Expression and significance of HSP70 and PI3K pathway in hepatocellular carcinoma

Abstract

Objective To investigate the expression and clinical significance of heat shock protein (HSP) 70, phosphatidylinositol 3-kinase (PI3k) and protein kinase(Akt) in hepatocellular carcinoma(HCC). Methods A total of 98 patients diagnosed hepatocellular carcinoma pathologically were involved in this retrospective study. The patients underwent surgical resection at Shengjing Affiliated Hospital of China Medical University from March 2005 to December 2008. Local ethical committee approval was received and that the informed consent of all participating subjects was obtained. There were 69 males and 29 females with the age range of 31-70 years old and a median age of 57. Immunohistochemistry and Western blot were used to examine the expression and the level of HSP70, PI3K and Akt proteins respectively. Real-time reverse transcription polymerase chain reaction was used to examine the expression of HSP70, PI3K and Akt mRNA. The expression of HSP70, PI3k and Akt protein and mRNA was observed and the relationship between the gender, age, histological differentiation, lymph node metastasis, tumor-node-metastasis (TNM) staging were analyzed and compared by χ2 test and Fisher definite probability. The differences of HSP70, PI3K, Akt protein and mRNA content in HCC tissues of diverse differentiation were compared by one-way ANOVA analysis and LSD-t test and the correlation between them were analyzed using Pearson correlation analysis. Kaplan-Meier method and Log-rank test were used for survival analysis. Results Twenty-six(27%) cases presented HSP70 positive expression of grade 1, 41(42%) grade 2, and 31(32%) grade 3. The low expression of PI3K and Akt were observed in 40 (41%) and 42(43%) cases, and high expression in 58(59%) and 56 cases (57%) respectively. The expression of HSP70, PI3K, Akt protein were associated with HCC histological differentiation (χ2=49.99, 24.675, 32.521, all in P 0.05) . The HSP70 protein levels of well, moderate, poorly differentiated HCC were 0.5284±0.0056, 0.8420±0.0260, 0.9810±0.0020; the PI3K protein content were 0.6047±0.0558, 0.7027±0.0064, 0.9311±0.0019; and the Akt protein levels were 0.7139±0.0028, 0.7756±0.0039, 0.9701±0.0010. There were significant differences between the three groups (F=75.546, 76.007, 69.693; all in P<0.05); The levels of HSP70, PI3K and of Akt protein expression in poorly differentiated HCC tissues were significantly higher than those in well differentiated HCC tissues (t=12.256, 11.560, 10.532; all in P<0.05); The HSP70, PI3K and Akt protein contents were associated with differentiation of HCC(r= 0.387, 0.715, 0.713; P<0.01); When the mRNA relative expression amount of HSP70, PI3K and Akt protein in well differentiated HCC was set as 1, the mRNA expression levels of HSP70 in moderate and poorly differentiated HCC were 1.674±0.008, 2.234±0.006, the PI3K were 2.676±0.006, 3.449±0.045, and the Akt were 2.754±0.004, 3.366±0.006 respectively. There were significant differences among the three groups(F=9.784, 16.580, 5.933; P<0.05). The HSP70, PI3K and of Akt mRNA expression amount in poorly differentiated HCC tissues were significantly higher than that in well differentiated ones (t=0.126, 0.8202, 6.497; P<0.05); The expression of HSP70, PI3K and Akt mRNA were associated with the differentiation grades of HCC (r=0.210, 0.187, 0.397; P=0.001, <0.01, <0.05); Expression of HSP70 was positively associated with the expression of PI3K and Akt protein (r=0.715, 0.713; all in P=0.001); The average tumour-free survival time of patients with HSP70 positive expression at grade 1, 2 and 3 were 31, 17 and 11 months respectively, which showed significant difference among 3 groups(P=0.001); The average tumour-free survival time of patients with high and low PI3K expression were 12 and 25 months, which showed significant difference between 2 groups(P=0.001); The average tumour-free survival time of patients with high and low Akt expression were 11 and 21 months, which also showed significant difference between the 2 groups(P=0.001). Conclusions The different expression of HSP70, PI3K, Akt and mRNA in HCC tissues are associated with histological differentiation. HSP70 and PI3K/AKT signaling pathway may have a synergistic role in promoting HCC cell proliferation. The expression of HSP70, PI3K and Akt protein in HCC tissues are important prognostic factors of patients’ tumor-free survival. The higher the HSP70 protein expression is, the worse prognosis the patients have. Key words: Carcinoma, hepatocellular; Heat shock protein; Phosphatidylinositol 3-kinase; Protein kinase; Prognosis