Brest Cancer

The incidence of cancer in Mediterranean countries is lower than in the rest of European countries and the United States (Keys et al. 1981). This is mostly described by the lower rate of the large bowel, breast, endometrial, and prostate cancers by a number of epidemiological studies, and the major reason for this, apart from possible genetic factors, is attributed to the dietary practices. The traditional Mediterranean diet is characterized by high consumption of foods of plant origin, relatively low consumption of red meat, and high consumption of olive oil and its products.

There are a number of studies on health beneficial effects of olive oil. Several studies have been reported that olive oil is more favorable against cancer than other forms of added lipids due to its high content of monounsaturated fatty acids (Owen et al. 2000a, b; Visioli and Galli 2001). In recent studies, diet containing 15% olive oil could significantly reduce pre-cancerous lesions in rat breast and colon (Martin-Moreno et al. 1994; Corona et al. 2007; Paula et al. 2007). However, similar amount of soy oil did not have such a protective effect as was expected (La Vecchia et al. 1998). Furthermore, the incidence of breast cancer was 70% less in the rats group fed olive oil than in the rats group fed safflower oil (Owen et al. 2000a, b). These data suggest that cancer preventive effect of olive oil is not only attributed to the “good” fat content. Recently, growing evidence show that minor compounds in olive oil may take a part in cancer protection as well, and more attention is paid to its phenolic compounds.

The phenolic compounds of olive oil and leaf are a complex mixture of compounds that include 3,4-dihydroxyphenylethanol (hydroxytyrosol), 4-hydroxyphenylethanol (tyrosol), 4-hydroxyphenylacetic acid, protocatechuic acid, caffeic acid and p-coumaric acid, among others (Litridou et al. 1997; Caponio et al. 1999). The concentration of the phenolic fraction is several times higher in olive leaf than in oil and varies depending on the cultivar and climate (Tables 1, ,2;2; Servili et al. 1999; Ryan et al. 2002; Abaza et al 2005). In vivo and in vitro studies suggest that these bioactive compounds exhibit powerful antioxidant activity (Visioli et al. 2000; Le Tutour and Guedon 1992). One of various phenolic compounds hydroxytyrosol seems to be among the most important ones. It is present in free form and as a constituent of complex molecules such as oleuropein in leaves and fruits.

Both hydroxytyrosol and oleuropein have been shown to possess anti-inflammatory, bactericidal and bacteriostatic activities (Yang et al. 2007). Some in vivo studies on olive leaf have shown that its extract can decrease blood pressure and dilate the coronary arteries surrounding the heart (Tuck and Hayball 2002). Moreover, hydroxytyrosol has been shown to have anti-cancer effect on human colon adenocarcinoma HT-29 cells and human promyelocytic leukemia HL-60 cells (Fabiani et al. 2002, 2006), have anti-melanogenesis activity, whereas oleuropein inhibited cell growth of LN-18, poorly differentiated glioblastoma; TF-1a, erythroleukemia; 786-O, renal cell adenocarcinoma; T-47D, infiltrating ductal carcinoma of the breastpleural effusion; RPMI-7951, malignant melanoma of the skin-lymph node metastasis; and LoVo, colorectal adenocarcinoma cells (Hamdi and Hamdi 2005). Even though anticancer properties of oleuropein and hydroxytyrosol were confirmed in vitro with different cell lines, studies of their protective effect from breast cancer have not been demonstrated. Since many epidemiological studies suggest the possible correlation between olive products consumption and incidence of breast cancer here we tried to elucidate the possible effect of the main phenolic compounds hydroxytyrosol and oleuropein of olive leaf on breast cancer using human breast cancer cell line MCF-7.