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Cranberry proanthocyanidins are cytotoxic to human cancer cells and sensitize platinum-resistant ovarian cancer cells to paraplatin

Singh AP, Singh RK, Kim KK, Satyan KS, Nussbaum R, Torres M, Brard L and Vorsa N
Phytother Res 23(8):1066-74

Polyphenolic extracts of the principal flavonoid classes present in cranberry were screened in vitro for cytotoxicity against solid tumor cells lines, identifying two fractions composed principally of proanthocyanidins (PACs) with potential anticancer activity. Matrix-Assisted Laser Desorption/Ionization Time-Of-Flight Mass Spectrometry (MALDI-TOF-MS) analysis of the proanthocyanidins (PACs) fractions indicated the presence of A-type PACs with 1-4 linkages containing between 2-8 epicatechin units with a maximum of 1 epigallocatechin unit. PACs exhibited in vitro cytotoxicity against platinum-resistant human ovarian, neuroblastoma and prostate cancer cell lines (IC50 = 79-479 microg/mL) but were non-cytotoxic to lung fibroblast cells (IC50 > 1000 microg/ml). SKOV-3 ovarian cancer cells treated with PACs exhibited classic apoptotic changes. PACs acted synergistically with paraplatin in SKOV-3 cells. Pretreatment of SKOV-3 cells with PACs (106 microg/ml) resulted in a significant reduction of the paraplatin IC50 value. Similarly, in a BrdU incorporation assay, co-treatment of SKOV-3 cells with PACs and paraplatin revealed reduced cell proliferation at lower concentrations than with either individually. In SKOV-3 cell cultures co-treated with PAC-1 and paraplatin, an HPLC analysis indicated differential quantitative presence of various PAC oligomers such as DP-8, -9, -11 and -14 indicating either selective binding or uptake. Cranberry proanthocyanidins exhibit cell-line specific cytotoxicity, induce apoptotic markers and augment cytotoxicity of paraplatin in platinum-resistant SKOV-3 ovarian cancer cells.

A Flavonoid Fraction from Cranberry Extract Inhibits Proliferation of Human Tumor Cell Lines

Ferguson PJ,Kurowska E, Freeman DJ, Chambers AF,
J Nutr 134:1529-1535

In light of the continuing need for effective anticancer agents, and the association of fruit and vegetable consumption with reduced cancer risk, edible plants are increasingly being considered as sources of
anticancer drugs. Cranberry presscake (the material remaining after squeezing juice from the berries), when fed to mice bearing human breast tumor MDA-MB-435 cells, was shown previously to decrease the growth and
metastasis of tumors. Therefore, further studies were undertaken to isolate the components of cranberry that
contributed to this anticancer activity, and determine the mechanisms by which they inhibited proliferation. Using
standard chromatographic techniques, a warm-water extract of cranberry presscake was fractionated, and an
acidified methanol eluate (Fraction 6, or Fr6) containing flavonoids demonstrated antiproliferative activity. The
extract inhibited proliferation of 8 human tumor cell lines of multiple origins. The androgen-dependent prostate cell
line LNCaP was the most sensitive of those tested (10 mg/L Fr6 inhibited its growth by 50%), and the estrogen independent breast line MDA-MB-435 and the androgen-independent prostate line DU145 were the least sensitive
(250 mg/L Fr6 inhibited their growth by 50%). Other human tumor lines originating from breast (MCF-7), skin
(SK-MEL-5), colon (HT-29), lung (DMS114), and brain (U87) had intermediate sensitivity to Fr6. Using flow
cytometric analyses of DNA distribution (cell cycle) and annexin V-positivity (apoptosis), Fr6 was shown in
MDA-MB-435 cells to block cell cycle progression (P 0.05) and induce cells to undergo apoptosis (P 0.05) in
a dose-dependent manner. Fr6 is potentially a source of a novel anticancer agent.