Transforming growth factor-α and epidermal growth factor expression in the exocrine pancreas of azaserine-treated rats: modulation by cholecystokinin or a low fat, high fiber (caloric restricted) diet

Abstract

Expression of transforming growth factor-alpha (TGF-alpha) and epidermal growth factor (EGF) was studied in normal pancreatic tissue and in (pre)neoplastic pancreatic lesions of azaserine-treated rats. They were given either a low fat, high fiber (low caloric) diet, to inhibit carcinogenesis, or a low fat diet combined with injections of the cholecystokinin analog caerulein to enhance carcinogenesis. The control groups, maintained on a low fat diet, were injected with azaserine or were not treated at all. Autopsy was performed at 6 and 15 months after the last azaserine injection. After both 6 and 15 months immunohistochemistry revealed a weak expression of EGF and TGF-alpha peptides in the acinar cells, and a stronger expression in the ductular and centroacinar cells. TGF-alpha peptide expression was reduced in both putative preneoplastic and neoplastic acinar cell lesions, but no differences in EGF peptide expression were observed between the various stages of exocrine pancreatic carcinogenesis. After 16 months an increase in TGF-alpha mRNA due to treatment with azaserine was detected by semi-quantitative PCR in total pancreatic homogenates, whereas EGF mRNA expression had decreased. TGF-alpha mRNA levels in macroscopically isolated tumors were significantly lower, but EGF mRNA levels were significantly higher, than in total pancreatic homogenates from azaserine-treated rats. Furthermore, EGF and TGF-alpha mRNA levels in isolated tumors did not differ significantly from mRNA levels in non-carcinogen-treated rats. Neither with immunohistochemistry nor with PCR were differences in EGF or TGF-alpha expression observed due to either inhibition or stimulation of carcinogenesis. It is concluded that putative preneoplastic acinar cell lesions induced in rat pancreas by azaserine may develop into acinar adenocarcinomas independently of TGF-alpha and EGF. The results suggest involvement of these growth factors at the early stage of the carcinogenic process, during the initiation of normal acinar cells into putative preneoplastic cells. However, modulation of azaserine-induced pancreatic carcinogenesis by cholecystokinin or a low fat, high fiber (caloric restricted) diet appeared not to be regulated by EGF or TGF-alpha.

Dietary restriction reduces hepatocyte proliferation and enhances p53 expression but does not increase apoptosis in normal rats during development

“…Based on the published nucleotide sequence of cDNA encoding rat β-actin (Nudel et al 1983) and p53 (Soussi et al 1988), the following primers were designed using a software package (Oligo 4.0, National Bioscience Inc.): (a) primer for rat β-actin: (forward 1): 5'-CGT TGA CAT CCG TAA AGA CC-3', (forward 2): 5'-CAC TGC CGC ATC CTC TTC CT-3', (reverse): 5'-AGC CAC CAA TCC ACA CAG AG-3' (PCR product size 173 bp and 347 bp, respectively); (b) primer for rat p53' (forward): 5'-TCC TCC CCA ACA TCT TAT CC-3', (reverse): 5'-GCA CAA ACA CGA ACC TCA AA-3' (PCR product size 261 bp), primers for rat histone H3.3 (Kelly et al 1993), TGFα (Visser et al 1995), TGFβ1 (Gao et al 1996), Fas (Higami et al 1997b) and TNFr (Krown et al 1995) were published oligonucleotide sequences. The sizes of PCR products for rat histone H3.3, TGFα, TGFβ1, Fas and TNFr were 213, 266, 395, 141 and 288 bp, respectively.…”

Pancreatic cancer in rats and hamsters does not induce IAPP-related hyperglycaemia

“…In 10 128 6 7 2.5 6 0.2 1.0 6 0.3 0.1 6 0.1 BOP 1 cae 10 129 6 5 2.7 6 0.2 3.3 6 0.5 0.0 6 0.0 ‡ ‡ ‡ BOP 1 HF 10 133 6 6 2.6 6 0.3 2.6 6 0.3 0.2 6 0.2 ‡ ‡ 12 months post-treatment Con 5 143 6 4 3.2 6 0.3 0.0 6 0.0 0.0 6 0.0 * BOP 9 152 6 4 2.9 6 0.5 3.0 6 0.8 0.0 6 0.0 * BOP 1 cae 9 164 6 7 3.1 6 0.3 3.2 6 0.9 0.3 6 0.2 ***/ † BOP 1 HF 10 175 6 4 2.2 6 0.2 3.2 6 0.3 0.3 6 0.2 ***/ † † †/ ‡ ‡ earlier reports by our group, food intake, body and pancreas weight, and the nature, number and volumetric analysis of (pre-) neoplastic lesions were presented in relation to the levels of growth factors in the lesions (Visser et al, 1995(Visser et al, , 1996. In this study we examined the influence of exocrine pancreatic carcinogenesis on blood-glucose homeostasis.…”

“…All animals were given standard laboratory chow until one week after the last injection. From that time onwards, AIN-76-based diets were provided (Visser et al, 1995(Visser et al, , 1996. All carcinogen-treated animals were assigned randomly to one of the following experimental sub-groups: regular diet (5% corn oil); regular diet plus s.c. injections of 2.5 µg/kg body weight caerulein, 3 times a week, or high-fat diet (20% corn oil), in isocaloric (rat) or non-isocaloric (hamster) form (Birt et al, 1989).…”

“…Investigating both animal models might reveal differential effects of pancreatic lesion histology. To promote carcinogenesis, carcinogen-treated rat and hamster sub-groups were additionally treated with the cholecystokinin(CCK) analogue caerulein (Howatson and Carter, 1985;Visser et al, 1995) or were given a high-fat diet (Birt et al, 1989). Animals were examined at 6 and 12/15 (hamster/rat) months after the last carcinogen injection.…”

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“…In one report, strong TGFα immunoreactivity was found in 95% of pancreatic tumors, whereas EGF immunoreactivity was observed in only 12% of the tumors [ 17 ]. Similarly, carcinogen-induced pancreatic cancer in the hamster and rat expressed only TGFα and EGFR, but not EGF [ 18 , 19 ]. Data from these human and animal studies are in line with a generally accepted notion that TGFα is the preferred trophic factor over other EGFR ligands for normal ductal cells and cancer cells in the pancreas [ 20 - 23 ].…”