乳腺癌组织中平滑肌22α的表达与淋巴结转移的关系

Expression of SM22α and its relationship with lymph node metastasis in breast cancer

目的 分析平滑肌（SM）22α在乳腺癌组织中的表达与淋巴结转移的关系,探讨SM22α参与乳腺癌淋巴结转移的分子机制.方法 应用逆转录-聚合酶链反应（RT-PCR）检测了27例乳腺癌组织及癌旁正常乳腺组织中SM22α表达水平 同时用Western印迹分析检测了12例乳腺纤维腺瘤组织、15例乳腺癌未转移组织、12例乳腺癌淋巴结转移组织中SM22α mRNA和蛋白表达水平 利用RT-PCR和明胶酶图检测乳腺纤维腺瘤、乳腺癌未转移、乳腺癌淋巴结转移组织中基质金属蛋白酶（MMP）2、MMP9表达和活性及组织金属蛋白酶抑制剂（TIMP）1表达水平.结果 RT-PCR检测结果显示,乳腺癌组织中SM22α mRNA表达水平（5.1%±2.4%）显著低于癌旁正常乳腺组织（30.1%±5.1%）（P＜0.01）,淋巴结转移组乳腺癌组织中SM22α表达水平（6.2%±3.1%）显著低于无淋巴结转移组（10.1%±4.1%）及乳腺纤维腺瘤组织（15.1%±5.3%）（均P＜0.01）.Western印迹分析结果表明,SM22α蛋白在无淋巴结转移组（14.5%±2.1%）及伴淋巴结转移组乳腺癌组织中（6.2%±3.1%）表达水平均显著低于乳腺纤维腺瘤组（26.8%±5.5%）（均P＜0.01）.MMP2、MMP9表达水平及活性均显著高于未转移组（P＜0.01）,乳腺癌组织中SM22α表达水平与MMP2（r=-0.848 n=27 P＜0.01）、MMP9（r=-0.916 n=27 P＜0.01）活性呈负相关.结论 SM22α在乳腺癌组织中表达下调与淋巴结转移有关,SM22α可能通过负性调节MMP2、MMP9表达抑制乳腺癌淋巴结转移.

Objective To analyze the relationship between the expression of SM22α and the lymph node （LN） metastasis of breast cancer and to investigate its molecular mechanisms. Methods Reverse transcription-polymerase chain reaction （RT-PCR） was performed to detect the expression of SM22α in breast cancer tissue and adjacent normal breast tissue. RT-PCR and Western blot were employed to investigate the SM22α mRNA and protein level in tissues of breast fibroadenoma, breast cancer without LN metastasis and breast cancer with LN metastasis. RT-PCR and zymography were used to detect the MMP2 and MMP9 expression and activity and TIMP1 expression level in breast fibroadenoma, breast cancer samples without LN metastasis and those with LN metastasis respectively. Results The expression level of SM22α mRNA in breast cancer was significantly lower than that in breast fibroadenoma or adjacent normal breast tissue （5.1% ±2.4% vs 15.1% ±5.3% vs 30.1% ±5.1%, P〈0.01）. The protein and mRNA expression level of SM22α in breast cancer samples with LN metastasis were significant lower than those of breast cancer without LN metastasis （6.2% ± 3.1% vs 10.1% ±4.1%, P 〈0.01 ）. Both the expression and activity of MMP2 and MMP9 in breast cancer samples with LN metastasis were significant higher than those without LN metastasis （P 〈 0.01 ）. A strong negative correlation was found between SM22α protein level and MMP2 activity （r= -0.848 n=27 P〈0.01） or MMP9 activity （r= -0.916 n=27 P〈0.01） in breast cancer tissue. Conclusion A down-regulation of SM22α in breast cancer is correlated with LN metastasis. SM22α may inhibit the LN metastasis through a negative regulation of MMP2 and MMP9 in breast cancer.