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Evaluation of Protein Kinase cAMP-Activated Catalytic Subunit Alpha as a Therapeutic Target for Fibrolamellar Carcinoma

Open AccessPublished:November 08, 2022DOI:https://doi.org/10.1016/j.gastha.2022.11.004
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      Abstract

      Background & Aims

      Fibrolamellar carcinoma (FLC) is a rare, difficult-to-treat liver cancer primarily affecting pediatric and adolescent patients, and for which precision medicine approaches have historically not been possible. The DNAJB1-PRKACA gene fusion was identified as a driver of FLC pathogenesis. We aimed to assess whether FLC tumors maintain dependency on this gene fusion and determine if PRKACA is a viable therapeutic target.

      Methods

      FLC patient-derived xenograft (PDX) shRNA cell lines were implanted subcutaneously into female NOD-SCID mice and tumors were allowed to develop prior to randomization to doxycycline (to induce knockdown) or control groups. Tumor development was assessed every 2 days. To assess the effect of treatment with novel selective PRKACA small molecule kinase inhibitors, BLU0588 and BLU2864, FLC PDX tumor cells were implanted subcutaneously into NOD-SCID mice and tumors allowed to develop. Mice were randomized to treatment (BLU0588 and BLU2864, orally, once daily) or control groups and tumor size determined as above.

      Results

      Knockdown of DNAJB1-PRKACA reversed a FLC-specific gene signature and reduced PDX tumor growth in mice compared to the control group. Furthermore, FLC PDX tumor growth was significantly reduced with BLU0588 and BLU2864 treatment versus control (P = 0.003 and P = 0.0005, respectively).

      Conclusions

      We demonstrated, using an inducible knockdown and small molecule approaches, that FLC PDX tumors were dependent upon DNAJB1-PRKACA fusion activity. In addition, this study serves as a proof-of-concept that PRKACA is a viable therapeutic target for FLC and warrants further investigation.

      Key words

      Abbreviations:

      ATP (adenosine-5'-triphosphate), cAMP (3′ 5′-cyclic adenosine monophosphate), CCC (cholangiocellular carcinoma), cDNA (complementary DNA), CDX (cell line derived xenograft), CPS1 (c arbamoyl phosphate synthetase 1), CREB (cAMP-responsive binding protein), DMEM (Dulbecco’s Modified Eagle Medium), DMSO (dimethyl sulfoxide), DNAJB1 (heat shock protein 40), EDTA (ethylenediaminetetraacetic acid), ESRRA (estrogen related receptor alpha), FLC (fibrolamellar carcinoma), G6PC (glucose-6-phosphatase catalytic subunit), HNF4a (hepatocyte nuclear factor 4 alpha), HCC (hepatocellular carcinoma), IC50 (half-maximal inhibitory concentration), Kd (dissociation constant), NT (non-targeting), PDX (patient-derived xenograft), PKA (protein kinase A), PRKACA (protein kinase cAMP-activated catalytic subunit alpha), PYGL (glycogen phosphorylase, liver form), QD (once daily), SHH (sonic hedgehog), shRNA (short hairpin ribonucleic acid), VASP (vasodilator-stimulated phosphoprotein), WT (wild type)