Prognostic value, biological role, and mechanisms of LCN2 in childhood acute lymphoblastic leukemia

Resistance to glucocorticoids (GC) is associated with poor prognosis in childhood acute lymphoblastic leukemia (ALL). Lipocalin 2 (LCN2) plays a pro-tumorigenic role in solid tumors and chronic myeloid leukemia by promoting initiation, invasion, metastasis and drug resistance, and has gained increasing attentions as a therapeutic target. However, ALL cells show a low expression status of LCN2. Meanwhile, the clinical significance and biological role of LCN2 remain unclear in childhood ALL. Therefore, we collected bone marrow, peripheral blood, and cerebrospinal fluid samples from children with ALL and control individuals to assess LCN2 expression. Lentiviral transduction was used to establish stable LCN2 overexpression in Nalm6, CEM-C1, CEM-C7, and Molt4 cell lines. The cell growth, proliferation, cell cycle, apoptosis, ferroptosis, and sensitivity to dexamethasone were detected to clarify the function of LCN2. Compared with healthy individuals, non-tumor patients and intracranial solid tumors, LCN2 expression was down-regulated in patients with childhood ALL at diagnosis. Lower LCN2 expression in the bone marrow was associated with poor prognostic features and a lower disease relapse-free rate. Effective chemotherapy could restore the expression of LCN2. Overexpression of LCN2 led to an inhibition of cell growth and an induction of ferroptosis in GC sensitive ALL cells (Nalm6 and CEM-C7), and reversed GC resistance by up-regulating the expression of glucocorticoid receptor (GR) and phosphorylated-GR (p-GR) and inhibiting the Notch signaling pathway. On the contrary to solid tumors, our results suggest that inducing the expression of LCN2 might be a novel therapeutic protocol in childhood ALL.