On the other hand, we found that the chymotryptic serine proteinase Cma1, the endogenous opioid polypeptide hormone Penk, Guanine nucleotide-binding protein Gnai1 and the chemokine receptor Ccr3 were among the most down-regulated genes in SSMs after the influence of a local tumor mass (Figure 4B). Here, PENK is linked to neoplasm.