Banca de DEFESA: RAYSSA DE MELLO LOPES

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : RAYSSA DE MELLO LOPES
DATE: 16/12/2022
TIME: 13:00
LOCAL: Online via Google Meet (https://meet.google.com/oav-mgsz-jer)
TITLE:

The role of autophagy on phenothiazine-induced cell death in leukemia cells

PAGES: 77
BIG AREA: Ciências Biológicas
AREA: Bioquímica
SUBÁREA: Metabolismo e Bioenergética
SUMMARY:

Leukemias comprises a set of heterogeneous hematological neoplastic diseases that occupy the 10th position among the cancer types with the highest mortality rates in the world. Although the therapeutic arsenal has improved significantly in recent years, the development of resistance to available drugs has been often described. Recent studies have reported increasing rates of relapse, drug resistance, drug toxicity against normal tissues and cells, and other side effects. Therefore, novel therapeutic approaches need to be explored to overcome these challenges and the drug repositioning has emerged as a promising alternative. In this regard, several studies have shown that, in addition to antipsychotic and neuroleptic activity, phenothiazines have other biological effects, including antitumor activity in vitro and in vivo against various types of cancer. Recent data from our research group suggest that one of the mechanisms of phenothiazine-induced cell death in leukemia cells involves the modulation of autophagy. It was shown that the phenothiazine derivative promethazine induced apotosis-associated autophagy in a chronic myeloid leukemia (CML) model, but on the contrary thioridazine-induced autophagy protected acute lymphoblastic leukemia (ALL) cells from death. The mechanisms responsible for these effects remain unclear. Thus, the aim of this work was to investigate the role of autophagy induced by phenothiazine derivatives used in Medicine on the viability of different types of leukemia cells, in order to understand the alterations leading to cell death or survival. Furthermore, we intend to evaluate the modulation of autophagy as a potential therapeutic target for chemotherapy in leukemia. In cell viability assays, the four clinically used phenothiazine derivatives thioridazine (TR), promethazine (PMTZ), trifluoperazine (TFP) and chlorpromazine (CPZ) exhibited concentration-dependent cytotoxicity. Among them, TR was the most cytotoxic derivative, being selected for subsequent studies. In K562 cells (LMC), TR increased the autophagic flux, assessed by an increase in LC3-II and SQSTM1 (p62) levels. Furthermore, the inhibition of autophagy by bafilomycin A1 decreased the cytotoxicity of TR, whereas the autophagy inducer rapamycin potentiated its cytotoxic effect. Thus, differently from what was observed in the ALL model, TR induced autophagy associated with cell death in the CML model, highlighting the double role of autophagy already described, either pro-death or pro-survival. This result is an indication that the role of autophagy may be due to the subtype and specific characteristic of leukemia on the stimulus of phenothiazines, regardless of whether it is TR or PMTZ. Although more studies are needed to clarify such differences in response to TR in ALL and CML. Investigation of molecular mechanisms revealed that the well-documented action of TR as an antagonist at dopaminergic receptors (DR), a type of protein-coupled receptor (GPCR), is related to the induction of autophagy associated with cell death in CML. It was observed that the LC3-II increase and TR cytotoxicity were potentiated by the DR antagonist haloperidol and reduced by the DR agonist dopamine.TR probably inhibits D2R (GPCR αi/o), since the adenylyl cyclase inhibitor (SQ 25.536 ) protected from its cytotoxic effect, showing that downstream signaling pathways to cAMP production may be associated with cell death. Additionally, we showed that although the decrease in the PI3K/AKT/mTOR pathway is important for TR cytotoxicity, we were unable to correlate its effect with dopaminergic receptor modulation, as additional experiments are needed to clarify the effects observed so far. Together, these results show that the therapeutic potential of TR is associated with the induction of apoptosis-associated autophagy in a CML model and its pharmacological action on DR participates in this cell death mechanism.

COMMITTEE MEMBERS:
Presidente - Interno ao Programa - 1674592 - TIAGO RODRIGUES
Membro Titular - Examinador(a) Interno ao Programa - 1948411 - LUIZ ROBERTO NUNES
Membro Titular - Examinador(a) Externo à Instituição - JOÃO AGOSTINHO MACHADO NETO - USP
Membro Suplente - Examinador(a) Externo à Instituição - DENISE COSTA ARRUDA - UMC