Inhibition of Dipeptidyl Peptidase-4 Accelerates Epithelial–Mesenchymal Transition and Breast Cancer Metastasis via the CXCL12/CXCR4/mTOR Axis

Abstract

Dipeptidyl peptidase (DPP)-4 is a multifunctional glycoprotein involved in various biological and pathologic processes. DPP-4 has been widely recognized as a therapeutic target for type 2 diabetes mellitus but is also implicated in the development of human malignancies. Here, we show that inhibition of DPP-4 accelerates breast cancer metastasis via induction of CXCL12/CXCR4, which activates mTOR to promote epithelial-mesenchymal transition (EMT). In cultured cells, DPP-4 knockdown induced EMT and cell migration. Treatment with the DPP-4 inhibitor KR62436 (KR) promoted primary tumor growth and lung metastasis in a 4T1 tumor allograft mouse model; DPP-4 knockdown in 4T1 cells displayed similar phenotypes in vivo and in vitro. KR treatment enhanced the levels of CXCL12/CXCR4 and phosphorylated mTOR, which were associated with the induction of EMT in metastatic cancer cells. KR-induced EMT in cancer cells was inhibited by treatment with the CXCR4 inhibitor AMD3100 or the mTOR inhibitor rapamycin, and AMD3100 suppressed KR-induced metastasis in vivo. Our findings suggest that DPP-4 plays a significant role in cancer biology and that inhibition of DPP-4 promotes cancer metastasis via induction of the CXCL12/CXCR4/mTOR/EMT axis.Significance: These findings reveal that inhibition of DPP-4 increases the metastatic potential of breast cancer. This is especially important given the potential use of DPP-4 inhibition as a therapeutic strategy for type 2 diabetes.

Deficiency in Dipeptidyl Peptidase-4 Promotes Chemoresistance Through the CXCL12/CXCR4/mTOR/TGFβ Signaling Pathway in Breast Cancer Cells

“…In our previous study, we have confirmed that DPP-4 inhibition induced the EMT through the CXCL12/CXCR4/mTOR axis in breast cancer [17]. Here, we demonstrated that KR+DOX-induced overexpression of ABC transporters were significantly suppressed by the CXCR4 inhibitor AMD3100 in 4T1 cells ( Figure 2A) and were associated with the suppression of CXCL12 and CXCR4 ( Figure S1A).…”

“…EMT-related transcription factors (TFs) have been shown to play vital roles in regulating ABC transporter expression [36]. As shown previously [17], DPP-4 deficiency induced the EMT, which was characterized by the suppression of E-cadherin and the induction of α-SMA in 4T1 cells, and the trends were much more prominent in KR+DOX treated cells ( Figure 3A) and DOX-treated DPP-4-kd 4T1 cells ( Figure 3B). Immunofluorescence analysis revealed that primary tumors of DPP-4-kd 4T1 cells exhibited EMT markers ( Figure 3C).…”

“…In recent studies, researchers have revealed that overexpression of EMT-related transcription factors (TFs), such as snail, enhanced the chemoresistance through the induction of P-gp and ABCG2 in breast cancer cells [42,43]. In our previous study, we demonstrated that deficiency in DPP-4 induced EMT in 4T1 cells, MCF-7 cells and MDA-MB-231 cells and accelerated lung metastasis of breast cancer in vivo via the CXCL12/CXCR4/mTOR axis [17]. This signaling pathway could be also relevant in the chemoresistance associated with ABC transporters in DPP-4-deficient cells, and EMT-related TFs played a major role in regulating ABC transporters expression, as described in a recent study.…”

“…The mouse 4T1 cell DPP-4 shRNA vectors were constructed in the pSIH vector (System Biosciences) using synthetic oligonucleotides against mouse DPP-4 antisense sequences (shDPP-4-1: 50-TAGAAGGAGTATTCAATGAGC-30, shDPP-4-2: 50-AATAGTCAGCTA-GTGAATACG-30 or shDPP-4-3: 50-ATAGTAGAGGATATTTCTTGG-30) with a 50-CTCGAG-30 loop (detailed in a previous work) [17]. 4T1 cells were transfected with siRNA (100 nmol/L) targeting mouse snail (5 -UUGGGAAGUUGGCCCAAAGCCAGGGA-3 ; 375453F10, Invitrogen, Tokyo, Japan) and mouse E-cadherin (5 -CGCCACAGAUGAUGGUUCACCCAUU-3 ; 379261A08, Invitrogen, Tokyo, country).…”

“…Furthermore, a study suggested that DPP-4 might be involved in increased sensitivity of epithelial ovarian carcinoma cells to chemotherapy [16]. We have recently shown that a DPP-4 inhibitor accelerated the epithelial mesenchymal transition (EMT) and lung metastasis via the CXCL12/CXCR4/mTOR axis in breast cancer cells [17]. Signaling through mTOR is vital for proliferation and survival in cancers and plays a central role in adaptive resistance to inhibitors of oncogenic signaling pathways [18,19].…”