HUMAN LUNG-CARCINOMA CELL-LINE DLKP CONTAINS 3 DISTINCT SUBPOPULATIONS WITH DIFFERENT GROWTH AND ATTACHMENT PROPERTIES

Many human solid tumours, particularly lung tumours, contain different subpopulations. the presence of which can complicate diagnosis and tr eatment, yet few models exist for in vitro studies. We have found that DLKP, a human lung cell line established from a tumour histologically diagnosed as a 'poorly differentiated squamous carcinoma', contains 3 morphologically distinct populations. Three clones corresponding to t hese populations were established from the parental DLKP cells. Confir mation that the clones were derived from the parental population was o btained by DNA fingerprinting. The clones were designated M (mesenchym allike), I (intermediate) and SQ (squamous), On prolonged subculture, SQ and M can each interconvert with I, but SQ and M do not interconver t. We investigated the growth patterns of these isolated populations i n monolayer culture, soft agar, spinner flasks and serum-free medium, In all but the latter assay, the parental DLKP cells grew faster than each of the clones, indicating some form of physiological co-operation between the clones. The growth of the clones themselves varied under the different assay conditions (DLKP-I showing greatest growth in mono layer, in serum-containing and serum-free media but, surprisingly, bei ng unable to grow in soft agar, unlike the SQ and hi clones), Addition of fibronectin permitted growth of DLKP-M and DLKP-SQ in serum-free m edium at equivalent rates to those of DLKP and DLKP-I, In some cases, morphological adaptation to specific growth conditions was observed. V ariation between the clones was also evident in their respective chrom osome numbers (with the hi clone being predominantly hyperdiploid and the other clones predominantly hypertetraploid) and in their ability t o adhere to extracellular matrix proteins, with DLKP-M showing most ra pid attachment. Electrical resistance studies revealed the absence of tight junctions from the parental line and clonal subpopulations, Exte nsive immunohistological studies showed that neither DLKP nor the clon es express cytokeratin or any other epithelial marker examined, but ne uroendocrine markers were present. Further analysis of these different clonal populations may help to reveal some of the mechanisms involved in lung tumour development and progression.