RSPO1 and sarcoma: GM: advance DMEM supplemented with—10% heat-inactivated horse serum, primocin, and 1 glutamax for MFS2.1 glutamax, B27 supplement, primocin, 1.25 mM N-acetylcystein, 50 ng/mL rhEFG, 20 ng/mL rhFGF 10, 1 ng/mL rhbFGF, 500 nM A-83-01, 10 mM SB202190, 10 mM nicotinamide, 1 mM prosta-glandin E2, 25 nM hydrocortisone, 0.5 mg/mL epinephrine, and 50 mL R-spondin for the remaining sarcoma type. 1:1 mixture of HS:CHK at P5.SM: advance DMEM without additional growth factors