Construction and selection of subtracted cDNA library of mouse hepatocarcinoma cell lines with different lymphatic metastasis potential

AnnexinA7 promotes epithelial-mesenchymal transition by interacting with Sorcin and contributes to aggressiveness in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide, and metastasis is the major cause of the high mortality of HCC. In this study, we identified that AnnexinA7 (ANXA7) and Sorcin (SRI) are overexpressed and interacting proteins in HCC tissues and cells. In vitro functional investigations revealed that the interaction between ANXA7 and SRI regulated epithelial-mesenchymal transition (EMT), and then affected migration, invasion, and proliferation in HCC cells. Furthermore overexpression/knockdown of ANXA7 was remarkably effective in promoting/inhibiting tumorigenicity and EMT in vivo. Altogether, our study unveiled a mechanism that ANXA7 promotes EMT by interacting with SRI and further contributes to the aggressiveness in HCC, which provides a novel potential therapeutic target for preventing recurrence and metastasis in HCC.

Inhibition of lymphatic metastases by a survivin dominant-negative mutant

Metastasis is the most lethal attribute of human malignancy. High-level expression of survivin is involved in both carcinogenesis and angiogenesis in cancer. Previous studies indicate that a mutation of the threonine residue at position 34 (Thr34Ala) of survivin generates a dominant-negative mutant that induces apoptosis, inhibits angiogenesis, and suppresses highly metastatic breast carcinoma in mouse models. We investigated the efficacy of gene therapy with a survivin dominant-negative mutant and possible factors related to lymph node metastasis. The metastasis rate was compared between each group in order to find a survivin-targeted therapy against lymphangiogenesis in its earliest stages. We established lymph node metastasis models and treated animals with H22 tumors with Lip-mSurvivinT34A (Lip-mS), Lip-plasmid (Lip-P), or normal saline (NS). Eight days after the last dose, five randomly chosen mice from each group were sacrificed. We detected the apoptotic index, microvessel density (MVD), lymphatic microvessel density (LMVD), and the expression of VEGF-D with immunohistochemistry. After the remaining animals were sacrificed, we compared the tumor-infiltrated lymph nodes in each group. Administration of mSurvivinT34A plasmid complexed with cationic liposome (DOTAP/chol) resulted in the efficacious inhibition of tumor growth and lymph node metastasis within the mouse H22 tumor model. These responses were associated with tumor cell apoptosis, and angiogenesis and lymphangiogenesis inhibition. Our results suggested that Lip-mSurvivinT34A induced apoptosis and inhibited tumor angiogenesis and lymphangiogenesis, thus suppressing tumor growth and lymphatic metastasis. The mSurvivinT34A survivin mutant is a promising strategy of gene therapy to inhibit lymphatic metastasis.

Comparative analysis of the membrane proteome of closely related metastatic and nonmetastatic tumor cells

The identification of proteins that are preferentially expressed on the membrane of metastatic tumor cells is of fundamental importance in cancer research. Here, we report the systematic comparison of the membrane proteome of two closely related murine teratocarcinoma cell lines (F9B9 and F9DR), of which only one (F9DR) is capable of forming liver metastases in vivo. The proteomic methodology used in this study featured the surface protein biotinylation on tumor cells followed by protein purification on streptavidin resin and relative quantification of corresponding tryptic peptides by mass spectrometric procedures. The study allowed the identification of 998 proteins and the determination of their relative abundance. Proteins previously known to be associated with metastatic spread were found to be either up-regulated (e.g., synaptojanin-2) or down-regulated (e.g., Ceacam1) in F9DR cells. A dramatic increase in abundance at the cell membrane was observed for a broad variety of proteins (e.g., high-mobility group protein B1), which were mainly thought to reside in intracellular compartments, a finding that was confirmed using confocal laser scanning microscopy and immunochemical analysis of cell cultures. Furthermore, we showed by microautoradiographic analysis that certain target proteins can readily be reached by intravenously administered radiolabeled antibodies. Finally, we showed that the most promising antigens for antibody-based pharmacodelivery approaches are strongly and selectively expressed on the surface of tumor cells in three different syngeneic mouse models of liver metastases. Taken together, our results indicate that the expression of intracellular proteins on the membrane of metastatic cells is a feature much more common than previously expected.

Screening and cloning of target genes transactivated by hepatitis C virus p7 protein

AIM: To clone and identify human genes transactivated by hepatitis C virus p7 (HCVp7) protein.

METHODS: Suppression subtractive hybridization (SSH) and bioinformatic techniques were used for screening and cloning of the target genes transactivated by HCVp7 protein. The mRNA was isolated from HepG2 cells transfected with pcDNA3.1(-)-p7 and pcDNA3.1(-) empty vector respectively, and SSH method was employed to analyze the differentially expressed DNA sequence between the two groups. After digestion with restriction enzyme Rsa I, cDNAs of small size were obtained. Then tester cDNA was divided into two groups and ligated to the specific adaptor 1 and 2 respectively. After tester cDNA was hybridized with driver cDNA twice and underwent nested PCR twice, and then the product was subcloned into T/A plasmid vectors to set up the subtractive library. Amplification of the library was carried out after transfected with E. coli strain DH5α. The cDNA was sequenced and analyzed in GenBank with Blast search after PCR.

RESULTS: The subtractive library of genes transactivated by HCVp7 was constructed successfully. The amplified library contained 71 positive clones. Colony PCR showed that 56 clones contained 200-1 000 bp inserts. Sequence analysis was performed in 33 clones randomly, and the full-length sequences were obtained with bioinformatics method. Altogether 15 coding sequences were obtained, including 14 known and 1 unknown.

CONCLUSION: The obtained sequences may be target genes transactivated by HCV p7, and some genes coding proteins get involved in cell cycle regulation, metabolism, and cell apoptosis.