Therapeutic Potential of Ex Vivo Expanded γδ T Cells against Osteosarcoma Cells

Immunotherapy is an attractive therapeutic strategy for the treatment of osteosarcoma (OS). The unique features of gamma delta T cells have made them popular for cancer immunotherapy. Here, we expanded gamma delta T cells using human peripheral blood mononuclear cells (PBMCs) and investigated their therapeutic potential against OS cells. PBMCs from healthy donors were cultured for 10 days with CON medium (unstimulated control); EX media, CON with recombinant human interleukin-2 (rhIL-2) and zoledronate; and EX28 media, CON with rhIL-2, zoledronate, and CD3/CD28 activator. The expanded gamma delta T cells were isolated by magnetic cell separation or fluorescence-activated cell sorting, cultured with two OS cell lines (KHOS/NP and MG-63) at various cell ratios with or without doxorubicin or ifosfamide, and analyzed for cytotoxicity and cytokine secretion. The number of CD3(+)gamma delta TCR+V gamma 9(+) triple-positive gamma delta T cells and concentrations of IFN-gamma and TNF-alpha were highest in the rhIL-2 (100 IU) and zoledronate (1 mu M) supplemented culture conditions. The CD3/CD28 agonist did not show any additional effects on gamma delta T cell expansion. The expanded gamma delta T cells exhibited potent in vitro cytotoxicity against OS in a ratio- and time-dependent manner. The gamma delta T cells may enhance the effect of chemotherapeutic agents against OS and may be a new treatment strategy, including chemo-immunotherapy, for OS.