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M. Gurney et al.
effects. The established anti-leukemic activity of alloreac- tive NK cells in AML provides a rationale for the develop- ment of CAR-NK cell approaches.14,15 Alloreactive NK cells can be expected to retain their innate anti-leukemic activity, with enhancement against CD38-positive cells conferred by an anti-CD38 CAR. Toxicity against normal cell populations can be minimized through the use of an
optimized-affinity CD38 CAR variant.11
While many target antigens are being considered in
AML, CD38 is also unique in the availability of a licensed and well-tolerated oral agent capable of modulating target antigen expression, ATRA.20 Furthermore, it has been shown that malignant blast cells are particularly sensitive to the CD38-inducing effect of ATRA, acting directly
AB
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Figure 3. CRISPR/Cas9 gene editing of CD38 in primary expanded natural killer cells to reduce natural killer cell fratricide upon CD38 CAR expression. (A) CD38 expression in freshly isolated (day 0), and expanded natural killer (eNK) cells at day 5 and day 13, as measured by flow cytometry and presented as a representative histogram and summary bar chart of three unique expansions. (B) Residual CD38 expression measured on day 8-10 after CRISPR/Cas9 gene editing of CD38. Dot plots from representative donor for mock-electroporated and CD38 knockdown (KD) conditions. Bar chart represents summary data for four donors. (C) Confirmatory CAR staining performed 18 h after CD38 CAR mRNA electroporation. Pseudo-colored plots depict results from one representative experiment. (D) NK cell death after 18 h of culture after CD38 CAR mRNA electroporation comparing CD38 KD and control eNK cells across three individual experiments and NK cell donors. Comparison of mean cell death by an unpaired t-test. (E) Histogram depicting a representative residual CD38 expression profile of viable CD38 KD eNK cells demonstrating loss of residual CD38-positive eNK cell population after CD38 CAR electroporation but not after ‘dummy’ mRNA (CD16) electroporation. EP: electroporated; H + L: heavy and light chain specific. Error bars indicate standard error of mean (SEM). Statistical significance is defined as *P≤0.05, **P≤0.01.
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haematologica | 2022; 107(2)