All transduced EFPrx1MSCL cell lines with BCL2 family members gave rise to prominent sarcoma formation within 3–4 weeks and with 100% penetrance when 4 × 106 Bcl2-, Bcl-xL- or Mcl1-transduced EFPrx1MSCL cells were injected. This evidence concerns the gene MCL1 and sarcoma.