title: Exosome release and low pH belong to a framework of resistance of human melanoma cells to cisplatin.
abstract: Intrinsic resistance to cytotoxic drugs has been a main issue in cancer therapy for decades. Microenvironmental acidity is a simple while highly efficient mechanism of chemoresistance, exploited through impairment of drug delivery. The latter is achieved by extracellular protonation and/or sequestration into acidic vesicles. This study investigates the importance of extracellular acidosis and nanovesicle (exosome) release in the resistance of human tumour cell to cisplatin (CisPt); in parallel to proton pump inhibitors (PPI) ability of interfering with these tumour cell features. The results showed that CisPt uptake by human tumour cells was markedly impaired by low pH conditions. Moreover, exosomes purified from supernatants of these cell cultures contained various amounts of CisPt, which correlated to the pH conditions of the culture medium. HPLC-Q-ICP-MS analysis revealed that exosome purified from tumour cell culture supernatants contained CisPt in its native form. PPI pre-treatment increased cellular uptake of CisPt, as compared to untreated cells, in an acidic-depend manner. Furthermore, it induced a clear inhibition of exosome release by tumour cells. Human tumours obtained from xenografts pretreated with PPI contained more CisPt as compared to tumours from xenografts treated with CisPt alone. Further analysis showed that in vivo PPI treatment induced a clear reduction in the plasmatic levels of tumour-derived exosomes which also contained lower level of CisPt. Altogether, these findings point to the identification of a double mechanism that human malignant melanoma use in resisting to a dreadful cellular poison such as cisplatin. This framework of resistance includes both low pH-dependent extracellular sequestration and an exosome-mediated elimination. Both mechanisms are markedly impaired by proton pump inhibition, leading to an increased CisPt-dependent cytotoxicity.
authors: Department of Therapeutic Research and Medicine Evaluation, National Institute of Health, Rome, Italy.
authors: Cristina
authors: C
authors: Federici
authors: Department of Environment and Primary Prevention, National Institute of Health, Rome, Italy.
authors: Francesco
authors: F
authors: Petrucci
authors: Department of Environment and Primary Prevention, National Institute of Health, Rome, Italy.
authors: Stefano
authors: S
authors: Caimi
authors: Department of Ematology, Oncology and Molecular Biology, National Institute of Health, Rome, Italy.
authors: Albino
authors: A
authors: Cesolini
authors: Department of Therapeutic Research and Medicine Evaluation, National Institute of Health, Rome, Italy.
authors: Mariantonia
authors: M
authors: Logozzi
authors: Department of Therapeutic Research and Medicine Evaluation, National Institute of Health, Rome, Italy.
authors: Martina
authors: M
authors: Borghi
authors: National Centre for Chemicals Substances, National Institute of Health, Rome, Italy.
authors: Sonia
authors: S
authors: D'Ilio
authors: Department of Therapeutic Research and Medicine Evaluation, National Institute of Health, Rome, Italy.
authors: Luana
authors: L
authors: Lugini
authors: Department of Environment and Primary Prevention, National Institute of Health, Rome, Italy.
authors: Nicola
authors: N
authors: Violante
authors: Department of Therapeutic Research and Medicine Evaluation, National Institute of Health, Rome, Italy.
authors: Tommaso
authors: T
authors: Azzarito
authors: Department of Environment and Primary Prevention, National Institute of Health, Rome, Italy.
authors: Costanza
authors: C
authors: Majorani
authors: Department of Therapeutic Research and Medicine Evaluation, National Institute of Health, Rome, Italy.
authors: Daria
authors: D
authors: Brambilla
authors: Department of Therapeutic Research and Medicine Evaluation, National Institute of Health, Rome, Italy.
authors: Stefano
authors: S
authors: Fais
mesh_terms: D000818:Animals; D002021:Buffers; D016923:Cell Death / Q000187:drug effects; D045744:Cell Line, Tumor; D060833:Cellular Microenvironment / Q000187:drug effects; D002851:Chromatography, High Pressure Liquid; D002945:Cisplatin / Q000494:pharmacology*; D019008:Drug Resistance, Neoplasm / Q000187:drug effects*; D055354:Exosomes / Q000187:drug effects / Q000378:metabolism*; D005110:Extracellular Space / Q000187:drug effects / Q000378:metabolism; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism; D008545:Melanoma / Q000473:pathology*; D016513:Mice, SCID; D054328:Proton Pump Inhibitors / Q000494:pharmacology; D012015:Reference Standards; D012996:Solutions; D013054:Spectrophotometry, Atomic; D023041:Xenograft Model Antitumor Assays
chemical_list: D002021:Buffers; D054328:Proton Pump Inhibitors; D012996:Solutions; D002945:Cisplatin