*2.5. Matrigel Induced 3D Spheroid Cultures*

Matrigel (Corning Life Sciences, Tewksbury, MA, USA) diluted in 1.2 mM Ca2<sup>+</sup> SGEC sub-culturing medium (2 mg/mL final concentration) was solidified in 8-well Nunc™ Lab-Tek™ II Chamber Slides™ (Thermo Fisher Scientific, Waltham, MA, USA) or 12-well tissue culture-treated plates (VWR, Radnor, PA, USA) and incubated for 1 h at 37 ◦C. Cells were seeded at 3 <sup>×</sup> <sup>10</sup><sup>5</sup> or 1 <sup>×</sup> 106 per well, respectively. Cell cultures on matrigel-coated plates were grown at 37 ◦C and 5% CO2 for up to 7 days.
