The PI3K/AKT pathway promotes gefitinib resistance in mutant KRAS lung adenocarcinoma by a deacetylase-dependent mechanism.

To select the appropriate patients for treatment with epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs), it is important to gain a better understanding of the intracellular pathways leading to EGFR-TKI resistance, which is a common problem in patients with lung cancer. We recently reported that mutant KRAS adenocarcinoma is resistant to gefitinib as a result of amphiregulin and insulin-like growth factor-1 receptor overexpression. This resistance leads to inhibition of Ku70 acetylation, thus enhancing the BAX/Ku70 interaction and preventing apoptosis. Here, we determined the intracellular pathways involved in gefitinib resistance in lung cancers and explored the impact of their inhibition. We analyzed the activation of the phosphatidyl inositol-3-kinase (PI3K)/AKT pathway and the mitogen-activated protein kinase/extracellular-signal regulated kinase (MAPK/ERK) pathway in lung tumors. The activation of AKT was associated with disease progression in tumors with wild-type EGFR from patients treated with gefitinib (phase II clinical trial IFCT0401). The administration of IGF1R-TKI or amphiregulin-directed shRNA decreased AKT signaling and restored gefitinib sensitivity in mutant KRAS cells. The combination of PI3K/AKT inhibition with gefitinib restored apoptosis via Ku70 downregulation and BAX release from Ku70. Deacetylase inhibitors, which decreased the BAX/Ku70 interaction, inhibited AKT signaling and induced gefitinib-dependent apoptosis. The PI3K/AKT pathway is thus a major pathway contributing to gefitinib resistance in lung tumors with KRAS mutation, through the regulation of the BAX/Ku70 interaction. This finding suggests that combined treatments could improve the outcomes for this subset of lung cancer patients, who have a poor prognosis.

Jeannot V ，Busser B ，Brambilla E ，Wislez M ，Robin B ，Cadranel J ，Coll JL ，Hurbin A ... -  《-》

Insulin-like growth factor-1 receptor inhibition overcomes gefitinib resistance in mucinous lung adenocarcinoma.

The appropriate selection of patients is a major challenge in the treatment of non-small cell lung cancer (NSCLC) with epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs). Prospective trials in adenocarcinoma demonstrated that the mucinous subtype presents a poorer outcome under EGFR-TKI treatment than the non-mucinous subtype. Our aim was to determine the molecular characteristics associated with resistance to EGFR-TKIs in mucinous and non-mucinous adenocarcinoma. Eighty adenocarcinoma samples, including 34 tumours from patients treated with gefitinib in a phase II clinical trial (IFCT0401), were classified as mucinous (n = 32) or non-mucinous (n = 48) adenocarcinoma. We demonstrated that four biological markers were differentially expressed between the two subtypes: mucinous tumours that overexpressed IGF1R (p < 0.0001) and amphiregulin (p = 0.004) with a tendency for more frequent KRAS mutations, in contrast to non-mucinous tumours that overexpressed EGFR (p < 0.0001) and TTF-1 (p < 0.0001) with more frequent EGFR mutations (p = 0.037). Higher IGF1R (p = 0.02) and lower TTF-1 (p = 0.02) expression was associated with disease progression under gefitinib treatment. We observed in vitro cross-talk between EGFR and IGF1R signalling pathways in gefitinib-resistant H358 mucinous cells. Anti-amphiregulin siRNAs and anti-IGF1R treatments sensitized the H358 cells to gefitinib-induced apoptosis with additive effects, suggesting that these treatments could overcome the resistance of mucinous tumours to EGFR-TKIs, including those with KRAS mutation. Our results highlighted that mucinous and non-mucinous adenocarcinoma subtypes are different entities with different therapeutic responses to EGFR-TKIs. These data will foster the development of therapeutic strategies for treating adenocarcinoma with mucinous component.

Hurbin A ，Wislez M ，Busser B ，Antoine M ，Tenaud C ，Rabbe N ，Dufort S ，de Fraipont F ，Moro-Sibilot D ，Cadranel J ，Coll JL ，Brambilla E ... -  《-》

Transient PI3K inhibition induces apoptosis and overcomes HGF-mediated resistance to EGFR-TKIs in EGFR mutant lung cancer.

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKI), such as gefitinib and erlotinib, show favorable response to EGFR mutant lung cancer. However, the responders acquire resistance almost without exception. We recently reported that hepatocyte growth factor (HGF) induces EGFR-TKI resistance by activating MET that restores downstream mitogen activated protein kinase (MAPK)/extracellular signal regulated kinase (ERK)1/2 and phosphoinositide 3-kinase (PI3K)/Akt signaling. The purpose of this study was to determine whether inhibition of PI3K, a downstream molecule of both EGFR and MET, could overcome HGF-mediated EGFR-TKI resistance in EGFR mutant lung cancer cells PC-9 and HCC827. We explored therapeutic effect of a class I PI3K inhibitor PI-103 on HGF-induced EGFR-TKI resistance in vitro and in vivo. Unlike gefitinib or erlotinib, continuous exposure with PI-103 inhibited proliferation of PC-9 and HCC827 cells, even in the presence of HGF. On the other hand, in gefitinib-resistant xenograft model by using PC-9 cells mixed with HGF high producing fibroblasts, PI-103 monotherapy did not inhibit tumor growth. However, PI-103 combined with gefitinib successfully regressed gefitinib-resistant tumor. In vitro experiments by considering short half-life of PI-103 reveal that transient exposure of PI-103 combined with gefitinib caused sustained inhibition of Akt phosphorylation, but not ERK1/2 phosphorylation, resulting in induction of tumor cell apoptosis even in the presence of HGF. These results indicate that transient blockade of PI3K/Akt pathway by PI-103 and gefitinib could overcome HGF-mediated resistance to EGFR-TKIs by inducing apoptosis in EGFR mutant lung cancer.

Donev IS ，Wang W ，Yamada T ，Li Q ，Takeuchi S ，Matsumoto K ，Yamori T ，Nishioka Y ，Sone S ，Yano S ... -  《-》

Gefitinib (IRESSA) sensitive lung cancer cell lines show phosphorylation of Akt without ligand stimulation.

Noro R ，Gemma A ，Kosaihira S ，Kokubo Y ，Chen M ，Seike M ，Kataoka K ，Matsuda K ，Okano T ，Minegishi Y ，Yoshimura A ，Kudoh S ... -  《BMC CANCER》

Knockdown of the Bcl-2 gene increases sensitivity to EGFR tyrosine kinase inhibitors in the H1975 lung cancer cell line harboring T790M mutation.

Zou M ，Xia S ，Zhuang L ，Han N ，Chu Q ，Chao T ，Peng P ，Chen Y ，Gui Q ，Yu S ... -  《-》