No abstract

Osteosarcoma (OS) has a high degree of chromosomal instability and total copy number (CN) changes. We examined 58 human OS samples including 40 primary tumors, 11 explants, and 7 cell lines using single nucleotide polymorphism (SNP) arrays, and revealed that 70% of the samples had one or more recurrent CN-neutral loss of heterozygosity (CNN‑LOH) also known as uniparental disomy (UPD). Importantly, 17% of the samples showed prominent homozygous deletion of 3q13.31, suggesting its role in tumorigenesis. We identified and characterized two novel lncRNAs, LOC285194 and BC040587, within this genomic locus, strongly suggesting their tumor suppressor activity. Frequent deletions and UPD suggest that OS often has mutant or non-expressed tumor suppressor genes including two lncRNAs.

Human liposarcoma (LPS) is one of the most common soft tissue sarcomas in adults. However, its molecular mechanism is poorly understood. For better understanding of the disease, we examined 54 human liposarcoma samples including 51 primary tumors and 3 cell lines (SW872, LP6, LP141) using Affymetrix 250K single nucleotide polymorphism (SNP) array. Allele-specific copy number (CN) analysis using anonymous references revealed that CN gain was dominant event over CN loss and loss of heterozygosity (LOH) in human LPS. Recurrent CN gain at 1q21–24 (43% of the samples), 5p13-p15 (46%), and 8q24 (41%) were identified. The most prominent CN gain was found in the 12q13-q15 region. 88% of the samples, mostly well-differentiated / de-differentiated subtype (WDLPS / DDLPS), showed various levels of CN gains centered at MDM2 gene. In addition to MDM2 amplicon, we also identified an MDM2-independent amplicon in the 12q13-q15 region centered at miR-26a-2 gene at the same frequency (88%). MDM2 amplicon almost always accompanied miR-26a-2 amplicon. Likewise, samples without MDM2 amplicon did not have a miR-26a-2 amplicon. Quantitative reverse transcription real-time PCR (qRT-PCR) analysis showed that this CN gain of miR-26a-2 was strongly correlated with high mRNA expression of the gene in the WDLPS / DDLPS subtype. Furthermore, high mRNA expression of miR-26a-2 significantly correlated with a worse patient survival (p=0.05). Interestingly, some samples in myxoid / round-cell subtype (MRC) also showed high expression of miR-26a-2 without any prominent CN changes. High expression in the MRC subtype was also correlated with poor patient survival (p=0.0029). Western blot analysis using LPS cell lines revealed that cells with high miR-26a-2 expression showed decreased levels of RB1 and PTEN, which are two verified targets of miR-26a-2. In conclusion, our analysis demonstrated the clinical importance of miR-26a-2 gene in human LPS. This finding may contribute to the discovery of prognostic markers as well as novel therapeutic targets for human LPS. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr LB-345. doi:10.1158/1538-7445.AM2011-LB-345

Bromodomain and extra terminal domain (BET) proteins are important epigenetic regulators facillitating the transcription of genes in chromatin areas linked to acetylated histones. JQ1, a BET protein inhibitor, has antiproliferative activity againts many hematological and solid cancers, mainly through inhibition of c-myc and upregulation of p21. In this research, we investigated the use of JQ1 for human osteosarcoma (OS) treatment, due to the frequent copy number gain and overexpression of c-myc in OS cells. JQ1 significantly inhibited the proliferation and survival of seven OS cells (U2OS, G292, MG-63, HT-161, MNNG/HOS, SAOS-2, SJSA), at a relatively higher dose than other cancers (median IC50 = 7.35 μM). JQ1 induced G1 cell cycle arrest and premature senescence of OS cells, but produced little apoptosis. Interestingly, c-myc protein levels in JQ1-treated cells remained unchanged, whereas the upregulation of p21 protein was still observable, as noted by Western blots. Although effective in vitro, JQ1 failed to reduce the size of the MNNG/HOS xenografts in immunocompromised mice in vivo. To overcome the resistance of OS cells to JQ1 treatment, we tested JQ1 in combination with rapamycin. Rapamycin inhibits the assembly of mTOR complexes which is one of the important growth signaling pathways in many cancers including OS. JQ1 and rapamycin synergistically inhibited the growth and survival of OS cells in vitro. The drug combination nearly abrogated expression of c-myc protein, enhanced levels of p21, and induced apoptosis in OS cells in vitro. After 24 days of treatment in vivo, JQ1 (50mg/kg body weight) or rapamycin (1.5 mg/kg body weight) alone showed little effect on the size of human OS xenografts in nude mice. However, combination of both drugs significantly inhibited tumor growth by 85% and 73% (p<0.05 for both) compared to either JQ1 or rapamycin alone, respectively. In conclusion, JQ1 inhibited proliferation and survival of OS cells in vitro but failed to reduce growth of OS xenografts in immunodeficient mice. When combined with rapamycin, JQ1 synergistically inhibited proliferation of OS cells both in vitro and in vivo. Citation Format: Dhong Hyun Tony Lee, Jun Qi, James Bradner, Jonathan Said, Ngan Doan, Charles Forscher, H Phillip Koeffler. Synergistic effect of JQ1 and rapamycin for treatment of human osteosarcoma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1689. doi:10.1158/1538-7445.AM2014-1689