Dipeptidyl peptidase 9 (DPP9) was recently identified as fusion gene in ovarian high-grade serous
carcinoma (HGSC). The aim of this study was to analyze the expression and clinical relevance of DPP8 and DPP9 in ovarian
carcinoma, with focus on HGSC.
mRNA expression by qRT-PCR of DPP8 and DPP9 was analyzed in 232
carcinomas, including 114 effusions and 118 surgical specimens (89 ovarian, 29 solid
metastases). DPP8 and DPP9
protein expression was analyzed in 92 effusions. DPP8 and DPP9
mRNA was overexpressed in effusions compared to solid lesions in analysis of all histotypes (p < 0.001 both), as well as in analysis limited to HGSC (p < 0.001 for DPP9, p = 0.002 for DPP8). DPP9
mRNA was additionally overexpressed in HGSC compared to other histotypes (p = 0.021). DPP8 and DPP9
protein was expressed in
carcinoma cells in 31/92 (37%) and 81/92 (88%) effusions, respectively. DPP8
protein expression in HGSC effusions was significantly related to better (complete) chemoresponse at diagnosis (p = 0.005). DPP8 and DPP9
mRNA and
protein expression was unrelated to survival in analysis of the entire effusion cohort. However, higher DPP9
mRNA levels were significantly related to longer overall survival in pre-
chemotherapy effusions (p = 0.049). In conclusion, DPP8 and DPP9
mRNA is frequently expressed in ovarian
carcinoma, whereas DPP9 is more frequently expressed at the
protein level. DPP8 and DPP9 may be related to less aggressive disease in advanced-stage HGSC.