Gibberellin A3 is a plant growth regulator used in many countries, including Egypt, to increase the growth of fruits and vegetables. The carcinogenic effect of gibberellin A3 was investigated in this study with Swiss albino mice. Administration of gibberellin A3 by gavage for 22 months induced a significant increase in their body weights. Tumors were induced in 18% of the males and 36% of the females and were located in the skin of the axillary region (sebaceous adenomas), breast (adenocarcinomas), and lung (adenocarcinomas and secondary metastatic deposits from breast tumors). Bronchocentric granulomas were induced in animals exposed to gibberellin A3 for 14 months. These results indicate that gibberellin A3 was carcinogenic in mice.

The carcinogenic effect of flour infested with beetles (Tribolium castaneum), biscuits made of this flour, and 1,4-benzoquinone (a quinoid secretion of this beetle) was investigated using Swiss albino mice. Force feeding flour infested with T. castaneum induced liver and spleen tumors (lympholeukemia) in 35.2% of the animals. The tumor incidence was 29% in mice force fed biscuits made of infested flour, and the tumors were located in the liver (lympholeukemia) and breast (adenocarcinoma type A). In animals fed 1,4-benzoquinone, the tumor incidence was 33.6%, and the tumors were located in the liver and spleen (lympholeukemia). It is speculated that 1,4-benzoquinone, alone or in combination with other quinoid secretions of the beetles present in the flour, may be responsible for tumor induction in the organs of mice.

Neoplasms developed in 18 of 98 toads, Bufo regularis, subjected to enforced feeding with bracken fern. They comprise 7 cases of adenocarcinoma in the ileum, 16 cases of hepatomas in the liver and 6 cases of neoplasms in the kidney due to metastases from the hepatomas. The results demonstrate that the Egyptian toad can be considered as an advantageous model for detecting the carcinogenicity of bracken fern, since the lesions occur faster than in other experimental animals.

Neoplastic lesions were induced in 10 out of 58 experimental toads (Bufo regularis) force-fed with alpha-ecdysone, which naturally occurs in the leaves of bracken fern (Pteris aquilina). The results of this study prove that alpha-ecdysone may be one of the factors responsible for the carcinogenicity of bracken fern plant fed to cattle and other experimental animals.

Biscuits made of flour infested with Tribolium castaneum induced the formation of hepatocellular carcinomas (22%) when force-fed to toads (Bufo regularis) at a dose level of 200mg/50g 3 times a week. Maximal time of exposure and observation was 16 weeks. Some metastatic deposits from the primary liver tumours were found in the kidneys. Thus, the carcinogenic potency of the biscuits was almost the same as that of the flour previously reported by the authors indicating that the temperature of the oven in which the biscuits were baked did not alter the carcinogenicity of the infested flour.