Inhibition of Cell Cycle Progression by Hydroxytyrosol Is Associated with Upregulation of Cyclin-Dependent Protein Kinase Inhibitors p21WAF1/Cip1 and p27Kip1 and with Induction of Differentiation in HL60 Cells

Abstract

Recent evidence indicates that the cancer preventive activity of olive oil can be mediated by the presence of minor components, such as antioxidant phenolic compounds. However, their mechanisms of action remain largely unknown. In this study, we investigated the in vitro effects of one of the main olive oil phenols, hydroxytyrosol [3,4-dihydroxyphenylethanol (3,4-DHPEA)], on proliferation, cell cycle progression, apoptosis, and differentiation of HL60 human promyelocytic leukemia cells. 3,4-DHPEA showed a potent inhibitory activity on DNA synthesis, as evidenced by a 92% reduction of [3H]-thymidine incorporation at 100 micromol/L, and an induced apoptosis, as evidenced by the release of cytosolic nucleosomes and flow cytometry. This phenol, 3,4-DHPEA, was also able to inhibit the progression of the cell cycle in synchronized HL60 cells, which accumulated in the G0/G1 phase of the cell cycle after 25 h of treatment. Furthermore, 3,4-DHPEA induced differentiation on HL60 cells with a maximum effect (22% of cells) at 100 micromol/L after 72 h of treatment. Among the different proteins involved in the regulation of the cell cycle, 3,4-DHPEA reduced the level of cyclin-dependent kinase (CDK) 6 and increased that of cyclin D3. With regard to the CDK inhibitors, p15 was not altered by 3,4-DHPEA treatment, whereas the expression of p21(WAF1/Cip1) and p27(Kip1) was increased at both protein and mRNA levels. To our knowledge, these results provide the first evidence that 3,4-DHPEA may effect the expression of genes involved in the regulation of tumor cell proliferation and differentiation.

Natural Polyphenols that Display Anticancer Properties through Inhibition of Kinase Activity

“…Due to their structural similarity with these acid derivatives, several others phenolic analogues are reviewed here even if they do not contain acid function ( Table 1). The polyphenols which exert anticancer activity by targeting specific kinases include capsaicinoid derivatives (8 and 9, vanilloid derivatives of branched-chain fatty acids), found in some peppers of the Capsicum plant family [19,20], [6]gingerol (10) and [6]-paradol (11), two phenols structurally related to the vanilloid moiety with 16 carbon atoms (C6-C10) [21,22], tyrosol derivatives (12 and 13, phenylethanol compounds with 8 carbon atoms (C6-C2)), present in a variety of natural sources [23,24], rosmarinic acid (14, phenolic derivative of caffeic acid with 18 carbon atoms (C6-C6-C6)), found in many Lamiaceae herbs [25], and curcumin (15, diferuloyl derivative containing 19 carbon atoms (C6-C7-C6)), isolated from the ginger family (Zingiberaceae) [26,27]. Curcumin has a highly conjugated structure, and it is a major pigment in mustard and turmeric.…”

“…Alcohol or phenol functions can be glycosylated or esterified with gallic acid (Table 3). Flavonols, a group of flavonoid derivatives containing the 3-hydroxyl group in the pyrone ring, are exemplified by quercetin (22), myricetin (23) and kaempferol (24) [48][49][50]. Flavanoid derivatives containing the 2-phenyl-3,4-dihydro-2H-chromen-3-ol skeleton are more commonly referred to as flavanols ( Table 3).…”

“…Although multiple mechanisms could explain this anticancer activity, inhibition of protein kinase C (PKC ) and glycogen synthase kinase (GSK-3 ) as well as activation of activator protein 1 (AP-1) were all involved in this process (Table 1) [21,22]. Hydroxytyrosol (13) was able to inhibit the progression of cell cycle in HL60 human promyelocytic leukemia cells [24]. This in vitro anticancer activity was associated with a reduction in the levels of cyclin-dependent kinase 6 (CDK6) and an increase of CDKi p21WAF1/Cip1 and p27 Kip1 [24].…”

“…Hydroxytyrosol (13) was able to inhibit the progression of cell cycle in HL60 human promyelocytic leukemia cells [24]. This in vitro anticancer activity was associated with a reduction in the levels of cyclin-dependent kinase 6 (CDK6) and an increase of CDKi p21WAF1/Cip1 and p27 Kip1 [24]. On the other hand, tyrosol (12) was associated with inhibition of protein kinase C (PKC) [23].…”

Cytotoxic and Apoptotic Effects of Hydroxytyrosol on Ovarian Cancer Cell Lines: Relationship of Cytotoxic Effect with ERK 1/2 Pathway

“…When oleuropein is naturally subjected to hydrolysis in the course of the ripening process of olives, HT is released through the elenolic acid 7 . It has been reported in various in vitro and in vivo studies that HT has an anti-cancer effect with its cytotoxic and apoptotic characteristics and that it also plays an anti-tumoral role in the prevention of angiogenesis [8][9][10][11][12][13][14] . According to the current literature, no study has been found as to whether or not HT has any anti-proliferative effect in any type of ovarian cancer.…”