General anaesthetics reduce acute lymphoblastic leukaemia malignancies in vitro and in vivo via CXCR4 and osteopontin mediated mechanisms

Background: Acute lymphoblastic leukaemia (ALL) is the most common type of cancer in children. General anaesthetics are often used on patients undergoing painful procedures during ALL treatments but their effects on ALL malignancy remain unknown. Herein, we aim to study the effect of two commonly used general anaesthetics, intravenous propofol and inhalational sevoflurane, on the migration,homing and chemoresistance of ALL cells in vitro and in vivo.

Methods: NALM-6 and Reh cells were treated with propofol (5 and 10 μg/ml) or sevoflurane (3.6%) in vitro for six hours. Then, cells were harvested for flow cytometry analysis. For in vitro migration experiments, NALM-6 and Reh cells were pre-treated with propofol and sevoflurane for six hours before being loaded onto the upper chamber of a migration chamber and cells were collected in the lower chamber after six hours of migration. For in vitro adhesion assays, NALM-6 cells were pre-treated with propofol and sevoflurane before an adhesion assay was carried out. In in vivo experiments, GFP-NALM-6 cells were pre-treated with propofol (10 μg/ml) or sevoflurane (3.6%) for six hours. Then, cells were injected intravenously to C57BL/6 female mice followed by intravital microscopy. Both cell lines were treated with rising concentrations of Ara-c (0.05-50 nM) plus 10µg/ml (56μM) of propofol or Ara-C (0.05-50 nM) plus 3.6% of sevoflurane (MAC 2.0) for 4 hours, followed by the assessment of cell viability via CCK-8 assay and detection of autophagy influx via flow cytometry

Results: Both anaesthetics reduced in vitro migration, in vivo migration and in vivo homing as exemplified by 1) the reduction in the number of cells entering the bone marrow and 2) the disturbance in homing location in relation to the nearest endosteal surface. Our results indicated that general anaesthetics reduced the surface CXCR4 expression. In addition, the adhesion of leukaemia cells to thrombin cleaved osteopontin (OPN) was reduced by general anaesthetics. Those changes might result in the alterations in migration and homing. In addition, both anaesthetics sensitized ALL cells to chemotherapeutic agent Ara-c. Propofol but not sevoflurane enhanced chemo-related cell death via inducing cytotoxic autophagy.

Conclusion: Together, our data suggest that both propofol and sevoflurane could reduce ALL migration, and homing in vivo and in vitro via CXCR4 and OPN mediated mechanisms. Additionally, both anaesthetics might sensitise ALL cells to chemotherapy via CXCR4 mediated mechanism.