Disclosed are methods and compositions useful in identifying an E3 ubiquitin ligase inhibitor and modulating cell growth, comprising contacting a cell with an effective amount of an inhibitor of an E3 ubiquitin ligase, and contacting the cell with an effective amount of a topoisomerase inhibitor, wherein the treatment with the E3 ubiquitin ligase inhibitor and topoisomerase inhibitor modulates cell growth in comparison to a cell treated with the topoisomerase inhibitor alone. The present invention further provides methods for identifying and making an E3 ubiquitin ligase inhibitor.