Chemoprevention of upper aerodigestive tract cancer by dietary zinc

描述（由申请人提供）：上气消化道癌症（UADT），包括食道癌和口腔癌，是全球癌症死亡的主要原因。在人类中，膳食锌缺乏与食道癌和口腔癌的风险增加有关。在啮齿类动物中，锌缺乏通过引起细胞增殖增加和广泛的基因表达改变，包括环氧化酶-2 （COX-2）的上调，从而在UADT中产生癌前状态，COX-2是一种在多种人类癌前和恶性病变中过度表达的酶。因此，锌缺乏促进了4-硝基喹啉1-氧化物（NQO）在啮齿动物中的UADT致癌作用和n -亚硝基甲基苄胺（NMBA）在啮齿动物中的食管癌作用。补充锌可以逆转细胞增殖，刺激细胞凋亡，纠正食管上皮中COX-2的过度表达，并抑制癌变。我们获得的新数据显示(i)转录因子NF-kappaB和COX-2在锌缺乏（ZD）大鼠食管中共同过表达；（ii）缺乏锌的COX-2小鼠没有表现出预期的nmba诱导的肿瘤产量降低；（iii）塞来昔布，一种COX-2选择性抑制剂，单独给予以前用NQO治疗的ZD大鼠，在预防肿瘤方面不如含锌治疗有效。我们提出，膳食锌在UADT癌症启动和化学预防中起关键作用，并将通过以下相关目的研究锌在体内影响这些过程的机制：1)通过确定靶向kappaB激酶(IKK)/NF-kappaB激活途径的抑制剂，包括硼替佐米、PS-1145和NF-kappaB p65小干扰RNA (si)RNA是否能有效抑制COX-2的表达，来确定体内锌缺乏情况下NF-kappaB与COX-2诱导在大鼠食管中的联系。比较补锌对COX-2表达、增殖和凋亡的影响；2)通过研究独立于COX-2的花生四烯酸代谢信号，确定锌缺乏增加COX-2缺失小鼠NMBA诱导的前胃癌发生的机制；3)通过评价锌补充剂的疗效和生物标志物调节作用，探讨ZD大鼠UADT癌症模型的防癌作用；锌与低剂量姜黄素（NF-kappaB抑制剂）、zileuton （5-LOX抑制剂）联合使用，以及低剂量抑制剂的双重治疗。锌和低剂量抑制剂的组合可能有效预防，而没有与高剂量这些药物相关的副作用的风险。我们将通过免疫组织化学评估病变中特异性增殖、凋亡和其他相关标志物的定位。然后，我们将使用这些标记物的适当子集作为替代终点来评估每种化疗方案的疗效。我们还将比较锌或锌加抑制剂治疗引起的基因表达变化。这些研究结果将为膳食锌在UADT致癌中的作用提供新的认识，并为化学预防这些致命癌症的新饮食方法提供基础。

DESCRIPTION (provided by applicant): Cancer of the upper aerodigestive tract (UADT), including esophageal and oral cancer, is a major cause of cancer deaths worldwide. In humans, dietary zinc deficiency is associated with an increased risk of esophageal and oral cancer. In rodents, zinc deprivation creates a precancerous condition in the UADT by causing increased cell proliferation and extensive gene expression changes, including upregulation of cyclooxygenase-2 (COX-2), an enzyme overexpressed in a variety of human premalignant and malignant lesions. Thus, zinc deficiency promotes UADT carcinogenesis by 4-nitroquinoline 1-oxide (NQO) and esophageal carcinogenesis by N-nitrosomethylbenzylamine (NMBA) in rodents. Zinc replenishment reverses cell proliferation, stimulates apoptosis, corrects COX-2 overexpression in esophageal epithelium, and inhibits carcinogenesis. We have obtained new data showing that (i) transcription factor NF-kappaB and COX-2 are co-overexpressed in zinc deficient (ZD) rat esophagi; (ii) zinc-deficient COX-2 null mice do not show the expected reduction in NMBA-induced tumor yield; and (iii) celecoxib, a COX-2 selective inhibitor, given singly to ZD rats formerly treated with NQO, is not as effective in tumor prevention as treatments that includes zinc. We propose that dietary zinc plays critical roles in UADT cancer initiation and chemoprevention and will examine the mechanisms whereby zinc affects these processes in vivo by the following interrelated AIMS: 1) to define the link between NF-kappaB and COX-2 induction in rat esophagus under in vivo zinc deficit by determining whether inhibitors targeting the kappaB kinase (IKK)/NF-kappaB activation pathway, including bortezomib, PS-1145, and NF-kappaB p65 small interfering (si)RNA are effective in knocking- down COX-2 expression. Effects on COX-2 expression, proliferation, and apoptosis will be compared with effects of zinc replenishment; 2) to determine the mechanism whereby zinc deficiency increases NMBA- induced forestomach carcinogenesis in COX-2 null mice, by investigating signals in arachidonic acid metabolism, independent of COX-2; 3) to investigate cancer prevention in the ZD rat UADT cancer model by evaluating efficacy and assessing biomarker modulating effects of zinc supplementation; zinc in combination with low doses of curcumin (inhibitor of NF-kappaB), zileuton (inhibitor of 5-LOX), and with low doses of dual treatment of inhibitors. A combination of zinc and low doses of inhibitors might be effective in prevention without the risk of the side effects associated with high doses of these agents. We will evaluate in lesions the localization of specific proliferation, apoptosis, and other relevant markers by immunohistochemistry. We will then use an appropriate subset of these markers as surrogate endpoints to assess the efficacy of each chemotherapeutic regimen. We will also compare gene expression changes caused by treatments with zinc or zinc plus inhibitors. The results of these studies will provide a new understanding of the role of dietary zinc in UADT carcinogenesis, as well as a basis for novel dietary approaches for the chemoprevention of these deadly cancers.