PTEN loss does not confer resistance to EGFR kinase inhibition. A, cells expressing a scrambled control sh-RNA (sh-Scr) or a PTEN sh-RNA (sh-PTEN) were analyzed by immunoblot for cleaved PARP, phospho AktThr308, AktSer473 and PTEN expression. Total Akt and β-tubulin are used as an internal loading control. B, parental TGFα-EGFRWT;InkΔ2/3−/− cultured tumor cells (T1-T3) and their PTEN knockdown counterpart were treated with gefitinib (10 μM) and assayed for cell viability. The results are presented as values relative to untreated conditions (mean ± SD; n=3 in each group, *p<0.005, two-tailed t-test).