Actin-related protein 2/3 complex subunit 2-enriched extracellular vesicles drive liver cancer metastasis.

BACKGROUND: Extracellular vesicles (EVs) play pivotal roles in tumor growth, cancer metastasis and angiogenesis. Here, we aimed to identify proteins that contribute to the functionality of EVs derived from metastatic hepatocellular carcinoma (HCC) cells. METHODS: Proteins of EVs derived from metastatic HCC cells and normal liver cells were analyzed by mass spectrometry. Proteomic profiling identified actin-related protein 2/3 complex subunit 2 (ARPC2) to be highly expressed in EVs of metastatic HCC cells. The expression of ARPC2 in EVs and HCC tissues was examined using immunoblotting and TCGA database, respectively. The functional roles of EV-ARPC2 were investigated by knockout approach and various in vitro and in vivo assays. RESULTS: ARPC2 was highly expressed in EVs of metastatic cells but barely detected in non-metastatic HCC cells and normal liver cells. Immunogold labeling showed the presence of APRC2 on the surface of EVs. Analysis of TCGA database of liver cancer revealed ARPC2 overexpression was correlated with poor prognosis of patients. ARPC2 was knockout in metastatic HCC cells. EVs derived from knockout cells displayed compromised activity in enhancing cell growth, motility and metastasis compared to EVs of control cells. Pimozide, an inhibitor of APRC2, also inhibited the promoting effect of EVs of metastatic cells in lung colonization of tumor cells in mice. CONCLUSION: This study reveals previously unreported expression and function of ARPC2 in EVs. EVs with highly expressed ARPC2 enhance cancer cell growth and metastasis. ARPC2 may provide a prospective target for the novel treatment of HCC patients.

[MicroRNA-34a regulates cell cycle by targeting CD44 in human bladder carcinoma cells].

OBJECTIVE: To investigate the role of microRNA-34a (miR-34a) in regulating the cell cycles of bladder cancer cell line J82 and explore the underlying mechanism. METHODS: J82 cells were transfected with a miR-34a mimic or an inhibitor to induce miR-34a overexpression or silencing. The RNA level of miR-34a in the transfected cells was detected by real-time PCR, and CD44 expressions at the mRNA and protein levels were detected by real-time PCR and Western blotting. Luciferase reporter assay was used to detect the activation of 3'UTR of CD44, and flow cytometry was performed to analyze the cell cycle changes. RESULTS: The expression level of miR-34a was significantly increased and CD44 expression significantly lowered in cells transfected with miR-34a mimic; miR-34a inhibitor transfection caused reverse effects on miR-34a and CD44 expressions. MiR-34a mimics downregulated while miR-34a inhibitor enhanced the activation of 3'UTR of CD44 with corresponding changes in the expressions of some cell cycle-related proteins. MiR-34a mimics and miR-34a inhibitor induced opposite changes in J82 cell cycle, which were partly reversed by CD44. CONCLUSION: MiRNA-34a regulates cell cycles by targeting CD44 in human bladder carcinoma cell line J82.

Mechanistic insights into the roles of three linked single-stranded template binding residues of MMLV reverse transcriptase in misincorporation and mispair extension fidelity of DNA synthesis.

To obtain some insights into the structure-function relationship of Moloney murine leukemia virus (MMLV) reverse transcriptase (RT), we modeled the catalytic state ternary complexes of this protein using the corresponding RT from human immunodeficiency virus type 1 (HIV-1) and available structures of MMLV RT. We observed that three MMLV RT single-stranded template binding residues, Y64, D114, and R116, act as a linked set through mutual interactions, including hydrogen bonding and ion-pairing. The analogous residues of HIV-1 RT have a somewhat different environment and they lack this linked phenomenon. To understand the functional implication of this linked set of MMLV RT, we performed site-directed mutagenesis at these three positions. Then the mutant enzymes were examined for their biochemical properties and nucleotide selectivity. Mutagenesis of these residues (Y64A, D114A, and R116A) resulted in enzymes with slight to modest changes in polymerase activities. The processivity of DNA synthesis correlated positively with the binding affinity of the MMLV RT variants. Lower fidelity in mutants was indicated by measurements of misincorporation and mispair extension fidelity of wild type (WT) and mutant RTs, in contrast to earlier works that indicate that mutations at the analogous positions in HIV-1 RT result in relatively higher fidelity. These data together with structural analysis suggest that this structural set may therefore be a key factor responsible for the different fidelity of these two RTs.