Immunotherapy using chimeric antigen receptor (CAR) T cells is a rapidly emerging modality that engineers T cells to redirect tumor-specific cytotoxicity. CAR T cells have been well characterized for their efficacy against B cell malignancies, and rigorously studied in other types of tumors. Preclinical evaluation of CAR T cell function, including direct tumor killing, cytokine production, and memory responses, is crucial to the development and optimization of CAR T cell therapies. Such comprehensive examinations are usually performed in different types of models. Model establishment should focus on key challenges in the clinical setting and the capability to generate reliable data to indicate CAR T cell therapeutic potency in the clinic. Further, modeling the interaction between CAR T cells and tumor microenvironment provides additional insight for the future endeavors to enhance efficacy, especially against solid tumors. This review will summarize both in vitro and in vivo models for CAR T cell functional evaluation, including how they have evolved with the needs of CAR T cell research, the information they can provide for preclinical assessment of CAR T cell products, and recent technology advances to test CAR T cells in more clinically relevant models.

MicroRNAs (miRNAs) are a class of non-coding RNAs involved in a variety of pathophysiological processes. We have previously reported that the abnormally high expression of miR-99a is associated with drug resistance and poor prognosis in acute myeloid leukemia. However, the impact of miR-99a on normal hematopoiesis is not well understood. To investigate the effect of aberrant miR-99a overexpression on hematopoietic stem and progenitor cells (HSPCs), we overexpressed miR-99a in human umbilical cord blood CD34⁺ cells. We observed that miR-99a overexpression increased the proliferation, self-renewal capacity, and transplantation efficiency of HSPCs with or without a clonal hematopoiesis-associated mutation (JAK2^V617F). Meanwhile, we found that overexpression of miR-99a blocked the maturation and differentiation of granulocytes/monocytes and erythrocytes. We then identified NIPBL as a direct target of miR-99a. NIPBL knockdown in HSPCs showed a phenotype similar to miR-99a overexpression. In this study, we elucidate that abnormally high expression of miR-99a can enhance the proliferative capacity of HSPCs but inhibit myeloid differentiation and maturation. Taken together, our work has uncovered important roles for miR-99a in regulating HSPCs by enhancing the proliferation and self-renewal capacity of HSPCs but inhibiting differentiation, which play important roles in leukemic transformation.