Genome-wide CRISPR/Ca9 screen was performed to identify genes essential for T-ALL survival, using KOPT-K1 cell line as the model system. Experimental procedure was based on previously published protocol(52 (link)) with minor modifications. Briefly, Cas9-expressing KOPT-K1 cells were first generated by lentiviral transduction, and single cell dilution was performed to develop and select clones with high level of Cas9 for genome-wide CRISPR screen. Cas9-expressing KOPT-K1 cells were transfected with the GeCKO V2 sgRNA library (Addgene, #1000000048) at low multiplicity of infection (0.3). Transfected cells were selected with puromycin for two days and then cultured for another 6 days to allow proliferation. Genomic DNA was extracted from surviving cells and sgRNAs were amplified by PCR followed by Illumina sequencing(53 ). The sgRNA enrichment was quantified based on read counts, and fold change from baseline (day 0) to day 6 was used for estimate gene dependency score(53 ).