Biomedical subjects

D M Goldenberg

Publications and source records attributed to D M Goldenberg.

At least 145 records · Page 8Linked to original sources

PubMed1994

Processing of antibody-radioisotope conjugates after binding to the surface of tumor cells.

BACKGROUND: Previous experiments indicated that most antibodies binding to cell surface antigens are internalized gradually and degraded within lysosomes, with a half-life of degradation of approximately 1 day, for most antibodies. The research discussed in this article extended our studies to eight additional antibodies reacting with six different antigens, including three antigens anchored in the membrane by glycosyl-phosphatidylinositol. The authors also tested antibodies labeled with 111indium, as well as 125iodine, to determine whether different radiolabels would be processed differently. METHODS: Antibodies were radiolabeled with 125I or with 111In bound to benzyl-DTPA. After binding to the surface of tumor cells in vitro, excess antibody was washed away, and the fate of the radiolabel was investigated over periods of 3-7 days. Radiolabel released into the supernatant or retained by the cells was analyzed to determine whether it was still on intact antibody. RESULTS: In 13 of the 15 antibodies that were tested, a similar pattern of irreversible binding and gradual catabolism was observed. Iodine conjugated to antibodies was released rapidly from the cell after antibody catabolism. In contrast, the 111In was retained within the cell much longer than 125I, with the rate of degradation and release into the medium being at least fivefold slower. More than 50% of the bound 111In was still present on the cells after 7 days. Biochemical analysis of the retained 111In extracted cells after 4-6 days demonstrated that it was no longer associated with antibodies and was in a low molecular weight form, probably still associated with the chelator benzyl-DTPA. CONCLUSIONS: Different radiolabels are processed by tumor cells differently, after catabolism of the antibody to which they originally were conjugated. The data suggest that the prolonged retention of 111In, relative to that of 125I, is due not to deiodination of iodine conjugates, but rather to intracellular retention of catabolic products containing 111In, perhaps within lysosomes. The use of radioisotopes that are retained within cells after antibody internalization and degradation may improve both radioimmunodetection and radioimmunotherapy of cancer.

Antibodies, Monoclonal↗

PubMed1994

Comparative biodistribution and radioimmunotherapy of monoclonal antibody RS7 and its F(ab')2 in nude mice bearing human tumor xenografts.

BACKGROUND: RS7 is a murine monoclonal antibody immunoglobulin G1 with pan-carcinoma reactivity, which was raised against human squamous cell carcinoma of the lung. To optimize the use of monoclonal antibody RS7 as a carrier of radionuclides for tumor targeting and therapeutic applications, whole RS7 immunoglobulin G and its F(ab')2 fragment were radiolabeled, and their biodistribution and effectiveness as radioimmunotherapeutic agents in nude mice bearing established human tumor xenografts were evaluated. The contributions of the tumor model, monoclonal antibody form (fragment vs. intact), radioisotope (131I, 111In, 90Y, and 188Re), and antigen target were evaluated. METHODS: Cumulative absorbed radiation doses were calculated from biodistribution data, and doses were normalized to blood to estimate expected relative toxicities. Two tumor models expressing different levels of RS7-antigen were studied: ME180, a cervical carcinoma cell line, and Calu-3, an adenocarcinoma of the lung cell line. In addition, the therapeutic effectiveness of 131I-RS7-F(ab')2 was compared to that of 131I-RS7-IgG. RESULTS AND CONCLUSIONS: Doses delivered to tumor (normalized to blood) calculated for 131I-RS7-F(ab')2 and 90Y-RS7-IgG were 4.7 times and 1.8 times greater, respectively, than 131I-RS7-IgG, and therefore would be expected to yield greater therapeutic efficacy when equitoxic doses are administered. This expectation was confirmed in the radioimmunotherapy study with 131I-RS7-F(ab')2. At equivalent absorbed dose to tumor, 131I-RS7-F(ab')2 was found to effect a slightly longer suppression of tumor growth than the intact 131I-RS7 IgG, and a 50% dose escalation yielded tumor regression for a prolonged period with the fragment, whereas a similar 50% dose escalation with 131I-RS7-IgG could not be tolerated.

Adenocarcinoma↗

PubMed1994

Phase I clinical evaluation of a new murine monoclonal antibody (Mu-9) against colon-specific antigen-p for targeting gastrointestinal carcinomas.

BACKGROUND: Colon-specific antigen-p is a tumor-associated antigen present in approximately 60% of colorectal cancers. Preclinical studies have shown that the murine monoclonal antibody Mu-9 has excellent tumor-targeting abilities; therefore, clinical studies were initiated. METHODS: The immunoglobulin G and F(ab')2 were radiolabeled with 131I and administered to 13 and 12 patients, respectively, with advanced gastrointestinal cancer (colon, rectal, and pancreatic) for radioimmunodetection or radioimmunotherapy. RESULTS: Even in patients with highly elevated carcinoembryonic antigen levels, only one patient showed appreciable complexation of the labeled antibody, suggesting the epitope may not be highly expressed in the blood. Fifty percent of 131I-Mu-9 immunoglobulin G was cleared from the blood within 41 +/- 13 hours, while it took only 19 +/- 8 hours for the same amount of 131I-F(ab')2 to be cleared from the blood. Lesion detection in the abdomen, liver, and pelvis was greater than 90% for either the immunoglobulin G or F(ab')2. The dose absorbed by the normal organs, except the kidneys, was two- to threefold less for the F(ab')2 than for the whole immunoglobulin G. The dose to the kidneys was similar for both forms of immunoglobulin. The average tumor dose for 131I-Mu-9 immunoglobulin G was 13.9 +/- 11.0 cGy/mCi, and for 131I-F(ab')2 was 4.9 +/- 2.9. Tumor/red marrow dose ratios for the whole immunoglobulin G were 4.3 +/- 3.0, compared to 3.3 +/- 1.9 for the F(ab')2, suggesting the therapeutic window for the two forms of immunoglobulin may be similar. Eight of nine patients given the whole immunoglobulin G developed highly elevated levels of human anti-mouse antibody, whereas lower values were observed in five of seven patients given the F(ab')2. CONCLUSIONS: These initial results support the need for further evaluation of Mu-9 immunoglobulin G and F(ab')2 for targeting gastrointestinal cancer for radioimmunotherapy.

Adult↗

PubMed1994

Radioimmunodetection of non-small cell lung cancer using technetium-99m-anticarcinoembryonic antigen IMMU-4 Fab' fragment. Preliminary results.

BACKGROUND: Although computed tomography and magnetic resonance imaging have improved the staging and evaluation of non-small cell lung cancer (NSCLC), mediastinal staging lacks adequate specificity and sensitivity. Radioimmunodetection may augment computed tomography and magnetic resonance imaging. The authors evaluated the ability of the technetium 99m-anticarcinoembryonic antigen IMMU-4 Fab' fragment to localize NSCLC in vivo, measured its pharmacokinetics, and estimated its radiation dose. METHODS: Seventeen patients with carcinoembryonic antigen-positive NSCLC received 16-30 mCi of technetium 99m IMMU-4 Fab'. Planar imaging was performed at 1-7 hours and 20-24 hours. Single-photon emission computed tomography (SPECT) was performed within 8 hours after injection. In 10 patients, blood sampling, urine collection, and quantitative imaging were performed to determine blood and urine pharmacokinetics and radiation dose estimates. Human anti-mouse antibody response was measured for as long as 3 months after administration. RESULTS: Planar and/or SPECT imaging detected 72% of 32 known lesions. SPECT was more sensitive than planar imaging. T1/2 alpha averaged 0.18 +/- 0.33 hours; T1/2 beta averaged 8.02 +/- 5.53 hours. The mean concentration versus time value was 1.11 +/- 0.56 mg.h. The average whole body dose estimated for administration of 30 mCi was 0.45 +/- 0.08 rads. No human anti-mouse antibody responses were detected. CONCLUSION: The tumor detection rate was high, but the persistent blood pool at < 8 hours complicated image interpretation. An intermediate imaging time point (12-16 hours) might be preferable. SPECT is an important adjunct to imaging with this radioimmunoconjugate. The acceptable dosimetry estimated for 30 mCi Technetium 99m IMMU-4 Fab' and the lack of human anti-mouse antibody responses suggest this is a promising localizing tool for NSCLC:

Antibodies, Monoclonal↗

PubMed1994

Initial clinical results with technetium-99m-labeled LL2 monoclonal antibody fragment in the radioimmunodetection of B-cell lymphomas.

BACKGROUND: Various monoclonal antibodies (MoAb) labeled with Iodine-131 or Indium-111 (In-111) have been investigated for radioimmunodetection of Hodgkin's and non-Hodgkin's lymphomas. Successful radioimmunotherapy also has been reported. The purpose of this pilot study was to stage non-Hodgkin's B-cell lymphomas (NHL) using whole body scintigraphy with technetium-99m (Tc-99m)-labeled murine monoclonal antibody LL2 (EPB-2) Fab' (Immunomedics, Morris Plains, NJ). Others have shown this MoAb to have specific binding to B-cell lymphomas by flow cytometry and immunofluorescence. Initial clinical studies by others have demonstrated targeting of NHL with the Tc-99m-labeled LL2-Fab'. METHODS: One milligram of the antibody was injected intravenously after being radiolabeled with 30 mCi Tc-99m. Fifteen patients with high (n = 6), low (n = 2), and intermediate (n = 7) grade NHL were studied. No adverse effects were noted. Planar whole body imaging and single-photon emission computed tomography were performed at 2-6 h and 20-24 h postinjection. Human anti-mouse antibody levels were determined before injection and at 2 and 6 weeks. RESULTS: In 4 of 15 patients (27%), the disease stage was altered in response to the scintigraphic findings. The physiologic biodistribution of the antibody demonstrated splenic uptake caused by antibody targeting of the white pulp and of normal B-cells, and renal uptake caused by urinary excretion. Lymph node and bone marrow involvement of known tumor sites were clearly seen. A number of previously unknown tumor sites were revealed by LL2-radioimmunodetection despite normal morphologic imaging results. Long-term follow-up of these patients is required to verify these findings. No human anti-mouse antibody elevations or adverse reactions were found in the patients studied. CONCLUSION: These preliminary data suggest that Tc-99m-labeled LL2 Fab' yields useful clinical results, especially for the staging of patients with NHL before initial therapy or for the detection of early disease recurrence.

Animals↗

PubMed1994

Comparison of equitoxic radioimmunotherapy and chemotherapy in the treatment of human colonic cancer xenografts.

The therapeutic efficacy of 5-fluorouracil (5-FUra; 0.6 mg/day x 5 days) + leucovorin (LV; 1.8 mg/day x 5 days) and of 131I-labeled MN-14 anticarcinoembryonic antigen IgG (275 microCi single dose) was evaluated in size-matched (0.3-0.7 cm3) s.c. LoVo, HT-29, DLD-1, HCT-15, LS174T, and MOSER, GW-39, and WidR human colonic tumors. These lines express varying amounts of carcinoembryonic antigen and exhibit varying degrees of in vitro responsiveness to 5-FUra. Unlike radioimmunotherapy (RAIT), multiple cycles of chemotherapy were feasible over a 3-week period. However, no therapeutic advantage to a second cycle of 5-FUra/LV administration was found. Therefore, it is reasonable to compare single cycles of both treatment modalities. RAIT was statistically more effective in 5 of 8 tumor lines (LoVo, LS174T, MOSER, WidR, and GW-39). In 1 other line (DLD-1), RAIT was marginally more efficacious, but tumors responded well to both therapies. The lack of a statistical difference between the 2 modalities of treatment may indicate that the efficacy of the 2 treatments is equivalent, or the relatively large variability within the treatment groups may have prevented significance given the number of animals evaluated. RAIT and 5-FUra/LV were equally efficacious in the HT-29 and the HCT-15 tumor lines. Of the 5 xenografts that responded better to RAIT, 3 lines (LS174T, GW-39, and WidR) demonstrated a greater percentage of tumors responding over a 5- to 6-week period. The other 3 lines (LoVo, MOSER, and DLD-1) exhibited a similar percent of tumors responding to both therapies, but a greater growth inhibition in those RAIT-treated tumors that responded. In vitro responsiveness to 5-FUra/LV did not directly correlate with in vivo responsiveness (r2 = -0.664), since LS174T and LoVo tumors, with rapid growth rates (0.05-0.36 cm3/day), were not highly responsive to therapy. Growth inhibition from RAIT also did not correlate with total tumor carcinoembryonic antigen content (r2 = 0.003), an observation that may be due to additional variables, such as accessibility of antigen and innate radiosensitivity of the tumor. RAIT was most effective in the fastest growing tumor lines (LS174T, GW-39, MOSER, WidR, and LoVo). These preclinical results suggest an advantage to radioantibody therapy over one of the most commonly used forms of chemotherapy to treat colorectal cancer. These studies also highlight the need to establish criteria that will enable the selection of therapeutic modalities in patients.

Animals↗

PubMed1994

Characterization of cluster 13: the epithelial/carcinoma antigen recognized by MAb RS7.

Cluster 13 was defined by 2 independently derived murine monoclonal antibodies (MAbs), RS7 (IgG1) and MR54 (IgG2a), which were raised against human squamous-cell carcinoma of the lung and a human ovarian-carcinoma cell line, respectively. Immunologic and biochemical evidence demonstrated that RS7 and MR54, as well as 2 additional MAbs, MR6 (IgG2a) and MR23 (IgG1), generated in the same fusion as MR54, recognize the same antigen, a 46- to 48-kDa glycoprotein. Evaluation of the expression of antigen on the surface of tumor cell lines, Western blotting analyses, competitive binding studies, and double-determinant ELISA assays, support this conclusion. Two distinct epitopes are defined by these MAbs. In order to further characterize this antigen, amino-acid-sequence analyses were performed on peptides derived from antigen purified by affinity chromatography with MAb RS7. The sequence data obtained from 2 peptides, which were independently generated by CNBr cleavage and trypsin digestion respectively indicated identity to GA733-1. The GA733-1 genomic DNA sequence predicted a type-1 membrane protein of 35 kDa, with 4 potential N-linked glycosylation sites. The GA733-1 protein product has not been identified previously, and MAbs to this tumor-associated antigen were not previously known.

Amino Acid Sequence↗

PubMed1994

Internalization of an intact doxorubicin immunoconjugate.

An immunoconjugate between doxorubicin and anti-(carcinoembryonic antigen) (CEA) was prepared by using aminodextran (M(r) = 40,000) as the intermediate carrier, and the carbohydrate moiety of the antibody as the linking site. The resulting immunoconjugate was subjected to an in vitro evaluation for the internalization on the target cells (Lo Vo), and compared to that of unconjugated antibody, as well as the cellular uptake of unconjugated doxorubicin. The internalization was evaluated microscopically by following the translocation of the red fluorescence of doxorubicin and the green fluorescence of the fluorescein-isothiocyanate-labeled goat anti-(mouse Ig) antibody, which visualizes the location of the primary mouse antibody. Anti-CEA monoclonal antibody (NP-4) was found to internalize into Lo Vo cells. The immunoconjugate made with this antibody was similarly internalized, and the doxorubicin was found to distribute with the primary antibody. The cell surface and cytoplasm were the major compartments of their distribution. These results indicate that the drug molecules were indeed delivered into the cells by the antibody as an intact conjugate. Unconjugated doxorubicin, on the contrary, was quickly absorbed by the cells and concentrated in the nucleus within 30 min, and never showed a distribution in the cytoplasm or cell membrane as in the nucleus by this procedure. The intermediate drug conjugate, doxorubicin-dextran, did not show internalization. The internalization of NP-4 antibody (or the doxorubicin conjugate) was also confirmed by studying the intracellular catabolism of the cell-bound antibody (or conjugate). The release of the degraded antibody by the cells, as differentiated by trichloroacetic acid precipitation techniques, was considered an indication of internalization. Lysosomes were involved in the degradation, since the process was markedly inhibited in the presence of the lysosomal enzyme inhibitor, ammonium chloride.

Antibodies, Monoclonal↗

PubMed1994

Normal colonic epithelium adheres to carcinoembryonic antigen and type IV collagen.

BACKGROUND/AIMS: Human colorectal carcinoma cells bind to collagen and laminin in the basement membrane as well as to carcinoembryonic antigen (CEA) on neighboring cells. The purpose of this study was to determine whether normal colonic epithelial cells bind to CEA, collagen, or laminin. METHODS: Intact colonic crypts were isolated from normal mucosa in 13 specimens resected for colorectal carcinoma or colonic diverticulitis. Colonocytes were released from the crypts by treatment with collagenase and deoxyribonuclease and tested for adhesion to CEA, type IV collagen, and laminin in a solid-phase adhesion assay. RESULTS: Twelve percent to 25% of colonocytes in all specimens bound to CEA. Colonocytes from seven specimens also bound to type IV collagen, but none of the colonocyte preparations bound significantly to laminin. Monoclonal antibodies to CEA and to the hyaluronate receptor CD44 and enzymatic removal of membrane CEA blocked the adhesion of colonocytes to CEA. CONCLUSIONS: First, colonocytes use the same epitopes on CEA and CD44 as colorectal carcinoma cells to adhere to solid-phase CEA. Second, colonocytes bind to solid-phase CEA through CEA-to-CEA homophilic binding. Third, CEA and type IV collagen, but not laminin, are adhesion ligands for human colonocytes.

Antibodies↗

PubMed1994

Preparation of a pure 99mTc-F(ab')2 radioimmunoconjugate by direct labeling methods.

Intact IgG and Fab' can be labeled directly with 99mTc to give quantitative incorporation of radioactivity into the protein. With F(ab')2 the reductive conditions yield a mixture of 99mTc-F(ab')2 and 99mTc-Fab'. We now report a direct labeling method to produce only 99mTc-F(ab')2 in quantitative yield and contaminated with 99mTc-Fab'. The properties, stability and biodistribution of the 99mTc-F(ab')2 have been compared to 99mTc-Fab'. This new technology will allow us to compare technetium direct-labeled IgG, F(ab')2 and Fab' derivatives of the same antibody for radioimmunodetection.

Animals↗

PubMed1994

The use of monoclonal antibodies and antibody fragments in the imaging of infectious lesions.

The advantage of immunoscintigraphy over autologous leukocyte techniques in the imaging of infection is the simplicity of its use compared with techniques that require the isolation of autologous white blood cells. The advantage over 99mTc- or 111In-labeled nonspecific human immunoglobulin is the excellent target-to-background ratio, which results from an endogenous background subtraction with the whole antigranulocyte antibody (99mTc-anti-NCA-95; BW250/183) and a rapid clearance of the antibody using an antigranulocyte Fab'-fragment (99mTc-anti-NCA-90; IMMU-MN3). The whole antibody is helpful for imaging of soft tissue infections, peripheral bone, and abdominal infections. Problems may arise occasionally in regions with normal bone marrow that are caused by human antimouse antibody (HAMA) formation. An infection or the entire extent of inflammation can be proven or excluded only at 24 hours postinjection. In contrast, antigranulocyte Fab'-fragment may have its advantage in an earlier localization of infectious lesions (1 hour) owing to its smaller molecular size and its lower affinity for its epitope. This may be promising in the detection of spinal infections and in infections in regions with the presence of normal bone marrow. Also advantageous is the negligible HAMA response rate. Problems may arise in abdominal infections because of an intestinal excretion of activity as early as 4 hours postinjection in some cases but more usually at 24 hours.

Abdomen↗

PubMed1994

Chimerization of LL2, a rapidly internalizing antibody specific for B cell lymphoma.

LL2 is a murine monoclonal antibody (MAb) that has been shown to be effective for the diagnosis and treatment of patients with non-Hodgkin's B cell lymphoma. Studies have also shown that radiolabeled murine LL2 (mLL2) or mLL2 and fragments thereof coupled to Pseudomonas exotoxin (PE) can effectively target human B cell lymphoma in mice. We have obtained the DNA sequences encoding the VK and VH domains of mLL2, an IgG2a MAb, which were combined with their respective human kappa and IgG1 constant region domains and expressed in SP2/0 cells. Like its murine counterpart, the chimeric LL2 (cLL2) antibody is glycosylated in the light chain variable region. Chimerization did not interfere with the immunoreactivity of the antibody, as determined by a competitive binding assay, where either antibody shows equivalent inhibition of the binding of its counterpart to the Raji cell membrane surface antigen, CD22. Both antibodies bind and are rapidly internalized by Raji cells, whereas an irrelevant humanized antibody did not bind and was not internalized under similar conditions. The internalization rates of the bound murine or chimeric antibodies were nearly identical, with Ke values of 0.106 and 0.118 min-1 for mLL2 and cLL2, respectively. The observed close equivalence between the murine and chimeric antibodies suggests potential advantages of the latter as a less immunogenic agent. Studies are currently underway to evaluate the chimeric antibody as a potential therapeutic immunoconjugate.

Amino Acid Sequence↗

PubMed1994

Detection of soft-tissue infections and osteomyelitis using a technetium-99m-labeled anti-granulocyte monoclonal antibody fragment.

UNLABELLED: Imaging of osteomyelitis and soft-tissue infections can be problematic with currently available agents; bone scans are often false-positive. Indium-111-oxine and 99mTc-HMPAO white blood cell (WBC) scans require ex vivo handling of blood with potential exposure to infectious agents, and 99mTc-antigranulocyte (IgG1) antibodies need 24 hr for final diagnosis. METHODS: We investigated the use of 99mTc-murine anti-granulocyte monoclonal Fab' fragment in 20 patients with suspected osteomyelitis of soft-tissue infections. All patients also had 99mTc bone scans and 111In-oxine or 99mTc-HMPAO white blood cell scans. The final diagnosis was confirmed by culture, biopsy, surgery, follow-up, x-rays, CT or MRI. In vitro studies performed on granulocytes demonstrated no effect on their function when the anti-granulocyte monoclonal antibody fragment was added. RESULTS: Sensitivity, specificity and diagnostic accuracy to detect infection was 88%, 75% and 80%, respectively. All lesions could be detected as early as 1 hr after injection of the antibody fragment. In comparison, WBC scanning had values of 86%, 78% and 81%, respectively. Some lesions could only be detected 24 hr following the injection of labeled WBCs. LeukoScan had three false-positives and WBC scanning had two false-positives. CONCLUSIONS: Immunoscintigraphy with 99mTc-NCA-90 Fab' fragments offers rapid localization of foci, rapid and simple use, a negligible HAMA response rate, no effect on granulocyte function and an accuracy comparable to WBC scanning.

Adult↗

PubMed1994

The processing and fate of antibodies and their radiolabels bound to the surface of tumor cells in vitro: a comparison of nine radiolabels.

UNLABELLED: Processing radiolabeled degradation products is the key factor affecting retention of antibodies within the cell. In this study, we have analyzed the processing of antibodies labeled in nine different ways. METHODS: Antibodies were labeled with three different radioisotopes and seven different forms of 125I. Eight of the radiolabels (except 188Re) were conjugated to the same antibody, MA103, and tested on the renal carcinoma cell line SK-RC-18 and/or the ovarian carcinoma cell line SK-OV-6. Rhenium conjugation utilized the antibody RS7, the target cell line ME180 and three of the other radiolabels were also tested with this antibody-target cell combination for comparison. RESULTS: Iodine conjugated to antibodies by conventional methods was rapidly released from the cell after antibody catabolism. In contrast, iodinated moieties, such as dilactitol-tyramine and inulin-tyramine were retained within cells four to five times longer. CONCLUSIONS: The use of radiolabels that are trapped within cells after antibody catabolism can potentially increase the dose of radiation delivered to the tumor, from the same amount of radioactivity deposited by a factor of four or five. The prolonged retention of 111In relative to 125I is not due to deiodination of iodine conjugates, but rather to intracellular retention of catabolic products containing 111In, perhaps within lysosomes.

Acetylgalactosamine↗

PubMed1994

Immunoscintigraphy of Pneumocystis carinii pneumonia in AIDS patients.

UNLABELLED: The diagnosis of Pneumocystis carinii pneumonia (PCP) currently relies upon cytological demonstration of the organism in sputum or bronchoscopy specimens. The purpose of this study was to develop a radiolabeled monoclonal antibody (Mab) against Pneumocystis carinii (P. carinii) and to evaluate its use for imaging PCP. METHODS: We studied 16 HIV-infected patients with pneumonia in order to evaluate a new Mab-based imaging method for diagnosing PCP. Most patients were managed for opportunistic pneumonia associated with AIDS, including standard cytological tests, and, in all cases, intensive chemotherapy. Prior to the clinical study, the Mab raised to P. carinii was shown to react with human P. carinii but not with rat P. carinii or human white blood cells. RESULTS: After labeling a 1-mg Mab Fab' fragment with 30 mCi of 99mTc, the presence or absence of PCP could be confirmed in six of seven or seven of eight assessable patients, respectively, by external photoscanning within 24 hr. This shows a sensitivity of 85.7% and a specificity of 86.7%. CONCLUSION: Our findings suggest that PCP can be diagnosed by a noninvasive imaging method employing a small dose of a 99mTc-labeled Mab showing specificity for the infectious organism, since patients with P. carinii-free pneumonia were correctly negative in 87.5% of cases. Rapid diagnosis and organ-localization of other infectious lesions with organism-specific, radiolabeled Mabs may be feasible.

AIDS-Related Opportunistic Infections↗

PubMed1993

Specificity and properties of MAb RS7-3G11 and the antigen defined by this pancarcinoma monoclonal antibody.

The murine monoclonal antibody (MAb) RS7-3G11 is an IgG1 with pancarcinoma reactivity, which has been raised against human squamous-cell carcinoma of the lung. Immunoperoxidase staining of frozen tissue sections demonstrated that the antigen defined by RS7-3G11 is present in tumors of the lung, stomach, bladder, breast, ovary, uterus and prostate. The rate and extent of internalization of RS7-3G11 into Calu-3, an adenocarcinoma of the lung cell line, was investigated using unconjugated MAb, followed by fluorescence labelling, and by binding 125I-RS7-3G11 followed by acid removal of surface-bound antibody. Rapid internalization of MAb RS7-3G11 into target cells was observed. Antibody internalization was noted at 30 min, and by 2 hr virtually all MAb RS7-3G11 was internal. Although MAb RS7-3G11 was raised against non-small-cell carcinoma of the lung, ME-180, a cervical-carcinoma cell line, expresses higher quantities of the antigen than the lung-carcinoma cell lines. Due to the higher antigen density in ME-180 cells, this line was used for immunoprecipitation studies and antigen purification. Immunoprecipitation studies using the ME-180 cervical-carcinoma cell line metabolically labeled with [3H]leucine or [3H]glucosamine demonstrated that the antigen defined by RS7-3G11 is a glycoprotein of M(r) 46 kDa. Deglycosylation by treatment with endoglycosidase-F resulted in a protein with a M(r) of 35 kDa. RS7-3G11-antigen was purified from ME-180 tissue-culture cells using affinity-column chromatography. By SDS-PAGE it was seen that the antigen was highly purified. The major band appeared at M(r) of 45 to 48 kDa. This result is in agreement with the immunoprecipitation studies. The broad band observed in the SDS-PAGE is typical of many glycoproteins, and suggests heterogeneity of glycosylation. Chemical and enzymatic treatments of the antigen, followed by Western blot analyses, suggest that the RS7-3G11 antigenic determinant is composed of a conformation-dependent peptide.

Animals↗

PubMed1993

Characterization of second-generation monoclonal antibodies against carcinoembryonic antigen.

BACKGROUND: A second-generation panel of anti-carcinoembryonic antigen (CEA) monoclonal antibodies (MoAb) has been generated, and the specificity has been compared with that of the first panel of MoAb used to differentiate meconium antigen (MA) from CEA. METHODS AND RESULTS: Four of the MoAb had similar specificities to the first-generation panel of NP MoAb. MN-15, like its first-generation equivalent, NP-1, reacts with normal cross-reactive antigen (NCA), MA, and CEA; both MN-15 and NP-1 react strongly with granulocytes. MN-2 has properties similar to Class II NP-2, being reactive with MA and CEA, cross-blocking binding to CEA by NP-1, and having low reactivity with granulocytes; both NP-2 and MN-2 stain granulocytes in frozen tissue sections but show minimal staining of granulocytes in sections fixed in formaldehyde solution and embedded in Paraplast (Fischer Scientific, Pittsburgh, PA). MN-14 demonstrates properties similar to the Class III anti-CEA-specific MoAb, NP-4, being unreactive with NCA and MA. MN-14, as compared with NP-4, demonstrated significantly superior tumor targeting in a human colon tumor xenograft model and consistently stronger staining of frozen sections of colon cancer. A fifth MoAb, MN-3, had properties uniquely different from the NP series of MoAb, reacting strongly with granulocytes but not demonstrating the liquid-phase ion-sensitivity binding of CEA exhibited by MN-15 and NP-1. CONCLUSIONS: MN-14 is being evaluated for radioimmunodetection of and radioimmunotherapy for CEA-containing cancers, whereas MN-3 is being studied for the radioimmunodetection of occult infections and sites of inflammation.

Animals↗

PubMed1993

Clinical evaluation of tumor targeting with a high-affinity, anticarcinoembryonic-antigen-specific, murine monoclonal antibody, MN-14.

BACKGROUND: The authors previously reported that an anticarcinoembryonic antigen antibody against a carcinoembryonic antigen (CEA)-specific epitope is preferred for clinical investigations. They developed a second generation, CEA-specific murine monoclonal antibody (MoAb), MN-14 (IMMU-14), that has a tenfold higher affinity. This report summarizes the initial clinical experience with the new MoAb. METHODS: MN-14 immunoglobulin G (IgG) (0.5-6.0 mg) was labeled with radioactive iodine (I131) (5-80 mCi) and injected into 22 patients with cancer. External scintigraphy was used to determine targeting in patients with low and highly elevated plasma CEA. Quantitative external scintigraphy methods were used to determine organ and tumor clearance rates and absorbed radiation doses. Targeting data were correlated with several factors, including MoAb protein dose, plasma CEA, and relative tumor burden. RESULTS: Despite more than 80% complexation with plasma CEA of more than 500 ng/ml, all known tumor sites were disclosed by external scintigraphy. The overall sensitivity of tumor targeting on a lesion basis was 89%. The residence time in the blood was predicted by body weight (P = 0.05) and the log of plasma CEA (P = 0.043). The absorbed dose to the red marrow and total body could be predicted by the body weight of the patient, but no other factor contributed significantly to the clearance rate or absorbed dose to the organs. Individual tumors received an average dose of 9.3 +/- 6.4 cGy/mCi. The absorbed dose to the tumors was negatively correlated to the weight of the tumor, and the percent uptake in the tumor was positively correlated to the estimated total tumor burden. Patients injected with approximately 5 mg of MN-14 IgG were more likely to have anti-mouse antibodies (HAMA) develop than were patients who were injected with less MoAb. CONCLUSIONS: These results suggest that MN-14 targets tumors effectively, even in the presence of elevated circulating CEA. Additional studies are necessary to determine if an advantage for the higher affinity MN-14 MoAb, compared with the lower affinity NP-4 MoAb, can be appreciated clinically.

Adult↗