PTN and cancer: Furthermore, one research has shown that increased expression of SDC2 in CAFs (Cancer-Associated Fibroblasts) promotes tumor growth, finding the role of high SDC2 expression in CAFs and its correlation with aggressive cancer phenotypes and poor patient survival [69], and in our study, we found PLOD2 + SAA1 + tumor cells communicated with SDC2 + CAFs through PTN-SDC2 and MDK-SDC2 pairs, which may play an important role in the development and progression of tumors.