Effect of hypoxia on proliferation and glucocorticoid resistance of T-cell acute lymphoblastic leukaemia.

Objective: Hypoxia is emerging as a key factor in the biology of leukaemia. Here, we want to clarify the impact of hypoxia on the proliferation of T-cell acute lymphoblastic leukaemia (T-ALL) cells and the response to chemotherapy.
Methods: T-ALL cells were cultured under normoxic and hypoxic conditions. MTT assay and trypan blue staining technique was used to detect cell viability and proliferation. In vitro sensitivity to glucocorticoid was assessed by IC50. CDI was used to analyze the combined effects of glucocorticoid and hypoxia. Flow cytometry was performed to detect apoptosis and cell cycle. Western blotting was performed to detect the protein expression associated with hypoxia.
Results: Hypoxia of 1% O ₂ resulted different impact on cell viability and proliferation to different T-ALL cell lines, reduced, unaffected or induced, according to their different metabolic phenotype. All the cell lines showed an induction of key enzymes in glycolysis pathway following hypoxia exposure, although different effector proteins were induced in different cell lines. In GC-sensitive cells, acute hypoxia made no effect on the IC50 of dexamethasone, but chronic hypoxia may improve cell survival and induce GC resistance. However, acute hypoxia induced a higher GC resistance in GC-resistant T-ALL cells and showed an antagonistic effect while combined with high-dose dexamethasone.
Conclusion: T-ALL cells adapt well to hypoxic environment. Hypoxia may influence leukaemic cell proliferation. More importantly, hypoxia contributes to GC resistance in T-ALL blasts, especially in refractory/relapsed T-ALL.