Abstract A20: Depletion of replication factor MCM7 is synthetically lethal to oncogenic KRAS expression

Colorectal cancer (CRC) is a substantial cause of death in the western world. With KRAS being one of the most frequently altered oncogenes in CRC, it is an obvious target for cancer therapy. But despite enormous efforts over the past three decades to target mutated RAS, not a single drug has made it to the clinic.In order to find vulnerabilities of KRAS mutant cells, we performed a shRNA-based screen. We used CaCo2 cells (wild type for KRAS/BRAF/PIK3CA) with doxycycline (DOX) inducible expression of the oncogenic KRASG12V as a model system. The custom-designed shRNA library comprised 121 selected genes encoding signaling proteins and transcription factors, which we have previously identified to be strongly up- or downregulated after treatment with MEK inhibitors.We found that CaCo2 cells expressing KRASG12V are highly sensitive to the depletion of the DNA replication licensing factor Minichromosome Maintenance Complex Component 7 (MCM7), whereas wild-type CaCo2 cells are resistant to MCM7 depletion. The screening result was verified with 3 independent shRNAs under anchorage dependent and independent conditions. Similar results were obtained with NRASG12D and in DLD1 (KRASwt/KRASG13D) and DLD1 (KRASwt/-) cells.The proposed molecular mechanism is RAS-induced genotoxic stress that cannot be resolved after MCM7 reduction. MCM7-containing complexes prime DNA for replication by binding to replication origins. However, only a few of the licensed origins are later used for DNA replic...
Source: Molecular Cancer Therapeutics - Category: Cancer & Oncology Authors: Tags: Finding Synthetic Lethal Interactions through Functional Genomics: Poster Presentations - Proffered Abstracts Source Type: research