EFFECT OF CHLOROQUINE ON THE ENDO-LYSOSOMAL SYSTEM OF BREAST TUMOR CELLS

PEREYRA L; PERALTA S; VARGAS-ROIG L; SOSA MA; CARVELLI, L.

Congreso; XXXIX Reunión Anual de la Sociedad de Biología de Cuyo; 2021

Sociedad de Biología de Cuyo

Breast cancer is the second leading cause of cancer death in women. Estrogen Receptor (ER)-positive breast cancer are less aggressivethan triple negative subtype, where patients have a higher likelihood of recurrence and a poorest survival prognosis. Some tumor cells haveshown an increased lysosomal biogenesis, together with an altered lysosomal integrity and/or functionality, and increased levels oflysosomal proteases such as cathepsin-D (CatD). In most cell types, lysosomal proteins are selectively transported from the trans-Golginetwork(TGN) to lysosomes by the mannose-6-phosphate receptors (CD-MPR and CI-MPR). Alterations in the lysosomal membranepermeability induce a release of CatD into the cytoplasm, triggering apoptotic processes. Thus, lysosomes are considered as potentialtherapeutic targets for antitumor drugs. Acidotropic amines could accumulate in lysosomes, increasing the lysosomal membranepermeability, and leading to leakage of enzymes into the cytoplasm. The acidotropic amine chloroquine is known to affect lysosomalacidification and it is used as an adjuvant for chemotherapeutic treatments. The aim of this study was to evaluate the effect of chloroquineon the cellular distribution of CatD and CD-MPR in cells derived from tumors with different grade of malignancy. MCF-7 and MDA-MB-231 cell lines were incubated with chloroquine during 4, 6, 12 and 18 h, and processed for CatD, CD-MPR and Golgin97 (TGN marker)detection by indirect immunofluorescence and confocal microscopy. In MCF-7 cells (ER-positive), the CatD signal was decreased at 6 hof incubation with chloroquine, and a redistribution to a perinuclear area was observed, whereas the CD-MPR was mostly redistributed inthe cytoplasm. This could indicate an impaired recycling of CD-MPR to TGN and an increased secretion of CatD by default. In turn, theTGN appears disorganized and co-localizes with CD-MPR. Surprisingly, after 12 h of incubation, CatD, CD-MPR and Golgin97 returnedto their initial condition denoting a loss of chloroquine effect over time. By contrast, chloroquine did not induce changes on the distributionof the proteins in MDA-MB-231 cells (triple-negative), indicating a differential response of breast tumor cells to chloroquine, which wouldbe related to their distinct malignancy