Point mutations in normal lungs of smokers and non-smokers

It is a widely-held hypothesis that environmental mutagens play an essential role in human somatic and germinal cell mutagenesis. In particular, the finding of small amounts of chemical mutagens in cigarette smoke has led to the general hypothesis that mutagens in cigarette smoke induce oncomutations and thus account for the carcinogenic effect of cigarette smoking in human lungs. However, this hypothesis has not been tested by an assay of nuclear point mutations in lungs of smokers and nonsmokers. Mismatch amplification mutation assay (MAMA), an effective form of allele-specific PCR, was applied for detection of point mutations in TP53 bp742, bp746 and bp747, K-ras bp35 and HPRT bp508 from a total of 291 tracheal-bronchial epithelial sectors from six smokers and nine non-smokers, yielding 949 individual mutational assays. The conditions of MAMA for each target point mutations were optimized such that the sensitivity of each was equal to or below 10⁻⁵. Lung epithelial sectors of 2.3x10⁶ cells in average contained 0-200 mutant cells in general, equivalent to mutant fractions (MFs) of 0-10⁻⁴ with an exception of rare sectors with MF larger than 4x 10⁻⁴ (4.6%). Noticeably, the distributions of the MFs among sectors did not vary appreciably with the donor's smoking status. The mean MFs per lung were very similar between smokers and non-smokers for all five target mutations assayed (p >> 0.05). The mean MFs were slightly higher in females than males (p = 0.015). The mean MFs increased with age of the subjects although the correlation did not reach statistical significance due to large variances within the same age group. The distributions of MF among sectors of smokers and non-smokers did not differ significantly by Kolmogorov-Smirnov test

Department dc:contributor.department

Massachusetts Institute of Technology. Biological Engineering Division.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2004

Author dc:creator

• Sudo, Hiroko, 1977-

Advisor dc:contributor.advisor

• William G. Thilly.

• Biological Engineering Division.

Statement dc:rights

• MIT theses are protected by copyright. They may be viewed, downloaded, or printed from this source but further reproduction or distribution in any format is prohibited without written permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/36321

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/36321