Lookup NU author(s): Dr Chris Redfern
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The nuclear proto-oncogenes are involved in transcriptional regulation and control many cell processes. The role of changes in proto-oncogene expression in controlling the balance between proliferation and differentiation was studied in cultured keratinocytes. Normal human keratinocytes were grown in the serum-free medium MCDB153 with an extracellular calcium concentration of 70 mu M. After treatment with different differentiation conditions, cellular RNA was size-fractionated on agarose gels and transferred to nylon membranes which were subsequently hybridized with c-myc, c-jan, and H-ms P-32-labelled probes. Relative RNA loading was assessed using probes for beta-actin and ribosomal 18s RNA. Inducing differentiation by increasing the calcium concentration of the medium from 70 mu M to 1.5 mM resulted in a marked decrease in c-myc RNA levels to 26% of control levels within 8 h. After 48 h in 1.5 mM calcium, c-myc levels had recovered to approximately 50% of control levels. There was a gradual reduction in c-jun levels to 56% of control levels by 4 days. Treatment with 10 nM TPA, which also induces keratinocyte differentiation, reduced c-myc RNA levels to 70% of control levels during the first 4 h, but thereafter c-myc levels remained approximately constant for a further 20 h. TGF beta (2 ng/ml), which inhibits keratinocyte growth without inducing differentiation, did not alter c-myc RNA levels over a 4-day period. There were no changes in c-myc levels following the addition of retinoic acid and none of the conditions altered H-ras levels. We conclude that c-myc levels are high in proliferating keratinocytes and decrease following differentiation stimuli, but further work is required to investigate the underlying molecular mechanisms of differentiation.
Author(s): Sharpe GR, Fisher C, Redfern CPF
Publication type: Article
Publication status: Published
Journal: Archives of Dermatological Research
Print publication date: 01/10/1994
ISSN (print): 0340-3696
ISSN (electronic): 1432-069X
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