Regulation of Ovarian Cancer Multidrug Resistance by MAP Kinases

描述（申请人提供）：许多卵巢肿瘤对初始药物治疗有反应，但复发后对药物治疗无效。因此，确定耐药性的机制对于现有的和新的癌症治疗是重要的。选择性mRNA剪接影响74%的人类基因组。选择性mRNA剪接因子表达的改变发生在癌症中，并且可以强烈影响凋亡反应。剪接因子SPF45在卵巢癌细胞中的过表达导致他莫昔芬敏感的耐药表型SPF 45介导的耐药性机制尚不清楚。许多化学治疗剂和细胞刺激物诱导有丝分裂原活化蛋白激酶（MAP激酶）ERK、JNK和p38的活化，所有这些都与通过其蛋白质底物的磷酸化调节细胞存活反应有关。目前，Sam68是唯一已知的受MAP激酶磷酸化影响的剪接因子。我们已经确定了SPF45作为所有三种MAP激酶的新底物，并确定了SPF45上的两个磷酸化位点。我们产生磷酸特异性抗体，并已显示SPF45磷酸化在人腹水和细胞系中的化疗药物，氧化应激，佛波酯和紫外线照射。最重要的是，SPF45在Ser222上被MAP激酶磷酸化增加了其可变剪接活性。这些数据有力地证明了MAP激酶、SPF 45磷酸化、可变剪接活性和耐药性之间的直接联系。本申请的总体目标是确定SPF 45介导耐药性的机制以及如何通过SPF 45的MAP激酶磷酸化调节耐药性。这些研究将能够识别治疗干预的新靶点，以对抗SPF 45过表达肿瘤的耐药性。我们推测，MAP激酶磷酸化的SPF 45在响应化疗药物增强耐药表型刺激SPF 45选择性剪接活性。我们将通过以下具体目标来检验这一假设：具体目标1。产生针对SPF 45的磷酸化特异性抗体。确定MAP激酶特异性SPF45磷酸化模式响应于化疗剂的变化，并确定涉及的激酶。具体目标2。确定MAP激酶磷酸化对SPF45剪接活性的影响，使用？Fas微基因检测通过外显子阵列分析确定SPF 45的新剪接靶点，并确定这些靶点导致SPF 45介导的耐药性的机制。具体目标3。阐明SPF45及其磷酸化在肿瘤前和肿瘤性卵巢细胞系、裸鼠肿瘤和人恶性腹水中对化疗药物治疗的反应中的作用。明确雌激素受体在SPF 45介导的耐药性中的作用。公共卫生相关性：卵巢肿瘤经常对化疗药物产生耐药性，但其机制知之甚少。我们假设这种现象部分是由细胞内信号通路的能力调节的，该信号通路在癌细胞中通常被过度激活，以化学修饰在耐药性中具有已知作用的蛋白质。阐明这种协同耐药机制将为治疗耐药卵巢癌提供重要信息。

DESCRIPTION (provided by applicant): Many ovarian tumors respond to initial drug therapy, but become refractory to drug treatment upon recurrence. Therefore, defining the mechanisms of drug resistance is important for existing and new cancer therapies. Alternative mRNA splicing affects 74% of the human genome. Alterations in alternative mRNA splicing factor expression occur in cancer and can strongly influence apoptotic responses. Over-expression of the splicing factor SPF45 in ovarian cancer cells results in a tamoxifen sensitive drug-resistant phenotype. The mechanism of SPF45-mediated drug resistance is unknown. Numerous chemotherapeutic agents and cellular stimuli induce activation the mitogen-activated protein kinases (MAP kinases) ERK, JNK and p38, all of which are associated with modulating cell survival responses through phosphorylation of their protein substrates. Currently, Sam68 is the only known splicing factor affected by MAP kinase phosphorylation. We have identified SPF45 as a novel substrate of all three MAP kinases and identified two phosphorylation sites on SPF45. We generated phospho-specific antibodies and have shown SPF45 phosphorylation in human ascites and in cell lines in response to chemotherapeutic drugs, oxidative stress, phorbol esters and UV irradiation. Most importantly, phosphorylation of SPF45 on Ser222 by MAP kinases increases its alternative splicing activity. These data strongly demonstrate a direct link between MAP kinases, SPF45 phosphorylation, alternative splicing activity and drug resistance. The overall objective of this application is to define the mechanism by which SPF45 mediates drug resistance and how resistance is regulated by MAP kinase phosphorylation of SPF45. These studies will enable the identification of novel targets for therapeutic intervention to combat drug resistance in SPF45 over-expressing tumors. We hypothesize that MAP kinase phosphorylation of SPF45 in response to chemotherapeutic agents enhances the drug resistant phenotype by stimulating SPF45 alternative splicing activity. We will test this hypothesis through the following Specific Aims: Specific Aim 1. Generate phospho-specific antibodies to SPF45. Identify the changes in MAP kinase- specific SPF45 phosphorylation patterns in response to chemotherapeutic agents and identify the kinase(s) involved. Specific Aim 2. Determine the effect of MAP kinase phosphorylation on SPF45 splicing activity using the ?fas minigene assay. Identify novel splicing targets of SPF45 by exon array analysis and identify the mechanism by which these targets contribute to SPF45-mediated drug resistance. Specific Aim 3. Elucidate the role of SPF45 and its phosphorylation in the response to chemotherapeutic agent treatment in pre-neoplastic and neoplastic ovarian cell lines, tumors in nude mice and in malignant human ascites. Define the role o estrogen receptors in SPF45-mediated drug resistance. PUBLIC HEALTH RELEVANCE: ovarian tumors often develop resistance to chemotherapeutics, but the mechanisms are poorly understood. We hypothesize that this phenomenon is regulated in part by the ability of an intracellular signaling pathway that is often hyper-activated in cancer cells to chemically modify a protein with a known role in drug resistance. Elucidation of this synergistic mechanism of drug resistance would provide important information for treating drug-resistant ovarian cancer.