GSE162508
The origin and contribution of the tumor stroma in colorectal carcinogenesis
Background and aims  Cancer-associated fibroblasts (CAFs) play a critical role in colorectal cancer (CRC) progression. However, the precise cellular origins of the tumor stroma remain unknown, making it challenging to therapeutically target the tumor mesenchyme. Here, we aimed to identify key cellular contributors to and components of the CRC mesenchyme associated with poor prognosis.  Methods  We used a mouse model of inflammation-associated CRC in 5 different genetic fate-mapping transgenic mouse lines to characterize the origins of the CRC stroma. To identify a potential therapeutic target expressed by the CRC stroma, RNA-sequencing of fluorescence-activated cell sorting (FACS)-purified CRC stromal cells was performed. CRC patient RNA-sequencing data (n=621) and tissue microarray (n=101) were used to examine the prognostic significance of marker expression.  Results   We found that approximately half of the CRC CAFs marked by a-smooth muscle actin (aSMA) in a mouse model of CRC emerge through proliferation. Lineage tracing experiments revealed that intestinal leptin receptor (Lepr)-lineage stromal cells expanded and contributed to 75% of the aSMA+ proliferating CAFs. Notably, no aSMA+ CAFs arose from Krt19-lineage epithelial cells or bone marrow-derived cells. Moreover, RNA-sequencing of FACS-purified CRC mesenchymal cells identified MCAM as a CRC stroma-specific marker, which is expressed by Lepr-lineage cells. Analysis of human CRC samples showed that high MCAM expression driven, in part, by TGF-ß was independently prognostic of poor overall survival.   Conclusion  Our data identify intestinal Lepr-lineage cells as a major source of the tumor stroma in CRC and suggest that targeting MCAM+ cells may serve as an attractive therapeutic approach to restrain CRC progression. Overall design: Four 8-week-old adult mice (2 males and 2 females), four postnatal day 14 mice (2 males and 2 females), and four AOM/DSS-treated mice (2 males and 2 females) were used to isolate colonic cells. Stromal cells were selected by FACS-sorting of CD45- immune cells, EPCAM- epithelial cells, CD31- endothelial cells on FACSAria Fusion (BD Bioscience). Differential gene expression analyses were performed between prenatal vs normal and AOM/DSS tumor vs normal.