The expression pattern of long non-coding RNA PVT1 in tumor tissues and in extracellular vesicles of colorectal cancer correlates with cancer progression

摘要

The plasmacytoma variant translocation 1 gene (PVT1) is a large non-coding locus at adjacent of c-Myc, and long non-coding RNA PVT1 is now recognized as a cancerous gene co-amplified with c-Myc in various cancers. But the expression and functional role of PVT1 in colorectal cancer are still unelucidated. In addition, all the reported long non-coding RNAs so far are discovered in either cells or tissues, but no research about long non-coding RNAs detection in extracellular vesicles has been reported yet. In the present study, we firstly investigated the expression of PVT1 in colorectal cancer specimens and its correlation with the expression of c-Myc and other related genes by real-time polymerase chain reaction. Then, we isolated the extracellular vesicles from colorectal cancer cells culturing medium by differential centrifugation and detected the PVT1 expression in extracellular vesicles by using real-time polymerase chain reaction. The PVT1 targeting siRNA was transfected into SW480 and SW620 cells, and 3-(4, 5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium assay and flow cytometry were used to evaluate the cell proliferation and apoptosis. The results showed that the PVT1 expression in tumor tissues was higher than that in normal tissues, which was significantly correlated with the expression of c-Myc and three c-Myc regulating genes FUBP1, EZH2, and NPM1 and also correlated with the expression of two other PVT1-associated transcript factors nuclear factor-κB and myocyte-specific enhancer factor 2A. Here, we reported for the first time that PVT1 as a long non-coding RNA was successfully detected in extracellular vesicles excluded from SW620 and SW480 cells, and the expression level of PVT1 was higher in extracellular vesicles from the more aggressive cell SW620 than from SW480. The results also showed that by down-regulating the PVT1 expression, the c-Myc expression was suppressed, the cell proliferation was inhibited, and cell apoptosis was increased. Taken together, these findings implicated that PVT1 may be a new oncogene co-amplified with c-Myc in colorectal cancer tissues and extracellular vesicles and functionally correlated with the proliferation and apoptosis of colorectal cancer cells.