Liver Kinase B1 (LKB1/STK11) signaling pathway has an established role in defining cellular responses to changes in energy homeostasis and metabolism. LKB1 signaling functions through a set of 14 kinase targets which provide distinct contributions and cell-type specific regulation of the LKB1 signaling axis. Beyond its role in energy homeostasis, metabolism, cell polarity and stress responses, LKB1 expression and activity has an important role as a tumor suppressor. Its role as a tumor suppressor is observed by its genomic loss in Peutz- Jeghers Syndrome which leads to increased lifetime risk of a number of malignancies as well as somatic mutation of LKB1 expression or function resulting in a number of solid tumor cancers. While more recent studies have begun to expand upon our understanding of LKB1 signaling and its mechanisms, there has been limited investigation into defining the individual contributions of its kinase targets in the regulation of the cancer phenotype. We have been investigating LKB1 signaling in breast cancer and have demonstrated a role for LKB1 in selective suppression of in vitro invasion and in vivo metastasis. We have further begun to define the kinase targets of LKB1 required for activity and demonstrated regulation of gene expression, transcription factor targeting and altered metabolism. The objective in this proposed project is to define the role of LKB1 and its downstream signaling and gene expression networks as potential therapeutic targets in the regulation of breast cancer invasion and metastasis. We have proposed the overall hypothesis that an LKB1 signaling axis, through downstream NUAK2 and SIK1, targets invasion and EMT related gene expression coordinate to suppression of metastasis in basal sub-type breast cancer. To accomplish this we proposal the following aims:
Aim 1 - To define the role for and mechanisms of LKB1 signaling in sub-type selective regulation of breast cancer cell tumorigenesis and metastasis, Aim 2- To test the requirement for downstream kinase targets of LKB1 signaling axis that selectively suppresses the invasive phenotype, Aim 3- To identify the role and mechanisms of direct NUAK2 and SIK1 signaling in suppression of breast cancer cell invasion and metastasis. This research will have an impact in several key areas. A- We are focusing on defining the breast cancer sub- type selective effects of LKB1 signaling. By defining the contribution of LKB1 and target kinases in basal versus Her2/neu or luminal sub-types we expect to define its unique role, mechanism of action and most importantly a translation of our findings into the clinical setting by sub-type selective targeted therapy for breast cancers. B- We seek to define the mechanisms by which the LKB1 axis suppresses invasion/metastasis in our breast cancer systems. By defining the kinome-transcriptome pathways that distinctly regulate the metastatic and metabolic phenotype of breast cancer we hope to define novel avenues of therapeutic targeting and earlier interventions that target the primary tumor preventing the metastatic spread of the disease.
Genomic sub-typing of breast cancer offers us the opportunity to understand unique molecular programs of individual breast cancer phenotypes that are uniquely tractable to individualized therapy. Our proposal seeks to define the role and mechanisms of the LKB1 signaling axis in suppression of the invasive and metastatic phenotype of the highly aggressive basal-B sub-type of breast cancer. Through this we hope to define novel approaches and therapeutic targets in the treatment of advanced breast cancer as well as the prevention of metastatic disease.
