title: Inhibition of RalA signaling pathway in treatment of non-small cell lung cancer.
abstract: Non-small cell lung cancer (NSCLC) is the most common type of lung cancer and relatively resistant to chemotherapy. The most prevalent molecular abnormality in NSCLC is the overactivation of K-Ras proto-oncogene; therefore, elucidating down-stream Ras signaling in NSCLC is significantly important in developing novel therapies against this malignancy. Our work indicates that RalA, an important effector of Ras, is activated in NSCLC cell lines. While RalA was also overactivated in fetal human broncho-epithelial cells, RalBP1 (Ral binding protein-1), an important down-stream effector of RalA, was expressed at higher levels in cancer cell lines. Aurora kinase-A (AKA), an upstream activator of RalA, was also found to be active only in malignant cells. The outcome of inhibition of RalA (by gene specific silencing using a lentivirus) on the malignant phenotype of A549 cells was also studied. While proliferation and invasiveness of A549 cells were reduced upon silencing RalA, apoptosis and necrosis were elevated in such conditions. Additionally, the in vivo tumorigenesis of A549 cells was reduced upon partial inhibition of RalA and AKA using pharmacological inhibitors. Finally, we were interested in evaluating the level of active RalA in the fraction of NSCLC cells expressing cancer stem cell markers. For this purpose cells with increased expression of CD44 were separated from A549 cells and compared with cells with low level of expression of this marker and an unsorted population. A significant enhancement of RalA activation in high CD44+ cells was found as potential evidence for involvement of RalA signaling in initiation of the neoplastic procedure and an important contributor for tumor maintenance in NSCLC. Further studies can reveal therapeutic, preventive and diagnostic value of RalA pathway in this deadly disease.
authors.affiliation: The University of Kansas Medical Center, Department of Medicine - Divisions of Hematology/Oncology & Gastroenterology, Molecular Medicine Laboratory, Kansas City, KS, USA.
authors.forename: Heather
authors.initials: H
authors.lastname: Male
authors.forename: Vijay
authors.initials: V
authors.lastname: Patel
authors.forename: Mark A
authors.initials: MA
authors.lastname: Jacob
authors.forename: Emma
authors.initials: E
authors.lastname: Borrego-Diaz
authors.forename: Kun
authors.initials: K
authors.lastname: Wang
authors.forename: Derek A
authors.initials: DA
authors.lastname: Young
authors.forename: Amanda L
authors.initials: AL
authors.lastname: Wise
authors.forename: Chao
authors.initials: C
authors.lastname: Huang
authors.forename: Peter
authors.initials: P
authors.lastname: Van Veldhuizen
authors.forename: Amy
authors.initials: A
authors.lastname: O'Brien-Ladner
authors.forename: Stephen K
authors.initials: SK
authors.lastname: Williamson
authors.forename: Sarah A
authors.initials: SA
authors.lastname: Taylor
authors.forename: Ossama
authors.initials: O
authors.lastname: Tawfik
authors.forename: Tuba
authors.initials: T
authors.lastname: Esfandyari
authors.forename: Faris
authors.initials: F
authors.lastname: Farassati
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000235:genetics; D002289:Carcinoma, Non-Small-Cell Lung / Q000235:genetics / Q000378:metabolism* / Q000628:therapy; D045744:Cell Line, Tumor; D015972:Gene Expression Regulation, Neoplastic; D020868:Gene Silencing; D006801:Humans; D018960:Hyaluronan Receptors / Q000378:metabolism; D008175:Lung Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000628:therapy; D051379:Mice; D008819:Mice, Nude; D014411:Neoplastic Stem Cells / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000008:administration & dosage / Q000494:pharmacology; D000090063:Proto-Oncogene Mas; D034622:RNA Interference; D015398:Signal Transduction; D023041:Xenograft Model Antitumor Assays; D020725:ral GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D018960:Hyaluronan Receptors; C000715470:MAS1 protein, human; D047428:Protein Kinase Inhibitors; D000090063:Proto-Oncogene Mas; C492198:RALA protein, human; D020725:ral GTP-Binding Proteins