Characterization of the 3a protein of SARS-associated coronavirus in infected vero E6 cells and SARS patients.

Proteomics was used to identify a protein encoded by ORF 3a in a SARS-associated coronavirus (SARS-CoV). Immuno-blotting revealed that interchain disulfide bonds might be formed between this protein and the spike protein. ELISA indicated that sera from SARS patients have significant positive reactions with synthesized peptides derived from the 3a protein. These results are concordant with that of a spike protein-derived peptide. A tendency exists for co-mutation between the 3a protein and the spike protein of SARS-CoV isolates, suggesting that the function of the 3a protein correlates with the spike protein. Taken together, the 3a protein might be tightly correlated to the spike protein in the SARS-CoV functions. The 3a protein may serve as a new clinical marker or drug target for SARS treatment.

From proteomic analysis to clinical significance: overexpression of cytokeratin 19 correlates with hepatocellular carcinoma metastasis.

To better understand the mechanism underlying the hepatocellular carcinoma (HCC) metastasis and to search potential markers for HCC prognosis, differential proteomic analysis on two well-established HCC cell strains with high and low metastatic potentials, MHCC97-H and MHCC97-L, was conducted using two-dimensional gel electrophoresis followed by matrix-assisted laser desorption/time-of-flight mass spectrometry. Cytokeratin 19 (CK19) was identified and found to be overexpressed in MHCC97-H as compared with MHCC97-L. This result was further confirmed by two-dimensional Western blot analysis and immunofluorescence assay. Furthermore, one-dimensional Western blot analysis showed consistently increased CK19 expression in progressively more metastatic cells. Immunohistochemical study on 102 human HCC specimens revealed that more patients in the CK19-positive group had overt intrahepatic metastases (satellite nodules, p < 0.05; vascular tumor emboli, p < 0.001; tumor node metastatis staging, p < 0.001). CK19 fragment CYFRA 21-1 levels measured in sera from nude mice model of human HCC metastasis with radioimmunoassay increased in parallel with tumor progression and rose remarkably when pulmonary metastases occurred. The results demonstrated that overexpression of CK19 in HCC cells is related to metastatic behavior. Serum CK19 level might reflect the pathological progression in some HCC and may be a useful marker for predicting tumor metastasis and a therapeutic target for the treatment of HCC patients with metastases.

c-Myc degradation induced by DNA damage results in apoptosis of CHO cells.

Although tripchlorolide (TC), a compound purified from a Chinese herb Tripterygium Wilfordii Hook, has been demonstrated to be a potent antitumor agent, its mechanisms of action are unknown. The present study shows that TC induces apoptosis of Chinese Hamster Ovary (CHO) cells. Most strikingly, TC was particularly potent in inducing apoptosis of the UV41 mutant CHO cells, which are deficient in the ERCC4 gene encoding a nucleotide excision repair protein. TC caused a higher level of DNA damage in UV41 cells than those in the wild-type CHO cells or EM9 cells, which are deficient in single-strand break repair. These results provided a critical link between apoptotic hypersensitivity and DNA damage in defective nucleotide excision repair pathway of UV41 cells by TC treatment. Further analysis showed that degradation of the c-Myc protein in TC-treated UV41 cells was much stronger than those in the wild-type CHOAA8 and the EM9. A proteasome inhibitor, MG132, reduced both the degradation of c-Myc and apoptosis in TC-treated UV41 cells. Expression of exogenous c-Myc also inhibited apoptosis of TC-treated UV41 cells. These results indicate that c-Myc degradation induced by DNA damage in the presence of TC contributes to induction of apoptosis of UV41 cells.