Study With Trabectedin in BRCA1 and BRCA2 Mutation Carrier and BRCAness Phenotype Ovarian Cancer

The main contribution to hereditary ovarian cancer comes from breast cancer (BRCA) genes mutations, which are responsible of 90% of hereditary ovarian cancer. The two susceptibility genes associated with epithelial-type OC are BRCA1 and BRCA2. The BRCA proteins play an important role in the DNA repair mechanisms and are also involved in the control of the cell cycle checkpoints, in protein ubiquitinization and chromatin remodelling. Mutations in the BRCA genes have been extensively described in families affected by breast and/or OC; mutated BRCA1 has been found in up to 75% of families with hereditary OC - Recent data suggest that dysfunction of BRCA1andBRCA2, so-called BRCAness, maybe more prevalent than originally assumed. Both genetic and epigenetic mechanisms can create the BRCAness phenotype in at least a third of all epithelial ovarian cancers. The definition of BRCAness ovarian cancer is: high-grade serous cancers, high initial sensitivity to platinum drugs and retention of platinum-sensitivity through multiple relapses, longer history of disease, longer survival, longer TFIs between relapses. Yondelis® (trabectedin) is proposed to block the transcriptional activation of a subset of inducible genes without affecting their constitutive expression. Trabectedin binds to the minor groove of DNA, bending the helix to the major groove. This binding to DNA triggers a cascade of events affecting several transcription factors, DNA binding proteins, and DNA repair pathways, resulting in perturbation of the cell cycle. Cell cycle studies of the action of trabectedin on tumor cells in vitro reveal that it decreases the rate of progression of the cells through S phase towards G2 and causes a prolonged blockade in G2/M at biologically relevant concentrations (20-80 nM). These cell cycle blocks are p53-independent and lead to a strong apoptopic response. Cells in G1 are more sensitive to the cytotoxic effects of trabectedin. These effects appear to be related to the unique 3-subunit structure, where two of the subunits or rings are involved in binding to the minor groove of DNA in guanine-cytosine rich sequences and alkylation N2 of guanine forming adducts that distorted the DNA helix structure and they are recognized by the TC-NER mechanism. DNA repair proficiency is a major determinant for the cytotoxicity of trabectedin: human cell lines deficient for genes essential for TC-NER activity as XPA, XPB, XPD, XPF, XPG, ERCC1, CSA and CSB are resistant to trabectedin, and this resistance is reverted by complementation of the cells with the corresponding gene. Trabectedin induces double strand breaks and that the BRCA1-/- human cell line HCC1937 and BRCA2Δ22/Δ22 mice cells are more sensitive to trabectedin and this hypersensitivity is reverted by complementation by the BRCA1 or BRCA2 gene. Based in these observations it was hypothesized that the NER machinery trapped in the DNA lesion induced by trabectedin was resolved by the cells producing double strand breaks that were repaired by the HRR machinery, and synergistic action of TC-NER and HRR machinery would be necessary for maximal trabectedin cytotoxicity.