Content area
Full Text
Introduction
Progestagen-associated endometrial protein (PAEP) is a secreted glycoprotein, which was first isolated from human placenta, amniotic fluid, decidua of pregnancies and seminal plasma (1). It has been demonstrated to be important in a number of physiological processes, such as embryonic implantation, immunotolerance, contraception and gland differentiation. In recent years, several studies have demonstrated that PAEP is abnormally expressed in various types of tumors, such as endometrial carcinoma, ovarian cancer, breast cancer (2–5), lung cancer (6) and melanoma (7). Transfection of PAEP cDNA into the MCF-7 breast cancer cell line results in marked changes in cell growth behavior, with the suppression of proliferation and formation of acinar structures (8), suggesting that PAEP inhibits tumor cell growth and promotes cell differentiation as a tumor suppressive factor. Song et al(9) demonstrated that PAEP is also involved in neovascularization during tumor growth (9). However, our previous study presumed that PAEP is a tumor promoter in melanoma (10), suggesting contradictory results as compared to other studies.
Melanogenesis is a result of the malignant transformation of neural crest-derived melanocytes (11), and melanoma is one of the most aggressive forms of human cancer. Once metastasized, it is difficult to treat and is associated with high mortality rates. PAEP has been shown to be highly expressed in melanoma tissues and the majority of the melanoma cell lines tested in the literature thus far. Therefore, the present study aimed to establish melanoma cell lines with low PAEP gene expression to investigate their cytological and genetic functions in tumorigenesis and tumor development.
In the present study, RNA interference (RNAi) technology was utilized to silence PAEP gene expression, using transfection with PAEP-specific small interfering RNA (siRNA) or infection with lentiviral vector-mediated small hairpin RNA (shRNA) to lead to the transient or stable knockdown of PAEP gene expression in melanoma cells. The cell lines obtained from this study may be utilized to clarify the function of the PAEP gene.
Materials and methods
Cell lines and culture
Four cell lines (MCC69B, 624-MEL, 624.38-Mel and FEMX-I lines) originally procured from melanoma patients were used. MCC69B cells were isolated from a distant metastasis, the 624-Mel and 624.38-Mel metastatic melanoma cell lines were obtained from the National Cancer Institute (NIH). FEMX-I, provided by Oystein Fodstand from Norwegian Radium Hospital...