Abstract PR3: NSCLC and SCLC mouse models mediated by lentiviral gene delivery
Authors: Xia Yifeng , Yeddula Narayana , Leblanc Mathias , Shaw Reuben , Verma Inder 
Published: March 2013

Lung cancer, the leading cause of cancer deaths, is responsible for 1.3 million lives lost worldwide every year. Good animal models that can faithfully recapitulate the human disease are in great need for pre-clinical studies. Based on the different responses to treatment, lung cancer is divided into two major classes: small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC). We have developed a novel lentiviral gene delivery system to study the initiation and development of both types of lung cancer. We use lentiviral vectors to establish lung tumors in mice for the following reasons: 1) lentiviruses infect almost any type of cells, and transgene expression can be controlled by a tissue-specific promoter, which allows a more precise tracing of the origin of the cancer cell; 2) lentiviruses integrate into genomic DNA so that it is possible to stably deliver oncogenes and shRNAs against tumor suppressors, and bypass the requirement of numerous conventional genetic crossings; 3) viral titers can be controlled so as to infect only a few cells, in order to more precisely recapitulate human cancer initiation.

We used CA2Cre-shp53 lentiviral vector to initiate lung adenocarcinoma in KrasG12D mice and studied the role of NF-κB/IKK2 in tumor development. We found that IKK2 depletion in tumor cells significantly attenuated tumor proliferation and significantly prolonged mouse survival. We identified Timp-1 (a tissue inhibitor of metalloproteinases), one of the NF-κB target genes, as a key mediator for tumor growth. Timp-1 binds to its receptor CD63, activates Erk signaling pathway and stimulates cell proliferation. Knockdown of either IKK2 or Timp-1 by shRNAs reduced tumor growth in both xenograft and lentiviral models, suggesting the possible application of IKK2 and Timp-1 inhibitors in treating lung cancer. Due to the safety concerns of systemic NF-κB inhibition, IKK2 inhibitors haven't been applied to the clinical trials. Our identification of Timp-1 may serve as an alternative target for blocking tumor proliferation. Timp-1 neutralizing antibodies are currently being tested to treat mice carrying Kras adenocarcinomas.

SCLC is the most malignant form of lung cancer with a five-year survival less than 6%. A mouse model with p53/Rb deletions activated by Adeno-Cre has been established in Berns lab. To improve the model and study other genes that are frequently mutated in human SCLC, we designed a single lentiviral vector to deliver oncogenes (L-myc) and shRNAs against tumor suppressors (p53, Rb etc) and successfully initiated SCLC in wild-type mice. Furthermore, we included luciferase or fluorescence protein genes in the same vector to follow tumor growth and metastasis in the live animal. Using this new model, we are now studying the crosstalk of multiple mutations in the SCLC development.

We hope that our unique lentiviral tool can simplify and accelerate the lung cancer study to understand the big signal pathway complex leading to tumorigenesis in the lung and search for new therapies for this deadly human disease.

This abstract is also presented as Poster A45.