Differential effects of retinoic acid on the in vitro growth and cell‐surface glycoconjugates of 2 human head and neck squamous‐cell carcinomas

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Abstract
As a part of an assessment of the potential use of retinoids in preventive and adjuvant treatment of HNSCC, we examined the effects of β‐all‐trans retinoic acid (RA) on the growth and cell‐surface glycoconjugates of 2 HNSCC cell lines. These lines, designated 1483 and 183A, were established from an untreated patient with a well‐differentiated SCC of the re‐tromolar trigone and one with a poorly differentiated SCC of the tonsil. Whereas the 1483 cells were sensitive to RA in that their anchorage‐dependent growth, their colony growth on solid substratum, and their anchorage‐independent growth in semi‐solid agarose gel were all inhibited in a dose‐dependent fashion by RA concentrations in the range between I nM and 10 μM, the 183A cells were not inhibited by RA. Their anchorage‐dependent growth and colony formation were stimulated by RA, whereas their anchorage‐dependent colony formation was not altered. Cell‐surface glycoconjugates were modulated by RA in the sensitive 1483 cells but not in the 183A cells. Treatment of the 1483 cells resulted in a large increase in the cell‐surface labelling of high‐molecular‐weight (Mr > 400,000) galactoglycoconjugates and sialoglycoconjugates, as well as an Mr 280,000 sialoglycoconjugate. Glycoconjugates with similar electrophoretic mobilities in polyacrylamide gels were labelled intensely on the surface of the 183A cells even before RA treatment and only minor changes were noticed in their labelling after treatment. These results demonstrate that RA can exert different effects on different HNSCC lines, and suggest that correlations might exist between responsiveness to RA and the stage of differentiation of the HNSCC, and between modulation of cell growth and enhancement of cell‐surface glycoconjugate glycosylation by RA.