The current disclosure describes materials and methods for identifying subjects that would benefit from treatment with a DNA topoisomerase 1 inhibitor, based on the levels of cullin 4B gene, RNA and protein levels in the subject. The disclosure identifies CUL4B as a predictive biomarker for cancer diagnosis and the subsequent treatment with directed therapeutic agents. The current disclosure also identifies novel therapeutic agents that modulate the level of CUL4B expression, and sensitize a subject to treatment with a second therapeutic agent.
