1,25‐dihydroxy‐vitamin‐D 3 enhances antiproliferative effect and transcription of TGF‐β1 on human keratinocytes in culture

Both TGF‐β and 1,25‐dihydroxy‐vitamin‐D 3 (1,25(OH) 2 D 3 ) have been reported to decrease the proliferation of normal human keratinocytes. The effect and expression of TGF‐β in keratinocytes treated with 1,25(OH) 2 D 3 was investigated. Human keratinocytes were grown in the presence of various concentrations of TGF‐β and/or 1,25(OH) 2 D 3 prior to enumeration. TGF‐β, alone, has a half maximal dose of inhibition (ED 50 ) of approximately 750 pg/ml after seven days in culture in Keratinocyte Growth Medium (KGM ® ; Clonetics) supplemented with 1.5 mM calcium. When 1,25(OH) 2 D 3 (10 −7 M) was also added to cultures with various concentrations of TGF‐β, the ED 50 shifted an average of 2‐fold less. The presence of TGF‐β (10 pg/ml) augmented the potency of 1,25(OH) 2 D 3 by at least 10‐fold. In keratinocyte cultures, the antiproliferative effect of the two compounds together is synergistic. In keratinocytes grown for 1 week in the presence of 1,25(OH) 2 D 3 at 10 −6 M, the TGF‐β1 message increased approximately 5‐fold. An increase is detected within 2 hours of exposure to 1,25(OH) 2 D 3 . There was only a 50% increase in the levels of TGF‐β2 and no detection of TGF‐β3. When keratinocyte cultures were treated with 1,25(OH) 2 D 3 and neutralizing antibodies to TGF‐β, the induced‐antiproliferative activity was blocked by more than 50%. The keratinocytes produced more active than latent TGF‐β after growth with high doses of 1,25(OH) 2 D 3 . © 1992 Wiley‐Liss, Inc.