COMPARISON OF C-MYC EXPRESSION IN NORMAL HUMAN BRONCHIAL EPITHELIAL CELLS AND LUNG CANCER CELL LINES USING A QUANTITATIVE FLUORESCENCE-BASED REVERSE TRANSCRIPTASE-POLYMERASE CHAIN REACTION METHOD

Abstract

Mutations, either heritable or induced,can modulate the expression of oncogenes and/or tumor suppressor genes and thereby alter the biology of the affected cells. Over expression of the c-myc oncogene appears to contribute to the development of small cell lung cancer, and has been used as an indicator of poor prognosis for this tumor type. However, neither the variability of c-myc expression in noncancerous human lung tissue retrieved from different donors nor the level of c-myc expression in various lung tumor types has been adequately studied. The authors havequantified and compared the expression of c-myc in normal human bronchial epithelial (NHBE)cells from several noncancerous lungs and in transformed human lung cell lines. c-myc mRNA levels were determined through the annealing of a gene-specific probe to a target cDNA copy of the mRNA. The fluorescence signal liberated by the 5-3 exonuclease-induced release of the reporter dyefrom theannealed probeduring the extension cycle of polymerasechain reaction (PCR) was quantified spectrophotometrically. While NHBE cells from four donors expressed comparable levels of c-myc mRNA, the c-myc mRNA levels in large cell lung carcinoma (LCLC) and small cell lung carcinoma (SCLC) cell lines were 2.4- and 5.0-fold greater than in NHBE cells, respectively. In contrast, the lung adenocarcinoma and adenosquamous carcinoma cell lines examined did not exhibit an increase in c-myc expression relative to the NHBE cells. In summary, this reverse/transcriptase polymerasechain reaction method readily quantifies and distinguishes the level of c-myc mRNA in NHBE and human lung cancer cells. This technology may serve to characterize oncogene-related changes during tumorigenesis, to identify genetically predisposed individuals, and to allow for earlier diagnosis and treatment of lung cancer.