A prospective imaging study of 131I-B72.3 monoclonal antibody in patients with epithelial ovarian cancer: preliminary report

Anti-CEA and Other Antibodies in the Study of Gastrointestinal Tumors

Localization of gastrointestinal tumors by means of labeled monoclonal antibodies is a new, sensitive and suitable technique currently used in several centers. Encouraging results have been documented with several monoclonal antibodies by different authors. This article reviews our experience with radioimmunoscintigraphy in 59 patients with colorectal cancer in follow-up, using 131I and 111In labeled B72.3, and in 16 patients with primary gastrointestinal tumors using 99mTc anti-CEA monoclonal antibody (type F023C5). The sensitivity of both B72.3 and anti-CEA was greater than 70% either for primary tumors and abdominal recurrences or distant metastases except hepatic ones. A significant gradient in antibody uptake was measured on surgical biopsies between tumors and normal tissues allowing a good in vivo contrast for gamma detection. We have defined the impact of some factors affecting in vivo tumor targeting. In fact, pharmacodynamics of MAbs, percentage of injected dose bound to tissues were measured, and in particular antigenic content in tumor nodules was quantified. Furthermore, the results of RIS were compared to those obtained by CT and other imaging modalities.

Gene therapy for ovarian cancer: progress and potential

Gene therapy remains a promising therapeutic modality for ovarian cancer. Yet much work remains to be done to see gene therapy realize its full potential in elucidating the complex genetic interactions of delivered genes within target cancer cells and in the development of improved vector systems. Because most neoplasms involve multiple mutations, the targeting of a single mutation is unlikely to achieve total tumor control: gene therapy strategies that target multiple cellular processes or invoke various antitumor approaches need to be investigated. Additionally, current vector systems do not transduce ovarian cancer cells efficiently and are hampered by immune responses that further limit their efficacy. Additionally, limitations in vector specificity lead to transduction of normal cells and subsequent toxicity. Investigators are developing refinements to current gene therapy approaches that would address these limitations and that are soon to be incorporated into clinical trials. It is hoped that these advances will lead to improvements in the therapeutic index for ovarian cancer gene therapy and provide another effective therapeutic tool for this deadly disease.

An immunomagnetic-based method for the purification of ovarian cancer cells from patient-derived ascites

OBJECTIVE

Primary ovarian cancer cells obtained from fresh tumor have many advantages over established cell lines. Therefore, a procedure for the specific and efficient purification of such neoplastic cells is critical. We report an effective immunomagnetic method for the isolation of tumor cells from the ascitic fluid of patients diagnosed with ovarian adenocarcinoma.

METHODS

This procedure incorporates the use of monoclonal antibody (mAb) CC49, which recognizes the tumor-associated glycoprotein 72 (TAG-72). TAG-72 is highly expressed on ovarian tumor cell surfaces with little or no reactivity with normal tissues. Also used in this protocol are immunomagnetic beads, which bind to the CC49 mAb via a secondary antibody. When ovarian cancer cells adhere to the magnetic beads, a magnetic field is used to separate the tumor cells from all other cellular components.

RESULTS

Using ascitic fluid from five patients, we found that preparations before purification contained between 38 and 52% neoplastic cells. Using our method, we produced preparations that were between 63 and 96% pure for cancer cells, thus obtaining an average increase in tumor cell enrichment of 86%.

CONCLUSION

We, therefore, believe this method is preferable for producing high yields of pure ovarian neoplastic cells. We are now employing this technique in our laboratory to provide a stringent and pure template for our studies on gene transfer to primary ovarian cancer cells.

Impact of radioimmunoscintigraphy on the management of colorectal and ovarian cancer patients: a retrospective study

Noninvasive differentiation of benign from malignant disease has emerged as an important diagnostic challenge in the current age of health-care cost containment. Most physicians today acknowledge that early and accurate detection of cancer is important in successful treatment. Antibodies have been developed, labeled with radioactive isotopes, and used to detect and treat malignant tumors. During the past few years, several radiolabeled antibodies have received approval from the U.S. Food and Drug Administration for imaging colorectal, lung, ovarian, and prostate carcinomas, thus expanding and improving the physician's ability to detect and follow cancer in patients. At present, there is ample evidence in the literature to suggest that imaging with the 111In-labeled monoclonal antibody B72.3 is clinically useful for detecting primary/recurrent colorectal and recurrent ovarian carcinomas. In this article, we present a retrospective review of 136 patients from 10 moderate-sized hospitals who underwent a study with radioimmunoscintigraphy (RIS), using the 111In B72.3 antibody and standard diagnostic examinations for the detection of recurrent colorectal or ovarian carcinoma. The resulting data were analyzed in an effort to determine if (and how) information obtained from this radioimmunoscintigraphic procedure is being used by referring physicians. Our findings suggest a gradually increasing use of scan findings with the 111In B72.3 antibody in making patient-management decisions.

Effect of circulating antigen on immunoscintigraphy of ovarian cancer patients using anti-CA125 monoclonal antibody

The murine monoclonal antibody (mAb) 145-9 recognizes an epitope present on CA125 but different from the epitope defined by the mAb OC125. To evaluate the clinical usefulness of the 145-9 antibody, immunoscintigraphy was performed in ovarian cancer patients and the effect of circulating CA125 on tumor imaging was investigated. Two milligrams (74 MBq) of 111In-labeled 145-9 was injected intravenously into 11 patients with ovarian cancer. Pre-injection serum CA125 concentrations were between 166 U/ml and 7414 U/ml. Tumors were visualized in 10 of 11 patients. In two patients, lymph nodes that were not detected by other imaging modalities but were clinically suspected as metastases were visualized. There was no correlation between serum CA125 level and antibody uptake in the tumors. Immune complexes between the antibody and circulating antigen were observed in sera of all the patients, but the fraction of radioactivity in complex form did not correlate well with serum CA125 levels. The immune complexes survived in the circulation and the circulating radiolabel, including immune complexes, was still bound to solid-phase CA125. The plasma clearance rate and hepatic uptake of the antibody were not significantly affected by circulating CA125. In conclusion, the antibody 145-9 formed complexes with CA125 in vivo but this did not Compromise the outcome of antibody imaging. The antibody 145-9 can be used in immunoscintigraphy of ovarian cancer irrespective of serum CA125 level.

Radioimmunoscintigraphy of ovarian tumours with technetium-99m labelled monoclonal antibody-170: first clinical experiences

The recently developed technetium-99m-labelled monoclonal antibody-170 (MAb-170) was designed for diagnostic use in patients suffering from gynaecological adenocarcinoma. Following in vitro studies which showed immunoreactivity of this antibody to more than 90% of human adenocarcinomas, the present investigation was initiated to verify its usefulness for radioimmunoscintigraphy of ovarian tumours. Most of the 30 patients participating in this study underwent immunoscintigraphy prior to first-look surgery. Biokinetic evaluation in two patients showed a plasma half-time of 18.9 h (mean value, n = 2, r = 0.98) and a biexponential total body curve with values of 7.7 h and 17 days (r = 0.98). The mean 24-h urinary excretion was 12% of the injected dose. Radioimmunoscintigraphy using the MAb-170 recognised 12 of 13 cases of adenocarcinoma of the ovaries, corresponding to an overall sensitivity of 92.3%. Specificity was 94.1% (16/17). The calculation of accuracy yielded a figure of 93.3% (28/30). Of 33 known lesions, 26 were visualised successfully; thus the locoregional sensitivity was 78.8%. Of 29 benign tumour sites, 28 showed no evidence of tracer accumulation, corresponding to a locoregional specificity of 96.6%. The smallest lesion visualised was an adenocarcinoma of the corpus uteri with a diameter of 1.5 cm. Technetium-99m labelled MAb-170 is a promising new radiopharmaceutical for immunoscintigraphy of ovarian adenocarcinoma.

Tumor imaging with monoclonal antibodies

Immunoscintigraphy offers the possibility of specifically targeting human tumors, but the complexity of the human immune system, as well as tumor-related phenomena, prevent monoclonal antibodies from reaching a large number of tumor cells in which they can interact with the antigen. Possible ways to overcome these problems are the use of small fragments, in particular those of genetically engineered humanized antibodies including single immunoglobulin-variable domains, as well as techniques to label the antibody in vivo after a sufficient amount has been taken up by the tumor and the remainder has been eliminated. Despite the low absolute tumor uptake, results of European studies, presently available radiolabeled monoclonal antibodies in gastrointestinal and ovarian cancers yield an average sensitivity of more than 70% with an average specificity of more than 80%, even in otherwise occult tumors. Because of possible tracer uptake in normal liver, the detection rate of liver metastases varies from less than 10% to more than 90%. For the detection of local recurrence in the pelvis, immunoscintigraphy has been found to be more accurate than methods that are based on the imaging of structural changes. Fusion of morphological and functional images might improve the early detection of recurrent and metastatic disease. In melanoma, another tumor that has been extensively studied in Europe, similar results have been obtained, whereas only few data are presently available for other tumors (especially lung and breast cancer).

Biologic properties of a CH2 domain-deleted recombinant immunoglobulin

Monoclonal antibody (MAb) B72.3 reacts with TAG-72, a high-molecular-weight mucin expressed on several types of human carcinoma, and is currently being used in clinical trials for the diagnosis and therapy of human carcinoma. An expression construct containing cDNA encoding an immunoglobulin (Ig) heavy chain, with the variable region of murine MAb B72.3 and a human Ig constant region with a deletion of the CH2 domain, was generated. Immunoglobulin from the transfectoma with the highest expression of the TAG-72 immunoreactive antibody was designated MAb chimeric (c) B72.3 delta CH2. The pharmacokinetics of serum clearance of iodine-labeled MAbs cB72.3 delta CH2 and the intact cB72.3 were compared in athymic mice. By 24 hr, less than 1% of the cB72.3 delta CH2 was left in the plasma, while 36% of the cB72.3 still remained. The T1/2 alpha values of the cB72.3 delta CH2 and cB72.3 MAbs were 1.7 and 2.4 hr, respectively. The T1/2 beta values were 7.8 hr for the domain-deleted cMAb and 48.9 hr for cB72.3. Biodistribution studies in athymic mice bearing LS-174T xenografts showed a reduction in the percentage of injected dose per gram in tumor with 131I-cB72.3 delta CH2; however, the 131I-cB72.3 delta CH2 both localized to tumors faster and cleared from the blood faster than the 125I-cB72.3 MAb. Only trace amounts of the 131I-cB72.3 delta CH2 were detected in normal tissues, including kidney. The faster clearance rate, more rapid tumor targeting and lack of metabolic uptake in normal tissues demonstrated with the iodine-labeled CH2 domain-deleted cMAb may be an advantage for certain clinical protocols.

Management of patients with ovarian cancer using monoclonal antibodies

We describe in detail the current trend using monoclonal antibodies to diagnose ovarian cancer either in vitro or in vivo. The approach with such powerful reagents allows to differentiate in vitro tumor histotypes and to detect in peritoneal washings the presence of a few neoplastic cells which characterize the minimal disease. The detection of elevated sera levels of ovarian cancer-associated antigens, such as CA-125 and TAG-72, allows the monitoring, follow-up of these patients and the response to therapy with great accuracy. We focused our attention on the role in vivo of labelled monoclonal antibodies, mainly for diagnostic purposes. Radioimmunoscintigraphy has been found to be more reliable than CT and US to detect foci of disease mainly in patients already treated by surgery, overcoming all the problems usually encountered with these two procedures.

Enhancement of tumor-associated glycoprotein-72 antigen expression in hormone-related ovarian serous borderline tumors

The immunoreactivity of monoclonal antibody (MoAb) B72.3 with ovarian serous tumors of borderline malignancy from 44 women who were pregnant, were on hormone medication containing a progestin, or were known to be in the secretory phase of the menstrual cycle, was compared with that of similar tumors of 32 patients who were not known to be in any of these three categories. All 76 borderline tumors expressed the tumor-associated glycoprotein (TAG-72) recognized by MoAb B72.3. Striking staining differences (P less than 0.0001) were observed between the hormone-related and the nonhormone-related tumors. Differences were also noticed between the staining of tumors from pregnant patients and that of previous, persistent, or recurrent tumors of the ipsilateral or contralateral ovaries when the same patients were not pregnant. Tumor MoAb B72.3 reactivity increased with progressive gestational age and fell to lower levels at term and during the postpartum period. Although it has been suggested by cell culture studies, enhanced TAG-72 expression in human tumors under hormonal stimulation has not been described before.

Radioimmunoscintigraphy of ovarian cancer with the MOv18 monoclonal antibody

The monoclonal antibody (Mab) 131I-MOv18 was administered to 30 patients with ovarian carcinoma intravenously (n = 20) and intraperitoneally (n = 10). After intraperitoneal administration, higher tumour uptake (mean values 1.3% vs. 0.8%) and a better tumour/background ratio (mean values 2.8 vs. 1.9) than after intravenous injection were obtained. Moreover, after intraperitoneal administration the uptake in non-affected organs, such as liver and spleen, was lower. However, occasionally the favourable results of the intraperitoneal route were cancelled by persistent pelvic non-specific accumulations of 131I-MOv18. The possibility to change the biodistribution pattern in the latter cases with peritoneal washing was evaluated. 3 patients were submitted to this procedure and an improvement in the radiotracer biodistribution was obtained in 1 case. With regard to tumour detection, the average sensitivity (73%) showed a significant difference from the sensitivities for abdominal (61%) and pelvic lesions (90%). No false positive results were noted.

Clinical studies with B72.3 in ovarian cancer and probe-guided tumor localization

The present study reports the findings of radiolabeled monoclonal antibody (MoAb) application in the post-operative monitoring of patients with ovarian carcinoma. We studied 40 patients with histologically confirmed ovarian cancer using two radiolabeled MoAbs, 131I-B72.3 and 131I-OC125. Antibody scans showed that high uptake of radiolabeled MoAb was consistently associated with presence of disease confirmed by computed tomography, ultrasonography, clinical evolution and in a few cases by second look procedures. Computed tomography could not discriminate well between post-operative fibrosis and tumor lesion especially when localized in the peritoneum. We conclude that radiolabeled MoAbs, computed tomography and serum tumor markers are complementary in the postoperative monitoring of patients with ovarian carcinoma.

In vitro and in vivo regulation of tumor antigen expression by human recombinant interferons

In vitro treatment with either type I or type II interferon (IFN) can selectively enhance the expression of several tumor antigens, such as the carcinoembryonic antigen (CEA) and the tumor-associated glycoprotein-72 (TAG-72) in different human carcinoma cell lines and result in enhanced level of monoclonal antibody (MAb) binding to the cell surface. In vivo animal studies demonstrated that treatment of athymic mice with a type I interferon [i.e. interferon-alpha (A)] significantly increased the expression of a 90 kDa tumor antigen which improved the targeting of a MAb to the carcinoma xenograft. More recent studies reported that in vitro IFN treatment of human adenocarcinoma cells isolated from human malignant serous effusions selectively increased the expression of TAG-72 and CEA. One can envision that the ability of these cytokines to upregulate the level of expression of human tumor antigens presents an important experimental model in which to study the regulation of markers often correlated with epithelial cell differentiation. In addition, the increase of selective MAb-defined antigens may also be exploited in an adjuvant setting to localize higher amounts of MAbs to the tumor cell surface and, thereby, improve the effectiveness of a MAb for tumor diagnosis and, possibly, therapy.

Chimeric B72.3 mouse/human (IgG1) antibody directs the lysis of tumor cells by lymphokine-activated killer cells

Chimeric mouse/human B72.3 (cB72.3) antibodies having a human IgG1 (gamma 1) or IgG4 (gamma 4) constant region were compared to the native murine IgG1 B72.3 (nB72.3) monoclonal antibody (mAb) for their ability to participate with human effector cells in antibody-dependent cellular cytotoxicity (ADCC). Because the TAG-72 antigen recognized by B72.3 is poorly expressed on tissue-cultured tumor cell lines, the xenografted OVCAR-3 human ovarian carcinoma ascites was used as a cytotoxicity target. The lytic activity of the cB72.3(gamma 1) mAb with peripheral blood lymphocytes was 1.5- to 50-fold greater than that of the nB72.3 mAb and usually the cB72.3(gamma 4) mAb. However, lymphocytes from some donors had similar ADCC activity with either the cB72.3(gamma 1) or cB72.3(gamma 4) mAb. The cB72.3(gamma 1) and the murine anti-colon carcinoma CO17-1A mAb had comparable activity in mediating ADCC against the OVCAR-3 tumor. Exposure of lymphoid cells to interleukin-2 (IL-2) (100-500 U/ml) for 24 h to generate lymphokine-activated killer (LAK) cells augmented ADCC mediated by the cB72.3(gamma 1) mAb 2- to 22-fold. By contrast, LAK cells from most donors expressed weak non-specific cytotoxicity against OVCAR-3 ascites tumor cells. The cB72.3(gamma 1), and to a lesser extent, the cB72.3(gamma 4) chimera also participated with monocytes in mediating ADCC, but the antibody-dependent lytic potency of monocytic effectors was much weaker than that of IL-2-activated lymphoid cells. These studies show that the cB72.3(gamma 1) mAb has appreciable ADCC-mediating properties, suggesting a potential role for its incorporation into treatment strategies utilizing adoptive killer cell and/or lymphokine therapy.

Monoclonal antibodies reactive with human breast or ovarian carcinoma: in vivo applications

Monoclonal antibodies (MoAbs) are unique and useful bioprobes that allow in vivo targeting of membrane-associated or circulating antigens. Most of the clinical trials to date have used low dosages of radiolabeled MoAb given in a single dose. Newer studies have included antibody fragments, repeated injections, intraperitoneal (IP) administration, and other labels such as 90Y. Clinical MoAb trials are often arduous, expensive, and time-consuming to perform. Before human use, animal studies and extensive MoAb characterization are required. The production of pharmaceutical grade, radiolabeled MoAb is technically difficult and costly. Clinical trials require administrative and patient consent as well as extensive written protocols. These studies necessitate interdepartmental and intradepartmental cooperation and coordination. Furthermore, the use of in vivo radiolabeled probes impacts many levels of health care providers from janitorial, nursing, and technical staff to laboratories and physicians. Simple blood tests or disposal of body excretions may concern nursing or technical staff with the possibility of radiation exposure. The responsibility for study design, personnel involvement, and prospective use in patients without a definitive cancer diagnosis ultimately rests with the physician. While many issues have been addressed, additional clinical trials, consideration of safety issues, and standardization between institutions will be necessary before the use of radiolabeled MoAb for diagnosis, management, or therapy of human tumors becomes routine. Continued cooperation and funding should ensure its achievement.

Diagnosis of ovarian cancer with radiolabelled monoclonal antibodies: our experience using 131I-B72.3

Radioimmunoscintigraphy (RIS) using 131I-labelled B72.3, a monoclonal antibody (MoAb) reacting against a tumor associated antigen (TAA) called TAG-72, has been performed in 36 patients with epithelial ovarian cancer. The patients were divided in three groups as follows: 17 patients with primary cancer before any therapy (Group 1); 10 patients studied after a partial therapeutic approach, having either bulky or minimal disease (Group 2); 9 patients with microscopic disease or in clinical remission at the moment of the study (Group 3). All the most important epithelial histotypes, including mucinous, were present. Results were confirmed at surgery and/or by other diagnostic procedures. Immunocytochemical (ICC) and immunocytofluorimetric (ICF) studies on ascitic collections were performed in order to demonstrate specificity of B72.3 and TAG-72 distribution on neoplastic cells. Immunohistochemistry (IHC) on tissue sections was also obtained. No cross reactions between B72.3 and mesothelial cells in the presence of specific uptake by neoplastic cells was found. Moreover, a non-homogeneous distribution of TAG-72 in the neoplastic population was demonstrated by ICF. RIS proved the intraperitoneal presence of disease in 15 out of 17 and in 5 out of 10 patients in Groups 1 and 2, respectively. One out of four (Group 1) and two out of four (Group 2) extraperitoneal metastases were also seen. False negative results were explained by lack of expression of the antigen, size and location of the lesion, and patho-physiological conditions. One false positive due to an aspecific uptake by a post-surgical active scar was also observed in a disease-free patient.