BACKGROUNDTo study the expression and mutation of β-catenin in non-small cell lung cancer (NSCLC) and the relationships between expression, mutation and clinicopathological parameters and prognosis.

METHODSAll the 120 samples (fixed with 10% formalin and embedded in paraffin blocks) were obtained from patients with NSCLC, who underwent surgery in the First Affiliated Hospital of China Medical University from 2001 to 2002 and Anshan Tumor Hospital from 1980 to 2001. Follow-up was available in 67 patients. The 53 fresh NSCLC samples and corresponding normal lung tissues were obtained from the First Affiliated Hospital of China Medical University. The pattern of β-catenin protein expression was detected by immunohistochemistry method (120 samples) using anti-β-catenin antibody (1:600). The level of β-catenin protein expression was detected by Western Blotting method using anti-β-catenin antibody (1:1500) in 53 fresh NSCLC samples and corresponding normal lung tissues. The mutation of β-catenin gene exon 3 was detected by polymerase chain reaction (PCR) and direct sequencing method (53 samples).

RESULTSIn 120 patients, abnormal expression rate of β-catenin was 80% (96/120) and nuclear expression rate was 36.7% (44/120). There was significant difference in β-catenin expression between well differentiated and poorly differentiated NSCLC. In well and moderately differentiated NSCLC cells the abnormal expression rate was 69.2% (45/65), which was much lower than 92.7% (51/55) of poorly differentiated ones (P=0.003). β-catenin expressed abnormally in 86.5% (64/74) cases with lymph node metastasis and in 69.6% (32/46) cases without lymph node metastasis (P=0.044). The results of Western Blotting showed that the expression of β-catenin in NSCLC tissues was significantly higher than that in normal lung tissues (t=2.935, P=0.005). The 53 patients' DNA were analysed by PCR and direct sequencing method, but no mutation in β-catenin gene exon 3 was found.

CONCLUSIONSAbnormal expression of β-catenin is negatively associated with differentiation and positively associated with lymph node metastasis of NSCLC. The β-catenin gene exon 3 mutation is not the main reason of β-catenin abnormal expression in NSCLC.