Sensitizing KSHV-positive PEL Cells

KSHV-positive PEL cell lines, BC3 (ATCC, CRL-2277) and BCBL1 (kindly supplied by Prof. P. Monini, National AIDS center, Istituto Superiore di Sanità, Rome, Italy), were grown in RPMI 1640 medium (Sigma-Aldrich, Burlington, MA, USA), supplemented with 10% fetal bovine serum (FBS) (Sigma-Aldrich, Burlington, MA, USA), L-glutamine (2 mM) (Aurogene, Rome, Italy), and streptomycin/penicillin (100 μg/mL) (Aurogene, Rome, Italy) (complete medium) at 37 °C, in a 5% CO₂ humified setting. Cells were seeded into 6-well plates, at a density of 4 × 10⁵ per well, in a final volume of 2 mL in complete RPMI medium, and they were treated for 24 h with J2 (10–20 µM) (MedChemExpress, Monmouth Junction, NJ, USA; cat n. HY-124653), PES-Cl (10–20 µM) (Calbiochem, San Diego, CA, USA; cat n. 5.31067), 17-AAG (0.1–1 µM) (Selleckem, Planegg, Germany; cat. n. S1141) or AG490 (100 µM) (Calbiochem, San Diego, CA, USA; cat n. 658411), inhibitors of HSP27, HSP70, HSP90 and STAT3, respectively. All the drugs were dissolved in DMSO, and the control cells were supplemented with DMSO in the same amount used for the other samples. To evaluate if HSPs or STAT3 inhibitors could sensitize PEL cells to the cytotoxic effect of PARP inhibitor, the cell lines were pre-treated for 1 h with HSP27, 70, 90 inhibitor (inHSP) or AG490 and then supplemented with AZD2461 (AZD, 40 μM) (Sigma-Aldrich, Burlington, MA, USA, cat n. SML1858) for 24 h. Untreated cells were used as a control group (CT).