Cancer stem-like cells in Epstein-Barr virus-associated nasopharyngeal carcinoma

Although the Epstein-Barr virus(EBV) has spread to all populations in the world, EBV-associated nasopharyngeal carcinoma(NPC) is prevalent only in South China and Southeast Asia. The role of EBV in the malignant transformation of nasopharyngeal epithelium is the main focus of current researches. Radiotherapy and chemoradiotherapy have been successful in treating early stage NPC, but the recurrence rates remain high. Unfortunately, local relapse and metastasis are commonly unresponsive to conventional treatments. These recurrent and metastatic lesions are believed to arise from residual or surviving cells that have the properties of cancer stem cells. These cancer stem-like cells(CSCs) have the ability to selfrenew, differentiate, and sustain propagation. They are also chemo-resistant and can form spheres in anchorage-independent environments. This review summarizes recent researches on the CSCs in EBVassociated NPC, including the findings regarding cell surface markers, stem cell-related transcription factors, and various signaling pathways. In particular, the review focuses on the roles of EBV latent genes [latent membrane protein 1(LMP1) and latent membrane protein 2A(LMP2A)], cellular microRNAs, and adenosine triphosphate(ATP)-binding cassette chemodrug transporters in contributing to the properties of CSCs, including the epithelial-mesenchymal transition, stem-like transition, and chemo-resistance. Novel therapeutics that enhance the efficacy of radiotherapy and chemoradiotherapy and inhibitors that suppress the properties of CSCs are also discussed.

Mechanism of metastasis by membrane type 1-matrix metalloproteinase in hepatocellular carcinoma

AIM To investigate the precise role of membrane type 1-matrix metalloproteinase （NTI-NNP） in hepatocellular carcinoma （HCC） metastasis. METHODS- Human HCC cells Hep3B with overexpression of MTT-MMP were established by stable transfection, and compared with control cells carrying the empty vector. Cells were examined in vivo for their differences in the metastatic ability of athymic nude mice, and analyzed in vito for their differences in invasion ability by invasion chamber coated with Matrigel, adhesion towards collagen I and migration through culture chamber. Cell proliferation and apoptosis in adherent and suspension status were evaluated by MTr and flow cytometry analysis. RESULTS We found that overexpression of MT1-MMP could increase intrahepatic metastasis in nude mice with orthotopic implantation of HCC cells （incidence of 100% [MT1-MMP transfectants] vs 40% [vector control transfectants], P〈0.05）. NT1-MMP could also enhance cell invasion through Natrigel （107.7 vs 39.3 cells/field, P〈0.001）, adhesion towards matrix （0.30 vs 0.12 absorbance unit at 540 nm, P〈0.001）, cell migration （89.3 vs 39.0 cells/field, P〈0.001）, and cell proliferation （24.3 vs 40.5 h/doubling, P〈0.001）. We also observed that NTI-NNP supported cell survival （71.4% vs 23.9%, P〈0.001） with reduced apoptosis （43.7% vs51.0%, P〈0.05） in an attachment-free environment. CONCLUSION： MT1-MMP overexpression could enhance metastasis. In addition to its active role in matrix degradation during tumor invasion, MT1-MMP enhances tumor cell survival upon challenge of detachment, which is important during metastasis when cells enter the circulation.