Possible immunotherapeutic potentiation with D-fraction in prostate cancer cells.
J Hematol Oncol. 2008;1:25. Epub 2008 Dec 4. PMID: 19055833
ABSTRACT: BACKGROUND: Prostate cancer remains the most common malignancy among elderly men and the second leading cause of cancer death in the United States. Although several conventional therapies are currently available, they have a low efficacy and the more effective treatment modalities need to be established. Interferons (IFNs) are one of such options known as immunotherapy and demonstrated their antitumor effects on certain cancer types. Yet such antitumor activity should be improved or potentiated to have the satisfactory outcomes. In fact, combination therapy has been proposed as an alternative approach and is being underway in human and animal studies. Accordingly, we studied whether the combination of IFN-alpha and D-fraction (PDF), a bioactive mushroom extract, might potentiate anticancer activity of IFN-alpha in prostate cancer PC-3 cells in vitro. RESULTS: Potential effects of recombinant IFN-alpha2b (0-100,000 IU/ml), PDF (0-1,000 mug/ml), or their combinations were assessed on the growth of PC-3 cells at 72 h. Cell cycle analysis using a flow cytometer and Western blot analysis were performed to explore antiproliferative mechanism of these agents. The dose-dependent study showed that IFN-alpha2b up to 20,000 (20 K) IU/ml had no significant effects, but>60% growth reduction was attained60%) down-regulated in IFN/PDF-treated cells. CONCLUSION: The combination of IFN-alpha2b (10 K IU/ml) and PDF (250 mug/ml) is capable of inducing a ~65% reduction in PC-3 cell growth. This appears to be due to a synergistic potentiation of two agents, leading to a G1 cell cycle arrest. Thus, it is conceivable that PDF may potentiate IFN-alpha2b activity, improving immunotherapy for prostate cancer.