VEGF/KDR loop is a target of AG1296 in acute myeloid leukaemia showing FLT3-internal tandem duplications

Quercetin Induces Apoptosis via Downregulation of Vascular Endothelial Growth Factor/Akt Signaling Pathway in Acute Myeloid Leukemia Cells

Acute myeloid leukemia (AML) is an aggressive haematological malignancy characterized by highly proliferative accumulation of immature and dysfunctional myeloid cells. Quercetin (Qu), one kind of flavonoid, exhibits anti-cancer property in multiple types of solid tumor, but its effect on acute myeloid leukemia is less studied, and the underlying mechanisms still largely unknown. This study aimed to explore the specific target and potential mechanism of quercetin-induced cell death in AML. First, we found that quercetin induces cell death in the form of apoptosis, which was caspase dependent. Second, we found that quercetin-induced apoptosis depends on the decrease of mitochondria membrane potential (MMP) and Bcl-2 proteins. With quantitative chemical proteomics, we observed the downregulation of VEGFR2 and PI3K/Akt signaling in quercetin-treated cells. Consistently, cell studies also identified that VEGFR2 and PI3K/Akt signaling pathways are involved in the action of quercetin on mitochondria and Bcl-2 proteins. The decrease of MMP and cell death could be rescued when PI3K/Akt signaling is activated, suggesting that VEGFR2 and PI3K/Akt exert as upstream regulators for quercetin effect on apoptosis induction in AML cells. In conclusion, our findings from this study provide convincing evidence that quercetin induces cell death via downregulation of VEGF/Akt signaling pathways and mitochondria-mediated apoptosis in AML cells.

Redistribution, homing and organ-invasion of neoplastic stem cells in myeloid neoplasms

The development of a myeloid neoplasm is a step-wise process that originates from leukemic stem cells (LSC) and includes pre-leukemic stages, overt leukemia and a drug-resistant terminal phase. Organ-invasion may occur in any stage, but is usually associated with advanced disease and a poor prognosis. Sometimes, extra-medullary organ invasion shows a metastasis-like or even sarcoma-like destructive growth of neoplastic cells in local tissue sites. Examples are myeloid sarcoma, mast cell sarcoma and localized blast phase of chronic myeloid leukemia. So far, little is known about mechanisms underlying re-distribution and extramedullary dissemination of LSC in myeloid neoplasms. In this article, we discuss mechanisms through which LSC can mobilize out of the bone marrow niche, can transmigrate from the blood stream into extramedullary organs, can invade local tissue sites and can potentially create or support the formation of local stem cell niches. In addition, we discuss strategies to interfere with LSC expansion and organ invasion by targeted drug therapies.

VEGFR2-Mediated Reprogramming of Mitochondrial Metabolism Regulates the Sensitivity of Acute Myeloid Leukemia to Chemotherapy

Metabolic reprogramming is central to tumorigenesis, but whether chemotherapy induces metabolic features promoting recurrence remains unknown. We established a mouse xenograft model of human acute myeloid leukemia (AML) that enabled chemotherapy-induced regressions of established disease followed by lethal regrowth of more aggressive tumor cells. Human AML cells from terminally ill mice treated with chemotherapy (chemoAML) had higher lipid content, increased lactate production and ATP levels, reduced expression of peroxisome proliferator-activated receptor gamma coactivator 1α (PGC-1α), and fewer mitochondria than controls from untreated AML animals. These changes were linked to increased VEGFR2 signaling that counteracted chemotherapy-driven cell death; blocking of VEGFR2 sensitized chemoAML to chemotherapy (re-)treatment and induced a mitochondrial biogenesis program with increased mitochondrial mass and oxidative stress. Accordingly, depletion of PGC-1α in chemoAML cells abolished such induction of mitochondrial metabolism and chemosensitization in response to VEGFR2 inhibition. Collectively, this reveals a mitochondrial metabolic vulnerability with potential therapeutic applications against chemotherapy-resistant AML.Significance: These findings reveal a mitochondrial metabolic vulnerability that might be exploited to kill chemotherapy-resistant acute myeloid leukemia cells. Cancer Res; 78(3); 731-41. ©2017 AACR.

Immunophenotypic features of acute myeloid leukaemia patients exhibiting high FLT3 expression not associated with mutations

FMS-related tyrosine kinase 3 (FLT3) mutations are found in 30% of cases of acute myeloid leukaemia (AML). In addition, recent studies have lead to the identification of about 10-15% of AML patients displaying high expression of FLT3, not associated with mutations of the receptor (FLT3 Wild-type High, FLT3WTH). These AMLs, as well as those displaying internal tandem duplication (ITD) are associated with an unfavourable prognosis. However, the biological features of these AMLs are poorly characterized. The present study explored the immunophenotypic features of FLT3WTH AMLs in 94 de novo cases of AML. The levels of FLT3 expression, as assessed by flow cytometry and FLT3 mutational status, was used to identify four AML subgroups: FLT3WTH (14/94); FLT3 Wild-type low (FLT3WTL, 48/94); FLT3 internal tandem duplication (FLT3ITD 26/94); FLT3 aspartic acid 835 (FLT3D835, 6/94). FLT3WTH and FLT3ITD were characterized by: high white blast cell counts; predominance of M4 and M5 French-American-British classification subtypes and associated expression of myelo-monocytic markers; high expression of CD123 and TRAIL-Rs; high expression of receptors for angiogenic growth factors. Addition of FLT3 Ligand to human CD34(+) or monocytic cells stimulated CD123 and TRAIL-R expression. These findings are of potential value for the development of new therapeutic strategies.