Cell Cycle Dysregulation in Oral Cancer

描述(申请人提供)：头颈癌被认为是通过一个多步骤的过程起源的，其中涉及癌基因的激活和肿瘤抑制基因的失活，然而，具体的进展模式和必要的基因改变尚未被描述。尽管在过去的30年里，治疗取得了进展，但存活率的改善很少或根本没有。识别正常细胞向恶性细胞转化过程中涉及的特定基因或蛋白质，以及这些基因或蛋白质的特定序列，对于开发早期检测方法、制定新的治疗策略和预测患者预后是必要的。虽然口腔肿瘤发生的研究对头颈癌患者特别有益，但这类研究也可能有助于从总体上理解多步骤癌症发生。要将这些优势转化为可能有益于口腔癌患者的治疗程序，必须了解口腔癌发生过程中涉及的基本分子变化。为此，我们研究了口腔癌发生过程中细胞周期失调的机制。与大多数人类肿瘤一样，口腔癌细胞中常见的肿瘤抑制基因p53(但不是其调控因子pl4ARF)和pRB途径被破坏。最有趣的是，我们发现PRB调节因子CDK6在口腔癌细胞中通过各种机制优先过度激活，而相关的激酶CDK4的活性水平与在原代细胞中观察到的水平相似。这些数据补充了我们实验室和其他实验室的一些研究，这些研究表明CDK4和CDK6在诱导所有类型的细胞增殖方面并不相同，可能在肿瘤发生中具有不重叠的作用。此外，p16INK4a对这两种激酶的抑制可以导致口腔癌细胞株的衰老状态，这表明CDK4和/或CDK6的持续活性是肿瘤细胞增殖所必需的。为了更好地了解这些pRB途径调控因子在口腔癌中的作用和细胞周期失调的一般过程，我们提出了三个具体的目标：(1)通过分别调控正常口腔上皮细胞和口腔癌细胞中细胞周期调节因子的活性来构建和解构口腔癌细胞。这将测试口腔癌细胞中抗增殖剂的可疑靶点，并将阐明已知细胞周期调节因子失调的后果。(2)可逆性抑制CDK4、CDK6或同时抑制CDK4和CDK6，诱导口腔癌细胞衰老和凋亡，使其成为治疗的靶点。(3)检测13号染色体基因编码的CDK4/CDK6相互作用蛋白CLLL7的生物学活性。

DESCRIPTION (provided by applicant): Head and neck cancer is believed to originate via a multi-step process that involves the activation of oncogenes and inactivation of tumor suppressor genes, however, the specific pattern of progression and the necessary genetic alterations have not been delineated. Although treatment advances have been made in the last 30 years, little or no survival improvement has been obtained. Identifying the specific genes or proteins involved in transformation of a normal cell to a malignant cell, and the particular sequence of these genes or proteins, is necessary for the development of early detection methods, the formulation of new treatment strategies, and the prediction of patient outcome. While studies on oral tumorigenesis are specifically beneficial to head and neck cancer patients, such studies are likely to also aid the understanding of multi-step carcinogenesis in general. To translate these advantages into procedures that may be beneficial to oral cancer patients, the basic molecular changes involved in oral cancer development must be understood. To this end we investigated the mechanism of cell cycle dysregulation in oral cancer development. As with most human tumors, the common tumor suppressor p53 (but not its regulator pl4ARF) and the pRb pathway are disrupted in oral cancer cells. Most interestingly, we found that the pRb regulator cdk6 is preferentially hyperactivated in oral cancer cells by a variety of mechanisms, while the related kinase cdk4 is active at levels similar to those observed in primary cells. These data complement a number of studies in our labs and others that indicate that cdk4 and cdk6 are not equivalent in their ability to induce proliferation in all cell types and may have non-overlapping roles in tumorigenesis. Further, inhibition of both kinases by p 16INK4a can lead to a senescent state in oral cancer cell lines, indicating that continued activity of cdk4, cdk6 or both is required for tumor cell proliferation. In order to better understand the roles of these pRb pathway regulators and the process of cell cycle dysregulation in general in oral cancer, we propose three specific aims: (1) construct and deconstruct oral cancer cells by manipulating the activity of cell cycle regulators in normal oral epithelial cells and oral cancer cells respectively. This will test suspected targets for antiproliferative agents in oral cancer cells and will elucidate the consequences of dysregulation of known cell cycle regulators. (2) Reversibly inhibit cdk4, cdk6 or both in order to induce senescence and apoptosis in oral cancer cells and thus validate them as targets for therapy. (3) Determine the biological activity of CLLL7, a novel cdk4/cdk6 interacting protein encoded by a gene on chromosome 13.