RETINOID RECEPTOR FUNCTION IN SKIN CANCER PROGRESSION

鳞状细胞癌(SCC)是临床上侵袭性最强的恶性肿瘤。 非黑色素瘤皮肤癌，尽管进行了积极的治疗， 侵袭性鳞癌病变复发率高(30%)。因此在那里 迫切需要开发改进的治疗和治疗方法 这种疾病的预防性治疗。维甲酸很重要 上皮分化和增殖的调节剂。维甲酸 对治疗和预防上皮癌是有效的， 包括皮肤鳞状细胞癌。然而，这种效应的机制并不是 很好理解。为了更好地设计化学预防疗法 对于皮肤鳞状细胞癌，更多关于维甲酸机制的信息 在这个系统中需要采取行动。维甲酸发挥作用 主要通过核受体、维甲酸受体(RARpha， β和γ)和维甲酸X受体(RXRα、β和伽马)， 类固醇激素受体超家族的成员。维甲酸受体 在几个系统中，丢失与恶性肿瘤有关，其中一个 最近的研究表明，对RARAlpha、RARGamma和 RXRα在患者皮肤上皮细胞中的表达。这项研究是基于 维甲酸受体缺失与恶性肿瘤的关系假说 通过使上皮细胞对维甲酸产生抗性而产生表型 Wold通常会抑制致癌作用。为了检验这一假设，HaCaT 细胞，一种自发永生化的，不会致癌的角质形成细胞- 选择来源细胞系。这些细胞表达两种主要的 维甲酸受体通常存在于皮肤、RARGamma和RXRpha中，以及 保持相同的差异化特征和响应 视黄酸与正常角质形成细胞相似。HaCaT细胞，这是一个模型 对于癌前细胞，将用于完成以下任务 具体目标：1.)要创建RARGamma空值、RXTalpha空值和 同源重组介导的RARGamma/RXRpha双零细胞 基因打靶。2.)以确定受体表达的缺失 导致细胞表型改变，特别是在 成瘤潜能、分化能力和对 维甲酸(RA)水平的变化。3.)重新表达思念之情 稳定的基因敲除细胞系中的受体(RARGamma或RXRpha) 以确定假定的表型 观察到的是遗传损伤的直接结果。体细胞 基于这一原理，基因打靶技术已获得成功。 研究人员分析F9胚胎中维甲酸受体的功能 癌细胞。预计受体Null的产生 HaCaT细胞将提供一个同样强大的工具来理解 维甲酸受体在皮肤鳞状细胞癌发生发展中的作用 因为它们在表皮分化中的作用。

Squamous cell carcinoma (SCC) is the most clinically aggressive form of non-melanoma skin cancer and in spite of aggressive treatment, deeply invasive SCC lesions recur at a high rate (30 percent). Therefore there is an urgent need for the development of improved therapeutic and preventive treatments for this disease. Retinoids are important modulators of epithelial differentiation and proliferation. Retinoids are effective in the treatment and prevention of epithelial cancers, including cutaneous SCC. However the mechanism for this effect is not well understood. In order to better design chemopreventive therapies for cutaneous SCC, more information about the mechanism of retinoid action in this system is needed. Retinoids exert their effects primarily through nuclear receptors, retinoic acid receptors (RARalpha, beta and gamma) and retinoid X receptors (RXRalpha, beta and gamma), members of the steroid hormone receptor superfamily. Retinoid receptor loss has been correlated with malignancy in several systems, and one recent study has demonstrated a suppression of RARalpha, RARgamma and RXRalpha expression in SCCs of patients. This study is based on the hypothesis that retinoid receptor loss contributes to the malignant phenotype by rendering epithelial cells resistant to retinoids, which wold normally suppress carcinogenesis. To test this hypothesis, HaCaT cells, a spontaneously immortalized, nontumorigenic, keratinocyte- derived cell line was chose. These cells express the two predominant retinoid receptors normally found in skin, RARgamma and RXRalpha, and retain the same differentiation characteristics and response to retinoids as normal keratinocytes. The HaCaT cells, which are a model for premalignant cells, will be used to accomplish the following specific aims: 1.) To create RARgamma null, RXTalpha null and RARgamma/RXRalpha double null cells by homologous recombination-mediated gene targeting. 2.) To determine whether loss of receptor expression results in an altered cell phenotype, specifically with regard to tumorigenic potential, differentiation capacity and response to alterations in retinoic acid (RA) levels. 3.) To reexpress the missing receptor (RARgamma or RXRalpha) in the knockout cell lines by stable transfection in order to determine whether the putative phenotype observed is the direct result of the genetic lesion. A somatic cell gene targeting approach has been successfully by the principle investigator to analyze retinoid receptor function in F9 embryonal carcinoma cells. It is expected that the generation of receptor null HaCaT cells will provide an equally powerful tool for understanding the role of retinoid receptors in the development of cutaneous SCC, as well as their role in epidermal differentiation.