title: Purvalanol induces endoplasmic reticulum stress-mediated apoptosis and autophagy in a time-dependent manner in HCT116 colon cancer cells.
abstract: Purvalanol, a novel cyclin-dependent kinase inhibitor, is referred to as a strong apoptotic inducer which causes cell cycle arrest in various cancer cells such as prostate, breast and colon cancer cell lines. Various physiological and pathological conditions such as glucose starvation, inhibition of protein glycosylation and oxidative stress may cause an accumulation of unfolded proteins in the endoplasmic reticulum (ER), leading to the unfolded protein response (UPR) and autophagy. Lacking proteosomal function on aggregates of unfolded proteins, ER stress may induce autophagic machinery. Autophagy, an evolutionarily conserved process, is characterized by massive degradation of cytosolic contents. In the present study, our aim was to determine the time-dependent, ER-mediated apoptotic and autophagy induction of purvalanol in HCT 116 colon cancer cells. Fifteen micromoles of purvalanol induced a reduction in cell viability by 20 and 35% within 24 and 48 h, respectively. HCT 116 colon cancer cells were exposed to purvalanol, which activated ER stress via upregulation of PERK, IRE1α gene expression, eIF-2α phosphorylation and ATF-6 cleavage at early time-points in the HCT 116 colon cancer cells. Moreover, we determined that during purvalanol-mediated ER stress, autophagic machinery was also activated prior to apoptotic cell death finalization. Beclin-1 and Atg-5 expression levels were upregulated and LC3 was cleaved after a 6 h purvalanol treatment. Purvalanol induced mitochondrial membrane potential loss, caspase-7 and caspase-3 activation and PARP cleavage following a 48 h treatment. Thus, we conclude that the anticancer effect of purvalanol in HCT 116 cells was due to ER stress-mediated apoptosis; however, purvalanol triggered autophagy, which functions as a cell survival mechanism at early time-points.
authors.affiliation: Department of Molecular Biology and Genetics, Science and Letters Faculty, Istanbul Kultur University, Atakoy Campus, Bakirkoy-Istanbul 34156, Turkey.
authors.forename: Ajda
authors.initials: A
authors.lastname: Coker-Gürkan
authors.affiliation: Department of Molecular Biology and Genetics, Science and Letters Faculty, Istanbul Kultur University, Atakoy Campus, Bakirkoy-Istanbul 34156, Turkey.
authors.forename: Elif Damla
authors.initials: ED
authors.lastname: Arisan
authors.affiliation: Department of Molecular Biology and Genetics, Science and Letters Faculty, Istanbul Kultur University, Atakoy Campus, Bakirkoy-Istanbul 34156, Turkey.
authors.forename: Pınar
authors.initials: P
authors.lastname: Obakan
authors.affiliation: Department of Molecular Biology and Genetics, Science and Letters Faculty, Istanbul Kultur University, Atakoy Campus, Bakirkoy-Istanbul 34156, Turkey.
authors.forename: Kübra
authors.initials: K
authors.lastname: Akalın
authors.affiliation: Department of Molecular Biology and Genetics, Science and Letters Faculty, Istanbul Kultur University, Atakoy Campus, Bakirkoy-Istanbul 34156, Turkey.
authors.forename: Utku
authors.initials: U
authors.lastname: Özbey
authors.affiliation: Department of Molecular Biology and Genetics, Science and Letters Faculty, Istanbul Kultur University, Atakoy Campus, Bakirkoy-Istanbul 34156, Turkey.
authors.forename: Narcin
authors.initials: N
authors.lastname: Palavan-Unsal
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D001343:Autophagy / Q000187:drug effects; D059447:Cell Cycle Checkpoints / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D003110:Colonic Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D004721:Endoplasmic Reticulum / Q000378:metabolism; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D045325:HCT116 Cells; D006801:Humans; D009363:Neoplasm Proteins / Q000096:biosynthesis* / Q000235:genetics; D011687:Purines / Q000008:administration & dosage*; D056811:Unfolded Protein Response / Q000187:drug effects
chemical_list: C471843:6-((3-chloro)anilino)-2-(isopropyl-2-hydroxyethylamino)-9-isopropylpurine; D009363:Neoplasm Proteins; D011687:Purines