Quantification of changes in c-myc mRNA levels in normal human bronchial epithelial (NHBE) and lung adenocarcinoma (A549) cells following chemical treatment.
Lung tumors frequently exhibit altered expression of oncogenes and/or tumor suppressor genes. Although some of these alterations are believed to arise from chemical exposure, the ability of specific chemicals to cause distinct changes in gene expression is not well characterized. We previously reported the development of a quantitative reverse transcriptase/polymerase chain reaction (RT/PCR) method for measuring c-myc mRNA levels, and reported that c-myc proto-oncogene expression is significantly increased in small-cell lung carcinoma cells. In the present study, quantitative RT/PCR was used to assess the effect of model toxins cycloheximide (CHX), a protein synthesis inhibitor, and N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), a DNA alkylating agent, on c-myc mRNA levels in normal human bronchial epithelial (NHBE) and lung adenocarcinoma (A549) cells. Expression of c-myc was evaluated at 1-100 microM CHX and MNNG and was compared to the cytotoxic response as measured by the neutral red assay. Cycloheximide elicited a dose-dependent increase in c-myc mRNA levels in NHBE and A549 cells, but did not alter expression of the housekeeping gene beta-actin. A maximum increase for c-myc expression (200% of control) was observed 5 h after treatment with noncytotoxic concentrations. In contrast, MNNG elicited a dose-dependent decrease in c-myc expression in A549 cells, but no significant change in c-myc was observed in NHBE cells. The results from this study suggest that the quantitative RT/PCR method may be an appropriate technique for monitoring gene expression changes following chemical exposure. Hence, these types of studies may assist in the identification of specific chemicals which may induce the genetic alterations involved in the development of lung cancer as well as provide information relevant to the interactive effects of chemicals within complex mixtures.
Fields
W R
WR
Integrated Toxicology Program, Duke University Medical Center, Durham, North Carolina 27710, USA. fieldsw@rjrt.com
Desiderio
J G
JG
Putnam
K P
KP
Bombick
D W
DW
Doolittle
D J
DJ
D000199:Actins / Q000235:genetics / Q000378:metabolism; D000230:Adenocarcinoma; D000328:Adult; D001980:Bronchi / Q000187:drug effects* / Q000378:metabolism; D002273:Carcinogens / Q000633:toxicity; D002648:Child; D003513:Cycloheximide / Q000633:toxicity*; D004305:Dose-Response Relationship, Drug; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D016259:Genes, myc; D006801:Humans; D008175:Lung Neoplasms; D008297:Male; D008769:Methylnitronitrosoguanidine / Q000633:toxicity*; D000090063:Proto-Oncogene Mas; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000187:drug effects* / Q000378:metabolism; D020545:Respiratory Mucosa / Q000187:drug effects* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000378:metabolism
D000199:Actins; D002273:Carcinogens; C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas; D016271:Proto-Oncogene Proteins c-myc; D012333:RNA, Messenger; D008769:Methylnitronitrosoguanidine; D003513:Cycloheximide