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Updated: Apr 25, 2026
Screening for Thermotoga maritima Membrane-Bound Pyrophosphatase Inhibitors
Published on: November 23, 2019
Identification of a putative Tdp1 inhibitor (CD00509) by in vitro and cell-based assays
Richard A Dean1, Hok Khim Fam2, Jianghong An3
1Centre for Drug Research and Development, Vancouver, BC, Canada.
Abstract:
Mutations of DNA repair pathways contribute to tumorigenesis and provide a therapeutic target for synthetic lethal interactions in tumor cells. Given that tyrosyl-DNA phosphodiesterase 1 (Tdp1) repairs stalled topoisomerase-I DNA complexes, we hypothesized that inhibition of Tdp1 has synthetic lethal effects in some cancers. To test this, we screened tumor arrays for Tdp1 expression and observed that Tdp1 is expressed in many tumors, including more than 90% of human breast tumors. Subsequent chemical screening identified putative Tdp1 inhibitors. Treatment of control human mammary epithelial cells and the breast cancer cell line MCF-7 with compound CD00509 preferentially sensitized MCF-7 cells to camptothecin and decreased cell proliferation 25% more than camptothecin treatment alone. This suggests that CD00509 specifically targeted Tdp1 in vitro, and CD00509 increased the sensitivity of wild-type murine embryonic fibroblasts (MEFs) to camptothecin to a degree comparable to that of Tdp1(-/-) MEFs. In addition, consistent with poly ADP-ribose polymerase-1 (PARP-1) collaborating with Tdp1 in DNA repair, combined Tdp1 and PARP-1 inhibition was more detrimental to MCF-7 cells than either treatment alone, whereas the combination was not additively harmful to control mammary cells. We conclude that targeting Tdp1 in anticancer therapy preferentially enhances the sensitivity of some breast cancer cells to camptothecin and may be an effective adjuvant for breast cancer therapy.
Insights
Targeting tyrosyl-DNA phosphodiesterase 1 (Tdp1) shows synthetic lethality in cancer. Inhibiting Tdp1 enhances breast cancer cell sensitivity to camptothecin, suggesting Tdp1 as a therapeutic target.
Area of Science:
- Cancer Biology
- DNA Repair Mechanisms
- Pharmacology
Background:
- Mutations in DNA repair pathways are implicated in cancer development.
- Tyrosyl-DNA phosphodiesterase 1 (Tdp1) repairs stalled topoisomerase-I DNA complexes, presenting a potential therapeutic target.
- Tdp1 is highly expressed in many human breast tumors, exceeding 90%.
Purpose of the Study:
- To investigate the synthetic lethal potential of inhibiting Tdp1 in cancer therapy.
- To identify and evaluate compounds that inhibit Tdp1 activity.
- To assess the combined therapeutic effect of Tdp1 and poly ADP-ribose polymerase-1 (PARP-1) inhibition.
Main Methods:
- Screening of tumor arrays for Tdp1 expression.
- Chemical screening to identify Tdp1 inhibitors.
- In vitro and cellular assays using breast cancer cell lines (MCF-7) and murine embryonic fibroblasts (MEFs).
- Assessment of drug sensitivity to camptothecin with and without Tdp1 inhibition.
- Evaluation of combined Tdp1 and PARP-1 inhibition.
Main Results:
- Compound CD00509 preferentially sensitized MCF-7 breast cancer cells to camptothecin.
- CD00509 demonstrated specific Tdp1 targeting in vitro and in cellular models.
- Tdp1 inhibition increased sensitivity to camptothecin in wild-type MEFs, comparable to Tdp1-deficient MEFs.
- Combined inhibition of Tdp1 and PARP-1 showed synergistic cytotoxicity in MCF-7 cells but not in control cells.
Conclusions:
- Inhibition of Tdp1 selectively enhances the sensitivity of certain breast cancer cells to camptothecin.
- Targeting Tdp1 represents a promising strategy for adjuvant breast cancer therapy.
- The combination of Tdp1 and PARP-1 inhibition offers a potential synergistic approach for cancer treatment.
