title: Blockade of irradiation-induced autophagosome formation impairs proliferation             but does not enhance cell death in HCT-116 human colorectal carcinoma cells.
abstract: This work was undertaken to gain further information on the molecular mechanisms             underlying autophagosome formation and its relation with tumor cell survival in             response to radiation in colon cancer. A human colon cancer cell line, HCT-116,             was examined with respect to cell survival after blockade of irradiation-induced             autophagosome formation by pharmacological interference. Autophagosome formation             was confirmed using a kinetic study with incorporated bovine serum albumin gold-conjugate             (BSA-Au) analyzed by electron microscopy and an autophagosome-associated LC3B             antibody measured by immunofluorescence and Western blotting. Annexin V/PI double             staining was used to monitor cell death by apoptosis, and cell cycle profiles             by flow cytometry. Ionizing radiation (IR) promoted autophagosome formation in             the HCT-116 IR-surviving cells. Pharmacological interference showed that PI3K/Akt             and Src were involved in early stages of autophagosome formation. IR alone decreased             cell proliferation by arresting cells in the G2/M phase, and pharmacological interference             of autophagosome formation decreased proliferation, but did not affect cell survival.             Also, our data suggest that decreased proliferation caused by PI3K and Src inhibitors             could be through S phase cell cycle delay. Our results clearly indicate that blockade             of IR-induced autophagosome formation impairs proliferation but does not enhance             cell death in colon cancer cells.
authors.affiliation: Division of Cellular Biology, Jose Alencar National Cancer Institute, Rio de Janeiro, Brazil.
authors.forename: Ana Cristina
authors.initials: AC
authors.lastname: de Albuquerque-Xavier
authors.forename: Lilian Gonçalves R
authors.initials: LG
authors.lastname: Bastos
authors.forename: Julio Cesar Madureira
authors.initials: JC
authors.lastname: de Freitas
authors.forename: Fernanda
authors.initials: F
authors.lastname: Leve
authors.forename: Waldemir Fernández
authors.initials: WF
authors.lastname: de Souza
authors.forename: Wallace Martins
authors.initials: WM
authors.lastname: de Araujo
authors.forename: João Luiz Mendes
authors.initials: JL
authors.lastname: Wanderley
authors.forename: Marcelo Neves
authors.initials: MN
authors.lastname: Tanaka
authors.forename: Wanderley
authors.initials: W
authors.lastname: de Souza
authors.forename: José Andrés
authors.initials: JA
authors.lastname: Morgado-Díaz
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000528:radiation effects; D001343:Autophagy / Q000528:radiation effects*; D002417:Cattle; D048708:Cell Growth Processes / Q000528:radiation effects; D045744:Cell Line, Tumor; D015179:Colorectal Neoplasms / Q000473:pathology* / Q000532:radiotherapy*; D045325:HCT116 Cells; D006801:Humans