The Role of AP-1 and Other Transcription Factors in Cancer Cause and Prevention

AP-1转录因子是Jun和Fos家族蛋白的异源二聚体，与某些基因转录启动子上的特定序列结合并驱动其转录。尽管基本的AP-1活性是正常功能所必需的，但AP-1活性的升高会在几个人类癌症部位推动肿瘤的进展。在与人类致癌相关的多种小鼠模型中，转基因小鼠中显性负性Jun的角质形成细胞特异性表达抑制了AP-1诱导的AP-1和肿瘤的形成，而不抑制细胞增殖或细胞存活(Young等人，PNAS，1999)。其中包括因人类乳头瘤病毒E7的表达而提高皮肤肿瘤促进反应的小鼠(Young等人Molec Carc 2002)和通过反复暴露于UVB而诱导形成鳞癌的小鼠(Cooper等人Molec癌症RES 2003)。四环素调控的67的表达已经被与鲍威尔·布朗合作引导到乳腺上皮细胞(沈等人，Dev Biol，2006)，最近已经被测试在预防HER2/Neu诱导的乳腺癌发生中的有效性。结果表明，AP-1阻滞剂对癌前病变以及早期和晚期肿瘤的发展具有实质性的抑制作用(Shenet al，CA Prev res，2008)。重要的是，在发生的乳腺肿瘤中，TAM67的表达被沉默。与Jay Tichelaar的实验室合作发现，可诱导的TAM67还可以抑制化学诱导的肺癌发生(癌症研究，2010年)。转录因子NFkappa B与AP-1协调调节，表明这两种因子在转化中可能具有重要作用(Li et，Cancer res 1997)。最近的观察发现，NFkB无反应性是JB6模型中转化无反应性的一个解释(Hsu等人，癌症RES 2001，Hu等人癌症发生2004年)。转化抵抗细胞由于不能激活NFkappa B p65蛋白而无反应。S536处的p65磷酸化对于DNA结合、泛素化和抑制物IkappaBα的降解是重要的(Hu等人Molec癌症2005年)。靶向AP-1和NFkB上调可防止肿瘤的推进和进展的观察已从小鼠JB6模型扩展到小鼠和人类角质形成细胞进展模型，以及转基因小鼠模型。表达AP-1/NFkB抑制因子67的转基因小鼠为鉴定AP-1或NFkB在肿瘤转化中起关键作用的靶基因提供了一个有价值的机会。表达芯片分析揭示了TAM67靶基因在驱动癌症发生中的功能意义。这样的靶基因可能是癌症预防的新的分子靶点(Young等人在2003年的Molec医学趋势中)。最近的研究已经确定染色质结构蛋白HMGA1(Dhar等人癌基因2004)、COX-2、骨桥蛋白、尿激酶型纤溶酶原激活物、CXCL1和MMP-10(Matthews等人癌症研究报告2007)作为TAM67的重要功能靶点。最近发现的TAM67/AP-1靶基因之一是硫氧还蛋白，它是一种氧化还原酶，在肿瘤促进和侵袭中都具有重要的功能，在人类癌症中也是升高的(Weq等人，2008年PNAS和2011年PNAS，2013年癌症发生)。AP-1阻滞剂最新发现的靶点是Wnt5a，它通过涉及蛋白激酶C和STAT3的非规范途径在几个模型中驱动肿瘤发生(Kang等人的基因和癌症，2012)。与分子靶标实验室合作的一个药物发现项目已经确定了模拟TAM67特异性的化合物，即抑制AP-1和/或NFkB并在不抑制细胞增殖或细胞存活的情况下防止癌症发生。对300,000种合成和天然产物进行的初步高通量筛选与细胞增殖(XTT)试验相结合，产生了一组少量的AP-1命中(Ruocco等人J Biomolec Screen 2007)。第二次试验评估了NFkB的抑制作用，并确定了一种对NFkappa B更有效的AP-1抑制剂(Kang等人Mol Ca Ther，2009)。新的化学生物学实验室CCR正在生产这种NFkappaB抑制剂的类似物，并与获得董事创新奖的Cristina Annunziata(MOB，CCR)合作，评估其对人类卵巢癌的可能效果。总而言之，该项目的最新成就包括：1)发现了AP-1调节的新基因，其衰减是导致AP-1阻滞剂TAM67抑制癌变活性的原因，特别是Sulfiredosin和Wnt5a；以及2)发现了针对AP-1或NFkappaB的新的小分子，而不抑制细胞活力。

The AP-1 transcription factor is a heterodimer of Jun and Fos family proteins that binds to a specific sequence on the transcriptional promoter of certain genes and drives their transcription. Although basal AP-1 activity is needed for normal function, elevated AP-1 activity drives tumor progression in several human cancer sites. Keratinocyte-specific expression of Dominant Negative Jun in transgenic mice inhibits induced AP-1 and tumorigenesis without inhibiting cell proliferation or cell survival in multiple mouse models relevant to human carcinogenesis (Young et al., PNAS, 1999). Among these are mice whose skin tumor promotion response is elevated by expression of Human Papilloma Virus E7 (Young et al Molec Carc 2002) and mice induced to form squamous carcinomas by repeated exposure to UVB (Cooper et al Molec Cancer Res 2003). Tetracycline regulated expression of TAM 67 has been directed to mammary epithelia in collaboration with Powel Brown (Shen et al Dev Biol 2006) and has recently been tested for efficacy in preventing HER2/Neu induced mammary carcinogenesis. The results show substantial inhibition by the AP-1 blocker of preneoplastic as well as early and later stage tumor development (Shen et al Ca Prev Res 2008). Importantly, TAM67 expression was silenced in mammary tumors that developed. Inducible TAM67 has been found also to inhibit chemically induced lung carcinogenesis in collaboration with the laboratory of Jay Tichelaar (Cancer Prev Research 2010). The transcription factor NFkappa B is coordinately regulated with AP-1, suggesting the possible importance of both factors in transformation (Li et, Cancer Res 1997). Recent observations have identified NFkB non-responsiveness as an explanation for transformation non-responsiveness in the JB6 model (Hsu et al, Cancer Res 2001, Hu et al Carcinogenesis 2004). Transformation resistant cells owe their nonresponsiveness to an inability to activate NFkappa B p65 protein. p65 phosphorylation at S536 is important for DNA binding and for ubiquitination and degradation of inhibitor IkappaB alpha (Hu et al Molec Carcinog 2005). The observation that targeting AP-1 and NFkB elevation prevents tumor promotion and progression has been extended from the mouse JB6 model to mouse and human keratinocyte progression models, and to transgenic mouse models. Transgenic mice expressing AP-1/ NFkB inhibitor TAM 67 present a valuable opportunity to identify AP-1 or NFkB target genes whose expression is critical to neoplastic transformation. Expression microarray analysis has revealed TAM67 target genes that are being queried for functional significance in driving carcinogenesis. Such target genes may be promising new molecular targets for cancer prevention (Young et al Trends in Molec Medicine 2003). Recent studies have established the importance of chromatin architectural protein HMGA1 (Dhar et al Oncogene 2004), COX-2, osteopontin, urokinase plasminogen activator, Cxcl1 and MMP-10 (Matthews et al Cancer Res 2007) as functionally significant TAM67 targets. One of the recently discovered TAM67/AP-1 target genes is sulfiredoxin, a redox enzyme that is functionally significant both in tumor promotion and invasion as well as elevated in human cancer (Wei Q, et al, PNAS 2008 and PNAS 2011, Carcinogenesis 2013). The most recently discovered target of the AP-1 blocker is Wnt5a which signals through a non-canonical pathway involving protein kinase C and STAT3 to drive oncogenesis in several models (Kang et al Genes and Cancer, 2012). A drug discovery project in collaboration with the Molecular Targets Laboratory has identified compounds that mimic the specificity of TAM67, i.e. that inhibit AP-1 and/or NFkB and prevent carcinogenesis without inhibiting cell proliferation or cell survival. The primary AP-1 high throughput screen of 300,000 synthetic and natural products coupled to a cell proliferation (XTT) assay yielded a small set of AP-1 hits(Ruocco et al J Biomolec Screening 2007). The secondary assay has assessed inhibition of NFkB and identified an AP-1 inhibitor that is even more active against NFkappa B (Kang et al Mol Ca Ther, 2009). The new Chemical Biology Laboratory, CCR is generating analogs of this NFkappaB inhibitor and collaborating with Cristina Annunziata (MOB, CCR), winner of a Directors Innovation Award to assess its possible effectivenss against human ovarian cancer. In summary, recent accomplishments for this Project include 1) the discovery of new AP-1 regulated genes whose attenuation is responsible for the carcingenesis suppressing activity of AP-1 blocker TAM67, notably Sulfiredoxin and Wnt5a, and 2) the discovery of new small molecules that target AP-1 or NFkappaB without inhibiting cell viability.