Monitoring mmp-9 gene expression in stromal cells using a novel transgenic mouse model.

Matrix metalloproteinase (MMP)-9 (gelatinase B) is involved in extracellular matrix degradation in the context of the motility and in in vivo migration of normal and malignant cells. Accordingly, its expression is highly regulated at the transcriptional level. In several types of human cancers, MMP-9 expression is abnormally elevated and has been associated with poor prognosis. Such high levels of MMP-9 expression are found in tumor cells and in stromal components. Therefore, it is important to understand the spatiotemporal expression pattern of MMP-9 in tissues for the development of effective therapeutic strategies that are aimed at suppressing mmp-9 gene activation. In the present work, we describe a transgenic mouse model harboring a luciferase gene under the control of the murine mmp-9 promoter. We found that the expression pattern of the transgene was similar to that of the endogenous mmp-9 gene either constitutively or following inflammatory stimuli. A constitutive transgene expression was observed in the bone marrow, consistent with the observed high levels of endogenous mmp-9 gene expression normally found in the bone. LPS injection in mice also induced a consistent and significant increase in bioluminescent signals in the liver, which is a major target of LPS-induced septic shock. Finally, we further used the model to provide evidence that mmp-9 is activated in stromal cells of the lung and spleen in melanoma tumor-bearing mice. This bioluminescent imaging model may facilitate in vivo monitoring of MMP-9 activation in stromal cells in tumor progression and inflammatory diseases.

EGR-1 activation by EGF inhibits MMP-9 expression and lymphoma growth.

Progression of hematologic malignancies is strongly dependent on bidirectional interactions between tumor cells and stromal cells. Expression of members of the matrix metalloproteinase (MMP) family by stromal cells is a central event during these interactions. However, although several studies have focused on the mechanisms responsible for induction of MMP in stromal cells, the signals that negatively regulate their secretion of in these cells remain largely unknown. Here, we provide evidence that MMP-9 production by stromal cells is suppressed through activation of early growth response protein 1 (EGR-1), thereby inhibiting the growth of thymic lymphoma. We found that EGR-1 expression is induced in stromal cells after contact with lymphoma cells via epidermal growth factor (EGF). Moreover, development of thymic lymphoma was inhibited when induced by lymphoma cells overexpressing EGF compared with control lymphoma cells. Using transgenic mice containing MMP-9 promoter-driven luciferase transgene in its genome, we further demonstrated that EGF/EGR-1 repressed transcriptional activation of the MMP-9 gene by stromal cells. De novo expression of EGR-1 alone by gene transfer or exposure to recombinant human EGF also inhibited MMP-9 expression. Taken together, these results indicate that EGR-1 could be a source of novel targets for therapeutic intervention in lymphoid tumors in which MMP-9 plays a critical role.

Overexpression of galectin-7, a myoepithelial cell marker, enhances spontaneous metastasis of breast cancer cells.

Galectins are members of a family of beta-galactosides-binding proteins that have recently emerged as novel modulators in different aspects of cancer. The expression of galectins in tumors and/or the tissue surrounding them has been well documented. Since galectin-7 expression has been associated with epithelial tissues and varies significantly in various types of cancer, we have investigated for the first time its role in breast cancer. Using two preclinical mouse models, high levels of galectin-7 expression in breast cancer cells drastically increased their ability to metastasize to lungs and bones. Significant increases in the number of pulmonary metastases and osteolytic lesions were induced by overexpression of galectin-7 compared with control cells. In human tissues, galectin-7 was specifically found in myoepithelial cells of normal human breast tissue, but not in luminal cells. Its expression was severely altered in breast carcinoma, many samples showing greater than 70% of galectin-7 positive cells. High expression levels of galectin-7 were restricted to high-grade breast carcinomas, including HER2 overexpressing and basal-like groups. In HER2 overexpressing cases, galectin-7 expression was associated with lymph node axillary metastasis. Taken together, our results indicate that galectin-7 may represent a potential target for both specific detection and therapeutic inhibition of metastatic breast cancer.

Galectin-7 in lymphoma: elevated expression in human lymphoid malignancies and decreased lymphoma dissemination by antisense strategies in experimental model.

Galectin-7 is found mainly in stratified squamous epithelia as well as in various other types of cancer cells. As with other members of the galectin family, the expression of galectin-7 has been shown to negatively regulate the development of some tumors while correlating with the progression of other tumor types. For example, up-regulation of galectin-7 is associated with rat mammary carcinomas and with progression to T-cell malignancy. Here, we provide evidence indicating that galectin-7 functions as an important molecule in the dissemination of lymphoma cells in vivo. We found that stable transfection of lymphoma cells with a plasmid encoding antisense galectin-7 cDNA significantly inhibited the dissemination and invasion of lymphoma cells to peripheral organs, thereby increasing the survival of mice. We also found that inhibition of galectin-7 in aggressive lymphoma cells correlated with a decreased invasion of tumor cells in target organs and a reduced expression of matrix metalloproteinase-9, a gene associated with a poor prognosis in non-Hodgkin's lymphoma. We finally examined the expression of galectin-7 in 50 specimens of different mature B-cell neoplasms and found high galectin-7 expression levels in a significant proportion of mature B-cell neoplasms but not in normal B cells. Taken together, these findings suggest that galectin-7 is a potential therapeutic target in the treatment of lymphoid malignancies.

Expression and functions of galectin-7 in human and murine melanomas.

The identification of galectin-7 as a p53-induced gene and its ability to induce apoptosis in many cell types support the hypothesis that galectin-7 has strong antitumor activity. This has been well documented in colon cancer. However, in some cases, such as breast cancer and lymphoma, its high expression level correlates with aggressive subtypes of cancer, suggesting that galectin-7 may have a dual role in cancer progression. In fact, in breast cancer, overexpression of galectin-7 alone is sufficient to promote metastasis to the bone and lung. In the present work, we investigated the expression and function of galectin-7 in melanoma. An analysis of datasets obtained from whole-genome profiling of human melanoma tissues revealed that galectin-7 mRNA was detected in more than 90% of biopsies of patients with nevi while its expression was more rarely found in biopsies collected from patients with malignant melanoma. This frequency, however, was likely due to the presence of normal epidermis tissues in biopsies, as shown our studies at the protein level by immunohistochemical analysis. Using the experimental melanoma B16F1 cell line, we found that melanoma cells can express galectin-7 at the primary tumor site and in lung metastasis. Moreover, we found that overexpression of galectin-7 increased the resistance of melanoma cells to apoptosis while inducing de novo egr-1 expression. Overexpression of galectin-7, however, was insufficient to modulate the growth of tumors induced by the subcutaneous injection of B16F1 cells. It also failed to modulate the dissemination of B16F1 cells to the lung.

Potential directions for drug development against galectin-7 in cancer.

BACKGROUND: Galectins are a family of proteins defined by having at least one characteristic carbohydrate recognition domain (CRD) with an affinity for beta-galactosides. Over the recent years, with a better understanding of their role in normal and pathological conditions, they have emerged as promising diagnostic and therapeutic targets in cancer. Whereas most of these studies have focused on galectin-1 and galectin-3, very little attention has been paid to galectin-7, a member of the family that has recently been associated with various forms of cancer. OBJECTIVE: We review the role of galectin-7 in cancer and examine the possible directions that could be exploited to inhibit its role in cancer on the basis of recently identified galectin ligands. CONCLUSION: Although efforts have been made to develop drugs aimed at inhibiting the cancer-promoting propensity of galectins, most of these inhibitors were specific for the CRD region of the molecule and have focused on extracellular functions of galectins. However, galectins may also be involved in protein-protein interactions, most notably in the nucleus. As galectin-7 is expressed in the cytoplasm and the nucleus in cancer cells, it will be important to investigate its nucleocytoplasmic trafficking and how putative drugs will affect its functions in cancer.