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Introduction
Primary liver cancer (PLC) is one of the most fatal types of cancer in humans with a rising incidence worldwide. It accounts for 70–90% of the total liver cancer burden and is the third most common cause of cancer-associated mortality globally (1). Long-term prognosis of PLC remains poor, with the majority of patients succumbing to disease due to recurrence. Therefore, understanding the pathogenesis of primary PLC is crucial for improving the efficacy of current treatment strategies.
The liver tumor microenvironment is an essential contributor to PLC initiation and progression. It has been demonstrated that various stromal cell types are recruited to neoplasms, where they are activated and substantially promote the proliferation, invasion and metastatic potential of cancer cells (2,3). Hepatic stellate cells (HSCs) belong to one of the most important stromal cell types in the liver tumor environment. Numerous prior studies have revealed that culturing hepatocytes and LX2 cells (a spontaneous immortalized human HSC cell line) results in bidirectional cross-talk, with LX2 cells promoting PLC proliferation and migration, thus inducing an inflammatory reaction (4,5). Simultaneous in vivo subcutaneous implantation of human HSCs and PLC cells in nude mice promotes tumor growth, invasiveness and inhibits necrosis (6).
Neuropilin-1 (NRP-1) is a transmembrane receptor for class 3 semaphorins (7) and vascular endothelial growth factor isoforms (8). It is expressed in a wide range of tissues and mediates diverse cellular functions, including migration, adhesion, proliferation and apoptosis (9,10). Recently, NRP-1 has been implicated in HSC activation and cirrhosis progression (11). However, the effect of HSCs on PLC cells following NRP-1 expression silencing remains unclear. The present study demonstrated that silencing NRP-1 expression of HSCs may inhibit the activation of HSCs, as well as attenuate the malignant progression of PLC cells in vitro and in vivo.
Materials and methods
Cell lines and culture
The LX2 human HSCs were provided by the American Type Culture Collection (Manassas, VA, USA). HepG2 human hepatoblastoma cells were provided by the Translation Medicine Center of Xi'an Jiaotong University (Xi'an, China). LX2 and HepG2 cells were cultured in Dulbecco's modified Eagle's medium (DMEM; HyClone; GE Healthcare, Chicago, IL, USA) supplemented with 10% fetal bovine serum (FBS; MP Biomedicals, Solon, OH, USA) and 1% streptomycin/penicillin (100 IU/ml; Gibco; Thermo Fisher Scientific, Inc., Waltham, MA,...