title: Signaling crosstalk of FHIT, CHK2 and p38 in etoposide induced growth inhibition in MCF-7 cells.
abstract: FHIT (Fragile Histidin Triad) is a tumor suppressor gene involved in regulating cell death during DNA damage conditions. The exact mechanism of DNA damage-induced FHIT signaling is not well understood. It is known that p38 kinase and CHK2 kinase are being activated during stress-induced conditions and DNA damage, resulting in cell death. Since both CHK2 and FHIT are being influenced by DNA damage, we have evaluated the interplay of p38, CHK2 and FHIT in response to etoposide-induced cell death. DNA damage was induced by etoposide in MCF-7 cells and viability was examined using MTT. FHIT expression was blocked using siRNA. Protein expression was measured using western blotting. Our results indicated that etoposide induced cytotoxicity in MCF-7. Block of FHIT expression, completely reversed etoposide cytotoxicity. Besides, etoposide induced p38 and CHK2 phosphorylation and reduced FHIT expression in a time-dependent manner. The time-course study indicated that CHK2 had been phosphorylated prior to p38 activation. Knockdown of FHIT expression reduced CHK2 phosphorylation but had no significant effect on p38 activation. Inhibition of p38 kinase and CHK2 prevented etoposide induced alteration in FHIT expression. Furthermore, p38 inhibitors augmented etoposide-induced CHK2 phosphorylation. These results indicate that etoposide lowers FHIT expression and induces cell death via p38 and CHK2 phosphorylation. These results demonstrate a time dependent complex crosstalk of FHIT, p38 and CHK2 pathways in response to etoposide. Moreover, our findings suggest signaling interaction for these pathways which can be targeted for manipulating cell proliferation.
authors.affiliation: Department of Biology, Faculty of Science, Tarbiat moalem University of Tehran, Tehran, Iran.
authors.forename: Fereshteh
authors.initials: F
authors.lastname: Mir Mohammadrezaei
authors.forename: Homa
authors.initials: H
authors.lastname: Mohseni kouchesfehani
authors.forename: Hamed
authors.initials: H
authors.lastname: Montazeri
authors.forename: Mehdi
authors.initials: M
authors.lastname: Gharghabi
authors.forename: Seyed Nasser
authors.initials: SN
authors.lastname: Ostad
authors.forename: Mohammad Hossein
authors.initials: MH
authors.lastname: Ghahremani
mesh_terms: D017766:Acid Anhydride Hydrolases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D049109:Cell Proliferation / Q000187:drug effects*; D064447:Checkpoint Kinase 2; D004249:DNA Damage; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005047:Etoposide / Q000494:pharmacology*; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D061986:MCF-7 Cells; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011725:Pyridines / Q000494:pharmacology; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D015398:Signal Transduction; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000099170:Bis(5'-adenosyl)triphosphatase
chemical_list: D017766:Acid Anhydride Hydrolases; D000972:Antineoplastic Agents, Phytogenic; D064447:Checkpoint Kinase 2; D004791:Enzyme Inhibitors; D005047:Etoposide; D007093:Imidazoles; D009363:Neoplasm Proteins; D017346:Protein Serine-Threonine Kinases; D011725:Pyridines; D034741:RNA, Small Interfering; D048051:p38 Mitogen-Activated Protein Kinases; D000099170:Bis(5'-adenosyl)triphosphatase; C578634:CHEK2 protein, human; C090942:4-(4-fluorophenyl)-2-(4-hydroxyphenyl)-5-(4-pyridyl)imidazole