Control of brain tumor growth by reactivating monocytes and macrophages with niacin

We have found that innate immune cells (monocytes/macrophages) are compromised in malignant glioma, and we have determined that vitamin B3 (niacin) reactivates and/or reprograms monocytes/macrophages to inhibit glioma growth, particularly by suppressing the growth of brain tumor initiating cells (BTICs). To this end, we sought to obtain insights into the mechanisms by which niacin regulates monocyte/macrophage activity to alter glioma growth. Analysis of the microarray data identified several genes that were differentially altered in niacin-treated monocytes that could regulate BTIC growth. The study has identified a mechanistic basis for the regulation of glioma growth with niacin treatment. Monocytes were isolated from the blood of three normal adult individuals. Each set of monocytes was treated with niacin (100 μM) for 6h in serum free BTIC medium, or were left untreated as control. After 6h, RNA was extracted using RNeasy MiniKit (Qiagen) as per manufacturer’s instruction, and subjected to microarray analysis. Thus, there were 3 separate sets of monocytes, each with control or niacin groups.