Engraftment of human cancer cells into rag2^Δ/Δ, il2rga ^−/− zebrafish. (A) Representative merged fluorescence and brightfield images of EGFP⁺ human cancers grown in rag2^Δ/Δ, il2rga^−/− zebrafish. Images shown just after engraftment (0 dpt; left) and at 28 dpt (right). Tumor type is noted in upper right and cell line name in lower left in leftmost panels. TNBC, triple negative breast cancer; CML, chronic myeloid leukemia; SCLC, small cell lung cancer. Tumor growth was assessed by relative GFP intensity multiplied by 2D pixel volume, with exception of PDX tumors that were stained with CFSE. In these PDX engrafted tumors, retention of blue CFSE denotes successful long-term engraftment. (B) H&E-stained sections of engrafted tumors. (C) Ki67 IHC to assess tumor cell proliferation. (D) TUNEL staining to assess apoptotic cells. Average percentage cells ±SD noted (n ≥ 3 fish/tumor type; B–D). (E) Quantification of relative (Rel.) growth of EGFP⁺ human cancer cells following successful engraftment into individual rag2^Δ/Δ, il2rga^−/− zebrafish. Scale bars equal 0.25 cm (A) and 50 µm (B–D). * denotes cell lines that did not efficiently engraft in previous immune-deficient zebrafish models.