In the field of cancer biology, numerous genes or proteins form extremely complex regulatory networks, which determine cancer cell fate and cancer cell survival. Among all regulatory networks operating in cancer cells, the DNA repair network is of particular importance. Dysfunction of DNA repair network leads to genomic instability, a hallmark of cancer cells. However, it remains largely unknown how loss of major tumor suppressors such as PTEN and BRCA1 influences the DNA repair network and what are the key links in the DNA repair network altered by loss of tumor suppressors in cancer cells.

To address these questions, we employ the concept of maximum flow in a flow network to identify the key links in the DNA repair network in BRCA1- and PTEN- deficient cells. Through this analysis, we determine the key links in such DNA repair networks.