According to the cancer stem cell hypothesis, the growth of cancers is driven by long-lived tumor cells that are capable of self-renewal and differentiation. Using the mammalian intestine as a model system, we sought to identify novel molecular pathways regulating Lgr5+ cancer stem cells. Given the central role of Akt in cancer cell fate, differentiation, and proliferation, we interrogated a definitive analysis of the Akt phosphoproteome by the Tsichlis laboratory to identify novel Akt phosphorylation substrates that are enriched in intestinal stem cells and intestinal tumors. Of 22 candidate targets, we selected Mtss1 for further study. We determined that Akt- specific phosphorylation of Mtss1 drives intestinal carcinogenesis and Lgr5+ stem cell clonogenicity in in vitro cell and organoid models by activating Hedgehog signaling. The goal of the current proposal is to study the role of Mtss1 in Hedgehog-mediated tumorigenesis and stem cell function. In the first aim of the proposal, we will examine the role of Mtss1-dependent Hedgehog signaling in intestinal tumorigenesis. In the second aim of the proposal, we will determine the role of Mtss1 in Lgr5+ intestinal cancer stem cell function. Finally, in the third aim of the proposal, determine the role of Mtss1-dependent Hedgehog signaling in Lgr5+ intestinal cancer stem cell function. Our proposal is expected to elucidate Akt and Hedgehog-dependent mechanisms of cancer stem cell function that will provide new therapeutic directions for targeting Lgr5+ tumor stem cells in colorectal, ovarian, gastric, and hepatocellular cancers.
Cancers are thought to originate from a small subpopulation of cancer stem cells that are long-lived and often resistant to standard therapies. Using the mouse intestine as a model system, we derived three-dimensional, heterogeneous tumor cultures that express important colorectal cancer stem cell markers and can be transplanted into colons of recipient mice. The goal of the proposed research is to use these models to identify mechanisms that promote growth of cancer stem cells in order to devise treatments that prolong and improve the lives of patients with cancer.
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