title: Phenethyl caffeate benzoxanthene lignan is a derivative of caffeic acid phenethyl ester that induces bystander autophagy in WiDr cells.
abstract: We recently reported that Phenethyl caffeate benzoxanthene lignan (PCBL), a semisynthetic compound derived from Caffeic Acid Phenethyl Ester (CAPE), induces DNA damage and apoptosis in tumor cells. In this study, we further investigated whether PCBL induces autophagy in WiDr cells. We also analyzed the pathways regulating autophagy and the role of autophagy in PCBL-induced cell death. Our acridine orange staining and LC3 II expression results suggest that PCBL induces autophagosomes in WiDr cells. The levels of LC3 II expression we observed after co-treatment of PCBL with bafilomycin A1 and the reductions in p62 expression we observed after PCBL treatment in WiDr cells demonstrate increased autophagic flux, a reliable indicator of autophagic induction. The increased Beclin 1 expression in PCBL-treated cells and the incapacity of PCBL to induce LC3 II in 3-methyladenine (3-MA)-treated cells we observed suggests that PCBL-induced autophagy is class III PI3-kinase dependent. PCBL did not alter phosphorylation of the mTOR substrate p70 S6 kinase, indicating that PCBL-induced autophagy was not mTOR regulated. Two autophagy related proteins, Atg5 and Atg12, also remained uninduced during PCBL treatment. The increased caspase activity and expression levels of LC3 II and p62 we observed in response to PCBL treatment in primary glioma cells demonstrates that PCBL-induced apoptosis and autophagy were not cell line specific. Pharmacological inhibition of autophagy did not alter the antitumor efficacy of PCBL in WiDr cells. This attests to the bystander nature of PCBL-induced autophagy (in terms of cell death). In toto, these data suggest that PCBL induces a class III kinase dependent, but mTOR independent, bystander mode of autophagy in WiDr cells.
authors.affiliation: Department of Biochemistry, Sree Chitra Tirunal Institute for Medical Science and Technology, Thiruvanathapuram, 695011, India.
authors.forename: Vinod
authors.initials: V
authors.lastname: Vijayakurup
authors.forename: Carmela
authors.initials: C
authors.lastname: Spatafora
authors.forename: Corrado
authors.initials: C
authors.lastname: Tringali
authors.forename: Padmakrishnan Chorakkode
authors.initials: PC
authors.lastname: Jayakrishnan
authors.forename: Priya
authors.initials: P
authors.lastname: Srinivas
authors.forename: Srinivas
authors.initials: S
authors.lastname: Gopala
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D001343:Autophagy / Q000187:drug effects*; D000071192:Autophagy-Related Protein 12; D000071187:Autophagy-Related Protein 5; D024201:Bystander Effect; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D004354:Drug Screening Assays, Antitumor; D015870:Gene Expression / Q000187:drug effects; D005910:Glioma; D006801:Humans; D017705:Lignans / Q000494:pharmacology*; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000378:metabolism; D025841:Small Ubiquitin-Related Modifier Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: C466624:ATG12 protein, human; C502778:ATG5 protein, human; D000970:Antineoplastic Agents; D000071192:Autophagy-Related Protein 12; D000071187:Autophagy-Related Protein 5; D017705:Lignans; D008869:Microtubule-Associated Proteins; D025841:Small Ubiquitin-Related Modifier Proteins; C577829:bis(2-phenylethyl)-6,9,10-trihydroxybenzo(kl)xanthene-1,2-dicarboxylate; D019869:Phosphatidylinositol 3-Kinases; D038762:Ribosomal Protein S6 Kinases, 70-kDa; C448901:ribosomal protein S6 kinase, 70kD, polypeptide 1