Banca de DEFESA: RAFAELA GOMES ALVES COSTA

PHARMACOLOGICAL STUDY OF BORTEZOMIB IN THE TREATMENT OF ACUTE MYELOID LEUKEMIA WITH ACTION ON STEM CELLS LEUKEMIC

Bortezomib; Leukemic stem cells; Acute myeloid leukemia; NF-κB.

INTRODUCTION: Acute myeloid leukemia (AML) is characterized by the uncontrolled growth of immature blasts in the bone marrow and corresponds to one of the most common types of cancer in the world. The 5-year relative survival rate is relatively low, and most patients eventually relapse. It is believed that one of the main factors responsible for the low rate of complete remission of the disease is associated with leukemic stem cells (CTL). Studies suggest that AML is originated and maintained by this population of CTLs. The NF-κB signaling pathway acts in the progression of cancer after tumor formation, being constitutively active in CTLs and, for this reason, it becomes an important therapeutic target. In this context, bortezomib (BTZ) is already described as a potent inhibitor of the NF-κB pathway and has been studied for the treatment of some hematological diseases. OBJECTIVE: Evaluate the antileukemic potential of BTZ as a therapeutic strategy to eliminate human AML CTLs in an in vitro and in vivo model. METHODOLOGY: BTZ cytotoxicity was tested on a panel of cancerous and non-cancerous cell lines. CTLs were identified using antibodies CD34, CD38, CD133, CD13 and CD123. The KG-1a strain was used to carry out BTZ mechanism of action assays in order to assess viability through cell cycle analysis, detection of cell death by apoptosis, evaluation of mitochondrial transmembrane potential and production of reactive oxygen species (ROS) by the flow cytometry technique. Analyzes of gene expression and signaling pathways associated with cancer through qPCR in cells treated with BTZ were also performed, in addition to assays for antitumor evaluation in an in vivo model. RESULTS: BTZ was cytotoxic to different strains tested with IC50 values ranging from 0.13 to 9.17 µM for cancer cell lines NB4 and U87 respectively. In addition, BTZ reduced the population of viable CTLs, induced apoptotic cell death, increased expression of active caspase-3 and cleaved PARP-1, induced alterations in mitochondrial transmembrane potential, increased ROS levels, induced DNA fragmentation in cells KG-1a and altered the gene expression of KG-1a cells, in addition to inhibiting the growth of these cells in an in vivo model. CONCLUSION: The antileukemic activity performed by BITZ emerges as a promising new path for the treatment of AML, with CTLs as the main target.