Up-Regulation of Prok-2 in Granulocytes Is Present BOTH in MGUS and MM

Introduction

Our previous work showed that in Multiple Myeloma (MM) the immune function is impaired, including immunosuppressive properties of granulocytes due to their increased amount of arginase-1 and reduced phagocytic activity (Parrinello, manuscript in preparation). It is currently unknown if granulocyte dysfunction occurs in progression from MGUS to MM.

Aim

Providing a gene expression profile of mature granulocytes isolated from peripheral blood at the steady-statein MGUS and MM.

Methods

Using oligonucleotide microarrays we first evaluated the gene expression profile of granulocytes at the steady state in 5 MM, 3 MGUS and 3 healthy subjects matched for sex and age.

Then, we validated the first up-regulated gene PROK-2, obtained from preliminary findings in granulocytes from peripheral blood in 85 consecutive newly diagnosed MGUS (N=45), MM (N=40) and 15 healthy subjects, in RT-PCR (validation set).

Results

We found 708 genes differentially expressed (467 up- and 241 down regulated) in MGUS versus healthy granulocytes at the steady state. The set of annotated, differentially expressed genes could befunctionally organized by “gene ontology” (http://www.geneontology.org/) into the following major categories:

i) receptors and signal transduction (including up-regulation of CD14, Toll-like receptor 5 (TLR-5), IL-7 Receptor (CD127), IL-11 receptor, TGF-beta receptor 2, hematopoietic cells kinase (HCK), IFNAR1);

ii) negative regulation of adaptive immune response (including up regulation of CD127, STAT6, IFNAR1, OSCAR, PROK-2 and down regulation of p50, p65,NFKBIA, IL8, ELK-1, HIF-1 alpha, CEBP-beta, CEBP-zeta).

In MM samples we confirmed a statistically significant up-regulation of PROK-2 (a key molecule of VEGF-independent angiogenesis), CD14 (mediator hypersensitive innate immune response to lipopolysaccharide) and HCK (the hematopoietic cell kinase, involved in neutrophil migration and degranulation).

In the validation set, PROK-2 expression was two times higher in MGUS than healthy subjects (p=.02) and up to ten times higher in MM (p=.001). In MM patients, increased levels of PROK-2 were positively associated with advanced bone disease and unfavourable cytogenetics.

Conclusion

Granulocytic impairment is present in MGUS and worsened in MM patients due to increased expression of genes that negatively regulate adaptive immune response. PROK-2 is a key molecule involved in the granulocyte dysfunction and could be involved in the progression from MGUS to MM.