Activation of NF-kappaB is required for PDGF-B chain to transform NIH3T3 cells

Elucidating the secondary signaling molecules that are necessary for platelet-derived growth factor (PDGF) to stimulate tumor development will be crucial to the understanding and treatment of a variety of cancers. Several lines of evidence have indicated that the transcription factor NF-kappaB plays a central role in transformation induced by Ha-ras and Bcr-abl, but nothing is known concerning its role in transformation by PDGF. Here we demonstrate that transcription from a promoter containing NF-kappaB binding sequences as well as the DNA binding activity of NF-kappaB were increased in PDGF-B-chain-transformed mouse fibroblast cells. Focus formation of PDGF-B-chain-transformed mouse fibroblasts was suppressed by treatment with acetylsalicylic acid (ASA) and salicylic acid, which are known inhibitors of NF-kappaB activation, but other nonsteroidal anti-inflammatory drugs that do not have an effect on NF-kappaB activity did not affect focus formation in these cells. Furthermore, expression of a dominant negative mutant of IkappaBalpha, pMEIkappaBalpha67CJ, and a dominant negative mutant of p65, p65DeltaC, resulted in decreased focus formation and NF-kappaB activity. Therefore, the transcription factor NF-kappaB plays a vital role in PDGF-B chain transformation of mouse fibroblast cells, and the NF-kappaB activity is sensitive to treatment with ASA.