Enhanced expression of the insulin receptor substrate-2 docking protein in human pancreatic cancer.
Insulin receptor substrate-2 (IRS-2) is a multisite docking protein implicated in mitogenic signaling after activation of the insulin and insulin-like growth factor (IGF)-I receptors. In the present study, we characterized IRS-2 expression and function in human pancreatic cancer. IRS-2 mRNA and protein were expressed in ASPC-1 and COLO-357 human pancreatic cancer cell lines. Insulin, IGF-I, and IGF-II enhanced the growth of both cell lines, stimulated tyrosine phosphorylation of IRS-2, and increased IRS-2-associated phosphatidylinositol (PI) 3-kinase activity. The mitogenic effects of insulin, IGF-I, and IGF-II were markedly attenuated by the PI 3-kinase inhibitor LY 294002. Northern blot analysis of total RNA extracted from normal and cancerous tissues revealed that IRS-2 mRNA levels were increased in the cancer tissues (P = 0.032). In the normal pancreas, IRS-2 immunoreactivity was present at low levels in some ductal and acinar cells and at moderate levels in a heterogeneous pattern in all of the endocrine islets. In the pancreatic cancers, IRS-2 was abundant in the ductal-like cancer cells. These findings indicate that IRS-2 is overexpressed in human pancreatic cancer and suggest that it may contribute to enhanced mitogenic signaling via the PI 3-kinase pathway, thereby leading to excessive growth stimulation in this malignancy.
Kornmann
M
M
Department of Medicine, University of California, Irvine 92697, USA.
Maruyama
H
H
Bergmann
U
U
Tangvoranuntakul
P
P
Beger
H G
HG
White
M F
MF
Korc
M
M
D003110:Colonic Neoplasms; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects / Q000502:physiology*; D006133:Growth Substances / Q000494:pharmacology* / Q000502:physiology; D006801:Humans; D007328:Insulin / Q000494:pharmacology; D055504:Insulin Receptor Substrate Proteins; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D007335:Insulin-Like Growth Factor II / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins; D010179:Pancreas / Q000166:cytology / Q000378:metabolism*; D010190:Pancreatic Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010750:Phosphoproteins / Q000096:biosynthesis / Q000235:genetics*; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000096:biosynthesis; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured
D006133:Growth Substances; C526297:IRS2 protein, human; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; D047908:Intracellular Signaling Peptides and Proteins; D010750:Phosphoproteins; D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D019869:Phosphatidylinositol 3-Kinases