Six flavonoids [xanthohumol (XN), 2′,4′,6′,4-tetrahydroxy-3′-prenylchalcone (TP); 2′,4′,6′,4-tetrahydroxy-3′-geranylchalcone (TG); dehydrocycloxanthohumol (DX); dehydrocycloxanthohumol hydrate (DH); and isoxanthohumol (IX)] from hops (Humulus lupulus) were tested for their antiproliferative activity in human breast cancer (MCF-7), colon cancer (HT-29) and ovarian cancer (A-2780) cells in vitro. XN, DX and IX caused a dose-dependent (0.1 to 100 μm) decrease in growth of all cancer cells. After a 2-day treatment, the concentrations at which the growth of MCF-7 cells was inhibited by 50% (IC50) were 13.3, 15.7 and 15.3 μm for XN, DX and IX, respectively. After a 4-day treatment, the IC50 for XN, DX and IX were 3.47, 6.87 and 4.69 μm, respectively. HT-29 cells were more resistant than MCF-7 cells to these flavonoids. In A-2780 cells, XN was highly antiproliferative with IC50 values of 0.52 and 5.2 μm after 2 and 4 days of exposure, respectively. At 100 μm, all the hop flavonoids were cytotoxic in the three cell lines. Growth inhibition of XN- and IX-treated MCF-7 cells was confirmed by cell counting. XN and IX inhibited DNA synthesis in MCF-7 cells. As antiproliferative agents, XN (chalcone) and IX (flavanone isomer of XN) may have potential chemopreventive activity against breast and ovarian cancer in humans.
C.L. Miranda, J.F. Stevens, A. Helmrich, M.C. Henderson, R.J. Rodriguez, Y.H. Yang, et al.