Abstract 5227: Multimodality approaches to treat hypoxic NSCLC tumor microenvironment

Abstract

Abstract In a previous study we found both in vitro and in an orthotropic NSCLC model in SCID mice that survival of NSCLC cells in hypoxic microenvironment is dependent upon Notch-1 signaling. Active Notch-1 was expressed in hypoxic tumor microenvironment only. Notch-1 provides survival stimuli through exacerbated Akt-1 activation due to suppression of PTEN transcription and positive regulation of the transcription of IGF-1 and its receptor. Hypoxic tumor environment is a problem for NSCLC treatment because it is responsible for cancer resistance to chemotherapy, tumor recurrence and metastasization. Also, hypoxic tumor microenvironment is quiescent and represses mTORC-1 activity. We show a number of experiments aimed at targeting hypoxic tumor tissue in the orthotropic NSCLC model. We attempted to target the Notch-1/IGF-1R/Akt-1 axis using three agents (a γ-secretase inhibitor, MRK-003; a fully humanized antibody against the human IGF-1R that promotes the receptor degradation, MK-0646; a pan-Akt inhibitor, MK-2206, all drugs provided by Merck Inc.) alone or in various combinations. We also used in combination studies drugs that are used for the treatment of advanced NSCLC, namely cisplatin and Erlotinib. The orthotropic model was established using two cell lines non-dependent on Notch-3 signaling. siRNA to Notch-3 in A549 and H1437 affects neither the growth rate nor the survival of these cells. All treatments (besides MK-2206) significantly prolonged the median survival of mice compared to controls (16 mice/experimental arm). MRK-003 treatment yielded specific death of hypoxic tumor areas. The tumors excised from the mice reaching an end-point displayed a significant reduction of markers of hypoxia as assessed by RT-qPCR using human specific primers. Moreover, qPCR measurements of the ratio between human/mouse GAPDH in DNA extracted from the whole brains and livers showed a significant reduction in metastasization in MRK-003 treated mice. MK-0646 was not specific to hypoxic tumor environment, but substantially increased the median survival of treated mice compared to controls. NSCLC cells evaded MK-0646 treatment by activating EGF-R and ErbB3 exclusively both in vivo and in five cell lines in vitro. This phenomenon is achieved at the level of protein stability. One outcome of MK-0646 treatment is that cells poorly or not responsive to Erlotinib become more responsive to it. Sequential treatment with MK-0646 (three weeks), then combination of MK-0646 plus Erlotinib prolonged median survival of mice dramatically. If the two drugs where administered in combination from day one no survival advantage was observed in median survival compared to mice treated with Erlotinib alone and was actually less effective than MK-0646 used as single agent. 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 5227. doi:1538-7445.AM2012-5227