ROLE OF AP-1 AND OTHER TRANSCRIPTION FACTORS IN CANCER CAUSE AND PREVENTION

这项研究的总体目标是鉴定和表征基因 在肿瘤促进过程中推动限速步骤的调节事件 和肿瘤的进展。AP-1转录因子是一种异源二聚体 Jun和Fos家族蛋白与细胞上的特定序列结合 某些基因的转录启动子，并驱动它们的 抄写。我们1989年的观察(伯恩斯坦和科尔本，科学， 1989)，转换敏感(P+)，但不转换 耐药(P-)小鼠JB6细胞对肿瘤促进剂的反应 激活AP-1依赖的转录，表明AP-1激活 可能需要从癌前病变进展到 肿瘤(肿瘤)表型。对这一假说的检验表明， 药物抑制剂、糖皮质激素和维甲酸及其“基因” 治疗“抑制剂显性阴性Jun(TAM67)阻断AP-1 激活和转化反应。这一点已经扩展到显示 转译AP-1活性的特定维甲酸没有 反式激活视黄酸反应元件(REARE)依赖基因 转录，也能防止肿瘤转化(Li等人，癌症 Res，1996)。令人惊讶的是，TPA诱导了，但没有肿瘤坏死因子 在α诱导下，AP-1对维甲酸的反式抑制反应敏感。这个 控制这种敏感性差异的极限分子相互作用 似乎涉及cjun(Li et，癌症资源1997)。显性否定 角蛋白14(K14)启动子驱动的Jun突变体(TAM67)，当 在小鼠角质形成细胞系308中的表达同时抑制AP-1和NFkB 转录因子活性以及诱导侵袭 Matrigel(董等人，Molec.癌症，1997)暗示了可能的 第二个转录因子NFkB在病因和发病机制中的重要性 预防疾病进展。AP-1和NFkB活性与DNA结合 在人类角质形成细胞进展模型中显示进行性升高。 当转基因K14-TAM67在更进展的阶段表达时 致瘤性或锚定非依赖性的人类细胞系，肿瘤 细胞表型被抑制(Li等人，提交给癌基因)。 TAM67在小鼠JB6 P+细胞中的表达引起表型逆转 细胞在裸鼠移植床上生长时对P表型的影响 (Strickland等人，癌症。1997年)。表达K-蛋白的转基因小鼠 已产生14-TAM67转基因。这些K14-67号小鼠现在有 已显示在两种DMBA-TPA启动促进皮肤癌的发生中 实验表明，95%的保护作用不会促进皮肤 致癌，即预防癌前乳头状瘤的形成。 (Young等人，《正在准备中》)。最近我们发现， JB6 P变种的转化抗性是由于缺乏 MAPK信号通路ERK1和ERK2对AP-1也有限制作用 激活(Huang等人，PNAS，正在出版中)。因此，观察到 靶向AP-1和NFkB的上调可阻止肿瘤的促进和 进展已经从小鼠JB6模型扩展到小鼠和 人角质形成细胞进展模型及移植和转基因 老鼠模型。对极限分子相互作用的新理解是 正在浮现。

The overall aim of this research is to identify and characterize gene regulation events that propel rate limiting steps during tumor promotion and tumor progression. 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. Our 1989 observation (Bernstein and Colburn, Science, 1989) that transformation sensitive (P+) but not transformation resistant (P-) mouse JB6 cells responded to tumor promoters by activating AP-1 dependent transcription, suggested that AP-1 activation might be required for progression from preneoplastic to neoplastic(tumor)phenotype. Testing of this hypothesis revealed that the pharmacologic inhibitors, glucocorticoids and retinoids and the "gene therapy" inhibitor dominant negative jun (TAM67) blocked both AP-1 activation and transformation response. This has been extended to show that specific retinoids that transrepress AP-1 activity without transactivating retinoic acid response element (RARE) dependent gene transcription, also prevent neoplastic transformation (Li et al., Cancer Res, 1996). Surprisingly TPA induced, but not tumor necrosis factor alpha induced, AP-1 is sensitive to transrepression by retinoid. The limiting molecular interaction governing this sensitivity difference appears to involve cJun (Li et, Cancer Res 1997). The dominant negative jun mutant(TAM67) transgene driven by a keratin 14(K14)promoter, when expressed in a mouse keratinocyte line 308 suppressed both AP-1 and NFkB transcription factor activities as well as induced invasion into matrigel (Dong et al., Molec. Carcinog.,1997)suggesting the possible importance of a second transcription factor NFkB in both the cause and prevention of progression. Both AP-1 and NFkB activities and DNA binding show progressive elevation in a human keratinocyte progression model. When the transgene K14-TAM67 is expressed in the more progressed stage human cell lines that are tumorigenic or anchorage independent, tumor cell phenotype is suppressed (Li et al., submitted to Oncogene). Expression of TAM67 in mouse JB6 P+ cells produced phenotypic reversion to P- phenotype when cells were grown on a nude mouse graft bed (Strickland et al., Carcinog. 1997). Transgenic mice expressing the K- 14-TAM67 transgene have been generated. These K14-TAM 67 mice have now been shown in two DMBA-TPA initiation-promotion skin carcinogenesis experiments to show 95% protection against promotion of skin carcinogenesis, i.e., prevention of premalignant papilloma formation. (Young et al., Ms in preparation). Recently we have found that the transformation resistance of a JB6 P- variant is due to a shortage of the MAPK kinases Erks 1 and 2 which are also limiting for AP-1 transactivation (Huang, et al, PNAS, in press). Thus the observation that targetting 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 grafting and transgenic mouse models. New understanding of limiting molecular interactions is emerging.