Coordinated expression of matrilysin during TPA-induced apoptosis of LNCaP cells: two parallel processes affected by TPA

Induction of tumour cell apoptosis by matrix metalloproteinase inhibitors: new tricks from a (not so) old drug

Matrix metalloproteinases (MMPs) regulate the turnover of extracellular matrix (ECM) components and play an important role in embryo development, morphogenesis and tissue remodelling, as well as in tumour invasion and metastasis. Synthetic MMP inhibitors (MMPIs) were designed to prevent tumour cell-induced changes in ECM and thereby achieve antitumour activity. Several MMPIs have entered clinical trials but the preliminary results did not meet the expectations. Recent evidence suggests that MMPs may have more diverse roles than originally believed, influencing angiogenesis, cytokine secretion, as well as tumour cell growth and survival. In particular, synthetic MMPIs may directly induce apoptosis of cancer cells via their inhibitory effect on the shedding of Fas Ligand (FasL), a transmembrane member of the TNF superfamily that kills susceptible cells through its receptor, Fas. Several types of cancers have been shown to express FasL and to shed it from their surface as a soluble form, which is significantly less potent in promoting apoptosis. MMP-7 was recently reported to catalyse this process. Conversely, inhibition of FasL-shedding by a synthetic MMPI results in apoptosis of Fas-sensitive cancer cells. More importantly, DNA-damaging anticancer agents, such as adriamycin, kill cancer cells, at least in part, by upregulating FasL. By inhibiting the proteolytic cleavage of FasL, MMPIs can potentiate the killing effect of traditional chemotherapeutic drugs. These studies therefore demonstrate a direct link between DNA-damaging chemotherapeutic drugs, the apoptosis-inducing Fas/FasL system and the proteolytic activity of MMPs and have important therapeutic implications. For example, the proteolytic activity of MMP-7, which is broadly expressed in primary and especially metastatic human malignancies, may contribute to tumour resistance to cytotoxic agents; targeting and inactivating MMP-7 may, therefore, enhance the efficacy of conventional cancer chemotherapy.

Effects of smokeless tobacco and tumor promoters on cell population growth and apoptosis of B lymphocytes infected with epstein-barr virus types 1 and 2

The effects of smokeless tobacco purified products 4-(N-methyl-N-nitrosamine)-1-3-pyridinyl)-1-butanone (NNK) and N-nitrosonornicotine (NNN), smokeless tobacco extracts (dry snuff, moist snuff, and loose leaf), and the tumor promoters 12-O-tetradecanoyl phorbol-13-acetate (TPA) and n-butyrate on cell population growth, cell death, and apoptosis were studied in B lymphocyte cell lines harboring Epstein-Barr virus (EBV) type 1 (Raji and X50-7) or type 2 (HR-1K and AG876) and in an EBV-uninfected control lymphocyte cell line (Ramos). Spontaneous apoptosis was present in all EBV-infected cell lines, but at varying levels. Spontaneous and induced apoptosis were generally greater by Student-Newman-Keuls tests in cells harboring EBV type 2 compared to EBV type 1. The greatest effects on cell population growth, cell death, and apoptosis on cells harboring lytic EBV type 1 (X50-7) was with each of the three smokeless tobacco extracts. The greatest effects on cells harboring EBV type 2 was with TPA and n-butyrate. There were no effects of smokeless tobacco extracts on the Raji cell line that harbors EBV type 1 incapable of lytic replication. Smokeless tobacco purified products, NNN and NNK, had no discernible effects. At the concentrations used in these experiments, there appears to be an EBV type-specific response to chemical induction, with greater susceptibility of lytic EBV type 1 to smokeless tobacco extracts and lytic EBV type 2 to TPA and n-butyrate. This EBV type-specific susceptibility to the effects of smokeless tobacco extracts is another phenotypic difference between EBV types. The use of smokeless tobacco products may affect B lymphocytes infected with replication-capable EBV in the oropharynx. The absence of significant effects with NNK and NNN suggests that these properties reside with other compounds present in tobacco extracts.

EGF induces the expression of matrilysin in the human prostate adenocarcinoma cell line, LNCaP

BACKGROUND

Matrix metalloproteinases (MMPs) are regulated both positively and negatively at the transcriptional level by a variety of growth factors, oncogenes, and tumor promoters. Induction of the MMP, matrilysin, by epidermal growth factor (EGF) was investigated in a human prostate cancer cell line.

METHODS

Secreted protein and messenger RNA were detected using Western and Northern methods, respectively. EGF receptor antibodies were used for neutralization of the EGF receptor to determine the role of the EGF growth factor family (EGF, transforming growth factor alpha (TGFalpha), or amphiregulin) in the basal induction of matrilysin.

RESULTS

EGF increased mRNA and secreted protein levels for the MMP matrilysin in LNCaP cells, in a concentration- and time-dependent manner. Transforming growth factor beta1 (TGFbeta1) had no inhibitory effect on the levels of mRNA or secreted protein induced by EGF in LNCaP cells. Decay of matrilysin mRNA after the addition of actinomycin D indicated that the half-life of matrilysin mRNA was not altered by EGF. Blocking with a neutralizing antibody to the EGF receptor did not alter the basal level of secreted matrilysin.

CONCLUSIONS

Exogenously added EGF increased matrilysin mRNA, perhaps at a transcriptional level. Growth factors, other than the members of the EGF family which act through the EGF receptor, may be involved in the regulation of the basal level of secreted matrilysin in LNCaP cells. Our data with LNCaP cells suggest that paracrine regulation of matrilysin expression in human prostate carcinoma cells could be via the EGF receptor.

Requirement for specific proteases in cancer cell intravasation as revealed by a novel semiquantitative PCR-based assay

Proteases are crucial for cancer metastasis, but due to lack of assays, their role in intravasation has not yet been tested. We have developed a human Alu sequence PCR-based assay to quantitate intravasated cells in an in vivo model. We demonstrated that metalloproteinases (MMPs), and most likely MMP-9, are required for intravasation by showing that marimastat, an inhibitor of MMPs, reduced intravasation by more than 90%, and that only tumor cell lines expressing MMP-9 intravasated. Cells with low surface urokinase plasminogen activator (uPA) and uPA receptor (uPAR) were also incapable of intravasation, despite the presence of high levels of MMP-9. We concluded that breaching of the vascular wall is a rate-limiting step for intravasation, and consequently for metastasis, and that cooperation between uPA/uPAR and MMP-9 is required to complete this step.

Gap junction Cx26 gene modulation by phorbol esters in benign and malignant human mammary cells

Connexin (Cx) 26, a major gap junction protein expressed in mammary epithelial cells, has been considered to be a tumor suppressor gene candidate. This study investigated the molecular mechanism of transcriptional up-regulation of Cx26 by phorbol ester (TPA) in human immortalized MCF-10 mammary epithelial cells and MDA-MB-231 mammary cancer cells. Such up-regulation was mediated through the protein kinase C pathway and could be blocked by the PKC inhibitor, calphostin C. Based on the results of the nuclear run-on assay, there was a TPA-induced increase in the rate of transcriptional initiation. We identified a TPA-induced DNase I hypersensitivity (DH) region approximately 1 kb 5' upstream of the ATG translation starting site. Sequence analysis revealed that this DH region was located in intron 1 and contained two TRE-like TGAT/ATCA elements, two 5'TTCA3' motifs and a 5'AGGAAG3' PEA3 motif. Both TRE-like elements were capable of binding AP1. TPA inducibility of this DH region was seen by the CAT reporter assay and appeared to be direction-dependent suggesting a functional cooperation between PEA3/TTCA and TRE.

Overview of matrix metalloproteinase expression in cultured human cells

The matrix metalloproteinases (MMP) have been implicated in tumor invasion and metastasis both by immunohistochemical studies and from the observation that specific metalloproteinase inhibitors block tumor invasion and metastasis. Oligonucleotide primers for thirteen MMPs (MMP-1, MMP-2, MMP-3, MMP-7, MMP-8, MMP-9, MMP-10, MMP-11, MMP-12, MMP-13, MMP-14, MMP-15, MMP-16) were optimized for use in RT-PCR. A semi-quantitative RT-PCR assay was used to determine the pattern of MMP mRNA expression in 84 normal and transformed or carcinogen transformed human cell lines and strains derived from different tissues. The results demonstrate one or more cell lines which express thirteen members of the MMP family. In addition, various oncogene transfected human fibroblast cell strains were analyzed for MMP expression. We confirm that over-expression of the H-ras oncoprotein correlates with up-regulation of MMP-9 and demonstrate that over-expression of v-sis also up-regulates MMP-9. A cell line immortalized following myc expression was found to up-regulate MMP-7, MMP-11 and MMP-13. Inappropriate expression of several MMP mRNAs was detected in breast, prostate, bone, colon and oral tumor derived cell lines. Identification of at least one cell line expressing each of thirteen MMPs and the observation of oncogene induced expression of several MMPs should facilitate analysis of the transcriptional mechanisms controlling each MMP.