Ultrastructural morphology and localisation of cisplatin-induced platinum-DNA adducts in a cisplatin-sensitive and -resistant human small cell lung cancer cell line using electron microscopy

Ultrastructural morphology (transmission electron microscopy) and localisat ion of cisplatin-induced platinum (Pt)-DNA adducts (immunoelectron microsco py) were analysed in the human small cell lung cancer cell line GLC(4) and its 40-fold in vitro acquired cisplatin-resistant subline GLC(4)-CDDP, whic h is characterised by among other things, a decreased DNA platination. Immu nolabelling of Pt-DNA adducts was performed with the polyclonal antibody GP t,known to detect the main Pt-containing intrastrand and interstrand DNA ad ducts, Morphological analysis of GLC(4) and GLC(4)-CDDP at the ultrastructu ral level showed cells with a high nucleus/cytoplasm ratio with the majorit y of nuclei containing one or more nucleoli. GLC(4)-CDDP showed, in contras t to GLC(4), an extensive Golgi apparatus and an increased number of mitoch ondria DNA platination was detectable in both GLC(4) and GLC(4)-CDDP. Immun oelectron microscopy showed Pt-DNA adducts primarily in the nucleus, prefer entially at loci with high-density chromatin (e.g. heterochromatin, pars gr anulosa around nucleoli, condensed DNA in proliferating and apoptotic cells ), and in mitochondria. The level of detectable Pt-DNA adducts was cell cyc le status-dependent. In both cell lines, Pt-DNA adduct levels increased fro m non-dividing interphase cells to dividing cells and were highest in cells undergoing apoptosis. Overall localisation of Pt-DNA adducts was comparabl e in GLC(4) and GLC(4)-CDDP cells. (C) 2001 Elsevier Science Inc. All right s reserved.