Chromosomal alterations and mutagen sensitivity in human mucosal cells of the oropharynx and lymphocytes caused by BPDE

Abstract

Background: In addition to exogenous risk factors, the development of head and neck cancer is based on genetic alterations and individual mutagen sensitivity. DNA damage caused by xenobiotics is not uniformly distributed over the DNA, as certain chromosomes and genes are more likely to be damaged than others. The DNA damaging effect of xenobiotics and the specific sites of chromosomal changes require further investigation.

Materials and methods: In order to evaluate mutagen sensitivity in macroscopically healthy mucosal tissue of 30 patients with (15) and without cancer (15) of the oropharynx, three different chromosomes (chromosomes 3, 5 and 8) involved in carcinogenesis of the oropharynx and one control chromosome (chromosome 1) were examined. After incubation with benz[a]pyren-7,8-diol-9,10-epoxide (BPDE), a tobacco-associated carcinogen, comet fluorescence in situ hybridization (FISH) was applied to assess DNA damage of these chromosomes. Furthermore, lymphocytes and macroscopically healthy mucosal cells of the oropharynx were assessed using FISH after their incubation with BPDE in order to evaluate loss and gain of DNA in these chromosomes.

Results: BPDE caused significant DNA damage compared to the negative control in oropharyngeal mucosa cells of patients with and without carcinoma. No difference was observed between mutagen sensitivity of patients suffering from cancer of the oropharynx and patients without malignancy. In cells from patients suffering from squamous cell carcinoma, significantly higher DNA damage was found in chromosome 5 and 8 after incubation with BPDE and application of comet FISH. No difference was found in patients without cancer of the head and neck. After application of FISH, no difference in the amount of DNA was found in chromosomes 1, 3, 5 and 8, neither in lymphocytes nor in mucosal cells from both groups. No DNA gain or loss was detected.

Conclusion: Our results confirm the higher sensitivity of chromosomes 5 and 8 of normal epithelial cells of oropharyngeal cancer patients to BPDE. These effects were shown in macroscopically healthy tissue of such patients for the first time. Therefore, we suggest that these are early onset effects in carcinogenesis of the head and neck. No such effect was shown for chromosome 3 and control chromosome 1.