Dipeptidyl Peptidases as Survival Factors in Ewing Sarcoma Family of Tumors

Abstract

Ewing sarcoma family of tumors (ESFT) is a group of aggressive pediatric malignancies driven by the EWS-FLI1 fusion protein, an aberrant transcription factor up-regulating specific target genes, such as neuropeptide Y (NPY) and its Y1 and Y5 receptors (Y5Rs). Previously, we have shown that both exogenous NPY and endogenous NPY stimulate ESFT cell death via its Y1 and Y5Rs. Here, we demonstrate that this effect is prevented by dipeptidyl peptidases (DPPs), which cleave NPY to its shorter form, NPY 3-36 , not active at Y1Rs. We have shown that NPYinduced cell death can be abolished by overexpression of DPPs and enhanced by their down-regulation. Both NPY treatment and DPP blockade activated the same cell death pathway mediated by poly(ADP-ribose) polymerase (PARP-1) and apoptosisinducing factor (AIF). Moreover, the decrease in cell survival induced by DPP inhibition was blocked by Y1 and Y5R antagonists, confirming its dependence on endogenous NPY. Interestingly, similar levels of NPY-driven cell death were achieved by blocking membrane DPPIV and cytosolic DPP8 and DPP9. Thus, this is the first evidence of these intracellular DPPs cleaving releasable peptides, such as NPY, in live cells. In contrast, another membrane DPP, fibroblast activation protein (FAP), did not affect NPY actions. In conclusion, DPPs act as survival factors for ESFT cells and protect them from cell death induced by endogenous NPY. This is the first demonstration that intracellular DPPs are involved in regulation of ESFT growth and may become potential therapeutic targets for these tumors.

Expression profiling of dipeptidyl peptidase 8 and 9 in breast and ovarian carcinoma cell lines

“…However, information on the expression of DP8 and DP9 in pathophysiological settings and potential roles in cancer is limited. In contrast to the recently identified NPY-dependent survival role suggested for DP8/DP9 in Ewings sarcoma (16), the overexpression of DP8 and DP9 in HEK293T and HepG2 cells has been shown to increase migration, proliferation and enhance staurosporine-streptomyces induced apoptosis (17,36) suggesting the effects of DP8/DP9 in cancer, like DP4 and FAP, may be tumor specific. In chronic lymphocytic leukemia (CLL) a significant increase in DP8 mRNA has been observed (37) while upregulation of DP9 mRNA has been observed in testicular cancer (38).…”

“…As we have found in the present study, the expression of DP4 in relation to DP9 is likely to play an important role in breast and ovarian cancer pathogenesis. Lu et al investigated the roles of DPs in ESFT, individual siRNA knockdown of DP4, DP8, DP9 and FAP was performed in human ESFT cell lines, however no increase in DP9 mRNA levels was detected following siRNA decrease in DP4 mRNA (16). Unfortunately, the Lu et al study did not measure protein level expression.…”

“…DP4 proteolysis inactivates SDF-1α/β, disrupting the SDF-1/ CXCR4 interaction affecting downstream signaling and the likely SDF-1 mediated cell migration and metastasis (13)(14)(15). DP4, DP8 and DP9 have recently been shown to act as survival factors for Ewing's sarcoma family of tumors (ESFT) through the inactivation of NPY-driven cell death within ESFT cells (16). There also appears to be non-enzymatic functions of DP4, FAP, DP8 and DP9 that are important to their roles affecting migration, proliferation and apoptosis of tumor cells (17,18).…”

Contribution of upregulated dipeptidyl peptidase 9 (DPP9) in promoting tumoregenicity, metastasis and the prediction of poor prognosis in non‐small cell lung cancer (NSCLC)

“…For instance, DPP9 expression is significantly increased in testicular cancer,11 and DPP9 enzymatic activity is associated with a malignant behavior in human astrocytic tumors 13. Additionally, the inhibition of intracellular DPP9 enhances the anti‐leukemic activity of parthenolide,28 while DPP9 may also act as a survival factor for cells from the Ewing's sarcoma family of tumors cells and protect them against cell death induced by endogenous neuropeptide Y 29. On the other hand, DPP9 overexpression was reported to inhibit phosphoinositide 3‐kinase/Akt signaling in an epidermal growth factor receptor‐dependent manner, attenuating cell proliferation and promoting apoptosis in human hepatoma cells 30.…”

The amino terminus extension in the long dipeptidyl peptidase 9 isoform contains a nuclear localization signal targeting the active peptidase to the nucleus

“…Both peptidases are ubiquitously expressed on mRNa levels in various organs and tissues and cell lines [18][19][20][21][22]. Changes in the levels of these peptidases appear to be critical for cell survival, as both overexpression or application of DPP8/9 inhibitors lead to cell death in several cell lines [23][24][25]. Recently, it was shown that knock-in mice with a serine to alanine mutation in the active site of DPP9 die 8-24 h after birth.…”