Effects of a 15% orange-pulp diet on tumorigenesis and immune response in rats with colon tumors.
This study evaluated whether the feeding of rats with a 15% orange-pulp diet affects the lymphatic system and the tumorigenic response in rats exposed to a high dose of carcinogen. Five-week-old Sprague Dawley rats were divided into 2 groups fed a control chow diet or the same diet with 15% orange pulp. All rats were injected with 1,2-dimethylhydrazine (DMH) (20 mg/kg) weekly for 6 weeks. At 8 months, tumors, spleens and descending colon were taken from each group for analyses. Feeding rats the 15% orange-pulp diet did not reduce the tumor number but modified the number of adenocarcinomas found in the orange-pulp group compared to controls: 66.7% vs. 93.7%. The number of endophytic tumors was also significantly lower in the experimental group: 6.3% vs. 32.3% in controls. DMH affected the size of the splenic structures. The size of follicles and germinal centers decreased significantly in tumor-bearing rats compared to tumor-free rats. This effect was changed in rats fed the orange-pulp diet. In tumor-bearing rats from this group, only the area of the marginal zone decreased and the red pulp increased compared to tumor-free rats. The size of germinal centers significantly increased compared to tumor-bearing rats in controls. The total number of lymphoid cells decreased in germinal centers of spleens obtained from control tumor-bearing rats compared to tumor-free rats. DMH alone significantly increased the total number of cells in the colon mucosa of the rats fed the control diet. In tumor-bearing rats exposed to the carcinogen and fed the 15% orange-pulp diet, the total number of cells and the number of Ki-67+ cells increased in the depth of tumors whereas the number of CD8+ T cells increased in the colon mucosa, at the border of tumors and its depth. The caspase-3 protein a cysteine protease was elevated in tumors from rats fed the orange-pulp diet. Although the 15% orange-pulp diet did not change the number of tumors in the tumor-bearing rats, feeding rats orange pulp significantly decreased the number of endophytic tumors and increased the number of exophytic tumors. Increased activity of T cell killers in tumors and higher level of proteins involved with apoptosis following consumption of the orange pulp indicate a clear tumor suppressor effect of these dietary fibers.
Kossoy
G
G
Department of Obstetrics and Gynecology, Kaplan Medical Center, Rehovot, Israel.
Ben-Hur
H
H
Stark
A
A
Zusman
I
I
Madar
Z
Z
D000230:Adenocarcinoma / Q000276:immunology / Q000473:pathology / Q000517:prevention & control; D000818:Animals; D016588:Anticarcinogenic Agents / Q000494:pharmacology*; D017209:Apoptosis; D053148:Caspase 3; D020169:Caspases; D002957:Citrus; D003110:Colonic Neoplasms / Q000276:immunology / Q000473:pathology / Q000517:prevention & control*; D019587:Dietary Supplements; D005638:Fruit; D007413:Intestinal Mucosa / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D013601:T-Lymphocytes
D016588:Anticarcinogenic Agents; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases