Direct cell-cell contact, for example adhesion of RHAMM/CD44 positive cancer cells onto mesothelial hyaluronic acid (HA) and interactions between mesothelial cell surface fibronectin and cancer cell-derived α5β1 integrins, adhesion of IL-1β expressing cancer cells onto mesothelial β1 integrins, formation of spontaneous cancer spheroids, and cancer cells squeezing past mesothelial gap junctions to access the underlying basement membrane (BM) and extracellular matrix (ECM). The gene discussed is CD44; the disease is cancer.