WNT and inflammatory signaling distinguish human Fallopian tube epithelial cell populations

A substantial fraction of ovarian/extra-uterine high-grade serous carcinomas (HGSCs) likely originate in the distal region of the Fallopian tubes epithelium (TE) before implanting/metastasizing to the ovary. Unfortunately, molecular and cellular mechanisms rendering preferential cancer susceptibility of the human distal TE remain insufficiently elucidated, largely due to limited primary human TE gene expression data. Here we report an in depth bioinformatic characterization of 34 primary TE cell mRNA-seq samples. These samples were prepared from the proximal and distal TE regions of 12 normal Fallopian tubes. TE cells were segregated based on their aldehyde dehydrogenase (ALDH) activity. As compared to the proximal TE, cells from the distal region form organoids with higher frequency and larger size during serial organoid formation assays. Consistent with enrichment for organoid-forming stem/progenitor cells, ALDH+ cells have greater WNT signaling activity. Comparative evaluation of proximal and distal TE cell populations shows heightened inflammatory signaling in distal differentiated (ALDH-) TE. Furthermore, comparisons of proximal and distal TE cell populations finds that the distal TE express gene sets characteristic of four HGSC molecular sub-types, and that distal ALDH+ cell populations exhibit greater enrichment than their ALDH-counterparts. Taken together, our study shows that increased organoid forming capacity, WNT and inflammatory signaling, and HGSC signatures underlie the differences between distal and proximal regions of the human TE. These findings provide the basis for further mechanistic studies of distal TE susceptibility to the malignant transformation.