Protein Kinase C Signaling and Breast Cancer

描述（由申请人提供）：乳腺癌是女性癌症死亡的主要原因。抗雌激素药物，如他莫昔芬（Tamoxifen，Tam），通过减缓肿瘤生长、预防疾病复发和相对较少的副作用，有效治疗雌激素受体α（ER）阳性乳腺肿瘤。然而，几乎所有的反应性肿瘤最终都会产生TAM抗性。目前，Tam的抗性和/或促生长作用的机制尚不清楚。本课题组和其他研究表明雌激素诱导的MAPK激活（Erk 1和2）主要通过HRG/HER-2/PKC-δ/Ras途径介导。我们最近展示了以下内容：（a）四种抗雌激素抗性细胞系中的三种过表达总的和活化的PKC-δ，（B）在TAM敏感性MCF-7细胞中PKC-δ的过表达导致体外和体内的TAM抗性，（c）通过rottlerin或siRNA抑制PKC-δ显著逆转抗雌激素抗性，（d）与体外敏感细胞相比，先用rottlerin预处理细胞，再用TRAIL预处理细胞显著增强抗雌激素抗性细胞的凋亡，（e）在MCF-7肿瘤异种移植物中，与TAM敏感性肿瘤相比，TAM抗性肿瘤中的PKC-δ水平更高，（f）与TAM敏感性肿瘤相比，TAM耐药人类乳腺肿瘤的免疫组织化学染色显示PKC-δ水平显著增加。基于上述结果，我们推测PKC-δ的过表达和/或激活在ER阳性乳腺肿瘤细胞抗雌激素抵抗的调节中起主要作用。我们提出以下四个具体目标来检验我们的假设：目标1。我们将确定PKC-δ过表达和/或激活抑制抗雌激素抵抗细胞系凋亡的分子机制。目标二。我们将研究PKC-δ和/或其下游信号分子如何调节抗雌激素抵抗。目标3。我们将确定PKC-δ抑制剂使抗雌激素抗性细胞对TRAIL诱导的凋亡敏感的机制。目标4。我们将开发治疗策略，将体外观察结果转化为体内实际适用的治疗方法。我们预计，拟议的调查将揭示新的见解PKC-δ调节抗雌激素耐药的机制，数据应提供明确的分子靶点，为未来的临床干预治疗乳腺癌。

DESCRIPTION (provided by applicant): Breast cancer is a leading cause of cancer death among women. Antiestrogen drugs, such as tamoxifen (Tam), are effective in the treatment of estrogen receptor alpha (ER)-positive breast tumors by slowing the growth of the tumors, preventing the recurrence of the disease, and with relatively few side effects. However, almost all responsive tumors eventually develop of Tam-resistance. The mechanism(s) responsible for resistance and/or growth promoting effects of Tam are not clear at present. Studies from our group and others indicated estrogen-induced MAPK activation (Erk 1&2) is predominantly mediated by HRG/HER-2/PKC-delta/Ras pathway. We have recently shown the following: (a) Three out of four antiestrogen resistant cell lines overexpress total and activated PKC-delta, (b) Overexpression of PKC-delta in Tam-sensitive MCF-7 cells leads to Tam-resistance both in vitro and in vivo, (c) Inhibition of PKC-delta by rottlerin or siRNA significantly reversed antiestrogen resistance, (d) Pretreatment of cells with rottlerin followed by TRAIL significantly enhanced apoptosis in antiestrogen resistant cells compared with sensitive cells in vitro, (e) PKC-delta levels are higher in Tam-resistant tumors compared to Tam-sensitive tumors in MCF-7 tumor xenograft, (f) Immunohistochemical staining of Tam-resistant human breast tumors showed a significant increase of PKC-delta levels compared with those in Tam-sensitive tumors. Based on the above results, we hypothesize that overexpression and/or activation of PKC-delta plays a major role in the regulation of antiestrogen resistance in ER-positive breast tumor cells. We are proposing the following four specific aims to test our hypotheses: Aim 1. We will determine the molecular mechanism by which PKC-delta overexpression and/or activation suppresses apoptosis in antiestrogen resistant cell lines. Aim 2. We will investigate how PKC-delta and/or its down stream signaling molecules regulate antiestrogen resistance. Aim 3. We will determine mechanism by which PKC-delta inhibitors sensitizes antiestrogen resistant cells to TRAIL-induced apoptosis. Aim 4. We will develop treatment strategies to translate in vitro observations into practically applicable therapies in vivo. We anticipate that the proposed investigations would reveal novel insights into the mechanism by which PKC-delta regulates antiestrogen-resistance and the data should provide defined molecular target(s) for future clinical intervention for the treatment of breast cancer.