A2780cis

A2780 (platinum-sensitive) and A2780cis (platinum resistance) human ovarian cancer cell lines were purchased from Sigma Aldrich (Gillingham, UK). PEO1 (BRCA2 deficient) and PEO4 (BRCA2 proficient) were purchased from American Type Culture Collection (ATCC, Manassas, VA, USA). A2780, A2780cis, PEO1, and PEO4 were cultured in RPMI (R8758, Merck, Dorset, UK) with 10% FBS (F4135, Merck, Dorset, UK), 1% Penicillin-Streptomycin (P4333, Merck, Dorset, UK). FEN1-deficient HeLa SilenciX cells and control HeLa cells were purchased from Tebu-Bio and were grown in Dulbecco’s Modified Eagle’s Medium (11965092, Thermo Fisher Scientific) supplemented with 10% FBS, 1% penicillin/streptomycin, and 125 μg/mL hygromycin B. All cell lines were maintained in a humidified incubator at 37 °C in a 5% CO₂ atmosphere.

The human OC cell lines, A2780 and A2780cis were obtained from Sigma Aldrich. The latter made resistant to cisplatin as previously described [48 (link)]. The ES-2 (CRL-1978) and SK-OV-3 (HTB-77) cells were both purchased from American Type Culture Collection (ATCC, Wesel, Germany). The cells were cultured in RPMI 1640 (A2780 and A2780cis) or McCoys 5A medium (ES-2 and SK-OV-3) and complemented with 10% FCS and 2% pest/glut (all Sigma Aldrich). The human OC cell line SK-OV-3-Luc IP1 is a more potent, luciferase positive OC cell line, created through in vivo selection [49 (link)]. Sort Tandem Repeat (SRT) profiling was conducted as described by De Vlieghere et al. [49 (link)]. This cell line was cultured in Dulbecco's Modified Eagle's Medium (DMEM, Life technologies, ThermoFisher, Ghent, Belgium), supplemented with 2% penicillin/streptomycin (Life technologies) + 0.005% fungizone (Bristol-Myers-Squib B.V., Utrecht, The Netherlands) and 10% FCS (Sigma-Aldrich) [50 (link)]. Saline and BD matrigel (Life Sciences, Antwerp, Belgium) were used to dilute SK-OV-3-Luc IP1 cells before IP and SP injection, respectively. The cell banks performed authentications by short tandem repeat analysis. All cell line experiments in Sweden were performed within 6 month after resuscitation, in Belgium STR was done to verify identity.

Cell viability was determined in a human ovarian carcinoma cell line (A2780) and its cisplatin resistant variant (A2780cis) obtained from Sigma. Cells were grown in (RPMI)-1640 medium supplemented with 10% fetal bovine serum (FBS). For the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay (Sigma-Aldrich, St. Louis, MO, USA), cultured A2780 and A2780cis cells were seeded into 96-well flat-bottomed plates at a density of 5 × 10³ cells in 100 μL of medium and incubated for 24 h in a 5% CO₂ atmosphere at 37 °C. They were then incubated in growth medium containing different concentrations of decitabine, cisplatin or equivalent cisplatin/decitabine-loaded CS2-cis-PLGA-dac NPs for 72 h. Media containing different cisplatin dosages were made up from successive dilutions in warmed media, from a stock solution of cisplatin in sterile PBS (1 mM). After treatment, MTT (5 mg mL⁻¹ in PBS) was diluted 1 : 100 with medium into each well. After 2 h of incubation, culture supernatants were aspirated, and purple insoluble MTT product was dissolved in 100 μL of dimethyl sulfoxide (DMSO)/ethanol (EtOH) (50 : 50) for 10 min. The absorbance in each well was recorded at 570 nm using a microplate reader; blanks were subtracted from all data, and the results were analysed using Origin software (OriginLab, Northampton, MA, USA).