Synergistic potentiation of D-fraction with vitamin C as possible alternative approach for cancer therapy

Abstract

Maitake D-fraction or PDF is the bioactive extract of maitake mushroom (Grifola frondosa) and its active constituent is the protein-bound polysaccharide (proteoglucan), or more specifically known as beta-glucan. PDF has been extensively studied and a number of its medicinal potentials/properties have been unveiled and demonstrated. Those include various physiological benefits ranging from immunomodulatory and antitumor activities to treatment for hypertension, diabetes, hypercholesterolemia, viral infections (hepatitis B and human immunodeficiency virus), and obesity. Particularly, two major biological activities of PDF, immunomodulatory and antitumor activities, have been the main target for scientific and clinical research. To demonstrate and confirm such biological activities, numerous studies have been performed in vitro and in vivo or in clinical settings. These studies showed that PDF was indeed capable of modulating immunologic and hematologic parameters, inhibiting or regressing the cancer cell growth, and even improving quality of life of cancer patients. Synergistic potentiation of PDF with vitamin C demonstrated in vitro is rather interesting and may have clinical implication, because such combination therapy appears to help improve the efficacy of currently ongoing cancer therapies. Recently, intravenous administration of vitamin C has been often used to increase its physiological concentration and this useful procedure may further make this combination therapy feasible. Therefore, PDF may have great potential, either being used solely or combined with other agents, for cancer therapy. Such relevant and detailed studies will be described and discussed herein with a special focus on the combination of PDF and vitamin C as a viable therapeutic option.

Keywords: PDF; cancer therapy; maitake D-fraction; synergism; vitamin C.

Figure 1

Schematic structure of β-glucan.

Figure 2

Effect of PDF on PC-3 cell growth. PC-3 cells were cultured with the varying concentrations of PDF (0–1,000 μg/ml), and viable cell numbers were determined in 72 h. All data represent mean ± SD from three separate experiments. Notes: *p < 0.02; **p < 0.08. Abbreviations: PC-3, human prostate carcinoma cell line; PDF, Maitake D-fraction; SD, standard deviation.

Figure 3

Effect of VC. PC-3 cells were cultured with the indicated concentrations of VC, and viable cell numbers were determined in 72 h. All data are mean ± SD from three independent experiments. Note: *p < 0.05. Abbreviations: PC-3, human prostate carcinoma cell line; SD, standard deviation; VC, vitamin C.

Figure 4

Effects of PDF/VC combination on cell viability. PC-3 cells were treated for 24 h with the ineffective concentrations (0–250 μg/ml) of PDF in combination with the similarly ineffective concentrations (0–200 μM) of VC. Particularly, the combination of 150 μg/ml PDF and 200 μM VC resulted in >90% cell death (*p < 0.01) as shown here. Abbreviations: PC-3, human prostate carcinoma cell line; PDF, Maitake D-fraction; VC, vitamin C.

Figure 5

Assessment of lipid peroxidation (LPO) level with PDF/VC combination. Cells were exposed to the combination of PDF (150 μg/ml) and VC (200 μM) for merely 3 h, and the LPO levels in control, PDF alone-, VC alone-, and PDF/VC -exposed cells were determined for comparison, by measuring the amount of malondialdehyde (MDA) formed. The data are mean ± SD from three separate experiments. Notes: *p < 0.01. Abbreviations: PDF, Maitake D-fraction; SD, standard deviation; VC, vitamin C.

Figure 6

In situ hybridization assay. Cells were treated with the combination of PDF (150 μg/ml) and VC (200 μM) for 24 h and evaluated for apoptosis using ISH assay. A minimum of 100 cells from control and PDF/VC -treated cells were counted and assessed for staining. Over 90% (92/100) of PDF/VC -treated cells (B) were positively stained (with brown color), while >90% (93/100) of control cells (A) were negative for a stain (giving off green color). Abbreviations: PDF, Maitake D-fraction; VC, vitamin C.