Panoply™ Human CD7 Over-expressing Stable Cell Line

CD7 has been confirmed as a promising chimeric antigen receptor (CAR) T cell target in multiple clinical trials. However, its expression on normal T cells poses additional challenges to CD7-targeted CAR therapy, such as complete fratricide, malignant cell contamination, and immunosuppression caused by incomplete T cell development. Taking advantage of the evolved affinity between the ligand and the receptor, researchers constructed a CD7-targeted CAR with its extracellular domain (SECTM1, the natural ligand of CD7) as the recognition domain. SECTM1 CAR T cells killed most T cells with high CD7 expression in vitro. However, SECTM1 CAR T cells with low or negative CD7 expression survived, expanded in vitro, and showed strong cytotoxicity against CD7+ malignant cell lines and primary leukemic blasts from patients with T-cell acute lymphoblastic leukemia and acute myeloid leukemia. The CAR T cells also showed efficacy in inhibiting xenograft tumor growth in vivo. Further exploration of its potential for clinical efficacy in patients with CD7+ malignancies is needed.

To further confirm the specific cytotoxicity of SCETM1 CAR T cells, the researchers examined changes in cytotoxicity after altered CD7 expression. First, CD7 was overexpressed in K562 cells (K562 CD7 cells) and confirmed by flow cytometry (Figure 1A) and real-time PCR. Then, K562 CD7 cells were co-cultured with SECTM1 CAR T cells at an E:T ratio of 2:1. SECTM1 CAR T cells strongly lysed 63.1% of CD7-overexpressing K562 cells, while the lysis rate of K562 control cells was 16.1% (Figure 1B). Moreover, this lysis was accompanied by significant IFNγ release in cells co-cultured with CD7-overexpressing K562 cells, but not in cells co-cultured with K562 control cells (Figure 1C). In contrast, normal T cells were transduced with lentiviral particles that induced CD7 knockdown, and the reduction in CD7 expression levels was confirmed by real-time fluorescence quantitative PCR and flow cytometry. The best constructs, shCD7#3 and shCD7#5, were selected for cytotoxicity assay (Figure 1D). As expected, the cytotoxicity of SECTM1 CAR T cells against CCRF-CEM-shCD7 cells was lower than that against control CCRF-CEM-shCOO2 cells (Figure 1E). In addition, the IFNγ released by SECTM1 CAR T cells when co-cultured with CD7-silenced tumor cells was lower than that when co-cultured with control tumor cells (Figure 1F). All these data indicate that the cytotoxicity of SECTM1 CAR T cells against tumor cells is dependent on CD7.

Figure 1. SECTM1 CAR T cells lysed tumor cells in a CD7-dependent manner. (Wei W, et al., 2023)