI, heterogeneously iso/hypodense on CT and had variable contrast enhancement. Most tumours were heterogeneously hypointense to muscle on T1-weighted MRI. US showed a hypoechoic mass with a cystic component.

CONCLUSION

Peripheral PNET can occur in unusual locations. The clinical and imaging features of peripheral PNET are non-specific, making tissue diagnosis essential. PNET should be included in the differential diagnosis of aggressive soft tissue tumours in children.