Characterization of a novel glucocorticoid-resistant human B-cell acute lymphoblastic leukemia cell line, with AMPK, mTOR and fatty acid synthesis pathway inhibition.

Background: Acquired glucocorticoid (GC) resistance remains the main obstacle in acute lymphoblastic leukemia (ALL) therapy. The aim of the present study was to establish a novel GC-resistant B-ALL cell line and investigate its biological characteristics. Methods: A cell culture technique was used to establish the GC-resistant cell line from the parental cell, NALM-6. Molecular and cellular biological techniques including flow cytometry, MTT assay, western blotting, DNA fingerprinting analysis and whole transcriptome sequencing (WTS) were used to characterize the GC-resistant cell lines. Nude mice were used for xenograft studies. Results: The GC-resistant cell line, NALM-6/HDR, was established by culturing NALM-6 cells under hypoxia for 5 weeks with a single dexamethasone (Dex) treatment. We subcloned the NALM-6/HDR cell lines, and got 6 monoclone Dex-resistant cell lines, NALM-6/HDR-C1, C3, C4, C5, C6 and C9 with resistance index (RI) ranging from 20,000–50,000. NALM-6/HDR and its monoclone cell line, NALM-6/HDR-C5, exhibited moderate (RI 5–15) to high resistance (RI > 20) to Ara-c; low or no cross-resistance to L-Asp, VCR, DNR, and MTX (RI < 5). STR analysis confirmed that NALM-6/HDR and NALM-6/H were all derived from NALM-6. All these cells derived from NALM-6 showed similar morphology, growth curves, immunophenotype, chromosomal karyotype and tumorigenicity. WTS analysis revealed that the main metabolic differences between NALM-6 or NALM-6/H (GC-sensitive) and NALM-6/HDR (GC-resistant) were lipid and carbohydrates metabolism. Western blotting analysis showed that NALM-6/HDR cells had a low expression of GR and p-GR. Moreover, AMPK, mTORC1, glycolysis and de novo fatty acid synthesis (FAS) pathway were inhibited in NALM-6/HDR when compared with NALM-6. Conclusions: NALM-6/HDR cell line may represent a subtype of B-ALL cells in patients who acquired GC and Ara-c resistance during the treatment. These patients may get little benefit from the available therapy target of AMPK, mTORC1, glycolysis and FAS pathway. [ABSTRACT FROM AUTHOR]

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