Lin Valerie C L, Woon Chow Thai, Aw Swee Eng, Guo Chunhua
Department of Clinical Research, Singapore General Hospital, School of Biological Sciences, School, Singapore 637616.
Endocrinology. 2003 Dec;144(12):5650-7. doi: 10.1210/en.2003-0484. Epub 2003 Sep 11.
We have reported previously that reactivation of progesterone receptor (PR) expression in estrogen receptor (ER)- and PR-negative MDA-MB-231 breast cancer cells enabled progesterone to inhibit cell growth and invasiveness, and to induce remarkable focal adhesions. The present study addressed molecular mechanisms that mediate these anticancer effects of progesterone in the PR-transfected breast cancer cells ABC28. In response to progesterone treatment are the marked up-regulation of cyclin-dependent kinase inhibitor protein p21WAF1/CIP1 and decreased expression of cyclin A, cyclin B1, and cyclin D1 that are required for G1 progression and during cell mitosis. Progesterone also induced down-regulation of phosphorylated MAPK (p42/44 MAPK). Furthermore, this study also demonstrated that MEK inhibitor PD98059 that inhibits the phosphorylation of p42/44 MAPK also caused reduction of cyclin D1 level and inhibition of cell proliferation. These results suggest that inhibition of p42/44 MAPK pathway is part of the mechanisms mediating progesterone's growth-inhibitory effect. On the other hand, progesterone-induced focal adhesion is mediated by separate pathway. Whereas PD98059 exhibited no effects on cell adhesion, inhibitory antibody to beta1-integrin was able to reverse progesterone-induced focal adhesion and progesterone-induced increase in the phosphorylation of focal adhesion kinase. On the other hand, beta1-integrin antibody had no effect on progesterone-mediated growth inhibition and on progesterone-mediated expression of cyclins p21CIP1/WAF1 and phosphorylation of P42/P44 MAPK. In the context of complex functions of progesterone in breast cancer and reproductive organs, identification of distinct pathways offers new strategies for designing therapeutic agents to target the specific pathway so as to minimize the side effects.
我们之前报道过，在雌激素受体（ER）和孕激素受体（PR）均为阴性的MDA-MB-231乳腺癌细胞中重新激活孕激素受体（PR）的表达，可使孕激素抑制细胞生长和侵袭，并诱导显著的粘着斑形成。本研究探讨了在PR转染的乳腺癌细胞ABC28中介导孕激素这些抗癌作用的分子机制。对孕激素处理的反应是细胞周期蛋白依赖性激酶抑制蛋白p21WAF1/CIP1显著上调，而细胞周期蛋白A、细胞周期蛋白B1和细胞周期蛋白D1的表达降低，这些蛋白是G1期进展和细胞有丝分裂所必需的。孕激素还诱导磷酸化丝裂原活化蛋白激酶（p42/44 MAPK）下调。此外，本研究还表明，抑制p42/44 MAPK磷酸化的MEK抑制剂PD98059也会导致细胞周期蛋白D1水平降低和细胞增殖抑制。这些结果表明，抑制p42/44 MAPK信号通路是介导孕激素生长抑制作用机制的一部分。另一方面，孕激素诱导的粘着斑由独立的信号通路介导。虽然PD98059对细胞粘附无影响，但β1整合素抑制性抗体能够逆转孕激素诱导的粘着斑以及孕激素诱导的粘着斑激酶磷酸化增加。另一方面，β1整合素抗体对孕激素介导的生长抑制以及孕激素介导的细胞周期蛋白p21CIP1/WAF1表达和P42/P44 MAPK磷酸化无影响。鉴于孕激素在乳腺癌和生殖器官中的复杂功能，确定不同的信号通路为设计靶向特定信号通路的治疗药物提供了新策略，从而将副作用降至最低。
