The present study describes the characterization and evaluation of novel anticancer conjugates, 2,6-diisopropylphenol-docosahexaenoate (PP-DHA), and its analogues including 2,4-diisopropylphenol-docosahexaenoate (
DIPP-DHA), 2-isopropylphenol-docosahexaenoate (
IPP-DHA), 2-cyclohexanephenol-docosahexaenoate (CHP-DHA) and
phenol-
docosahexaenoate (P-DHA) on
breast cancer cell lines. Representative
breast cancer cell lines, based on
estrogen alpha receptor (ER) and oncogene Her-2 expression, were used and include MDA-MB-231 (ER-negative, Her-2-negative), MCF-7 (ER-positive, Her-2-negative) AU565 (ER-negative, Her-2-positive) and MDA-MB-361 (ER-positive, Her-2-positive). The PP-DHA conjugate significantly inhibited cell growth and induced cell loss in the
breast cancer cell lines similarly; however, this conjugate was not effective against normal mammary epithelial cells. The effect of various conjugates were in PP-DHA>
IPP-DHA>
DIPP-DHA>CHP-DHA>>P-DHA order. PP-DHA and
IPP-DHA conjugates were stable in human and mouse serum. Furthermore, the non-hydrolyzable
amide-linked conjugate analogues affected
breast cancer cells in a manner similar to that of the
ester-linked conjugates. This suggests that
ester-linked PP-DHA and
IPP-DHA conjugates were stable during treatment to
breast cancer cells due to structural hindrance. PP-DHA did not affect
PPARalpha or
PPARgamma activities but its anticancer effects appear to be mediated in part though the inhibition of
histone deacetylase (HDAC) activity. Further experiments are needed to confirm their molecular target and to test the effectiveness of these compounds in an in vivo model for their anticancer properties. In conclusion, these results suggest that the novel PP-DHA and
IPP-DHA conjugates and their
amide derivatives may be useful for the treatment of
breast cancer.