Inhibition of ribonucleotide reductase subunit M2 enhances the radiosensitivity of metastatic pancreatic neuroendocrine tumor

Cancer Lett. 2024 Aug 1:596:216993. doi: 10.1016/j.canlet.2024.216993. Epub 2024 May 25.

Abstract

Ribonucleotide Reductase (RNR) is a rate-limiting enzyme in the production of deoxyribonucleoside triphosphates (dNTPs), which are essential substrates for DNA repair after radiation damage. We explored the radiosensitization property of RNR and investigated a selective RRM2 inhibitor, 3-AP, as a radiosensitizer in the treatment of metastatic pNETs. We investigated the role of RNR subunit, RRM2, in pancreatic neuroendocrine (pNET) cells and responses to radiation in vitro. We also evaluated the selective RRM2 subunit inhibitor, 3-AP, as a radiosensitizer to treat pNET metastases in vivo. Knockdown of RNR subunits demonstrated that RRM1 and RRM2 subunits, but not p53R3, play significant roles in cell proliferation. RRM2 inhibition activated DDR pathways through phosphorylation of ATM and DNA-PK protein kinases but not ATR. RRM2 inhibition also induced Chk1 and Chk2 phosphorylation, resulting in G1/S phase cell cycle arrest. RRM2 inhibition sensitized pNET cells to radiotherapy and induced apoptosis in vitro. In vivo, we utilized pNET subcutaneous and lung metastasis models to examine the rationale for RNR-targeted therapy and 3-AP as a radiosensitizer in treating pNETs. Combination treatment significantly increased apoptosis of BON (human pNET) xenografts and significantly reduced the burden of lung metastases. Together, our results demonstrate that selective RRM2 inhibition induced radiosensitivity of metastatic pNETs both in vitro and in vivo. Therefore, treatment with the selective RRM2 inhibitor, 3-AP, is a promising radiosensitizer in the therapeutic armamentarium for metastatic pNETs.

Keywords: Metastases; Pancreatic neuroendocrine tumor; Radiosensitization; Radiotherapy; Ribonucleotide reductase inhibitor.

MeSH terms

  • Animals
  • Apoptosis* / drug effects
  • Ataxia Telangiectasia Mutated Proteins / antagonists & inhibitors
  • Ataxia Telangiectasia Mutated Proteins / genetics
  • Ataxia Telangiectasia Mutated Proteins / metabolism
  • Cell Line, Tumor
  • Cell Proliferation* / drug effects
  • Checkpoint Kinase 1 / antagonists & inhibitors
  • Checkpoint Kinase 1 / genetics
  • Checkpoint Kinase 1 / metabolism
  • Checkpoint Kinase 2 / antagonists & inhibitors
  • Checkpoint Kinase 2 / genetics
  • Checkpoint Kinase 2 / metabolism
  • DNA-Activated Protein Kinase
  • Female
  • Humans
  • Lung Neoplasms / genetics
  • Lung Neoplasms / pathology
  • Lung Neoplasms / radiotherapy
  • Lung Neoplasms / secondary
  • Mice
  • Mice, Nude*
  • Neuroendocrine Tumors / drug therapy
  • Neuroendocrine Tumors / enzymology
  • Neuroendocrine Tumors / genetics
  • Neuroendocrine Tumors / metabolism
  • Neuroendocrine Tumors / pathology
  • Neuroendocrine Tumors / radiotherapy
  • Pancreatic Neoplasms* / drug therapy
  • Pancreatic Neoplasms* / enzymology
  • Pancreatic Neoplasms* / genetics
  • Pancreatic Neoplasms* / pathology
  • Pancreatic Neoplasms* / radiotherapy
  • Phosphorylation
  • RNA Interference
  • Radiation Tolerance* / drug effects
  • Radiation-Sensitizing Agents* / pharmacology
  • Ribonucleoside Diphosphate Reductase* / antagonists & inhibitors
  • Ribonucleoside Diphosphate Reductase* / genetics
  • Ribonucleoside Diphosphate Reductase* / metabolism
  • Signal Transduction / drug effects
  • Tumor Suppressor Proteins / genetics
  • Tumor Suppressor Proteins / metabolism
  • Xenograft Model Antitumor Assays*

Substances

  • Ribonucleoside Diphosphate Reductase
  • ribonucleotide reductase M2
  • Radiation-Sensitizing Agents
  • RRM1 protein, human
  • Ataxia Telangiectasia Mutated Proteins
  • Tumor Suppressor Proteins
  • Checkpoint Kinase 1
  • ATM protein, human
  • CHEK1 protein, human
  • PRKDC protein, human
  • Checkpoint Kinase 2
  • DNA-Activated Protein Kinase