Mingxi Tang

Protective effects of citrus nobiletin and auraptene in transgenic rats developing adenocarcinoma of the prostate (TRAP) and human prostate carcinoma cells

Dietary phytochemicals, including nobiletin and auraptene, have been shown to exert inhibiting effects in several chemically induced carcinogenesis models. We here investigated the influence of nobiletin and auraptene on prostate carcinogenesis using transgenic rats developing adenocarcinoma of the prostate (TRAP) bearing the SV40 T antigen transgene under control of the probasin promoter and human prostate cancer cells. Starting at 5 weeks of age, male TRAP rats received powder diet containing 500 p.p.m. nobiletin or auraptene, or the basal diet for 15 weeks and then were sacrificed for analysis of serum testosterone levels and histological changes. The body and relative prostate weights and serum testosterone levels did not differ among the groups. Since all animals developed prostate carcinomas, these were semiquantitatively measured and expressed as relative areas of prostate epithelial cells. Nobiletin caused significant reduction in the ventral (P < 0.01), lateral (P < 0.001) and dorsal (P < 0.05) prostate lobes, while decreasing high grade lesions (P < 0.05) in the ventral and lateral lobes. Feeding of auraptene also effectively reduced the epithelial component (P < 0.05) and high grade lesions (P < 0.05), in the lateral prostate. A further experiment demonstrated that growth of androgen sensitive LNCaP and androgen insensitive DU145 and PC3 human prostate cancer cells, was suppressed by both nobiletin and to a lesser extent auraptene in a dose‐dependent manner, with significant increase in apoptosis. In conclusion, these compounds, particularly nobiletin, may be valuable for prostate cancer prevention. (Cancer Sci 2007; 98: 471–477)

Suppression of prostate cancer in a transgenic rat model via γ-tocopherol activation of caspase signaling

Epidemiological data indicate that intake of one form of vitamin E, γ‐tocopherol, may reduce prostate cancer risk, and several in vitro studies have demonstrated that γ‐tocopherol can inhibit prostate cancer cell growth. The purpose of the present study was to confirm effects of γ‐tocopherol on prostate cancer in the transgenic rat for adenocarcinoma of prostate (TRAP) model established in our laboratory.

Silencing of connexin 43 suppresses invasion, migration and lung metastasis of rat hepatocellular carcinoma cells

To reduce cancer mortality, understanding of mechanisms of cancer metastasis is crucial. We have established six rat hepatocellular carcinoma (HCC) cell lines, which exhibit differing metastatic potential to the lung after inoculation into the tail veins of nude mice. In the present experiment, we investigated the process of cell attachment to metastatic sites and possible regulating factors. One hour after inoculation, two of two HCC cell lines with high metastatic potential and one of two HCC cell lines with low metastatic potential exhibited many attached cells in the lung. One day after inoculation, lung metastatic foci were observed only with highly‐metastatic cells with elevated connexin 43 (Cx43) expression as assessed by cDNA array analysis. Furthermore, 24 or 48 h after transfection of an siRNA targeting Cx43, in vitro invasion and migration were suppressed by 68% (P < 0.001) and 36% (P < 0.05) compared with control‐siRNA transfected cells, despite no differences in cellular morphology, cell proliferation or apoptotic activity. Moreover, the number of metastatic nodules per lung area in nude mice was significantly (P < 0.01) reduced. In conclusion, suppression of Cx43 expression in tumor cells reduced in vitro migration and invasion capacity and in vivo metastatic ability so that Cx43 has potential as a molecular target for prevention of cancer metastasis with Cx43 overexpressing tumors. (Cancer Sci 2012; 103: 860–867)

Ellagic acid, a component of pomegranate fruit juice, suppresses androgen-dependent prostate carcinogenesis via induction of apoptosis

Ellagic acid (EA), a component of pomegranate fruit juice (PFJ), is a plant‐derived polyphenol and has antioxidant properties. PFJ and EA have been reported to suppress various cancers, including prostate cancer. However, their chemopreventive effects on development and progression of prostate cancer using in vivo models have not been established yet.

Therapeutic targeting of angiotensin II receptor type 1 to regulate androgen receptor in prostate cancer.

With the limited strategies for curative treatment of castration‐resistant prostate cancer (CRPC), public interest has focused on the potential prevention of prostate cancer. Recent studies have demonstrated that an angiotensin II receptor blocker (ARB) has the potential to decrease serum prostate‐specific antigen (PSA) level and improve performance status in CRPC patients. These facts prompted us to investigate the direct effects of ARBs on prostate cancer growth and progression.

Induction of apoptosis in the LNCaP human prostate carcinoma cell line and prostate adenocarcinomas of SV40T antigen transgenic rats by the Bowman-Birk inhibitor.

The soybean‐derived serine protease inhibitor, Bowman–Birk inhibitor (BBI), has been reported as a potent chemoprevention agent against several types of tumors. The present study was undertaken to evaluate the effects of BBI on androgen‐sensitive/dependent prostate cancers using a human prostate cancer cell (LNCaP) and the transgenic rats developing adenocarcinoma of the prostate (TRAP) model. Treatment of LNCaP prostate cancer cells with 500 µg/mL BBI resulted in inhibition of viability measured on WST‐1 assays, with induction of connexin 43 (C×43) and cleaved caspase‐3 protein expression. Feeding of 3% roughly prepared BBI (BBIC) to TRAP from the age 3 weeks to 13 weeks resulted in significant reduction of the relative epithelial areas within the acinus and multiplicity of the adenocarcinomas in the lateral prostate lobes. C×43‐ and terminal deoxynucleotidyl transferase mediated dUTP‐biotin end labeling of fragmented DNA (TUNEL)‐positive apoptotic cancer cells were more frequently observed in the lateral prostates treated with BBIC than in the controls. These in vivo and in vitro results suggest that BBI possesses chemopreventive activity associated with induction of C×43 expression and apoptosis.

Inhibition of prostate carcinogenesis in probasin/SV40 T antigen transgenic rats by leuprorelin, a luteinizing hormone–releasing hormone agonist

The effects of leuprorelin acetate, a luteinizing hormone‐releasing hormone agonist (LHRH‐A), on prostate carcinogenesis in probasin/SV40 Tag transgenic rat was investigated. Fifteen weeks after administration of 0.28 and 2.8 mg/kg leuprorelin, prostate weights and serum testosterone levels were significantly decreased compared to values for transgenic controls. Histopathological findings revealed that the incidence of prostatic adenocarcinomas was significantly reduced in ventral, dorsal and lateral lobes of the prostate, correlating with decreased expression of SV40 Tag oncoprotein as well as inhibition of DNA synthesis and proliferation of epithelial cells in neoplastic lesions of the ventral prostate. Microarray analysis further showed leuprorelin acetate to significantly inhibit testicular steroidogenesis, suppressing the expression of SV40 Tag oncoprotein and altering the expression of a large number of genes which might be involved in the inhibition of prostate cancer progression in this rat model. (Cancer Sci 2006; 97: 459–467)

FTY720, an immunosuppressant, attenuates chronic pancreatitis in rats by suppressing T-cell infiltration.

Objectives: FTY720, a novel synthetic immunosuppressant, decreases peripheral blood lymphocytes by accelerating their homing to the peripheral and mesenteric lymph nodes and Peyers patches. We previously reported that tacrolimus, another immunosuppressant, attenuates chronic pancreatitis by suppressing T-cell infiltration in male Wistar Bonn/Kobori rats but also may cause toxicity. To assess the effects of FTY720 on the development of pancreatic inflammation and fibrosis in the same model, the agent dissolved in physiologic saline was subcutaneously injected to 10-week-old male WBN/Kob rats for 10 weeks. Methods: Parameters for inflammation and fibrosis were assessed and interferon-γ and transforming growth factor-β1 mRNA in the pancreas were determined by RT-PCR. Results: Treatment with FTY720 attenuated gross alterations in the pancreas, including pigmentation and atrophy. This protective effect was quantitatively confirmed by significant increase in pancreatic weights and decreases in pancreatic myeloperoxidase activity (an index of granulocyte infiltration), pancreatic hydroxyproline content (an index of collagen deposition), ratio of fibrous tissue, and histologic scores. The obvious infiltration of CD4- and CD8-positive T cells into the pancreas in the saline group was almost completely prevented by administration of FTY720, which also suppressed overexpression of interferon and transforming growth factor-β1 mRNA in the pancreas. Conclusion: We conclude that FTY720 prevents pancreatic inflammation and fibrosis by suppressing infiltration of CD4- and CD8-positive T cells and by downregulating induction of interferon and transforming growth factor-β1 mRNA in the pancreas.

Suppressive effects of antiandrogens, finasteride and flutamide on development of prostatic lesions in a transgenic rat model

Transgenic (TG) rats bearing a probasin promoter/simian virus 40 T antigen (SV40 Tag) construct were treated with antiandrogens to examine their ability to suppress prostate carcinogenesis. Finasteride and flutamide were administered to 10-week-old TG rats five times a week for 2, 5 and 7 weeks. Antiandrogen-treated prostates exhibited atrophic glandular structures with almost no expression of SV40 Tag and only weak signals for androgen receptors. Furthermore, quantitative data for ventral prostate adenocarcinomas showed significant decrease with antiandrogen treatment. Both finasteride and flutamide had the ability to suppress SV40 Tag-driven carcinogenesis through their different antiandrogenic mechanisms, suggesting that this TG model is suitable for exploring the potential of agents to inhibit prostate cancer development.

Hypertension is positively associated with prostate cancer development in the TRAP transgenic rat model

Epidemiological data on the relationship between hypertension and prostate cancer development are conflicting. To cast light on this question, we performed animal experiments using hybrid rats generated by crossing the spontaneously hypertensive rat (SHR) or its normotensive control Wistar Kyoto (WKY) rat with a transgenic rat for adenocarcinoma of prostate (TRAP) that features development of adenocarcinoma at high incidence by 15 weeks of age. The number of adenocarcinomatous foci in the lateral prostate of hypertensive (TRAP × SHR)F1 rats was demonstrated to be significantly increased compared with those of normotensive (TRAP × WKY)F1 rats. In the ventral prostate, increase of carcinoma foci was also observed but did not reach significance. The number of cancer foci showing microinvasion in (TRAP × SHR)F1 rats was higher than that of (TRAP × WKY)F1 rats, but again without significance, while treatment with prazosin, an anti‐hypertensive agent, tended to decrease microinvasive carcinoma foci in both the ventral and lateral prostate. In conclusion, the present study provided additional evidence that high blood pressure is associated with prostate cancer risk.