Pancreatic ductal adenocarcinoma (PDAC) is among the most devastating of all cancers. It is responsible for only 3% of cancer cases annually but is the cause of over 7% of cancer related deaths. Despite the prevalence of this diseases there remains a scarcity of rational targeted chemotherapies.
The most frequently observed driver mutation in PDAC is in the KRAS gene. KRAS is a GTPase protein in the RAS-RAF-MEK-ERK (MAPK) pathway. This pathway regulates vital functions necessary for cell proliferation, differentiation, and survival. Unfortunately, efforts to pharmacologically inhibit KRAS have been unsuccessful.
PDAC can be subdivided into two classes: KRAS-dependent and KRAS-independent. KRAS-dependent cell lines acquire numerous genetic mutations yet still require sustained activity of the KRAS protein to survive. These two subtypes of PDAC have distinct genetic and morphological features. One such difference is expression of the Spleen tyrosine kinase (Syk), which is expressed at higher levels in KRAS-dependent cell lines.
Syk is a non-receptor tyrosine kinase that functions downstream of KRAS and is an upstream activator of mTORC1. mTORC1 activity is associated with anabolic processes such as protein and lipid synthesis, while its suppression causes activation of the catabolic autophagy pathway. Like KRAS, mTORC1 has proven to be a poor drug target in clinical studies. This issue necessitates the discovery of other therapeutic targets in the pathway. Inhibiting Syk with the inhibitor PRT062607 (Syki) results in decreased mTORC1 activity, increased autophagy, and cell death.
In this study we aim to identify compounds that act synergistically with Syki to produce an enhanced therapeutic effect. Synergy can be summarized as a combinational effect greater than the expected additive effect of each agent acting individually. We evaluated the effects of various drug combinations on cell viability and studied the impact of these compounds on the autophagy pathway.
We found a synergistic killing effect when cells were treated with Syki and the iron-chelating agent Nocardimicin F (NCF). Live cell imaging assays showed that NCF is a strong activator of the autophagy pathway. Western Blot data suggest that NCF activates the autophagy pathway through a mechanism independent of mTORC1 suppression. Furthermore, our data suggest that the cytotoxicity of Nocardimicin does not result from induction of apoptosis. We hypothesize that cell death proceeds via an autophagy dependent mechanism called autosis. Autosis is a poorly understood process, however, is known to be dependent on the Na+/K+-ATPase. Our findings provide rationale for further study of the effects of iron-chelating compounds in PDAC and suggest that targeting the autophagy pathway is a viable therapeutic strategy.
| Identifer | oai:union.ndltd.org:bu.edu/oai:open.bu.edu:2144/43515 |
| Date | 04 December 2021 |
| Creators | Parzick, James Cole |
| Contributors | Singh, Anurag |
| Source Sets | Boston University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
Page generated in 0.0024 seconds