Modulation of Autophagy by a Thioxanthone Decreases the Viability of Melanoma Cells

• Type: Article in International Scientific Journal
• Date: 2016

Authors

Lima, RT (Author) Other; Sousa, D (Author) Other; Paiva, AM (Author) Other; Palmeira, A (Author) FFUP; Barbosa, J (Author) Other; Pedro, M (Author) Other; Pinto, MM (Author) Other; Emilia Sousa (Author) FFUP; Helena Vasconcelos, MH (Author) FFUP

Journal

Title: Molecules

Vol. 21 No. 7

Final page: 1343

ISSN: 1420-3049

Publisher: MDPI

Indexing

ISI Web of Knowledge - 17 Citations

Scopus - 19 Citations

Other information

Authenticus ID: P-00M-5T3

DOI: 10.3390/molecules21101343

Abstract (EN): (1) Background: Our previous studies unveiled the hit thioxanthone TXA1 as an inhibitor of P-glycoprotein (drug efflux pump) and of human tumor cells growth, namely of melanoma cells. Since TXA1 is structurally similar to lucanthone (an autophagy inhibitor and apoptosis inducer) and to N-10-substituted phenoxazines (isosteres of thioxanthones, and autophagy inducers), this study aimed at further assessing its cytotoxic mechanism and evaluating its potential as an autophagy modulator in A375-C5 melanoma cells; (2) Methods: Flow cytometry with propidium iodide (PI) for cell cycle profile analysis; Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay, flow cytometry with Annexin V/PI labeling and Western blot for apoptosis analysis were conducted. A pharmacophore approach was used for mapping TXA1 onto pharmacophores for autophagy induction. Autophagy analyses included transmission electron microscopy for visualization of autophagic structures, fluorescence microscopy for observation of monodansylcadaverine (MDC) staining, pattern of LC3 expression in the cells and acridine orange staining, and Western blot for autophagic proteins expression; (3) Results: TXA1 induced autophagy of melanoma cells at the GI(50) concentration (3.6 mu M) and apoptosis at twice that concentration. Following treatment with TXA1, autophagic structures were observed, together with the accumulation of autophagosomes and the formation of autophagolysosomes. An increase in LC3-II levels was also observed, which was reverted by 3-methyladenine (3-MA) (an early stage autophagy-inhibitor) but further increased by E-64d/pepstatin (late-stage autophagy inhibitors). Finally, 3-MA also reverted the effect of TXA1 in cellular viability; (4) Conclusion: TXA1 decreases the viability of melanoma cells by modulation of autophagy and may, therefore, serve as a lead compound for the development of autophagy modulators with antitumor activity.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 15