The Function Of Annexin A1 In Acute Mveloid Leukemia Cells

Leukemia is a kind of hematological malignancies with abnormal proliferation of hematopoietic stem cells, which can be divided into acute myeloid leukemia, acute lymphoblastic leukemia, chronic myeloid leukemia, chronic lymphocytic leukemia. Leukemia is the most commonly diagnosed type of cancer in children aged 0-14 years which accounts for about 35% of the total number of cancers, and the incidence of leukemia is rising year by year.At present, the majority of acute myeloid leukemia can not be well controlled with the problems of a few kinds of drugs, poor targeting and without an expectant therapeutic effect. Therefore, it is urgent to find and develop more effective drugs to treat leukemia with the characteristics of reduced side effects and improved treatment rate.Annexin A1, a membrane protein, is involved in a variety of pathophysiological processes in vivo. Previous studies have reported that Annexin A1 may be involved in the occurrence and development of tumors. However, there is no report about Annexin A1 in myeloid leukemia. In our present study, peripheral blood samples from patients with acute myeloid leukemia and normal volunteers have been collected, and the expression level Annexin A1has been detected by Western blot technology. We have investigated the function of Annexin A1 in modulation the proliferation of acute myeloid leukemia cells through the construction of the knock-down expression of Annexin A1 in leukemia cell lines (KG-la and HL60 cell lines), as well as we have elucidated the molecular mechanism involved in the role of Annexin A1 at the cellular and molecular level. We further evaluated the effect of Annexin A1 in node mice bearing the leukemia cells in vivo.We have collected peripheral blood samples from 37 patients with acute myeloid leukemia without treatment during the period from 2014 to 2017 in the Zhejiang Province People's Hospital, and extracted the white blood cells by lysis the red blood cells. The proteins in the white blood cells were obtained to detect the expression level of Annexin A1 using Western blot method. Our results showed that the expression level of Annexin A1 in patients was significant higher than the expression level of Annexin A1 in volunteers. In the cell lines with the property of knock-down the expression level of Annexin A1 using RNA interference technology, the proliferation rate and double proliration time of KG-1a and HL60 cells were inhibitied significantly with the knock-down expression of Annexin A1,indicating that Annexin A1 has the property to promote the proliferation of acute myeloid leukemia cells. The results of flow cytometry showed that the expression of Annexin A1 could block cell in the G0/G1 phase, but not promote cell apoptosis. The results obtained from Western blot showed that the expression levels of Notch1 and p15 were enhanced in the cells with the knock-down expression level of Annexin A1. The proteins of Annexin A1 and Notchl were co-localization on the cells membrane in KG-1a and HL60 cells using the method of immunocytochemistry. Furthermore, our results from Co-IP showed that the proteins of Annexin A1 and Notch1 have interaction. We speculate that Annexin A1 have the ability to promote the degradation of Notch1 though the ubiquitin degradation pathway, which be validated by chloroquine treatment, an inhibitor of ubiquitin degradation pathway, with the results of enhanced the expression level of Notch1 and the proliferation inhibition of KG-1a cells after the treatment of chloroquine. In addition, KG-1a cells with the knock-down expression of Annexin A1 have the lower growth and proliferation property conmpared with KG-1a itself after injection in BALB/c nude mice via subcutaneous injection.In short, all of our present results showed that Annexin A1 has the ability to promote the proliferation of acute myeloid leukemia cells in vitro and in vivo, and the mechnisms involved in the effect of Annexin A1 could be related to the interation of Annexin A1 and Notch1, as well as the modulation the expression levels of Notch signal pathway, such as p15. Our present results will provide the basic theoretical data for the subsequent development of Annexin A1 as a new target for the treatment of leukemia.