Figure 1.
Insertion of ASS and OTC enzymes enhances CAR-T cell proliferation in vitro. Biochrom amino acid analysis of (A) AML (n = 10) and (B) neuroblastoma (n = 11) plasma samples revealing low concentrations of arginine, cysteine, methionine, a-amino-n-butyric, aspartic acid, citrulline, and taurine at diagnosis. (C) Plasma arginine levels at diagnosis are significantly lower than healthy controls in AML and solid pediatric cancer patients. (D) Schematic of CAR-T constructs containing the basic anti-XX-CAR scFv-CD8 hinge-41BB-CD3ζ in concert with ASS or OTC or ASS+OTC enzyme. A truncated CD34 is expressed for CAR-T identification and purification. (E) Western blot of ASS and OTC expression, with β-actin control, in control and modified anti-GD2-CAR-T cells posttransduction and expansion. (Representative of n = 7.) (F) ASS enzyme activity, measured by citrulline catabolism, is increased in ASS expressing CAR-T cells compared with controls. (G) OTC enzyme activity, measured by citrulline production, is increased in OTC expressing CAR-T cells compared with controls. (H) Highest proliferation of 2.5 × 106 modified anti-GD2-Jurkat CAR-T cell line following engraftment into NOG-SCID mice treated with recombinant human arginase (BCT-100, daily 50 mg/kg IV). (I) Proliferation of modified human CAR-T cells is significantly increased in low arginine media conditions, in vitro, as measured by flow cytometry after 72 hours. (J) Proliferation of modified anti-GD2 or anti-CD33-CAR-T cells is significantly increased in neuroblastoma (LAN-1 neuroblastoma or K562 AML, 72-hour conditioned supernatants) conditions, in vitro as measured by flow cytometry after 72 hours. (K) Expansion of modified CAR-T cells is enhanced in low arginine vs excess arginine (RPMI10%) conditions as measured by flow cytometry after 72 hours. (L) Liquid chromatography mass spectometry analysis of modified CAR-T cells after proliferation in low arginine conditions (72 hours) compared with each modified version. Heatmap demonstrating metabolomic changes in arginine and proline metabolism, pyrimidine metabolism, and purine metabolism pathways.