Abstract A35: Treatment with demethylating drugs inhibits tumor growth in leiomyosarcoma cell lines and xenograft models

• Published in: Clinical cancer research 2018-01, Vol.24 (2_Supplement), p.A35-A35
• Main Authors: Fischer, Cynthia De Carvalho, Hu, Yue, Singh, Jasvinder, Thakar, Maya, Thakar, Manjusha, Ahuja, Nita
• Format: Article
• Language: English
• ISSN: 1078-0432; 1557-3265
• DOI: 10.1158/1557-3265.SARCOMAS17-A35

Introduction: Leiomyosarcomas are rare mesenchymal neoplasms characterized by a smooth-muscle differentiation pattern. Patients show poor disease-specific survival due to high recurrence rates and low response to chemotherapy and radiation. Development of novel chemotherapeutic regimens is the need of the hour. Epigenetic mechanisms such as hypermethylation of gene promotor regions lead to abnormal gene silencing and have been found to influence the initiation and progression of cancer. Epigenetic drugs have been approved for treatment of various malignancies such as myelodysplastic syndrome, acute myeloid leukemias, and subsets of lymphomas. This study aims to understand the potential efficacy of epigenetic drugs called DNA methyltransferease inhibitors (DNMTi) in the treatment of leiomyosarcomas. Methods: DNMTi used in this study include azacytidine (Aza), decitabine (Dac), and guadecitabine. Aza and Dac are antimetabolites, which get incorporated onto RNA and DNA, respectively, leading to inhibition of DNMT. Guadecitabine is a novel prodrug for Dac with a longer half-life. Various leiomyosarcoma cell lines (SK-UT1, SK-LMS, and MES) were treated with varying doses of guadecitabine (0.01-5 ug/ml), decitabine (Dac: 0.1 uM-5uM), or azacitidine (Aza: 0.1 uM-5 uM) and incubated for a maximum of five days. Cell viability was measured daily via MTT assay. To further characterize the mechanism(s) of drug induced cell death, Caspase Glo® Assay (G8090) was utilized as a measure of apoptosis by proxy of Caspase 3 and 7 activity. CellToxTM Green Cytotoxicity Assay was then employed to measure membrane integrity, thus quantifying nonspecific cell death. This would further measure the toxic effect of the demethylating drugs on leiomyosarcoma cell lines. We also studied the effect of guadecitabine (3 mg/kg, 2x/week) treatment in vivo, using subcutaneous xenografts in NOD/SCID mice. Statistical analysis was conducted using GraphPad Prism 6. Results: Decreased cell viability was observed in all three leiomyosarcoma cell lines upon exposure to demethylating agents. SK-UT1 showed the highest sensitivity to all three epigenetic drugs (IC50 values: guadecitabine-0.3 uM, Aza-2.1 uM, and Dac-2.3 uM), MES was sensitive to Aza and guadecitabine (IC50 values: Aza-3.2 uM, guadecitabine-6.14 uM, and Dac-11.77 uM), and SK-LMS was sensitive only to Aza (IC50 values: Aza-2.6 uM, guadecitabine-9.6 uM, and Dac-10.3 uM). To better understand the effect of guadecitabine and AZA on these c