Differential response of the endo-lysosomal system to chloroquine in breast tumor cells

PEREYRA L; PERALTA S; VARGAS ROIG LM; SOSA MA; CARVELLI L

Palma de Mallorca

Workshop; 2nd International Workshop on Translational Cancer Research; 2021

Estrogen Receptor (ER)-positive breast cancer are less aggressive than triple negative subtype. Some tumor cells have shown an increased lysosomal biogenesis, together with an altered lysosomal integrity and/or functionality, and increased levels of lysosomal proteases such as cathepsin-D (catD). In most cell types, lysosomal proteins are selectively transported from the trans-Golgi-network (TGN) to lysosomes by the mannose-6-phosphate receptors (CD-MPR and CI-MPR). Alterations in the lysosomal membrane permeability induce a release of catD into the cytoplasm, triggering apoptotic processes. Thus, lysosomes are considered as potential therapeutic targets for antitumor drugs. Acidotropic amines could accumulate in lysosomes, increasing the lysosomal membrane permeability, and leading to leakage of enzymes into the cytoplasm. The acidotropic amine chloroquine is known to affect lysosomal acidification and it is used as an adjuvant for chemotherapeutic treatments. The aim of this study was to evaluate the effect of chloroquine on 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 6-24 h, and processed for catD, CD-MPR and Golgin97 (TGN marker) detection by indirect immunofluorescence. In MCF-7 cells (ER-positive), the catD signal was decreased at 6 h of incubation with chloroquine, and a redistribution to a perinuclear area was observed, whereas the CD-MPR was mostly redistributed in the cytoplasm. This could indicate an impaired recycling of CD-MPR to TGN and an increased secretion of catD by default. In turn, the TGN appears disorganized and co-localizes with CD-MPR. Surprisingly, after 12 h of incubation, catD, CD-MPR and Golgin97 returned to their initial condition denoting a loss of chloroquine effect over time. By contrast, chloroquine did not induce changes on the distribution of the proteins in MDA-MB-231 cells (triple-negative), indicating a differential response of these breast tumor cells to chloroquine.