Figure 1. PERK expression is maintained in cancer cells wherein it regulates tumor expansion in vivo.

(A) PERK protein levels were measured by immunoprecipitation (IP) followed by Western blot analysis in the following cell lines: MCF10A (1), MCF7 (2), T47D (3), MDA-MB231 (4), MDA-MB468 (5), TE3 (6), TE7 (7), KYSE 520 (8). (B) PERK protein levels following shRNA targeting of PERK. (C) Parental MDA-MB468 cell line, shPERK-transduced cells (shPERK), and shPERK-transduced cells reconstituted with mouse Myc-PERK (+mPERK) were treated with 2μg/ml tunicamycin for the indicated intervals. Western analysis for ATF4, CHOP, or β-actin. (D) Volume of orthotopic tumors formed from the mouse mammary tumor-derived cells transduced in vitro with empty vector virus (Neu/PERK^loxP/loxP) or Cre-expressing retrovirus (Neu/PERK^Δ/Δ) 28 days post-transplant (n=4). Representative image of tumors are provided. All p-values determined by Student t-test. (E) Western analysis of transgenic ErbB2 and PERK expression following infection of mouse mammary tumor-derived cells with control (Neu/PERK^loxP/loxP) or Cre-expressing retrovirus (Neu/PERK^Δ/Δ). Thapsigargin treatment (50nM, 1h) was used to demonstrate that PERK is functional.