Establishment and characterization of a novel childhood acute lymphoblastic leukemia cell line, HXEX-ALL1, with chromosome 9p and 17p deletions

BACKGROUND: Although contemporary chemotherapy has improved the cure rate of childhood acute lymphoblastic leukemia (ALL) to nearly 90%, relapsed/refractory ALL is still a leading cause of tumor-related death in children. To clarify the underlying mechanisms of relapsed/refractory childhood ALL, researchers urgently need to establish novel cell models from patients with relapsed ALL after treatment with contemporary chemotherapy. METHODS: Cell culture technique was used to establish the HXEX-ALL1 cell line from primary B cell precursor ALL (BCP-ALL) cells. Molecular and cellular biological techniques including flow cytometry, polymerase chain reaction (PCR), short tandem repeat (STR) analysis, conventional cytogenetics, and chromosomal microarray analysis (CMA) were used to characterize the HXEX-ALL1 cell line. Nude mice were used for xenograft studies. RESULTS: A stable ALL cell line, HXEX-ALL1, derived from a 6-year-old boy of Han nationality with BCP-ALL at the second relapse, was established and maintained in culture for more than 18 months. The HXEX-ALL1 cell line was authenticated as being derived from primary leukemia cells based on morphologic, immunophenotypic, cytogenetic and STR analyses and demonstrated tumorigenicity in nude mice. WGS data showed that there were 27,006 novel single nucleotide polymorphisms (SNPs) and 193,951 novel insertion/deletions (InDels) in HXEX-ALL1 cells. Compared with the other BCP-ALL cell lines in use, the HXEX-ALL1 cells have a special karyotype represented by trisomy 8 and 9p and 17p deletions with a multidrug resistance phenotype, especially highly resistant to asparaginase. CONCLUSIONS: The HXEX-ALL1 cell line may prove to be a useful model for the study of relapsed/refractory childhood ALL, particularly for the researches on asparaginase resistance.