PSEN1 and cancer: To identify specific genes that may play important roles in the differential expression of the nine genes, we conducted bioinformatics analyses using Ingenuity Pathway Analysis software and identified PS1 as a common upstream regulator for three of these nine genes: ATP1B1, ARF4, and ATP5C1. Using freshly isolated human normal ovarian fibroblasts (NOFs) and cancer-associated fibroblasts (CAFs) derived from HGSC, we confirmed that PS1 expression was indeed higher in CAFs when compared with NOFs (Figure 1A).