Hiroyuki Kubo

Nuclear translocation of ADAM-10 contributes to the pathogenesis and progression of human prostate cancer.

A disintegrin and metalloproteases (ADAM) are cell membrane‐anchored proteins with potential implications for the metastasis of human cancer cells via cell adhesion and protease activities. In prostate cancer (PC), the ADAM‐10 protein showed a nuclear localization whereas in benign prostate hypertrophy (BPH) it was predominantly bound to the cell membrane. We hypothesized that the pathogenesis and progression of PC are attributable to the nuclear translocation of ADAM‐10. Immunoblotting revealed that after 5α‐dihydrotestosterone treatment, a 60‐kDa active form of ADAM‐10 was increased in the nuclear fraction but decreased in the cell membrane and cytoplasmic fractions of human androgen‐dependent PC cells. Immunocytochemistry revealed that after 5α‐dihydrotestosterone treatment, the ADAM‐10 protein was translocated from the cell membrane to the nucleus. Coimmunoprecipitation of androgen receptor and ADAM‐10 was detected in the nuclear fraction but not in the cell membrane and cytoplasmic fractions. Immunohistochemical study of 64 PC and 20 BPH samples showed that the intensity of ADAM‐10 staining was significantly higher in the nuclei of PC cells than in the nuclei of BPH cells (P < 0.0001). It was also significantly lower in the cell membrane of PC cells than in the cell membrane of BPH cells (P = 0.0017). Nuclear staining intensity was significantly correlated with the clinical T‐factor (P = 0.004), the Gleason score (P < 0.0001) and preoperative prostate‐specific antigen levels (P = 0.0061). ADAM‐10 small interfering RNA transfectants showed a significant decrease in cell growth compared to the controls. Our results suggest that in human PC, the nuclear translocation of ADAM‐10 coupled with the androgen receptor is involved in tumor growth and progression. (Cancer Sci 2007; 98: 1720–1726)

Inhibition of ADAM9 expression induces epithelial phenotypic alterations and sensitizes human prostate cancer cells to radiation and chemotherapy.

Recent studies demonstrated the importance of ADAM9 in prostate cancer relapse upon therapy. In this study, we determined the role of ADAM9 in the therapeutic resistance to radiation and chemotherapy.

Reversal of P‐Glycoprotein‐mediated Paclitaxel Resistance by New Synthetic Isoprenoids in Human Bladder Cancer Cell Line

We isolated a paclitaxel‐resistant cell line (KK47/TX30) from a human bladder cancer cell line (KK47/WT) in order to investigate the mechanism of and reversal agents for paclitaxel resistance. KK47/TX30 cells exhibited 700‐fold resistance to paclitaxel and cross‐resistance to vinca alkaloids and topoisomerase II inhibitors. Tubulin polymerization assay showed no significant difference in the ratio of polymerized α‐ and β‐tubulin between KK47/WT and KK47/TX30 cells. Western blot analysis demonstrated overexpression of P‐glycoprotein (P‐gp) and lung resistance‐related protein (LRP) in KK47/TX30 cells. Drug accumulation and efflux studies showed that the decreased paclitaxel accumulation in KK47/TX30 cells was due to enhanced paclitaxel efflux. Cell survival assay revealed that verapamil and cepharanthine, conventional P‐gp modulators, could completely overcome paclitaxel resistance. To investigate whether new synthetic isoprenoids could overcome paclitaxel resistance, we synthesized 31 isoprenoids based on the structure of N‐solanesyl‐N, N′‐bis(3,4‐dimethoxybenzyl)ethylenediamine (SDB), which could reverse multidrug resistance (MDR), as shown previously. Among those examined, trans‐N, N′‐bis(3,4‐dimethoxybenzyl)‐.N‐solanesyl‐l,2‐diaminocyclohexane (N‐5228) could completely reverse paclitaxel resistance in KK47/TX30 cells. N‐5228 inhibited photoaffinity labeling of P‐gp by [3H]azidopine, suggesting that N‐5228 could bind to P‐gp directly and could be a substrate of P‐gp. Next, we investigated structural features of these 31 isoprenoids in order to determine the structural requirements for the reversal of P‐gp‐mediated paclitaxel resistance, suggesting that the following structural features are important for overcoming paclitaxel resistance: (1) a basic structure of 8 to 10 isoprene units, (2) a cyclohexane ring or benzene ring within the framework, (3) two cationic sites in close proximity to each other, and (4) a benzyl group with 3, 4‐dimethoxy functionalities, which have moderate electron‐donating ability. These findings may provide valuable information for the development of P‐gp‐mediated MDR‐reversing agents.

Spatial pattern dynamics over 10 years in a conifer/broadleaved forest, northern Japan

The present study investigated stand dynamics during 10-year period in a conifer/broadleaved mixed forest in Hokkaido, northern Japan, focusing on spatially dependent recruitment, mortality and growth of two growth-form groups, deciduous broadleaved species and the dominant evergreen conifer Abies sachalinensis. The stand-level basal area was maintained over the 10-year period, while a compositional equilibrium at the individual species level was not confirmed. Univariate and bivariate spatial analyses revealed clustering of many of the constituent species. The absence of single-species patches suggested an ambiguous mosaic formed by co-occurrence of Abies and broadleaved trees. The trend towards an aggregated distribution of Abies and broadleaved trees was caused by spatially dependent recruitment rather than mortality. New recruits of broadleaved species were spatially associated with surviving broadleaved trees, while this was not the case for Abies. The degree of competitive effects on growth was not consistent over the 10-year period. Abies showed between-groups competition, but not within-group competition. In contrast, we found asymmetric competitions between the broadleaved trees. Our results suggest that Abies is not sufficiently competitively dominant to exclude broadleaved trees, and that the co-occurrence of the two growth-form groups might be maintained.

Expression of the multidrug resistance-associated protein (MRP) gene in urothelial carcinomas.

The intrinsic or acquired resistance of urothelial cancer to chemotherapy is one major obstacle to successful treatment. Generally, the expression level of P‐glycoprotein in urothelial cancer is low, so we accordingly investigated the expression of multidrug resistance‐associated protein (MRP). We examined the expression of MRP mRNA by means of slot‐blotting samples of 11 renal pelvic and/or ureteral tumors, 33 bladder tumors, one lung metastasis from a ureter tumor, 7 non‐cancerous urothelia from patients with transitional‐cell carcinoma (TCC) and one urothelium from a patient with renal‐cell carcinoma (RCC). We also estimated, by Southern blotting, whether or not the MRP gene was amplified in clinical specimens that overexpressed MRP mRNA. MRP was detected immunohistochemically using a polyclonal antibody against MRP. In all, 5 of 11 renal pelvic and/or ureter tumors (45.5%), 17 of 33 bladder tumors (51.5%) and 4 of 7 non‐cancerous urothelia of TCC patients (57.1%) expressed more than 2‐fold the MRP mRNA levels of drug‐sensitive human KB cells. There was no significant difference in the MRP mRNA level between primary and recurrent tumors. Low‐grade urothelial carcinomas (G1 and G2 TCCs) expressed significantly higher levels of MRP mRNA than the high‐grade G3 TCC. The MRP gene was not amplified in urothelial carcinomas, irrespective of their expression levels of MRP mRNA. Immunohistochemically, MRP was located mainly on the plasma membrane, but also detected on the cytoplasm of cancer cells. MRP may be one mechanism responsible for intrinsic drug resistance in low‐grade urothelial cancer.

Primary malignant melanoma of the male urethra

We report a case of primary malignant melanoma of the male urethra in a patient whose penile shaft was successfully preserved, but who proceeded to acute renal failure (ARF) after interferon (IFN)‐β adjuvant immunotherapy. Primary malignant melanoma of the male urethra is rare and usually shows highly malignant potential. Therefore, urologists must often perform phallectomy, which impacts on the patient both sexually and mentally. A 64‐year‐old man presented at Saiseikai Sendai Hospital with asymptomatic gross hematuria and was diagnosed as distal urethral tumor. We predicted the highly malignant potential of this tumor from the urethroscopic finding and from urinary cytological examination. We did not select trans‐urethral resection (TUR), but selected partial urethrectomy.