Tumour necrosis factor (TNF)-related apoptosis inducing ligand (TRAIL) is a promising anti-cancer agent that rapidly induces apoptosis in cancer cells. Unfortunately, the clinical application of recombinant TRAIL (rTRAIL) has been hampered by its common cancer resistance. Naturally TRAIL is delivered as a membrane-bound form by extracellular vesicles (EV-T) and is highly efficient for apoptosis induction. SCH727965 (dinaciclib), a potent cyclin-dependent kinase (CDK) inhibitor, was shown to synergize with other drugs to get better efficacy. However, it has never been investigated if dinaciclib coordinates with EV-T to enhance therapeutic results. This study explores the potential of combination therapy with EV-T and dinaciclib for cancer treatment. EV-T was successfully derived from human TRAIL transduced cells and shown to partially overcome resistance of A549 cells. Dinaciclib was shown to drastically enhance EV-T killing effects on cancer lines that express good levels of death receptor (DR) 5, which are associated with suppression of CDK1, CDK9 and anti-apoptotic proteins. Combination therapy with low doses of EV-T and dinaciclib induced strikingly enhanced apoptosis and led to complete regression in A549 tumors without any adverse side effects observed in a subcutaneous xenograft model. Tumor infiltration of mass NK cells and macrophages was also observed. These observations thus indicate that the combination of EV-T with dinaciclib is a potential novel therapy for highly effective and safe cancer treatment.
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