Abstract 5378: Epigenetic regugulation of osteosarcoma metastatic phenotype via histone deacetylace inhibition
Authors: Weiss Kurt R. , Mu Xiaodong , Brynien Daniel 
Published: August 2015

Abstract
Introduction:
The epigenetic modification of cancer cells regulates tumor development and metastasis. Epigenetic changes include DNA methylation and histone modification, both of which regulate gene expression but do not alter the genetic code. We have demonstrated differential DNA methylation status of tumor suppressor genes between highly metastatic K7M2 osteosarcoma (OS) cells and less metastatic K12 OS cells. The demethylation of tumor suppressor genes repressed the metastatic phenotype of K7M2 cells. Histone deacetylase inhibitors (HDAC inhibitors, HDIs) have been evaluated for epigenetic regulation of various malignancies, but the role of HDAC inhibitors in OS is unclear. Wehave investigated the effect of the HDAC inhibitor, suberoylanilide hydroxamic acid (SAHA), on highly metastatic K7M2 OS cells.
Methods:
1. Osteosarcoma cells: K7M2 and K12 are murineOS cell populations with differing metastatic potentials. K7M2 is highly metastatic to the lung but K12 is much less metastatic.
2. SAHA treatment: SAHA (25, 50, or 100 μM) in proliferation medium (10% FBS in DMEM) was used to culture the K7M2 cells. Cells were incubated with SAHA for 48 hours prior to fixation for observation, harvesting for mRNA isolation, or plating for invasion assays.
Results:
1. SAHA treatment (25, 50, or 100 μM for 48 hours) significantly decreased cell proliferation compared with untreated cells.
2. SAHA treatment of K7M2 cells modified cell morphology. K7M2 cells were cultured with or without SAHA (25, 50, 100 μM) for 48 hours. Staining of the actin cytoskeleton revealed structural differences in SAHA-treated cells: treated cells displayed fewer invadopodia and their shape was more polygonal, resembling less metastatic K12 cells.
3. SAHA treatment of K7M2 cells modified the expression tumorigenesis and metastasis-related genes.
Semi-quantitative polymerase chain reaction showed that the expressions of mammalian target of rapamycin (mTOR), aldehyde dehydrogenase-1 (ALDH-1), and peroxisome proliferator-activated receptor gamma coactivator 1 (PGC-1) were down-regulated in SAHA-treated K7M2 cells. The expression of microtubule-associated protein 1A/1B-light chain (LC3) was up-regulated.
4. K7M2 cells were cultured with or without SAHA (50 μM) for 2 days, and their invasion capacity through 2.5% matrigel was analyzed. SAHA treatment significantly reduced the cells’ invasion capacity.
Conclusion:
These data demonstrate that highly metastatic OS cells can be epigenetically modified with HDAC inhibition. SAHA treatment of K7M2 cells reduced both their proliferation and invasiveness, indicating that HDAC inhibition may potentially reduce tumor development and metastasis. The effect of SAHA on OS cells could be related to cytoskeletal changes and/or diminished expression of genes regulating tumor development and metastasis. In the future we will test the ability of SAHA to affect OS metastatic potential in vivo.
Citation Format: Kurt R. Weiss, Xiaodong Mu, Daniel Brynien. Epigenetic regugulation of osteosarcoma metastatic phenotype via histone deacetylace inhibition. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5378. doi:10.1158/1538-7445.AM2015-5378