Insulin-like growth factors induce apoptosis as well as proliferation in LIM 1215 colon cancer cells.
The insulin-like growth factor (IGF) system plays an important role in cell proliferation and survival. However, more recently, a small number of studies have shown that IGFs induce apoptosis in some cells. Our initial studies showed this occurred in LIM 1215 colon cancer cells but not RD rhabdomyosarcoma cells. IGFs induced both proliferation and apoptosis in LIM 1215 cells, and the induction of apoptosis was dose-dependent. [R54, R55]IGF-II, which binds to the IGF-I receptor with normal affinity but does not bind to the IGF-II receptor, induced apoptosis to the same extent as IGF-II, whereas [L27]IGF-II, which binds to the IGF-I receptor with 1000-fold reduced affinity, had no effect on apoptosis. These results suggest that the IGF-I receptor is involved in induction of apoptosis. Western blot analyses demonstrated that Akt and Erk1/2 were constitutively activated in RD cells. In contrast, phosphorylation of Akt and Erk1/2 were transient and basal expression of Akt protein was lower in LIM 1215 cells. Analysis of apoptosis-related proteins showed that IGFs decreased pro-caspase-3 levels and increased expression of pro-apoptotic Bad in LIM 1215 cells. IGFs co-activate proliferative and apoptotic pathways in LIM 1215 cells, which may contribute to increased cell turnover. Since high turnover correlates with poor prognosis in colorectal cancer, this study provides further evidence for the role of the IGF system in its progression.
Fu
Ping
P
Department of Medicine, Central & Eastern Clinical School, Alfred Hospital, Monash University, Prahran VIC 3181, Australia.
Thompson
Julian A
JA
Leeding
Kerri S
KS
Bach
Leon A
LA
D017209:Apoptosis; D053148:Caspase 3 / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D003110:Colonic Neoplasms / Q000378:metabolism* / Q000473:pathology; D053938:DNA Fragmentation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000502:physiology*; D007335:Insulin-Like Growth Factor II / Q000502:physiology*; D051058:Oncogene Protein v-akt / Q000378:metabolism; D010766:Phosphorylation; D017526:Receptor, IGF Type 1 / Q000378:metabolism; D012208:Rhabdomyosarcoma / Q000378:metabolism / Q000473:pathology; D015398:Signal Transduction; D051025:bcl-Associated Death Protein / Q000378:metabolism
C494819:BAD protein, human; D051025:bcl-Associated Death Protein; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D017526:Receptor, IGF Type 1; D051058:Oncogene Protein v-akt; D048049:Extracellular Signal-Regulated MAP Kinases; D053148:Caspase 3