Therapeutic strategy for tumors with low-to-intermediate expression of B7 and OX40 costimulatory molecules: Combine an epigenetic agent with a viral vector for transduction of IL-2 and B7.1 genes, antagonistic antibodies directed against the checkpoint inhibitors (e.g, CTLA-4, PD-1) and agonist antibodies such as OX40 to improve costimulatory signaling to T cells.