Figure 4. Abcg1^−/− macrophages in the tumor display enhanced apoptosis under Western-like diet conditions.

(a) Blood and tumor cells from Western-like diet-fed Abcg1^fl/fl-LysM-Cre⁺ (n=6) and Abcg1^fl/fl-LysM-Cre⁻ (n=6) mice were analyzed by flow cytometry 18 days after MB49 tumor injection. Dot plots show frequencies of monocytes (CD45⁺, NK1.1⁻, Ly6G⁻, CD11b⁺, CD115⁺) (% of live cells) in blood (top) and tumor (bottom). (b–e) Tumor cells from Abcg1^−/− (n=5) and WT (n=5) mice were analyzed for apoptosis by Annexin V staining and flow cytometry 12 days after injection of MB49 cells. (b,d) Representative pseudo-color plots show percentages of all tumor cells gated on live cells (left) and CD45⁺, NK1.1⁻, Ly6G⁻, CD11b⁺, F4/80^high macrophages, which are Annexin V⁺ (right). Dot plots show percentages of apoptotic (Annexin V⁺ live) macrophages in tumor from (c) Western-like-diet-fed and (e) chow diet-fed mice. Data are representative of 2 independent experiments with similar results (mean ± s.e.m., **P < 0.01, two-tailed Student’s t test).