An understanding of the molecular nature of BMs first came in the 1970s with biochemical studies of the Engelbreth–Holm–Swarm sarcoma BM extracts also known as Matrigel (83, 118); purification of laminins (23, 147), HSPG2/perlecan (63), and entactin/nidogen 1 (23, 37, 146); and molecular cloning of the corresponding genes. The gene discussed is HSPG2; the disease is sarcoma.