Dipeptidyl peptidase 4 promotes epithelial cell transformation and breast tumourigenesis via induction of PIN1 gene expression

BACKGROUND AND PURPOSE

Dipeptidyl peptidase 4 (DPP4) is an aminopeptidase that is widely expressed in different cell types. Recent studies suggested that DPP4 plays an important role in tumour progression in several human malignancies. Here we have examined the mechanisms by which up-regulation of DPP4 expression causes epithelial transformation and mammary tumourigenesis.

EXPERIMENTAL APPROACH

Expression of DPP4 and the peptidylprolyl cis/trans isomerase, NIMA-interacting 1 (PIN1), and the cytotoxic effects of combined treatment with sitagliptin and juglone were investigated by immunohistochemistry, immunoblotting, real-time PCR, TUNEL and soft agar assays, using MCF7 cells. The effects of sitagliptin on tumour development in vivo were studied in the syngeneic 4T1 metastatic breast cancer model.

KEY RESULTS

Activity of the transcription factor E2F1 induced by EGF was enhanced by DPP4, thus increasing PIN1 expression. Furthermore, DPP4 enhanced MEK/ERK and JNK/c-Jun signalling induced by EGF, inducing AP-1 activity and epithelial cell transformation. In contrast, DPP4 silencing or DPP4 inhibition in MCF7 cells inhibited PIN1 expression via E2F1 activity induced by EGF, decreasing colony formation and inducing DNA fragmentation. In the syngeneic 4T1 metastatic breast cancer model, DPP4 overexpression increased tumour development, whereas treatment with sitagliptin and/or juglone suppressed it. Consistent with these observations, DPP4 levels were positively correlated with PIN1 expression in human breast cancer.

CONCLUSIONS AND IMPLICATIONS

DPP4 promoted EGF-induced epithelial cell transformation and mammary tumourigenesis via induction of PIN1 expression, suggesting that sitagliptin targeting of DPP4 could be a treatment strategy in patients with breast cancer.

Long-term treatment with empagliflozin as add-on to oral antidiabetes therapy in Japanese patients with type 2 diabetes mellitus

AIMS

To evaluate the safety and efficacy of empagliflozin for 52 weeks as add-on to one other oral antidiabetes therapy in Japanese patients with type 2 diabetes mellitus (T2DM).

METHODS

Patients on biguanide (n = 133), thiazolidinedione (n = 273), α-glucosidase inhibitor (n = 139), dipeptidyl-peptidase-4 inhibitor (n = 139) or glinide (n = 140) were randomized 1 : 1 to receive empagliflozin 10 or 25 mg double-blind as add-on therapy for 52 weeks. Patients on sulphonylurea (SU; n = 336) were randomized 2 : 2 : 1 to receive empagliflozin 10 or 25 mg double-blind or open-label metformin as add-on therapy for 52 weeks. The primary objective was to evaluate safety. Change from baseline in glycated haemoglobin (HbA1c) at week 52 was a secondary endpoint.

RESULTS

Adverse events (AEs) were reported in 67.6-84.6% of patients receiving empagliflozin. Confirmed hypoglycaemic AEs (plasma glucose ≤70 mg/dl and/or requiring assistance) were reported in 4.4 and 6.6%, respectively, of patients receiving empagliflozin 10 and 25 mg as add-on to SU and in 0.0 to 2.9%, respectively, of patients receiving empagliflozin 10 and 25 mg as add-on to other therapies. Baseline mean ± standard deviation HbA1c ranged from 7.51 ± 0.73 to 8.06 ± 0.76% across background therapy groups. At week 52, adjusted mean ± standard error changes from baseline in HbA1c ranged from -0.77 ± 0.06 to -1.00 ± 0.06% in patients receiving empagliflozin.

CONCLUSIONS

In Japanese patients with T2DM, empagliflozin 10 and 25 mg as add-on to one other oral antidiabetes therapy for 52 weeks were well tolerated and were associated with clinically meaningful reductions in HbA1c.