A549 cells cultured in 2D monolayer or 3D aggregates were harvested and lysed in cell signaling lysis buffer (Merck Millipore) containing protease/phosphatase inhibitor cocktail (Cell Signaling Technology, Inc.). Protein quantification was performed using a Bradford assay kit (Bio-Rad Laboratories, Inc.). A total of 20 µg protein per lane was separated by 10% SDS-PAGE, electroblotted onto Immobilon-P Transfer Membranes (Merck Millipore) and blocked for 1 h at room temperature with 3% BSA (Sigma-Aldrich; Merck KGaA) in TBS-T (0.1% Tween-20). The membranes were then probed with the indicated primary antibodies: phosphorylated (p)-STAT3 (Y705; 1:250; rabbit, monoclonal; cat. no. 9145), STAT3 (1:3,000; rabbit, polyclonal; cat. no. 4904), p-Akt (1:250; rabbit, polyclonal; cat. no. 9271), Akt (1:1,000; rabbit, polyclonal; cat. no 9272), p-ERK (1:10,000; rabbit, polyclonal; cat. no. 9101), ERK (1:4,000; rabbit, polyclonal; cat. no. 9102), p-p38 (T180/Y182; 1:250; rabbit, polyclonal; cat. no. 9211), p38 (1:1,000; rabbit, polyclonal; cat. no. 9212), p-FAK (1:200; rabbit, monoclonal; cat. no. 8556), FAK (1:1,000; rabbit, polyclonal; cat. no. 3285), Mcl-1 (1:250; rabbit, polyclonal; cat. no. 4572), survivin (1:200; rabbit, polyclonal; cat. no. 2803), puma (1:500; rabbit, polyclonal; cat. no. 4976), cyclin D1 (1:250; rabbit, polyclonal; cat. no. 2922), cyclin D3 (1:1,000; mouse, monoclonal; cat. no. 2936), CDK2 (1:1,000; rabbit, monoclonal; cat. no. 2546) (all from Cell Signaling Technology, Inc.), MYLK (1:200; mouse, monoclonal; cat. no. sc-365352; Santa Cruz Biotechnology, Inc.) and GAPDH (1:50,000; rabbit, monoclonal; cat. no. ab190480; Abcam) at 4°C overnight. The membranes were washed and incubated for 1 h at room temperature in a 1:5,000 dilution of HRP-conjugated goat anti-rabbit (monoclonal; cat. no. 7074; Cell Signaling Technology, Inc.) or rabbit anti-mouse (polyclonal; cat. no. P0260; Dako; Agilent Technologies, Inc.) secondary antibodies. Visualization of the protein bands was performed with the SuperSignal™ West Pico PLUS Chemiluminescent Substrate (cat. no. 34580; Thermo Fisher Scientific) or SuperSignal™ West Femto Maximum Sensitivity Substrate (cat. no. 34096; Thermo Fisher Scientific, Inc.). Quantification of the bands was carried out by densitometry using ImageJ version 1.53k software (National Institutes of Health).
Keeratichamroen S., Sornprachum T., Ngiwsara L., Ornnork N, & Svasti J. (2023). p‑STAT3 influences doxorubicin and etoposide resistance of A549 cells grown in an in vitro 3D culture model. Oncology Reports, 49(4), 71.