Effects of all-trans-retinoic acid incorporated into low-density lipoprotein on invasive properties of multidrug-resistant MCF-7 spheroids.

Cultured cells grown as spheroids provide an in vitro model that is closer to an in vivo tumour than conventional monolayer techniques. Previous work from our laboratory has demonstrated that spheroids formed from multidrug-resistant MCF-7 cells exhibit invasive characteristics which were not present in their sensitive counterparts. The treatment of these spheroids by all-trans-retinoic acid (ATRA), a potent inducer of in vitro and in vivo differentiation, decreases their proteolytic activity and ability to invade Matrigel-coated filters.

[The multidrug resistance phenotype: some morphological and biological characteristics except efflux pump].

Recent data from the literature together with personal results strongly suggest that multidrug resistance phenotype is overwhelming the sole expression of P170 glycoprotein efflux pump. Morphological alterations have been put in evidence in MDR cells after transmission and scanning electron microscopy. They include presence of osmiophilic vesicles and modifications of nuclear and nucleolar chromatin.

Increased accumulation of drugs in multidrug-resistant cells induced by liposomes.

A multidrug-resistant cell such as the human lymphoblastic leukemic cell CEM/VLB100 accumulates far less vinblastine (VLB) than its drug-sensitive parent, CEM. When CEM/VLB100 cells are exposed to liposomes consisting of the phospholipids cardiolipin, dioleoylphosphatidic acid, or phosphatidylinositol bearing unsaturated fatty acids and then tested for uptake of VLB, accumulation of drug rapidly rises to levels approaching those of CEM cells, which are relatively unaffected by the liposome treatment. The liposomes are not carriers of entrapped drug.

Inhibition of collagenolytic activity in human leukemic K562 cells by tamoxifen.

Presence of a collagenolytic activity has been demonstrated in the human leukemic cell line K562. Among various effectors studied, tamoxifen, a well-known antiestrogenic compound, exhibited a strong inhibitory effect. After 3 days of culture in the presence of 10(-7) M of tamoxifen, 75% of the collagenolytic activity was inhibited.

Quantitative morphological analysis of adriamycin-resistant human K562 leukemic cells.

The morphological changes associated with Adriamycin resistance in a human leukemic cell line have been investigated by image analysis. An Adriamycin-resistant subline of the human erythroleukemic K562 cell line has been established. Three sets of cells have been analysed: sensitive cells, resistant cells cultured in the continuous presence of Adriamycin, and resistant cells cultured without the drug.