The possible chemopreventive effects of natural Egyptian
flaxseed oil on preneoplasia and
cancer formation were investigated in a rat medium-term colon
carcinogenesis bioassay. Male Wistar rats were divided into 6 groups. Groups 1, 3 and 5 were initiated by
1,2-dimethylhydrazine (
DMH) 20 mg/kg
body weight s.c. 8 times, twice a week to initiate colon
carcinogenesis. Groups 1 and 3 received 20% or 5%
flaxseed oil respectively in diet in post initiation stage until the end. Groups 2 and 4 served as a flaxseed dose corresponding controls without
carcinogen initiation, while rats in group 6 served as negative controls. Distribution and total numbers of
aberrant crypt foci (ACF), putative preneoplastic lesions, particularly those with ≥4 aberrant crypts (ACs), and the numbers and sizes of colon
tumors (
adenoma and
carcinoma) were significantly decreased by both treatment doses of flaxseeds as compared to group 5. Histochemical investigation revealed that the numbers of mucus-secreting cells in the colonic mucosa were reduced gradually during progression of colon
carcinogenesis. Intriguingly,
flaxseed oil caused the numbers and integrity of the mucus-secreting cells to retain close to normal levels and in a dose dependent manner. Moreover, the hematological parameters were almost constant between the groups particularly at the dose of 5% as compared to groups 5 and 6.
PCNA-labeled indexes (
PCNA-LI) in the
DMH-initiated colonic mucosa were found to be decreased by both doses of flaxseeds administration. In conclusion, the present study showed that the post initiation dietary administration of flaxseeds oil suppressed
DMH-induced colon
carcinogenesis in rats without significant side effects. The mechanism is likely to be through its inhibitory effects on early cellular proliferation and modulation of
mucin secretion properties in the initiated colonic mucosa.