title: Oral RKS262 reduces tumor burden in a neuroblastoma xenograft animal model and mediates cytotoxicity through SAPK/JNK and ROS activation in vitro.
abstract: Patients diagnosed with high-risk neuroblastoma (NB), an extracranial solid tumor in children, have metastases and low survival (30%) despite aggressive multi-modal therapy. Therefore new therapies are urgently needed. We show significant in vitro and in vivo antitumor efficacy of RKS262 in NB. RKS262 showed superior cytotoxicity (IC(50) = 6-25 μM) against six representative NB cell lines compared to its parent analog Nifurtimox (currently in phase 2). Pre-formulated RKS262 (150 mg/kg/daily) pellets administered orally, suppressed tumor growth (60%, p = 0.021) in NB xenograft mice within 28 days. RKS262-treated SMSKCNR cells showed TUNEL-positive DNA nicks and activation of ROS, MAPKs (SAPK/JNK), caspase-3, and p53, along with suppression of the IGF-1R/PI3K/PKC pathway and the Bcl2 family of proteins. RKS262 caused G(2)/M-phase arrest and suppressed cdc-2, cyclin B1, p21, and cyclin D1/D4 expression. N-acetyl-cysteine (NAC; 10 mM) pre-treatment rescued cell viability of RKS262 (23 µM)-treated SMSKCNR cells, and pre-treatment with ascorbic acid (100 μM) and a MAPK inhibitor SB203580 (20 μM) reversed SAPK/JNK, caspase-3 activation, PARP-1 cleavage, and suppression of IGF-1R, PI3K, and PKC phosphorylation. Further, treatment with exogenous BDNF (50 nM) did not suppress SAPK/JNK or ROS activation due to RKS262. Rather, BDNF (50 nM), EGF (100 nM) and IGF-1 (100 nM) co-treatment with RKS262 induced a remarkable S-phase arrest rather than a G(2)/M phase arrest when RKS262 was used alone. In summary, RKS262 shows oral efficacy in NB xenograft animals, and induces apoptosis in vitro in SMSKCNR cells via cell cycle arrest, MAPK and ROS activation, and suppression of IGF-1R/PI3K/PKC and Bcl2 family proteins in a growth factor (BDNF/EGF/IGF-1)-independent fashion.
authors.affiliation: Women and Infants' Hospital, Department of Obstetrics and Gynecology, Alpert Medical School of Brown University, Providence, RI, USA.
authors.forename: Rakesh K
authors.initials: RK
authors.lastname: Singh
authors.forename: Lee
authors.initials: L
authors.lastname: Dorf
authors.forename: Angelica
authors.initials: A
authors.lastname: DeMartino
authors.forename: Sharon
authors.initials: S
authors.lastname: Illenye
authors.forename: Karen
authors.initials: K
authors.lastname: Koto
authors.forename: Erika A
authors.initials: EA
authors.lastname: Currier
authors.forename: Takamaru
authors.initials: T
authors.lastname: Ashikaga
authors.forename: Kyu Kwang
authors.initials: KK
authors.lastname: Kim
authors.forename: Laurent
authors.initials: L
authors.lastname: Brard
authors.forename: Giselle L Saulnier
authors.initials: GL
authors.lastname: Sholler
mesh_terms: D000284:Administration, Oral; D000818:Animals; D000970:Antineoplastic Agents / Q000737:chemistry / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D019208:Brain-Derived Neurotrophic Factor / Q000494:pharmacology; D053148:Caspase 3 / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D003374:Coumarins / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology*; D003499:Cyclic S-Oxides / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology*; D004815:Epidermal Growth Factor / Q000494:pharmacology; D005260:Female; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D051379:Mice; D008819:Mice, Nude; D009447:Neuroblastoma / Q000378:metabolism* / Q000473:pathology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D047368:Tumor Burden / Q000187:drug effects*; D023041:Xenograft Model Antitumor Assays
chemical_list: D000970:Antineoplastic Agents; D019208:Brain-Derived Neurotrophic Factor; D003374:Coumarins; D003499:Cyclic S-Oxides; D019253:Proto-Oncogene Proteins c-bcl-2; C557291:RKS 262; D017382:Reactive Oxygen Species; D004815:Epidermal Growth Factor; D007334:Insulin-Like Growth Factor I; D048031:JNK Mitogen-Activated Protein Kinases; D053148:Caspase 3