Cancer Letters

Cancer Letters

Volume 384, 1 January 2017, Pages 60-69
Cancer Letters

Original Article
Targeting cancer cells through antibiotics-induced mitochondrial dysfunction requires autophagy inhibition

https://doi.org/10.1016/j.canlet.2016.09.023Get rights and content

Highlights

  • Cells exposed to antibiotics used in routine lab practice result in mitochondrial dysfunction.

  • Antibiotics induce ROS-dependent autophagy/mitophagy in both normal and cancer cells.

  • Cancer cells are not the perfect target for antibiotics, perhaps due to glycolitic shift.

  • Cancer cells repopulation capacity can be reduced by antibiotics and inhibition of autophagy.

Abstract

A significant part of current research studies utilizes various cellular models which imply specific antibiotics-containing media as well as antibiotics used for clonal selection or promoter de/activation. With the great success of developing such tools, mitochondria, once originated from bacteria, can be effectively targeted by antibiotics. For that reason, some studies propose antibiotics-targeting of mitochondria as part of anticancer therapy. Here, we have focused on the effects of various classes of antibiotics on mitochondria in cancer and non-cancer cells and demonlow mitochondrial membrane potential, reduced ATP production, altered morphology and lowered respiration rate which altogether suggested mitochondrial dysfunction (MDF). This was in parallel with increased level of reactive oxygen species (ROS) and decreased activity of mitochondrial respiration complexes. However, both survival and repopulation capacity of cancer cells was not significantly affected by the antibiotics, perhaps due to a glycolytic shift or activated autophagy. In turn, simultaneous inhibition of autophagy and treatment with antibiotics largely reduced tumorigenic properties of cancer cells suggesting potential strategy for anticancer therapy.

Introduction

For the last 70 years, antibiotics have been used worldwide on an enormous scale [1]. Despite their profound clinical effectiveness, a growing body of compelling evidence has now shown that even at low concentrations some antibiotics may inhibit mitochondrial functions and lead to detrimental changes on both molecular and physiological levels [2]. Mitochondria are key organelles that have an essential role in the life and death of cells [3]. Having a double-membrane organization, mitochondria are thought to have evolved from the genus rickettsia bacteria but have lost the peptidoglycans as they no longer required to carry out respiration [4]. These organelles should be considered as weakly gram-negative or even gram-indeterminate and likewise many bacteria can be targeted by antibiotics. After being neglected for many years, this fact has brought some attention not only from scientists using antibiotics in their cellular and animal models but also from the clinicians, and especially from the pharmaceutical companies, planning drug repurposing in anticancer therapy [5].

Yet, the possible role of antibiotics in MDF is unclear and seems to be tissue- and cell line-dependent. The current study focuses on the elucidation of the roles of several commonly used antibiotics on mitochondrial functions. We show evidence of MDF in both normal and cancer cells treated with antibiotics. Moreover, antibiotics can increase ROS and trigger autophagy in both types of cells. However, antibiotics did not significantly affect survival as well as repopulation capacity of cancer cells, perhaps due to a glycolytic shift or activated autophagy. In turn, simultaneous treatment with antibiotics and inhibitor of autophagy largely reduced tumorigenic properties of cancer cells suggesting their combinatory application as potential anticancer strategy.

Section snippets

Chemicals and antibodies

Manitol, cat# M4125 purity >99.5, N-acetyl-cystein (NAC), cat# A7250 purity >99.5, sucrose, cat# S0389 purity >99.5, Na3VO4, cat#590088, purity >99.5, NaF, cat#S7920, purity >99.5, cat#D2510, purity >99.5, deoxycholic acid, NP-40, cat# 9016-45-9, purity >99.5, Ethylene glycol-bis(2-aminoethylether)-N,N,N′,N′-tetraacetic acid (EGTA), cat#03777 purity >99.5, 4-(2-Hydroxyethyl)piperazine-1-ethanesulfonic acid (HEPES), cat# H3375, purity >99.5, NDPH oxidase inhibitor diphenyleneneiodonium chloride

Antibiotics treatment leads to MDF

In order to study the effects of various antibiotics on mitochondrial functions we utilized human metastatic breast cancer cells (CAL51) and non-cancer primary human fibroblasts (NF) representing glycolytic-prone and OXPHOS-prone cellular models. We treated cells with penicillin/streptomycin (as a universal supplement to cell media), tetracycline, kanamycin, G418-geneticin (aminoglycoside antibiotics), puromycine (aminonucleoside antibiotic) blasticidine, (efficient selective antibiotic) with

Discussion

MDF has been recognized for many years as a characteristic feature of many chronic illnesses, partially classified as mitochondrial diseases [19]. Not withholding the importance of that fact, the current work was focused on the role of induced MDF in experimental models utilizing different antibiotics. In particular, our study confirmed that major mitochondrial functions can be significantly compromised upon exposure of the cells with antibiotics. This observation is especially important for

Author contributions

Study design (ME, DG, ML, AL); experiments for mitochondrial morphology (ME, AL); biochemical experiments (DG, ML, AL); Statistical analyses (ME, DG, AL); TEM experiments (AL, DG), drafting the manuscript (DG, ML, AL).

Acknowledgments

Authors are grateful to Dr. Krejci (Laboratory of DNA Recombination and Repair, National Centre for Biomolecular Research, Masaryk University, Brno) for sharing materials Dr. Stjepan Uldrijan's lab for giving initial access to SeaHorse apparatus. MELL. is a FIS investigator (Miguel Servet grant CP03/00101). AL received support from Marie Curie – COFUND program (INCOMED – GA 267128) for the Institut de Recerca Vall d’Hebrón, Barcelona, Spain.

References (19)

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Both authors contributed equally to this work.

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