Absence of p53 gene expression in selenium molecular prevention of chemically induced hepatocarcinogenesis in rats

Abstract

Background/aim: p53 pathway is thought by many researchers to be critically involved in selenium's chemoprevention or in hepatocarcinogenesis. The aim of this study was to investigate the gene expression of p53, p21 and B-cell lymphoma-2 (bcl-2) using preventive and therapeutic approaches of selenium in chemically induced hepatocarcinogenesis in rats.

Materials and methods: Rats were divided randomly into six groups: Negative control, positive control (diethyl nitrosamine +2-acetylaminofluorene), preventive group, preventive control (respective control for preventive group), therapeutic group and therapeutic control (respective control for therapeutic group). p53, p21 and bcl-2 genes on liver tissues were measured using real-time polymerase chain reaction.

Results: The expression of p53 was only significant in the therapeutic control. The expression of bcl-2 was insignificant in all the groups. p21 expression was significant in all the groups except the preventive group.

Conclusions: The selenium molecular mechanism for liver cancer prevention is not through the p53 pathway. Also, the absence of p53 is not necessary for chemically induced liver cancer in rats.

Figure 1

Neoplastic liver showing enlarged nuclei with prominent nucleoli, as seen in the positive control (received a single IP injection of DEN at a dose of 200 mg/kg body weight in saline and 2 weeks later, the carcinogen effect was promoted by 2-AAF (0.02%) and continued for 10 weeks). Hematoxylin and eosin (×20)

Figure 2

Hyperplastic liver with largely preserved architecture as seen in the preventive group (received sodium selenite which was stopped at week 4, the day of commencement of DEN administration as in group 2) and the therapeutic group (received a single IP injection of DEN as in group 2, and 4 weeks later, rats were treated with sodium selenite for 8 weeks). Hematoxylin and eosin (×20)

Figure 3

Normal liver architecture as seen in the negative (received normal rat chow and drinking water), preventive (treated with sodium selenite alone for 4 weeks and served as control for group 3) and therapeutic controls (treated with sodium selenite alone for 8 weeks and served as control for group 5). Hematoxylin and eosin (×20)

Figure 4

Relative expression of p53 in all experimental groups, using RT-PCR. Group 1 received rat chow and drinking water. Group 2 received a single IP injection of DEN at a dose of 200 mg/kg body weight in saline, and 2 weeks later, the carcinogen effect was promoted by administering 2-AAF (0.02%) which was continued for 10 weeks. Group 3 received sodium selenite (4 mg/l in drinking water) which was stopped at week 4 (the day of commencement of DEN administration as in group 2). Group 4 rats were treated with sodium selenite alone for 4 weeks (served as control for group 3). Group 5 received a single IP injection of DEN as in group 2, and 4 weeks later, rats were treated with sodium selenite (4 mg/l in drinking water) for 8 weeks. Group 6 rats were treated with sodium selenite alone for 8 weeks (served as control for group 5). Results are expressed as means ± SD. Values were analyzed using Student's t and Mann–Whitney's U tests

Figure 5

Relative expression of bcl-2 in all experimental groups using RT-PCR. Group 1 received rat chow and drinking water. Group 2 received a single IP injection of DEN at a dose of 200 mg/kg body weight in saline, and 2 weeks later, the carcinogen effect was promoted by administering 2-AAF (0.02%) which was continued for 10 weeks. Group 3 received sodium selenite (4 mg/l in drinking water) which was stopped at week 4 (the day of commencement of DEN administration as in group 2). Group 4 rats were treated with sodium selenite alone for 4 weeks (served as control for group 3). Group 5 received a single IP injection of DEN as in group 2, and 4 weeks later, the rats were treated with sodium selenite (4 mg/l in drinking water) for 8 weeks. Group 6 rats were treated with sodium selenite alone for 8 weeks (served as control for group 5). Results are expressed as means ± SD. Values were analyzed using Student's t and Mann–Whitney's U tests

Figure 6

Relative expression of p21 in all experimental groups using RT-PCR. Group 1 received rat chow and drinking water. Group 2 received a single IP injection of DEN at a dose of 200 mg/kg body weight in saline, and 2 weeks later, the carcinogen effect was promoted by administering 2-AAF (0.02%) which was continued for 10 weeks. Group 3 received sodium selenite (4 mg/l in drinking water) which was stopped at week 4 (the day of commencement of DEN administration as in group 2). Group 4 rats were treated with sodium selenite alone for 4 weeks (served as control for group 3). Group 5 received a single IP injection of DEN as in group 2, and 4 weeks later, the rats were treated with sodium selenite (4 mg/l in drinking water) for 8 weeks. Group 6 rats were treated with sodium selenite alone for 8 weeks (served as control for group 5). Results are expressed as means ± SD. Values were analyzed using Student's t and Mann–Whitney's U tests