OBJECTIVETo explore the expression of PI3K in esophageal squamous cell carcinoma (ESCC) and its clinical significance.

METHODSThe expression of PI3K proteins was detected by immunohistochemical SP staining in 91 ESCC tissues and normal mucosa of 10 cases. RT-PCR was used to detect the expression of PI3K mRNA in 30 ESCC tissues and adjacent normal mucosa. The relation between PI3K expression and the clinicopathological features and prognosis was analyzed.

RESULTSThe positive rate of expression of PI3K protein in ESCC was 86.8%, significantly higher than that in normal esophageal mucosa (10.0%, P<0.001). There was a positive correlation between P13K expression and the degrees of differentiation, invasion depth, and clinical stage. No positive correlation was found between the expression of PI3K protein and age, gender and lymph node metastasis (P>0.05). The poorer is the differentiation of ESCC, the stronger is expression of PI3K protein (r = 0.351, P<0.05); the deeper is the invasion depth of ESCC, the stronger is expression of PI3K protein (r = 0.210, P<0.05); and the higher is the clinical stage of ESCC, the stronger expression of PI3 K protein (r = 0.240, P<0.05). RT-PCR results demonstrated that the level of PI3K mRNA expression in ESCC was 0.675 +/- 0.029, significantly higher than that in the adjacent normal mucosa (0.349 +/- 0.073, P<0.05). The high expression of PI3K mRNA was correlated with poor differentiation, deep invasion and clinical stage of ESCC (P<0.05). The result was consistent with SP staining immunohistochemistry. By Kaplan-Meier analyses, following factors were observed to be significantly associated with prognosis: PI3K expression, the degrees of differentiation, invasion depth, lymph node metastasis, clinical stage, tumor embolus and stump invaded (all P<0.05). The multivariate analysis showed that clinical stage (P<0.05), invasion depth (P<0.05) and stump invaded (P<0.05) were significantly correlated with the prognosis. The multivariate analysis of Cox model showed that PI3K was not an independent prognostic indicator of prognosis (chi2 = 1.235, P = 0.266).

CONCLUSIONSThe expression levels of PI3K protein and mRNA in ESCC tissues are significantly increased and PI3K plays a role in the carcinogenesis and development of ESCC. The enhanced PI3K expression may serve as a reference index indicating a poor prognosis in ESCC.