Figure 1.

Retinoid X receptors (RXR) natural ligands are present in MLL-AF9 myeloid leukemia in vivo. (A) Schema for bone marrow (BM) transplant procedure. Kit+ cells isolated from the BM of UAS-GFP mice using magnetic-activated cell sorting (MACS) were transduced with MSCV-MLL-AF9, MSCV-Notch1 or MSCV-TLS-ERG retroviruses and then injected into sublethally irradiated recipient mice. When leukemia emerged, recipient mice were sacrificed and their leukemic cells harvested. Leukemia cells were transduced with MCSV-Flag-Gal4-RXRA-IRES-mCherry (Gal4-RXRA), MSCV-Flag-Gal4-RXRA-ΔAF2-IRES-mCherry (Gal4-RXRA-DAF2), or MSCVFlag- Gal4-RARA-IRES-mCherry (Gal4-RARA) and then injected into sublethally irradiated recipient mice. After leukemia engraftment, leukemia cells were harvested and the ratio of mCherry+GFP+ versus total mCherry+ cells was evaluated by flow cytometry. (B and C) Representative data showing GFP and mCherry intensity in MLL-AF9 leukemia cells. (D) Representative GFP and mCherry expression in mice transplanted with MLL-AF9-derived leukemic cells transduced with Gal4-RXRA and treated with Targretin (bexarotene, 50 mg/kg) by oral gavage administration for 2 days. (E) Combined results from mice transplanted with MLL-AF9-derived leukemia transduced with Gal4-RXRA (circles; n=5 recipient mice) or RXRA-DAF2 (squares; n=3 recipient mice). (F) Combined results from mice transplanted with MLL-AF9- derived leukemia cells transduced with Gal4-RXRA and gavaged with bexarotene (Targretin) (squares; n=4 recipient mice) or water (vehicle) (circles; n=4 recipient mice). (G) Representative GFP and mCherry intensity in MLL-AF9-derived leukemia cells transduced with Gal4-RARA and transplanted into recipient mice (n=3 recipient mice). (H and I) Representative GFP and mCherry intensity in leukemia cells derived with MSCV-Notch1 (n=5 recipient mice) or MSCV-TLS-ERG (n=4 recipient mice) retroviruses, transduced with Gal4-RXRA, and transplanted into recipient mice. t-test with Welch’s correction.