FOLR1 and cancer: Notably, after 24 hours of coincubation with FRα-expressing cancer cells (SKOV3), C4-27z and C4opt-27z, but not CD19-27z, CAR expression declined rapidly in CD3+, CD4+ or CD8+ T cells, consistent with T cell activation and metabolism resulting in a greater loss of RNA-transcribed CAR expression (Figures 1G, Supplemental Figures 2A–2B).