title: Selective inhibition of tumor cell associated Vacuolar-ATPase 'a2' isoform overcomes cisplatin resistance in ovarian cancer cells.
abstract: Development of resistance to platinum compounds significantly hinders successful ovarian cancer (OVCA) treatment. In tumor cells, dysregulated pH gradient across cell membranes is a key physiological mechanism of metastasis/chemo-resistance. These pH alterations are mediated by aberrant activation of key multi-subunit proton pumps, Vacuolar-ATPases (V-ATPases). In tumor cells, its 'a2' isoform (V-ATPase-V0a2) is a component of functional plasma-membrane complex and promotes tumor invasion through tumor-acidification and immuno-modulation. Its involvement in chemo-resistance has not been studied. Here, we show that V-ATPase-V0a2 is over-expressed in acquired-cisplatin resistant OVCA cells (cis-A2780/cis-TOV112D). Of all the 'a' subunit isoforms, V-ATPase-V0a2 exhibited an elevated expression on plasma membrane of cisplatin-resistant cells compared to sensitive counterparts. Immuno-histochemistry revealed V-ATPase-V0a2 expression in both low grade (highly drug-resistant) and high grade (highly recurrent) human OVCA tissues indicating its role in a centralized mechanism of tumor resistance. In cisplatin resistant cells, shRNA mediated inhibition of V-ATPase-V0a2 enhanced sensitivity towards both cisplatin and carboplatin. This improved cytotoxicity was mediated by enhanced cisplatin-DNA-adduct formation and suppressed DNA-repair pathway, leading to enhanced apoptosis. Suppression of V0a2 activity strongly reduced cytosolic pH in resistant tumor cells, which is known to enhance platinum-associated DNA-damage. As an indicator of reduced metastasis and chemo-resistance, in contrast to plasma membrane localization, a diffused cytoplasmic localization of acidic vacuoles was observed in V0a2-knockdown resistant cells. Interestingly, pre-treatment with monoclonal V0a2-inhibitory antibody enhanced cisplatin cytotoxicity in resistant cells. Taken together, our findings suggest that the isoform specific inhibition of V-ATPase-V0a2 could serve as a therapeutic strategy for chemo-resistant ovarian carcinoma and improve efficacy of platinum drugs.
authors.affiliation: Department of Microbiology and Immunology, Rosalind Franklin University of Medicine and Science, North Chicago, IL, USA.
authors.forename: Arpita
authors.initials: A
authors.lastname: Kulshrestha
authors.affiliation: Department of Microbiology and Immunology, Rosalind Franklin University of Medicine and Science, North Chicago, IL, USA.
authors.forename: Gajendra K
authors.initials: GK
authors.lastname: Katara
authors.affiliation: Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, IL, USA.
authors.forename: Jordyn
authors.initials: J
authors.lastname: Ginter
authors.affiliation: Department of Microbiology and Immunology, Rosalind Franklin University of Medicine and Science, North Chicago, IL, USA.
authors.forename: Sahithi
authors.initials: S
authors.lastname: Pamarthy
authors.affiliation: Department of Microbiology and Immunology, Rosalind Franklin University of Medicine and Science, North Chicago, IL, USA.
authors.forename: Safaa A
authors.initials: SA
authors.lastname: Ibrahim
authors.affiliation: Department of Microbiology and Immunology, Rosalind Franklin University of Medicine and Science, North Chicago, IL, USA.
authors.forename: Mukesh K
authors.initials: MK
authors.lastname: Jaiswal
authors.affiliation: Department of Obstetrics & Gynecology, Advocate Lutheran General Hospital, Park Ridge, IL, USA.
authors.forename: Corina
authors.initials: C
authors.lastname: Sandulescu
authors.affiliation: Department of Obstetrics & Gynecology, Advocate Lutheran General Hospital, Park Ridge, IL, USA.
authors.forename: Ramayee
authors.initials: R
authors.lastname: Periakaruppan
authors.affiliation: Department of Obstetrics & Gynecology, Advocate Lutheran General Hospital, Park Ridge, IL, USA.
authors.forename: James
authors.initials: J
authors.lastname: Dolan
authors.affiliation: Department of Microbiology and Immunology, Rosalind Franklin University of Medicine and Science, North Chicago, IL, USA.
authors.forename: Alice
authors.initials: A
authors.lastname: Gilman-Sachs
authors.affiliation: Department of Microbiology and Immunology, Rosalind Franklin University of Medicine and Science, North Chicago, IL, USA. Electronic address: kenneth.beaman@rosalindfranklin.edu.
authors.forename: Kenneth D
authors.initials: KD
authors.lastname: Beaman
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D016190:Carboplatin / Q000494:pharmacology; D045744:Cell Line, Tumor; D002945:Cisplatin / Q000494:pharmacology*; D018736:DNA Adducts / Q000235:genetics; D004249:DNA Damage / Q000187:drug effects; D019008:Drug Resistance, Neoplasm; D005260:Female; D006801:Humans; D010051:Ovarian Neoplasms / Q000188:drug therapy* / Q000235:genetics* / Q000473:pathology; D010053:Ovary / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D006180:Proton-Translocating ATPases / Q000032:analysis / Q000235:genetics*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics
chemical_list: C525845:ATP6V0A2 protein, human; D000970:Antineoplastic Agents; D018736:DNA Adducts; D034741:RNA, Small Interfering; C057270:cisplatin-DNA adduct; D016190:Carboplatin; D006180:Proton-Translocating ATPases; D002945:Cisplatin
keywords: Cisplatin resistance; Ovarian cancer; Vacuolar ATPase; a2 isoform