Role of JNK Pathway in Lung Tumorigenesis

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DESCRIPTION (provided by applicant): K-Ras and mutated/over-expressed EGFR family members function as dominant oncogenes in non-small cell lung cancer (NSCLC). Yet, the signal pathways that mediate transformation by these oncogenes remain ill-defined. Moreover, oncogenes stimulate both pro- and anti-tumorigenic signaling. In this regard, the JNK MAPKs, encoded by jnk1, jnk2 and jnk3, are activated by growth factors and oncogenes and the literature documents both positive and negative roles for JNKs in cellular transformation. MKK4, a dual-specificity kinase activator of the JNKs, has emerged as a tumor metastasis suppressor in diverse human cancers. Consistent with this finding, our experiments with JNK1 and JNK2-deficient mice reveal increased carcinogen-induced lung tumorigenesis relative to wild-type littermates. Also, multiple human NSCLC cell lines show decreased JNK activity relative to non-transformed lung epithelial cells and transfected gain-of-function JNK1 inhibits anchorage-independent NSCLC growth. Thus, we propose that JNK1 and JNK2 function as components of a tumor suppressor pathway in lung cancer. By contrast, preliminary studies with JNK3- deficient mice reveal decreased carcinogen-induced lung tumorigenesis. In addition, JNKS mRNA and protein is expressed in NSCLC cell lines and primary tumors relative to non-transformed lung epithelial cells or uninvolved lung tissue. Thus, we hypothesize that JNK3 is induced during lung cancer progression and represents a pro-tumorigenic JNK isoform. To test these hypotheses, we will complete the following specific aims. Aim 1: Determine the in vivo role for specific JNKs in murine lung tumorigenesis with mice lacking jnk1, jnk2 or jnk3. The role of specific JNKs as signal components of the host lung microenvironment regulating lung tumorigenesis will also be tested. Aim 2: Test the in vitro role of specific JNKs in tumor suppression or cellular transformation. Non-transformed lung epithelial cell lines expressing molecular inhibitors of the JNKs will be transduced with oncogenic K-Ras and criteria of transformation, differentiation and apoptosis will be measured. Also, NSCLC cells transduced with gain-of-function JNKs or dominant-negative JNKS will be monitored for criteria of cellular transformation. Aim 3: Define the mechanism(s) accounting for decreased JNK1 and JNK2 activity in NSCLC cell lines. The role of MKPs as oncogene-induced negative regulators of JNK1 and JNK2 activity will be highlighted. Aim 4: The activation state of JNKs and expression status of specific signaling molecules defined in Aims 1-3 will be measured in archived primary human lung tumors with IHC and quantitative RT-PCR and correlated with clinical behaviour. Completion of these specific aims will lead to a comprehensive understanding of the complex role of this family of MAP kinases in lung tumorigenesis and provide a format for exploration of the role of these kinases in other human cancers. Furthermore, a detailed understanding of the multi-faceted role of the JNK MAP kinases in lung cancer is absolutely required for rationale and precise therapeutic targeting of this pathway to combat lung cancer.