Measurement of DNA content and nuclear pleomorphism in metastatic variants of the B16 murine melanoma and hamster lymphoma and its liver metastasis using image analysis techniques

The DNA content and nuclear pleomorphism (NPM), which are two cellular features consistently employed in the assessment of tumour malignancy, have been measured in B16 murine melanoma metastatic variants and in hamster primary lymphoma and its liver metastasis as tumour models using image analysis techniques. The three melanoma variants studied were the low metastasis variant Fl, the BL6 variant selected for high lung metastasis and invasive ability, and ML8, a line isolated from pulmonary metastasis of the BL6 tumour. The cellularity of the melanomas bore no relationship to metastatic ability. The cell cycle distribution of nuclei based on integrated nuclear density (IND) was studied. The ML8 tumour showed higher DNA ploidy. Also, in this tumour the S-phase fraction was 2·0-fold larger than that of the BL6 tumour. Flow cytometry of nuclei isolated from paraffin-embedded tumour tissue showed all three melanomas were aneuploid. In both F1 and BL6, two distinct subpopulations (p² and p³) of nuclei, based on the degree of their pleomorphism, could be discerned. A significantly higher proportion of the more pleomorphic subpopulation (p²) occurred in BL6 than in Fl. In the ML8 alone, a third subpopulation (p¹), which was more pleomorphic than p², was found. The hamster lymphomas (HALY—malignant and N-HALY—non-malignant) were less cellular than the metastatic tumour (HALY-met) in liver. The lymphomas N-HALY and HALY-met had a higher DNA ploidy as compared with its primary tumour HALY. However, the non-malignant lymphoma N-HALY and the moderately malignant hamster fibrosarcoma were also found to be hyperdiploid. The metastatic lymphoma (HALY-met) showed a more pleomorphic nuclear subpopulation as compared with the primary. No differences were found in the size of the S-phase fractions of the hamster tumours. The present work shows that image analysis techniques enable one to make objective measurements of DNA content and nuclear pleomorphism of tumour cells, and suggests that in the tumour models investigated there is increased nuclear pleomorphism and DNA ploidy associated with tumour progression.[/p]