Nitroreductase activation of CB1954--an alternative 'suicide' gene system.
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Animals↗
Biomedical subjects
I R Hart
Publications and source records attributed to I R Hart.
Integrin alpha5beta1-mediated adenovirus infection is enhanced by the integrin-activating antibody TS2/16.
Adenovirus internalization generally has been accepted to involve an interaction of the adenoviral penton base protein with alpha(v)beta3 and alpha(v)beta5 cell surface integrins. In this study we show that exposure of a panel of melanoma cells to the beta1-activating antibody TS2/16 rendered such cells more susceptible to adenovirus infection. This increase in adenoviral infectivity paralleled effects on cell adhesion, and both these characteristics were mediated, in part, by the alpha5beta1 integrin. These observations suggest that alpha5beta1 may act as an alternative adenovirus receptor and that integrin-activating strategies may improve the efficacy of recombinant adenoviruses as vectors for gene therapy.
Adenoviridae↗
Expression of co-stimulatory molecules by tumor cells decreases tumorigenicity but may also reduce systemic antitumor immunity.
Many tumor cells do not express co-stimulatory molecules, and this may account, in part, for their poor ability to stimulate T cells directly. One strategy to enhance immune recognition would be to express such molecules on the tumor cell. Here, we show that expression of a member of the B7 family of co-stimulatory molecules by CMT93 murine colorectal tumor or 1735 murine melanoma cells resulted in a local antitumor response in immunocompetent mice. The antitumor effect was diminished in athymic nude mice, indicating that T cells played an important part in this response. The ability of the B7-expressing tumor cells to generate systemic protective immunity was investigated by excision of tumors that developed from the initial inoculation followed by rechallenge with parental tumor cells. CMT93 is a poorly immunogenic tumor and no significant systemic immunity was elicited by the expression of B7-1 in these cells. 1735 melanoma is a mildly immunogenic tumor. Unexpectedly, the systemic immunity obtained with 1735 tumors expressing B7-1 or B7-2 was weaker than that generated by parental 1735 cells (p < 0.001, stratified logrank test), even when coexpression of interferon-gamma in the B7-1 cells produced high levels of surface MHC class I expression. These results suggest that some caution is appropriate when considering the use of these molecules in the gene therapy of cancer.
Animals↗
Identification by differential display of annexin-VI, a gene differentially expressed during melanoma progression.
To identify genes involved in the melanocyte to malignant melanoma conversion, we have applied differential display to the comparison of syngeneic murine B16F10 (metastatic melanoma) and Melan-a-immortalized melanocyte cell lines. Approximately 7000 bands were analyzed, revealing approximately 80 to be differentially displayed. Reverse Northern blotting and subsequent Northern blotting confirmed the reproducible differential expression of four transcripts. Three B16F10-specific bands encode novel genes or partially sequenced cDNAs of unknown function. One Melan-a-specific band was found to be identical to the 3' end region of the mouse Annexin VI mRNA and shown to have a reduced message expression in B16F10 relative to Melan-a. Differential expression was confirmed at the protein level with Western blotting using a rabbit polyclonal antiserum. Immunohistochemistry of human melanoma specimens with this antiserum revealed a decrease or loss of Annexin VI expression as melanomas progressed from a benign to a more malignant phenotype. Our results provide further evidence for a potential role of Annexin VI in tumor suppression.
Animals↗
The role of alpha v-integrins in tumour progression and metastasis.
Metastatic tumour spread is a pathologic process which can be described as altered cell growth associated with a series of adhesion/de-adhesion events which are coupled with regulated tissue degradation. Adhesion to, and migration through, the extracellular matrix (ECM) is necessary for the tumour invasion which is an important part of the metastatic process. Efficient proteolytic digestion of the molecules of the ECM appears to be facilitated by the localization of proteases at the cell surface-tissue interface (see also review by Stetler-Stevenson). Indeed, there is evidence from in-vitro studies to suggest that restriction of these enzymes to focal contact sites (areas of cell-substratum contact) may occur and that this sub-cellular juxtaposition of receptors and enzymes co-ordinates regulation of adhesion and proteolysis by the neoplastic cells. How such co-ordinated regulation is achieved and how this dynamic interplay is controlled during tumour development and progression are important areas of investigation.
Antigens, CD↗
Transcriptionally targeted gene therapy.
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Adjuvants, Immunologic↗
Selectin ligands on human melanoma cells.
Twelve established human melanoma lines were screened for surface expression of the carbohydrate antigens Lewisa (Lea), sialyl Lewisa (SLea), dimeric sialyl Lewisa (diSLea), sialyl LewisX (SLex) and dimeric sialyl LewisX (diSLeX). None of the lines expressed SLex, but 11/12 were positive for diSLeX and 7/12 were positive for SLea. Although both diSLeX and SLea have been reported to bind to E-selectin, none of the melanoma lines exhibited E-selectin-dependent adhesion to activated human umbilical vein endothelial cells (HUVECs). Three melanoma lines infected with a retroviral vector carrying the cDNA for the human Lewis fucosyltransferase (FucT-III) subsequently expressed SLeX at their cell surface and exhibited E-selectin-dependent adhesion to activated HUVECs. Treatment of these transduced cells with inhibitors of O-linked or N-linked protein glycosylation significantly inhibited E-selectin-mediated adhesion, though fluorescence-activated cell sorter analysis indicated no decrease in cell surface expression of SLeX, Slea or diSLeX. This suggests that the majority of SLeX/SLea-type glycans endogenously produced by human melanoma cells are not protein-associated and do not mediate E-selectin-dependent adhesion. These results support the hypothesis that E-selectin-dependent adhesion requires presentation of SLeX-type moieties on appropriate glycoproteins.
Carbohydrate Sequence↗
Expression of NM23 in human melanoma progression and metastasis.
NM23 is a putative metastasis-suppressor gene for some human cancers. Here we have studied NM23 expression during melanoma progression using Northern blotting and immunocytochemistry. There was no significant difference in the average amounts of NM23 mRNA between cell lines derived from metastatic and primary melanomas. The level of NM23 mRNA was also determined for three pairs of poorly metastatic parental (P) and their highly metastatic variant (M) cell lines; the ratios for M/P were 1.2, 0.98 and 0.80. Next we used immunocytochemistry to study NM23 protein in normal skin, benign naevi and primary and metastatic melanomas. Melanocytes in all normal skin and benign samples were positive for NM23; however most primary melanomas (7/11) were not stained by the antibody. All metastatic melanoma samples (5/5) were positively stained. Findings were similar with an antiserum reactive with both forms of NM23 (H1 and H2), and with an antibody specific for NM23-H1. No relationship was apparent between NM23 immunoreactivity in primary tumours and their aggressiveness or prognosis. Hence, in contrast to the situation described for murine melanoma, the amount of NM23 mRNA or protein in human melanoma did not correlate inversely with metastasis.
Animals↗
Biology of tumor micrometastasis.
Metastasis is the major cause of death in cancer patients. Our understanding of the molecular genetic and biologic events that contribute to tumor cell dissemination has increased considerably over the last decade. It is clear that close anatomic and temporal cooperation between cellular adhesion molecules, extracellular matrix-degrading proteases, and tumor vascularization is an essential component of the metastatic behavior of cancer cells. With this improved understanding have come novel antimetastatic therapies targeting distinct molecules and steps in the metastatic cascade. Here, we review the role of matrix-degrading enzymes, changes in cellular adhesive capacity, and tumor angiogenesis during cancer spread.
Cell Adhesion↗
Tissue specific promoters in targeting systemically delivered gene therapy.
Melanin biosynthesis is restricted to melanocytes partly as a consequence of transcriptional regulation of the mRNA coding for those enzymes involved in this biochemical pathway. Promoter sequences of these genes may be used to regulate expression of complementary DNA coding for therapeutic genes so as to provide transcriptional targeting. As a model system we have used the 5'-flanking sequences of the murine tyrosinase or tyrosinase-related protein 1 (TRP-1) genes to show that such transcriptional targeting can be accomplished both in vitro and in vivo. Using interleukin-2 (IL-2) as an example of an immunostimulatory gene and herpes simplex virus thymidine kinase (HSVTK), as an example of a prodrug-activating gene we have shown, in murine model systems, that marked antitumour effects can be achieved by targeted gene therapy approaches. Because other tumor types produce particular proteins as a consequence of specific transcription it is possible that this approach may provide a way of targeting therapeutic genes to various cancers.
Animals↗
Investigation of alternative prodrugs for use with E. coli nitroreductase in 'suicide gene' approaches to cancer therapy.
The most commonly employed 'suicide' gene/prodrug system used in cancer gene therapy is the herpes simplex virus thymidine kinase (HSVtk)/ganciclovir system. We have examined the efficacy of an alternative approach utilising the E. coli nitroreductase B enzyme with CB1954 and a variety of other prodrugs. V79 cells transfected with a nitroreductase expression vector were up to 770-fold more sensitive to CB1954 than control non-expressing cells. In general other prodrugs which were found by HPLC to act as substrates for purified E. coli nitroreductase also exhibited increased cytotoxicity against the nitroreductase-expressing cells, although this correlation was not absolute. In particular nitrofurazone (97-fold) and additional aromatic nitro-compounds (nine- to 50-fold) showed a large differential whereas the quinones and the antimetabolite, B-FU, were less effective (< three-fold). The results support the possibility of using nitroreductase and CB1954 for 'suicide gene' therapy and in addition suggest that alternative prodrugs, such as nitrofurazone, warrant further investigation in this novel approach.
Animals↗
Management decisions in subclinical thyroid disease.
Subclinical hypo- and hyperthyroidism are common, well-defined conditions that often progress to overt disease. In addition, there have been concerns that the subclinical states may contribute to hyperlipidemia, cardiac dysfunction, and osteoporosis. The author discusses the issues and outlines a rational approach to management that identifies patients who will benefit from treatment.
Aged↗
Level of expression of E-cadherin mRNA in colorectal cancer correlates with clinical outcome.
A series of colorectal carcinomas (n = 49) resected from patients with known clinical outcomes were analysed for E-cadherin expression using in situ hybridisation to measure mRNA. Patients surviving 5 years or longer (n = 31) exhibited significantly higher levels of E-cadherin mRNA than those surviving less than 5 years (n = 18, P = 0.003). These preliminary results from this small sample suggest that E-cadherin expression may be a useful prognostic marker in colorectal cancer patients.
Cadherins↗
Gene therapy for lung cancer.
BACKGROUND: The techniques of molecular genetics are being applied in many areas of oncology and have been spectacularly successful in elucidating the pathogenesis of cancer. Attempts are now being made to harness this knowledge for therapeutic use. Lung cancers are common solid tumours of complex aetiology and represent a major challenge for gene therapy. CURRENT INVESTIGATIONS: The approaches presently under investigation include the correction of acquired genetic abnormalities, such as mutation of p53 and activation of the ras oncogene, immunotherapy, enhancement of host resistance to cytotoxic insult, and genetic activation of prodrugs by tissue-specific promoters. A variety of vector systems arc available, including liposomes, replication-defective retroviruses and adenoviruses. Local, regional and systemic routes of administration are being studied, and it seems likely that a combination of these approaches will be needed if such treatments are to become generally available.
Antineoplastic Agents↗
Targeted gene therapy.
Melanin biosynthesis is limited to melanocytes partly as a consequence of transcriptional regulation of the enzymes involved in this pathway. Promoter sequences of these enzyme genes may be utilised to drive expression of complementary DNA coding for therapeutic genes so as to provide transcriptional targeting. We have used the 5'-flanking sequences of the murine tyrosinase or tyrosinase-related protein 1 (TRP-1) genes to show that such transcriptional targeting can be achieved both in vitro and in vivo. Using IL-2 as an example of an immunostimulatory gene and Herpes Simplex Virus thymidine kinase (HSVtk) as an example of a prodrug-activating gene we have shown, in murine model systems, that substantial anti-tumour effects can be achieved by targeted gene therapy approaches. The stage now is set for initial clinical evaluations in human patients.
Gene Targeting↗
Effects of modulators of tyrosinase activity on expression of murine interleukin-2 cDNA driven by the tyrosinase promoter.
Sequence analysis of the promoter region of the murine tyrosinase gene identified various consensus motifs including AP2 sites, cAMP and TPA response elements (CREs/TREs) and retinoic acid response element (RARE) half-sites. By linking two different promoter lengths (2.5 kb or 769 bp) to murine interleukin-2 (IL-2) cDNA we have used IL-2 production by transduced B16 cells to monitor response to inducing agents capable of acting through these elements. Aminophylline or theophylline (0.1-2 mM) added to the culture medium of transfected B16, but not 3T3, cells, increased IL-2 secretion significantly (P > 0.05) in a dose-dependent fashion. This response was comparable in cells transfected with either the full length or the truncated promoter. Therefore, the cAMP responsiveness of the tyrosinase promoter probably is mediated by CREs and not AP2 sites, since the truncated promoter contains the former but not the latter regions. Retinoic acid at various concentrations (0.1-1 microM) evoked a standard increase in IL-2 production. Responses were similar for both promoter constructs, which suggests either that each RARE half-site can confer the full retinoic acid response, or that retinoic acid is mediating its effect through pathways independent of the RARE sites. TPA (2 nM-2 microM) had no effect on IL-2 production. These results demonstrate that the tyrosinase promoter can be induced by certain pharmacological agents and raise the possibility that administration of such substances may enhance expression of therapeutic genes controlled by this promoter.
3T3 Cells↗
Alpha v beta 1 is a receptor for vitronectin and fibrinogen, and acts with alpha 5 beta 1 to mediate spreading on fibronectin.
We have shown previously that VUP was the only line out of ten human melanoma lines that failed to express the vitronectin receptor alpha v beta 3, but instead expressed alpha v beta 1. Levels of alpha v beta 1 expression were low on parental VUP cells so that iterative sorting by FACS, using an anti-alpha v antibody (13C2), was utilised to derive sublines with 8- to 10-fold higher amounts of cell surface alpha v beta 1. There was little difference between low (V-) and high (V+) alpha v beta 1-expressing sublines with regard to adherence to collagen type I, collagen type IV or laminin substrata. However, adherence to vitronectin and fibrinogen correlated closely with alpha v beta 1 expression (35-42% adhesion for V(+) lines versus 6-8% adhesion for V- lines on vitronectin, for example). Utilising a high alpha v beta 1-expressing subline (V + B2) we have shown that binding to vitronectin and fibrinogen was inhibited specifically by function-blocking antibodies to alpha v (17E6 and 14D9) and beta 1 (A11B2). V(+) sublines spread more compared with V(-) sublines on both vitronectin and fibronectin. However, neither alpha 5- nor alpha v-blocking antibodies had any effect on attachment or spreading of V + B2 on fibronectin whereas the combination of alpha 5 (PID6)- and alpha v(17E6)-blocking antibodies abrogated binding to fibronectin almost completely. This is the first report of an alpha v beta 1 integrin able to recognize vitronectin and fibrinogen, and also cooperate with alpha 5 beta 1 to mediate attachment to and spreading on fibronectin.
Antibodies↗
Systemic gene therapy of murine melanoma using tissue specific expression of the HSVtk gene involves an immune component.
Previously we have demonstrated safe and effective transfer of the HSVtk cytotoxic gene to primary murine melanoma tumors by direct injection of plasmid and retroviral vectors in which the HSVtk gene is driven by the tissue-specific tyrosinase promoter. However, for general clinical application such forms of therapy should, ideally, be effective against disseminated metastases. We report here that the number of recently established lung metastases of B16 melanoma in C57BL mice treated with ganciclovir is reduced compared to controls after multiple i.v. administrations of high titer retroviral supernatant encoding the HSVtk gene, but not after administration of liposome-complexed plasmid DNA. Using polymerase chain reaction analysis, integration of the provirus was observed in metastasis-bearing lungs (4 of 6 mice) and in the spleens of some ganciclovir-treated animals (2 of 6 mice) but not in the testes, brain, heart, liver, or kidney. The reduction in the number of experimental metastases in C57BL mice exceeded the anticipated extent of transduction of tumor cells, which is indicative of a marked bystander effect. This magnitude of reduction was not observed in immunodeficient athymic mice, suggesting that the immune system plays some part in the bystander effect. In support of these data, we show that, whereas the parental tumor cells are only poorly immunogenic, an effective antitumor immune response is generated following the killing of neoplastic cells in vivo as a result of treatment with ganciclovir. These effects may be responsible for augmenting the efficacy of retroviral infection. The combination of local cell killing by the HSVtk/ganciclovir system and the induction of antitumor immunity suggests new opportunities for the design of vectors for the gene therapy of cancer.
Animals↗