Figure 4. PIK3R2 depletion induces SQCC xenograft regression.

A, B. Lung SQCC cell lines expressing inducible PIK3R2 shRNA were cultured (72 h) at indicated doxycycline concentrations. Sample extracts were examined in WB to confirm PIK3R2 shRNA efficiency in reducing p85β levels (top). Cell lines were expanded in culture and injected subcutaneously into scid/beige mice (~10⁷ cells in 100 μl PBS plus 100 μl matrigel). Tumors developed for several days until they reached ~50 mm³; we then included doxycycline (2 mg/ml) in drinking water and measured tumor size three times/week. We compared tumor growth after doxycycline addition to drinking water. As a control, we used tumors generated with cell lines expressing empty vector and treated with doxycycline (control 1) or generated with cell lines expressing inducible PIK3R2 shRNA with no doxycycline (control 2); both controls gave comparable results. Graphs in A, (left) and B) indicate the size of each tumor at different times after treatment. Differences between control and treated mouse tumors were analyzed with a 2-way ANOVA test. Graphs in A, (right) show percent change in tumor size, comparing the final with initial tumor size (pre-treatment). We compared groups using the Chi square test.