Takako Asano

Protein kinase Cδ amplifies ceramide formation via mitochondrial signaling in prostate cancer cells

We studied the role of protein kinase C isoform PKCδ in ceramide (Cer) formation, as well as in the mitochondrial apoptosis pathway induced by anticancer drugs in prostate cancer (PC) cells. Etoposide and paclitaxel induced Cer formation and apoptosis in PKCδ-positive LNCaP and DU145 cells but not in PKCδ-negative LN-TPA or PC-3 cells. In contrast, these drugs induced mitotic cell cycle arrest in all PC cell lines. Treatment with Rottlerin, a specific PKCδ inhibitor, significantly inhibited drug-induced Cer formation and apoptosis in LNCaP cells, as did overexpression of dominant negative–type PKCδ. Overexpression of wild-type PKCδ had an opposite effect in PC-3 cells. Notably, etoposide induced biphasic Cer formation in LNCaP cells. The early and transient Cer increase resulted from de novo Cer synthesis, while the late and sustained Cer accumulation was derived from sphingomyelin hydrolysis by neutral sphingomyelinase (nSMase). Cer, in turn, induced mitochondrial translocation of PKCδ and stimulated the activity of this kinase, promoting cytochrome c release and caspase-9 activation. Furthermore, the specific caspase-9 inhibitor LEHD-fmk significantly inhibited etoposide-induced nSMase activation, Cer accumulation, and PKCδ mitochondrial translocation. These results indicate that PKCδ plays a crucial role in activating anticancer drug–induced apoptosis signaling by amplifying the Cer-mediated mitochondrial amplification loop.

Impaired KLHL3-Mediated Ubiquitination of WNK4 Causes Human Hypertension

Mutations in WNK kinases cause the human hypertensive disease pseudohypoaldosteronism type II (PHAII), but the regulatory mechanisms of the WNK kinases are not well understood. Mutations in kelch-like 3 (KLHL3) and Cullin3 were also recently identified as causing PHAII. Therefore, new insights into the mechanisms of human hypertension can be gained by determining how these components interact and how they are involved in the pathogenesis of PHAII. Here, we found that KLHL3 interacted with Cullin3 and WNK4, induced WNK4 ubiquitination, and reduced the WNK4 protein level. The reduced interaction of KLHL3 and WNK4 by PHAII-causing mutations in either protein reduced the ubiquitination of WNK4, resulting in an increased level of WNK4 protein. Transgenic mice overexpressing WNK4 showed PHAII phenotypes, and WNK4 protein was indeed increased in Wnk4(D561A/+) PHAII model mice. Thus, WNK4 is a target for KLHL3-mediated ubiquitination, and the impaired ubiquitination of WNK4 is a common mechanism of human hereditary hypertension.

Permanent Genetic Tagging of Podocytes: Fate of Injured Podocytes in a Mouse Model of Glomerular Sclerosis

Injured podocytes lose differentiation markers. Therefore, the true identity of severely injured podocytes remains unverified. A transgenic mouse model equipped with a podocyte-selective injury induction system was established. After induction of podocyte injury, mice rapidly developed glomerulosclerosis, with downregulation of podocyte marker proteins. Proliferating epithelial cells accumulated within Bowmans space, as seen in collapsing glomerulosclerosis. In this study, the fate of injured podocytes was pursued. Utilizing Cre-loxP recombination, the podocyte lineage was genetically labeled with lacZ in an irreversible manner. After podocyte injury, the number of lacZ-labeled cells, which were often negative for synaptopodin, progressively declined, correlating with glomerular damage. Parietal epithelial cells, but not lacZ-labeled podocytes, avidly proliferated. The cells proliferating within Bowmans capsule and, occasionally, on the outer surface of the glomerular basement membrane were lacZ-negative. Thus, when podocytes are severely injured, proliferating parietal epithelial cells migrate onto the visceral site, thereby mimicking proliferating podocytes.

3-Hydroxy-3-Methylglutaryl-Coenzyme A Reductase Inhibitor, Fluvastatin, as a Novel Agent for Prophylaxis of Renal Cancer Metastasis

Purpose: Inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, also called statins, are currently used widely as a safe, effective therapeutic in the treatment of hypercholesterolemia. Recently, statins have been recognized for their activity against cancer. In the present study, we examined the effect of a synthetic statin, fluvastatin, on the development of renal cancer. Experimental Design: The effects of fluvastatin on cell viability, cell cycle, in vitro angiogenesis, and invasive properties were examined in murine renal cancer cell Renca. The changes in cell cycle-associated proteins, p21Waf1/Cip1 and p53, and rac1 phosphorylation were analyzed by Western blotting. The prophylactic efficacy of fluvastatin to murine pulmonary metastasis of Renca was examined. Results: Fluvastatin inhibited in vitro growth of Renca cells in a time- and dose-dependent manner, with up to 70% inhibition at a concentration of 10 μmol/L. This inhibitory effect was due to cell cycle arrest at the G1 phase and induction of apoptosis accompanied by up-regulation of p21Waf1/Cip1 and p53. The invasive properties of Renca cells through Matrigel were inhibited by fluvastatin, with decreased phosphorylation of rac1. In vitro angiogenesis was also inhibited by fluvastatin. Furthermore, oral administration at doses of 1 to 10 mg/kg/d, for 12 days after inoculation of Renca cells via the tail vein, significantly decreased the amount of pulmonary metastasis. Conclusions: Because our results suggest that fluvastatin may effectively inhibit in vitro tumor growth, invasion, angiogenesis, and metastasis of Renca cells, oral administration of fluvastatin could be a novel, safe, and effective agent for preventing metastasis of renal cancer.

Novel SN-38–Incorporated Polymeric Micelle, NK012, Strongly Suppresses Renal Cancer Progression

It has been recently reported that NK012, a 7-ethyl-10-hydroxy-camptothecin (SN-38)-releasing nanodevice, markedly enhances the antitumor activity of SN-38, especially in hypervascular tumors through the enhanced permeability and retention effect. Renal cell carcinoma (RCC) is a typical hypervascular tumor with an irregular vascular architecture. We therefore investigated the antitumor activity of NK012 in a hypervascular tumor model from RCC. Immunohistochemical examination revealed that Renca tumors contained much more CD34-positive neovessels than SKRC-49 tumors. Compared with CPT-11, NK012 had significant antitumor activity against both bulky Renca and SKRC-49 tumors. Notably, NK012 eradicated rapid-growing Renca tumors in 6 of 10 mice, whereas it failed to eradicate SKRC-49 tumors. In the pulmonary metastasis treatment model, an enhanced and prolonged distribution of free SN-38 was observed in metastatic lung tissues but not in nonmetastatic lung tissues after NK012 administration. NK012 treatment resulted in a significant decrease in metastatic nodule number and was of benefit to survival. Our study shows the outstanding advantage of polymeric micelle-based drug carriers and suggests that NK012 would be effective in treating disseminated RCCs with irregular vascular architectures.

ZD1839 Modulates Paclitaxel Response in Renal Cancer by Blocking Paclitaxel-Induced Activation of the Epidermal Growth Factor Receptor–Extracellular Signal-Regulated Kinase Pathway

Purpose: We evaluated the antitumor activity of ZD1839, a selective epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitor, in combination with paclitaxel in human renal cell carcinomas (RCCs). Experimental Design: Eight human RCC lines and the surgical specimens obtained from 10 RCC patients were used. The protein expression was detected by Western blotting, immunohistochemistry and/or flow cytometry. Apoptosis was evaluated by flow cytometry and fragmented DNA ELISA. SKRC-49 tumor xenografts in athymic nude mice were treated with ZD1839 and/or paclitaxel, and tumor volume was determined Results: EGFR protein was expressed and phosphorylated in eight RCC lines and EGFR expression was markedly increased in RCC specimens compared with adjacent normal renal tissues. Treatment of SKRC-49 with 1 μm ZD1839 resulted in a marked decrease in the phosphorylation of EGFR but not of HER-2. Treatment of SKRC-49 with ZD1839 in combination with 5 nm paclitaxel resulted in a significant increase in apoptotic cell number compared with paclitaxel alone, whereas ZD1839 alone failed to induce apoptosis. Although administration of ZD1839 or paclitaxel resulted in a transient growth inhibition in SKRC-49 xenografts, significant tumor regrowth delay was observed when paclitaxel was combined with ZD1839. Paclitaxel phosphorylated extracellular signal-regulated kinase through EGFR activation predominantly in cancer cells. ZD1839 promoted paclitaxel-induced Bcl-2 down-regulation resulting in promoting apoptosis by blocking paclitaxel-induced activation of the EGFR—extracellular signal-regulated kinase antiapoptotic pathway independent of Akt activity in SKRC-49. Conclusions: Our findings support the idea that the significant clinical benefit is obtained from ZD1839 in combination with paclitaxel for the treatment of RCC.

Fatty Acid Synthase Over Expression is an Indicator of Tumor Aggressiveness and Poor Prognosis in Renal Cell Carcinoma

PURPOSE Fatty acid synthase is a key enzyme in the de novo biosynthesis of fatty acids. Increased fatty acid synthase expression and its association with tumor aggressiveness and poor prognosis have been demonstrated in various human malignant tumors. We investigated fatty acid synthase expression in patients with renal cell carcinoma and its impact on clinicopathological parameters. MATERIALS AND METHODS Fatty acid synthase expression in 120 patients with renal cancer was examined by immunohistochemistry. The relationship between fatty acid synthase expression status and various clinicopathological parameters was analyzed. Survival analysis was performed using the log rank test and a Cox multivariate hazard model. RESULTS Of 120 tumors 18 (15%) showed positive fatty acid synthase expression, which was significantly associated with advanced pathological T stage (pT3-4, p = 0.0009), regional lymph node metastasis (p = 0.0429), distant metastasis (p = 0.0042), higher histological grade (G3, p = 0.0017) and microvascular invasion (p = 0.0357). Patients with positive fatty acid synthase expression had significantly shorter cancer specific survival than those with negative FAS expression (p <0.0001). Multivariate Cox proportional hazards model analysis demonstrated that positive fatty acid synthase expression was an independent predictor of shortened cancer specific survival (p = 0.0363, HR 3.736). CONCLUSIONS Increased FAS expression could be an indicator of tumor aggressiveness and poor prognosis of renal cell carcinoma. Patients with fatty acid synthase positive tumors should be followed closely and carefully, and adjuvant therapy should be considered.

Genetic Podocyte Lineage Reveals Progressive Podocytopenia with Parietal Cell Hyperplasia in a Murine Model of Cellular/Collapsing Focal Segmental Glomerulosclerosis

Focal segmental glomerulosclerosis (FSGS) is a progressive renal disease, and the glomerular visceral cell hyperplasia typically observed in cellular/collapsing FSGS is an important pathological factor in disease progression. However, the cellular features that promote FSGS currently remain obscure. To determine both the origin and phenotypic alterations in hyperplastic cells in cellular/collapsing FSGS, the present study used a previously described FSGS model in p21-deficient mice with visceral cell hyperplasia and identified the podocyte lineage by genetic tagging. The p21-deficient mice with nephropathy showed significantly higher urinary protein levels, extracapillary hyperplastic indices on day 5, and glomerular sclerosis indices on day 14 than wild-type controls. X-gal staining and immunohistochemistry for podocyte and parietal epithelial cell (PEC) markers revealed progressive podocytopenia with capillary collapse accompanied by PEC hyperplasia leading to FSGS. In our investigation, non-tagged cells expressed neither WT1 nor nestin. Ki-67, a proliferation marker, was rarely associated with podocytes but was expressed at high levels in PECs. Both terminal deoxynucleotidyl transferase dUTP nick-end labeling staining and electron microscopy failed to show evidence of significant podocyte apoptosis on days 5 and 14. These findings suggest that extensive podocyte loss and simultaneous PEC hyperplasia is an actual pathology that may contribute to the progression of cellular/collapsing FSGS in this mouse model. Additionally, this is the first study to demonstrate the regulatory role of p21 in the PEC cell cycle.

Does cyclooxygenase-2 inhibitor prevent renal tissue damage in unilateral ureteral obstruction?

PURPOSE We determined whether the cyclooxygenase-2 inhibitor etodolac affects renal tubular damage and interstitial fibrosis in unilateral ureteral obstruction. MATERIALS AND METHODS Etodolac (10 mg./kg.) was administered to rats 1 day before unilateral ureteral obstruction and every day thereafter. Kidneys were harvested at day 14 after unilateral ureteral obstruction. Tissue transforming growth factor-beta and prostaglandin E2 were measured by bioassay using mink lung epithelial cells and enzyme linked immunosorbent-sandwich assay. Renal tubular proliferation and apoptosis were detected by immunostaining with proliferating cellular nuclear antigen and by terminal deoxynucleotidyl transferase mediated deoxyuridine triphosphate nick end labeling, respectively. Cyclooxygenase-2 expression was detected by immunohistochemistry. Fibrosis was assessed by measuring collagen deposition in trichrome stained slides. RESULTS Bioassay showed that in the control group obstructed kidneys contained significantly higher mean transforming growth factor-beta1 than unobstructed kidneys (79.1 +/- 8.3 versus 33.6 +/- 4.2 ng./gm. tissue) and etodolac significantly decrease the mean value in obstructed kidneys (46.2 +/- 10.0 ng./gm. tissue). Assay demonstrated that obstructed control kidneys had significantly more mean tubular apoptosis than their unobstructed counterparts (26.6 +/- 5.4 versus 2.2 +/- 1.4 nuclei per high power field) and etodolac significantly decreased mean renal tubular apoptosis in the obstructed kidneys (16.2 +/- 1.9 nuclei per high power field). In addition, immunostaining with proliferating cellular nuclear antigen showed that obstructed kidneys in the control group had significantly more mean renal tubular proliferation than unobstructed kidneys (9.8 +/- 3.4 versus 3.9 +/- 0.1 per high power field) and etodolac significantly increased mean proliferating renal tubule in the obstructed kidneys (24.9 +/- 4.3 per high power field). Control obstructed kidneys had significantly more fibrosis and prostaglandin E2 production, which were also significantly blunted by etodolac. CONCLUSIONS The cyclooxygenase-2 inhibitor etodolac significantly reduces tissue transforming growth factor-beta, resulting in decreased tubular damage and interstitial fibrosis. This finding suggests that etodolac is a promising agent for preventing renal tissue damage in unilateral ureteral obstruction.

Pharmacological Inhibitor of Fatty Acid Synthase Suppresses Growth and Invasiveness of Renal Cancer Cells

PURPOSE Fatty acid synthase has been shown to be over expressed in a wide range of cancers and it has emerged as a therapeutic target. We examined whether fatty acid synthase could be a novel therapeutic target for renal cell carcinoma using the pharmacological fatty acid synthase inhibitor C75 (Cayman Chemical, Ann Arbor, Michigan). MATERIALS AND METHODS The effects of C75 on cell viability and proliferation in human renal cancer 769P (ATCC(R)), Caki-1 and KU20-01 cells were examined by MTS assay and cell counts. Cell cycle distribution was analyzed by flow cytometry and cell invasiveness was assessed by wound healing and Matrigel(trade mark) invasion assays. Fatty acid synthase expression and the effects of C75 on intracellular signaling pathways were analyzed by Western blotting. The antitumor efficacy of C75 was examined using Caki-1 cell xenografts. RESULTS All renal cancer cell lines expressed detectable fatty acid synthase. C75 (10 mug/ml) significantly inhibited cell viability and growth by arresting the cell cycle at the G2/M phase and inducing apoptosis (p <0.01). The covered area in the wound and the number of cells invading through a Matrigel chamber were significantly smaller for cells treated with C75 than they were for control cells treated with vehicle (p <0.001). C75 suppressed Her2 and epidermal growth factor receptor expression as well as STAT3 phosphorylation, while increasing p53 and p21(Waf1/Cip1) expression. Intraperitoneal administration of C75 at doses of 20 mg/kg per week for 28 days significantly reduced the tumor volume of Caki-1 xenografts (p <0.05). CONCLUSIONS Pharmacological inhibition of fatty acid synthase could be an effective strategy for treating renal cell carcinoma.