Figure 2. Inhibition of eIF4E activity does not affect wild-type prostate epithelial cell maintenance but suppresses prostate tumor initiation and progression in the setting of PTEN loss in vivo.

(A) Schematic representation of the prostate-specific and doxycycline-inducible PTEN^L/L;4EBP1^M mouse model, in which the addition of doxycycline to the drinking water (at 2 g/L) induced the expression of the 4EBP1^M transgene. (B) Representative H+E staining of ventral prostate glands from 4EBP1^M mice after 4 weeks with or without doxycycline in their drinking water. Scale bar, 100 μm. (C) Representative H+E staining of wild-type (WT), PTEN^L/L, and PTEN^L/L;4EBP1^M prostates after 4–5 weeks of exposure to doxycycline after weaning. Percent high grade prostatic intraepithelial neoplasia (PIN) positive glands in PTEN^L/L and PTEN^L/L;4EBP1^M mice (n = 3 mice/genotype, *P = 0.03, t-test). Scale bar, 500 μm. (D) Fold change in TUNEL positive cells in WT, PTEN^L/L, and PTEN^L/L;4EBP1^M prostates after 4–5 weeks of exposure to doxycycline after weaning (n = 3 mice/genotype, *P = 0.004, **P <0.0001, t-test). (E) Representative PTEN^L/L;4EBP1^M prostate with or without exposure to doxycycline for 8 weeks starting at age 6–8 months. Mice were at 8–10 months of age at necropsy. (F) Quantification of mouse prostate weights between PTEN^L/L and PTEN^L/L;4EBP1^M exposed to doxycycline for 8 weeks (n = 4–5 mice/genotype, *P = 0.02, t-test). (G) Representative ultrasounds of PTEN^L/L and PTEN^L/L;4EBP1^M anterior prostates before and after 8 weeks exposure to doxycycline. (H) Quantification of tumor area in PTEN^L/L and PTEN^L/L;4EBP1^M anterior prostates before and after 8 weeks exposure to doxycycline (n = 4–5 mice / genotype, *P= 0.003, t-test). (I) Fold change in TUNEL-positive (apoptotic) cells in PTEN^L/L and PTEN^L/L;4EBP1^M (n = 3 mice/genotype, *P = 0.0006, t-test). Data are mean +/− S.E.M.