Current strategies for adoptive immunotherapy for cancer: ”Off-the-shelf” immune cells

Immunotherapy, especially immune cell-based therapy, is a strategy for cancer treatment that has over the past decades focused on novel modifications and targets. In recent years, adoptive cell immunotherapy has continuously evolved, with studies of different platforms utilizing different immune effector cells to kill a variety of cancer cells. This review summarizes the various kinds of immune cells which have been used in adoptive cell therapy (ACT), including natural killer cells, cytokine-induced killer cells, T cells, and engineered immune cells. Most reports have shown that ACT can induce tumor regression, both in animal studies and clinical trials. However, the high cost of ACT is the greatest disadvantage of this strategy. Moreover, the efficacy of treatment is variable among patients. To reduce these disadvantages, off-the-shelf immune cells are considered the best solution to reduce the cost while maintaining the efficacy of treatment. In this review, we will discuss the potential of various kinds of immune cells for development as ``off-the-shelf'' immune cells for use in adoptive cell therapy, based on their unique advantages.