LIX: a chemokine with a role in hematopoietic stem cells maintenance.

LIX is a chemokine usually associated with cell migration and activation in neutrophil. While using a microarray approach to dissect the hematopoietic microenvironment, we have discovered that LIX is also expressed in the hematopoietic stromal cells and its expression is associated with hematopoietic supportive phenotypes. LIX microarray profiles were verified using reverse transcription and semi-quantitative polymerase chain reaction. We subsequently tested the effects of LIX on the primary bone marrow derived lineage depleted (Lin(-)) cells. LIX was found to increase the number of long-term culture-initiating cells by 34% (from 1 in 342 to 1 in 255 of Lin(-) cells). LIX also increased the clonogenicity of the long-term culture Lin(-) cells by 2-fold (p=0.029 ). When compared to untreated EML hematopoietic progenitor cell line, LIX was found to increase the level of DNA synthesis in EML cells significantly (1.63-fold; 0.010p=), with a corresponding increase in viable cell number by 1.11-fold 96 h after seeding. Similar effect was not observed with the M1 mature myeloid leukemia cell line or with the MS5.1 and AFT024 stromal cell lines. This suggested that the proliferative effect of LIX is specific towards the primitive hematopoietic cells.