2. Academic Validation
  3. POLQ and DNA-PK inhibition in muscle-invasive bladder cancer : Enhancing radiosensitivity with novel DNA damage response inhibitors to improve radiotherapy outcomes

POLQ and DNA-PK inhibition in muscle-invasive bladder cancer : Enhancing radiosensitivity with novel DNA damage response inhibitors to improve radiotherapy outcomes

  • Pathologie (Heidelb). 2025 Nov 26. doi: 10.1007/s00292-025-01507-w.
Julia Pannhausen 1 2,  Ahmed A Chughtai 2 3,  Michael K Melzer 4 5,  Yanchun Ma 4 5,  Julia Wirtz 1 2,  Alexander Kleger 5 6 7,  Matthias Saar 2 8,  Michael J Eble 2 3,  Danny D Jonigk 1 2 9,  Michael Rose 10 11 12,  Nadine T Gaisa 13 14 15
Affiliations

Affiliations

  • 1 Institute of Pathology, Uniklinik RWTH Aachen, Pauwelsstraße 30, 52074, Aachen, Germany.
  • 2 Centre for Integrated Oncology Aachen Bonn Cologne Duesseldorf (CIO ABCD), 52074, Aachen, Germany.
  • 3 Department of Radiation Oncology, Uniklinik RWTH Aachen, 52074, Aachen, Germany.
  • 4 Department of Urology, Ulm University Hospital, 89081, Ulm, Germany.
  • 5 Institute for Molecular Oncology and Stem Cell Biology, Ulm University Hospital, 89081, Ulm, Germany.
  • 6 Core Facility Organoids, Ulm University Hospital, 89081, Ulm, Germany.
  • 7 Section for Interdisciplinary Pancreatology, Clinic for Internal Medicine I, Ulm University Hospital, 89081, Ulm, Germany.
  • 8 Department of Urology, Uniklinik RWTH Aachen, 52074, Aachen, Germany.
  • 9 German Center for Lung Research, DZL, BREATH, 30625, Hanover, Germany.
  • 10 Institute of Pathology, Uniklinik RWTH Aachen, Pauwelsstraße 30, 52074, Aachen, Germany. [email protected].
  • 11 Centre for Integrated Oncology Aachen Bonn Cologne Duesseldorf (CIO ABCD), 52074, Aachen, Germany. [email protected].
  • 12 Institute of Pathology, Ulm University Hospital, Albert-Einstein-Allee 23, 89081, Ulm, Germany. [email protected].
  • 13 Institute of Pathology, Uniklinik RWTH Aachen, Pauwelsstraße 30, 52074, Aachen, Germany. [email protected].
  • 14 Centre for Integrated Oncology Aachen Bonn Cologne Duesseldorf (CIO ABCD), 52074, Aachen, Germany. [email protected].
  • 15 Institute of Pathology, Ulm University Hospital, Albert-Einstein-Allee 23, 89081, Ulm, Germany. [email protected].
PMID: 41295990 DOI: 10.1007/s00292-025-01507-w
Abstract

Background: Muscle-invasive bladder Cancer (MIBC) includes histological subtypes such as urothelial carcinoma (UC) and the rarer, prognostically unfavorable, squamous cell carcinoma (SCC). Standard treatment is radical cystectomy, while alternatives like chemotherapy or radiotherapy are particularly limited in SCC. Radiosensitizers, such as DNA-dependent protein kinase (DNA-PK) and DNA Polymerase theta (POLQ) inhibitors, could selectively enhance radiotherapy effects in tumor cells and represent promising approaches for clinical translation.

Objective: This study analyzed the radiosensitizing effects of DNA-PK and POLQ inhibition ex vivo in patient-derived MIBC cell lines of UC and SCC subtypes.

Materials and methods: The DNA-PK Inhibitor AZD7648 (DNA-PKi) and the POLQ inhibitor ART558 (POLQi) were tested ex vivo in patient-derived SCC (p-SCC; n = 3) and UC (p-UC; n = 3) cell cultures. Effects were assessed in combination with ionizing radiation (IR) using XTT cell viability assays (IC50), clonogenic survival assays, γH2AX immunofluorescence, and comet assays.

Results: DNA-PKi strongly radiosensitized MIBC cultures ex vivo, reducing IC50-XTT values by 74-99% and survival rates by 34-64%. Under POLQi +2 Gy, IC50 decreased by 7-13%, whereas under POLQi +8 Gy it increased by 11-24%, with only ~5% reduction in survival. DNA-PKi markedly delayed DNA repair (comet tail moments 38-40%, γH2AX foci increased 11.9-13.1-fold), while POLQi showed minimal effects (comet tail moments 22-33%, γH2AX foci increased 5.4-6.0-fold).

Conclusion: DNA-PKi radiosensitized MIBC cells more effectively than POLQi, particularly SCC. DNA damage response (DDR) inhibitors thus have therapeutic potential in MIBC, depending on the target protein and tumor subtype.

Keywords

ART558; AZD7648; Radiosensitization; Squamous bladder cancer; Urothelial carcinoma.

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