Abstract 915: Effect of AZD1480 on lung tumor in transgenic mice carrying activating EGFR mutation

Abstract

Abstract Signal transducer and activator of transcription 3 (STAT3) plays a major role in inducing and maintaining a pro-carcinogenic inflammatory microenvironment and is reported to be a critical mediator of the oncogenic effects of epidermal growth factor receptor (EGFR) mutations. STAT3 activation is mediated through the Janus family kinases (JAK) and SRC. JAK1/2 inhibitors such as AZD1480 suppress activation of STAT3 in human solid tumor cell lines and xenografts. Furthermore, they show anticancer effects in various cancer cell lines and xenograft models, including lung cancer. However, the effect of the JAK inhibitors on non-small cell lung cancer harboring EGFR mutation remains unclear. PC-9 is a lung adenocarcinoma cell line harboring exon19 EGFR deletion mutation. Four EGFR tyrosine kinase inhibitors-resistant cell lines, RPC-9, PC-9/Van-R, PC-9/ER3 and PC-9/GR, were established from PC-9 in our laboratory and the resistant mechanisms were mainly caused by a secondary mutation of T790M, JAK2 overexpression or ERK reactivation. Growth inhibition was measured by MTT assays. The drug concentration required to inhibit the growth of tumor cells by 50% (IC50) for 96 h exposure was used to evaluate the effectiveness of AZD1480. Protein expression was determined by Western blotting. The IC50s were 2.4 μM for PC-9, 1.7 μM for RPC-9, 1.2 μM for PC-9/Van-R, 1.2 μM for PC-9/ER3 and 1.6 μM for PC-9/GR. Thus, no cross-resistance was observed. Phosphorylated JAK2 and phosphorylated STAT3 were suppressed by treatment with AZD1480. We generated transgenic mice expressing the delE748-A752 mutant of mouse Egfr, which corresponded to the delE746-A750 mutant of human EGFR. In the absence of treatment, the transgenic mice developed adenocarcinoma at 6 to 7 weeks of age and died due to tumor progression at 13 to 18 weeks. To investigate the effect of AZD1480 on lung tumors induced by an activating EGFR mutation, the transgenic mice were treated with oral AZD1480 (30 mg/kg/day) or vehicle alone from 7 to 10 weeks of age. The number of lung tumors (long axis exceeding 1 mm) ± SE in the AZD1480-treated group and control group was 0.37 ± 0.18 and 2.25 ± 0.53 (t-test, p<0.001), respectively. Immunohistochemistry and Western blotting showed that phosphorylation of STAT3 was suppressed during AZD1480 treatment. To evaluate the efficacy of AZD1480 on survival in EGFR transgenic mice, AZD1480 (30 mg/kg/day, n = 13) or vehicle (n = 13) was administered orally from 7 weeks of age. The median survival time in the AZD1480-treated group (217 days) was significantly longer than that in the control group (106 days) (logrank test, p<0.0001). In conclusion, AZD1480 may be effective for treatment of lung tumors induced by an activating EGFR mutation and may overcome the resistance to EGFR-tyrosine kinase inhibitors. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 915. doi:1538-7445.AM2012-915