Mitochondria are dynamic organelles that undergo fission and fusion to respond to various cellular cues and maintain proper mitochondrial function. In particular, disruptions in Dynamin-related protein 1 (Drp1)-mediated mitochondrial fission have been implicated in a variety of pathologies, including pancreatic cancer. Pancreatic cancer is the 3rd leading cause of cancer related deaths in the US with incidence and mortality expected to rise in the coming decades and limited therapeutic options. Over 90% of cases of pancreatic ductal adenocarcinoma (PDAC) harbor an activating KRAS mutation. Our lab recently demonstrated that activated Ras promotes activation of Drp1, which is necessary for tumor growth in a subcutaneous xenograft model. In addition, our lab demonstrated that patient-derived pancreatic cancer specimens exhibit activated Drp1. However, there remains a gap in our knowledge of how Drp1 mediates its pro-tumorigenic effects. This proposal aims to determine which physiological processes Drp1 mediates that promote tumor growth in pancreatic cancer. To do this, we will utilize both a genetically engineered mouse model of pancreatic cancer as well as a patient-derived orthotopic xenograft system. We have generated a mouse (KPDC) characterized by pancreas-specific expression of mutant Kras and deletion of both alleles of p53 and Drp1. Preliminary data from this mouse indicates that loss of Drp1 confers a survival advantage to the mice. Using cell lines derived from KPDC tumors, preliminary evidence suggests a selective pressure against deletion of both alleles of Drp1. Additional preliminary studies indicate that cells lacking Drp1 have altered metabolism, in particular lipid metabolism. Given these observations as well as evidence from literature, we hypothesize that Ras driven, Drp1 activation promotes physiologic changes that contributes to pancreatic tumor growth.
In Specific Aim 1, I will use histologic analyses on our KPDC mice to understand the function of Drp1 in tumor progression, proliferation, apoptosis, and metabolism in vivo. I will use our KPDC cell lines to perform standard in vitro assays to complement our in vivo findings and gain a more mechanistic understanding of those physiologic processes.
In Specific Aim 2, I will generate a doxycycline-inducible shDrp1 system in a panel of genetically and phenotypically heterogeneous patient-derived cell lines. We will orthotopically xenograft those cells and induce knockdown of Drp1 during and after tumor establishment to determine the role of Drp1 in tumor maintenance, progression, and metastasis. Successful completion of this work will reveal how Drp1 promotes pancreatic tumor growth and provide greater rationale for Drp1 as a therapeutic target in PDAC.
Pancreatic cancer is an extraordinarily lethal disease that urgently needs new drug targets to be identified, since both incidence and mortality are expected to rise in the coming decades. Our lab has recently demonstrated that activated Ras, commonly mutated in pancreatic cancer, promotes activation of the mitochondrial fission GTPase Dynamin-related protein 1 (Drp1) and that this activation of Drp1 is needed for tumor growth. This proposal aims to determine the role of Drp1 in the physiological processes necessary for tumor growth using murine models and clinically relevant orthotopic xenografts of patient-derived cells. If successful, these studies will reveal novel mechanisms into how Drp1 promotes pancreatic tumor growth. In addition, these studies may reveal Drp1 as a therapeutic target for pancreatic cancer and provide insight into potential combinatorial treatments to combat this disease.
| Nagdas, Sarbajeet; Kashatus, David F (2017) The Interplay between Oncogenic Signaling Networks and Mitochondrial Dynamics. Antioxidants (Basel) 6: |
