Anti-Cancer Effects of Phenolic-rich Extracts of Button Mushrooms (Agaricus bisporus)
Open Access
- Author:
- Xu, Tongtong
- Graduate Program:
- Food Science
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- November 30, 2012
- Committee Members:
- Joshua D Lambert, Dissertation Advisor/Co-Advisor
Robert Bruce Beelman, Committee Member
Ryan John Elias, Committee Member
John Patrick Vanden Heuvel, Committee Member - Keywords:
- Agaricus bisporus
mushrooms
cancer
phenolic compounds
apoptosis
microarray
SCID mice
xenograft tumor - Abstract:
- Standard therapies for the treatments of cancer have limitations, including lack of effectiveness against hormone-refractory tumors and toxic side-effects. Dietary anti-cancer compounds have attracted increasing attention in cancer research because of their potential for lower toxic side effects and lower cost. Recent publications have shown that edible mushrooms are rich in phenolic compounds including simple phenolic acids and flavonoids. Given the available literature on the potential anticancer activity of phenolic compounds from other dietary sources, I hypothesized that the phenolic compounds in edible mushrooms can inhibit cancer cell growth. I compared the anti-proliferative effects of hot water, hexane, and ethyl acetate extracts of commonly consumed edible mushrooms against HT-29 human colon, H1299 lung, MCF-7 breast, and LNCaP & PC-3 prostate cancer cells using the 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Brown button mushroom ethyl acetate extract (BBEA) had the most potent inhibition against cancer cell growth with LNCaP prostate cancer cells being the most sensitive (IC50 = 0.1 mg/mL after 48 h). A direct relationship was observed between total phenolic content and anti-proliferative effect of mushroom extracts. With further study, I observed that BBEA time- and dose-dependently produced reactive oxygen species in cell culture medium in both the absence or presence of prostate cancer cells over 48 h treatment period. There was also a dramatic increase in the level of intracellular ROS and DNA damage response, indicating that BBEA-induced oxidative stress may represent the mechanism of prostate cancer cell growth inhibition. I used Western blot analysis, flow cytometry, and microarray analysis to study the anti-cancer mechanism of BBEA in prostate cancer cells. Increased cleavage of caspase-3 and PARP was observed after treatment of prostate cancer cells with BBEA for 12 – 24 h, indicating induction of apoptosis. BBEA arrested prostate cancer cells at G2 phase of the cell cycle and treatment with BBEA for 12 – 24 h decreased cyclin D1, E2, A, and B1 expression in LNCaP cells compared to vehicle-treated controls. Based on microarray results, the expression of 34 genes involved in transcription regulation, cell cycle progression, DNA damage/oxidative stress response, cytoskeleton stabilization, cell proliferation, and polyamine catabolism was modified by BBEA. Finally I investigated the tumor growth inhibitory effects of brown (BBEA) and white (WBEA) button mushroom ethyl acetate extracts in LNCaP human prostate cancer cell xenograft-bearing severe combined immunodeficiency (SCID) mice. Tumor volume (mm3) and final tumor weight (g) were reduced by 18 and 22%, respectively, in mice fed a 0.5% WBEA-containing diet. By contrast, BBEA had no inhibitory effect. There was a discrepancy of growth inhibitory effect of BBEA between in vitro and in vivo models. The potential reasons for this discrepancy will be discussed. In summary, phenol-rich button mushroom extracts inhibited prostate cancer cell growth in vitro, and caused apoptosis and cell cycle arrest. There was significant modulation of anti-proliferative genes by BBEA. These effects appear to be mediated in part by BBEA-induced oxidative stress. My present research provided the data to support the anti-cancer effects of button mushrooms and provides preliminary data for future mechanistic studies.