LAMB2 and urinary bladder carcinoma: Laminin is an interesting candidate: a recent feeder‐free protocol employs laminin‐rich conditioned medium from 804G rat bladder carcinoma cells to deposit a substrate for epithelial cell expansion (Mou et al, 2016) and the common organoid ECM from murine sarcoma‐derived Matrigel contains predominantly laminin, collagen IV, and nidogen‐1, but it also includes more than 1,000 other proteins with variability between batches (Hughes et al, 2010).