Introduction

T regulatory (T-regs) cells (CD4+, CD25+, FOXP3+) have been studied in many types of human and canine cancer patients, as they can attenuate the immune response to a specific tumor. The correlation of T-regs to CD8+ cells has been reported to be associated with disease progression and overall survival in cancer patients, including dogs with osteosarcoma (OSA). CD4+, RANKL+ T lymphocytes have also been associated with lung metastasis in humans, but have never been investigated in canine cancer patients. In the current study, we investigated the fluctuation of these cell populations in osteosarcoma bearing dogs over time.

Methods

Client-owned dogs with appendicular OSA who elected to pursue amputation followed by carboplatin chemotherapy. Flow cytometry of peripheral blood mononuclear cells was performed at four time points: Day 0 (amputation), Day 14 (prior to first dose of chemotherapy), Day 21 (one week after chemotherapy), and Day 35. Antibodies for the detection of CD4+ CD8+, CD25+, FoxP3 and RANKL were used to identify T lymphocyte populations.

Results

A total of 12 dogs were included in the study. T-regs substantially decreased at Day 14, followed by a marked increase at Day 21. The percentage of CD4+ RANKL+, and CD8+ RANKL+ cells were increased by Day 14, and surged at Day 21. The CD8+: T-regs ratio was constantly decreased after amputation

Conclusion

This study highlights surgery and chemotherapy-dependent increases of T-regs and CD4+ RANKL+ lymphocytes. These cells can potentially be targeted to support osteosarcoma patients through their chemotherapy protocol.