A fundamental, hard-wired response to oncogenic transformation is enhanced cellular stress (for example, oxidative, replicative, metabolic, ER stress, and DNA damage) that is a hallmark of cancer cells. These common stress phenotypes must be tolerated by cancer cells through stress support pathways. Moreover, adaptation to stress is required for cancer cell survival, and consequently cancer cells may become dependent on stress response pathways that do not ordinarily perform such a vital function in normal cells. Thus, targeting these associated vulnerabilities to stress adaptation are clearly paramount and offer a tremendous window of opportunity for a synthetic lethal interaction that may elicit selective death of cancer cells. Despite the tremendous importance of the stress phenotype of cancer cells, there is a large gap in our understanding of the genetic basis for how stress tolerance is maintained in transformed cells, thereby limiting our ability to design rationa therapeutic agents. Cells require adaptation responses in gene expression to respond to cellular stress. Strikingly, our findings reveal that the major cap binding protein eIF4E is unexpectedly a central integrator of the translation program for the adaption of cancer cells to oncogenic stress. By generating the first genetic loss-of-function mouse model for eIF4E, we have unexpectedly discovered that 50% reductions in eIF4E have no effect on normal development or cellular function but instead are specifically limiting for oncogenic transformation. Utilizing unbiased genome-wide translational profiling, we find that eIF4E is selectively limiting for the translationof specific subsets of mRNAs involved in cellular stress response pathways, including oxidative stress (e.g. Fth1, Gclc,) and ER stress (e.g. Atf6, XBP-1), at least in part, through a novel cis-acting regulatory sequence in their 5'UTRs that sensitizes these mRNAs to eIF4E dosage. Moreover, our preliminary data demonstrate that eIF4E-dependent control of these stress response pathways is critical for tumor cell survival and oncogenic transformation. These findings lay the foundation for this proposal, which seeks to open a new portal into our understanding of the translation program that maintains the adaptation of cancer cells to stress and develops a novel therapeutic regimen to target this vulnerability of transformed cells.
In Aim 1, we will assess the role of eIF4E dependent control of oxidative stress in non-small cell lung carcinoma in vivo.
In Aim 2, we will define the molecular mechanism by which eIF4E directs the stress-induced oncogenic translation program through a novel cis-acting regulatory element.
In Aim 3, we will determine the contribution of eIF4E to cellular transformation through translational control of the unfolded protein response (UPR).
Cancer cells survive enhanced cellular stress, a hallmark of cancer resulting from oncogenic transformation, by triggering stress response pathways that are not normally required for non-transformed cells, which represents a new vulnerability in cancer cells that holds the potential to be therapeutically targeted. In this proposal, we will employ novl genetic, pharmacologic and mass spectrometry approaches to characterize the mechanisms by which the stress-induced gene expression program promotes lung cancer development. Our important findings will provide the rationale to usher in a new line of therapeutics that will specifically and effectively exploit the dependency of cancer cells, but not normal cells, in control of the oncogenic stress response pathway.
