ESTRO 2024 - Abstract Book

S5430

Radiobiology - Tumour biology

ESTRO 2024

The aim of this project is to investigate underlying mechanisms and to validate the radiosensitization in different human models and in vivo .

Material/Methods:

Murine and human PDAC cells, as well as patient-derived organoids (PDOs), were treated with different concentrations of Rabusertib or Defactinib 24 h after seeding and irradiated (0 Gy, 2 Gy, 4 Gy, 6 Gy, 8 Gy; Gulmay RS225A) after an incubation time of 24 h.

A colony formation assay (CFA) with human cell lines and a 3D Cell Viability Assay with PDOs were performed to determine the radioresponse after combination treatment of kinase inhibitors and irradiation.

Flow cytometry was used to analyze DNA damage (yH2AX), cell cycle distribution (propidium iodide), reactive oxygen species (ROS, DCFDA), and apoptosis (Caspase 3/7) at different time points (60 min, 8 h, 24 h, 48 h) after irradiation.

For in vivo validation, a syngeneic subcutaneous tumor mouse model combining intraperitoneal injection of Rabusertib with image-guided irradiation (10 Gy) was established.

Results:

The radiosensitizing effect of Rabusertib and Defactinib was confirmed in human cell lines and PDOs. The combination of kinase inhibition and irradiation showed a concentration-dependent increase in the mean fluorescence of yH2AX. In cells treated with kinase inhibitors a significant increase in the radiosensitive G2/M phase at the time of irradiation was observed. Depending on the irradiation dose as well as inhibitor concentration, levels of ROS and apoptosis were increased.

In the syngeneic mouse model, combination therapy of Rabusertib and irradiation led to improved tumor control without the occurrence of toxicities compared to control cohorts (vehicle, Rabusertib, or irradiation).

Conclusion:

The present work identified underlying radiobiological mechanisms of radiosensitizing effects by kinase inhibition. In particular, DNA damage, ROS, apoptosis, and G2/M arrest seem significantly involved. The radiosensitization was validated in human PDAC cell lines, PDOs, and a syngeneic tumor mouse model.

The long-term goal is a translational approach to overcome radioresistance by kinase inhibition as an innovative therapeutic option for patients with PDAC.

Keywords: Pancreatic cancer, Radiosensitization, Kinase

References: