THE ROLE OF EGF-RELATED PEPTIDES IN THE PATHOGENESIS OF BREAST AND COLON CANCER

转化生长因子α(TGF-α)、两性调节素(AR)、肝素结合生长因子(HB-EGF)、人参球蛋白(HRG)和CRIPTO-1(CR-1)是结构上和某些情况下与表皮生长因子(EGF)相关的蛋白质，它们与EGF受体(c-erb B)结合，而HRG与c-erb B-3或c-erb B-4结合。本研究表明，MCF-10A人乳腺上皮细胞对外源性EGF、HB-EGF、TGF-α或AR有丝分裂反应，c-Ha-ras原癌基因点突变后，内源性HB-EGF、TGF-α、AR和HRG表达增加，而erb B-2转化这些细胞仅上调AR和HRG表达。此外，人转化生长因子-α基因在这些细胞中的过表达导致了它们的体外转化。加入抗EGF受体阻断抗体可抑制MCF-10A转化的乳腺细胞的生长，这表明在这些细胞中存在一个外部自分泌环路。雌激素可促进雌激素敏感型人乳腺癌细胞系中转化生长因子-α和AR基因的表达。重组CR-1蛋白能够适度刺激小鼠和人乳腺上皮细胞的增殖，并抑制β-酪蛋白和乳清酸性蛋白的表达。此外，CR-1在体外和体内都能刺激小鼠乳腺上皮细胞的分枝形态发生，我们最近发现CR-1还可以通过caspase-3依赖的途径诱导乳腺上皮细胞亚群的凋亡。最后，CR-1可以通过基质或1型胶原涂层过滤器刺激小鼠乳腺上皮细胞的趋化和侵袭。CR-1不直接与EGF受体结合，也不直接激活c-erb B-2、c-erb B-3或c-erb B-4型受体酪氨酸激酶，无论是单独激活还是以各种异二聚体成对方式激活。然而，CR-1可以迅速和短暂地增强p46Shc的酪氨酸磷酸化，并激活MAPK亚型p42erk2。125125I-CR-1可以特异性地与130 kDa和60 kDa的蛋白发生交叉连接，这两种蛋白与其他erb B相关的酪氨酸激酶不同。虽然CR-1不能直接与已知的四种erb酪氨酸激酶受体中的任何一种结合，但它可以特异性地增强erb B-4的间接酪氨酸磷酸化。Erb B-4表达或活性的缺失显著削弱了CR-1激活MAPK的能力。AR和CR-1mRNA在大约50%到80%的原发和转移性人类结直肠肿瘤中表达，而在正常的邻近结肠或肝组织中只有5%表达这些基因。同样，在大约80%的原发人类乳腺肿瘤中检测到AR和CR-1的水平超过了邻近正常乳腺上皮的水平。-乳腺癌，Cripto，EGF，生长因子，转化生长因子，

Transforming growth factor alpha (TGF-alpha), amphiregulin (AR), heparin-binding growth factor (HB-EGF), heregulin (HRG) and cripto-1 (CR-1) are proteins that are structurally and in some cases functionally related to epidermal growth factor (EGF) in that TGF- alpha, HB-EGF and AR can bind to the EGF receptor (c-erb B) whereas HRG binds to c-erbB-3 or c-erb B-4. The present studies have demonstrated that MCF-10A human mammary epithelial cells are mitogenically responsive to exogenous EGF, HB-EGF, TGF-alpha or AR and that transformation of these cells with a point-mutated c-Ha-ras protooncogene results in an increase in the expression of endogenous HB-EGF, TGF-alpha, AR and HRG whereas erb B-2 transformation of these cells results in an upregulation in only AR and HRG expression. Furthermore, overexpression of a human TGF-alpha cDNA in these cells leads to their in vitro transformation. Addition of an anti-EGF receptor blocking antibody inhibits the growth of MCF-10A transformed mammary cells suggesting that an external autocrine loop is operative in these cells. Estrogens can increase the expression of TGF-alpha and AR mRNA and protein in estrogen-responsive human breast cancer cell lines. A recombinant CR-1 protein is able to moderately stimulate the proliferation of mouse and human mammary epithelial cells and to inhibit beta-casein and whey acidic protein expression. In addition, CR-1 can stimulate branching morphogenesis of mouse mammary epithelial cells in vitro and in vivo.We have recently found that CR-1 can also induce apoptosis in a subpopulation of mammary epithelial cells through a caspase-3-dependent pathway. Finally, CR-1 can stimulate chemotaxsis and the invasion of mouse mammary epithelial cells through matrigel or type-1 collagen-coated filters. CR-1 does not directly bind to the EGF receptor nor does it directly activate the c-erb B-2, c-erb B-3 or c- erb B-4 type 1 receptor tyrosine kinases either singularly or in various heterodimeric pairwise combinations. However, CR-1 can rapidly and transiently enhance the tyrosine phosphorylation of p46 Shc and can activate the MAPK isoform, p42erk2. 125125I-CR-1 can be specifically cross-linked to a 130 kDa and a 60 kDa protein that are distinct from other erb B-related tyrosine kinases. Although CR-1 fails to directly bind to any of the four known erb tyrosine kinase receptors, it can specifically enhance the indirect tyrosine phosphorylation of erb B-4. Abrogation of erb B-4 expression or activity significantly impairs the ability of CR-1 to activate MAPK. mRNA expression for AR and CR-1 have been detected in approximately 50% to 80% of primary and metastatic human colorectal tumors, whereas only 5% of normal adjacent colon or liver tissue express these genes. Likewise,AR and CR-1 were detected in approximately 80% of primary human breast tumors at a level that exceeded the level found in adjacent normal normal mammary epithelium. - breast cancer, Cripto, EGF, growth factors, TGF,