Inflammatory cytokines and signaling pathways are associated with survival of primary chronic lymphocytic leukemia cells in vitro: a dominant role of CCL2.
BACKGROUND
Chronic lymphocytic leukemia cells show prolonged survival in vivo, but rapidly die by spontaneous apoptosis in vitro, unless they are co-cultured with stromal cells or non-malignant leukocytes. The objective of this study was to characterize the survival-inducing cross-talk of chronic lymphocytic leukemia cells with their microenvironment to identify novel therapeutic targets.


METHODS
We analyzed and compared microarray-based expression profiles of chronic lymphocytic leukemia cells before and after three different survival-inducing culture conditions: (i) stromal cell co-culture, (ii) stromal cell conditioned medium and (iii) high cell density cultures of unsorted peripheral blood mononuclear cells. Cytokine antibody arrays were applied to study the composition of soluble factors present in these cultures.


RESULTS
The different survival-supportive culture conditions induced distinct gene expression changes, the majority of which were common to all three conditions. Pathway analyses identified - in addition to known signaling networks in chronic lymphocytic leukemia - novel pathways, of which Toll-like receptor signaling, nuclear respiratory factor-2 (NRF2)-mediated oxidative stress response, and signaling via triggering receptor expressed on myeloid cells-1 (TREM1) were the most relevant. A high proportion of up-regulated genes were inflammatory cytokines, of which chemokine (C-C motif) ligand 2 (CCL2) was shown to be induced in monocytes by the presence of chronic lymphocytic leukemia cells in vitro. In addition, increased serum levels of this chemokine were detected in patients with chronic lymphocytic leukemia.


CONCLUSIONS
Our data provide several lines of evidence that an inflammatory microenvironment is induced in survival-supportive cultures of chronic lymphocytic leukemia cells which might be directly or indirectly involved in the prolonged survival of the malignant cells.
German Cancer Research Center, Dept. for Molecular Genetics, Im Neuenheimer Feld 280, 69120 Heidelberg, Germany.
Angela
A
Schulz
Grischa
G
Toedt
Thorsten
T
Zenz
Stephan
S
Stilgenbauer
Peter
P
Lichter
Martina
M
Seiffert
D017209:Apoptosis / Q000235:genetics / Q000276:immunology; D016022:Case-Control Studies; D002450:Cell Communication; D002452:Cell Count; D018929:Cell Culture Techniques; D002470:Cell Survival; D018932:Chemokine CCL2 / Q000235:genetics / Q000378:metabolism*; D018920:Coculture Techniques; D017077:Culture Media, Conditioned / Q000378:metabolism; D016207:Cytokines / Q000276:immunology / Q000378:metabolism; D051268:GA-Binding Protein Transcription Factor / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression; D006801:Humans; D007249:Inflammation / Q000378:metabolism; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D007963:Leukocytes, Mononuclear / Q000378:metabolism* / Q000473:pathology; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism; D018384:Oxidative Stress / Q000235:genetics / Q000276:immunology; D040081:Protein Array Analysis; D011971:Receptors, Immunologic / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics; D017154:Stromal Cells / Q000166:cytology / Q000378:metabolism; D000073871:Triggering Receptor Expressed on Myeloid Cells-1; D059016:Tumor Microenvironment
C111835:CCL2 protein, human; D018932:Chemokine CCL2; D017077:Culture Media, Conditioned; D016207:Cytokines; D051268:GA-Binding Protein Transcription Factor; D008562:Membrane Glycoproteins; D011971:Receptors, Immunologic; C408842:TREM1 protein, human; D000073871:Triggering Receptor Expressed on Myeloid Cells-1