?P-glycoprotein 1 mediates Galectin-1-induced resistance to doxorubicin in hepatocellular carcinoma(HCC) cells.

CARABIAS, P; BACIGALUPO, ML; OTERO, S; SAFFIOTI, N; ELOLA, MT; CARLOTA WOLFENSTEIN-TODEL; ROSSI, JP; RABINOVICH GA; ESPELT M.V; TRONCOSO, MF

Congreso; SAFIS-SAIC; 2016

Galectin-1 (Gal1), a β-galactoside-binding protein, is overexpressedin HCC and it is related to tumor aggressiveness. P-glycoprotein 1 (Pgp), also known asmultidrug resistance protein 1 (MDR1), is an ATP-dependent drug efflux pump. Its overexpression in tumor cells decreases intracellular chemotherapeutic drug concentration, showinga multidrug resistant phenotype. Previously, we reported that Gal1 overexpression in human HCC HepG2 cells (HepG2Gal1) reduces apoptosis induced by the chemotherapeutic drugs camptothecin and doxorubicin (DOX). Also, we described that HepG2Gal1 cells show increased levels of Pgp protein expression.Our aim was to evaluateif Gal1 overexpression reduces intracellular DOX levels in HepG2 cells, andto confirmPgp involvement onGal1-mediated resistanceto DOX-induced cell death.Byfluorescence techniques we found a significant decrease in intracellular DOX concentration (pmol/µM total protein, min after treatment) in HepG2Gal1 cells compared with HepG2 cells (1.2±0.1 vs 1.8±0.1, 30; 1.7±0.4 vs 2.9±0.5, 60; 2.3±0.5 vs 4.5±1, 90; 3.1±0.7 vs 5.6±1.2, 120).Co-incubation of HepG2 orHepG2Gal1 cells for 24h with DOX (2µM) and verapamil (20µM), a Pgpinhibitor, diminished cell viability (MTT) compared with cells incubated only with DOX, respectively (HepG2, 37.4±5.1% vs 54±5.3%; HepG2Gal1, 60.1±3.4% vs 77.8±2.5%).Similar results were obtained silencing Pgp expressionin HepG2Gal1 cells with siRNA (Scr+DOX 61.1±2.7% vssiRNA+DOX 40.8±7.2%). However, probenecidtreatment (250µM), a multidrug resistance-associated protein 2 (MRP2) inhibitor, did not change DOX-treated cell viability (HepG2, 51.5±9.3% vs 53.1±6.7%; HepG2Gal1, 69.0±9.8% vs 78.1±12.3%).Thus, Gal1-overexpressing HepG2 cells accumulate less intracellular DOX, showing a resistant phenotype. Moreover,Pgpinhibition, but not MRP2, orPgpspecific expression silencingsensitizes HepG2 cells to DOX, suggesting the involvement of Pgp in Gal1-mediated resistance to DOX-induced cell death.