PFKFB4 is critical for the survival of acute monocytic leukemia cells.

Acute myeloid leukemia (AML), which is characterized by an overproliferation of blood cells, is divided into several subtypes in adults and children. Of those subtypes, acute monocytic leukemia (M4/M5, AMoL) is reported to be associated with abnormal gene fusions that result in monocytic cell differentiation being blocked. However, few studies have shown a relationship between cellular metabolism and the initiation of AMoL. Here, we use the open-access database TCGA to analyze the expression of enzymes in the metabolic cycle and find that PFKFB4 is highly expressed in AMoL. Subsequently, knocking down PFKFB4 in THP-1 and U937 cells significantly inhibits cell growth and increases the sensitivity of cells to chemical drug-induced apoptosis. In line with the gene-editing alterations, treatment with a PFKFB4 inhibitor exhibits similar effects on THP-1 and U937 proliferation and apoptosis. In addition, we find that PFKFB4 functions as a reliable target of the epigenetic regulator MLL, which is a well-known modulator in AMoL. Mechanistically, MLL promotes PFKFB4 expression at the transcriptional level through the putative E2F6 binding site in the promoter of the pfkfb4 gene. Taken together, our results suggest PFKFB4 serves as a downstream target of MLL and functions as a potent therapeutic target in AMoL.

Comparison of the proliferation, cytotoxic activity and cytokine secretion function of cascade primed immune cells and cytokine-induced killer cells in vitro.

The present study aimed to compare the antitumor effects of cascade primed immune (CAPRI) cells and cytokine-induced killer (CIK) cells in vitro, through investigating cell morphology, proliferation, cytotoxic activity to tumor cells and the ability of these cells to secrete cytokines. Peripheral blood samples (50 ml) were obtained from three healthy volunteers and peripheral blood mononuclear cells (PBMCs) were obtained from each via Ficoll-Conray density gradient centrifugation. Each suspension of PBMCs (1 x 10(6)/ml) was divided into two parts; CAPRI cells were obtained from one part through a series of induction, amplification and cytokine cultures, while CIK cells were obtained from the other part through induction with different cytokines. During the culture process, the proliferation and morphological changes were observed for the two cell types using Trypan blue staining. At day 14, the cytotoxic activity of the two cell types was examined through determining lactate dehydrogenase release in the presence of K562 leukemia cells and MCF-7 breast cancer cells. In addition, secretory levels of interferon (IFN)-γ and interleukin (IL)-2 were detected using enzyme-linked immunospot (ELISPOT) technology. The results revealed that at day 5 and 14 of culture, there were significantly fewer CAPRI cells compared with CIK cells (P<0.001), although the survival rate of each cell type was >95%. The cytotoxic activity of CAPRI cells towards the K562 cell line was effector-target ratio-dependent (40:1 and 20:1) with values of 55.1 ± 3.25 and 35.0 ± 2.65%, respectively, which were significantly reduced compared with the corresponding data in CIK cells, 60.0 ± 3.03 and 39.7 ± 3.42% (P=0.004 and 0.005, respectively). Furthermore, the cytotoxic activity of CAPRI cells towards MCF-7 cells were 71.5 ± 3.06, 56.0 ± 3.76 and 40.2 ± 2.90% at effector-target ratios 40:1, 20:1 and 10:1, respectively. These data were significantly higher than the corresponding values in CIK cells, 65.4 ± 3.86, 49.5 ± 3.91 and 36.1 ± 3.73% (P=0.002, 0.003 and 0.02, respectively). As determined using ELISPOT technology at different cell concentrations (1 x 10(6)/ml and 5 x 10(5)/ml), IFN-γ secretion levels, determined by the number of spot-forming cells, of CAPRI cells were 126.2 ± 10.31 and 48.8 ± 10.99, respectively, which were significantly reduced compared with those of CIK cells, 409.3 ± 7.76 and 159.3 ± 15.45, respectively (P<0.001). IL-2 secretion levels in CAPRI cells were 325.1 ± 16.24 and 113.8 ± 11.29 at 1 x 10(6)/ml and 5 x 10(5)/ml, respectively, which were significantly increased compared with CIK cells, 212.0 ± 16.58 and 70.7 ± 10.57, respectively (P<0.001). In conclusion, the present study demonstrated that CAPRI cells had a reduced proliferation rate compared with CIK cells as well as a less potent cytotoxic effect on K562 cells; however, the two cell types had potent cytotoxic activity towards solid tumor MCF-7 cells. In addition, CAPRI cells secreted lower levels of IFN-γ and increased levels of IL-2 compared with CIK cells. These results indicated that antitumor activities of CAPRI and CIK cells proceeded via different mechanisms.