Do the dietary supplements epigallocatechin gallate or vitamin E cause a radiomodifying response on tumors in vivo? A pilot study with murine breast carcinoma

The primary aim of this study was to evaluate a systematic and reproducible assay to examine the potential radiomodifying effects of vitamin E (VE) or epigallocatechin gallate (EGCG), antioxidants commonly consumed by cancer patients as dietary supplements, on tumor control. C3H mice were randomized to a control diet or to the control diet supplemented with VE or EGCG. A tumor control dose 50% (TCD₅₀) assay was used to evaluate for a radiomodifying response in stage IV murine cancer (MCa-IV) tumors, implanted in the hindleg of mice, and allowed to grow to 8 mm before receiving a single dose of radiation. The effects of VE and EGCG on intratumoral angiogenesis and apoptosis were evaluated in a group of nonirradiated mice using immunohistochemical staining. Cell proliferation assays were conducted on MCa-IV tumors in vitro. EGCG slowed tumor growth rate by 10%. EGCG and VE slowed tumor regrowth by 24 to 25%. There were no significant differences in TCD ₅₀ values between the groups (control = 73.9 Gy, VE = 77.2 Gy, EGCG = 76.4 Gy); however, normal tissues were protected from late radiation effects (autoamputations) in the VE group. VE and EGCG increased tumor cell apoptosis and decreased tumor cell proliferation but had no effect on microvessel density. In this pilot study, neither VE nor EGCG exerted a significant radiomodifying effect on the MCa-IV tumor. Nonetheless, the suggestion of a small degree of tumor radioprotection by these antioxidant compounds warrants further research. As supplementation with VE radioprotected normal tissue, additional studies on this putative benefit are recommended.