Sertznig Pit, Dunlop Tom, Seifert Markus, Tilgen Wolfgang, Reichrath Jörg
Department of Dermatology, The Saarland University Hospital, Homburg/Saar, Germany.
Anticancer Res. 2009 Sep;29(9):3647-58.
The expression and signaling of the vitamin D receptor (VDR) and peroxisome proliferator-activated receptor (PPAR) alpha, delta, gamma was investigated in the melanoma cell line MeWo. Using real-time PCR, the mRNA of the nuclear receptors (NR) was detected. The strongest expression was found for the VDR, approximately 3-fold higher compared to the expression of PPARalpha or PPARdelta, and the weakest expression was for PPARgamma. After treatment with corresponding ligands, the expression of the VDR, PPARalpha and PPARdelta was elevated up to 5-fold, while the PPARgamma expression was not significantly affected. Treatment with 1alpha,25-dihydroxyvitamin D3 (1,25(OH)2D3, calcitrol) resulted in 40% inhibition of MeWo cell proliferation, that was associated with a 5-fold increase in VDR mRNA. Interestingly, cell proliferation was differentially modulated by treatment with the PPAR ligands. While docosahexaenoic acid (DHA) treatment resulted in a statistically significant increase (approximately 10%), the other PPAR ligands inhibited MeWo cell proliferation. GW501516 (PPARdelta ligand) and WY14643 (PPARalpha ligand) both had an antiproliferative effect of approximately 10%. These antiproliferative effects were not associated with modulation of PPARalpha or PPARdelta expression. In contrast, stimulation of MeWo proliferation by DHA was associated with a 3- and 4-fold increase in the expression of PPARalpha and PPARdelta, respectively. Analyzing the cross-talk between the VDR and PPAR signaling pathways, the 1,25(OH)2D3 treatment resulted in an approximately 2-fold increase in expression of PPARalpha and PPARdelta, while the expression of PPARgamma was unaffected. Treatment with GW501516 and WY14643 resulted in an increase in the VDR expression (2-fold after 120 h). The simultaneous treatment with 1,25(OH)2D3 partially antagonised the DHA- and alpha-linolenicacid (ALA)-induced up-regulation of PPAR expression. In contrast, treatment with the PPAR ligands had no pronounced effect on the 1,25(OH)2D3-induced increase in VDR expression. Simultaneous treatment with the PPAR ligands bezafibrate or ALA resulted in an up to 6-fold reduction of the 1,25(OH)2D3-induced elevation of the 1alpha,25-dihydroxyvitamin D3-24-hydroxylase (CYP24A1) expression. Simultaneous treatment with the PPAR ligands and 1,25(OH)2D3 resulted in only marginal modulation of 1,25(OH)2D3-induced inhibition of cell proliferation. However, simultaneous treatment with bezafibrate and 1,25(OH)2D3 resulted in a statistically significant partial antagonisation of the 1,25(OH)2D3-induced inhibition of MeWo cell proliferation. In conclusion, PPAR and VDR have a role in growth regulation in melanoma cells and functionally relevant cross-talk between these nuclear signaling pathways is indicated, but not at the level of cell proliferation, where 1,25(OH)2D3 has a dominant effect.
在黑色素瘤细胞系MeWo中研究了维生素D受体（VDR）和过氧化物酶体增殖物激活受体（PPAR）α、δ、γ的表达及信号传导。采用实时PCR检测核受体（NR）的mRNA。发现VDR表达最强，与PPARα或PPARδ的表达相比约高3倍，而PPARγ表达最弱。用相应配体处理后，VDR、PPARα和PPARδ的表达升高至5倍，而PPARγ表达未受显著影响。用1α,25 - 二羟基维生素D3（1,25(OH)2D3，骨化三醇）处理导致MeWo细胞增殖受到40%的抑制，这与VDR mRNA增加5倍相关。有趣的是，PPAR配体处理对细胞增殖有不同的调节作用。虽然二十二碳六烯酸（DHA）处理导致统计学上显著增加（约10%），但其他PPAR配体抑制MeWo细胞增殖。GW501516（PPARδ配体）和WY14643（PPARα配体）均具有约10%的抗增殖作用。这些抗增殖作用与PPARα或PPARδ表达的调节无关。相反，DHA刺激MeWo增殖分别与PPARα和PPARδ表达增加3倍和4倍相关。分析VDR和PPAR信号通路之间的相互作用，1,25(OH)2D3处理导致PPARα和PPARδ表达增加约2倍，而PPARγ表达未受影响。用GW501516和WY14643处理导致VDR表达增加（120小时后增加2倍）。1,25(OH)2D3与DHA和α - 亚麻酸（ALA）同时处理部分拮抗了PPAR表达的上调。相反，PPAR配体处理对1,25(OH)2D3诱导的VDR表达增加没有明显影响。PPAR配体苯扎贝特或ALA与1,25(OH)2D3同时处理导致1,25(OH)2D3诱导的1α,25 - 二羟基维生素D3 - 24 - 羟化酶（CYP24A1）表达升高最多降低6倍。PPAR配体与1,25(OH)2D3同时处理仅对1,25(OH)2D3诱导的细胞增殖抑制有轻微调节作用。然而，苯扎贝特与1,25(OH)2D3同时处理导致1,25(OH)2D3诱导的MeWo细胞增殖抑制有统计学上显著的部分拮抗作用。总之，PPAR和VDR在黑色素瘤细胞的生长调节中起作用，表明这些核信号通路之间存在功能相关的相互作用，但在细胞增殖水平上不存在，其中1,25(OH)2D3具有主导作用。
