Yalçın A. (Executive)
TUBITAK Project, 2019 - 2022
Pancreatic adenocarcinoma is one of the deadliest cancers, and incidence is on the rise. Although standard chemotherapy is the only option for many patients, it provides little survival benefit to pancreatic cancer patients. Therefore, novel therapeutic approaches are urgently needed to combat this deadly disease. Activating mutations in the proto-oncogene KRAS are seen in more than %90 of pancreatic adenocarcinomas. Importantly, pancreatic adenocarcinomas are dependent on hyperactive KRAS signaling for the maintenance of neoplastic properties. Efforts aimed at directly targeting KRAS activation have been unsuccessful thus far. However, several recent studies suggest that metabolic dependences that are orchestrated by the oncogenic KRAS and are required for the maintenance of neoplastic properties may provide actionable therapeutic targets, leading to significant success in the treatment of pancreatic cancers.
Tumor cells develop dependency on the exogenous glutamine amino acid for proliferation and the maintenance of neoplastic properties. Therefore, tumor cells are sensitive to genetic and pharmacological inhibition of glutaminase (GLS1), the key enzyme of glutamine metabolism. A specific GLS1 inhibitor called CB-839 is currently being evaluated in multiple phase 1/2 clinical trials. However, CB-839 has not exhibited a significant anti-tumorigenic effect on preclinical pancreatic adenocarcinoma mouse models, which may be associated with metabolic plasticity caused the oncogenic KRAS in pancreatic adenocarcinoma cells. This notion has been supported by studies demonstrating clinical benefit of combinatorial strategies targeting various aspects of pancreatic adenocarcinoma metabolism.
Accelerated aerobic glycolysis is a hallmark of pancreatic adenocarcinoma cells. 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFKFB) enzyme family catalyzes the synthesis and degradation of the glycolytic activator fructose-2,6-bisphosphate (F2,6BP). Preliminary studies demonstrate that the CRISPR/Cas9-mediated targeting of the PFKFB2 isozyme in pancreatic adenocarcinoma cells caused a decrease in glycolytic activity and an increase in the anti-proliferative effect of glutamine withdrawal. This finding supports the hypothesis that combined targeting of PFKFB2 and GLS1 may yield a stronger anti-tumorigenic outcome, as compared to GLS1 targeting alone. To test this hypothesis, in this proposal we aimed to test the effect of CRISPR/Cas9-mediated inactivation of PFKFB2 on the sensitivity of pancreatic adenocarcinoma tumors to GLS1 inhibition in vitro and in vivo. The following specific aims will be pursued toward this end: (1) CRISPR/Cas9-mediated targeting of PFKFB2 in human pancreatic adenocarcinoma cell lines PANC-1, MIA PaCa-2, AsPC-1 and HPAC; (2) determination the effect of PFKFB2 inactivation on the sensitivity of pancreatic adenocarcinoma cells to glutamine withdrawal and GLS1 inhibition by cell proliferation analyses; (3) determination the effect of PFKFB2 inactivation and GLS1 inhibition on pancreatic adenocarcinoma metabolism using isotope-resolved metabolomics approaches; and (4) investigation of the effect of PFKFB2 inactivation on the sensitivity of pancreatic adenocarcinoma xenografts to GLS1 inhbition.
We anticipate that, upon PFKFB2 inactivation, pancreatic adenocarcinoma cells will become more sensitive to the anti-proliferative and anti-tumorigenic effects of the GLS1 inhibitor CB-839. This outcome may provide a rationale for studies that aim to test, as a novel approach, the dual targeting of PFKFB2 and GLS1 in preclinical and clinical settings for the treatment of pancreatic adenocarcinoma.