Figure 4

Induction of eIF2α phosphorylation by salubrinal inhibits ErbB2-induced hyperproliferation. (A) Representative confocal images of equatorial cross-sections through day 10 vector control, wild type and constitutively active ErbB2 acini stained for Ki-67 (red) or the corresponding images stained with DAPI (blue). Untreated acini (panels a, c and e) and salubrinal treated acini (panels b, d and f). Note Ki-67-positive cells in the outer basal layer of cells in untreated vector control acini (outlined in dotted lines in some structures where edges are not obvious) compared to those occupying the central luminal space in untreated ErbB2-over-expressing acini. Scale bars = 40 μm. Inset (panel d) depicts a smaller salubrinal-treated Wt-ErbB2 acinus with many Ki-67 positive cells. (B) Graph showing distribution of the percentage of wt-ErbB2 cells per acinus that stained positively for Ki-67 at days 6, 8 and 10 (left panel) or phospho-H3 at day 6 (right panel); horizontal red line indicates the median. Statistical significance was determined using the unpaired t-test with p < 0.05 defined as statistically significant. N.S - not significant. Salubrinal treatment significantly decreases the percentage of Ki-67 positive cells in WT-ErbB2 acini only early at day 6.(C) Graph showing distribution of the percentage of cells per acinus that stained positively for Ki-67 cells; mean ± SEM. Statistical significance was determined using the unpaired t-test with p < 0.05 defined as statistically significant. N.S - not significant. Note the increase in percentage of Ki-67 positive cells in untreated CA-ErbB2 expressing acini compared to vector controls. Salubrinal treatment significantly decreases the percentage of Ki-67 positive cells in CA-ErbB2 acini.