A cancer vaccine technology is provided which knocks out expression of cell surface immune checkpoint proteins, to facilitate their processing by immune cells, and optionally by knocking-in the expression of cytokines to boost immune response. Non-replicating tumor cells lacking cell surface CD47 are highly effective immunizing agents against subcutaneous mouse melanoma. Whole-cell vaccines inhibited tumor growth, and immunophenotyping showed a dramatic increase in activated effector cell subsets and M1-type macrophages aided by a significant reduction in the tumor-associated macrophage and myeloid derived suppressor cell compartments. A remarkable downregulation of cell surface CD47 was observed in the tumors that did escape after vaccination with genetically modified cells, suggesting the intricate involvement of CD47 in a prophylactic situation. An effective vaccination strategy to increase tumor-specific immune response in solid tumors is provided to improve the outcome of cancer immunotherapy.
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