Study of a soluble tumor-associated marker composed of CEA related molecules recognized by three monoclonal antibodies

Three MAbs, MLuC2, MLuC8 and MLuC9, directed against a molecule that is produced and secreted by carcinoma cells were studied with the aim of developing a double-determinant immunoradiometric assay (DDIRMA). We demonstrated by means of immunoblotting, immunodepletion and DDIRMA techniques, that MLuC9 reacted against the CEA molecule, whereas MLuC2 and MLuC8 reacted against a 90 Kd molecule related to CEA. The DDIRMA performed with the anti-CEA as a catcher MAb and the anti-90 Kd as a tracer MAb was found to be positive with the HT29 soluble extract, which suggests the existence of CEA/90 Kd dimeric molecules. The same reactivity was found when sera from patients with lung carcinomas were tested, which excludes that this molecule could be an artefact due to the cell solubilization procedures. The association between CEA and the 90 Kd molecule was further confirmed by immunodepletion experiments in which the immunoprecipitation with one MAb not only removed the recognized molecule, but also partially immunodepleted the material from the other.

In Vivo and in Vitro Growth of SCLC Cells Derived from Biopsies

In order to increase the availability of SCLC cells derived from biopsies, in vivo and in vitro growth methods were investigated. The cells grown in both conditions were periodically monitored for reactivity with 2 monoclonal antibodies (MAbs): MLuC1 directed against SCLC cells and IM1 which recognizes the class II antigen on activated lymphocytes and macrophages. About 50 % of the 28 analyzed SCLC specimens were found to proliferate in one or both systems. The in vitro-grown cells exhibited the same heterogeneity found in the original cell suspensions and moreover, in some cases only normal cells were recovered after several in vitro passages. From the subcutaneous transplanted tumors a large number of MLuC1-positive tumor cells could easily be recovered, thus indicating the validity of the in vivo methodology. The MBr1 MAb, directed against an epithelial antigen, was found to react with about 50 % of the 26 tested tumors, mainly those which demonstrated in vivo and/or in vitro growth capacity. These data suggest that only some tumors, presumably with peculiar biological characteristics, can efficiently grow in these artificial systems.

New Scm (Structuredness of the Cytoplasmatic Matrix)-Based Approach in Breast Cancer Detection

Aims and Background

We evaluate the possibility to use a combination of techniques such as lymphocyte stimulation and the Cell Scan instrument for early detection of breast cancer. This method can detect differences in lymphocytes activation in the presence or absence of cancer.

Methods

The Cell Scan is a static cytometer system able to examine cellular membrane polarization. We screened 88 women with benign breast lesions, 207 women with mammary carcinoma and 325 healthy blood donors. After lymphocytes separation, each blood sample was incubated with encephalitogenic factor (EF), phytohaemagglutinin (PHA) and Breast Antigen (BrAg) then SCM test was performed.

Results

Positivity was 50% among breast cancer patients, 34% among women affected by benign disease and 27% and 22% respectively among healthy female and male controls with an increase of the specific predictivity of the test during the period of ovulation. A significant difference ( P <0.0001) was observed between healthy donors and breast cancer patients.

Conclusions

This results suggest that the Cell Scan test could be useful to investigate patient's immunogenicity to molecules known to be involved in tumor development and progression, such as oncogene or suppressor gene products, which could be appropriate targets for immune-derived therapeutic approaches.

Production and Characterization of two Monoclonal Antibodies Directed against the Integrin β1 Chain

The production and characterization of two new monoclonal antibodies (MAbs), designated MAR4 and MAR5, raised against the partially purified α5β1 integrin, are described. The reactivity of these 2 MAbs on tumor cell lines indicated that they reacted on all the cells expressing the β1 subunit independently of the α5 expression. Both MAbs were found to immunoprecipitate on 3 cell lines, a protein of 120 KD corresponding to the molecular weight be the β1 chain, in addition to proteins of other MW corresponding to the α subunits differentially expressed by these cells. The cross-competition experiments showed that MAR4 and MAR5 recognize the same epitope. These 2 MAbs seem to be useful reagents for the characterization of the VLA expression in tumor cells.

Influence of Thymectomy, Splenectomy, and Cortisone on Carcinogenesis

Groups of outbred albino CTM mice were either thymectomized or splenectomized at 4 weeks of age and administered urethan 0.4 percent in the drinking water for 10 days at 5 weeks. In comparison with intact, urethan-treated animals, the thymectomized, urethan-treated mice had a slightly lower incidence of malignant lymphomas (19 against 24 %), a marked decrease of mammary tumors (31 against 62%), and increased incidence of lung adenomas (84 against 48%) and of skin papillomas (10 against 1%). Thymectomized, but otherwise untreated mice developed less lymphomas and mammary tumors than intact, untreated controls. Splenectomy did not modify significantly the tumor incidence. In a second experiment, groups of CTM mice were administered either 1 mg of cortisone s. c. daily for 10 days or urethan in the drinking water for 5 days followed by 5 days of cortisone or viceversa, or urethan alone. No major differences in the tumor incidence in the various groups were observed, but for a decreased incidence of thymic lymphosarcomas in the group with cortisone after urethan. In a third experiment, CTM mice were given 2 mg urethan within the first day after birth and thymectomized or sham operated during the anesthesia caused by the urethan. Both groups had a very high incidence of hepatomas and lung adenomas, and developed only few lymphomas and mammary tumors. Finally, a group of C3H mice thymectomized at birth under Nembutal anesthesia, developed a considerably lower incidence of hepatomas and mammary tumors than sham operated animals.

Nature and Properties of C3Hf Natural Antitumor Cytotoxins Directed against Murine Lymphosarcoma Cells

The nature and some biological properties of the natural antitumor cytotoxins previously found in normal C3Hf serum, have been investigated. By immunoelectronmicroscopy study, employing rabbit hybrid antibodies with specificity for mouse Ig and ferritin, the C3Hf cytotoxins were shown to belong to immunoglobulins. By gel filtration, by inhibition experiments of the cytotoxic serum activity with monospecific anti-IgG and anti-IgM sera, and by 2-mercaptoethanol treatment of the C3Hf serum, the cytotoxic immunoglobulins were demonstrated to belong to the IgM class. They were not inactivated by heating until 60 °C and were able to activate guinea pig, rabbit, and human complement. The highest cytotoxic activity of the normal C3Hf serum was found when cells and serum were incubated at the low temperature, suggesting a low binding affinity of the cytotoxic IgM.

Immunohistochemical Reactivity of a Monoclonal Antibody Prepared against Human Ovarian Carcinoma on Normal and Pathological Female Genital Tissues

The reactivity profile of the monoclonal antibody (MAb) MOv18, raised against a poorly differentiated ovarian carcinoma specimen, was studied on normal tissues and tumors from the female reproductive system and on the kidney, which like the oviducts, vagina and uterus, also derives from the intermediate mesoderm. The obtained results indicate that MOv18 recognizes an epitope present on the normal epithelium of the oviducts, on 14-week old fetal kidney and, focally, on proximal and distal tubules of normal adult kidney. A strong reactivity was found on ovarian carcinomas, on invasive squamous carcinomas of the cervix and on endometrial carcinomas and hyperplasias. The antigen recognized by MOv18 (CaMOv18) therefore seems to be an epithelial cell marker associated with intermediate mesoderm differentiation, which can be derepressed during the neoplastic transformation of the ovary and the uterus.

Relationship between Cambrl Expression and Tumor Progression in Small cell Lung Carcinomas

In order to study the possible relationship between antigenic phenotype and tumor progression, 63 small cell lung carcinomas (SCLC) biopsies derived from primary or metastatic tumors were tested by immunofluorescence and immunoperoxidase techniques with an anti-carcinoma monoclonal antibody designated MBr1. Primary tumors were found to be less reactive with MBr1 than the local and distant metastatic lesions (57 % versus 75 % and 89 % positivity respectively). A life table analysis on the tested cases indicated an inverse association between the expression of the marker recognized by the MBr1 MAb (CaMBr1) and overall survival (p < 0.01): patients with MBr1-positive tumors showed a shorter survival time in comparison to patients whose tumors did not express the marker. The same correlation between survival and CaMBr1 expression was found even when only the 31 cases of early stage disease patients were considered (p < 0.05). Different tumor aggressiveness or resistance to therapy of MBr1-positive tumors could be responsible for the shorter survival time of the patients.

Influence of in Vitro Culture Conditions on Tumor Cell Differentiation

We studied the influence of different in vitro culture conditions on the growth characteristics of certain human and murine tumor cell lines maintained in either conventional medium supplemented with FCS or in serum-free synthetic medium. A lower growth rate was observed for all of the cell lines maintained in serum-free conditions. Three human melanoma cell lines which were Ia-positive and showed an absence of pigmentation in the presence of FCS, without it produced melanin and lost their Ia antigens. In serum-free conditions, a murine hybridoma lost its membrane IgM and two human carcinoma cell lines expressed and secreted an increased amount of several tumor markers identified by monoclonal antibodies. The results of the study are in keeping with the hypothesis that tumor cell lines cultured in serum-free medium acquire differentiation characteristics.

Tumor Radioimmunolocalization in a Murine System using Monoclonal Antibodies

Tumor localization was obtained in a murine system by use of 131I-labeled monoclonal antibodies, both of IgG and IgM class. The A6 IgG2 monoclonal antibody (which recognizes the gp70 of MuLV) and the B3 IgM monoclonal antibody (which recognizes a proteic structure widely exposed on chemically induced tumors), which both manifest an in vitro cytotoxic activity for various types of murine lymphomas, were injected in tumor-bearing (B6 × BALB/c)F1 mice and B6 mice, respectively, at the dose of 1 μg per mouse. The radioactivity count demonstrated an optimal tumor accumulation of the radiolabeled monoclonal antibodies 96 h after iodine injection, although an initial accumulation was already present 48 h after injection. The scanning detection was less sensitive, since at 48 h no tumor localization was possible. In the experiments with the A6 antibody, the presence of the gp70 in the circulating form, demonstrated by the detection of immunocomplexes in kidney and spleen of tumor-bearing mice injected with the A6, did not prevent radioactivity accumulation in the tumor. This accumulation was found to increase with tumor size only up to 1 g of tumor weight, then a decreased binding index was observed, whereas in the kidney the accumulation was progressive and paralleled the increase in tumor weight.

MOv18 Monoclonal Antibody in Diagnostic Applications: Capability to Recognize the Histotype of the Original Tumor

Cells from 52 ascitic fluids and 28 abdominopelvic cavity washings, obtained from 46 ovarian cancer patients, 17 patients bearing malignancies of non ovarian sites and 17 patients with non-malignant ovarian diseases, were tested using 2 methods: traditional cytology and monoclonal antibody immunofluorescence. The immunologic test using the MOv18 MAb, raised against ovarian carcinoma, revealed immunoreactive cells in 83 % of the 36 cytologically positive fluids and in one of the 8 negative fluids from ovarian carcinoma patients and in 18% of the 17 fluids from patients with non-malignant ovarian disease. Forty six cytologically positive ascitic fluids from malignant patients were analyzed in order to evaluate the ability of this MAb to identify the histotype of metastatic cells. Ninety-three percent (26/28) of the effusions from non-mucinous ovarian carcinomas contained MOv18-positive cells, whereas no reactive cells were found in cytologically malignant fluids from patients with ovarian tumors of other oncotypes or with carcinomas of non-ovarian origin. The MOv18 reagent, used as an adjuvant in cytological analysis, can help in the identification of the histotype of metastatic cells of unknown origin.

Expression of Two Antigens Defined by Monoclonal Antibodies in Normal, Benign and Malignant Human Mammary Tissues

We examined the reactivity of two monoclonal antibodies (MAbs), MBrl and MBr8, on sections from normal breast tissues, benign lesions, primary infiltrating carcinomas and distant breast cancer metastases and compared the expression of the recognized antigens (CaMBr1 and CaMBr8 respectively) in these different normal and pathologic conditions. The expression of both antigens was found to significantly decrease in the neoplastic tissues, in comparison to normal breast tissue (34% vs 61% for MBr1 and 52% vs 86% for MBr8; p < 0.001 for both). Atypical epithelial hyperplasia was found to be reactive on the same level (31%) of the tumors when tested with MBr1, whereas its reactivity was similar to that of normal tissues (78%) when MBr8 was used. Non-atypical epithelial hyperplasia showed the same reactivity with both MAbs (positive staining on about 50% of the cells). 65% of the « in situ » ductal carcinoma cases was MBr1-positive, whereas 50% was MBr8-positive; these values, when compared with the reactivity on normal glands, were significantly lower for MBr8, but not for MBr1. When testing sections from premenopausal women who had biopsies performed on different days during their menstrual cycle a correlation was found between the expression of CaMBr1 in normal breast epithelial cells and the stimulatory phase of the cycle. These findings suggest that both antigens are typical of normal breast and their expression could possibly decrease in pathologic tissues.

Analysis of Rabbit and Guinea PIG Complement Efficiency in Cytotoxicity Tests against Fibrosarcoma and Lymphosarcoma Cells

In a complement-dependent 51Cr cytotoxicity assay, using as target murine fibrosarcoma or lymphosarcoma cells, the rabbit complement (RC) was more efficient than guinea pig complement (GPC) when tested either with strong antisera, such as anti-histocompatibility sera, or with weak sera, such as sera from normal mice shown previously to possess a natural antitumor response. The high efficiency of RC was not due to activation by antibodies of a different class or specificity than those activating GPC. In fact, both 2-mercaptoethanol (2-Me)-sensitive or-resistant immunoglobulins could activate both RC and GPC, and the results of absorption tests indicated that the antibodies detected using either of the 2 complements were directed against the same specificities. In addition, the results of tests searching for cooperative antibodies excluded that a cooperative effect might be responsible for the high efficiency of RC. With weak antisera, sera of different rabbits were found to have different complement activity.

Histopathological Characterization of a Novel Monoclonal Antibody, MLuC1, Reacting with Lung Carcinomas

A monoclonal antibody (MoAb), MLuC1, derived from the fusion of P3 - X63 - Ag 8 - U1 mouse myeloma cells with spleen cells from an HR mouse immunized with the carcinoma cell line SW626, was studied to define its reactivity profile on normal and neoplastic human tissues and its potential clinical applications in lung cancer. Evaluation of paraffin sections using the ABC immunoperoxidase method showed a « pan-epithelial » reactivity; a large majority of epithelial components of organs in the respiratory, digestive and urogenital systems (except liver, rectum and ovary) were immunostained. As regard to neoplastic tissues MLuC1 recognized 84 % of lung carcinomas (82 % of small cell, 100 % of squamous cell, 74 % of adenocarcinomas), 86 % of breast and 62 % of ovarian carcinomas. On the contrary, MLuC1 was non-reactive with the other normal and tumoral non-epithelial tissues. Due to its spectrum of reactivity this MoAb could be useful for different diagnostic purposes such as differential diagnosis and lung cancer cytology.

Production of Monoclonal Antibodies against a New Carcinoma-associated Marker in View of Developing a Serological Test

By immunizing a mouse with human metastatic breast tumor cells from patient effusions and infiltrated lymph nodes, a monoclonal antibody (MLuC2), which identifies a new carcinoma-associated marker, was raised. The reactivity of this reagent was studied by immunohistochemistry on live and fixed cells from tumor cell lines and on frozen sections from surgical specimens. Besides reacting with 73% of breast carcinomas, MLuC2 also reacted with 93% of non-small cell lung carcinoma (NSCLC) and with a few normal tissues. The MLuC2-recognized molecule (CaMLuC2), whose MW was 90 KDa according to immunoblotting experiments, was found to be detectable in the serum and could therefore be of particular interest for serological diagnostic applications. Since the CaMLuC2 epitope was not polyexpressed on the bearing molecule, we produced a new generation of MAbs in order to define epitopes coexpressed with CaMLuC2 on the same 90 KDa molecule, and which are therefore suitable to develop a double-determinant immunoradiometric assay (DDIRMA) for the detection of this marker in the sera of lung carcinoma patients. Different analyses by immunohistochemistry, binding inhibition tests and DDIRMA, proved that the two new reagents developed, MLuC8 and MLuC9, recognize the same or closely related epitopes, which are however different from CaMLuC2, but which are all present on the same molecule. Preliminary immunoradiometric tests performed on sera from lung cancer and control patients showed a good specificity but a low sensitivity. In fact, only 42% of the 28 tested sera samples from NSCLC patients scored positive despite the fact that more than 90% of the NSCLC expressed the relevant antigen

Hybrid Antibodies in Cancer Diagnosis and Therapy

Monoclonal Antibodies (Mabs) represent a promising tool for cancer diagnosis and theraphy.

Administration of MAbs alone or conjugated to cytotoxic agents has been attempted but has significant limitations. Another potentially effective approach is the use of bispecific or bifunctional antibodies where the capacity to recognize the tumor cell and the toxic agent or lymphocyte activation molecule are united in one MAb. The hybrid molecule can be produced by chemical linkage between the two parentalantibodies, or alternatively by a biological approach that consists in the fusion of the two selected hybridomas. In the resulting quadroma cell the hybridoma immunoglobulin chains recombine randomly to form the bifunctional MAb.

In different in vitro and in vivo models, bifunctional MAbs against tumor and CDS at nanomolar concentration has been shown to promote tumor cell killing by cytotoxic T cells.

Specific localization of chemotherapeutic drugs in xenografted tumors has been demonstrated in mice pretreated with hybrid MAbs.

The advantages of the hybrid MAb approach are that it should reduce the MAb biodistribution problem and that it involves no chemical manipulation between the functional agent and the MAb molecules.

Urethan Carcinogenesis in Newborn, Suckling, and Adult Mice of C57BL, C3H, BC3FJ, C3Hf, and SWR Strains

Urethan was given to four inbred strains of mice and to one hybrid, either in the drinking water at 0.4 per cent for 15–20 days to 5-week old animals, or subcutaneously 3 mg once to newborns, or intraperitoneally 1 mg/g body weight, 5 times, once every second day, to 10-day old animals. The 5 treatments starting at 10 days of age induced a high percentage of rapidly developing thymic lymphosarcomas, while in the groups treated at birth or at 5 weeks, few tumors of this type were observed. The incidence of non-thymic malignant lymphomas or leukemias was not influenced by urethan, apart from a reduction of latent period. A small number of mammary adenocarcinomas occurred among the treated females of the C57BL and SWR strains but none in the control groups. In C3Hf and BC3F1 females there was a high incidence of mammary tumors when treatment was started at 5 weeks; treatment at birth or at 10 days did not modify the control incidence. On the contrary, hepatomas developed more rapidly and in higher percentage in the animals treated at birth or at 10 days. The incidence of pulmonary adenomas was increased by treatment in all strains parallel with the spontaneous occurrence. Tumors of harderian glands, skin, kidney, thyroid, adrenals and ovaries were also more frequent among treated animals.

Comparison of the Natural Humoral Antitumor Reactivity of Different Strains of Mice

Normal serum from C3Hf mice showed a complement-dependent cytotoxic reactivity against EL4 lymphoma cells, starting from 2 to 3 months of age, whereas normal serum from BALB/c and C57BL/6J mice became reactive only at a later age. The cytotoxins of normal sera of the 3 strains, as well as of a C57BL antiembryo antiserum studied in parallel, belong to the IgM class. When absorption tests were performed, using a variety of absorbing cells, marked differences were found among the sera, which according to their behavior could be divided in two groups: one group comprises the BALB/c and the C57BL sera, the other group the C3Hf serum from both young and old mice and the antiembryo antiserum. The reactivity of the 3 latter sera seems to be directed against specificities related to an ecotropic N-tropic virus, which on the contrary did not seem to be involved in the reactivity of BALB/c and C57BL sera. The C57BL antiembryo antiserum obtained by immunization with C3Hf embryos behaved differently from the C57BL normal serum and similarly to the C3Hf normal serum.

Production and Characterization of Monoclonal Antibodies Directed against the Laminin Receptor Precursor

The 67-kDa laminin receptor (67LR) is an important tumor marker whose molecular structure has not yet been fully elucidated. To shed new light on this molecule, we raised a series of eight new monoclonal antibodies, designated MPLR1 to 8, directed against the 37-kDa recombinant laminin receptor precursor (37LRP). Cross-competition experiments demonstrated that the epitopes recognized by MPLR2, 4 and 5 partially overlap, since MPLR4 and 5 compete with labelled MPLR2 for the binding to recombinant 37LRP. These three antibodies belong to the IgG1 class, whereas the other ones are all IgM. Presumably due to the fact that they are directed against partially unfolded antigenic determinants expressed on the recombinant protein, MPLRs did not recognize the native protein. Indeed, they showed no reactivity at the membrane level in cytofluorimetric analysis and they did not work in immunoprecipitation experiments. In contrast, these reagents are valuable tools in immunoblotting, since they clearly identify a 67-kDa protein (the mature laminin receptor) in addition to the 37-kDa precursor form. MPLRs are thus a new powerful tool which could help in the characterization of the still enigmatic 67LR molecule.

Natural Antilymphoma Antibodies in C3Hf Mice Serum: Lack of Identity with Autoimmune and anti Murine Leukemia Virus Antibodies

Absorption experiments on C3Hf normal mouse sera followed by cytotoxic tests on EL4 lymphoma cells were done to investigate a possible identity between natural antilymphoma antibodies (NAA) and various types of autoantibodies known to be present in normal mouse sera. Single C3Hf normal sera were also tested both by cytotoxicity on EL4 cells and by radioimmune precipitation assay (RIP) on 125I-labelled AKR ecotropic virus to ascertain whether or not viral antigen are the target structures of the NAA activity. The study provides evidence that NAA coexist with autoanticorpal and antiviral activities although they are distinct entities.

Fc Receptor-Like Structures on in Vitro-Cultured Human Ovarian Tumor Cells

Four ovarian cystadenocarcinomas cultured in vitro were tested by a radioisotopic method with sera from cancer patients or healthy donors to search for a possible specific antitumor immune response of patients bearing ovarian tumors. However, the ovarian tumor cells were found to bear on their membrane surface structures able to bind immunoglobulins from any tested serum, thus making impossible the detection of a hypothetical specific antitumor antibody. These structures were demonstrated to bind the Fc portion of the Ig and were therefore similar to the Fc receptors described on various normal cells, particularly of the immunocompetent compartment.

Isonicotinic Acid Hydrazide and Urethan Carcinogenesis in suckling SWR Mice

Five i.p. injections of 1 mg urethan/g body weight on alternate days administered to 10-day old SWR mice resulted in the development of thymic lymphosarcomas in 60 % and of lung adenomas in nearly 100 % of the animals, irrespective of sex. Concurrent treatment with isonicotinic acid hydrazide (INH), 0.1 mg/g body weight, administered five times on alternate days starting at 9 days of age, did not modify the carcinogenic effect of urethan. The treatment with INH alone did not induce a higher tumor incidence than in untreated controls.

A Double Determinant Radioimmunoassay Mov2-Mov8* for Monitoring Ovarian Carcinomas: Definition of the Methodology

A double-determinant radioimmunoassay for the detection of circulating antigens associated with human ovarian carcinoma was developed using two monoclonal antibodies: MOv2 and MOv8 employed respectively as catcher and tracer. The development of the method through three different procedures enabled us to detect the presence of CaMOv2-CaMOv8 carrying molecules in 14 out of 15 ascitic fluids from ovarian carcinoma patients whose tumors were found to be positive with MOv2 and MOv8 monoclonal antibodies by immunofluorescence. Moreover, 13 out of 15 ovarian carcinoma patients presented high levels of antigen in their serum (60-170 Ua/ml). Low levels of antigen were observed in the normal population, the values ranging from 30-40 Ua/ml. However, in 13 out of 100 apparently healthy women high levels of antigen were found in the serum

Correlation between the Presence of Natural Antitumor Antibodies and Activation of Mulv Endogenous Virus in Balb/C Mice

Individual 3-month-old or 12-month-old BALB/c mice, as well as 5-month-old nu/nu or nu/ + BALB/c mice, showed a direct correlation between the serum level of natural antitumor cytotoxic antibodies and the capacity of spleen cells to infect SC-1 cells permissive for murine ecotropic viruses. Pooled or individual sera from 3-month-old BALB/c mice, negative for the presence of natural antitumor cytotoxic antibodies and whose spleen cells were unable to infect the SC-1 cells, were negative both for SC-1 cells and SC-1 cells infected by MuLV. On the contrary, pooled or individual sera from 15-month-old BALB/c mice, positive for the presence of natural antitumor antibodies and with infecting spleen cells, were cytotoxic for infected SC-1 cells but not for the uninfected ones. The infection of SC-1 cells by MuLV could be inhibited by 3-month-old spleen cells, and this effect was suppressed by depriving the inhibiting spleen cells of T cells by means of an anti-Thy-1 antibody plus complement. The cells with infectious capacity did not belong to the T-cell compartment, as demonstrated by the lack of infection after passing the infecting spleen cells through an anti-Ig column, whereas T-deprivation did not modify the infectious capacity. A natural anti-gp70 monoclonal antibody, which exerted a complement-dependent cytotoxic effect on tumor cells, stronghly inhibited the infection of the permissive SC-1 cells by MuLV.

Monoclonal anti-CEA Antibody: Factors Affecting Localization in a Preclinical Study

131I-labelled anti-CEA monoclonal antibody was tested in an animal model to evaluate: influence of antibody type (whole versus F(ab’)2 fragments), administration route (i.v. versus i.p.), dose of tracer (100 μCi versus 1000 μCi), growth site (s.c. versus i.p.) and size of tumor. Athymic mice bearing CEA-producing human colon carcinoma (HT-29) or human melanoma as an irrelevant tumor (MeWo) received tracer and immunoscintigraphy and the localization ratios (LR) were compared. In HT-29 bearing animals F(ab’)2 fragments localized better than the whole antibody. The LR were higher after i.p. administration of the tracer, independently of the tumor characteristics or the injected dose. The highest values were achieved when the radioactivity remaining in the whole body was below 2% of the injected dose. The images were negative when the i.p. injected dose was low or tumor growth was i.p. but positive in the other conditions (i.v. administration, high tracer dose, s.c. tumor growth).

In the animals bearing melanoma, images scored positive or negative when the tumor weight was respectively above or below 400 mg, but the LR were always low.

Response to cyclophosphamide, methotrexate, and fluorouracil in lymph node-positive breast cancer according to HER2 overexpression and other tumor biologic variables

PURPOSE

There is considerable interest in biologic markers able to predict the response of cancer patients to therapy. HER2 overexpression is a potential indicator of responsiveness to doxorubicin and paclitaxel and of unresponsiveness to tamoxifen in breast carcinoma patients. However, the significance of HER2 overexpression in responsiveness to cyclophosphamide, methotrexate, and fluorouracil (CMF) has remained unclear. In this study, we investigated this issue in the 386 breast cancer patients in the first CMF controlled clinical trial with a 20-year follow-up.

PATIENTS AND METHODS

Node-positive breast carcinoma patients were randomly assigned to receive either no further treatment after radical mastectomy (179 women) or 12 monthly cycles of adjuvant CMF chemotherapy (207 women). Overexpression of HER2 and the status of other tumor variables was assessed by immunohistochemistry in at least 324 (84%) of the 386 patients. Statistical analyses were performed to assess the efficacy of CMF treatment for the subgroups defined by HER2 and the status of other variables using a Bayesian approach. The end points considered were relapse-free survival (RFS) and cause-specific survival (CSS).

RESULTS

Bayesian analysis of the treatment effect for HER2 and other variables indicated a clinical benefit from CMF treatment in all subgroups defined according to variables status. In particular regarding HER2 status, Bayesian estimates of RFS hazard ratios were equal to 0.484 and 0.641 and estimates of CSS hazard ratios were equal to 0.495 and 0.730 for HER2-positive and -negative tumors, respectively.

CONCLUSION

CMF treatment showed a clinical benefit in the considered subgroups, defined according to HER2 and other tumor variables status. Patients with HER2-positive or HER2-negative tumors benefit from CMF treatment, and the poor prognosis associated with the HER2 overexpression in the untreated group could be completely overcome by the chemotherapy treatment.

Cooperative effects of Mycobacterium tuberculosis Ag38 gene transduction and interleukin 12 in vaccination against spontaneous tumor development in proto-neu transgenic mice

An approach to stimulating an immune response against tumors is to transduce tumor cells with bacterial genes, which represent a "danger signal" and can induce a wide immune response. Mycobacterium tuberculosis genes and their encoded proteins play a pivotal role in linking innate and cell-mediated adaptive immunity and represent ideal candidates as immune adjuvants for tumor vaccines. The efficacy of a cancer vaccine, obtained by transduction of a mammary tumor cell line with the M. tuberculosis Ag38 gene, was investigated in female mice transgenically expressing the rat HER-2/neu proto-oncogene. These mice spontaneously develop stochastic mammary tumors after a long latency period. The onset of spontaneous mammary tumors was significantly delayed in mice vaccinated with Ag38-transduced cells but not in mice vaccinated with nontransduced cells as compared with untreated mice. Protection from spontaneous tumor development was increased when mice were vaccinated with the mycobacterium gene-transduced vaccine plus a systemic administration of interleukin 12 (IL-12) at a low dose. Mice vaccinated with nontransduced cells plus IL-12 developed tumors, with only a slight delay in tumor appearance as compared with the control group. Lymphocytes obtained from lymph nodes of mice vaccinated with transduced cells secreted high levels of IFN-gamma. CD3+CD8+ spleen cells derived from these mice responded to the tumor with IFN-gamma production. These data indicate the efficacy of a short-term protocol of vaccinations exploiting the adjuvant potency of a M. tuberculosis gene and low doses of IL-12 in a model of stochastic development of mammary tumors. This adjuvant approach may represent a promising immunotherapeutic strategy for cancer immunization.

Detection of aberrant isotype switch recombination in low-grade and high-grade gastric MALT lymphomas

Gastric mucosa-associated lymphoid tissue (MALT) lymphoma originates from reactive lymphocytic infiltrates during chronic gastritis, closely associated with Helicobacter pylori infection. MALT lymphomas may be either "low grade" or "high grade," and transformation from low grade to high grade can occur. To obtain information on the maturational state of MALT lymphoma cells, we investigated their ability to undergo isotype switch recombination, which together with immunoglobulin variable gene somatic mutation, contributes to normal B-cell maturation. Using specific probes for the immunoglobulin heavy-chain (IgH) switch regions, we found by Southern blot that 3 out of 5 low-grade cases and 2 out of 2 high-grade cases showed rearrangements within IgH switch regions, which appeared aberrant in 4 of the 5 cases. The cloning of two rearranged fragments from one low-grade and one high-grade case confirmed the aberrant nature of the rearranged fragments. A deletion from the switch mu region (S mu) to the first constant mu exon (C mu 1) and a second deletion from the second constant mu exon (C mu 2) to the gamma 3 region (gamma 3) was detected in the low-grade case. In the high-grade case, there was a deletion of the IgH intronic enhancer (E mu) and a 336-base pair (bp) insertion into the S mu region of a gene (KIAA0307) normally located at 15q24. These data demonstrate for the first time the ability of MALT lymphoma cells to undergo aberrant isotype switch recombinations, which might be directly involved in the development or progression of malignancy.

Interaction of folate receptor with signaling molecules lyn and G(alpha)(i-3) in detergent-resistant complexes from the ovary carcinoma cell line IGROV1

Using as a model the ovary carcinoma cell line IGROV1, we analyzed the partitioning of the glycosyl-phosphatidylinositol-anchored folate receptor into lipid rafts based on its relative detergent insolubility, with a focus on physically and functionally associated signaling molecules. A variable amount (40-60%) of folate receptor was found in low-density Triton X-100 insoluble complexes together with subunits of heterotrimeric G-proteins and the src-family non-receptor tyrosine kinases p53-56 lyn. In the same fraction the structural component of caveolae, caveolin, was not detected at the protein level, although the corresponding mRNA was detected in trace amounts. Comodulation of folate receptor and signalling molecules was observed in the detergent-insoluble complexes during cell proliferation or induced by phosphatidylinositol-specific phospholipase C treatment or by interaction with anti-folate receptor monoclonal antibodies. Moreover, complexes of folate receptor, lyn and the G(α)(i-3) subunit were immunoprecipitated using either anti-folate receptor or anti-lyn antibodies. In vitro kinase assay of the immunoprecipitates revealed stimulation of phosphorylation of common and specific proteins. In particular, the p53 form of lyn appeared to be enriched and phosphorylated in the anti-folate receptor MOv19 monoclonal antibody immunoprecipitate, whereas a 40 kDa band common to anti-folate receptor and anti-lyn immunoprecipitates was the phosphorylated form of the G(α)(i-3) subunit. These findings point to the functional interaction between folate receptor and associated signaling molecules.

Tamoxifen chemoprevention of a hormone-independent tumor in the proto-neu transgenic mice model

We evaluated the effect of tamoxifen (TAM) on tumor development in proto-neu transgenic mice that spontaneously develop mammary carcinomas overexpressing the neu protein. These mammary carcinomas are hormone independent because superimposable growth of transplants was observed in females and males. Virgin transgenic mice treated with TAM from 24 weeks of age, ie., when subclinical mammary tumors are already present, showed a slightly accelerated tumor development. In contrast, transgenic mice treated with TAM starting at 12 weeks of age, when subclinical tumors are not yet present, showed a 50% reduction of tumor incidence. Light microscopy analysis of the mammary gland of these mice revealed an apparently normal ductal branching but a complete regression of the acini. In conclusion, TAM can prevent the occurrence of hormone-independent breast carcinoma if given early enough to inhibit normal cells.

Expression profile of saccharide epitope CaMBr1 in normal and neoplastic tissue from dogs, cats, and rats: implication for the development of human-derived cancer vaccines

CaMBr1 is a blood group-related tumour-associated antigen, whose pattern of expression provides a therapeutic window for passive or active immunotherapy and points to the promise of a vaccine against carcinomas overexpressing this antigen. In this context, an animal model that closely mimics the human situation would be extremely useful. We, therefore, utilised the murine monoclonal antibody MBr1, which defines CaMBr1, as a useful probe to detect the molecule targeted for vaccine development on canine and feline spontaneous breast and uterus tumours and on their normal counterparts, and on rat normal tissues and carcinoma cell lines. Immunoperoxidase staining of cryostat sections revealed homogeneous CaMBr1 expression only in normal feline uterus and a uterus papilloma, whereas MBr1 reactivity was very weak and heterogeneous in normal (1/3 and 1/3) and tumour (1/10 and 1/6) breast tissues from dogs and cats, respectively. In contrast, the data obtained in rat tissues were reproducible in the strains tested and showed that CaMBr1 was expressed in all epithelial tissues of the digestive tract, although with variable intensities. Monoclonal antibody staining appeared to correspond to membrane-bound structures as well as mucinous secretions. Similarly, secretion products of lactating mammary glands expressed CaMBr1. The spectrum of expression on rat digestive tract was broader than that in humans but the specificity of MBr1 reactivity was confirmed by competition assay with a synthetic tetrasaccharide that mimics the CaMBr1 antigen. On FACS analysis, only one of two clonal derivatives of the rat breast carcinoma line RAMA 25 expressed CaMBr1, and a negative cell subset was evident in repeated experiments. By contrast, both colon carcinoma lines, DHD/K12 and CC531, showed staining with MBr1, albeit at different levels of intensity, and no evidence of a negative subset. The cell line CC531 maintained or even increased CaMBr1 expression levels following transplantation in syngeneic immunocompetent animals. Our data suggest the usefulness of the rat as a test model for vaccines against human cancers overexpressing the CaMBr1 antigen.

Fluctuation of HER2 expression in breast carcinomas during the menstrual cycle

The hormonal milieu at time of tumor surgery seems to have a significant impact on survival in premenopausal breast cancer patients. Indeed, surgery performed during the follicular phase of the menstrual cycle was suggested to correlate with a poor prognosis. To investigate the relationship between prognosis and menstrual cycle at time of surgery, we analyzed the expression of some markers associated with tumor aggressiveness, such as the hormone receptors, HER2, p53, Bcl2, and cathepsin D in breast carcinomas obtained from 198 premenopausal women who underwent surgery during different phases of the menstrual cycle. HER2 overexpression was found to fluctuate in hormone receptor-positive tumors. In actual fact, 20% of the tumors removed during the follicular phase scored HER2-positive, versus 8% of those removed during the luteal phase. Similarly, a number of hormone receptor-positive tumor specimens, obtained from the same patients during follicular and luteal phases, were scored HER2-positive when the sample was removed during the follicular phase and HER2-negative when removed in the luteal phase. Southern blot analysis of the HER2 gene indicated that, in hormone receptor-positive cases, the overexpression of HER2 is often not associated with gene amplification. The finding that overexpression of the HER2 gene, associated with tumor aggressiveness, can fluctuate according to the hormonal milieu may explain the increased survival of patients operated during the luteal phase. It is also relevant to the selection and treatment of patients most likely to benefit from anti-HER2 antibody therapy.

High level antibody response to retrovirus-associated but not to melanocyte lineage-specific antigens in mice protected against B16 melanoma

Mice vaccinated with Mycobacterium tuberculosis Ag38 gene-transduced B16 melanoma cells showed significant protection from intravenous challenge with parental B16 melanoma cells. No cytotoxic T-cell activity was found against melanoma cells, although the endogenous presence of the mycobacterial gene induced a preferential Th1 response. After immunization, a low serological response against melanoma cells was detected, while a high titer of antibodies directed to parental B16 cells, mainly of IgG2(a) isotype, was found in protected mice after challenge. These antibodies exhibited complement-dependent cytotoxicity against melanoma cells in vitro, while in vivo, used in passive immunization, they induced a decrease in a number of experimental B16 lung metastases. Most of the antibodies were directed against endogenous murine leukemia viruses. No reactivity against melanocyte lineage-specific antigens was observed. In particular, no reactivity was found in sera from protected mice against tyrosinase-related protein 2 (TRP-2), either stably expressed in a non-melanoma cell line or obtained by in vitro transcription-translation, or against tyrosinase, TRP-1 and gp100 antigens immunoprecipitated from B16 cells. Thus, in the B16 murine model, the presence of dominant viral antigens induces a very strong humoral response that might be protective and may inhibit or mask the presence of minor clonotypes.

Correlation between tumor vascularity, vascular endothelial growth factor production by tumor cells, serum vascular endothelial growth factor levels, and serum angiogenic activity in patients with breast carcinoma

Angiogenesis is an important prognostic factor in invasive breast carcinoma. We analyzed sera and tumor samples from 36 patients with primary breast carcinomas to determine the relationship between tumor vascularity, vascular endothelial growth factor (VEGF) production by tumor cells, levels of circulating VEGF (measured by ELISA assay), and levels of endothelial growth factors analyzed by a functional test of human umbilical vein endothelial cells (HUVEC) proliferation. Tumor vascularity was correlated directly with VEGF production by the tumor, indicating that VEGF production is a relevant factor in determining angiogenesis in primary tumor. No correlation was found either between the number of vessels in the tumor or the production of VEGF by tumor cells and the levels of serum angiogenic factors including VEGF. On the contrary, the two serum tests correlated together because a high serum level of VEGF is more frequent in cases with the presence of HUVEC-stimulating growth factors. These data indicate that the principal source of factors stimulating angiogenesis in the primary tumor is the tumor itself. This is an important issue in the context of anti-angiogenic therapeutic approaches, which should be planned to interfere with tumor production of angiogenic factors rather than with circulating angiogenic factors. In conclusion, whereas the vessel count and VEGF production by tumor cells are parameters that give direct information on tumor angiogenesis, long-term follow-up is necessary to determine the clinical significance of the determination of serum HUVEC-stimulating factors in the progression of breast carcinoma.

Pathobiologic identification of two distinct breast carcinoma subsets with diverging clinical behaviors

Many different pathological and biological variables which characterize breast carcinomas have been found to be associated. The aim of this work was to analyze the complex relationship among these parameters. The pathologic, biologic, and clinical characteristics of a series of primary breast carcinomas from 676 patients were retrospectively investigated. Multiple correspondence analysis of 13 factors revealed clustering of eight pathobiologic variables, that is histologic grade, necrosis, lymphoid infiltration, number of mitoses, c-erbB-2 overexpression, p53, progesterone receptor, and bcl2 expression. An index for each tumor calculated on the basis of these eight factors served to distinguish two different tumor phenotypes, designated A and B. Phenotype A is represented by tumors sharing most of the biologic features of normal breast tissues: indeed, these tumors are characterized by a relatively high degree of differentiation, low proliferation, no necrosis or leukocyte infiltration, and no gene alterations. By contrast, phenotype B is quite divergent from the normal tissue because of its poor differentiation, high proliferation, frequent gene alterations and evidence of a host immune reaction. As regards the disease progression, these two subsets showed marked differences: phenotype A tumors had a low recurrence rate per year that remained constant over time and affected more frequently elderly patients, whereas group B tumors showed high aggressivity in the first years after surgery followed by a low long-term recurrence rate and were more frequently seen in younger patients. These data suggest that breast carcinoma consists of two different subsets that can be identified on the basis of pathobiologic features.

The 67 kDa laminin receptor as a prognostic factor in human cancer

Different receptors for adhesion molecules, including the monomeric 67 kDa laminin receptor (67LR), are responsible for the interactions between tumor cells and components of the extracellular matrix that play an important role in tumor invasion and metastasis. Clinical data clearly demonstrate the importance of the 67LR in the progression of a wide variety of tumors, including breast, lung, ovary, and prostate carcinomas and lymphomas. Indeed, data on more than 4000 cases of different tumors from different organs studied by immunohistochemistry are all concordant with a role for the 67LR in invasiveness, metastasis, and even tumor growth. This receptor molecule appears to be unusual since the corresponding full-length gene encodes a 37 kDa precursor protein which, after acylation, dimerizes to generate the mature 67 kDa form. The primary function of the membrane receptor is to stabilize the binding of laminin to cell surface integrins, acting as an integrin-accessory molecule, although homology of the gene encoding the receptor precursor with other genes suggests additional functions. Studies conducted to define the structure, expression, and function of this laminin receptor represent a step toward developing therapeutic strategies that target this molecule. In particular, therapeutic approaches that downregulate expression of the receptor on tumor cells might lead to decreased tumor aggressiveness.

Absence of microsatellite instability in breast carcinomas with both p53 and c-erbB-2 alterations

Based on a previous finding that amplification of the c-erbB-2 oncogene and alteration of p53 are strongly associated in most aggressive breast tumours, the present study investigated whether microsatellite instability (MI) might also be associated with this tumour phenotype. Nine polymorphic microsatellite markers, including six dinucleotide, one trinucleotide, and two tetranucleotide repeats, were amplified from paired normal and tumour DNA samples of 15 breast tumours that overexpressed both c-erbB-2 and p53 and of 15 control breast tumours that overexpressed neither protein. All 30 breast tumours analysed exhibited a replication error-negative phenotype, with only one sample showing MI in one of the nine loci. This suggests that the genetic events underlying MI, which are critical in colorectal and gastric tumours, are not involved in the pathogenesis of c-erbB-2/p53 double-altered breast tumours and do not play a central role in breast tumour formation.

Level of anti-mouse-antibody response induced by bi-specific monoclonal antibody OC/TR in ovarian-carcinoma patients is associated with longer survival

More than 60% of cancer patients injected with intact murine monoclonal antibody (MAb) develop a humoral response against the antigen even after a single dose. Analysis of a series of 35 ovarian-cancer patients entered in phase-I and -II clinical studies of T-cells retargeted with the bi-specific F(ab')2 OC/TR revealed: (i) a detectable human anti-mouse antibody (HAMA) response in 31/35 (88%) patients, with high HAMA levels (> or = 150 ng/ml) in 18/31 (58%) cases by the end of the treatment; (ii) no correlation between HAMA levels and the form of delivery of the mAb (OC/TR bound to T cells or bound plus soluble), time schedule or cumulative dose; (iii) an association between high HAMA levels and favorable clinical parameters and response to immunotherapy; and (iv) a significantly longer median survival probability in patients with high HAMA levels than in patients with lower HAMA levels, even when the sub-group of non-responder patients was considered. Evaluation of the anti-idiotypic response in HAMA-positive sera indicated that 11/17 sera showed high-titer (>6000) binding of OC/TR, as evaluated by a specific radioimmunoassay, and 15/18 and 16/16 sera specifically inhibited the binding of the MOv18 and anti-CD3 parental MAbs to ovarian-carcinoma cells and T lymphocytes respectively. Of 7 patients evaluated for duration of the HAMA response, 5 showed stable or even increased HAMA levels. The long-lasting HAMA response maintained an anti-idiotypic component, directed mainly against the alphaCD3 idiotype of bi-MAb OC/TR in 2 out of 3 cases tested.

Inhibition of fibronectin-activated migration of microvascular endothelial cells by interleukin-1alpha, tumour necrosis factor alpha and interferon gamma

The effect of interferon gamma (IFN) and the inflammatory cytokines tumour necrosis factor alpha (TNF) and interleukin 1alpha (IL-1) on micro- and macrovascular endothelial cell (EC) proliferation and migration was analysed. Whereas both micro- and macrovascular EC were growth-inhibited in response to the aforementioned cytokines, only microvascular EC were sensitive to TNF, IL-1 and IFN as inhibitors of fibronectin-activated cell migration. In addition, because microvascular EC play a crucial role in angiogenesis, and the formation of new capillaries depends upon the presence of angiogenic polypeptides, we evaluated the synthesis of fibroblast growth factor (FGF) type 1 and 2, Vascular Endothelial Growth Factor (VEGF) and Hepatocyte Growth Factor (HGF) in our system. Both micro- and macrovascular EC produce large amounts of FGF-2, which is mainly localized in the nucleus, and almost undetectable levels of FGF-1. In addition, the two cell types synthesize notable levels of VEGF and no HGF. Whether these findings are relevant to the different in vivo functions of EC residing different districts remains the focus of additional studies.

Ectopic expression of pRb2/p130 suppresses the tumorigenicity of the c-erbB-2-overexpressing SKOV3 tumor cell line

We investigated the in vitro and in vivo effects of the ectopic expression of the pRb2/p130 cell cycle regulator on c-erbB-2-associated tumorigenicity. SKOV3 ovarian cancer cells, which display c-erbB-2 gene amplification and oncoprotein (p185HER2) overexpression, were stably transfected with a plasmid containing the coding sequence for human wild-type pRb2/p130 (wtRb2), or with pcDNA3 empty vector. Three wtRb2-transfected clones (cl. 24, ci. 49, cl. 100) and one empty vector-transfected clone (cl. mock) were randomly picked and further analysed. Western blot analysis revealed high levels of pRb2/p130 in the three clones compared to mock cells. Levels of p185HER2 and the extent of its tyrosine phosphorylation were similar in all transfectant clones, as were levels of pRb1 and p107. In anchorage-independent growth assays, the number of colonies from wtRb2 clone-transfectants was about 90% less than that arising from mock cells (P<0.001). Tumor take rates of the three wtRb2-transfected clones xenografted in nu/nu mice were much lower than those of mock cells, and tumor volume was decreased by 80% (P<0.001). A mutant version of pRb2/p130 deleted of the pocket region (mut-Rb2) was also transfected into SKOV3 cells and studied in parallel with the wtRb2-transfected and pcDNA empty vector-transfected bulk populations. mut-Rb2 transfected cells showed no inhibition of in vitro colony formation and were fully tumorigenic. Together, these findings indicate that Rb2 acts as a tumor suppressor gene in vivo and in vitro in SKOV3 cells and that the intact pocket region is required for the suppressor activity.

Molecular requirements for attachment of the glycosylphosphatidylinositol anchor to the human alpha folate receptor

The alpha isoform of the folate receptor (FR) is a 38-KDa glycosylphosphatidylinositol (GPI) protein which mediates the internalization of folates. The FR amino acid sequence has features typical of GPI-linked proteins, including the presence of a hydrophobic carboxyl-terminus, a hinge region, and a stretch of small and uncharged amino acids. Substitution of predicted cleavage/attachment Ser234 with arginine or threonine, or replacement of Gly235 with proline by site-directed mutagenesis had no effect on GPI processing. In fact, CHO cells transfected with each of the three cDNA variants or with FR wild-type showed comparable amounts of phosphatidylinositol-specific phospholipase C-resistant FR in double-determinant radioimmunoassay. Western blot analysis of total cell lysates from all transfectants consistently revealed the 38-KDa FR band. Deletion of residues 233-237 in the amino-terminal portion of the FR cDNA constructs derived by a polymerase chain reaction strategy abrogated GPI processing, with only a small proportion of the FR remaining in the cytoplasm in four of the five clones tested. This finding suggests that FR residues 233-237 are essential in properly juxtaposing the FR hydrophobic domain. Together, these data support the hypothesis that the postulated Ser234 is not the only potential cleavage/attachment site of the alpha isoform of FR.

Transfer of chimeric receptor gene made of variable regions of tumor-specific antibody confers anticarbohydrate specificity on T cells

The antitumor specificity of T cells can be induced by gene transfer using a recently developed therapeutic approach (T body). In this work, we genetically conferred anticarbohydrate specificity onto T cells using the variable regions of monoclonal antibody MLuC1, which binds the Lewis(Y) (LeY) tumor-associated antigen that is overexpressed on several human carcinomas. The variable regions of MLuC1, which are in a single-chain Fv (ScFv) configuration, were cloned and spliced in a eukaryotic expression vector with both the gene encoding the signal-transducing gamma-chain of the human Fcgamma receptor and a flexible hinge domain. The chimeric ScFv-gamma gene was expressed in a murine cytotoxic T-cell hybridoma. Transfectants receiving vector only served as a negative control (mock). Screening for functional transfectants was carried out using a tumor growth inhibition assay. The soluble form of MLuC1 ScFv was recovered from bacteria periplasm and tested for binding to LeY-expressing cells by the fluorescence-activated cell sorter analysis. Despite the low binding ability of the soluble MLuC1 ScFv, 7 of 13 genetically engineered cytotoxic T lymphocyte clones inhibited the growth of LeY-positive cells and did not affect growth of LeY-negative cells. None of the mock clones tested specifically inhibited tumor growth. These data indicate that, by chimeric MLuC1 ScFv-gamma gene transfer, it is possible to confer anticarbohydrate specificity onto T cells and extend the applicability of the T-body approach to tumor-associated antigens that are naturally not recognized by T cells.

The 67-kDa laminin receptor originated from a ribosomal protein that acquired a dual function during evolution

The 67-kDa laminin receptor (67LR) is a nonintegrin cell surface receptor that mediates high-affinity interactions between cells and laminin. Overexpression of this protein in tumor cells has been related to tumor invasion and metastasis. Thus far, only a full-length gene encoding a 37-kDa precursor protein (37LRP) has been isolated. The finding that the cDNA for the 37LRP is virtually identical to a cDNA encoding the ribosomal protein p40 has suggested that 37LRP is actually a component of the translational machinery, with no laminin-binding activity. On the other hand, a peptide of 20 amino acids deduced from the sequence of 37LR/p40 was shown to exhibit high laminin-binding activity. The evolutionary relationship between 23 sequences of 37LRP/p40 proteins was analyzed. This phylogenetic analysis indicated that all of the protein sequences derive from orthologous genes and that the 37LRP is indeed a ribosomal protein that acquired the novel function of laminin receptor during evolution. The evolutionary analysis of the sequence identified as the laminin-binding site in the human protein suggested that the acquisition of the laminin-binding capability is linked to the palindromic sequence LMWWML, which appeared during evolution concomitantly with laminin.

Increased expression of c-erbB-2 in hormone-dependent breast cancer cells inhibits cell growth and induces differentiation

c-erbB-2, a member of the tyrosine kinase oncogene family, is overexpressed in about 30% of human breast tumors where it correlates with poor prognosis. In vitro studies have suggested that increased expression of the receptor plays an important role in malignant progression. To better understand the direct effects of p185HER2 overexpression, a human c-erbB-2 expression vector was transfected into the hormone-dependent MCF-7 human breast carcinoma cell line and cell growth was analysed. Unexpectedly, colony formation assay revealed a reduction in the number and size of colonies as compared with mock-transfected cells. In hormone-deprived medium, c-erbB-2 transfected cells acquired growth capability, consistent with previous reports. By contrast, two c-erbB-2-transfected clones grown in complete medium showed a reduced proliferation rate despite the activation of a fully functional oncoprotein capable of autophosphorylation and induction of the MAPK pathway. The number of c-erbB-2-overexpressing cells in the S phase of the cell cycle was about one-half the number of control and mock-transfected cells. Also, overexpression of c-erbB-2 induced overexpression of p21WAF1, pRB hypophosphorylation and a mature differentiated cell phenotype with production of lipid droplets. Functional inactivation of p185HER2 by means of a specific single chain antibody indicated the c-erbB-2-dependence of the observed alterations. These data show that the exogenous overexpression of the c-erbB-2 gene in hormone-dependent breast cancer cells inhibits proliferation and induces differentiation.

Formation of the 67-kDa laminin receptor by acylation of the precursor

Even though the involvement of the 67-kDa laminin receptor (67LR) in tumor invasiveness has been clearly demonstrated, its molecular structure remains an open problem, since only a full-length gene encoding a 37-kDa precursor protein (37LRP) has been isolated so far. A pool of recently obtained monoclonal antibodies directed against the recombinant 37LRP molecule was used to investigate the processing that leads to the formation of the 67-kDa molecule. In soluble extracts of A431 human carcinoma cells, these reagents recognize the precursor molecule as well as the mature 67LR and a 120-kDa molecule. The recovery of these proteins was found to be strikingly dependent upon the cell solubilization conditions: the 67LR is soluble in NP-40-lysis buffer whereas the 37LRP is NP-40-insoluble. Inhibition of 67LR formation by cerulenin indicates that acylation is involved in the processing of the receptor. It is likely a palmitoylation process, as indicated by sensitivity of NP-40-soluble extracts to hydroxylamine treatment. Immunoblotting assays performed with a polyclonal serum directed against galectin3 showed that both the 67- and the 120-kDa proteins carry galectin3 epitopes whereas the 37LRP does not. These data suggest that the 67LR is a heterodimer stabilized by strong intramolecular hydrophobic interactions, carried by fatty acids bound to the 37LRP and to a galectin3 cross-reacting molecule.

Evaluation of the balance between angiogenic and antiangiogenic circulating factors in patients with breast and gastrointestinal cancers

Angiogenesis is a critical determinant of tumor growth. Tumor cells produce or induce angiogenic molecules that act specifically on endothelial cells (ECs) but also release angiostatic molecules. Thus, tumor angiogenesis represents a net balance between positive and negative regulators of neovascularization. Sera from patients with breast or gastrointestinal cancers were evaluated for their capacity to selectively modulate the proliferation of human umbilical vein ECs; sera from 15 of 78 (19%) breast cancer patients and 8 of 53 (15%) gastrointestinal cancer patients induced human umbilical vein EC growth, whereas sera from 4 of 78 (5%) breast cancer patients and 1 of 53 (2%) gastrointestinal cancer patients inhibited EC proliferation. Growth-stimulatory sera were significantly more frequent among postmenopausal (14 of 53) than premenopausal (1 of 25) breast cancer patients; inhibitory activity was observed in 3 of 25 premenopausal patients versus 1 of 53 postmenopausal individuals. The half-life of serum-stimulating and -inhibiting factors seemed to differ, because stimulatory activity but not inhibitory activity was decreased at 5 days after surgery. The levels of vascular endothelial growth factor were elevated in about 45% of patients with growth-stimulatory sera, whereas the serum inhibition of EC growth was found to be due, at least in part, to high levels of soluble thrombospondin.

Role of cross-linking agents in determining the biochemical and pharmacokinetic properties of Mgr6-clavin immunotoxins

Several immunotoxins (ITs) were synthesized by the attachment of clavin, a recombinant toxic protein derived from Aspergillus clavatus, to the monoclonal antibody Mgr6 that recognizes an epitope of the gp185(HER-2) extracellular domain expressed on breast and ovarian carcinoma cells. Conjugation and purification parameters were analyzed in an effort to optimize the antitumor activity and stability of the ITs in vivo. To modulate the in vitro and in vivo properties of the immunotoxins, different coupling procedures were used and both disulfide and thioether linkages were obtained. Unhindered and hindered disulfide with a methyl group linkage ethyl S-acetyl 3-mercaptopropionthioimidate ester hydrochloride (AMPT) or ethyl S-acetyl 3-mercaptobutyrothioimidate ester hydrochloride (M-AMPT) were obtained by reaction with recombinant clavin, while the monoclonal antibody Mgr6 was derivatized with ethyl 3-[(4-carboxamidophenyl)dithio]propionthioimidate ester hydrochloride (CDPT). To achieve higher hindrance (a disulfide bond with a geminal dimethyl group), Mgr6 was derivatized with the N-hydroxysuccinimidyl 3-methyl-3-(acetylthio)butanoate (SAMBA) and clavin with CDPT. To evaluate the relevance of the disulfide bond in the potency and pharmacokinetic behavior of the ITs, a conjugate consisting of a stable thioether bond was also prepared by derivatizing Mgr6 with the N-hydroxysuccinimidyl ester of iodoacetic acid (SIA) and clavin with AMPT. The immunotoxins were purified and characterized using a single-step chromatographic procedure. Specificity and cytotoxicity were assayed on target and unrelated cell lines. The data indicate that the introduction of a hindered disulfide linkage into ITs has little or no effect on antitumor activity and suggest that disulfide cleavage is essential for activity; indeed, the intracellularly unbreakable thioether linkage produced an inactive IT. Analysis of IT stability in vitro showed that the release of mAb by incubation with glutathione is proportional to the presence of methyl groups and increases exponentially with the increase in steric hindrance. Analysis of the pharmacokinetic behavior of ITs in Balb/c mice given intravenous bolus injections indicated that ITs with higher in vitro stability were eliminated more slowly; i.e., the disulfide bearing a methyl group doubled the beta-phase half-life (from 3.5 to 7.1 h) compared with that of the unhindered, while a geminal dimethyl protection increased the elimination phase to 24 h. The thioether linkage showed its intrinsic stability with a beta-phase half-life of 46 h. The thioether linkage also increased the distribution phase from 17 to 32 min. The in vitro characteristics and in vivo stability of Mgr6-clavin conjugates composed of a methyl and dimethyl steric hindered disulfide suggest clinical usefulness.

Panning phage antibody libraries on cells: isolation of human Fab fragments against ovarian carcinoma using guided selection

The display of repertoires of human antibody (Ab) fragments on filamentous phages and selection by binding of the phage to antigen (Ag) have provided a ready means of deriving human Ab against purified Ag. However, it has been more difficult to obtain phage Ab against an individual Ag of a complex mixture, such as cell surface Ag. Using the technique of "guided selection," we generated human Ab against the high-affinity folate-binding protein (FBP), a cell surface Ag that is overexpressed in many human ovarian carcinomas. The guiding Ab template was provided by the light chain of mouse monoclonal Ab Mov19 (K[aff], 10[8] M[-1]) directed against FBP; this was paired with repertoires of human heavy chains displayed on phages, and the hybrid Ab fragments were selected by binding to an ovarian carcinoma cell line (OVCAR3). The selected human heavy chains were then paired with repertoires of human light chains. Further panning led to the isolation of a human Fab fragment, C4, with a binding affinity of 0.2 x 10(8) M(-1). This was highly specific for FBP, as demonstrated by ELISA and flow cytometry data and by immunoprecipitation of the relevant molecule from the cell surface of ovarian carcinoma cells. Moreover, C4 targeted the same or a closely related epitope of the Ag, as did the template rodent monoclonal Ab Mov19. These results suggest the usefulness of guided selection as a simple means to deriving human Ab against cell surface Ag for which a rodent Ab is available.