Microenvironment alterations after arsenic trioxide treated in acute promyelocytic leukemia murine models revealed by single-cell RNA sequencing

The human APL cell line NB4 (ATCC® CRL-2047™) was cultured in RPMI-1640 medium (Gibco, Thermo Fisher Scientific, Waltham, MA, USA) supplemented with 10% fetal bovine serum (FBS; Gibco), 100 U/mL penicillin, and 100 µg/mL streptomycin in a humidified 5% CO2 incubator at 37°C. Arsenic trioxide (ATO; GBW08666, National Institute of Metrology, Beijing, China) was dissolved in sterile phosphate-buffered saline (PBS) to prepare working solutions for in vivo administration. To establish a reproducible human APL xenograft model, six-week-old specific-pathogen-free (SPF) female NCG mice (NOD-Prkdc^em26 Il2rg^em26/Gpt, GemPharmatech Co., Ltd., Nanjing, China) were selected. NCG mice represent a severely immunodeficient strain lacking mature T, B, and functional NK cells, enabling robust human leukemic cell engraftment without pre-conditioning irradiation. Mice were intravenously injected via the tail vein with 5 × 10^6 NB4 cells suspended in 200 µL of PBS to initiate leukemogenesis, as previously described. At 14 days post-transplantation, mice were randomly assigned into two cohorts (n = 3 per group). The therapeutic cohort received daily intraperitoneal (i.p.) injections of ATO at a dosage of 1 mg/kg/day for 14 consecutive days (Days 14–27 post-transplantation). Control APL mice were administered volume-matched vehicle PBS via the same i.p. route and schedule. All animals were monitored daily for health status and leukemic disease burden.