Figure 1.

Selection of a CD19⁺ cancer cell line that expresses no folate nor TLR7 receptor and will grow in immune competent mice. Cancer cells lines (4T1, CT26, EMT6) that were known to grow in immune competent mice were cultured for 1 week in folate deficient medium to upregulate inducible folate receptors (if any) and then screened by flow cytometry to assure that the cells still expressed neither a folate receptor (A) nor a Toll-like receptor 7 (B). Known folate receptor positive (L1210A cells) and TLR7 positive (24JK cells) were used as positive controls. FR and TLR7 negative cell lines were then stably transduced with murine CD19 (mCD19) to create a cancer cell line that would respond to an anti-CD19 CAR T cell therapy. Successful expression of CD19 was confirmed after one-month of culturing by flow cytometry (C). Each flow cytometry analysis was performed at least three times, with representative histograms shown above.