Cell passaging rapidly affects expression, secretion and activity of MMP9 as well as mobility of HL60 leukemia cells

The HL60 cell line, derived from acute promyelocytic leukemia cells, can differentiate into neutrophil-like cell following DMSO treatment. Mobility of HL60, or DMSO-differentiated HL60 cells (≠HL60), requires surface expression of adhesion molecules and production of matrix metalloproteinases (MMPs). The aim of this study was to investigate in HL60 and ≠HL60 the effects of cell passaging (over 5 passages after delivery (P and P+5)) on i) surface expression of adhesion molecule CD11b, which is considered a neutrophil differentiation marker ii) MMP9 mRNA expression, protein release and zymographic activity and iii) cellular mobility. As expected, CD11b expression at both cell passages increased in ≠HL60 relative to undifferentiated HL60, but expression levels of this neutrophils marker did not change over 5 passages. MMP9 mRNA expression however, in basal conditions was increased in HL60 at P+5. At P+5 versus P, MMP9 protein levels, MMP9 zymographic activity and cellular mobility in HL60 and ≠HL60 were elevated. Stimulation by N-formyl-L-Methionyl-L-Leucyl-L-Phenylalanine had no effects on HL60, but raised MMP9 protein concentration and zymographic activity in ≠HL60. Since passage history is likely to also influence cellular functions other than MMP-related effects, it is important to carefully consider passage numbers when designing experiments