NUTRITION AND CANCER, 58(1), 6065Copyright C 2007, Lawrence Erlbaum Associates, Inc.

Comparison of White Tea, Green Tea, Epigallocatechin-3-Gallate,and Caffeine as Inhibitors of PhIP-Induced Colonic Aberrant Crypts

Orianna Carter, Rong Wang, W. Mohaiza Dashwood, Gayle A. Orner, Kay A. Fischer,Christiane V. Lohr, Clifford B. Pereira, George S. Bailey, David E. Williams,

and Roderick H. Dashwood

Abstract: There is growing interest in the possible healthbenefits of tea. We reported previously on the inhibi-tion by white tea of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP)-induced colonic aberrant crypt foci (ACF)in the rat (4). To distinguish between blocking and suppress-ing effects, and thus provide mechanistic insights into pre-vention during the initiation versus post-initiation phasesof carcinogenesis, white tea, and green tea were adminis-tered at 2% (w/v) as the sole source of drinking fluid ei-ther 2 wk before and 2 wk during PhIP dosing (100 mg/kg,every other day by oral gavage), or starting 1 wk afterthe carcinogen and continued until the study was termi-nated at 16 wk. In the former protocol, each tea producedmarginal inhibition of colonic ACF, despite evidence forchanges in several hepatic enzymes involved in heterocyclicamine metabolism. Post-initiation, however, the data wereas follows (ACF/colon, mean SE): PhIP/water 12.2 1.5; PhIP/white tea 5.9 0.9 (P < 0.01); PhIP/caffeine5.9 1.5 (P < 0.01); PhIP/EGCG 3.5 0.8 (P caffeine = white tea >green tea (compare Fig. 4C with Fig. 3, right panel). Al-though EGCG augmented the apoptosis index according tothe in situ oligo ligation assay, we interpret this finding withcaution, because an alternative and more specific apoptosisassay, cleaved caspase-3, revealed no significant increase byany of the test agents, including EGCG (Fig. 5).

Tea catechins synergistically inhibited TNF- release incultured cells (12), but our results suggest that antagonisticeffects might occur between tea constituents in vivo. Thiscould explain the rather surprising observation that EGCGalone was more effective than white tea, which containedthe same concentration of EGCG as well as several othercatechins and caffeine. Caffeine is an interesting compound

because it is present in tea and several other beverages con-sumed by humans, and in rats treated simultaneously withcaffeine and heterocyclic amines there was evidence for co-carcinogenicity in the colon but protection in the mammarygland (13,14). Further studies are warranted on the protocol-dependent and organ-specific effects of caffeine and otherconstituents in tea, including possible assessment of apopto-sis and cell proliferation indices directly in the early biomark-ers. This is feasible only for large, well-defined ACF, and istechnically more time demanding than scoring labeling in-dices in randomly selected regions of the colon, which in-cludes non-involved areas as well as possible early lesions.Changes at later times might be more pertinent, such as theinhibition of frank tumors and alterations in molecular targetssuch as -catenin and Apc (3,1517).

In summary, we evaluated two different protocols forwhite tea and green tea against PhIP-induced ACF in therat. Both teas induced phase 1 and phase 2 enzymes asso-ciated with PhIP metabolism and excretion, but had onlymarginal blocking effects towards ACF scored at 16 wk.In contrast, white tea, caffeine, and EGCG each suppressedPhIP-induced ACF significantly, in accordance with the rel-ative order of inhibition of cell proliferation in the coloniccrypts. Further studies appear to be warranted on the chemo-preventive effects of EGCG and caffeine post-initiation, in-cluding possible antagonistic effects in vivo. This should bedone in the context of physiologically relevant concentra-tions and the most likely inhibitory mechanisms (1). Overall,the study outcome provides interesting mechanistic leads for

64 Nutrition and Cancer 2007

Figure 5. No change in cleaved caspase-3 after treatment with green tea,white tea, EGCG, or caffeine. (A) Immunohistochemical staining of cleaved(active) caspase-3 identified positively-labeled cells (arrows) in the mid-dle third and upper third of the colonic crypt column. (B) The number ofpositively-stained cells was divided by the total number of cells and multi-plied by 100 to obtain percent labeling for the entire crypt. The labelingindex also was assessed separately for upper, middle, and lower regionswithin the crypt column (data not shown). Bars, mean SE, n = 56.

the timing of preventive intervention during multi-step coloncarcinogenesis.

Acknowledgments and Notes

We thank C. Riegger of DSM Nutritional Products for providingEGCG (TEAVIGOTM), and Q. Li, T.-W. Yu, M.C. Myzak, P. Tong, V.Elias, M. Moussaoui, and M. Louderback for assistance during necropsy.Laboratory Animal Service staff are gratefully acknowledged for helpwith animal care. We dedicate this work to the memory of Joy Ed-lund (Stash Tea Co., Portland, OR), who was instrumental in arrangingfor the supply of tea. This study was supported in part by NIH grantsCA90890, CA65525, and CA80176, and by Inkos White Tea (New York,NY). Address correspondence to R.H. Dashwood, Linus Pauling Institute,Oregon State University, Weniger Hall 503, Corvallis, OR 97331-6512.E-mail: rod.dashwood@oregonstate.edu.

Submitted 30 July 2006; accepted in final form 20 December 2006.

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