Production and Characterization of a Tumor-Specific Monoclonal Antibody Act19 Recognizing an Epitope Distinctive from Sialosyl-Tn on the TAG72 Antigen

Aims

A murine monoclonal antibody ACT19 directed at the TAG72 tumor-associated antigen, which was originally defined by the B72.3 antibody, was established.

Methods

This was done by immunizing mice with the bovine mucin followed by the selection of hybridomas secreting antibodies with the desired specificity. In order to better characterize this antibody, its immunoreactivity was compared to that of the B72.3 antibody.

Results

The data showed that the ACT19 antibody bound specifically to the TAG72 antigen as the B72.3 antibody did. However, there were some differences between ACT19 and B72.3. Firstly, the immunoreactivity of ACT19 for the bovine mucin was lower than that of B72.3. Secondly, the immunoreactivity of ACT19 for the TAG72 antigen was not inhibited by N-acetylgalactosamine, nor was that of B72.3. Thirdly, ACT19 did not compete the binding reactivity of B72.3 for the TAG72 antigen. This suggests that the epitope defined by ACT19 is different from the sialosyl-Tn epitope recognized by B72.3. Immunoperoxidase staining of various tumors, normal and embryonic tissues for ACT19 was carried out. For the various tumors, only adenocarcinomas from the colon and stomach showed remarkable positivity. All the normal tissues were negative, except for weak positivity involving the zona reticularis of the adrenal cortex, and intestinal goblet cells. Embryonic tissues showed a wide spectrum of positivity with staining of the small and large intestine, stomach and renal tubules.

Conclusions

The ACT19 antibody appears to be a useful marker for colon and stomach cancers, and this additional anti-TAG72 antibody may be useful in conjunction with the B72.3 antibody in pathology and clinical application.

Regression of engineered myeloma cells secreting interferon-gamma-inducing factor is mediated by both CD4(+)/CD8(+) T and natural killer cells

IL-18 is a novel cytokine that stimulates T and NK cell activity and has potent antitumor effects. In this study, a mouse IL-18 gene was transfected into the mouse myeloma cell line J558. Our data demonstrated that (i) inoculation of 0.5x10(6) engineered tumor cells J558/IL-18 into syngeneic mice induced a Th1 dominant immune response and resulted in tumor regression in all 8/8 mice; (ii) the IL-18 antitumor effect was significantly decreased in mice depleted of either the CD4(+), or CD8(+), or NK cell subset, respectively but was completely abrogated in mice depleted of both CD4(+) and CD8(+) T cells; (iii) in vivo neutralization of IFN-gamma was accompanied by the growth of J558/IL-18 tumor in all the mice; and (iv) the J558/IL-18 tumor regression further induced protective immunity against a subsequent challenge by the parental J558 tumor, which is mediated by CD8(+) T cells as examined in the cytotoxicity assay in vitro and in the animal study in vivo. Taken together, our findings indicate that: (i) IL-18 can induce antitumor immune responses mediated by both CD4(+)/CD8(+) T cells and NK cells; and (ii) it is associated with IFN-gamma production. This study thus highlights the potential utility of IL-18 as an antitumor agent, a role that it can fulfil alone or in combination with other immunomodulatory cytokines such as IL-12.

Efficient antitumor immunity derived from maturation of dendritic cells that had phagocytosed apoptotic/necrotic tumor cells

Dendritic cells (DCs) that acquired antigen from apoptotic tumor cells are able to induce major histocompatibility complex (MHC) class I-restricted cytotoxic T lymphocytes and antitumor immunity. In the present study, we investigated the efficiency of antitumor immunity derived from DCs that had phagocytosed apoptotic/necrotic BL6-10 melanoma cells compared with that of DCs pulsed with the tumor mTRP2 peptide. Our data showed that phagocytosis of apoptotic/necrotic tumor cells resulted in maturation of DCs with up-regulated expression of proinflammatory cytokines [interleukin (IL)-1beta, IL-6, tumor necrosis factor-alpha, interferon-gamma and granulocyte-macrophage colony-stimulating factor], chemokines (MIP-1alpha, MIP-1beta and MIP-2), the CC chemokine receptor CCR7 and the cell surface molecules (MHC class II, CD11b, CD40 and CD86), and down-regulated expression of the CC chemokine receptors CCR2 and CCR5. These mature DCs displayed enhanced migration toward the CC chemokine MIP-3beta in a chemotaxis assay in vitro and to the regional lymph nodes in an animal model in vivo. Our data also showed that vaccination with DCs that had phagocytosed apoptotic/necrotic BL6-10 cells was able to (i) more strongly stimulate allogeneic T-cell proliferation in vitro, (ii) induce an in vivo Th1-type immune response leading to more efficient tumor-specific cytotoxic CD8(+) T-cell-mediated immunity and (iii) eradicate lung metastases in all 6 vaccinated mice compared with mice vaccinated with DCs pulsed with the tumor mTRP2 peptide, in which lung metastases were reduced (mean number of 16 per mouse) but not completely eradicated. Therefore, DCs that had phagocytosed apoptotic/necrotic tumor cells appear to offer new strategies in DC cancer vaccines.

Lymphotactin expression by engineered myeloma cells drives tumor regression: mediation by CD4+ and CD8+ T cells and neutrophils expressing XCR1 receptor

The C chemokine lymphotactin has been characterized as a T cell chemoattractant both in vitro and in vivo. To determine whether lymphotactin expression within tumors could influence tumor growth, we transfected an expression vector for lymphotactin into SP2/0 myeloma cells and tested their ability to form tumors in BALB/c and nude mice. Transfection did not alter cell growth in vitro. Whereas SP2/0 cells gave rise to a 100% tumor incidence, lymphotactin-expressing SP2/0-Lptn tumors invariably regressed in BALB/c mice and became infiltrated with CD4(+) and CD8(+) T cells and neutrophils. Regression of the SP2/0-Lptn tumors was associated with a type 1 cytokine response and dependent on both CD4(+) and CD8(+) T cells, but not NK cells. Both SP2/0 and SP2/0-Lptn tumors grew in nude mice, but growth of the latter tumors was retarded and associated with heavy neutrophil responses; this retardation of SP2/0-Lptn tumor growth was reversed by neutrophil depletion of the mice. Our data also indicate that mouse neutrophils express the lymphotactin receptor XCR1 and that lymphotactin specifically chemoattracts these cells in vitro. Thus, lymphotactin has natural adjuvant activities that may augment antitumor responses via effects on both T cells and neutrophils and thereby could be important in gene transfer immunotherapies for some cancers.

Cancer gene therapy by adenovirus-mediated gene transfer

Cancer arises as a direct result of genetic mutations. It therefore stands to reason that cancer should be well suited for the correction through gene therapy. Recent advances in the understanding of the molecular pathogenesis of cancer and the rapid development of recombinant DNA technology have made cancer gene therapy feasible in the clinical setting. The current efforts for cancer gene therapy mainly focus on immunogene therapy, chemogene therapy, restoration of tumor suppressor gene function, and oncolytic virus therapy. Central to all these therapies is the development of efficient vectors for gene delivery--this remains a work in progress. These vectors can be classified as viral and non-viral vectors. This paper will concentrate on viral vectors because of their practical advantages over non-viral vectors. Of the viral vectors, by far the most important are the human adenoviruses as is reflected by the enormous data and literature accumulated by studies relating to animal tumor models and clinical trials. In this review, we examine the recent progress in adenovirus-mediated cancer gene therapy with regard to cytokine gene, tumor suppressor gene, chemogene, and oncolytic adenovirus. We also discuss the current limitations of the adenoviral vector system and how they may be circumvented in future developments relating to targeted gene delivery.

Adenovirus-mediated p16INK4 gene transfer significantly suppresses human breast cancer growth

The p16INK4 tumor suppressor gene encodes a protein that inhibits cyclin-dependent kinase 4, and its homologous deletion is common in human breast cancer. p16INK4 gene transfer has been reported to be efficacious in inducing growth inhibition of various human tumors such as brain, lung, prostate, and esophageal cancers. However, the efficiency of the p16INK4 gene with regard to growth inhibition of human breast cancer has not been studied extensively. To examine its tumor-suppressive function and its potential in breast cancer gene therapy, the wild-type p16INK4 gene was expressed in an adenovirus-mediated gene delivery system and introduced into breast cancer cell lines that do not express p16INK4 protein. Expression of the introduced p16INK4 blocked tumor cell entry into the S phase of the cell cycle, induced tumor cell apoptosis, and inhibited tumor cell proliferation both in vitro and in vivo. These results strongly suggest that p16INK4 is a tumor suppressor gene and suggest that it has potential utility in breast cancer gene therapy.

Combinational immunotherapy for established tumors with engineered tumor vaccines and adenovirus-mediated gene transfer

There are currently extensive studies relating to cancer vaccines using tumor cells engineered to express immunogenes and cancer gene therapy using adenovirus (AdV)-mediated gene transfer. In this study, a mouse tumor cell line, VKCK, was cotransfected with genes coding for tumor necrosis factor-alpha (TNF-alpha) and costimulatory B7-1 molecule to enhance immunogenicity. The transfectant cell line VKCK-TNF-alpha/B7-1 showed reduced tumorigenicity and tumor regression. Its inoculation further induced protective immunity; both CD4+ and CD8+ T cells were involved in the induction phase, whereas only CD8+ T cells mediated the effector phase. Susceptible mice bearing VKCK tumors developed a T helper type 2-dominant response, whereas resistant mice with VKCK-TNF-alpha/B7-1 tumor regression developed a T helper type 1-dominant response to VKCK, indicating that the tumor regression was related to a shift in the cytokine profile of the host from type 2 to type 1. Vaccination of VKCK-TNF-alpha/B7-1 cells inhibited tumor formation derived from a single dose of 3 x 10(6) VKCK cells and eradicated 3-day tumors but not 10-day tumors. AdV-mediated TNF-alpha gene transfer by intratumoral injection of AdV-TNF-alpha significantly inhibited tumor growth but failed to eradicate any well-established tumors. However, combinational immunotherapy with vaccination of VKCK-TNF-alpha/B7-1 cells and AdV-mediated TNF-alpha gene transfer not only significantly inhibited tumor growth but also eradicated 10-day VKCK tumors in three of eight mice. Therefore, the present study may be useful not only in understanding the mechanisms responsible for an efficient antitumoral immunity, but also in establishing a more effective immunotherapeutic approach for cancer patients.

Regression of engineered tumor cells secreting cytokines is related to a shift in host cytokine profile from type 2 to type 1

The precise role of the endogenous immune response in modulating cancer development remains unclear. In this study, three mouse tumor cell lines were used to elucidate the immune mechanisms for tumor regression versus tumor growth. These cell lines were (1) the poorly immunogenic VKCK cell line and (2) its two derived cell lines VKCK/RM4-tumor necrosis factor-alpha (TNF-alpha) and VKCK/RM4-interferon-gamma (IFN-gamma) engineered to secrete TNF-alpha and IFN-gamma, respectively. Our data showed that VKCK tumors grew aggressively in syngeneic BALB/c mice, and vaccination of irradiated VKCK cells failed to protect the mice from a subsequent challenge with the same tumor. In contrast, engineered VKCK tumor cells lost their tumorigenicity, and vaccination of engineered VKCK cells induced a protective immunity against VKCK cells that was mediated with VKCK-specific CD8+T cells. Susceptible mice developed a Th2-dominant response, whereas resistant mice developed a Th1-dominant response to VKCK. The T cell proliferative response and cytolytic activity against VKCK developed in both resistant and susceptible mice, but in the susceptible mice, these responses were much weaker compared with those in the resistant mice. Our results indicate that regression of tumor cells engineered to secrete cytokines TNF-alpha and IFN-gamma is related to a shift from a host type 2 to a type 1 cytokine profile. Our results further suggest that the failure of unmodified VKCK to generate efficacious T cells is not due to an inability to recognize tumor antigens but, rather, to the nature and magnitude of the antitumor immune response that develops. A better understanding of the mechanisms by which tumor cells modulate the host immune system may result in newer approaches for manipulating host-tumor interactions that favor the development of a protective antitumor immune response.

Adenoviral transfer of xenogeneic MHC class I gene results in loss of tumorigenicity and inhibition of tumor growth

The immune system confers protection against a variety of pathogens and contributes to the destruction of neoplastic cells. Foreign major histocompatibility complex (MHC) protein serves as a potent stimulus to the immune system. In this report, a mouse H-2Kb gene was introduced into two poorly immunogenic tumor cell lines, a mouse colonic carcinoma cell line, MCA-26 (H-2Kd), and a rat mammalian carcinoma cell line, LN-4, in an effort to stimulate tumor rejection. Our results showed that the expression of xenogeneic MHC class I antigen completely abolished the LN-4 tumorigenicity in rats, whereas the expression of allogeneic MHC class I antigen only partially reduced the MCA-26 tumorigenicity in mice. Rats with tumor regression of LN-4/H-2Kb developed a T helper type 1-dominant response, whereas rats with LN-4 tumor growth developed a T helper type 2-dominant response. The immunized rats that experienced LN-4/H-2Kb tumor regression further developed protective immunity against a subsequent challenge of LN-4 cells. This protective immunity was mediated by the LN-4 tumor-specific cellular immune response against both the transduced and the parental LN-4 cells. Recombinant adenoviral vectors are highly efficient at in vitro and in vivo gene delivery. The LN4 cells transfected with the recombinant adenovirus AdV-H-2Kb in vitro expressed the cell surface H-2Kb molecule by fluorescence-activated cell sorter analysis. Adenovirus-mediated H-2Kb gene transfer in vivo can further significantly inhibit pre-established LN-4 tumors. Those rats with complete tumor regression further developed protective immunity against the subsequent challenge of a parental LN-4 tumor. Therefore, our study indicates that the adenovirus-mediated transfer of xenogeneic MHC class I gene may be an effective alternative to the current protocol of cancer gene therapy in which the allogeneic MHC class I gene is used.

Enzyme-linked immunosorbent assay-based selection and optimization of elution buffer for TAG72-affinity chromatography

An enzyme-linked immunosorbent assay (ELISA)-elution assay was developed to screen a large variety of elution buffers for selection of a suitable one for purification of the fusion protein FV/TNF-alpha by affinity chromatography. Various commonly used buffer systems utilizing widely differing conditions such as extreme pH, denaturants, chaotropic ions and polarity reducing reagents were investigated. Ammonia solution (1 M, pH 11.5) proved to exert the most suitable influence on dissociation of the FV/TNF-alpha/TAG72 complex while having a minimal protein denaturing effect on FV/TNF-alpha. The total yield of purified FV/TNF-alpha using the TAG72-affinity column with this elution system was 300-fold higher than that using the common elution buffer, 0.1 M glycine, 0.5 M NaCl, pH 2.7. Our study indicates that the ELISA-elution assay will be most useful in the selection of suitable elution buffers for affinity chromatography.

Asplenia as a cause of sudden unexpected death in childhood

Sudden unexpected death in childhood is rare. The commonest causes of such deaths are a result of fulminating infections of the respiratory or nervous systems. Other causes include unsuspected congenital abnormalities of the heart, acute metabolic disorders, and rarities such as internal hemorrhages and pulmonary thrombosis. Recognition of children with congenital asplenia who are otherwise normal but have an increased susceptibility to overwhelming sepsis is extremely difficult. We reviewed 1763 autopsy files from our institution over 5 years (1990-1995), of which 293 were classified as pediatric cases. The vast majority of the cases were stillbirths and deaths within the first year of life as a result of complex congenital anomalies. Four cases of asplenia were identified in our entire series, 3 of which were of the congenital syndromal variety and 1 of which was a case of isolated sporadic congenital asplenia. All 4 cases of asplenia were analyzed in detail with respect to autopsy findings and cause of death. Severe complex cardiac malformations were present in the congenital syndromal asplenia patients; these other malformations contributed significantly to their death. In this report, we discuss in detail the autopsy findings in a previously healthy 4-year-old girl who presented with a brief 8-hour history of being unwell and died within 4 hours of admission into the hospital. She had sporadic, isolated congenital asplenia complicated by high-grade type 6B pneumococcemia and acute bilateral adrenal hemorrhage (Waterhouse-Friderichsen syndrome). Previously healthy children who clinically deteriorate very rapidly should have a blood smear done as part of their clinical workup. The detection of Howell-Jolly bodies on a peripheral blood smear can be an indicator of asplenia, and this diagnosis can be confirmed by medical imaging of the abdomen. Such steps may aid in the aggressive management of isolated congenital asplenia and thereby avert untimely death.

Adenovirus-mediated TNF-alpha gene transfer induces significant tumor regression in mice

Recombinant adenovirus vectors are highly efficient at in vitro and in vivo gene delivery. The in vitro infection of a mouse colon adenocarcinoma cell line MCA-26 with the adenovirus AdV-LacZ can reach a maximal 75% of infectivity at an MOI of 1000. Intratumoral injection of AdV-LacZ (2X10(9) pfu) resulted in substantial gene transfer in nearly 70% of MCA-26 tumors. After the in vitro infection of AdV-TNF-alpha, infected MCA-26 cells showed significant secretion of TNF-alpha (45 ng/ml/10(6) cells) in tissue culture. The secretion peaks at day 2 and is diminished at day 4 following the viral infection. Infected MCA-26 tumor cells secreting TNF-alpha significantly reduced their tumorigenicity in syngeneic BALB/c mice. In mice bearing small tumors, intratumoral injection of 2X10(9) pfu of AdV-TNF-alpha virus with a repeated booster treatment resulted in complete regression of three tumors and significant diminution of the other two with a mean tumor-weight of 0.16 g; this is in contrast to 0.85 and 1.62 g for tumors injected with the control AdV-pLpA and PBS respectively (p < 0.01). Mice with complete tumor regression further developed protective immunity against the second challenge of MCA-26 inoculation. In mice bearing large tumors, this treatment also caused significant inhibition of tumor growth with a mean tumor weight of 0.65 g vis-a-vis 3.05 g for tumors injected with the control AdV-pLpA. On the contrary, in mice bearing large tumors, the treatment of tumors with pCI-TNF-alpha delivered by the gene gun did not induce significant tumor inhibition. These results indicate that the adenoviral delivery of TNF-alpha gene is more efficient than the particle-mediated gene gun device, and that adenovirus-mediated cytokine gene therapy may be a useful approach in the clinical management of human solid tumors.

Intratumoral vaccination of adenoviruses expressing fusion protein RM4/tumor necrosis factor (TNF)-alpha induces significant tumor regression

Recombinant adenovirus (AdV) vectors are highly efficient at in vitro and in vivo gene delivery. VKCK is a murine myeloma cell line expressing the light chain of the fusion protein RM4/tumor necrosis factor (TNF)-alpha. The in vitro transfection of VKCK cells with the AdV AdV5LacZ, which contains the marker gene beta-galactosidase, can reach a maximal 75% at a multiplicity of infection of 1000. Intratumoral injections of AdV5LacZ (2 x 10(9) plaque-forming units) resulted in substantial gene transfer in nearly 50% of VKCK tumors. The AdV pLpA/M4-TNF-alpha, which contains a fused gene M4-TNF-alpha that codes for the heavy chain of fusion protein RM4/TNF-alpha, was constructed. After the in vitro transfection of pLpA/M4-TNF-alpha at a multiplicity of infection of 1000, transfected VKCK cells showed significant secretion of RM4/TNF-alpha (36 ng/mL/10(6) cells) containing the functional TNF-alpha moiety in tissue culture. The secretion peaks at day 3 and is diminished at day 6 following the viral infection. These transfected VKCK cells also became more immunogenic with enhanced expression of major histocompatibility complex class I antigen. Intratumoral injections of 2 x 10(9) plaque-forming units of pLpA/M4-TNF-alpha virus with a repeated booster resulted in significant VKCK tumor regression in immune-competent mice, but not in athymic nude mice with a mean tumor weight of 0.07 g that were compared with 1.58 g and 1.70 g for tumors injected with AdV5LacZ and phosphate-buffered saline, respectively (P < .01). The tumor regression also results in protective immunity against a second challenge with parental tumor cells, which is mainly mediated by VKCK tumor-specific CD8+ T cells. These results indicate that AdV-mediated cytokine gene therapy may be a useful approach in the clinical management of solid human tumors.

Cytotoxic CD4+ T cells associated with the expression of major histocompatibility complex class II antigen of mouse myeloma cells secreting interferon-gamma are cytolytic in vitro and tumoricidal in vivo

Vaccination of mouse myeloma V(K)C(K)-gamma (I) cells secreting interferon (IFN)-gamma and expressing enhanced major histocompatibility complex (MHC) class I antigen (Ag) resulted in protective immunity that was mainly mediated by CD8+ T cells. V(K)C(K)-gamma (I/II) cells expressing both enhanced MHC class I and class II Ags were isolated from V(K)C(K)-gamma (I) cells. These V(K)C(K)-gamma (I/II) cells were used to study the relationship between IFN-gamma secretion of tumor cells, its tumorigenicity, and its induced immunity, as well as to evaluate the cellular immunocomponents mediating this immunity. Our animal studies showed that IFN-gamma secretion by V(K)C(K)-gamma (I/II) cells curtailed its tumorigenicity in syngeneic BALB/c mice and further induced protective immunity against a subsequent graft of parental V(K)C(K) tumor. This immunity is mediated by both CD4+ and CD8+ T cells. The activation of CD4+ T cells is associated with enhanced expression of MHC class II Ag of V(K)C(K)-gamma (I/II) cells. These CD4+ T cells are tumor specific and cytolytic in an MHC-restricted fashion in vitro, and are tumoricidal in a T-cell adoptive transfer experiment in vivo. Our data thus demonstrate that vaccination of genetically modified tumor cells secreting IFN-gamma may provide beneficial antitumor effects by inducing both cytolytic CD4+ and CD8+ cytotoxic T lymphocytes, provided that these tumor cells express both enhanced MHC class I and class II Ags.

One hundred seventy-fold increase in excretion of an FV fragment-tumor necrosis factor alpha fusion protein (sFV/TNF-alpha) from Escherichia coli caused by the synergistic effects of glycine and triton X-100

To target tumor necrosis factor alpha (TNF-alpha) to tumor cells, recombinant DNA techniques were used to construct and express the fused gene VKLVH-TNF-alpha, which encodes the secreted form of single-chain fusion protein sFV/TNF-alpha in Escherichia coli. sFV/TNF-alpha was secreted into the culture medium and purified by affinity chromatography. The production of the fusion protein in the culture medium under the optimal conditions of 30 degrees C and 37 micromol of isopropyl-beta-D-thiogalactopyranoside (IPTG) per liter was 16- and 5-fold higher than that under the standard conditions of 37 degrees C and 1 mmol of IPTG per liter. Fusion protein excretion into culture medium with 2% glycine, 1% Triton X-100, or both of these two chemicals was either 14-, 38-, or 170-fold higher, respectively than that without the two chemicals. The final yield of sFV/TNF-alpha was estimated to be 50 mg/liter. The loss of integrity of the cellular membrane may be a potential mechanism for enhancement of fusion protein production and excretion by treatment with glycine and Triton X-100. This study thus provides a practical, large-scale method for more efficient production of the heterologous fusion protein sFV/TNF-alpha in E. coli by using glycine and Triton X-100.

Elevated expression of the cdc25A protein phosphatase in colon cancer

The nuclear protein phosphatase cdc25A has been postulated to be a protooncogene. The total nuclear phosphotyrosyl protein phosphatase (PTP) activity and the expression of cdc25A were compared in normal and cancerous colon epithelial tissue. Nuclei derived from normal mucosal epithelium and tumors were analyzed for phosphotyrosyl protein phosphatase activity using the malachite green assay and a synthetic phosphotyrosyl peptide based on the sequence of cdc2, a known cdc25A phosphotyrosyl protein substrate. Tumorigenesis resulted in elevated nuclear PTP activity (343.0 +/- 37.0% of normal epithelial PTP activity) in 52% (29 of 56) of colon tumors. In all cases elevated nuclear PTP activity correlated with an increase in the expression of cdc25A. The changes in PTP activity observed were not due to any increase in the rate of growth of the colonic mucosa as no corresponding changes occurred with PTP activity under conditions of rapid mucosal growth.

Genetic engineering of a recombinant fusion possessing anti-tumor F(ab')2 and tumor necrosis factor

The construction, synthesis and expression of a genetically engineered bifunctional antibody/cytokine fusion protein is described. In order to target alpha-tumor necrosis factor (TNF) to tumor cells, recombinant antibody techniques were used to construct an RM4/TNF fusion protein containing the chimeric anti-tumor F(ab')2 (RM4) as well as the TNF moiety. The recombinant cDNA of human TNF was linked to the 3' end of the chimeric heavy-chain gene fragment (M4) containing the VH, the CH1 and the hinge region to form the fused heavy-chain gene fragment M4-TNF. Transfection of the M4-TNF gene fragment into a VKCK cell line producing the chimeric light-chain of the same antibody allowed the transfectant secreting the bifunctional fusion protein RM4/TNF. The RM4/TNF was purified by affinity chromatography. Our data showed that RM4/TNF retained the TAG72 antigen-binding reactivity as well as TNF activity as measured by ELISA, Western blotting, flow cytometry analysis, immunohistochemistry and cytotoxicity assays using the human colon cancer cell line LS174T. Therefore, the bifunctional fusion protein RM4/TNF may prove useful in targeting the biological effects of TNF to tumor cells, and in this way stimulate the immune destruction of tumor cells.

Establishment of a rat colonic carcinoma model for study of immunoreagents against the human tumor-associated TAG72 antigen

TAG72 originally defined by the mouse B72.3 antibody is a mucin-like, human tumor-associated antigen present in more than 85% of human colonic adenocarcinomas. Establishment of a tumor model expressing the TAG72 antigen in immunocompetent animals would be of great benefit in evaluating the therapeutic efficacy and studying anti-tumor immune mechanisms of anti-TAG72 immunoreagents. In this study, we screened 6 animal tumor cell lines including 3 derived from mouse colonic adenocarcinomas (MCR-26, MCR-38-LD and CA-51), 1 from mouse ovarian adenocarcinoma (MOT), 1 from rat colonic adenocarcinoma LMCR, and 1 from rat mammalial adenocarcinoma (R3230AB) for TAG72 expression by using the B72.3 antibody. Immunohistochemistry disclosed significant amounts of TAG72-expression in the dimethylhydrazine-induced BDIX rat colonic adenocarcinoma LMCR. The rat TAG72 antigen purified from rat LMCR tumors showed strong immunoreactivity for the B72.3 antibody in ELISA analysis and displayed a smear band of high molecular weight in Western blotting, which is similar to the human TAG72 antigen purified from human LS174T colonic adenocarcinoma. In addition, the iodinated B72.3 antibody was able to localize LMCR tumor in BDIX rats. Therefore, this rat LMCR model should be useful in studying human colonic cancer, especially in evaluating the therapeutic efficacy of anti-TAG72 immunoreagents such as the recombinant fusion proteins possessing the anti-TAG72 antibody fragment and the cytokine moiety.

Identification of a decapeptide with the binding reactivity for tumor-associated TAG72 antigen from a phage displayed library

Peptide ligands for tumor-associated TAG72 antigen were identified by screening a large, diverse decapeptide library expressed on the surface of filamentous phages. Fifty-eight clones of phages were selected from the eluates after the third round of biopanning and their DNA inserts were sequenced. A dominant decapeptide HYVSIELPDH (14/58) was found with the binding reactivity for TAG72 antigen in the TAG72-binding ELISA and Western dot blotting. It also showed a preferential binding to colonic adenocarcinomatous cells expressing the TAG72 antigen in the histochemical study. Therefore, this anti-TAG72 decapeptide may be useful in serving as the starting point with regard to further designing peptidomimetics for potential pharmaceuticals.

Repair and function of synovium after arthroscopic synovectomy of the dorsal compartment of the equine antebrachiocarpal joint

The reparative ability of equine synovium was determined by gross, histological, and ultrastructural examination. The functional potential of the synovium was estimated by examination of synovial cell organelles with transmission electron microscopy. Results from rested and exercised horses were compared to determine the effect of exercise on synovial healing. The response of synovectomized joint to exercise was evaluated with a standardized lameness examination and by gross, histological, and histochemical observations of the articular cartilage. A 7-mm diameter motorized synovial resector was used to perform a subtotal synovectomy in 1 antebrachiocarpal joint of each of 8 horses; the contralateral joint served as a control. After 2 months rest, four randomly selected horses were rigorously exercised for the remainder of the study; the other four horses continued paddock rest. Lameness examinations and synovial fluid analyses were conducted at 0, 2, 30, 60, and 120 days. Synovium and articular cartilage from all horses were examined at necropsy at 120 days. None of the horses were lame during the study, and transient synovitis occurred in the synovectomized joints. The hyaluronan concentration of treated joints decreased at 2 days but returned to normal by 60 days. Synovial fluid composition, including hyaluronan concentration, was unchanged by exercise. Significant cartilage damage was not observed in any of the joints. At 120 days, the healing synovium was devoid of villi and its subintima was fibrotic, however transmission electron microscopy confirmed that an intimal layer was present within the repair tissue. The cells within the repair tissue appeared actively engaged in both synthesis and phagocytosis. Exercise did not modify any of these findings. The results of this study suggest that 120 days after subtotal synovectomy, the joint environment was maintained and and the resected synovium had evidence of restoration and increased metabolic potential. Synovectomized joints withstood exercise but synovial repair was not accelerated by exercise.

Selection of a peptide with affinity for the tumor-associated TAG72 antigen from a phage-displayed library

A hexapeptide phage library was used to select peptides with affinity for the tumor-associated TAG72 antigen. Twenty-one phage clones were selected after the third round of biopanning. Three phage clones with the same DNA insert of ARTLRF were found to bind more strongly to the TAG72 antigen than other phage clones and the wild-type phage. A synthetic decapeptide GAARTLRFGA with two conjunctive amino acid residues of the phage coat protein III on each side of the selected peptide was found to bind more strongly to the TAG72 antigen than to other antigens such as the mouse metallothionein. Furthermore, immunohistochemical studies revealed that this peptide displayed preferential binding to colonic adenocarcinomatous cells expressing the TAG72 antigen. Therefore, this anti-TAG72 peptide may be useful in serving as the starting point with regard to further designing peptidomimetics as potential pharmaceuticals.

Antibody-targeted lymphokine-activated killer cells inhibit liver micrometastases in severe combined immunodeficient mice

BACKGROUND & AIMS

Animal models for hepatic metastases can facilitate the investigation of lymphokine-activated killer (LAK) cell-based immunotherapy. The aim of this study was to investigate the efficacy of ccM4 antibody-targeted LAK cells in inhibiting hepatic micrometastases.

METHODS

Hepatic micrometastases were generated after the intrasplenic injection of HM7 colon carcinoma cells. TAG72 expression was detected in these hepatic micrometastases using ccM4 antibody. The ccM4 antibody was conjugated onto LAK cells by treatment with 17.5% polyethylene glycol 8000. After the intrasplenic injection of HM7 cells, severe combined immunodeficient mice were randomized into five groups (i-v) and received either 10(7) ccM4-LAK cells plus 1000 U interleukin 2 (IL-2; group i), LAK cells plus 50 micrograms ccM4 and IL-2 (group ii), LAK cells plus IL-2 (group iii), IL-2 alone (group iv), or only phosphate-buffered saline (group v).

RESULTS

The ccM4-LAK cells retained cytolytic activity and acquired TAG72-binding reactivity. The results showed that group i had significantly fewer hepatic metastases compared with group ii or group iii (P < 0.05) and even fewer hepatic metastases compared with group iv or group v (P < 0.001).

CONCLUSIONS

These results show that ccM4 antibody-targeted LAK cells significantly inhibited tumor growth in vivo; thus, they can be potentially useful in treatment of hepatic micrometastases.

A genetically engineered single-chain FV/TNF molecule possesses the anti-tumor immunoreactivity of FV as well as the cytotoxic activity of tumor necrosis factor

Recombinant DNA techniques were used to clone, construct and express the fused gene FV-TNF in E. coli under control of the strong T7 bacteriophage promoter in the expression vector pT7-7-FV-TNF. The fusion protein FV/TNF in inclusion bodies from the bacteria homogenate was solubilized in the denaturing solution containing 6 mol/l guanidine and 0.3 mol/l DTT and refolded in refolding buffer containing 8 mmol/l GSSG. The FV/TNF was purified by ion exchange chromatography. The yield of FV/TNF was estimated at 10 mg/l. The purified FV/TNF displayed a single band of 42 kD under reducing conditions, whereas it showed three forms including its monomer (40/42 kD), its dimer (84 kD) and its trimer (126 kD) under non-reducing conditions. Our data showed that this fusion protein retained its bifunctional activities well, namely the anti-TAG72 immunoreactivity of the FV portion and the cytotoxic activity of the TNF moiety. Therefore, the FV/TNF fusion protein may prove useful in targeting the biological effect of TNF to tumor cells as well as in stimulating the immune destruction of tumor cells.

Immunolocalization of hepatic metastases of human colonic cancer by chimeric anti-TAG72 antibody in SCID mice

TAG72 is a well-characterized, human tumor-associated antigen present in > 85% of human colonic cancers. In this study, we established an animal model of hepatic metastases of human colonic carcinoma. The high-mucin variant cell line, designated HM7, was derived from the human colonic carcinoma cell line LS174T. Following intrasplenic injection, HM7 was able to induce much greater hepatic metastases in SCID mice compared to its parental cell line LS174T. Numerous hepatic metastases were evident 18 days subsequent to the intrasplenic injection of tumor cells. Using the chimeric anti-TAG72 antibody ccM4, immunohistochemistry demonstrated strong expressions of the TAG72 antigen in these metastases. Our biodistribution and imaging data also showed that the radiolabelled ccM4 antibody was able to localize hepatic metastases in the SCID mice. Based upon these findings, w anticipate that the herein described SCID mouse model will prove most useful in studying hepatic metastases of human colonic carcinoma by using anti-TAG72 therapeutic immunoreagents.

Autologous human B-cell immune response to pulmonary adenocarcinomatous polymorphic epithelial mucin

In order to investigate whether a B-cell immune response to the polymorphic epithelial mucin (PEM) is present in adenocarcinomatous patients, peripheral blood lymphocytes from 20 patients with adenocarcinomas from various sites were fused with the mouse-human heteromyeloma cell line SHM-D33. One IgM(K) monoclonal antibody derived from peripheral blood lymphocytes of a patient with a lung adenocarcinoma was generated with binding reactivity for bovine submaxillary mucin (BSM). The latter is one of the PEMs, and it contains a large amount of the tumor-associated sialosyl-Tn epitope. The generated antibody was designated KMD-2. Immunohistological studies on various tissues showed that KMD-2 reacted with 6/6 colorectal adenocarcinomas and 4/6 pulmonary adenocarcinomas. The antibody also displayed a slight degree of cross-reactivity with a limited number of normal tissues, especially those that elaborate mucin. Our data show that an autologous antibody response in the form of IgM to the immunosuppressive PEM is present in some adenocarcinomatous patients. The data also suggest that the KMD-2 (IgM/K) antibody may be of clinical importance for diagnostic purposes of adenocarcinomatous disease.

Monoclonal antibody recognizing a determinant on type 2 chain blood group A and B oligosaccharides detects oncodevelopmental changes in azoxymethane-induced rat colon tumors and human colon cancer cell lines

Altered expression of ABH blood group substances is a common feature of human colorectal carcinoma, yet it remains unclear how these structural changes influence the biological properties of tumor cells. Azoxymethane-induced rat colon tumors display many features of the human disease, thereby providing a potentially useful model to study the role of blood group substances in colon cancer progression. We have prepared monoclonal antibodies to a microsomal fraction isolated from an azoxymethane-induced rat colon tumor and selected an antibody that detects cancer-associated changes. Monoclonal antibody (mAb) 3A7 recognizes a determinant on type 2 chain blood group A (GalNAc alpha 1-3[Fuc alpha 1-2]Gal beta 1-4GlcNAc-R) and B (Gal alpha 1-3[Fuc alpha 1-2]Gal beta 1-4GlcNAc-R) oligosaccharides. Expression of the epitope detected by this antibody was developmentally regulated in rat colon, with maximal expression from day 4-21 after birth. Immunohistochemical staining and Western blotting analyses of azoxymethane-induced colon tumors revealed increased expression of the epitope in all of the 21 colonic tumors examined, including preneoplastic glands within transitional mucosa. Conventional and signet-ring adenocarcinomas that had invaded through the muscularis propria (Duke's B2) consistently showed the most intense staining with mAb 3A7, including regions depicting angioinvasion. Some of the lymph node metastases (Duke's C2) stained poorly with the antibody. The epitope was also expressed in blood group A positive human colon carcinoma cell lines, including HT29 and SW480 but not by SW620, a cell line derived from a lymph node metastasis isolated in vivo from the SW480 primary tumor, or in the blood group B cell line SW1417. The glycoproteins detected by mAb 3A7 in rat colon tumors and HT29 cells ranged in size between 50 and 200 kd, including a major species of 140 kd. Affinity chromatography of detergent lysates of normal rat colon on the blood group A specific lectin Dolichos biflorus (DBA)-agarose resulted in nearly quantitative binding of glycoprotein species detected by the antibody. By contrast, immunoreactive glycoproteins from rat colon tumors or HT29 cells bound poorly to DBA-agarose but were retained by another blood group A-binding lectin, Helix-pomatia (HPA)-agarose. These results indicate that colon carcinogenesis results in quantitative as well as qualitative changes in oligosaccharides detected by mAb 3A7 and suggest that the combined use of mAb 3A7 and blood group A-specific lectins may provide a useful tool for early detection of colon cancer.

Single-chain antibody variable region-targeted interleukin-2 stimulates T cell killing of human colorectal carcinoma cells

Recombinant DNA techniques were used to clone, construct and express the bifunctional molecule FV/IL-2. The FV/IL-2 is a single-chain 37 kDa fusion protein expressed in Escherichia coli under control of the strong T7 bacteriophage promoter in the expression vector pT7-7-FV-IL-2. The fused gene fragment FV-IL-2 contains a single-chain anti-TAG72 FV gene fragment and the human recombinant cDNA fragment of the IL-2 molecule. The renatured soluble form of FV/IL-2 was purified from E. coli inclusion bodies using hydroxylapatite chromatography. The yield of this fusion protein was estimated at 2.0 mg/L. Our data showed that the FV/IL-2 molecule retained the TAG72 antigen-binding specificity and the IL-2 activity as measured in the standard T cell proliferation as well as cytotoxicity assays. Therefore, it may prove to be useful in targeting the biological effect of IL-2 to tumour cells and stimulating its immune destruction.

Production of a bifunctional hybrid molecule B72.3/metallothionein-1 by protein engineering

A hybrid anti-tumour B72.3 antibody/metallothionein protein B72.3MT-1 was produced by the construction of the expression vector mpSV2neo-EP1-B72.3MT-1. This vector contained the neo gene as a selection marker, the murine immunoglobulin promoter and enhancer, and the hybrid B72.3 heavy chain gene fragment with mouse metallothionein-1 cDNA gene ligated into its CH2 domain. The expression vector was transfected to the heavy chain loss mutant B72.3Mut(K) cell line. The hybrid protein B72.3MT-1 was purified from transfectant supernates using a Protein G column. We showed that the hybrid protein retained the binding reactivity for the TAG72 antigen as the original B72.3 antibody, and the metal-binding capacity of the native metallothionein molecule. Therefore, the bifunctional hybrid protein B72.3MT-1 may be very useful in cancer imaging when labelled with radionuclides such as 99mTc.

High binding affinity chimeric anti-colorectal carcinoma antibody correlated to enhanced tumor binding and effector function

The genetically engineered mouse/human chimeric cB72.3m4 and cB72.3m12 antibodies all recognized the tumor-associated TAG72 antigen. The high affinity cB72.3m4 antibody had an approximately 18-fold higher affinity constant for the TAG72 antigen than the low affinity cB72.3m12 antibody. The relationship amongst antibody binding affinity, tumor binding and effector functions was studied by using these two antibodies. The data showed that the high affinity cB72.3m4 antibody was reactive with, on average, 15% more colon adenocarcinoma cells on tissue sections than the low affinity cB72.3m12 antibody, and it did not produce any cross-reactivities with various normal tissues. The high affinity cB72.3m4 antibody was able to mediate more effective ADCC and CDC to the human ovarian cancer cells in vitro than the low affinity cB72.3m12 antibody. This study provides evidence that this high affinity chimeric cB72.3m4 antibody may be useful in both immunodetection and immunotherapy of cancer.

Construction and characterization of a high-affinity chimeric anti-colorectal carcinoma antibody ccM4

We have produced a high-affinity chimeric anti-colorectal carcinoma antibody, ccM4, chimerized in both heavy and light chains by the construction of two expression vectors, the chimeric heavy-chain expression vector mpSV2neo-EP1-Vm4Cr1 and chimeric light-chain vector mpSV2gpt-EP1-VKCK. These vectors contained the neo or gpt gene as a selection marker, the murine immunoglobulin promoter and enhancer (EP1), the genomic DNA fragments of human immunoglobulin constant region (CK and C gamma 1), and murine cDNA fragments of VH and VK region amplified and cloned directly from the B72.3 hybridoma RNA by the polymer chain reaction technique. These two vector DNAs were sequentially transfected into the SP2/0Ag14 cell line. Transfectants were selected in media containing both G418 and mycophenolic acid. The ccM4 antibody was purified from transfectant supernatants with positive binding reactivity for the TAG72 antigen on a protein A column. We demonstrated that ccM4 antibody retained the same high binding reactivity for the TAG72 antigen as its counterpart, the high-affinity chimeric heavy-chain cB72.3m4 antibody. The ccM4 antibody bound specifically to human colon cancer cells, displayed biodistribution patterns similar to cB72.3m4 antibody, and mediated effective antibody-dependent cellular cytotoxicity to human OVCAR3 tumor cells. Therefore, the high-affinity chimeric ccM4 antibody should be useful in cancer immunotherapy.

Carrageenan-induced intestinal injury: possible role of oxygen free radicals

There is a growing body of evidence that implicates oxygen free radicals in a wide variety of inflammatory conditions in various body systems including the gastrointestinal tract. The purpose of this study was to ascertain whether or not oxy-radicals play a role in carrageenan-mediated intestinal injury. Allopurinol, superoxide dismutase-polyethylene glycol, and dimethyl sulfoxide, respectively, were administered to the carrageenan rat model for 30 to 32 days. Collectively, all three drugs attenuated the carrageenan-mediated injury as shown by four indices of intestinal damage: ulceration (p = 0.0007); abnormal villous pattern (p = 0.0002); degree of inflammation (p = 0.0001); and extent of inflammation (p = 0.0025). Dimethyl sulfoxide appeared to be the least efficacious of the three drugs. The results suggest that oxygen free radicals play a role in carrageenan-mediated intestinal injury, and that one of the sources of these oxy-radicals may be the intestinal macrophage.