Prolactin as a Growth Factor in Breast Cancer

描述（申请人提供）：化疗是晚期乳腺癌的主要治疗手段，但肿瘤耐药是导致治疗失败的主要障碍。耐药由多种原因引起，包括药物外排、失活、促/抗凋亡蛋白或肿瘤抑制基因表达改变以及DNA修复机制增加。我们提出的证据表明，催乳素（PRL）作为一种生存因子，可以拮抗dna损伤剂顺铂和阿霉素以及微管破坏剂紫杉醇的细胞毒性。PRL通过激活解毒酶谷胱甘肽- s转移酶（GST）以及增加抗凋亡蛋白Bcl-2的表达来保护乳腺癌细胞（BCC）免受药物的侵害。人的乳房从两个来源接收PRL输入：垂体和局部。在乳腺内，基质脂肪细胞比上皮细胞产生更多的PRL，两者都受到强直抑制。我们发现多巴胺受体（DAR）在乳腺组织、脂肪细胞和基底细胞中表达。与其对垂体PRL的作用类似，多巴胺和溴隐亭（Br）抑制乳腺PRL的产生。本地产生的PRL可能会产生化学耐药，因为内源性PRL高的BCC比低PRL的BCC更耐药。我们新开发的LS14人脂肪细胞系，产生PRL并表达PRL受体（PRL- r），也对许多抗癌药物具有耐药性。假设：PRL通过激活解毒酶、抗凋亡蛋白或两者兼而有之，赋予对不同种类抗癌药物的化学耐药性。乳腺肿瘤的PRL输入来自循环（垂体）、旁分泌（基质脂肪细胞）和自分泌（BCC）。与多巴胺对垂体的作用类似，多巴胺抑制乳腺PRL，从而使乳腺癌对抗癌药物敏感。目的1：比较PRL和PRL- r在BCC中mRNA和蛋白水平的表达，并通过敲低和过表达来确定局部PRL在化疗耐药中的作用。目的2：研究GST和/或Bcl-2是否介导PRL对四类药物的化疗耐药：dna损伤、微管改变、抗代谢产物和死亡配体TRAIL（肿瘤坏死因子（TNF）相关的凋亡诱导配体）。目的3：表征脂肪细胞、BCC和LS14细胞中的DAR，并确定多巴胺及其激动剂是否抑制PRL的产生并增加细胞对抗癌药物的敏感性。目的4：建立完全分化的LS14脂肪细胞和BCC的混合培养，研究多巴胺激动剂是否使胸腺小鼠LS14/BCC肿瘤对抗癌药物敏感。临床影响：口服多巴胺激动剂在抑制PRL方面具有良好的安全性和有效性，已获得fda批准。在接受化疗的乳腺癌患者中使用它们可以提高疗效，降低剂量，减少副作用，扩大有效药物的选择。公共卫生相关性：这项继续研究探讨了催乳素（一种由脑垂体和乳腺组织产生的激素）在体外和体内条件下对乳腺癌细胞产生化疗耐药性的机制。长期目标是建立fda批准的长效多巴胺激动剂作为抑制或PRL分泌的药物，从而提高化疗药物对乳腺癌患者的疗效。

DESCRIPTION (provided by applicant): Chemotherapy is the mainstay treatment for advanced breast cancer, but tumor resistance is a major obstacle that results in treatment failure. Resistance results from many causes, including drug efflux, inactivation, altered expression of pro/anti-apoptotic proteins or tumor suppressor genes, and increased DNA repair mechanisms. We present evidence that prolactin (PRL) serves as a survival factor which antagonizes the cytotoxicity of the DNA-damaging agents cisplatin and doxorubicin, and the microtubule disrupting agent taxol. PRL protects breast cancer cells (BCC) against drugs by activating the detoxification enzyme glutathione-S-transferase (GST) as well as by increasing the expression of the anti- apoptotic protein Bcl-2. The human breast receives PRL input from two sources: the pituitary and local. Within the breast, stromal adipocytes produce significantly more PRL than epithelial cells, and both are under tonic inhibition. We discovered expression of dopamine receptors (DAR) in breast tissue, adipocytes and BCC. Similar to their action on pituitary PRL, dopamine and bromocriptine (Br) suppress breast PRL production. Locally- produced PRL likely confers chemoresistance, since BCC with high endogenous PRL are more resistant to drugs than those with low PRL. Our newly developed LS14 human adipocyte cell line, which produces PRL and expresses the PRL receptor (PRL-R), is also resistant to many anticancer drugs. Hypothesis: PRL confers chemoresistance against different classes of anti-cancer drugs by activating detoxification enzymes, anti-apoptotic proteins or both. Input of PRL to breast tumors comes from the circulation (pituitary), paracrine (stromal adipocytes) and autocrine (BCC). Similar to its action on the pituitary, dopamine suppresses breast PRL and thus sensitizes breast cancer to anticancer drugs. Aim 1: To compare expression of PRL and PRL-R in BCC at both the mRNA and proteins levels, and use knockdown and overexpression to determine the role of local PRL in chemoresistance, Aim 2: To examine whether GST and/or Bcl-2 mediate chemoresistance by PRL against four classes of drugs: DNA-damaging, microtubule altering, anti-metabolites, and the death ligand TRAIL (tumor necrotic factor (TNF)-related apoptosis-inducing ligand). Aim 3: To characterize DAR in adipocytes, BCC and LS14 cells, and determine whether dopamine and its agonists suppress PRL production and increase cell sensitivity to anticancer drugs. Aim 4: To establish mixed-cultures of fully differentiated LS14 adipocytes and BCC and examine whether dopamine agonists sensitize LS14/BCC tumors in athymic mice to anticancer drugs. Clinical Impact: Oral dopamine agonists with an excellent record of safety and efficacy for suppressing PRL are FDA-approved. Their use in breast cancer patients undergoing chemotherapy should improve dru efficacy, lower the doses, reduce side effects and expand the choice of effective drugs. PUBLIC HEALTH RELEVANCE: This continuation study examines the mechanism by which prolactin, a hormone which is produced by both the pituitary gland and breast tissue, confers chemoresistance on breast cancer cells under in vitro and in vivo conditions. The long term goal is to establish FDA-approved, long acting dopamine agonists as suppressor or PRL secretion, resulting in increased efficacy of chemotherapeutic agents in breast cancer patients.