Cancer associated fibroblasts in colorectal cancer: a heterogeneous population leading to cancer migration and invasiveness

Peri-tumoral activated fibroblasts are key players in tumorigenesis and cancer progression, and they are often referred as Cancer Associated Fibroblasts (CAFs). CAFs have a central role in the synthesis and remodeling of the desmoplastic stroma. Previous studies have shown that severe desmoplasia is correlated with poor prognosis in several tumors such as lung, pancreas, breast, and colorectal. In patients who underwent curative surgery for colon cancer, poor prognostic data (overall survival and disease free-survival) have been reported when the stromal component was prevalent than carcinoma cellularity. The definition of CAFs is still a debated issue because even if several markers have been suggested in the past to define CAFs, it is now being appreciated that these markers do not mark all CAFs and that their different expression could reveal a heterogeneous population of fibroblast. We develop a robust protocol for isolation of CAFs and their paired NFs by eco-guided FNAB sampling from a fresh specimen of colon and rectum resected for carcinoma. The present study revealed that Podoplanin was more differently expressed in CAF vs NFs, while similar levels of α-smooth muscle actin (α-SMA) were found in the two populations of fibroblasts. Moreover, HIC on paraffin sections was undertaken to assess if CAF markers (α-SMA and Podoplanin) expressed at the sample site previously marked with Indian Ink can be different. We found Podoplanin positive fibroblast in a linear disposition close to the tumoral cells that could be compared with the interstitial lining cells described as precursors of fibrogenic myofibroblast responders in peritumoral sclerosis revealed in the recent discovery of a new interstitium. Finally, we demonstrate that paracrine factors lead the invasion of colorectal tumor induced by CAF. When the wound healing assay was performed in order to evaluate the migration of colorectal tumoral cells (DLD1) earlier scratch closure was observed in cells supplemented by the CAF-conditioned medium (CAFc) compared to those treated with the NF-conditioned medium (NFc).