p53, BCL-2 and BAX in non-small cell lung cancer brain metastases: a comparison of real-time RT-PCR, ELISA and immunohistochemical techniques

Abstract

OBJECTIVES: Metastasis to the brain is a severe and common complication in non-small cell lung cancer (NSCLC). The examination of cell cycle associated genes in these lesions may contribute to the understanding of metastatic growths in the central nervous system. The aim of this study was to evaluate the p53, BCL-2 and BAX mRNA and protein expression in NSCLC brain metastases in comparison with matched primary tumors. METHODS: For quantitative TaqMan real-time reverse transcription-polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA), fresh frozen tumor specimens from 12 patients with NSCLC brain metastases were available. For immunohistochemical staining, 78 surgically removed NSCLC brain metastases were used. PCR results were analysed using the DeltaDeltaCT method. Staining was analysed using a modified immunoreactive score (IRS). RESULTS: Overall, p53, BCL-2 and BAX expression values in brain metastases and primary tumors showed a wide variety. The comparison of different techniques revealed different findings on the mRNA and protein level. Herein, PCR and ELISA revealed no clear tendencies. In contrast, immunohistochemistry showed significant overexpression of BAX and underexpression of BCL-2 in brain metastases. CONCLUSION: A high variability in the expression of p53, BCL-2 and BAX in NSCLC exists in brain metastases. Immunohistochemistry revealed overexpression of BAX and underexpression of BCL-2 in brain metastases, whereas there were no clear tendencies using PCR and ELISA techniques. More insights into the BAX/BCL-2 interaction are needed before reasonable conclusions can be drawn from the existing data.