Timeframe: 2021 – 2023
Goal: Investigate the potential of heat shock protein 70 (Hsp70) and kinase inhibitors as potential therapeutic options in pre-clinical models
Principal Investigator: John Scott, PhD
Study overview: In the previously funded work, the investigators discovered that DNAJ-PKAc forms a complex with heat shock protein 70 (Hsp70) and mitogenic kinases (kinase enzymes that function in the cell proliferation pathway) by acting as a scaffold. This feature creates a subcellular focal point for the transmission of aberrant chemical signals throughout FLC tumors and may be recruiting a host of other protein beyond what has been already reported. Pharmacological targeting of these oncogenic focal points was the next logical step in the continuum of this research. The goals of this study were:
- Determine if FLC is driven by the DNAJ-PKAc kinase activity or by association with oncogenic binding partners.
- Test efficacy of Hsp70/kinase inhibitor combinations in human FLC cells, organotypic tumor slices, hepatic organoids expressing the chimeric protein and PDX models.
Results: The investigators used a proximity assay to characterize the range of binding partners for DNAJ-PKAc ‘scaffold’ as compared to the native protein. Results showed that the fusion protein is promiscuous (binds to various partners) as compared to the native protein. Within these wide range of binding partners, they discovered increased association of Bcl2-associated athanogene 2 (Bag 2), with the fusion protein. Bag2 is a co-chaperone protein linked to Bcl2, an anti-apoptotic factor (an inhibitor of programmed cell death which can contribute to the development of cancer), which was also observed at elevated levels in FLC patient samples. Treatment of hepatocyte cell lines overexpressing the DNAJ-PKAc fusion protein with drug combinations targeting this DNAJ-PKAc/Bag2 axis confirmed a chemoresistant function of Bag2, which could explain the increased levels of this protein seen in FLC samples. This observation opened up potential therapeutic targets.
Implications: This study provided a strong candidate for therapeutic target explorations. Bag2 interacts with Bcl-2, which is an anti-apoptotic protein. Several targeted therapies against Bcl-2 are used for treatment of a wide range of cancers. However, targeting Bcl-2 in FLC has not been successful, so possible combinations of therapies targeting Bcl2 and associated factors, such as Bag2 could be a good strategy for FLC.