Protease-activated receptor 4 (PAR4), a member of
G-protein coupled receptors family, was recently reported to exhibit decreased expression in
gastric cancer and esophageal squamous
cancer, yet increased expression during the progression of
prostate cancer.
Trefoil factor 2 (TFF2), a small
peptide constitutively expressed in the gastric mucosa, plays a protective role in restitution of gastric mucosa. Altered TFF2 expression was also related to the development of
gastrointestinal cancer. TFF2 has been verified to promote cell migration via PAR4, but the roles of PAR4 and TFF2 in the progress of
colorectal cancer are still unknown. In this study, the expression level of PAR4 and TFF2 in
colorectal cancer tissues was measured using real-time PCR (n = 38), western blotting (n=38) and tissue microarrays (n = 66). The
mRNA and
protein expression levels of PAR4 and TFF2 were remarkably increased in
colorectal cancer compared with matched noncancerous tissues, especially in positive lymph node and poorly differentiated
cancers. The
colorectal carcinoma cell LoVo showed an increased response to TFF2 as assessed by cell invasion upon PAR4 expression. However, after intervention of PAR4 expression, PAR4 positive
colorectal carcinoma cell HT-29 was less responsive to TFF2 in cell invasion. Genomic
bisulfite sequencing showed the hypomethylation of PAR4 promoter in
colorectal cancer tissues and the hypermethylation in the normal mucosa that suggested the low methylation of promoter was correlated to the increased PAR4 expression. Taken together, the results demonstrated that the up-regulated expression of PAR4 and TFF2 frequently occurs in
colorectal cancer tissues, and that overexpression of PAR4 may be resulted from promoter hypomethylation. While TFF2 promotes invasion activity of LoVo cells overexpressing PAR4, and this effect was significantly decreased when PAR4 was knockdowned in HT-29 cells. Our findings will be helpful in further investigations into the functions and molecular mechanisms of
Proteinase-activated receptors (PARs) and
Trefoil factor factors (TFFs) during the progression of
colorectal cancer.