Cellular and molecular characterization of a feline insulinoma.
BACKGROUND
Insulinoma is an autonomous insulin-secreting islet cell neoplasm that is rarely diagnosed in cats. The clinical and pathological aspects of feline insulinoma have been described previously, but the molecular characteristics of these tumors have not been investigated.


OBJECTIVE
The study objectives were to characterize peptide hormone production and determine expression of selected genes involved in glucose metabolism and insulin secretion in a feline insulinoma.


METHODS
Immunohistochemistry and RT-PCR were used to examine hormone and gene expression, respectively, by insulinoma cells.


RESULTS
Immunohistochemistry examination indicated that the tumor cells expressed insulin, chromogranin A, and somatostatin but not glucagon or pancreatic polypeptide. The tumor expressed several genes characteristic of pancreatic beta cells (beta cells) including insulin (INS), glucose transporter 2 (GLUT2), and glucokinase (GCK). The tumor also expressed hexokinase 1 (HK1), a glycolytic enzyme not normally expressed in beta cells. GCK expression was higher in the insulinoma than in normal pancreas from the same cat. The GCK : HK1 ratio was >20-fold higher in insulinoma tissue than in normal pancreas.


CONCLUSIONS
The feline insulinoma produced several peptide hormones and expressed genes consistent with a beta-cell phenotype. The pattern of hexokinase gene expression in tumor cells differed from that of normal pancreas. These findings suggest insulinoma cells may have an increased sensitivity to glucose that could contribute to the abnormal insulin secretory response observed at low serum glucose concentrations.
Jackson
T C
TC
Department of Clinical Sciences, College of Veterinary Medicine, Kansas State University, 1800 Denison Avenue, Manhattan, KS 66506-5606, USA.
Debey
B
B
Lindbloom-Hawley
S
S
Jones
B T
BT
Schermerhorn
T
T
D000818:Animals; D002371:Cat Diseases / Q000235:genetics* / Q000378:metabolism; D002415:Cats; D004273:DNA, Neoplasm / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D005941:Glucokinase / Q000096:biosynthesis / Q000235:genetics; D051273:Glucose Transporter Type 2 / Q000096:biosynthesis / Q000235:genetics; D006593:Hexokinase / Q000096:biosynthesis / Q000235:genetics; D007150:Immunohistochemistry / Q000662:veterinary; D007328:Insulin / Q000096:biosynthesis / Q000235:genetics; D050417:Insulin-Secreting Cells / Q000378:metabolism; D007340:Insulinoma / Q000235:genetics / Q000378:metabolism / Q000662:veterinary*; D010190:Pancreatic Neoplasms / Q000235:genetics / Q000378:metabolism / Q000662:veterinary*; D016133:Polymerase Chain Reaction / Q000662:veterinary
D004273:DNA, Neoplasm; D051273:Glucose Transporter Type 2; D007328:Insulin; D006593:Hexokinase; D005941:Glucokinase