No abstract

Macrophages are key mediators of the therapeutic effects exerted by monoclonal antibodies, such as the anti-CD38 antibody MOR202, currently introduced in multiple myeloma (MM) therapy. Therefore, it is important to understand how antibody-mediated effector functions of myeloma-associated macrophages (MAMs) are regulated. Here, we focused on the effects of vitamin D, a known regulator of macrophage effector functions. Consequently, it was the aim of this study to assess whether modulation of the vitamin D pathway alters the tumoricidal activity of MAMs. Here, we demonstrate that MAMs display a defective vitamin D pathway with reduced expression level of CYP27B1 and limited tumoricidal activity which can be restored by the IMiD lenalidomide in vitro. Furthermore, our data indicate that the vitamin D pathway of MAMs from MM patients does recover during an IMiD-containing therapy shown by an improved MOR202-mediated cytotoxic activity of these MAMs against primary MM cells ex vivo. Here, the ex vivo cytotoxic activity could be further enhanced by vitamin D supplementation. These data suggest that vitamin D holds a key role for the effector functions of MAMs and that vitamin D supplementation in IMiD combination trials could further increase the therapeutic efficacy of anti-CD38 antibodies such as MOR202, which remains to be investigated in clinical studies.

No abstract

In addition to antimicrobial activity, macrophages regulate tissue development, remodeling, and repair. In terms of neoplastic growth, tumor-associated macrophages (TAMs) are even considered pro-tumorigenic based on their angiogenic and T-cell suppressive properties. In multiple myeloma (MM) macrophages represent an abundant component of the stromal cell compartment and are believed to support proliferation, survival, and drug resistance of MM cells. Those pro-tumorigenic functions are partly instructed by T-helper (TH)-2 cytokines such as interleukin-4 (IL-4) and IL-10, which skew TAM differentiation towards an alternatively activated, or so-called M2-like, phenotype. In contrast, M1 macrophages generally considered as potent effectors in response to microbial products or interferon-γ (IFN-γ), are characterized by superior antigen-presentation, abundant production of pro-inflammatory cytokines such as interleukin-12 (IL-12), and consequently, promote a polarized type I immune response against infections as well as malignant cells. Transcriptional regulation is a key determinant for macrophage polarization. The Ikaros (IKZF1) transcription factor is critical for lymphoid development and is found in all hematopoietic progenitors as well as in T-, B-, NK-cells and macrophages. Interestingly, IKZF1 is overexpressed in MM and selectively degraded by lenalidomide, which is approved in MM therapy. The potential role of IKZF1 in modulating macrophage polarization has not been elucidated yet. Here, we show that IKZF1expression is found highly elevated in M2-like macrophages and in MM TAMs. IKZF1 deletion in human macrophages by small interfering RNA (siRNA) or by lenalidomide yields an upregulation of M1-specific cytokines (IL-12 and IL-1b), chemokines (CXCL10 and CCL5), and costimulatory molecules (CD86 and CD40) and leads to a potent TH1-TH17 response. In fact, lenalidomide-pretreated macrophages display strong tumoricidal effects when co-cultured with MM cell lines as opposed to their untreated counterparts promoting MM proliferation and viability. Utilizing immunoprecipitation-sequencing (ChIP-Seq) we reveal that IKZF1 governs IRF4 and IRF5 expression in human macrophages. Recent studies demonstrate that IRF4 controls M2 macrophage polarization, while IRF5 regulates the M1 phenotype respectively. We could show that a lenalidomid-mediated M1-phenotype induction is efficiently abrogated by IRF4 overexpression or IRF5 silencing. Overall, these findings unravel a novel role for IKZF1 in orchestrating macrophage polarization via the IRF4/IRF5 pathway. Disclosures No relevant conflicts of interest to declare.

Zusammenfassung Bei den Untersuchungen wurden folgende Ergebnisse erzielt: Der Vitamin‐E‐Gehalt im Plasma der Vitamin‐E‐arm ernährten Muttersauen zeigt bei hohem Ausgangsniveau im Verlauf der Gravidität eine sinkende Tendenz. Liegen niedrige Werte zu Versuchsbeginn vor, wird keine Veränderung des Vitamin‐E‐Gehaltes deutlich. Im Kolostrum der Vitamin‐E‐depletierten Sauen werden nur etwa 15 % des Wertes der Kontrolltiere nachgewiesen, im Fettgewebe sogar nur etwa 3%. Bei den Ferkeln ergeben sich direkt nach der Geburt vor der Kolostrumaufnahme keine Differenzen im Vitamin‐E‐Gehalt von Plasma, Leber, Herz‐und Skelettmuskulatur zwischen Versuchs‐ und Kontrollgruppe. Nach der Aufnahme von Kolostrum bleibt der Vitamin‐E‐Status bei Ferkeln depletierter Sauen im wesentlichen unverändert, während bei den Kontrollferkeln ein z. T. beträchtlicher Anstieg des Vitamin‐E‐Gehaltes vor allem in der Leber zu verzeichnen ist. Offensichtlich ist für die Vitamin‐E‐Versorgung neugeborener Ferkel weniger der diaplazentare Transport als vielmehr der Gehalt von Vitamin E im Kolostrum von entscheidender Bedeutung. Summary Studies on the effect of vitamin E deficient diet in sows during pregnancy on the vitamin E status of newborn piglets The studies provided the following conclusions: The vitamin E content of plasma in sows fed a diet deficient in vitamin E showed during pregnancy a fall below the original level. When the initial level was low there was no clear change in the vitamin E level. In colostrum of vitamin E depleted sows the level was only 15 % of that of control sows and in adipose tissue the level was only around 3 %. In piglets immediately after birth and before ingestion of colostrum there was no difference in vitamin E content in plasma, liver or cardiac and skeletal muscle between experimental and control groups. After ingestion of colostrum the vitamin E status of piglets from depleted sows remained almost unchanged, whereas that of the control piglets showed a marked rise in vitamin E content, especially in the liver. It would appear that the vitamin E needs of newborn piglets are met less by transplacental transport than by the vitamin E level in the colostrum — the latter is the more important source. Résumé Recherches sur l'influence d'une nourriture pauvre en vitamine E chez des truies durant la gestation sur le statut de la vitamine E des porcelets durant la période néonatale Le taux de vitamine E dans le plasma des truies recevant un aliment pauvre en vitamine E a montré une tendance à la diminution dans les valeurs élevées durant la gestation. En ce qui concerne les valeurs faibles, il n'y a pas eu de modification du taux en vitamine E au début de l'essai. On a mis seulement en évidence le 15 % de la valeur dans le colostrum des truies carencées alimentairement par rapport aux témoins et même seulement 3 % dans le tissu graisseux. Il n'y a pas eu de différence pour le taux en vitamine E dans le plasma, le foie, le myocarde et la musculature du squelette entre les animaux de l'essai et les témoins pour les porcel...