Yang Wentao, Klos Kristine S, Zhou Xiaoyan, Yao Jun, Yang Ying, Smith Terry L, Shi Daren, Yu Dihua
Cancer. 2003 Sep 15;98(6):1123-30. doi: 10.1002/cncr.11625.
Clinical investigations have shown that in patients with breast carcinoma, tumors that overexpress the erb-B2 gene are less responsive to certain chemotherapy regimens compared with tumors that express low levels of ErbB2, suggesting that ErbB2 overexpression may be used as a marker for poor response to chemotherapy in patients with breast carcinoma. The combination of cyclophosphamide, methotrexate, and 5-fluorouracil (CMF) is one of the most widely used chemotherapy regimens in patients with breast carcinoma. Patients who have ErbB2-overexpressing breast carcinomas have poorer responses to CMF compared with patients who have breast carcinomas with low ErbB2 expression. ErbB2-overexpressing breast tumor cells are resistant to taxol-induced apoptotic cell death. The underlying molecular mechanism is that ErbB2 inhibits p34(Cdc2) activation, which is required for taxol-induced apoptosis, by up-regulating p21(Cip1) and by hyperphosphorylating p34(Cdc2) on tyrosine-15. However, the relation between ErbB2, p21(Cip1), and p34(Cdc2) in patients with breast carcinoma remains elusive. The contribution of these molecular alterations to ErbB2-mediated CMF resistance has not been examined.
Formalin-fixed, paraffin-embedded, 5 microm thick tissue sections from 107 patients with invasive breast carcinoma were immunostained using specific antibodies against ErbB2, p21(Cip1), and phosphorylated tyrosine (Tyr)-15 of p34(Cdc2). Ninety-four of 107 patients were treated with the CMF regimen. In situ hybridization of p21(Cip1)mRNA also was performed in 20 of the sections described above. ErbB2 expression levels, p21(Cip1) expression levels, and phosphorylation status on Tyr15 of p34(Cdc2) were analyzed for correlations with clinicopathologic parameters for the 107 patients and for correlations with disease-free survival (DFS) in the 94 patients who were treated with the CMF regimen.
Among 94 patients with breast carcinoma who were treated with CMF, it was found that ErbB2 overexpression was associated significantly with poor DFS (P < 0.01). Patients who had higher p21(Cip1) expression had worse DFS compared with patients who had low p21(Cip1) expression (P = 0.02). However, no significant correlation was found between p34(Cdc2)-Tyr15 phosphorylation and DFS (P > 0.05). It is noteworthy that p21(Cip1) expression and p34(Cdc2)-Tyr15 phosphorylation were correlated significantly and positively with ErbB2 expression (P < 0.01).
The current study suggests that p21(Cip1) expression, but not p34(Cdc2)-Tyr15 phosphorylation, may play a role in ErbB2-mediated CMF resistance, which may contribute to the poor survival of patients with ErbB2-overexpressing breast carcinomas who were treated on the CMF regimen. In addition, ErbB2 overexpression was correlated with p21(Cip1) up-regulation and with increased p34(Cdc2)-Tyr15 phosphorylation in breast tumors.
临床研究表明，在乳腺癌患者中，与低表达ErbB2的肿瘤相比，过表达erb - B2基因的肿瘤对某些化疗方案的反应较差，这表明ErbB2过表达可能用作乳腺癌患者化疗反应不佳的标志物。环磷酰胺、甲氨蝶呤和5 - 氟尿嘧啶（CMF）联合化疗是乳腺癌患者中最广泛使用的化疗方案之一。与低表达ErbB2的乳腺癌患者相比，过表达ErbB2的乳腺癌患者对CMF方案的反应较差。过表达ErbB2的乳腺肿瘤细胞对紫杉醇诱导的凋亡性细胞死亡具有抗性。潜在的分子机制是，ErbB2通过上调p21（Cip1）并使p34（Cdc2）的酪氨酸 - 15位点过度磷酸化，从而抑制紫杉醇诱导的凋亡所必需的p34（Cdc2）激活。然而，乳腺癌患者中ErbB2、p21（Cip1）和p34（Cdc2）之间的关系仍不清楚。这些分子改变对ErbB2介导的CMF耐药性的作用尚未得到研究。
使用针对ErbB2、p21（Cip1）和p34（Cdc2）磷酸化酪氨酸（Tyr） - 15的特异性抗体，对107例浸润性乳腺癌患者的福尔马林固定、石蜡包埋、5微米厚的组织切片进行免疫染色。107例患者中有94例接受了CMF方案治疗。还对上述20个切片进行了p21（Cip1）mRNA的原位杂交。分析了107例患者的ErbB2表达水平、p21（Cip1）表达水平以及p34（Cdc2）Tyr15位点的磷酸化状态与临床病理参数的相关性，以及94例接受CMF方案治疗患者的无病生存期（DFS）的相关性。
在94例接受CMF治疗的乳腺癌患者中，发现ErbB2过表达与较差的DFS显著相关（P < 0.01）。与低表达p21（Cip1）的患者相比，高表达p21（Cip1）的患者DFS更差（P = 0.02）。然而，未发现p34（Cdc2） - Tyr15磷酸化与DFS之间存在显著相关性（P > 0.05）。值得注意的是，p21（Cip1）表达和p34（Cdc2） - Tyr15磷酸化与ErbB2表达显著正相关（P < 0.01）。
当前研究表明，p21（Cip1）表达而非p34（Cdc2） - Tyr15磷酸化可能在ErbB2介导的CMF耐药中起作用，这可能导致接受CMF方案治疗的过表达ErbB2的乳腺癌患者生存率较低。此外，乳腺癌中ErbB2过表达与p21（Cip1）上调以及p34（Cdc2） - Tyr15磷酸化增加相关。
