Ruth MacDonald - Prostate Cancer Research Projects

We have been investigating the effects of commonly available herbal compounds on the progression of prostate cancer in an animal model of this disease. The TRAMP mouse, is a transgenic model of prostate adenocarcinoma that was developed by Norm Greenberg, Baylor University. We have crossed these mice with mice that have interrupted expression of estrogen receptor alpha (ERaKO) to generate TRAMP x wild type and TRAMP x ERaKO animals. These animals were provided by Dr. Dennis Lubahn. The mice were fed diets containing no isoflavavones or genistein (250 mg/kg diet) from weaning. Of significance, all mice in our colonies are maintained on a casein-based AIN93G diet which is free of isoflavones. We produce all experimental diets in our Animal and Nutrition Core. After 5 months, prostate tissue was obtained, fixed and a histologic score was defined by trained veterinary histopathologists. A score of 1-6, with 1 being normal and 6 poorly differentiated cancer, was used. To simplify the data, we considered scores of 1-3 to be normal and 4-6 cancer.

As shown in Figure 1, TRAMP x wild type mice fed genistein had lower histopathologic scores (less cancer) than control-fed mice. The effect of genistein was absent in the TRAMP x ERaKO mice, which suggests the response is estrogen-receptor dependent.

We have ongoing experiments with Dr. Dennis Lubahn at the University of Missouri in these animals to examine the response to daidzein and a mixture of soy isoflavones. Furthermore, we have initiated experiments in which TRAMP mice are being fed diets containing mixtures of 7 commonly used herbal compounds. The primary investigator on this project is Nader Shenouda, Post-doctoral Fellow in the University of Missouri Center for Phytonutrient and Phytochemical Studies

One group of animals is being fed diets with genistein, quercetin and baicalein, another group with resveratrol, apigenin, curcumin and EGCG, and another group with all 7 compounds. Also, we have included a group of animals being fed a diet made with the commonly used 7 herbs that are enriched in each of the compounds.

To further explore the role of dietary compounds in prostate cancer, we are using cell culture experiments with the 7 compounds mentioned above. We have observed that each of the compounds displaced, to some degree, 3H-estradiol binding from mouse uteri, suggesting they were able to bind to estrogen receptors (Figure 2).

For each compound, we defined a dose at which 50% of growth of two cell lines, PC-3 and LNCaP, was inhibited (Table 1).

Table (1) IC 50 of the 7 compounds in PC-3 and LNCaP cell lines

	PC3	LNCaP
Quercetin	50 uM	25 uM
Baicalein	50 uM	75 uM
Apigenin	50 uM	20 uM
Genistein	50 uM	50 uM
Curcumin	25 uM	20 uM
EGCG	90 uM	100 uM
Resveratrol	50 uM	75 uM

We have also quantified cell cycle distribution in the cells following exposure to each compound, and found both G2/M and S phase arrest (Table 2). We have also measured apoptosis by TUNEL and DNA laddering. This work has been published. In ongoing work, we will be defining intracellular events associated with each compound to better define the role of these compounds in prostate cancer prevention.

	PC3 (% of the cells)			LNCaP (% of the cells)
	G1	S	G2M	G1	S	G2M
Control	78	5	17	82	3	15
Quercetin	53	8	30	66	6	28
Baicalein	59	12	29	68	5	27
Apigenin	58	6	36	62	7	31
Genistein	57	3	40	66	5	29
Curcumin	60	8	32	65	8	27
EGCG	48	30	22	45	32	23
Resveratrol	47	32	21	47	33	20

Related Publications:

Shenouda NS, Zhou Q, Browning JD, Ansell PJ, Sakla MS, Lubahn DB, MacDonald RS. Phytoestrogens in Common Herbs Regulate Prostate Cancer Cell Growth in Vitro. Nutrition and Cancer 2004 49(2):200-208.

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