AML1-ETO interacts with Sp1 and antagonizes Sp1 transactivity through RUNT domain

AML1-ETO fusion protein is observed in approximately 12% of acute myeloid leukemia. In the present research, we found that AML1-ETO is able to inhibit Sp1 transactivity. We also found that this inhibition of Sp1 transactivity by AML1-ETO is achieved by interaction between Sp1 and RUNT domain of AML1. AML1b is able to abrogate the inhibition of AML1-ETO. Since Sp1 is involved in hematopoietic cell differentiation, we proposed that AML1-ETO promotes leukemogenesis by blocking cell differentiation through inhibition of Sp1 transactivity.     

Reduced expression of SRC family kinases decreases PI3K activity in NBS1-/- lymphoblasts

SRC family kinases (SFKs) are involved in the activation of phosphatidylinositol-3-kinase (PI3K). In addition, the activity of this lipid kinase can be regulated by the DNA repair protein NBS1. Here, we describe a disturbed expression of some members of the non-receptor tyrosine kinase family in lymphoblastoid cell lines generated from cells of Nijmegen breakage syndrome (NBS) patients. Especially, only minor amounts of the kinases LCK and HCK are expressed in the NBS1^−/− cell lines as compared to the consanguineous NBS1^+/− cells. We demonstrate that SFK activity is important for a proper activation of PI3K in these cells and that it is reduced in NBS1^−/− cells. We provide evidence that the observed reduced PI3K activity in NBS lymphoblasts is caused by an impaired expression of the SFKs LCK and/or HCK. Thus, our data establish a new function for the NBS1 protein as a regulator of PI3K activity via SFK members.     

Hematopoietic cell kinase enhances osteosarcoma development via the MEK/ERK pathway

Osteosarcoma (OS) is a sarcoma with high rates of pulmonary metastases and mortality. The mechanisms underlying tumour generation and development in OS are not well-understood. Haematopoietic cell kinase (HCK), a vital member of the Src family of kinase proteins, plays crucial roles in cancer progression and may act as an anticancer target; however, the mechanism by which HCK enhances OS development remains unexplored. Therefore, we investigated the role of HCK in OS development in vitro and in vivo. Downregulation of HCK attenuated OS cell proliferation, migration and invasion and increased OS cell apoptosis, whereas overexpression of HCK enhanced these processes. Mechanistically, HCK expression enhanced OS tumorigenesis via the mitogen-activated protein kinase (MEK)/extracellular signal-regulated kinase (ERK) pathway; HCK upregulation increased the phosphorylation of MEK and ERK and promoted epithelial-mesenchymal transition, with a reduction in E-cadherin in vitro. Furthermore, HCK downregulation decreased the tumour volume and weight in mice transplanted with OS cells. In conclusion, HCK plays a crucial role in OS tumorigenesis, progression and metastasis via the MEK/ERK pathway, suggesting that HCK is a potential target for developing treatments for OS.     

Identification of pyrrolo[2,3-d]pyrimidines as potent HCK and FLT3-ITD dual inhibitors

A series of novel pyrrolo[2,3-d]pyrimidines were synthesized by introducing 15 different amino acids to 7-cyclohexyl-5-(4-phenoxyphenyl)-7H-pyrrolo[2,3-d]pyrimidine-4-amine. Compounds with potent activities against HCK and FLT3-ITD were evaluated in viability studies with acute myeloid leukemia cell line MV4-11. Our structure activity relationship analyses lead to the identification of compound 31, which exhibited potent HCK and FLT3-ITD inhibition and activity against the MV4-11 cell line.