Figure 8. PERK loss attenuates MMTV-Neu-driven mammary tumorigenesis in mice, but promotes spontaneous mammary tumor formation in aged mammary gland-specific PERK knockout mice.

(A) Kaplan-Meier analysis of tumor-free survival for cohorts of MMTV-Neu/PERK^loxP/loxP (n=21) and MMTV-Neu/PERK^{Δ/Δ Δ/Δ} (n=27) mice. (B) Hematoxylin and eosin staining demonstrating histology of control (Neu/PERK^loxP/loxP) and PERK knockout (Neu PERK^Δ/Δ) mammary gland tumors. (C) Western analysis for PERK, ErbB2, and eIF4E levels on whole protein extracts from control (Neu/PERK^loxP/loxP) and PERK knockout (Neu/PERK^Δ/Δ) mammary gland tumors or mammary gland from lactating PERK^loxP/loxP dam (L10). (D) Nrf2 was precipitated from tumor lysates prepared from MMTV-Neu/PERK^Δ/Δ or control mice and blotted for phospho-Thr and Nrf2. PERK expression was determined by immunoblot. (E) PERK excision delays development of Neu-driven hyperplastic lesions. Representative mammary glands from 9- to 14-months old control (Neu/PERK^loxP/loxP) and PERK knockout (Neu/PERK^Δ/Δ) mice revealing pre-malignant lesions are shown. (F) Hematoxylin and eosin staining on lungs from control (Neu/PERK^loxP/loxP, n=24) and PERK knockout (Neu/PERK^Δ/Δ, n=27) mice revealing metastatic lesions. (G) Troma-1 (cytokeratin-8) staining on lung specimens containing metastatic foci. LT=lung tissue; Met=metastasis; OL=overlay. (H) Hematoxylin and eosin staining for tumor histology and whole mount of hyperplastic lesions in mammary glands of PERK^Δ/Δ aged females. (I) qRT-PCR for ErbB2 on genomic DNA from PERK^Δ/Δ tumors and FISH analysis on paraffin sections from the same animals. Levels of ErbB2 in tumors were compared to matched spleen tissues.