Makoto Mitsuhashi

Expression of peroxisome proliferator-activated receptors (PPARs) in human urinary bladder carcinoma and growth inhibition by its agonists.

Recent studies have demonstrated that peroxisome proliferator activator‐receptors(PPAR)‐γ is expressed in various cancer tissues and its ligand induces growth arrest of these cancer cells through apoptosis. In our study, we investigated the expression of PPAR‐α, β and γ in human bladder tumor (BT) and normal bladder (NB) tissues as well as the effects of PPAR‐γ ligands. Specimens were obtained from 170 patients with BT and 20 with NB. The expressions were investigated using RT‐PCR and immunohistochemical methods. We also investigated the inhibitory effect of PPAR‐γ ligands on BT‐derived cell line. Immunoreactive PPAR‐α and ‐β were significantly apparent in both BT and NB tissues. Although no marked expression of PPAR‐γ was observed in NB tissue, significant expression was found in BT tissue. The extent and intensity of immunoreactive PPAR‐γ polypeptides in BT cells were statistically much greater than those of NB cells. Correlation between PPAR‐γ expression and tissue type or progression of bladder cancer was observed; PPAR‐γ expression was higher in G3 of bladder cancer than in G1 and was higher in advanced than in early cancer. PPAR‐γ agonists, troglitazone and 15‐deoxy‐Δ12, 14‐prostaglandin J2 inhibited the growth of the BT cells. PPAR‐γ is expressed in bladder tumor, and results suggest that PPAR‐γ ligands may mediate potent antiproliferative effects against BT cells. Thus, PPAR‐γ has the ability to become a new target in treatment of bladder tumor.

Expression of peroxisome proliferator-activated receptors in human testicular cancer and growth inhibition by its agonists

OBJECTIVES To investigate the expression of peroxisome proliferator activator-receptor (PPAR)-alpha, beta, and gamma in human testicular cancer (TC) and normal testicular (NT) tissues, as well as the effects of the PPAR-gamma ligand. Recent studies have demonstrated that PPAR-gamma is expressed in various cancer tissues and its ligand induces growth arrest of these cancer cells through apoptosis. However, the expression of PPARs and the effects of PPAR-gamma ligand in testis have not been examined. METHODS Tumor specimens were obtained from 72 patients with TC. Specimens were obtained from 20 patients with NT tissue. The expressions were investigated using reverse transcriptase-polymerase chain reaction and immunohistochemical methods. We also investigated the inhibitory effect of the PPAR-gamma ligand on the TC-derived cell line. RESULTS Immunoreactive PPAR-alpha and beta were significantly apparent in TC tissues. Marked expression of PPAR-alpha and beta was also detected in the NT group. However, very weak or no expression of immunoreactive PPAR-gamma was found in the NT cases. In contrast, we found significant expression of immunoreactive PPAR-gamma in the cancer cells in the TC group. The synthetic PPAR-gamma agonists thiazolidinedione compounds and the endogenous PPAR-gamma ligand, 15-deoxy-Delta-prostaglandin J(2), inhibited the growth of the TC cells. CONCLUSIONS PPAR-gamma is induced in TC, and the results suggest that PPAR-gamma ligands may mediate potent antiproliferative effects against TC cells through differentiation. Thus, PPAR-gamma may become a new target in the treatment of TC.

Chemopreventive effect of JTE-522, a selective cyclooxygenase-2 inhibitor, on 1, 2-dimethylhydrazine-induced rat colon carcinogenesis

Selective COX-2 inhibitors have been suggested to be an effective strategy in the prevention of colon cancer without the adverse side effects of non-selective, nonsteroid anti-inflammatory drugs. The present experiment was designed to assess the potential chemopreventive properties of JTE-522, a new selective cyclooxygenase-2 inhibitor, on the induction of 1,2-dimethylhydrazine (DMH)-induced colonic aberrant crypt foci (ACF), a marker of rat colon carcinogenesis. A total of 80 male F344 rats were treated with 3 or 10 mg/kg of body weight JTE-522 or vehicle by oral gavage five times weekly from the start of the experiment. One week later, rats received s.c. injections of saline or 20 mg/kg of body weight DMH once weekly for four successive weeks. At the end of 12 weeks after the start of experiment, all rats were sacrificed and colons were evaluated for ACF. 10 mg/kg JTE522 significantly suppressed the total ACF/colon. No inhibitory effect was observed in the 3 mg/kg JTE-522 treatment group. This result suggests that JTE-522 possesses chemopreventive activity against colon carcinogenesis.

p53 and H-ras mutations and microsatellite instability in renal pelvic carcinomas of NON/Shi mice treated with N-butyl-N-(4-hydroxybutyl)-nitrosamine: Different genetic alteration from urinary bladder carcinoma

We previously reported p53 mutations to be frequent (greater than 70%), whereas both H‐ras mutations and microsatellite instability (MSI) were infrequent (about 10%), in urinary bladder carcinomas (UBCs) and their metastatic foci in the N‐butyl‐N‐(4‐hydroxybutyl)nitrosamine (BBN)‐induced mouse urothelial carcinogenesis model. In the present study, an analysis of p53 and H‐ras mutations as well as MSI was performed on 12 renal pelvic carcinomas (RPCs) and 8 metastatic or invading foci produced by the same experimental procedure. Histologically, 10 of the RPCs were transitional cell carcinomas and the remaining 2 were squamous cell carcinomas. p53 mutations were infrequent and only found in one primary RFC (8%), its metastatic foci and an invading lesion in another animal (in a total 2 of 12; 17%). H‐ras mutations were slightly more frequent (found in 3 of 12 animals; 25%), 4 of 5 involving codon 44, GTG to GCG, not a hot‐spot reported for human cancers. In two cases, H‐ras mutations were confined to lung metastasis and not detectable in their primary RPCs. MSI analysis was available for 6 pairs of primary RPCs and their metastatic foci, and 4 animals (67%) had MSI at one or more microsatellite loci. Overall, the distribution of genetic alterations differed from that in UBCs produced by the same experimental protocol. The results thus suggest that different genetic pathways may participate in carcinogenesis of the upper and lower urinary tract due to BBN.

Significance of overexpression of metallothionein in mouse urinary bladder focal lesions induced by treatment with N‐butyl‐N‐(4‐hydroxybutyl)‐nitrosamine

Metallothionein (MT) is expressed in various types of human tumors, including transitional cell carcinomas of the urinary bladder, but its biological significance remains unclear. In the present study, the role of MT in urinary bladder carcinogenesis induced by N‐butyl‐N‐(4‐hydroxybutyl)nitrosamine (BBN) treatment was investigated using C57BL/6 mice. One hundred 5‐week‐old male C57BL/6 mice were divided into two groups, which were given drinking water with or without 0.05% BBN throughout the experimental period. Subgroups of ten animals from each group were sacrificed at weeks 5, 10, 15, 20 and 25, and urinary bladder samples were examined immunohistochemically for MT, proliferating cell nuclear antigen (PCNA) and apoptosis. MT was found to be abundant in normal‐looking mucosa, but decreased with progression from precancerous lesions to invasive carcinoma in the urinary bladder obtained from BBN‐treated mice. Lesions could be divided into MT‐positive and negative. There was a tendency for greater MT expression in PCNA‐positive lesions, while apoptosis was rather associated with MT‐negativity. These data suggest that the overexpression of MT may play a role in mouse urinary bladder carcinogenesis.