Modulation of Vitamin D‐induced growth inhibition in melanoma cell lines: implications for an important function of vitamin D receptor (VDR) and 1,25‐dihydroxyvitamin D3‐24‐hydroxylase (24‐OHase) expression, histonedeacetylation, and calpain activity
You can manage bookmarks using lists, please log in to your user account for this.
Media type:
E-Article
Title:
Modulation of Vitamin D‐induced growth inhibition in melanoma cell lines: implications for an important function of vitamin D receptor (VDR) and 1,25‐dihydroxyvitamin D3‐24‐hydroxylase (24‐OHase) expression, histonedeacetylation, and calpain activity
Description:
<jats:p>Increasing evidence indicates an important role of the skin vitamin D system for tumorigenesis and progression of malignant melanoma. We have now characterized the vitamin D system in melanoma cell lines, detecting strong RNA expression of vitamin D receptor (VDR), 25‐hydroxyvitamin D‐1α‐hydroxylase (1αOHase), vitamin D‐25‐hydroxylase (25OHase) and 1,25‐dihydroxyvitamin D‐24‐hydroxylase (24OHase) in various melanoma cell lines (MEWO, SKMEL28, BU47HOM) using real time PCR (LightCycler) and specific hybridisation probes. We then have analyzed effects of 1,25‐dihydroxyvitamin D<jats:sub>3</jats:sub> and analogs (EB 1089, MC 1288) on proliferation and apoptosis as well as on expression of VDR, 1αOHase), 25OHase, and 24OHase in various melanoma cell lines (BUHOM, MEWO, SKMEL)<jats:italic>in vitro</jats:italic>. Using a tetrazolium salt (WST‐1) based colorimetric assay, we detected dose‐dependent inhibition of cell growth (up to 40%) induced by calcitriol or its analogs. Treatment of melanoma cells with calcitriol resulted in decreased immunoreactivity of proliferation markers including Ki‐67 and PCNA. Flow cytometry experiments (bcl‐2, bcl‐xl, bcl‐xs, bcl‐x, bax, CD95) and analysis of annexin Pi expression revealed no induction of apoptosis by calcitriol (10<jats:sup>−7</jats:sup> M) or its analogs, while increased levels of bcl‐2 protein were detected. Additionally, we show modulation of vitamin D‐induced inhibition of cell proliferation by calpain inhibitors I and II (Calbiochem) as well as by inhibitors of histonedeacetylation (sodium butyrate, trichostatin A). In conclusion our findings indicate that (i) vitamin D analogs suppress proliferation but do not induce apoptosis in melanoma cell lines, (ii) induction of VDR and 24‐OHase expression as well as histonedeacetylation and calpain activity modulate vitamin D‐induced growth inhibition, (iii) new calcitriol analogs exerting less systemic side effects may be interesting candidates for the treatment of metastasizing malignant melanoma.</jats:p>