title: H-RAS V12-induced radioresistance in HCT116 colon carcinoma cells is heregulin dependent.
abstract: The abilities of mutated active K-RAS and H-RAS proteins, in an isogenic human carcinoma cell system, to modulate the activity of signaling pathways following exposure to ionizing radiation is unknown. Loss of K-RAS D13 expression in HCT116 colorectal carcinoma cells blunted basal extracellular signal-regulated kinase 1/2 (ERK1/2), AKT, and c-Jun NH2-terminal kinase 1/2 activity. Deletion of the allele to express K-RAS D13 also enhanced expression of ERBB1, ERBB3, and heregulin but nearly abolished radiation-induced activation of all signaling pathways. Expression of H-RAS V12 in HCT116 cells lacking an activated RAS molecule (H-RAS V12 cells) restored basal ERK1/2 and AKT activity to that observed in parental cells but did not restore or alter basal c-jun NH2-terminal kinase 1/2 activity. In parental cells, radiation caused stronger ERK1/2 pathway activation compared with that of the phosphatidylinositol 3-kinase (PI3K)/AKT pathway, which correlated with constitutive translocation of Raf-1 into the plasma membrane of parental cells. Inhibition of mitogen-activated protein kinase/ERK1/2, but not PI3K, radiosensitized parental cells. In H-RAS V12 cells, radiation caused stronger PI3K/AKT pathway activation compared with that of the ERK1/2 pathway, which correlated with H-RAS V12-dependent translocation of PI3K into the plasma membrane. Inhibition of PI3K, but not mitogen-activated protein kinase/ERK1/2, radiosensitized H-RAS V12 cells. Radiation-induced activation of the PI3K/AKT pathway in H-RAS V12 cells 2 to 24 hours after exposure was dependent on heregulin-stimulated ERBB3 association with membrane-localized PI3K. Neutralization of heregulin function abolished radiation-induced AKT activation and reverted the radiosensitivity of H-RAS V12 cells to those levels found in cells lacking expression of any active RAS protein. These findings show that H-RAS V12 and K-RAS D13 differentially regulate radiation-induced signaling pathway function. In HCT116 cells expressing H-RAS V12, PI3K-dependent radioresistance is mediated by both H-RAS-dependent translocation of PI3K into the plasma membrane and heregulin-induced activation of membrane-localized PI3K via ERBB3.
authors.affiliation: Department of Radiation Oncology, Medical College of Virginia, Virginia Commonwealth University, 401 College Street, Richmond, VA 23298-0058, USA. pdent@hsc.vcu.edu
authors.forename: Rubén W
authors.initials: RW
authors.lastname: Carón
authors.forename: Adly
authors.initials: A
authors.lastname: Yacoub
authors.forename: Xiaoyu
authors.initials: X
authors.lastname: Zhu
authors.forename: Clint
authors.initials: C
authors.lastname: Mitchell
authors.forename: Song Iy
authors.initials: SI
authors.lastname: Han
authors.forename: Takehiko
authors.initials: T
authors.lastname: Sasazuki
authors.forename: Senji
authors.initials: S
authors.lastname: Shirasawa
authors.forename: Michael P
authors.initials: MP
authors.lastname: Hagan
authors.forename: Steven
authors.initials: S
authors.lastname: Grant
authors.forename: Paul
authors.initials: P
authors.lastname: Dent
mesh_terms: D000906:Antibodies / Q000494:pharmacology; D017209:Apoptosis; D002277:Carcinoma / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000737:chemistry; D003110:Colonic Neoplasms / Q000235:genetics / Q000378:metabolism*; D066246:ErbB Receptors / Q000378:metabolism; D017353:Gene Deletion; D006801:Humans; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D020890:Neuregulin-1 / Q000037:antagonists & inhibitors / Q000276:immunology / Q000502:physiology*; D019869:Phosphatidylinositol 3-Kinases / Q000032:analysis / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000032:analysis / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000032:analysis / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D011836:Radiation Tolerance / Q000235:genetics / Q000502:physiology*; D020893:Receptor, ErbB-3 / Q000502:physiology*; D018631:ras Proteins / Q000235:genetics / Q000502:physiology*
chemical_list: D000906:Antibodies; D066246:ErbB Receptors; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020890:Neuregulin-1; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D020893:Receptor, ErbB-3; D018631:ras Proteins; C494918:AKT1 protein, human