Screening differentially expressed genes in mouse hepatocarcinoma ascites cell line with high potential of lymphatic metastasis

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.

Annexin A7 and its binding protein galectin-3 influence mouse hepatocellular carcinoma cell line in vitro

Lymph node metastasis is recognized as an important mode of liver cancer metastasis. Our previous study has built two hepatocarcinoma cell lines, Hca-F with high (75%) and Hca-P with low (25%) incidences of lymph node metastasis, and has indicated that annexin A7 is an important factor in the lymphatic metastasis of tumors. There is evidence that galectin-3 is the binding protein of annexin A7 and works in protein complexes. Our current study shows that both annexin A7 and galectin-3 express higher in Hca-F than Hca-P. Annexin A7 was successfully down-regulated in Hca-P by RNA interference, and this resulted in concomitant reduction of galactin 3 expression in annexin A7 down regulated compared to the control and N-control cells. Using CCK-8 assay, the expression level of annexin A7 and galectin-3 were found to have correlation with the proliferation ability; Transwell assay showed annexin A7 and galectin-3 are involved in cell migration and invasion regulation in mouse hepatocellular carcinoma cell lines, immunofluorescence assay indicate annexin A7 and galectin-3 were co-located annexin A7 and galectin-3 played roles in DNA damage and cell proliferation cycle checkpoint arrest pathway. Those phenomena indicated that annexin A7 influences lymphatic metastasis of tumors by interacting with galectin-3 through the regulation of tumor cell proliferation, attachment, migration and invasion.

Identification of differentially expressed genes in spontaneously regressing melanoma using the MeLiM swine model

Partial and some few cases of complete spontaneous regression have been observed in cutaneous melanoma patients but little is known about the molecular mechanisms involved. The Melanoblastoma-bearing Libechov Minipig (MeLiM) is a suitable animal model to study the phenomenon of spontaneous regression because MeLiM pigs exhibit naturally occurring melanomas which regress completely 6 months after birth. In this study, we used suppression subtractive hybridization (SSH) to identify molecular determinants of melanoma regression within swine melanoma tissues and melanoma cell cultures. Several markers involved in cell-adhesion, -communication, -motility, signal transduction, negative regulation of cell proliferation, transport and immune response were identified that correlated with melanoma regression whereas the main genes involved in melanin synthesis showed a strong downregulation. For the most differentially expressed genes, we validated the results obtained by SSH with qRT-PCR and with immunohistochemistry for some of them (CD9, MITF, RARRES1). Most notable, for the first time in melanoma, we identified the retinoic acid responder 1 gene (RARRES1) as a main actor of the regression process in melanoma. This first gene expression study in swine melanoma regression, may contribute to the finding of new therapeutic targets for human melanoma treatment.

Identification of differentially expressed genes in mouse hepatocarcinoma ascites cell line with low potential of lymphogenous metastasis

AIM: To identify genes differentially expressed in mouse hepatocarcinoma ascites cell line with low potential of lymphogenous metastasis.

METHODS: A subtracted cDNA library of mouse hepatocarcinoma cell line with low potential of lympho-genous metastasis Hca-P and its synogenetic cell line Hca-F with high metastatic potential was constructed by suppression subtracted hybridization (SSH) method. The screened clones of the subtracted library were sequenced and GenBank homology search was performed.

RESULTS: Fifteen differentially expressed cDNA fragments of Hca-P were obtained which revealed 8 known genes, 4 expressed sequence tags (ESTs) and 3 cDNAs showed no homology.

CONCLUSION: Tumor metastasis is an incident involving multiple genes. SSH is a useful technique to detect differentially expressed genes and an effective method to clone novel genes.