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Tumor suppressor PTEN is mutated in canine osteosarcoma cell lines and tumors
R A Levine1, T Forest, C Smith
1Department of Molecular Medicine, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA. ral1@cornell.edu
Abstract:
Canine osteosarcoma (OS) cell lines contain mutations that directly or indirectly inactivate the tumor suppressor genes p53 and retinoblastoma. Another important tumor suppressor, PTEN, is mutated in many human cancers. To determine whether inactivation of PTEN plays a role in the pathogenesis of canine OS, we studied its expression in canine OS cell lines and tumors. Four of five canine OS cell lines (CO2, C03, CO5, and CO7) constitutively express high levels of the phosphorylated form of Akt, an indirect indicator of aberrant PTEN expression. PTEN protein is essentially absent from three of these cell lines (CO2, CO5, and CO7), whereas C03 contains a potentially inactivating amino acid substitution in PTEN at codon 340. Genomic hybridization experiments indicate that CO2, CO5, and CO7 contain large deletions within the PTEN gene. Ten of 15 OS tumors exhibit variable or negative PTEN staining. Evaluation of a PTEN-negative staining tumor by Southern blotting indicates that the PTEN gene is deleted in this tumor. These results indicate that PTEN is mutated or downregulated in a high percentage of canine OS cell lines and tumors and likely plays an important role in the pathogenesis of the disease.
Insights
PTEN gene mutations and loss are common in canine osteosarcoma (OS). This suggests PTEN inactivation is a key factor in the development of canine OS, impacting tumor suppressor pathways.
Area of Science:
- Oncology
- Canine Cancer Research
- Molecular Biology
Background:
- Canine osteosarcoma (OS) frequently involves mutations in tumor suppressor genes like p53 and retinoblastoma.
- PTEN is a critical tumor suppressor gene implicated in various human cancers.
- The role of PTEN in canine OS pathogenesis remains largely unexplored.
Purpose of the Study:
- To investigate the expression and potential inactivation of the PTEN gene in canine osteosarcoma cell lines and tumors.
- To determine if PTEN alterations contribute to the development of canine OS.
Main Methods:
- Analysis of PTEN protein expression in canine OS cell lines and tumors.
- Detection of PTEN gene mutations and deletions using genomic hybridization and Southern blotting.
- Assessment of phosphorylated Akt levels as an indirect indicator of PTEN activity.
Main Results:
- Four out of five canine OS cell lines showed high levels of phosphorylated Akt, indicating aberrant PTEN signaling.
- PTEN protein was absent in three cell lines, with one containing an inactivating mutation.
- Large PTEN gene deletions were identified in three cell lines.
- Variable or negative PTEN staining was observed in 10 of 15 OS tumors, with gene deletion confirmed in one case.
Conclusions:
- PTEN is frequently mutated, deleted, or downregulated in canine osteosarcoma cell lines and tumors.
- PTEN inactivation likely plays a significant role in the pathogenesis of canine osteosarcoma.
- These findings highlight PTEN as a potential therapeutic target in canine OS.