Targeting Ire1a-Xbp1 Signaling In Lung Cancer

Every year 1.5 million people die from lung cancer worldwide. Approximately ~15-30% of non small cell lung cancers (NSCLC) are driven by KRAS mutations and currently possess no viable therapeutic options. As such the discovery of effective therapeutic alternatives for the treatment of KRAS driven NSCLC are sorely needed. One prospect being explored in other solid tumors, but currently unexplored in NSCLC, is targeting the endoplasmic reticulum (ER) stress response. Adverse conditions in tumors such as hypoxia, nutrient starvation and reactive oxygen species disrupt protein folding, and induce ER stress. The most evolutionarily conserved pathway by which this insult is alleviated is the IRE1α-XBP1 axis, which responds by increasing the expression of a broad range of protein folding and quality control genes. Previous work has demonstrated that several cancers utilize this pathway to promote tumorigenesis, progression, epithelial to mesenchymal transition and metastasis. A preliminary analysis of a tissue microarray containing 304 human NSCLC samples, 254 demonstrated at least some positivity and u003e50% were strongly positive for the active isoform of XBP1. Given these preliminary findings we investigated the status of IRE1a-XB1 in our murine orthotopic model and confirmed the activation of IRE1a-XBP1 signaling in tumor cells in the context of the tumor microenvironment. Furthermore, in both cell types we can see the activation of canonical downstream targets of XBP1. Utilizing the CRISPR-CAS9 system, we knocked out IRE1a in the orthotopic tumor cell line. IRE1a abrogation was confirmed by western blot, evaluating the fraction of active XBP1 after induced ER stress in vitro, and qPCR of canonical downstream targets. Additionally, this knockout did not alter proliferation or morphology in vitro. However, when tumors were grown orthotopically, Cas9-IRE1a knockouts failed to grow past 10 days, whereas Cas9-Scramble controls and the parental tumor line grew comparably until end stage. Given these preliminary findings and data from prior studies, we hypothesize that the abnormal activation of the IRE1α-XBP1 axis may influence KRAS NSCLC progression and aggressiveness and serve as a potential novel avenue for the treatment of NSCLC. After probing the impact of the underlying mechanism on tumor growth we will finally evaluate the translational utility of targeting the ER stress pathway with a small molecule inhibitor against IRE1a. Citation Format: Michael J. Crowley, Shira Yomtoubian, Geoffrey Markowitz, Nasser K. Altorki, Dingcheng Gao, Juan Cubillos-Ruiz, Vivek Mittal. Targeting IRE1a-XBP1 signaling in lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4498. doi:10.1158/1538-7445.AM2017-4498