CTSD and cancer: Under electron microscopy, PaCSs showed characteristic barrel-like particles, about 13 nm thick and 15 to 40 nm long, with an inner punctate substructure, and selective immunogold reactivity for proteasome (Figure 1B and C), polyubiquitinated proteins, NOD1, VacA, CagA, urease and OMPs, but not for p62 protein or the lysosomal marker cathepsin D. Using the same procedures, PaCSs were also identified in two of five gastric gland-forming (cohesive, so-called ‘intestinal’) cancers, with all the structural and cytochemical patterns shown in non-tumour gastric epithelium (Figure 1D–M).