Toward Understanding the Antitumor Effects of Water-Soluble Fullerene Derivatives on Lung Cancer Cells: Apoptosis or Autophagy Pathways? Chui-Wei Wong, † Alexander V. Zhilenkov, § Olga A. Kraevaya, §,∥ Denis V. Mischenko, § Pavel A. Troshin,* ,§,∥ and Shan-hui Hsu* ,†,‡,⊥ † Institute of Polymer Science and Engineering and ‡ Research and Development Center for Medical Devices, National Taiwan University, Taipei 10617, Taiwan § Institute for Problems of Chemical Physics of Russian Academy of Sciences, Chernogolovka 142432, Russian Federation ∥ Skolkovo Institute of Science and Technology, Moscow 143026, Russian Federation ⊥ Institute of Cellular and System Medicine, National Health Research Institutes, Miaoli 35053, Taiwan *S Supporting Information ABSTRACT: Here we report the synthesis and investigation of anticancer effects of a series of water-soluble fullerene derivatives bearing amino acid (F1−F7) and thioacid (F8−F10) residues. Compounds F4 and F10 efficiently inhibited proliferation of lung cancer cells in vitro while being nontoxic to endothelial cells. It was revealed that the cancer cell death was caused by either autophagy (F4) or apoptosis (F10). Both fullerene derivatives strongly inhibited the tumor growth in the zebrafish xenograft model. In contrast to the vast majority of known cytostatics, fullerene derivatives do not show any significant acute toxicity effects in mice. Importantly, functional groups attached to the carbon cage affect interaction of the compounds with cancer cells, thus enabling realization of two different cell death mechanisms. The obtained results pave a way to the development of a new generation of selective antitumor drugs suppressing efficiently the proliferation of cancer cells while being nontoxic to normal cells. 1. INTRODUCTION Implementation of nanotechnology opened broad opportu- nities for the development of modern medicine, especially in the field of cancer therapeutics. The unique geometric features, and physicochemical and, particularly, surface properties of nanomaterials facilitate their interactions with biological targets, making them much more efficient compared with the conventional small-molecule drugs. 1 Fullerene C 60 , originally named buckminsterfullerene, represents a symmetrical hollow molecule with the cagelike structure composed of 20 hexagons and 12 pentagons 2 and has a molecular diameter of approximately 1 nm. Fullerene C 60 and its derivatives form an important family of nanomaterials 2 though it has negligibly low solubility in aqueous media and undergoes aggregation very easily, 3,4 which hamper its biomedical applications. Attaining high aqueous solubility for hydroxylated fullerenes C 60 (OH) n obtained via chemical modification of C 60 in the early 1990s inspired intense exploration of the potential of water-soluble fullerenes in the field of biomedicine. 5 Water- soluble fullerene derivatives are frequently tested as delivery vehicles for anticancer drugs and magnetic resonance imaging contrast agents. 6,7 Fullerene derivatives also generate efficiently single oxygen and other reactive oxygen species under illumination, so they are intensively explored as potential drugs for photodynamic antitumor therapy. 8−10 Another very promising research direction is based on combining standard clinical cytostatic drugs with the fullerene derivatives. 11 In particular, this approach is very beneficial when using hydrophobic anticancer drugs such as paclitaxel. 12 The chemotherapeutic drugs, such as anthracycline antibiotics, cause cancer cell death by generating excessive oxidative stress. 13,14 Meanwhile, water-soluble fullerene derivatives have plenty of conjugated double bonds that have strong activity with respect to the addition of radical species and, therefore, serve as radical sponges. These radical scavenging properties mitigate the side effects of oxidative stress caused in normal cells by standard antitumor drugs and slightly enhance their therapeutic efficiency against cancer due to passive targeting effects. 15 In other words, some water-soluble fullerene derivatives might exert a protective effect from the oxidative stress generated by the classical small-molecule drugs. 16 Additionally, fullerenes might induce structural and elastic property changes in the lipid membrane, 17 thus allowing these compounds and loaded drug molecules to enter the cells and Received: April 17, 2019 Article pubs.acs.org/jmc Cite This: J. Med. Chem. XXXX, XXX, XXX-XXX © XXXX American Chemical Society A DOI: 10.1021/acs.jmedchem.9b00652 J. Med. Chem. XXXX, XXX, XXX−XXX Downloaded via UNIV OF SOUTHERN INDIANA on July 30, 2019 at 14:26:37 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.