Synthesis and photochemical transformation of 3β,21-dihydroxypregna-5,7-dien-20-one to novel secosteroids that show anti-melanoma activity

Abstract

We have synthesized 3β,21-dihydroxypregna-5,7-dien-20-one (21(OH) 7DHP) and used UVB radiation to induce its photoconversion to analogues of vitamin D (pD), lumisterol (pL) and tachysterol (pT). The number and character of the products and the dynamics of the process were dependent on the UVB dose. The main products: pD and pT compounds were characterized by UV absorption, MS and NMR spectroscopy after RP-HPLC chromatography. In addition, formation of multiple oxidized derivatives of the primary products was detected and one of these derivatives was characterized as oxidized 21-hydroxyisotachysterol compound (21(OH)oxy-piT). These newly synthesized compounds inhibited growth of human melanoma cells in a dose dependent manner, with greater or equal potency to calcitriol. 3β,21-Dihydroxy-9β,10α-pregna-5,7-dien-20-one (21(OH)pL) and 21(OH)oxy-piT had higher potency against pigmented melanoma cells, while the EC 50 for compounds 21(OH)7DHP and (5Z,7E)-3β,21-dihydroxy-9,10-secopregna-5,7,10(19)-trien-20-one (21(OH)pD) were similar in both pigmented and nonpigmented cells. Moreover, 21(OH)7DHP and its derivatives inhibited proliferation of human epidermal HaCaT keratinocytes, albeit at a lower activity compared to melanoma cells. Importantly, 21(OH)7DHP derivatives strongly inhibited the colony formation of human melanoma cells with 21(OH)pD being the most potent. The potential mechanism of action of newly synthesized compounds was similar to that mediated by 1,25(OH) 2 D 3 and involved ligandinduced translocation of vitamin D receptor into the nucleus. In summary, we have characterized for the first time products of UVB-induced conversion of 21(OH)7DHP and documented that these compounds have selective, inhibitory effects on melanoma cells.

Lumisterol is metabolized by CYP11A1: Discovery of a new pathway

“…However, the synthetic hydroxyderivative of L3, 1,25-dihydroxy-L3, demonstrates biological activity apparently acting through binding to a second site on the vitamin D receptor (VDR) that mediates nongenomic responses (Dixon et al, 2011; Mizwicki et al, 2004; Rebsamen et al, 2002). Using chemical photosynthesis to generate vitamin D analogs with a short side chain (pD and aD compounds) we also generated pL and hydroxy-pL-derivatives (Zmijewski et al, 2008, 2009, 2011). Initial testing of their biological activity showed that pL inhibited the proliferation and stimulated the differentiation of leukemia cells (Slominski et al, 2010).…”

“…Initial testing of their biological activity showed that pL inhibited the proliferation and stimulated the differentiation of leukemia cells (Slominski et al, 2010). Its 21- hydroxyderivative, 3β,21-dihydroxy-9β,10α-pregna-5,7-dien-20-one (21(OH)pL3), also inhibited the proliferation of keratinocytes and melanoma cells, with high potency in the case of melanotic SKMEL-188 melanoma cells (Zmijewski et al, 2011). This steroid also stimulated translocation of a VDR-green-fluorescent-protein construct from the cytoplasm to the nucleus of melanoma cells suggesting that such effects can be mediated by the VDR.…”

Vitamin D derivatives enhance cytotoxic effects of H2O2 or cisplatin on human keratinocytes

“…7-DHP is further modified in this pathway by the classical enzymes of steroid metabolism resulting in 5,7-diene-analogues, some of which have been detected in vivo [15, 16]. In vitro studies have shown that these 5,7-dienes can be converted to the corresponding vitamin D analogues following UVB irradiation [9–11]. Several of these new derivatives, which have a short side chain compared to vitamin D 3 , display biological activity [6, 10, 11, 15, 17].…”

“…In vitro studies have shown that these 5,7-dienes can be converted to the corresponding vitamin D analogues following UVB irradiation [9–11]. Several of these new derivatives, which have a short side chain compared to vitamin D 3 , display biological activity [6, 10, 11, 15, 17]. In contrast, CYP11A1 acts directly on vitamin D to produce hydroxyvitamin D derivatives which retain a full-length side chain, with these products being detected both in vitro [12–14, 18, 19] and in vivo [20, 21].…”

“…The hydroxyvitamin D 3 metabolites produced by these pathways, including the major product, 20(OH)D 3 , are biologically active in both in vitro (reviewed in [8]) and in vivo [22] models. Since they are less prone to induce hypercalcemia than 1,25(OH) 2 D 3 [23, 24], they deserve special attention as potential therapeutics for the treatment of leukemia [23], melanoma [10, 11, 25, 26] and colorectal cancer [27]. …”