Abstract
Abstract DNA hypomethylation has been implicated in the coordinated targeting of various signaling pathways involved in tumor growth and metastasis. In the current study through various in vitro and in vivo assays, we have examined the plausibility of using universal methyl donar S-adenosyl methionine (SAM) for its ability to block breast cancer development, growth and metastasis in our xenograft and transgenic models of breast cancer. Treatment of highly invasive human triple negative breast cancer (TNBC) cell lines MDA-MB-231 and Hs578T with SAM resulted in a significant dose-dependent decrease in cell proliferation, invasion, migration, colony formation and increased apoptosis in vitro. Affymetrix gene expression array and real time PCR (qPCR) validated showed the ability of SAM to decrease the expression several genes implicated in cancer progression in MDA-MB-231 cells. For the in vivo studies, MDA-MB-231 cells expressing green fluorescent protein (MDA-MB-231-GFP) were inoculated into female CD-1 nude mice via mammary fat pad. From day three post tumor cell inoculation, animals were treated with SAM (0.8-1.6 mg/day) or vehicle alone as control via daily oral gavage and tumor volume was determined at weekly intervals for 10 weeks. SAM treatment caused a significant dose dependent decrease in tumor volume and GFP positive metastasis to lungs, liver and spleen in experimental animals compared to vehicle-treated controls. Analysis of RNA from primary tumors by qPCR showed the ability of SAM to cause a marked decrease in the expression of several pro-metastatic and EMT pathway genes. Pyrosequencing of tumoral DNA from control and experimental animals showed that SAM treatment causes a significant increase in the percentage of CpG methylation at the promoter region of several cancer-related genes which were seen to be downregulated in the qPCR assay. We next determined the effect of SAM in MMTV-PyMT transgenic mouse model of breast cancer where SAM treatment resulted in a significant delay in the development of mammary tumors and decreased tumor growth in experimental animals as compared to vehicle treated controls. SAM was found to bioavailable in the serum of experimental animals as determined by mass spectrometry and no notable adverse side effects were seen including any change in animal behavior. Results from these studies provide compelling evidence for the therapeutic potential of SAM in breast cancer to provide the rationale for initiating clinical trials with SAM in patients with breast and other common cancers as monotherapy or in combination setting with current therapeutic agents to reduce cancer associated morbidity and mortality. Citation Format: Niaz Mahmood, David Cheishvili, Ani Arakelian, William J. Muller, Moshe Szyf, Shafaat A. Rabbani. S-Adenosyl methionine (SAM) blocks breast cancer growth, invasion and metastasis in vitro and in vivo [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4346. doi:10.1158/1538-7445.AM2017-4346
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