Cell Cycle Dysregulation in Oral Cancer

描述（由申请人提供）：头颈癌被认为起源于一个多步骤的过程，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遗传改变尚未被描述。尽管在过去的30年里治疗已经取得了进展，但很少或没有获得生存改善。识别参与正常细胞向恶性细胞转化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，但这些研究也可能有助于了解一般的多步骤癌变。为了将这些优势转化为可能对口腔癌患者有益的手术，必须了解口腔癌发展过程中涉及的基本分子变化。为此，我们研究了细胞周期失调在口腔癌发展中的机制。与大多数人类肿瘤一样，常见的肿瘤抑制因子p53（而不是其调节因子pl4ARF）和pRb通路在口腔癌细胞中被破坏。最有趣的是，我们发现pRb调节因子cdk6在口腔癌细胞中通过多种机制优先高激活，而相关激酶cdk4的活性水平与在原代细胞中观察到的相似。这些数据补充了我们实验室和其他人的一些研究，这些研究表明cdk4和cdk6在所有细胞类型中诱导增殖的能力并不等同，并且可能在肿瘤发生中具有不重叠的作用。此外，p16ink4a抑制这两种激酶可导致口腔癌细胞系的衰老状态，这表明肿瘤细胞增殖需要cdk4、cdk6或两者的持续活性。为了更好地了解这些pRb通路调节因子的作用以及细胞周期失调在口腔癌中的总体过程，我们提出了三个具体目标：(1)分别通过操纵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药物的可疑靶点，并将阐明已知细胞周期调节因子失调的后果。(2)可逆抑制cdk4、cdk6或两者同时抑制，诱导口腔癌细胞衰老和凋亡，从而验证其作为治疗靶点的可行性。(3)确定13号染色体上一个基因编码的cdk4/cdk6相互作用蛋白CLLL7的生物活性。

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.