Immunomodulatory drugs (IMiDs) are used in the treatment of hematological malignancies, especially multiple myeloma. IMiDs have direct anticancer effects but also indirect effects via cancer-supporting stromal cells. Monocytes are a stromal cell subset whose metabolism is modulated by the microenvironment, and they communicate with neighboring cells through extracellular release of soluble mediators. Toll-like receptor 4 (TLR4) is then a common regulator of monocyte metabolism and mediator release. Our aim was to investigate IMiD effects on these two monocyte functions. We compared effects of thalidomide, lenalidomide, and pomalidomide on in vitro cultured normal monocytes. Cells were cultured in medium alone or activated by lipopolysaccharide (LPS), a TLR4 agonist. Metabolism was analyzed by the Seahorse XF 96 cell analyzer. Mediator release was measured as culture supernatant levels. TLR4 was a regulator of both monocyte metabolism and mediator release. All three IMiDs altered monocyte metabolism especially when cells were cultured with LPS; this effect was strongest for lenalidomide that increased glycolysis. Monocytes showed a broad soluble mediator release profile. IMiDs decreased TLR4-induced mediator release; this effect was stronger for pomalidomide than for lenalidomide and especially thalidomide. To conclude, IMiDs can alter the metabolism and cell-cell communication of normal monocytes, and despite their common molecular target these effects differ among various IMiDs.

Monocytes are important for innate immunity and include the classical (CD14brightCD16negative), intermediate (CD14brightCD16dim) and non-classical (CD14dimCD16bright) monocyte subsets. The quantification of these functionally different subsets in peripheral blood may become useful for diagnosis and follow-up in human diseases. The aim of the present study was to investigate how different pre-analytical parameters influence analysis of monocyte subsets in peripheral blood samples.
We determined relative levels of monocytes and monocyte subsets by flow cytometry of peripheral blood samples derived from healthy individuals. A gating strategy exclusively extracting viable CD14+ monocytes and focusing on the three monocyte subsets was applied. We investigated the effects of (i) various anticoagulants (i.e. Li-Heparin, ACD-A, K2EDTA), (ii) insufficient filling of blood sampling tubes, (iii) cryopreservation. In addition, we analysed expression of the CCR2 chemokine receptor.
The relative numbers of CD14+ monocytes depended on the anticoagulant used, whereas the fraction of the three monocyte subsets did not. Insufficient filling of blood sampling tubes altered the relative levels of monocytes out of leukocytes, but not the relative levels of the monocyte subsets. Finally, the fraction of CD14+ monocytes out of isolated peripheral blood mononuclear cells was not significantly altered by cryopreservation, but the relative percentages of monocyte subsets was altered (similar effects for ACD-A and K2EDTA samples) and this was observed in correlation to a decreased CD16 expression.
Analysis of the monocyte subsets (i.e. classical, intermediate, non-classical) in peripheral blood samples requires a careful standardization of peripheral blood sampling and pre-analytic handling of the samples with respect to the anticoagulant used, filling of sample tubes, and cryopreservation of cells prior to analysis.
Copyright © 2018. Published by Elsevier B.V.