| Osteosarcoma (OS) is the most common orthopedic neoplasm, with a high
metastasis rate and a dismal prognosis despite surgery and chemotherapy.
Immunotherapies have offered cancer patients a ray of optimism, but their
impact on OS has been disappointing. The objective of this study is to assess
the effect of mono, dual, and triple combinations of CTLA-4, PD-L1, and TIM3
blockade on OS cell viability, apoptosis, and migration. The MG-63 and U-2 OS
cell lines were transfected with mono, dual, and triple combinations of siRNAs
specific for CTLA-4, PD-L1, and TIM3. After evaluation for transfection efficacy
by qRT-PCR, MTT assay and flow cytometry were applied to assess cell
viability and apoptosis rate in siRNA-transfected cells, respectively. Ultimately,
the migration of transfected cells was measured by wound-healing assay. First,
the qRT-PCR analysis revealed that in siRNA-transfected OS cells, CTLA-4,
PD-L1, and TIM3 were downregulated. The MTT assay and flow cytometry
results confirmed that silencing of these immune checkpoints in dual or triple
combinations, but not in the single-agent blockade, significantly decreases cell
viability and increases apoptosis, respectively. These effects were more significant
when triple silencing was performed. Finally, the wound-healing assay
revealed that dual and triple silencing of immune checkpoints significantly
inhibits cell migration, with triple silencing exhibiting a greater effect. Our
findings suggest that triple blockade of CTLA-4, PD-L1, and TIM3 is an effective
strategy for inhibiting tumor cell progression and migration in OS, whichrequires large-scale clinical investigations to be translated into broad therapeutic
applicability for OS patients. |