BMP-induced growth suppression in colon cancer cells is mediated by p21WAF1 stabilization and modulated by RAS/ERK.
Bone morphogenetic proteins (BMPs) regulate cell differentiation, proliferation, and apoptosis through a canonical SMAD signaling cascade. Absence of BMP signaling causes the formation of intestinal juvenile polyps in the colon cancer-prone syndrome familial juvenile polyposis. As sporadic colon cancers appear to have intact BMP signaling, we evaluated if K-RAS, driving a mitogenic pathway frequently activated in colon cancer, negatively affects BMP growth suppression. We treated non-tumorigenic but activated RAS/ERK FET cells with BMP2, and in combination with pharmacological or genetic inhibition of RAS/ERK, examined BMP-SMAD signaling, transcriptional activity, and cell growth, and also assessed p21(WAF1) mRNA, transcriptional activation, and protein levels. BMP2 increased nuclear phospho-SMAD1 2-fold, which increased another 2-3 fold when RAS/ERK was inhibited. BMP2 increased BMP-specific SMAD transcriptional activity 2-fold over control and decreased cell growth, but inhibition of RAS/ERK further enhanced BMP-specific transcriptional activity by an additional 1.5-2 fold and enhanced growth suppression by 20%. BMP-induced growth suppression is mediated in part by p21(WAF1), not by transcriptional upregulation but by improved p21 protein stability, which is inhibited by RAS/ERK. In colon cancer cells, BMP-SMAD signaling and growth suppression is facilitated by p21(WAF1) but modulated by oncogenic K-RAS to reduce the growth suppression directed by this pathway.
Beck
Stayce E
SE
Department of Medicine, Division of Gastroenterology, University of California-San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA.
Jung
Barbara H
BH
Del Rosario
Eunice
E
Gomez
Jessica
J
Carethers
John M
JM
D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000494:pharmacology*; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D003110:Colonic Neoplasms / Q000473:pathology*; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects; D051059:PTEN Phosphohydrolase / Q000235:genetics / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D051785:Smad Proteins / Q000378:metabolism; D013816:Thermodynamics; D014158:Transcription, Genetic / Q000187:drug effects; D015533:Transcriptional Activation / Q000187:drug effects; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D018631:ras Proteins / Q000378:metabolism*
D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; D047428:Protein Kinase Inhibitors; D012333:RNA, Messenger; D051785:Smad Proteins; D016212:Transforming Growth Factor beta; D048049:Extracellular Signal-Regulated MAP Kinases; D051059:PTEN Phosphohydrolase; D018631:ras Proteins