Although AKT ⁄ protein kinase B is constitutively active in nonsmall cell lung cancer (NSCLC) cells and is an attractive target for enhancing the cytotoxicity of therapeutic agents, the distinct roles of the AKT isoforms in NSCLC are largely unknown. In the present study, we investigated the roles of AKT1 and AKT2 in NSCLC cells using RNAi. The siRNA targeting of AKT1 or AKT2 effectively decreased protein levels of AKT1 and AKT2, respectively, in A549 and H460 cells. Cisplatin treatment of these cells increased apoptotic cell death compared with control. The siRNA-induced knockdown of AKT1 in H460 cells significantly decreased basal MEK⁄ ERK1 ⁄ 2 activity, resulting in nuclear factor-κB activation, whereas knockdown of AKT2 resulted in anti-apoptotic Bcl-2 family protein MCL-1 (MCL-1) cleavage, the collapse of mitochondrial membrane potential, cytochrome c release, and activation of the caspase cascade. Consequently, both siRNA treatments enhanced the chemosensitivity of H460 cells to cisplatin. However, neither AKT1 nor AKT2 siRNA treatment had any effect of p27 expression, and although both treatments tended to induced G₂ ⁄M phase arrest, the effect was not statistically significant. Treatment with AKT1 siRNA markedly decreased colony formation growth and migration, but AKT2 siRNA had no significant effects on these parameters. These data suggest that AKT1 and AKT2 both contribute to cell survival, albeit via different mechanisms, and that the effects on cell growth and migration are predominantly regulated by AKT1. These findings may aid in refining targeted strategies for the inhibition of AKT isoforms towards the sensitization of NSCLC cells to therapeutic agents.

BACKGROUND.Irinotecan (I) and cisplatin (P) are active chemotherapy agents with clinical synergy in non–small‐cell lung cancer (NSCLC). We evaluated the efficacy of IP regimen as a salvage treatment of patients with NSCLC that progressed after nonplatinum‐containing regimen(s).METHODS.Eligibility required histologically confirmed NSCLC, bidimensionally measurable disease, ECOG PS 0‐2, and progressive disease after nonplatinum‐based chemotherapy. Treatment consisted of I (65 mg/m2) and P (30 mg/m2) i.v. on Days 1 and 8 of a 21‐day cycle, for a maximum of 6 cycles. An informed consent was obtained from all patients.RESULTS.Between August 2002 and May 2004, 32 patients with median age of 56 years (range, 42–74) were enrolled. Twenty‐four (75%) patients were men, and 28 (88%) had ECOG PS 0 or 1. Twenty‐five patients had adenocarcinoma and 6 had squamous‐cell carcinoma. All patients were evaluated for response and toxicity, and the response rate was 40.6%. After a median follow‐up of 18.5 months, the median survival time was found to be 9.3 months, with a 1‐year survival rate of 43.8%. Toxicities were moderate and manageable, with 47% G3 and 9% G4 neutropenia, 19% G3 diarrhea, and 22% G3 asthenia. There was no G4 nonhematologic toxicity.CONCLUSIONS.The irinotecan and cisplatin combination is an active and well‐tolerated regimen for the patients with advanced NSCLC that progressed after nonplatinum‐containing regimen(s). Cancer 2006. © 2006 American Cancer Society.