Role of JAK2-PAK1 interaction in human breast cancer

描述(申请人提供)：乳腺癌是女性的主要癌症类型，也是女性癌症死亡的第二大原因。根据美国女性目前的预期寿命，每9名女性中就有1人在有生之年患上乳腺癌--1960年，这一风险为每14人中就有1人患上乳腺癌。肿瘤转移仍然是乳腺癌死亡的主要原因。虽然化疗和放射治疗在某些情况下预后有所改善，但这些方法往往会导致严重的副作用。两种蛋白质-JAK2和PAK1-被认为与乳腺癌有关。酪氨酸激酶JAK2是催乳素受体结合的信号分子。催乳素受体在80%的人类乳腺癌中检测到，并在乳腺癌细胞中过度表达。正常和肿瘤乳腺上皮细胞合成催乳素和催乳素受体，因此催乳素可以作为一种自分泌生长因子作用于人乳腺癌细胞。丝氨酸-苏氨酸激酶PAK1与乳腺癌的关系有多种证据：(A)PAK1基因扩增和/或PAK1蛋白上调在乳腺癌中被报道；(B)激活的PAK1增加了乳腺癌细胞的细胞侵袭力；(C)PAK1参与了几个不同的丝裂原激活的蛋白激酶级联反应的激活或调节，导致细胞增殖增加； (D)PAK1通过提高细胞存活率促进癌变表型。初步数据 证明PAK1与JAK2结合并被JAK2磷酸化。二维肽 作图鉴定了3个被JAK2磷酸化的PAK1Tyr(S)。JAK2对PAK1的酪氨酸磷酸化也显示出保护细胞免于凋亡和增加细胞活力的作用。这项资助建议检验一种假说，即依赖JAK2的酪氨酸磷酸化的PAK1激活PAK1，增加细胞增殖，并导致人类乳腺细胞的非锚定生长和侵袭性。AIM1将确定PAK1的JAK2磷酸化是否通过促进细胞增殖和/或锚定非依赖性生长来改变人乳腺细胞的体外生长特性。AIM2将确定PAK1的JAK2磷酸化是否通过增加细胞运动和/或降低细胞黏附而导致人乳腺细胞侵袭性。虽然JAK2和PAK1在乳腺癌中的重要性得到了广泛的承认，但其涉及的机制仍然知之甚少。在我们对乳腺癌进展机制的理解中，上游的JAK2依赖的事件和下游的PAK1和PAK1依赖的功能之间存在差距。令人兴奋的初步数据表明，PAK1是一个重要的信号分子，被JAK2磷酸化，参与细胞生存。这些研究结果将为JAK2对PAK1酪氨酸磷酸化调控细胞增殖和侵袭性的基本机制提供重要的见解。这也将为JAK2和PAK1参与乳腺癌的可能机制提供必要的见解。我们认为，JAK2对PAK1酪氨酸的磷酸化可能是探索人类乳腺癌病因和治疗的一个新的分子靶点。 公共卫生相关性：乳腺癌是女性最常见的确诊癌症--近三分之一(30%)的女性癌症发生在乳房。根据美国女性目前的预期寿命，每9名女性中就有1人在有生之年患上乳腺癌--1960年，这一风险为每14人中就有1人患上乳腺癌。关于正常细胞成为癌细胞的分子生物学机制，仍有许多未知之处。正常的细胞行为受到多个信号通路的严格控制，这些信号通路确保细胞只有在身体需要时才会增殖。当正常的生长调节被破坏时，癌症就会发生，通常是因为这些信号机制的缺陷。转移，即癌症扩散到身体的远处，实际上是癌症如此致命的原因。外科医生可以相对容易地切除原发肿瘤，但转移的癌症通常会到达如此多的地方，仅靠手术治愈是不可能的。细胞转移的能力也受到多条信号通路的调节。两种蛋白质-JAK2和PAK1-参与了导致乳腺癌的细胞通路的调节，但它们是如何协同工作的，以及它们的确切作用机制尚不清楚。我们的长期目标是了解控制细胞分裂和细胞运动的分子机制，以及导致人类乳腺癌的失调。为此，我们已经开始分析JAK2与 和PAK1。我们发现JAK2与PAK1结合，并使PAK1更具活性。激活的PAK1有助于更好的细胞存活，这可能会促进癌症的发展。在目前的提案中，我们将研究JAK2和PAK1如何促进细胞增殖和细胞迁移，从而导致转移。了解这些蛋白质是如何共同作用的，将有助于设计新的治疗方法，并可能设计治疗人类乳腺癌的药物。

DESCRIPTION (provided by applicant): Breast cancer is the leading type of cancer in women and is the second leading cause of cancer death among women. Based on the current life expectancy for women in the United States, 1 out of 9 women will develop breast cancer in her lifetime - a risk that was 1 out of 14 in 1960. Tumor metastasis still remains the main cause of breast cancer death. Although with chemotherapy and radiation therapy, the prognosis has improved in some cases, these approaches often result in severe side effects. Two proteins - JAK2 and PAK1-have been implicated in breast cancer. Tyrosine (Tyr) kinase JAK2 was identified as a prolactin receptor-bound signaling molecule. The prolactin receptor is detected in 80% of human breast cancers and is overexpressed in breast cancer cells. Normal and tumor mammary epithelial cells synthesize prolactin and prolactin receptor, thus the prolactin could behave as an autocrine growth factor for human breast cancer cells. Serine-threonine kinase PAK1 has been linked to breast cancer by several lines of evidence: (a) PAK1 gene amplification and/or PAK1 protein up-regulation have been reported in breast cancers; (b) activated PAK1 increased cell invasion of breast cancer cells; (c) PAK1 is involved in the activation or regulation of several distinct mitogen-activated protein kinase cascades that lead to increased proliferation; (d) PAK1 contributes towards cancerous phenotypes by enhancement of cell survival. Preliminary data demonstrate that PAK1 associates with and is Tyr phosphorylated by JAK2. Two-dimensional peptide mapping identified three Tyr(s) of PAK1 which are phosphorylated by JAK2. Tyr phosphorylation of PAK1 by JAK2 was also shown to protect cells from apoptosis and increase cell motility. This grant proposes to examine the hypothesis that JAK2-dependent tyrosyl phosphorylation of PAK1 activates PAK1, increases cell proliferation, and causes anchorage-independent growth and invasiveness of human breast cell. Aim1 will determine whether JAK2 phosphorylation of PAK1 alters in vitro growth properties of human breast cells by promoting cells proliferation and/or anchorage-independent growth. Aim2 will determine whether JAK2 phosphorylation of PAK1 causes human breast cell invasiveness by increasing cell motility and/or decreasing cell adhesion. Although the significance of both JAK2 and PAK1 in breast cancer is widely acknowledged, the mechanism involved remains poorly understood. There is a gap between upstream JAK2-dependent events and downstream PAK1 and PAK1-dependent functions in our understanding of the mechanism of breast cancer progression. Exciting preliminary data suggest that PAK1 is an important signaling molecule phosphorylated by JAK2 and participating in cell survival. The results of the proposed studies will provide important insight into the fundamental mechanism by which tyrosyl phosphorylation of PAK1 by JAK2 regulates cell proliferation and invasiveness. It will also provide needed insight into the possible mechanism by which JAK2 and PAK1 participate in breast cancer. We believe that tyrosyl phosphorylation of PAK1 by JAK2 is likely to represent a novel molecular target in the search for theetiology and treatment of human breast cancer. PUBLIC HEALTH RELEVANCE: Breast cancer is the most commonly diagnosed cancer in women - nearly 1 in 3 (30%) of all cancers in women occur in the breast. Based on the current life expectancy for women in the United States, 1 out of 9 women will develop breast cancer in her lifetime - a risk that was 1 out of 14 in 1960. Much is still unknown regarding the molecular biological mechanism by which a normal cell becomes a cancer cell. Normal cell behavior is tightly controlled by multiple signaling pathways that ensure that cells proliferate only when they are required by the body. Cancer occurs when normal growth regulation breaks down, usually because of a defect in these signaling mechanisms. Metastasis, the spread of cancer to distant sites in the body, is in fact what makes cancer so lethal. A surgeon can remove a primary tumor relatively easily, but a cancer that has metastasized usually reaches so many places that cure by surgery alone becomes impossible. The ability of cells to metastasize is also regulated by multiple signaling pathways. Two proteins - JAK2 and PAK1 -have been implicated in the regulation of cell pathways that can lead to breast cancer but how they work together and the precise mechanism of their action is unknown. Our long term goal is to understand the molecular mechanisms that control cell division and cell motility and disregulation of which leads to human breast cancer. Toward this aim, we have started to analyze the relationship between JAK2 and PAK1. We showed that JAK2 binds to PAK1 and makes PAK1 more active. Activated PAK1 contributes to better cell survival that may promote cancer development. In the current proposal we will study how JAK2 and PAK1 increase cell proliferation and cell migration that leads to metastasis. In understanding of how these proteins work together will help to design new therapeutic approaches and possibly drugs for treatment of human breast cancer.