The CRISPR-Cas9 technology has revolutionized the scope and pace of biomedical research, enabling the targeting of specific genomic sequences for a wide spectrum of applications. Here we describe assays to functionally interrogate mutations identified in cancer cells utilizing both CRISPR-Cas9 nuclease and base editors. We provide guidelines to interrogate known cancer driver mutations or functionally screen for novel vulnerability mutations with these systems in characterized human cancer cell lines. The proposed platform should be transferable to primary cancer cells, opening up a path for precision oncology on a functional level.