Gender Disparity in Bladder Cancer and Chemopreventive Intervention

描述（由申请人提供）：膀胱癌（BC）是男性第四大常见癌症，但在不同种族中，男性的发病率几乎是女性的4倍；根本原因尚不清楚。缺乏这方面的知识阻碍了BC预防的进展。根据我们已发表和未发表的数据，我们假设肝脏udp -葡萄糖醛酸糖基转移酶1A3 （UGT1A3）是人类BC发展中性别差异的关键决定因素，通过将雄激素信号转化为增加尿中芳胺致癌物向膀胱组织的传递。芳胺类，尤其是4-氨基联苯（ABP），是导致人类BC的主要原因。我们还假设萝卜硫素（SF），一种常见的膳食植物化学物质，可以通过增强膀胱的细胞保护防御来阻止UGT1A3促进芳胺诱导的膀胱癌。这些假设将在使用培养细胞和转基因小鼠模型的互补方法的四个特定目标中进行检查。目的1是验证我们的假设，即肝脏UGT1A3是决定BC发展中性别差异的关键分子。比较野生型小鼠和UGT1A3转基因小鼠（肝脏特异性和雄激素非依赖性表达）abp诱导膀胱癌的发生。还将对阉割和未阉割的小鼠进行比较。另一种致癌物2-乙酰氨基芴（2- aaf）将用于排除abp特异性效应。目的2评估UGT1A3多态性对其对ABP和2- aaf的催化活性的影响，以及对膀胱细胞和肝细胞对ABP和2- aaf诱导的DNA损伤易感性的影响。UGT1A3基因存在6个单核苷酸多态性。所有多态性变异连同野生型基因将被评估。目的3是验证我们的假设，SF可以通过刺激膀胱中针对芳胺致癌物（ABP和2-AAF）的细胞保护性防御来阻断UGT1A3促进膀胱癌的发生，而不调节肝脏中的UGT1A3。不干扰肝脏UGT1A3可能是可取的，因为这种酶可能在生理上很重要，如代谢雌酮。SF是一种很有前途的癌症预防药物，可选择性地通过尿液排泄到膀胱组织中。我们将使用两种动物模型来验证这一假设，包括上述UGT1A3小鼠模型和Tg-UGT1小鼠模型（小鼠同时携带人类UGT1A3基因的编码和调控序列）。目的4：在体内证实雄激素对UGT1A3的转录刺激，并阐明雄激素刺激UGT1A3的分子机制。这将通过使用细胞模型和Tg-UGT1小鼠模型来完成。影响：建议的研究有望导致BC性别差异的分子基础的阐明和有效预防这种疾病的新策略的发展。

DESCRIPTION (provided by applicant): Bladder cancer (BC) is the 4th most common cancer in men, but BC incidence is nearly 4 fold higher in men than in women across race; the underlying cause is not understood. Lack of such knowledge impedes progress in BC prevention. On the basis of our published and unpublished data, we hypothesize that hepatic UDP-glucuronosyltransferase 1A3 (UGT1A3) is a key determinant of the gender disparity in human BC development through converting androgen signal to increased urinary delivery of arylamine carcinogens to bladder tissue. Arylamines, 4-aminobiphenyl (ABP) in particular, are the main cause of human BC. We also hypothesize that sulforaphane (SF), a common dietary phytochemical, can block UGT1A3 from promoting arylamine-induced bladder carcinogenesis by boosting cytoprotective defense in the bladder. These hypotheses will be examined in four specific aims using complementary approaches of cultured cells and transgenic mouse models. Aim 1 is to test our hypothesis that liver UGT1A3 is a key molecule that determines the gender disparity in BC development. Wild-type mice and UGT1A3 transgenic mice (liver- specific and androgen-independent expression) will be compared for ABP-induced bladder carcinogenesis. Comparison will also be made between mice with and without castration. Another carcinogen 2- acetylaminofluorene (2-AAF) will be used to rule out ABP-specific effects. Aim 2 is to assess the impact of UGT1A3 polymorphism on its catalytic activity toward ABP and 2-AAF and on the susceptibility of bladder cells and liver cells to DNA damage induced by ABP and 2-AAF. Six single nucleotide polymorphisms occur in UGT1A3 gene. All the polymorphic variants together with the wild-type gene will be evaluated. Aim 3 is to test our hypothesis that SF can block UGT1A3 from promoting bladder carcinogenesis by stimulating cytoprotective defense against arylamine carcinogens (ABP and 2-AAF) in the bladder, without modulating UGT1A3 in the liver. Non-interference of liver UGT1A3 may be desirable, since this enzyme may be physiologically important, such as metabolizing estrone. SF is a promising cancer-preventive agent and is selectively delivered to bladder tissue through urinary excretion. Two animal models will be used to test the hypothesis, including the UGT1A3 mouse model described above and the Tg-UGT1 mouse model (mice carry both the coding and the regulatory sequences of the human UGT1A3 gene). Aim 4 is to confirm that UGT1A3 is transcriptionally stimulated by androgen in vivo and to elucidate the molecular mechanism by which androgen stimulates UGT1A3. This will be accomplished by using both cell models and the Tg-UGT1 mouse model. Impact: The proposed studies are expected to lead to the elucidation of the molecular basis of the gender disparity in BC and the development of new strategy for effective prevention of this disease.