Aggarwal Abhishek, Höbaus Julia, Tennakoon Samawansha, Prinz-Wohlgenannt Maximilian, Graça João, Price Sally A, Heffeter Petra, Berger Walter, Baumgartner-Parzer Sabina, Kállay Enikö
Department of Pathophysiology and Allergy Research, Medical University of Vienna, Vienna, Austria.
Safety Assessment, AstraZeneca, Macclesfield, UK.
J Steroid Biochem Mol Biol. 2016 Jan;155(Pt B):231-8. doi: 10.1016/j.jsbmb.2015.02.006. Epub 2015 Mar 7.
Epidemiological studies suggest an inverse correlation between dietary calcium (Ca(2+)) and vitamin D intake and the risk of colorectal cancer (CRC). It has been shown in vitro that the active vitamin D metabolite, 1,25-dihydroxyvitamin D3 (1,25-D3) can upregulate expression of the calcium-sensing receptor (CaSR). In the colon, CaSR has been suggested to regulate proliferation of colonocytes. However, during tumorigenesis colonic CaSR expression is downregulated and we hypothesized that the loss of CaSR could influence the anti-tumorigenic effects of Ca(2+) and vitamin D. Our aim was to assess the impact of CaSR expression and function on the anti-neoplastic effects of 1,25-D3 in colon cancer cell lines. We demonstrated that in the healthy colon of mice, high vitamin D diet (2500 IU/kg diet) increased expression of differentiation and apoptosis markers, decreased expression of proliferation markers and significantly upregulated CaSR mRNA expression, compared with low vitamin D diet (100 IU/kg diet). To determine the role of CaSR in this process, we transfected Caco2-15 and HT29 CRC cells with wild type CaSR (CaSR-WT) or a dominant negative CaSR mutant (CaSR-DN) and treated them with 1,25-D3 alone, or in combination with CaSR activators (Ca(2+) and NPS R-568). 1,25-D3 enhanced the anti-proliferative effects of Ca(2+) and induced differentiation and apoptosis only in cells with a functional CaSR, which were further enhanced in the presence of NPS R-568, a positive allosteric modulator of CaSR. The mutant CaSR inhibited the anti-tumorigenic effects of 1,25-D3 suggesting that the anti-neoplastic effects of 1,25-D3 are, at least in part, mediated by the CaSR. Taken together, our data provides molecular evidence to support the epidemiological observation that both, vitamin D and calcium are needed for protection against malignant transformation of the colon and that their effect is modulated by the presence of a functional CaSR. This article is part of a Special Issue entitled '17th Vitamin D Workshop'.
流行病学研究表明，膳食钙（Ca(2+)）和维生素D摄入量与结直肠癌（CRC）风险之间呈负相关。体外实验表明，活性维生素D代谢物1,25-二羟基维生素D3（1,25-D3）可上调钙敏感受体（CaSR）的表达。在结肠中，CaSR被认为可调节结肠细胞的增殖。然而，在肿瘤发生过程中结肠CaSR表达下调，我们推测CaSR的缺失可能会影响Ca(2+)和维生素D的抗肿瘤作用。我们的目的是评估CaSR表达和功能对1,25-D3在结肠癌细胞系中抗肿瘤作用的影响。我们证明，与低维生素D饮食（100 IU/kg饮食）相比，在小鼠的健康结肠中，高维生素D饮食（2500 IU/kg饮食）可增加分化和凋亡标志物的表达，降低增殖标志物的表达，并显著上调CaSR mRNA表达。为了确定CaSR在此过程中的作用，我们用野生型CaSR（CaSR-WT）或显性负性CaSR突变体（CaSR-DN）转染Caco2-15和HT29结肠癌细胞，并单独用1,25-D3或与CaSR激活剂（Ca(2+)和NPS R-568）联合处理它们。1,25-D3仅在具有功能性CaSR的细胞中增强了Ca(2+)的抗增殖作用，并诱导了分化和凋亡，在CaSR的正性变构调节剂NPS R-568存在的情况下，这些作用进一步增强。突变型CaSR抑制了1,25-D3的抗肿瘤作用，表明1,25-D3的抗肿瘤作用至少部分是由CaSR介导的。综上所述，我们的数据提供了分子证据，支持流行病学观察结果，即维生素D和钙对于预防结肠恶性转化都是必需的，并且它们的作用受到功能性CaSR存在的调节。本文是名为“第17届维生素D研讨会”的特刊的一部分。
