Reexpression of LSAMP inhibits tumor growth in a preclinical osteosarcoma model
Tale Barøy, Stine H Kresse, Magne Skårn
1Department of Tumor Biology, Institute for Cancer Research, Oslo University Hospital, The Norwegian Radium Hospital, Oslo, Norway. leonardo.meza-zepeda@rr-research.no.
Background:
Osteosarcomas are the most common primary malignant tumors of bone, showing complex chromosomal rearrangements with multiple gains and losses. A frequent deletion within the chromosomal region 3q13.31 has been identified by us and others, and is mainly reported to be present in osteosarcomas. The purpose of the study was to further characterize the frequency and the extent of the deletion in an extended panel of osteosarcoma samples, and the expression level of the affected genes within the region. We have identified LSAMP as the target gene for the deletion, and have studied the functional implications of LSAMP-reexpression.
Methods:
LSAMP copy number, expression level and protein level were investigated by quantitative PCR and western blotting in an osteosarcoma panel. The expression of LSAMP was restored in an osteosarcoma cell line, and differences in proliferation rate, tumor formation, gene expression, migration rate, differentiation capabilities, cell cycle distribution and apoptosis were investigated by metabolic dyes, tumor formation in vivo, gene expression profiling, time-lapse photography, differentiation techniques and flow cytometry, respectively.
Results:
We found reduced copy number of LSAMP in 45/76 osteosarcoma samples, reduced expression level in 25/42 samples and protein expression in 9/42 samples. By restoring the expression of LSAMP in a cell line with a homozygous deletion of the gene, the proliferation rate in vitro was significantly reduced and tumor growth in vivo was significantly delayed. In response to reexpression of LSAMP, mRNA expression profiling revealed consistent upregulation of the genes hairy and enhancer of split 1 (HES1), cancer/testis antigen 2 (CTAG2) and kruppel-like factor 10 (KLF10).
Conclusions:
The high frequency and the specificity of the deletion indicate that it is important for the development of osteosarcomas. The deletion targets the tumor suppressor LSAMP, and based on the functional evidence, the tumor suppressor function of LSAMP is most likely exerted by reducing the proliferation rate of the tumor cells, possibly by indirectly upregulating one or more of the genes HES1, CTAG2 or KLF10. To our knowledge, this study describes novel functions of LSAMP, a first step to understanding the functional role of this specific deletion in osteosarcomas.
Insights
A common deletion in osteosarcoma targets the tumor suppressor LSAMP, reducing its expression. Restoring LSAMP expression inhibits tumor cell proliferation and growth, suggesting LSAMP
Area of Science:
- Oncology
- Genetics
- Molecular Biology
Background:
- Osteosarcomas are primary bone tumors with complex chromosomal abnormalities.
- A recurrent deletion at chromosomal region 3q13.31 is frequently observed in osteosarcomas.
- LSAMP (a gene within 3q13.31) is identified as a key target of this deletion.
Purpose of the Study:
- To determine the frequency and extent of the 3q13.31 deletion in osteosarcoma.
- To investigate the expression levels of genes within the deleted region.
- To elucidate the functional role of LSAMP in osteosarcoma development and progression.
Main Methods:
- Quantitative PCR and Western blotting assessed LSAMP copy number, mRNA, and protein levels.
- LSAMP expression was restored in an osteosarcoma cell line.
- Functional assays evaluated proliferation, tumor formation, gene expression, migration, differentiation, cell cycle, and apoptosis.
Main Results:
- Reduced LSAMP copy number found in 45/76 osteosarcomas; reduced expression in 25/42; protein loss in 9/42.
- LSAMP re-expression significantly decreased proliferation in vitro and delayed tumor growth in vivo.
- LSAMP re-expression upregulated HES1, CTAG2, and KLF10 mRNA levels.
Conclusions:
- The 3q13.31 deletion targeting LSAMP is frequent and specific to osteosarcoma development.
- LSAMP functions as a tumor suppressor by reducing proliferation, potentially via HES1, CTAG2, or KLF10.
- This study reveals novel functions of LSAMP and its role in osteosarcoma pathogenesis.
