Yap is an oncogene implicated in the progression of many cancers. However, most research on Yap oncogenic function has been performed in immortalized cell lines that have already undergone many steps of malignant progression. This study will use a HMEC cell culture system that closely models the early steps of breast cancer progression in vivo to understand the function of Yap during early breast cancer progression. Particular emphasis will be place on examining Yap?s role in the crucial step of reactivating telomerase to overcome the replicative senescence barrier, a process that we have shown proceeds in two steps. First Yap causes a change permissive for the acquisition of immortality (termed conditional immortality). Then, the HMEC then need to undergo a variable process (termed conversion) to convert their telomere maintenance mechanisms to support the short stable configuration seen in cancer cells. Preliminary data has led to the following hypothesis: Yap dysregulation during early breast cancer progression alters gene expression and causes cells to be susceptible to acquire cancer properties including conditional immortality and cancer stem cell characteristics. This proposal will rigorously test this hypothesis with three aims. (1) The Yap targets that promote a state permissive for the acquisition of conditional immortality will be determined by performing RNAseq and differential gene expression analysis. (2) Yap induction of cancer stem cell properties early in immortalization will be examined with three assays: qPCR of RNA?s involved in stem cell phenotypes, drug resistance, and formation of mammospheres in 3D culture. The genes downstream of Yap dysregulation that promote these stem cell phenotypes will also be determined. (3) the breast cancer stages in which Yap induces breast cancer progression will be defined by obtaining tissue from normal, DCIS, and increasing breast cancer stages and performing immunofluorescence using antibodies that detect Yap and genes identified in aims 1 and 2 that promote immortalization and cancer stem cell phenotypes. Furthermore, published transcriptome and microarray datasets will be used to determine if Yap and immortalization and cancer stem cell inducing genes downstream of Yap are increased in specific stages of breast cancer. The experiments outlined in this proposal will determine the function of Yap dysregulation during early breast cancer progression and may identify novel therapeutic targets to prevent breast cancer by preventing the immortalization step. The Yap oncogene is implicated in many cancers and immortalization is a barrier in the early progression of most human carcinomas; therefore these novel therapeutic targets could also be relevant to the prevention of most human carcinomas.
The Yap oncogene is implicated in many human cancers. This proposal aims to study the processes downstream of Yap that cause cancer precursor cells to progress towards cancer. Processes that contribute to cancer progression may be important targets of prevention therapeutics that can stop cancer before it can form.
