Nuclear texture parameters as discriminant factors in cell cycle and drug sensitivity studies

Abstract

The authors have recently shown that cell cycle characteristics of in situ cell populations can be determined using the SAMBA 200 cell image processor by computing 15 densitometric and texture parameters on each Feulgen-stained nucleus and multiparametric analysis of data. The present paper displays the importance of chromatin pattern assessment and detection of conformational changes in DNA structure, based on nine nuclear texture parameters measured from the grey level cooccurrence and the run-length section matrices. Reference files were constructed by merging respective reference files (G0/G1, S, G2 and M) of MDA AG and MCF-7, two mammary epithelial cell lines presenting different morphological aspects and hormone responses, these files were found to be valid in the reclassification of any mammary epithelial cell in culture with a diploid or near diploid pattern. Moreover, the authors demonstrate that chromatin texture changes, following direct interaction of chemotherapeutic drugs with DNA, may be assessed owing to nuclear texture parameters. Consecutive to daunomycin addition (0.5 microgram/ml) and concomitant to the appearance of nuclear morphological alterations in MDA AG sensitive cells as viewed by microscopic observation, discriminant factorial analysis showed progressively increasing erroneous reclassification from 15 to 72 h of treatment. These experimental results were exploited with a kinetic mathematical model to quantify the daunomycin blocking effect: 20% in S phase and 80% in G2 phase. Interestingly, no textural change was observed on MDA A1 anthracycline resistant cells, indicating that these texture parameters may permit distinction of drug sensitive cells. This methodology 1) can be applied to test in vitro resistance-reversal molecules, 2) may be extended to other therapeutic agents giving rise to conformational changes in DNA structure, and 3) can be applied to cytopunctions or imprints of tumor biopsies with diploid-like DNA content to follow evolution of drug sensitivity or resistance during course of therapy.