No abstract

Purpose Radiation therapy continues to be an important therapeutic strategy for providing definitive local/regional control of human cancer. However, oncogenes that harbor driver mutations and/or amplifications can compromise therapeutic efficacy. Thus, there is a need for novel approaches that enhance the DNA damage produced by ionizing radiation. Experimental Design A forward chemical genetic approach coupled with cell-based phenotypic screening of several tumor cell lines was used to identify a novel chemical entity (NCE) that functioned as a radiation sensitizer. Proteomics, comet assays, confocal microscopy and immunoblotting were used to identify the biological target. Results The screening process identified a 5-((N-benzyl-1H-indol-3-yl)methylene)pyrimidine-2,4,6(1H,3H,5H)trione as a NCE that radiosensitized cancer cells expressing amplified and/or mutated RAS, ErbB, PIK3CA, and/or BRAF oncogenes. Affinity-based solid phase resin capture followed by LC/MS/MS analysis identified the chaperone nucleophosmin as the NCE target. SiRNA suppression of nucleophosmin abrogated radiosensitization by the NCE. Confocal microscopy demonstrated that the NCE inhibited nucleophosmin shuttling to radiation-induced DNA damage repair foci and analysis of comet assays indicated a diminished rate of DNA double strand break repair. Conclusion These data support the hypothesis that inhibition of DNA repair due to inhibition of nucleophosmin shuttling increases the efficacy of DNA damaging therapeutic strategies.

A series of (Z)-5-((N-benzyl-1H-indol-3-yl)methylene)imidazolidine-2,4-dione (9a–9m) and 5-((N-benzyl-1H-indol-3-yl)methylene)pyrimidine-2,4,6(1H,3H,5H)-trione (10a–10i) derivatives that incorporate a variety of aromatic substituents in both the indole and N-benzyl moieties have been synthesized. These analogs were evaluated for their radiosensitization activity against the HT-29 cell line. Three analogs, 10a, 10b, and 10c were identified as the most potent radiosensitizing agents.