ROR1 and B-cell chronic lymphocytic leukemia: In another preclinical study, the combination of targeting receptor tyrosine kinase-like orphan receptor 1 (ROR1)-dependent signaling, which is associated with CSC maintenance and self-renewal, via cirmtuzumab and ibrutinib, which blocks B-cell receptor signaling, was more effective than single-agent treatments in reducing the number of CLL cells in the spleens of immunodeficient mice [253].