蛋白激酶B在胃癌中的表达及其生物学意义

Study on expression of protein kinase B in gastric cancer and its possible implications

目的研究丝氨酸/苏氨酸蛋白激酶(Akt)在胃癌中的表达、活化情况及其与血管内皮生长因子C(VEGFC)的关系,以初探Akt表达和活化的生物学意义及其可能的机制。方法采用RTPCR法检测20例新鲜胃癌及癌旁正常组织标本中Akt1、Akt2和Akt3mRNA的表达;Western印迹法检测Akt和磷酸化Akt(pAkt)蛋白的表达;免疫组化检测pAkt蛋白和VEGFC在55例胃癌配对组织中的原位表达。结果20例胃癌及相应癌旁正常组织中Akt1、2、3mRNA的表达阳性率皆为100%,且三者在癌和正常组织中的表达水平差异无统计学意义(P>0.05)。Western印迹显示Akt蛋白在胃癌组织中的表达水平为正常组织的2.7倍(P<0.001),而pAkt蛋白的表达水平为癌旁正常组织的4.1倍(P<0.01)。免疫组化分析表明,pAkt表达于67.3%(37/55)的胃癌组织,且较高表达于组织分化较差(χ2=9.751,P<0.01)和TNM分期较晚(χ2=7.684,P<0.05)者;VEGFC在胃癌组织中的表达阳性率为61.8%(34/55),其表达与肿瘤的TNM分期(χ2=9.298,P<0.01)及淋巴结转移(χ2=7.605,P<0.05)密切相关,统计分析表明,pAkt与VEGFC的表达呈显著性正相关(Pearsonr=0.524,P<0.05,Spearman,rho=0.747,P<0.01)。结论Akt及pAkt蛋白特异性过表达于胃癌组织,可能是蛋白翻译水平和(或)代谢水平改变的结果。Akt蛋白的磷酸化可能促进胃癌细胞的恶性转化和淋巴结转移,VEGFC可能在其中发挥重要的介导作用。

Objective To determine the expression of Akt and its activation in gastric cancer, and to investigate the association of Akt with vascular endothelial growth factor C （VEGF-C）. Methods RT-PCR was used to detect the transcriptase of Akt1, Akt2 and Akt3, and Western blot was conducted to evaluate Akt and phosphorylated Akt （pAkt） proteins in 20 pairs of fresh gastric cancer tissue and normal tissues, pAkt and VEGF C proteins were detected in 55 paired gastric cancer tissues by immunohistochemistry. Results Akt1, Akt2 and Akt3 mRNA were constitutively expressed in gastric specimens and their levels in cancers were not significantly different with those in matched normal tissues （P〉 0.05）. The expression levels of Akt and pAkt proteins in cancerous tissues were 2.7-fold （P〈0. 001） and 4.1-fold （P〈0.01） higher than those in normal tissues respectively. The pAkt was found expressed in 67.3%（37/55） gastric cancers, and the abundance of pAkt was significantly associated with poorly differentiated phenotype （X^2 =9. 751, P〈0.01） and late TNM stage （X^2= 7. 684, P〈0.05）, while the expression of VEGF-C protein was also found to be related with TNM stage（X^2=9. 298, P〈0.01 ）and lymph node metastasis（X^2=7. 605,P 〈0.05） with a positive rate of 61.8% （34/55）in gastric cancer. In addition, pAkt abundance was significantly correlated with VEGF-C immunostaining （Pearson r=0. 524, P〈0. 05, Spearman rho=0. 747, P〈0.01）. Conclusions Overexpression of Akt and pAkt proteins is tumor speciflc,and may be a result of alterations of the gene translation and （or） protein metabolism. Akt phosphorylation might contribute to malignant transformation and enhanced aggressiveness of gastric cancer through VEGF-C up-regulation.