Neuroblastoma (NB), a tumor of the primitive neural crest, despite aggressive treatment regimens, portends a poor long-term survival for patients with advanced high stage NB. Here, we investigated the effects of targeting two families of critical regulatory molecules involved in cancer progression, histone deacetylases (HDACs) and carbonic anhydrases (CAs). HDACs regulate the expression and activity of various proteins involved in carcinogenesis and cancer progression, whereas carbonic anhydrases (CAs) function in tumor cell pH homeostasis and therein regulation of growth, survival, and metastasis. In this study we have used HDAC inhibitor (HDACi), pyridylmethyl-N-{4-[(2-aminophenyl)-carbamoyl]-benzyl}-carbamate (MS-275) and CA inhibitor acetazolamide (AZ). We report that MS-275, at nanomolar concentrations, significantly reduced the tumor initiating cell fraction (TIC) in NB cell lines in reference to NT2/D1, a teratocarcinoma cell line, exhibiting a stem cell like phenotype in-vitro. Stemness genes Oct-5, SOX2 and nanog, assessed by flow cytometry and western blot were found to be significantly down-regulated after MS-275 treatment. Overall, the tumor growth inhibitory effect of MS-275 was demonstrated by cytotoxicity assays, FACs analysis, and “In cell Western” assay. In-vivo treatment with MS-275 (20 mg/Kg) in human NB SH-SY5Y subcutaneous NOD/SCID xenograft model significantly reduced the tumor weight after 21 days treatment compared to the control (AZ 30%; MS-275 85%; AZ+MS-275 90%); (AZ p<0.05; MS-275 and MS-275+AZ p<0.0001). The efficacy of MS-275 was further enhanced by co-administration of AZ (40 mg/Kg) without causing morbidity in mice. Electron microscopy and H&E staining revealed higher numbers of apoptotic cells in MS-275 and AZ+MS-275 treated tumors. Upon re-implantation of tumor cells from primary xenografts in mice, the MS-275+AZ treated cells did not produce palpable tumors after two months whereas untreated cells produced large tumors. This significant reduction in initial tumorigenicity and subsequent abrogation suggests potential elimination of NB tumor initiating cells. Thus MS-275 combined with AZ shows promise as a potent novel anti-NB therapeutic strategy given their current clinical utility.

Citation Format: Reza Bayat Mokhtari, Sr., Micky Tsui, Sr., Shamim Lotfi, Sr., Sushil Kumar, Sr., Narges Baluch, Syed S. Islam, Bikul Das, Herman Yeger. A novel therapeutic approach for neuroblastoma. [abstract]. In: Proceedings of the AACR Special Conference on Pediatric Cancer at the Crossroads: Translating Discovery into Improved Outcomes; Nov 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;74(20 Suppl):Abstract nr B45.