The complex roles of Wnt antagonists in RCC

Renal cell carcinoma (RCC) is the most lethal of all the genitourinary cancers, as it is generally refractory to current treatment regimens, including chemotherapy and radiation therapy. Targeted therapies against critical signaling pathways associated with RCC pathogenesis, such as vascular endothelial growth factor, von Hippel-Lindau tumor suppressor and mammalian target of rapamycin, have shown limited efficacy so far. Thus, Wnt signaling, which is known to be intricately involved in the pathogenesis of RCC, has attracted much interest. Several Wnt signaling components have been examined in RCC, and, while studies suggest that Wnt signaling is constitutively active in RCC, the molecular mechanisms differ considerably from other human carcinomas. Increasing evidence indicates that secreted Wnt antagonists have important roles in RCC pathogenesis. Considering these vital roles, it has been postulated--and supported by experimental evidence--that the functional loss of Wnt antagonists, for example by promoter hypermethylation, can contribute to constitutive activation of the Wnt pathway, resulting in carcinogenesis through dysregulation of cell proliferation and differentiation. However, subsequent functional studies of these Wnt antagonists have demonstrated the inherent complexities underlying their role in RCC pathogenesis.     

MicroRNA-205 inhibits Src-mediated oncogenic pathways in renal cancer

The Src family of protein kinases (SFK) plays key roles in regulating fundamental cellular processes, including cell growth, differentiation, cell shape, migration, and survival, and specialized cell signals in various malignancies. The pleiotropic functions of SFKs in cancer make them promising targets for intervention. Here, we sought to investigate the role of microRNA-205 (miR-205) in inhibition of Src-mediated oncogenic pathways in renal cancer. We report that expression of miR-205 was significantly suppressed in renal cancer cell lines and tumors when compared with normal tissues and a nonmalignant cell line and is correlated inversely with the expression of SFKs. miR-205 significantly suppressed the luciferase activity of reporter plasmids containing the 3'-UTR (untranslated region) sequences complementary to either Src, Lyn, or Yes, which was abolished by mutations in these 3'-UTR regions. Overexpression of miR-205 in A498 cells reduced Src, Lyn, and Yes expression, both at mRNA and protein levels. Proliferation of renal cancer cells was suppressed by miR-205, mediated by the phospho-Src-regulated ERK1/2 pathway. Cell motility factor FAK (focal adhesion kinase) and STAT3 activation were also inhibited by miR-205. Transient and stable overexpression of miR-205 in A498 cells resulted in induction of G?/G? cell-cycle arrest and apoptosis, as indicated by decreased levels of cyclin D1 and c-Myc, suppressed cell proliferation, colony formation, migration, and invasion in renal cancer cells. miR-205 also inhibited tumor cell growth in vivo. This is the first study showing that miR-205 inhibits proto-oncogenic SFKs, indicating a therapeutic potential of miR-205 in the treatment of renal cancer.     

Wnt antagonist DKK1 acts as a tumor suppressor gene that induces apoptosis and inhibits proliferation in human renal cell carcinoma

The functional significance of Wnt antagonist DKK1 has not been investigated in renal cell carcinoma (RCC). Therefore, we hypothesized that DKK1 may be a tumor suppressor gene and is epigenetically silenced, thus decreased DKK1 may cause progression of RCC. To assess the function of DKK1, we established stable DKK1 transfected cells and monitored them regarding cell viability, colony formation, apoptosis, cell cycle, and invasive capability. RCC cell lines had decreased levels of DKK1, which were increased after treatment with 5‐Aza‐2′‐deoxycytidine and trichostatin A. In chromatin immunoprecipitation assay, the level of dimethyl H3K9 and trimethyl H3K27 was decreased after 5‐Aza‐2′‐deoxycytidine/trichostatin A treatment in RCC cell lines. Increased methylation was also associated with higher pathological stages in primary RCC tissues. T‐cell factor/lymphoid enhancer factor activity and nuclear beta‐catenin expression were not changed in DKK1 transfectants. Also the expression of cyclinD1 and c‐Myc was not changed in DKK1 transfectants. These results suggest that DKK1 may not be involved in the beta‐catenin dependent pathway. We also evaluated the expression of various related genes. Cleaved caspase3, p53, p21 and puma expression were significantly upregulated in the DKK1 transfected cells. The population of apoptotic cells was increased in stable DKK1 cells and tumor growth suppression was also observed in nude mice with DKK1 transfected cells. In conclusion, this is the first report to show that DKK1 expression is epigenetically silenced in kidney cancer and its reexpression induces apoptosis and cell cycle arrest in RCC.     

Secreted frizzled‐related protein‐5 is epigenetically downregulated and functions as a tumor suppressor in kidney cancer

Secreted frizzled‐related protein‐5 (sFRP‐5) has been identified as 1 of the secreted antagonists that bind Wnt protein. However, the functional significance of sFRP‐5 in renal cell cancer (RCC) has not been reported. We hypothesized that sFRP‐5 may be epigenetically downregulated through DNA methylation and histone modification and function as a tumor suppressor gene in RCC. Using tissue microarray and real‐time RT‐PCR, we found that sFRP‐5 was significantly downregulated in kidney cancer tissues and cell lines, respectively. DNA bisulfite sequencing of the sFRP‐5 promoter region in RCC cell lines showed it to be densely methylated, whereas there was few promoter methylation in normal kidney. The sFRP‐5 expression was restored and the acetylation of H3 and H4 histones associated with the sFRP‐5 promoter region were significantly increased after treatment with demethylation agent (5‐Aza‐dc) and histone deacetylase inhibitor (TSA). When RCC cells were transfected with the sFRP‐5 gene, significant inhibition of anchorage independent colony formation and cell invasion were observed compared to controls. The sFRP‐5 transfection also significantly induced apoptosis in RCC cells. In conclusion, this is the first report documenting that the sFRP‐5 is downregulated by promoter methylation and histone acetylation and functions as a tumor suppressor gene by inducing apoptosis in RCC cells.     

Functional improvement in spinal cord injury-induced neurogenic bladder by bladder augmentation using bladder acellular matrix graft in the rat

Spinal cord injury (SCI) rostral to the lumbosacral level causes bladder hyperreflexia and detrusor-sphincter dyssynergia (DSD), which are accompanied by bladder hypertrophy. We hypothesize that bladder augmentation using a bladder acellular matrix graft (BAMG) can improve the function of SCI-mediated neurogenic bladder. In female rats (n = 35), SCI was induced by transection of the spinal cord at the lower thoracic level. Eight weeks following spinalization, bladder augmentation using BAMG was performed after hemicystectomy of the hypertrophic bladder. Cystometrography was performed at 8 weeks after spinalization and again at 8 weeks after augmentation. Several urodynamic parameters were measured and the grafted bladder was histologically evaluated. Thirty one rats were alive 8 weeks after spinalization. Twenty two (71%) rats developed hyperreflexic bladders and nine (29%) rats had underactive bladders before bladder augmentation. Twenty six rats survived until 8 weeks after augmentation. Urodynamic parameters showed improvement in some bladder functions in both hyperreflexic and underactive bladders after augmentation. In addition, bladder compliance was increased in hyperreflexic bladders and decreased in underactive bladders. Bladder augmentation decreased bladder capacity in high-capacity rats and increased it in low-capacity rats. Histological evaluation showed complete regeneration of BAMG in SCI-induced neurogenic bladder at 8 weeks after augmentation. This is the first report suggesting that the voiding function in SCI-induced neurogenic bladder can be improved by augmentation using BAMG. Improved voiding function was accompanied by histological regeneration of BAMG.     

Criterions for selection of patients for, and results of, a new technique for construction of the modified Blalock-Taussig shunt

BACKGROUND: We describe alternative surgical techniques for construction of systemic-to-pulmonary arterial shunts, and propose criterions for their application in selected patients. PATIENTS AND METHODS: We constructed a variety of modified systemic-to-pulmonary arterial shunts, using polytetrafluoroethylene grafts, in 92 selected patients with cyanotic congenital heart disease and anomalies of the aortic arch and systemic veins. Their age ranged from 7 days to 3.6 years, with a mean of 7.08 months. We performed 88 operations through a thoracotomy. Of this cohort, 60 patients underwent a second-stage operation, with 15 receiving a superior cavopulmonary connection, 16 a total cavopulmonary connection, and 29 proceeding to biventricular repair after a mean interval of 15.6 months. We have 21 patients awaiting their second or final stage of palliation. RESULTS: There were five early (5.4%) and six late deaths (6.8%), two of which were related to construction of the shunts. At a mean follow-up of 45.29 months, the increase in diameter of pulmonary trunk and its right and left branches was uniform and significant (p value less than 0.001). Pulmonary arterial distortion requiring correction at the time of second-stage operation was observed in 5 patients (6.1%). Adequate overall palliation was achieved in 98% of the cohort at 8 months, 91% at 12 months, and 58% at 18 months. CONCLUSIONS: Patients with a right- or left-sided aortic arch and right-sided descending thoracic aorta, those with anomalies of systemic venous drainage masking the origin of great arterial branches, and those with disproportionately small subclavian arteries, constitute the ideal candidates for our suggested modification of the construction of a modified Blalock-Taussig shunt. The palliation provided by these shunts was satisfactory, with predictable growth of pulmonary arteries, insignificant distortion in the great majority, and easy take-down.