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

本研究的总体目标是识别和表征基因 在肿瘤促进过程中推动限速步骤的调节事件 和肿瘤进展。AP-1转录因子是一种异源二聚体 Jun和Fos家族蛋白结合到一个特定的序列上， 某些基因的转录启动子，并驱动其 转录。我们1989年的观察（伯恩斯坦和科尔本，科学， 1989），转化敏感（P+），但不是转化 抗性（P-）小鼠JB6细胞通过以下方式对肿瘤促进剂作出应答： 激活AP-1依赖性转录，表明AP-1激活 可能需要从癌前病变进展到 肿瘤表型。对这一假设的检验表明， 药理学抑制剂、糖皮质激素和维甲酸以及"基因 治疗"抑制剂显性阴性jun（TAM 67）阻断AP-1和AP-2， 激活和转化反应。这已经被扩展到显示 特异性类维生素A反式抑制AP-1活性， 反式激活视黄酸反应元件依赖基因 转录，也防止肿瘤转化（Li等，癌 Res，1996年）。令人惊讶的是，TPA诱导，但不是肿瘤坏死因子 在α诱导的情况下，AP-1对类维生素A的反式阻遏敏感。的 限制了控制这种灵敏度差异的分子相互作用 似乎涉及cJun（Li et，Cancer Res 1997）。所述显性负性 由角蛋白14（K14）启动子驱动的jun突变体（TAM67）转基因，当 在小鼠角质形成细胞系308中表达的一种蛋白抑制AP-1和NF κ B 转录因子活性以及诱导侵入 基质胶（Dong等人，Molec.巨蟹座，1997)这表明 第二个转录因子NF κ B的重要性，在这两个原因， 预防进展。AP-1和NF κ B活性和DNA结合 显示在人角质形成细胞进展模型中进行性升高。 当转基因K14-TAM 67在更进展的阶段表达时， 致瘤性或非锚定依赖性的人细胞系，肿瘤 细胞表型被抑制（Li等，提交给Oncogene）。 TAM 67在小鼠JB6 P+细胞中的表达产生表型逆转 当细胞在裸鼠移植床上生长时， （斯特里克兰等人，巨蟹座1997年）。转基因小鼠表达的K- 14-TAM67转基因已经产生。这些K14-TAM 67小鼠现在 在两个DMBA-TPA启动-促进皮肤癌变中显示 实验显示95%的保护对促进皮肤 致癌作用，即，预防癌前乳头状瘤形成。 （Young等人，准备中）。最近我们发现， JB6 P-变体的转化抗性是由于缺乏 MAPK激酶Erks 1和2也限制AP-1 反式激活（Huang等人，PNAS，出版中）。因此， 靶向AP-1和NFkB升高可防止肿瘤促进， 进展已经从小鼠JB6模型扩展到小鼠， 人角质形成细胞进展模型，以及移植和转基因 小鼠模型。对限制分子相互作用的新认识是 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.