Genomic and biological aspects of resistance to selective poly(ADP-ribose) glycohydrolase inhibitor PDD00017273 in human colorectal cancer cells

by Selleckchem | Sep 04 2023

Background: Poly(ADP-ribose) glycohydrolase (PARG) is a key enzyme in poly(ADP-ribose) (PAR) metabolism and a potential anticancer target. Many drug candidates have been developed to inhibit its enzymatic activity. Additionally, PDD00017273 is an effective and selective inhibitor of PARG at the first cellular level.

Aims: Using human colorectal cancer (CRC) HCT116 cells, we investigated the molecular mechanisms and tumor biological aspects of the resistance to PDD00017273.

Methods and results: HCT116RPDD , a variant of the human CRC cell line HCT116, exhibits resistance to the PARG inhibitor PDD00017273. HCT116RPDD cells contained specific mutations of PARG and PARP1, namely, PARG mutation Glu352Gln and PARP1 mutation Lys134Asn, as revealed by exome sequencing. Notably, the levels of PARG protein were comparable between HCT116RPDD and HCT116. In contrast, the PARP1 protein levels in HCT116RPDD were significantly lower than those in HCT116. Consequently, the levels of intracellular poly(ADP-ribosyl)ation were elevated in HCT116RPDD compared to HCT116. Interestingly, HCT116RPDD cells did not exhibit cross-resistance to COH34, an additional PARG inhibitor.

Conclusion: Our findings suggest that the mutated PARG acquires PDD00017273 resistance due to structural modifications. In addition, our findings indicate that PDD00017273 resistance induces mutation and PARP downregulation. These discoveries collectively provide a better understanding of the anticancer candidate PARG inhibitors in terms of resistance mechanisms and anticancer strategies.

Comments:

Your study aimed to investigate the molecular mechanisms and tumor biological aspects of resistance to the PARG inhibitor PDD00017273 in human colorectal cancer (CRC) HCT116 cells. Here are the methods and results of your study:

Methods:
1. HCT116RPDD cells: You used a variant of the human CRC cell line HCT116, called HCT116RPDD, which exhibited resistance to the PARG inhibitor PDD00017273.
2. Exome sequencing: You performed exome sequencing on HCT116RPDD cells to identify specific mutations in PARG and PARP1, the two key enzymes involved in poly(ADP-ribose) (PAR) metabolism.
3. Protein analysis: You compared the levels of PARG and PARP1 proteins between HCT116RPDD and HCT116 cells using protein analysis techniques.
4. Intracellular poly(ADP-ribosyl)ation: You measured the levels of intracellular poly(ADP-ribosyl)ation, a process regulated by PARG and PARP1, in HCT116RPDD and HCT116 cells.
5. COH34: You tested whether HCT116RPDD cells exhibited cross-resistance to COH34, another PARG inhibitor.

Results:
1. PARG and PARP1 mutations: Exome sequencing revealed specific mutations in PARG (Glu352Gln) and PARP1 (Lys134Asn) in HCT116RPDD cells.
2. PARG protein levels: The levels of PARG protein were comparable between HCT116RPDD and HCT116 cells.
3. PARP1 protein levels: In HCT116RPDD cells, the levels of PARP1 protein were significantly lower than those in HCT116 cells.
4. Intracellular poly(ADP-ribosyl)ation: The levels of intracellular poly(ADP-ribosyl)ation were elevated in HCT116RPDD cells compared to HCT116 cells.
5. COH34 resistance: Interestingly, HCT116RPDD cells did not exhibit cross-resistance to COH34, indicating a specific resistance mechanism to PDD00017273.

Conclusion:
1. PARG mutations and resistance: The mutated PARG in HCT116RPDD cells acquired resistance to PDD00017273, likely due to structural modifications caused by the Glu352Gln mutation.
2. PARP downregulation: Resistance to PDD00017273 induced PARP1 downregulation, leading to lower levels of PARP1 protein in HCT116RPDD cells.
3. Elevated poly(ADP-ribosyl)ation: The increased intracellular poly(ADP-ribosyl)ation in HCT116RPDD cells suggests that resistance to PDD00017273 may promote hyperactivation of PAR metabolism.
4. COH34 sensitivity: HCT116RPDD cells did not exhibit resistance to COH34, indicating that the resistance mechanism is specific to PDD00017273.
5. Implications for anticancer strategies: These findings enhance our understanding of resistance mechanisms to PARG inhibitors like PDD00017273, providing insights for the development of effective anticancer strategies targeting PAR metabolism.

Please note that the information provided here is a summary based on the details you provided. For further details, please refer to the original study.