[Dbait: An innovative concept to inhibit DNA repair and treat cancer]

The ability of cancer cells to recognize damage and initiate DNA repair is an important mechanism for therapeutic resistance. The use of inhibitors of DNA damage repair or signaling pathways appears to provide a unique opportunity for targeting genetic differences between tumor and normal cells. In this review, we firstly describe the main DNA lesions induced by the different treatments and the pathways involved in their repair. Then we review the mechanism of action and applications of an innovative DNA repair inhibitor: Dbait (and its clinical form DT01). Dbait/DT01 consists of 32 bp deoxyribonucleotides forming an intramolecular DNA double helix that mimics DNA lesions. They act as a bait for DNA damage signaling enzymes, the polyadenyl-ribose polymerase (PARP), and the DNA-dependent kinase (DNA-PK), inducing a "false" DNA damage signal and ultimately inhibiting recruitment at the damage site of many proteins involved in double-strand break and single-strand break repair pathways. Preclinical studies have demonstrated the capacity of Dbait/DT01 to improve the efficiency of (i) chemotherapy in colorectal cancer or hepatocellular carcinoma models, (ii) radiofrequency ablative in colorectal cancer liver metastases models, and (iii) radiotherapy in xenografted mice with head & neck squamous cell carcinoma, glioblastoma and melanoma. Following this good preclinical results, we performed a first-in-human phase 1-2a study evaluating the safety and efficacy of the combination of DT01 with radiotherapy for the treatment of skin metastases of melanoma. Twenty-three patients were included. No dose-limiting toxicity was observed. An objective response was observed in 59% lesions, including 30% complete responses. This first promising clinical efficacy provides future potential interesting clinical development of Dbait/DT01 with various anticancer treatments.

[Hereditary ovarian carcinomas: clinico-biological features and treatment]

Hereditary ovarian cancers account for 10% of all cases. Two major syndromes with dominant autosomal transmission are identified. The most common one is breast-ovarian cancer syndrome due to BRCA1 and BRCA2 genes mutations, and the Lynch syndrome with mutated MMR genes is the other. Alterations in homologous recombination specifically observed in ovarian cancer with BRCA defects associated to Parp inhibition create a synthetic lethality of special interest. Numerous studies are in progress to explore this promising new approach. Furthermore, it seems that carcinogenesis of these two syndromes are different, suggesting alternative therapeutic options in the near future in order to improve prognosis of ovarian carcinomas.