Recreating the complex microenvironmental signalling network which is vital to CLL cell proliferation and survival in tissue niches in vivo is challenging to the extent that ex‐vivo stimulation of the BCR, one of the most important receptors for these cells in vivo, cannot induce CLL cell proliferation in culture (Schleiss et al., 2019). This evidence concerns the gene BCR and B-cell chronic lymphocytic leukemia.