Fig. 4. VitD acts via VDR in the gut epithelium to alter gut microbiome and permit tumor control.

(A, C-D) Growth profile of 0.2 x 10⁶ 5555 Braf^V600E cancer cells implanted into: (A) WT C57BL/6J mice that received (on days -14 and -12 prior to tumor inoculation) FT from WT C57BL/6J, Rag1^-/-, Batf3^-/- or Myd88^-/- donors that had been fed for 3.5 weeks on a VitD₃ standard or VitD₃ high diet. WT + WT-VitD₃^Standard FT (n=10), WT + WT-VitD₃^High FT (n=10), WT + Rag1^-/-- VitD₃^Standard FT (n=10), WT + Rag1^-/--VitD₃^High FT (n=9), WT + Batf3^-/--VitD₃^Standard FT (n=11), WT + Batf3^-/--VitD₃^High FT (n=11), WT + Myd88^-/--VitD₃^Standard FT (n=9), WT + Myd88^-/--VitD₃^High FT (n=9). (B) Lysates from the indicated mouse tissues of Vdr^+/+ and Vdr^{Δ IEC} mice immunoblotted for VDR and GAPDH. (C) Vdr^+/+ or Vdr^ΔIEC mice kept on a VitD₃ standard⁺ (2 IU/g) diet complemented with 2% calcium, 1.25% phosphorus and 20% lactose were then maintained on the same diet or switched to a VitD₃ high⁺ (10 IU/g) diet (similarly complemented with 2% calcium, 1.25% phosphorus and 20% lactose) from 3.5 weeks before tumor inoculation. Vdr^+/+-VitD₃^Standard+ (n=12), Vdr^+/+-VitD₃^High+ (n=11), VdrΔIEC -VitD₃^Standard+ (n=15), VdrΔIEC - VitD₃^High+ (n=15) (D) WT C57BL/6J mice (n=10 per group) received (on days -14 and -12 prior to tumor inoculation) FT from the groups in (C), i.e., Vdr^+/+ or Vdr^ΔIEC donors that were fed with VitD₃ standard⁺ or VitD₃ high⁺ diet. Data in (A, C and D) are presented as tumor volume (mm³) ± SEM and are representative of two independent experiments. Tumor growth profiles (A, C and D) were compared using Bonferroni-corrected two-way ANOVA. *p<0.05, ****p< 0.0001; ns, not significant.