PELP1 is a novel oncogene in gastric tumorigenesis and negatively regulated by miR-15 family microRNAs

BACKGROUD: Gastric cancer (GC) is one of the leading causes of cancer-related death in East Asia and some South American countries, but its mechanism has not been clarified clearly. Proline-, glutamic acid-, and leucine-rich protein-1 (PELP1), a coregulatory molecule of estrogen receptor alpha (ER alpha), is up-regulated in series of cancers such as endometrial carcinoma, ovarian cancer, colorectal cancer, breast cancer, and non-small cell lung cancer. However, PELP1's role in GC is still obscure, and its aberrant expression in cancers also remains to be explained. METHODS: Immunohistochemical staining and Real-time PCR were used to compare the expression level of PELP1 in GC tissues and adjacent tissues. Western blot was used to detect the expression of PELP1 in cell lines. Kaplan-meier analysis and chi-square test were applied to evaluate the potential of PELP1 to function as a cancer biomarker. RNA interference was used to inhibit PELP1 expression in GC cells, followed by detecting cell proliferation, apoptosis, migration and invasion. Luciferase assay was conducted to validate whether miR-15 family members can directly target PELP1. RESULTS: In this study, we validated that PELP1 was significantly up-regulated in GC samples and cell lines. It was also demonstrated that the up-regulation of PELP1 was associated with several clinicopathologic features such as tumor diameter (P < 0.001), serum CEA level (P = 0.034), and lymphatic metastasis (P = 0.0009) of GC patients, and its high expression was correlated with shorter disease-free survival and overall survival of the patients. Knockdown of PELP1 remarkably arrested the proliferationcn migration and invasion, while promoted apoptosis. We also confirmed that miR-15 family microRNAs, most of which were down-regulated and tumor suppressor in cancers, were posttranscriptional regulators of PELP1. CONCLUSION: In conclusion, we demonstrated that PELP1 was an oncogene of GC associated with patients' prognosis and miR-15 family members contributed to its aberrant expression in cancers.