Table 11

Effect of oral administration of tea, decaffeinated tea, and caffeine on tumorigenesis, the size of the parametrial fat pads and the thickness of the dermal fat layer in SKH-1 mice treated previously with UVB (high-risk mice)

Female SKH-1 mice were treated with UVB (30 mJ/cm2) twice a week for 22 weeks, and UVB administration was stopped. These tumor-free initiated mice had a high-risk of developing skin tumors during the next several months, and they were treated for 23 weeks with 0.6% lyophilized green tea (GT, 6 mg tea solids/ml), black tea (BT, 6 mg tea solids/ml), or decaffeinated green or black tea (DGT or DBT, 6 mg tea solids/ml) as their sole source of drinking fluid. Other mice received 0.044% caffeine (CF, 0.44 mg/ml) or 0.6% lyophilized decaffeinated teas plus 0.044% caffeine. Tumors were classified by histological evaluation of skin samples from the 179 mice with skin nodules, and calculations of tumors/mouse included data from all 217 mice alive at the end of the experiment. The data for total tumors include papillomas, keratoacanthomas, and squamous cell carcinomas.

The combined length of the two parametrial fat pads from all 217 mice alive when the experiment was terminated was measured and graded as follows: 1 (<1 cm), 2 (1–2 cm), or 3 (>2 cm). The thickness of the dermal fat layer was measured in 5–10 representative nontumor areas of the skin (>0.5 cm away from tumors) from 19–28 mice per group (total 179 mice) using a light microscope with an ocular micrometer and 100-fold magnification. The 152 tumor-bearing mice were used for calculations of the thickness of the dermal fat layer under tumors.

The values represent the mean ± SE, and the values in parentheses represent percentage decrease compared with the drinking water positive control group. Statistical evaluation of differences from the water-positive control group was done by the Dunnett’s T test. The data for total tumors includes a small number of squamous cell papillomas. (Taken from Ref. 323 .)

TreatmentNumber of miceKeratoacanthomas (tumors per mouse)Squamous cell carcinomas (tumors per mouse)Total tumors (tumors per mouse)Size of fat pads (relative units)Thickness of dermal fat layer away from tumors (μm)Thickness of dermal fat layer under tumors (μm)
Water284.00 ± 0.471.82 ± 0.306.18 ± 0.711.41 ± 0.11162 ± 960 ± 4
0.6% GT281.25 ± 0.47a0.68 ± 0.30b2.00 ± 0.71a0.64 ± 0.11a100 ± 11a28 ± 6a
(69)(63)(68)(54)(39)(53)
0.6% BT271.30 ± 0.48a0.70 ± 0.31c2.11 ± 0.72a0.95 ± 0.11b88 ± 10a31 ± 6a
(68)(61)(66)(32)(46)(49)
0.6% DGT272.93 ± 0.481.85 ± 0.314.96 ± 0.721.62 ± 0.11152 ± 1055 ± 4
(27)(0)(20)(0)(6)(8)
0.6% DBT262.88 ± 0.491.58 ± 0.314.62 ± 0.741.23 ± 0.12150 ± 1051 ± 4
(28)(13)(25)(13)(8)(14)
0.044% CF271.70 ± 0.48a0.63 ± 0.31b2.41 ± 0.72a0.62 ± 0.11a98 ± 10a31 ± 6a
(57)(65)(61)(56)(40)(49)
DGT + CF251.04 ± 0.50a0.92 ± 0.322.00 ± 0.75a0.61 ± 0.12a105 ± 11a29 ± 6a
(74)(50)(68)(57)(35)(51)
DBT + CF290.72 ± 0.46a0.38 ± 0.30a1.17 ± 0.70a0.89 ± 0.11a87 ± 11a24 ± 7a
(82)(79)(81)(37)(47)(61)
  • a P < 0.01.

  • b P < 0.05.

  • c P < 0.1.