Figure 6.

PIN1 overexpression induced by DPP4 is associated with human breast tumourigenesis. (A) Representative samples showing the results of immunohistochemical analysis of human normal breast tissue (Nor) and infiltrating ductal carcinoma of the breast (Tum), performed using an anti‐DPP4 antibody. Correlation was analysed using Fisher's exact test. (B) Representative samples showing the results of immunohistochemical analysis of infiltrating ductal carcinoma of the breast, performed using anti‐DPP4 and anti‐PIN1 antibodies on adjacent sections of samples. Correlations were analysed using Fisher's exact test. (C) MCF7 cells, mock transfected (GFP‐MCF7) or overexpressing PIN1 (PIN1‐MCF7), were treated with 1 mM sitagliptin (SITG) in a soft agar matrix and incubated at 37°C in a 5% CO₂ atmosphere for 14 days. The colonies from three separate experiments are photographed, and the average number of colonies was calculated. Columns represent the means ± SD of triplicate samples. P < 0.05, significantly different from control cells. (D) MCF7 cells were treated with 1 mM sitagliptin with/without additional treatment with juglone (JUG), dose dependently in soft agar matrix, and incubated at 37°C in a 5% CO₂ atmosphere for 14 days. The colonies from three separate experiments are photographed, and the average number of colonies was calculated. Columns represent the means ± SD of triplicate samples. P < 0.05, significantly different from control cells. . (E and F) 4T1 cells were treated or not treated with 10 mM sitagliptin, alone (SITG) or in combination with 100 μM juglone (SITG/JUG). Treated cells were injected into the mammary glands of BALB/c mice (n = 30) and allowed to grow until tumours formed (14 days). Representative pictures of tumours (E) and tumour volumes and weights (F) are shown. Columns represent the means ± SD of triplicate samples. *P < 0.05, significantly different from control group (injected with cells mock‐treated with PBS only).