In order to study differences in the tumor growth and frequency of metastases between younger and older patients with lung cancer, we investigated the nuclear DNA and nuclear protein according to age by means of cytophotometry after combined staining with Feulgen and Naphthol Yellow S. On the basis of Feulgen-Naphthol Yellow S staining method, 13 patients less than 40 years old and 16 patients older than 70 years were investigated. Our results showed no significant difference in nuclear DNA contents between young and old patients, but there were significantly higher nuclear protein contents (p<0.05) and nuclear protein to nuclear DNA (NP/DNA) ratios (p<0.001) in young patients than in old patients. This suggests that young patients may have higher tumor proliferation (high nuclear protein contents and NP/DNA ratios). The lower nuclear protein content and NP/DNA ratio of older cases is in keeping with the general phenomenon of slower tumor growth and less frequent metastases in such cases.
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