PTEN-KD confers endocrine resistance in the xenograft mouse model. (A) Fluorescent live images showed MCF7L-shPTEN xenograft tumors at week 6 after randomization. Fluorescent red suggests the expression of tRFP with the color bar indicated at bottom. The tumors without a red signal (arrow indicated) show the fluorescent green (eGFP expression) in the insets. (B-E) Growth curves of xenograft tumors under E2, ED, Tam, or Ful, all -/+Dox (n ≥10 in each arm). The IHC staining of PTEN (F), pAKT-S473 (H), and Ki67 (J) in tissue microarrays of xenograft tumors after two weeks of treatment was quantified as the Allred scores of cytoplasmic PTEN (G) and cytoplasmic pAKT-S473 (I), or as the proportion of Ki67 positive cells (K). n = 6 for each arm; scale bar, 50 μm (F and H), 100 μm (J). The Bonferroni post hoc test was applied for paired comparisons between -/+Dox in each endocrine group, or between the anti-estrogen and E2 groups (*P <0.05, **P <0.01, ***P <0.001). Dox, doxycycline; E2, β-estradiol; ED, estrogen deprivation; eGFP, enhanced GFP; Ful, fulvestrant; IHC, immunohistochemical; KD, knockdown; PTEN, phosphatase and tensin homolog; Tam, tamoxifen; tRFP, turbo-RFP.