In Vitro and in Vivo Regulation of Human Tumor Antigen Expression by Human Recombinant Interferons: A Review

The ongoing development of monoclonal antibody technology may eventually lead to the selective targeting of human carcinoma lesions by MAbs conjugated with a variety of cytotoxic agents (i.e., radionuclides, drugs, etc.). The antigen phenotype of the carcinoma cell will play an important role in the efficacy of the MAbs. Clearly, the human tumor antigens that are expressed on all carcinoma cells, and with a high antigen density, should provide the optimal target for the MAbs. More often than not, however, the human tumor antigens whose expression is highly selective for human tumor cells will also exhibit a certain degree of heterogeneity. Therefore, the ability of interferon to augment the level of expression of human tumor antigens such as TAG-72 and CEA, may play an important role in an adjuvant setting for immunoscintigraphy and/or immunotherapy. More recent observations have demonstrated that interferon treatment can also enhance the amount of TAG-72 and CEA secreted by the tumor cell. The ability of interferon to enhance the shedding of both TAG-72 and CEA could be of particular importance since recent reports suggest that their presence in the sera of patients diagnosed with gastrointestinal adenocarcinoma may be complementary and that the ability to increase either marker may facilitate earlier diagnosis of recurrent disease. It is conceivable that in subsequent years effective approaches to monitoring and/or treating malignacies may include a new combination of biological/immunological therapy.

Comparative studies of Avipox-GM-CSF versus recombinant GM-CSF protein as immune adjuvants with different vaccine platforms

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a potent immune stimulant when administered with different vaccines. Optimal use of GM-CSF resides in its ability to act locally to stimulate the proliferation and maturation of professional antigen-presenting cells (APCs) (i.e., Langerhans' cells) at the injection site. GM-CSF was engineered into a replication-incompetent recombinant avian (fowlpox) virus (rF-GM-CSF) and a single subcutaneous injection resulted in a sustained enrichment of activated dendritic cells within the regional draining lymph nodes. Those changes were attributed to local GM-CSF production at the injection site by rF-GM-CSF-infected cells. Studies were carried out in which mice were administered different types of beta-galactosidase (beta-gal)-based vaccines--whole protein, peptide, recombinant poxviruses--and GM-CSF was administered either as a single injection of rF-GM-CSF or four daily bolus injections of the recombinant protein. The use of rF-GM-CSF either improved the immune adjuvant effect, as observed for poxvirus-based vaccines, or was equivalent to rGM-CSF, as observed with the beta-gal protein vaccine. It is important to note that with either the replication-competent (vaccinia) or replication-incompetent (fowlpox) vaccines expressing LacZ, strong CTL responses directed against beta-gal were induced only when rF-GM-CSF was used as the immune adjuvant. Engineering GM-CSF into a recombinant fowlpox virus offers an excellent vehicle for the delivery of this cytokine as an immune adjuvant with specific vaccine platforms. In particular, delivery of GM-CSF via the rF-GM-CSF construct would be preferred over bolus injections of rGM-CSF when used as an immune adjuvant with whole protein or recombinant poxvirus-based vaccines. The study underscores the importance of defining the appropriate delivery form of an immune adjuvant, such as GM-CSF, relative to the immunization strategy to maximize the host immune responses against a specific antigen.

IgEs targeted on tumor cells: therapeutic activity and potential in the design of tumor vaccines

Surface-bound IgE play a central role in antiparasite immunity; to exploit IgE-driven immune mechanisms in tumor prevention and control, monoclonal IgEs of irrelevant specificity were loaded through biotin-avidin bridging onto tumor cells, either by systemic administration to tumor-bearing mice or pre-loading of tumor cells before inoculation. Here we show that systemic administration of biotinylated IgEs to mice bearing tumors pre-targeted with biotinylated antibodies and avidin significantly decreased tumor growth rate. In addition, as compared with IgG-loaded control cells, inoculation of suboptimal doses of IgE-loaded tumor cells suppressed tumor formation in a fraction of animals and induced protective host immunity by eliciting tumor-specific T-cell responses. Similarly, tumor vaccination experiments showed that irradiated tumor cells (IgE loaded by biotin-avidin bridging) conferred protective immunity at doses 100-fold lower than the corresponding control cells without IgE. Finally, in vivo depletion of eosinophils or T cells abrogated IgE-driven tumor growth inhibition. These results demonstrate that IgEs targeted on tumor cells not only possess a curative potential but also confer long-term antitumor immunity and that IgE-driven antitumor activity is not restricted to the activation of innate immunity effector mechanisms but also results from eosinophil-dependent priming of a T-cell-mediated adaptive immune response. This suggests a potential role for IgEs in the design of new cell-based tumor vaccines.

Detection of blood-borne cells in colorectal cancer patients by nested reverse transcription-polymerase chain reaction for carcinoembryonic antigen messenger RNA: longitudinal analyses and demonstration of its potential importance as an adjunct to multiple serum markers

The use of reverse transcription-PCR (RT-PCR) to analyze cells in the blood of cancer patients for the detection of mRNA expressed in tumor cells has implications for both the prognosis and the monitoring of cancer patients for the efficacy of established or experimental therapies. Carcinoembryonic antigen (CEA) is expressed on approximately 95% of colorectal, gastric, and pancreatic tumors, and on the majority of breast, non-small cell lung, and head and neck carcinomas. CEA shed in serum is useful as a marker in only approximately 50% of colorectal cancer patients and rarely is shed by some other carcinoma types. RT-PCR has been used previously to detect CEA mRNA in cells in the blood and lymph nodes of cancer patients. Under the assay conditions validated in the studies reported here, 34 of 51 (67%) patients with different stages of colorectal cancer had blood cells that were positive by RT-PCR for CEA mRNA, whereas none of 18 patients with colonic polyps were positive; 2 of 60 apparently healthy individuals (who were age and sex matched with the carcinoma patients and were part of a colon cancer screening program as controls) were marginally positive. The results of CEA PCR in the blood of the carcinoma patients and the other groups showed strong statistical correlation with the disease (P2 < 0.0001). Analyses were carried out to detect both serum CEA protein levels and CEA mRNA in blood cells of colorectal carcinoma patients by RT-PCR. For all stages of disease, 18 of 51 patients (35%) were positive for serum CEA, whereas 35 of 51 (69%) were positive by RT-PCR. More importantly, only 5 of 23 (20%) of stage B and C colorectal cancer patients were positive for serum CEA, whereas 16 of 23 (70%) were positive by RT-PCR. The use of two other serum markers (CA19.9 and CA72-4) for colorectal cancer in combination with serum CEA scored two additional patients as positive; both were positive by RT-PCR for CEA mRNA. Pilot long-term longitudinal studies conducted before and after surgery identified some patients with CEA mRNA in blood cells that were negative for all serum markers, who eventually developed clinical metastatic disease. The studies reported here are the first to correlate RT-PCR results for CEA mRNA in blood cells with one or more serum markers for patients with different stages of colorectal cancer, and are the first long-term longitudinal studies to use RT-PCR to detect CEA mRNA in blood cells of cancer patients. Larger cohorts will be required in future studies to define the impact, if any, of this technology on prognosis and/or disease monitoring.

Granulocyte/macrophage-colony stimulating factor produced by recombinant avian poxviruses enriches the regional lymph nodes with antigen-presenting cells and acts as an immunoadjuvant

Recombinant avian poxviruses [fowlpox and canarypox (ALVAC)], restricted for replication in nonavian cell substrates and expressing granulocyte/macrophage-colony stimulating factor (avipox-GM-CSF), were evaluated for their ability to enrich an immunization site with antigen-presenting cells (APCs) and, in turn, function as biological vaccine adjuvants. Avipox-GM-CSF administered as a single s.c. injection significantly enhanced the percentage and absolute number of APCs in the regional lymph nodes that drain the injection site. Both the magnitude and duration of the cellular and phenotypic increases within the lymph nodes induced by the avipox-GM-CSF viruses were significantly (P < 0.05) greater than those measured in mice treated with four daily injections of recombinant GM-CSF protein. Temporal studies revealed that the APC enrichment of regional lymph nodes was sustained for 21-28 days after injection of the recombinant avipox virus expressing GM-CSF and, moreover, three injections of the recombinant virus could be given without any appreciable loss of in vivo bioactivity. Mice expressing human carcinoembryonic antigen (CEA) as a transgene (CEA.Tg) developed CEA-specific humoral and cell-mediated immunity after being immunized with avipox-CEA. The coadministration of recombinant avipox viruses expressing CEA and GM-CSF significantly enhanced CEA-specific host immunity with an accompanying immunotherapeutic response in tumor-bearing CEA.Tg mice. The optimal use of avipox-GM-CSF, in terms of dose and dose schedule, especially when used with different immunogens, remains to be determined. Nonetheless, the present findings demonstrate: (a) the effective delivery of GM-CSF to an immunization site using a recombinant avian poxvirus; (b) the compatibility of delivering an antigen and GM-CSF in replication-defective viruses to enhance antigen-specific immunity; and (c) the combined use of recombinant avipox viruses expressing CEA and GM-CSF to generate antitumor immunity directed at a self tumor antigen.

Drug-induced modulation of carcinoembryonic antigen (CEA) expression in neoplastic cells from a patient with rectal cancer

Treatment with 5-fluorouracil (5-FU) or recombinant interferon-gamma (IFN), alone or in combination, was found to increase carcinoembryonic antigen (CEA) expression in several carcinoma cell lines. In this study we examined the in vitro effect of these agents on CEA expression of tumor cells, obtained from a patient operated for rectal cancer. The results showed that exposure of cancer cells to 5-FU or to IFN resulted in increased CEA levels in terms of percentage of CEA-positive cells and mean fluorescence values, as indicated by FACS analysis. However, drug combination did not induce CEA expression higher than that provided by single agents alone. Treatment with 5-FU or with IFN produced a reduction of the total number of viable cells. Moreover, Western blot analysis revealed that exposure of cancer cells to each drug was followed by a substantial increase of the total cellular CEA content. On the contrary, 5-FU in combination with IFN did not increase the expression of the antigen more than that obtained by single agents. Noteworthy, exposure of CEA-negative cells from adjacent normal rectal tissue to both agents alone or in combination, did not result in CEA induction. In conclusion, the present results suggest new approaches aimed at (a) increasing the sensitivity of diagnostic procedures based on detection of CEA-positive tumor cells; (b) facilitating the recognition of CEA-positive cancer cells by immune responses induced by anti-CEA peptide vaccines.

Effect of 5-fluorouracil on carcinoembryonic antigen expression and shedding at clonal level in colon cancer cells

BACKGROUND

The carcinoembryonic antigen (CEA) is a tumor marker largely utilized for the detection of minimal disease or as a target of immunotherapeutic approaches. In preclinical models CEA has been found to be up-regulated after exposure of cancer cells to 5-fluorouracil (5-FU). In the present study, the clonal distribution of CEA and its regulation by 5-FU at clonal level was investigated using human HT-29 colon cancer cells.

MATERIALS AND METHODS

The extent of CEA expression was measured in terms of: (a) antigen levels on plasma membrane, by flow cytometry; (b) cytoplasm and membrane protein, by Western blot analysis: (c) transcript, by Northern blot analysis; (d) CEA shedding by radioimmunossay.

RESULTS

CEA protein and gene transcript were variably expressed among different clones. In all cases 5-FU was able to increase the percentage of CEA-positive cells, the amount of antigen, either in the membrane or cytosolic fractions, and the corresponding transcript. Moreover, a marked increase of CEA shedding was found in drug-treated cells with respect to that of controls. The increase of CEA induced by the antimetabolite was not the result of a selection mechanism based on preferential killing of CEA negative cells. The antimetabolite was capable of enhancing antigen expression also in other CEA-positive tumor cell lines with different basal levels of the marker.

CONCLUSIONS

The present findings could be of potential value to increase the sensitivity of diagnostic procedures based on detection of CEA positive tumor cells. Moreover, the antimetabolite might be included in immunotherapeutic protocols to facilitate recognition of CEA-positive cancer cells by immune responses.

Comparative studies of the effects of recombinant GM-CSF and GM-CSF administered via a poxvirus to enhance the concentration of antigen- presenting cells in regional lymph nodes

Repeated subcutaneous (s.c.) injections of recombinant granulocyte-macrophage colony-stimulating factor (recGM-CSF) for 4-5 days can enrich an immunization site with antigen-presenting cells (APC), which has been correlated with improved immune responses in experimental and clinical studies. A recombinant vaccinia virus encoding the GM-CSF gene (rV-GM-CSF) has been developed and can generate specific antitumour immunity in a whole tumour cell vaccine. In the present study, we examined whether rV-GM-CSF could produce and release GM-CSF locally which, in turn, might enrich a site of immunization for APC as previously shown for recGM-CSF. S.c. injection of rV-GM-CSF significantly (P<0.05) enhanced the percentage and overall number of APC, measured by class II expression levels, in the regional lymph nodes that drain the injection site. Dose- and temporal-dependent studies showed class II expression levels in the draining lymph nodes were maximally enhanced 5-7 days after a single injection of 10(7)plaque-forming units (pfu) of rV-GM-CSF. Flow cytometry revealed that the increase in class II expression resulted from (i) a higher class II expression level on CD19(+)B cells and (ii) an increase in the number of CD11c(+)/class II(+)professional APC within the draining lymph nodes. Moreover, isolation of lymph nodes from rV-GM-CSF-treated mice revealed their capacity to support higher levels of antigen-specific T cell proliferation and allospecific cytotoxic responses. A comparison between a single injection of rV-GM-CSF and a 4-day course of recGM-CSF revealed comparable changes in class II expression and functional T cell assays. GM-CSF can be delivered in a recombinant poxvirus, and the local production of the cytokine results in cellular and phenotypic changes that are similar to those of recGM-CSF. The ability to utilize rV-GM-CSF as a single inoculum may be more compatible with traditional immunization strategies.

Staurosporine increases carcinoembryonic antigen expression in a human colon cancer cell line

Staurosporine (ST), a protein kinase C inhibitor, was found to produce antitumor effects against C22.20, a clonal subline derived from colon cancer HT-29 line, selected for low expression of carcinoembryonic antigen (CEA). However, as assessed by FACS analysis using propidium iodide, no apoptosis or cell cycle alteration was found on day 3 after treatment of C22.20 cells with ST (1-100nM). Exposure of cells to graded concentrations of the drug (i.e., from 1 to 25nM) resulted in a concentration-dependent increase in the percentage of CEA positive cells, as determined by flow cytometric analysis. However, when higher concentrations (i.e. 50nM - 100nM) of ST were used, the percentage of CEA positive cells declined compared to that detected in 25nM-treated tumor. Since these results were obtained in a clonal cell population, it is reasonable to hypothesize that induction rather than selection mechanism is involved in this phenomenon. The potential clinical interest of the present findings stems from the consideration that treatment with ST or its derivatives could improve sensitivity and efficacy of diagnostic and/or immunotherapeutic approaches based on CEA molecules.

Recurrent alterations of the short arm of chromosome 3 define a tumor suppressor region in rat mammary tumor cells

Cytogenetic alterations associated with different stages in carcinogenesis can be distinguished in cultured human or rodent cells transformed by carcinogenic agents. Three tumorigenic rat mammary epithelial cell lines transformed in vitro with 7,12, -dimethylbenz[a]anthracene alone or in combination with 12-O-tetradecanoylphorbol-13-acetate were examined cytogenetically. Non-random alterations consisting of translocations involving the short arm of chromosome 3 and trisomy of chromosomes 14 and X were identified in all three lines. Deletion and inversion of chromosome 1 with the breakpoint at band 1q22 and a duplication 1q 32-43 and trisomy of chromosome 2 were observed in two cell lines. The accumulation of structural alterations and chromosome imbalances during the process of cell immortalization and acquisition of tumorigenicity are required for normal rat mammary cells to become malignant. Unbalanced translocations of chromosome 3 resulting in loss of the short arm had the breakpoint at 3p11. This site is a hotspot of breakage and recombination in various rat tumors and may represent a region of tumor suppressor gene critical to the development of rat mammary tumors, as well as other types of tumors.

Induction of protective host immunity to carcinoembryonic antigen (CEA), a self-antigen in CEA transgenic mice, by immunizing with a recombinant vaccinia-CEA virus

Human carcinoembryonic antigen (CEA) is a well-characterized oncofetal glycoprotein whose overexpression by human carcinomas has been a target for cancer immunotherapy. Transgenic mice that express CEA as a self-antigen with a tissue distribution similar to that of humans have been developed. This study investigates: (a) the responsiveness of the CEA transgenic (CEA.Tg) mice to endogenous CEA or CEA administered as a whole protein in adjuvant; and (b) whether the presentation of CEA as a recombinant vaccinia virus could generate CEA-specific host immunity. By and large, the CEA.Tg mice were unresponsive to CEA, as shown by the lack of detectable CEA-specific serum antibodies and the inability to prime an in vitro splenic T-cell response to CEA. Furthermore, the administration of whole CEA protein in adjuvant to CEA.Tg mice failed to elicit either anti-CEA IgG titers or CEA-specific T-cell responses. Only weak anti-CEA IgM antibody titers were found in those mice. In contrast, CEA.Tg mice immunized with recombinant vaccinia virus expressing CEA generated relatively strong anti-CEA IgG antibody titers and demonstrated evidence of immunoglobulin class switching. These mice also developed T(H)1-type CEA-specific CD4+ responses and CEA peptide-specific cytotoxicity. The ability to generate CEA-specific host immunity correlated with protection of the CEA.Tg mice against a challenge with CEA-expressing tumor cells. Protection against tumor growth was accomplished with no apparent immune response directed at CEA-positive normal tissue. The results demonstrate the ability to generate an effective antitumor immune response to a tumor self-antigen by immunization with a recombinant vaccinia virus. CEA.Tg mice should be an excellent experimental model to study the effects of more aggressive immunization schemes directed at established tumors with the possible development of accompanying autoimmune responses involving normal tissues.

Novel clinical approaches in monoclonal antibody-based management in colorectal cancer patients: radioimmunoguided surgery and antigen augmentation

Surgery, the most effective treatment for colon and rectal cancer, is based on empirical knowledge of the patterns of tumor spread, gross findings at laparotomy, and histologic confirmation of tumor-free margins. In spite of the many technical improvements in surgery, there has not been a significant change in cure rates for colon and rectal cancers. In fact, one-half of affected patients will not survive 5 years. It is in this arena of treatment for primary colon and rectal cancer patients that radioimmunoguided surgery (RIGS) technology may provide the most benefit. RIGS is an intraoperative procedure for detection of carcinoma lesions that are targeted with a radiolabeled monoclonal antibody (MAb) to provide the surgeon with immediate intraoperative definition of tumor margins and identification of occult disease. To optimize this technique, our studies were designed to increase tumor uptake by higher affinity CC-49 (a second-generation MAb) and to increase tumor antigen expression using biological response modifiers (BRMs). The ability of BRMs, such as interferons (IFNs), to enhance the expression of tumor-associated antigens, may play an important role in an adjuvant setting for MAb-based treatment. Preclinical and clinical data provided evidence for the use of IFN as an adjuvant to enhance MAb-targeting of human carcinoma lesions. A combination protocol with IFN and RIGS is ongoing at our institution.

Novel clinical approaches in monoclonal antibody-based management in colorectal cancer patients: radioimmunoguided surgery and antigen augmentation

Surgery, the most effective treatment for colon and rectal cancer, is based on empirical knowledge of the patterns of tumor spread, gross findings at laparotomy, and histologic confirmation of tumor-free margins. In spite of the many technical improvements in surgery, there has not been a significant change in cure rates for colon and rectal cancers. In fact, one-half of affected patients will not survive 5 years. It is in this arena of treatment for primary colon and rectal cancer patients that radioimmunoguided surgery (RIGS) technology may provide the most benefit. RIGS is an intraoperative procedure for detection of carcinoma lesions that are targeted with a radiolabeled monoclonal antibody (MAb) to provide the surgeon with immediate intraoperative definition of tumor margins and identification of occult disease. To optimize this technique, our studies were designed to increase tumor uptake by higher affinity CC-49 (a second-generation MAb) and to increase tumor antigen expression using biological response modifiers (BRMs). The ability of BRMs, such as interferons (IFNs), to enhance the expression of tumor-associated antigens, may play an important role in an adjuvant setting for MAb-based treatment. Preclinical and clinical data provided evidence for the use of IFN as an adjuvant to enhance MAb-targeting of human carcinoma lesions. A combination protocol with IFN and RIGS is ongoing at our institution.

Effect of the combined treatment with 5-fluorouracil, gamma-interferon or folinic acid on carcinoembryonic antigen expression in colon cancer cells

5-Fluorouracil (5-FU) and human recombinant gamma-interferon (gamma-IFN) were found to increase the expression of carcinoembryonic antigen (CEA) in human cancer cells in vitro. In the present study, the antimetabolite was associated with gamma-IFN or folinic acid (FA), a biochemical modulator of cellular metabolism of 5-FU, able to increase its antineoplastic activity. Treatment of two human colon cancer cell lines (HT-29 and WiDr) with 5-FU + gamma-IFN resulted in an increase of CEA expression higher than that obtainable with both agents alone, although no synergistic effects were obtained. This was demonstrated in terms of: (a) mRNA transcripts (HT-29); (b) cytoplasm and membrane CEA protein levels detected by Western blot analysis (HT-29); and (c) plasma membrane reactivity determined by flow cytometry analysis (HT-29 and WiDr). Moreover, 5-FU + gamma-IFN increased HLA class I molecules in the HT-29 cell membrane over that obtainable with gamma-IFN alone. In contrast, both agents did not induce the expression of the costimulatory molecule B7-1. Treatment with FA enhanced the antitumor effect of 5-FU but not its ability to augment CEA expression. This suggests that the FA-sensitive biochemical mechanism of action of 5-FU is not involved in its effect on CEA expression. In vivo studies showed, for the first time, that 5-FU, alone or combined with gamma-IFN, increases the amount of CEA protein over controls, either in cancer cells or in peripheral blood of nude mice bearing HT-29 cells. These results could be of potential diagnostic and/or therapeutic value when CEA protein is the target of humoral or cell-mediated immunity.

Immunization with a syngeneic tumor infected with recombinant vaccinia virus expressing granulocyte-macrophage colony-stimulating factor (GM-CSF) induces tumor regression and long-lasting systemic immunity

A recombinant vaccinia virus encoding the gene for granulocyte-macrophage colony-stimulating factor (rV-GM-CSF) was used to infect the poorly immunogenic murine colon adenocarcinoma cell line, MC-38. Infection of MC-38 tumor cells with rV-GM-CSF completely suppressed the growth of the MC-38 primary tumors, whereas progressively growing tumors were formed in mice injected with MC-38 cells infected with wild type V-Wyeth. Irradiation of the recipient B6 mice before implantation of rV-GM-CSF-infected tumor cells resulted in the development of progressively growing tumors. Moreover, in vivo T-cell depletion studies revealed that growth suppression of the rV-GM-CSF-infected tumor cells was dependent on the presence of both CD4+ and CD8+ T-cell subsets. Subsequent studies established that this immunity was long-lasting and antigen specific, as demonstrated by the protection of rV-GM-CSF-immunized mice from MC-38 tumor challenge but not from challenge with another syngeneic tumor cell type. No such effects were observed when MC-38 tumor cells were infected with recombinant vaccinia viruses expressing interleukin (IL)-2 or IL-6. The results demonstrate that paracrine release of biologically active murine GM-CSF by tumor cells infected with rV-GM-CSF enhances the intrinsic immunogenicity of a poorly immunogenic murine tumor. Presumably the augmentation of tumor immunogenicity induces an antigen-specific T-cell-dependent antitumor response that prevents the formation of primary tumors and protects mice from tumor challenge. Thus in this experimental model, GM-CSF functions as a highly effective vaccine adjuvant.

Quantitative analysis of CEA expression in colorectal adenocarcinoma and serum: lack of correlation

Tissues and sera from 110 patients diagnosed with colorectal primary carcinoma, 20 patients with benign colorectal diseases and 31 healthy donors were subjected to quantitative CEA analysis. Multiple samples from tumor lesions and autologous histologically normal mucosa (10 cm from the tumor) were obtained at the time of surgery (cancer patients) or endoscopy (benign patients and healthy volunteers). CEA content was measured in protein extracts obtained from these tissues using a quantitative RIA method. A limit of normality for CEA content was established as 300 ng/mg of protein. When this was taken as cut-off, 104 of 110 (94.5%) tumor lesions and 51 of 110 (46.4%) autologous histologically normal colonic mucosa from cancer patients had elevated CEA levels. No correlation with stage of disease was found, while a correlation was observed with degree of tumor differentiation. A statistically significant difference between CEA content in tumor lesions and in histologically normal mucosa from cancer patients was observed (p = -0.001). Moreover, CEA content was statistically higher in the normal mucosa from cancer patients than in that from healthy donors (p = 0.005). CEA content in tissue specimens from benign lesions differed significantly from that in tissue from healthy donors (p = 0.005) and in carcinoma lesions (p < 0.001). The highest CEA content was observed in benign lesions with severe dysplasia. No statistical correlation between CEA content in carcinoma tissues and serum CEA levels (r = 0.195, p = .13) was found. Therefore, in considering diagnosis or therapy with anti-CEA MAbs for colorectal-carcinoma patients, or potential therapies with anti-CEA recombinant vaccines, serum CEA levels should not be taken as indicating CEA expression in tumor lesions.

Effect of recombinant alpha-interferon on pharmacokinetics, biodistribution, toxicity, and efficacy of 131I-labeled monoclonal antibody CC49 in breast cancer: a phase II trial

Preclinical studies have demonstrated that recombinant IFN-alpha (rIFN-alpha) can enhance the tumor associated glycoprotein 72 (TAG-72) on tumors. To determine whether rIFN-alpha could enhance TAG-72 expression in vivo in patients, 15 women with breast cancer were randomized to receive daily injections of rIFN-alpha (3 x 10(6) units/m2 for 14 days) beginning on day 1 (group 1 = 7 patients) or on day 6 (group 2 = 8 patients). On day 3, all patients received a 10-20-mCi tracer dose of 131I-CC49, a high-affinity murine monoclonal antibody reactive against TAG-72, followed by a therapy dose of 60-75 mCi/m2 of 131I-CC49 on day 6. Whole body and single-photon emission computed tomography scans along with whole blood pharmacokinetics were performed following tracer and treatment phases. Hematological toxicity was considerable; reversible grade 3-4 neutropenia and thrombocytopenia was observed in 12 of 15 patients. Twelve of 14 patients tested developed human antimouse antibodies 3-6 weeks after treatment. For group 1 patients, whole blood residence time increased significantly between that predicted from the tracer doses and therapy doses (42.6 +/- 4.7 versus 51.5 +/- 4.8 h, respectively; P < 0.01). The calculated radiation absorbed dose to red marrow from therapy compared to tracer activity was also significantly higher for this group (1.25 +/- 0.35 versus 1. 07 +/- 0.26 cGy/mCi; P < 0.05). Treatment with rIFN-alpha was found to enhance TAG-72 expression in tumors from patients receiving rIFN-alpha (group 1) by 46 +/- 19% (P < 0.05) compared to only 1.3 +/- 0.95% in patients not initially receiving IFN (group 2). The uptake of CC49 in tumors was also significantly increased in rIFN-alpha-treated patients. One partial and two minor tumor responses were seen. In summary, rIFN-alpha treatment altered the pharmacokinetics and tumor uptake of 131I-CC49 in patients at the expense of increased toxicity.

Dacarbazine-induced immunogenicity of a murine leukemia is attenuated in cells transfected with mutated K-ras gene

Strong immunogenicity is induced by antitumor triazene compounds in tumor cells through a mutagenic mechanism. A highly immunogenic <<D>> clone, isolated from a dacarbazine-treated L5178Y leukemia of DBA/2 mice, was transfected with K-ras mutated at codon 12 (i.e. ras(m12)). This transfected clone presents at least 2 mutations, one concerning K-ras gene, and the other affecting an unrelated gene, responsible for the generation of a highly immunogenic, MHC class I restricted non-self peptide. The results indicate that cells of <<D>> clone transfected with ras(m12) were less immunogenic than cells of the same origin transfected with the vector alone. Moreover, ras(m12)-transfected cells showed lower levels of H-2K(d) gene expression with respect to those detectable in control cells. In addition, in vivo and in vitro sensitization against <<D>> clone carrying mutated ras did not result in a strong cytotoxic T lymphocyte response against ras(m12)-transfected non immunogenic L5178y target cells. These preliminary results suggest that K-ras mutation could down-regulate the level of tumor immunogenicity, possibly acquired through a mutagenic process affecting other unrelated genes.

Drug-induced changes of carcinoembryonic antigen expression in human cancer cells: effect of 5-fluorouracil

Previous studies showed that 5-fluorouracil (5-FU) is capable of enhancing the membrane reactivity of the human colon carcinoma cell line HT-29 with a monoclonal antibody (COL-1) directed against carcinoembryonic antigen (CEA). In the present study, we show that short-term exposure (i.e., 1 hr) of cancer cells to 5-FU mediates a marked increase of CEA expression, that is concentration-dependent and lasts up to day 5 after treatment. This phenomenon is the result of the drug-mediated enhancement of the CEA expression, but not of the selection of the CEA-positive cells operated by the antimetabolite. This is supported by the finding that the increase of the CEA expression detected by cytofluorimetric analysis is observed not only in the parental HT-29 line, but also in its C22.20 subclone, endowed with a low basal level of CEA and with chemosensitivity to 5-FU lower than that of the parental cell line. Moreover, increase of CEA expression occurs not only in the plasma membrane, but also in the cytosolic cellular compartment, as indicated by the results of Western blot analysis. Northern blot analysis of total RNA extracted from 5-FU-treated HT-29 or C22.20 cells shows an increase in the steady-state levels of CEA and CEA-related transcripts (e.g., biliary glycoprotein). Moreover 5-FU-mediated augmentation of the CEA transcript appears to be attributable mainly to enhanced transcription rather than to increased mRNA stability. It is concluded that induction of enhanced CEA protein expression in cancer cells treated with 5-FU could be of clinical interest for the development of immunochemotherapeutic protocols based on CEA protein as the target molecule.

Correlation between tumor-associated glycoprotein 72 mucin levels in tumor and serum of colorectal patients as measured by the quantitative CA 72-4 immunoassay

Colorectal tissue biopsies were obtained from 110 patients diagnosed with primary colorectal carcinoma (tumor and normal colonic mucosa samples), 20 patients diagnosed with benign colorectal disease, and 31 healthy donors. The level of expression of tumor-associated glycoprotein 72 (TAG-72) was quantitatively measured in each sample using a double-determinant RIA with monoclonal antibodies B72.3 and CC49 and detecting the sialyl-Tn epitope; this assay was termed CA 72-4. Statistical analysis revealed a significant (approximately 10-fold) increase of TAG-72 expression in the colon tumor biopsies when compared with the expression in normal colonic mucosa from the same patients. A regression analysis revealed a significant correlation (r = 0.459; P < 0.001) between TAG-72 levels measured in biopsies from the tumor lesions and those found in the corresponding normal colonic mucosa. Furthermore, regression analysis showed a significant positive correlation between TAG-72 levels in the tumors and sera of the same patients (r = 0.491; P < 0.001). TAG-72 levels in normal colonic mucosa from healthy donors and patients diagnosed with colorectal cancer were compared. TAG-72 expression was 5-fold higher in the normal mucosa from the colorectal carcinoma patients. No relationship between TAG-72 tumor tissue content and stage of disease was found. Moreover, the correlation between TAG-72 distribution and degree of tumor differentiation observed (P < 0.05) was not any more evident when mucinous carcinomas were excluded. Finally, the results provide further evidence that TAG-72 may be considered an important early marker for colorectal cancer and/or other dysplastic colonic diseases. The statistical correlation between TAG-72 levels in tumors and circulating TAG-72 indicates that patients with elevated levels of serum TAG-72, as measured by the CA 72-4 assay, would be most suited for diagnostic and/or therapeutic intervention with the anti-TAG-72 monoclonal antibodies B72.3 or CC49 or vaccine trials using the sialyl-Tn epitope.

Clinical utility of CA 72-4 serum marker in the staging and immediate post-surgical management of gastric cancer patients

CA 72-4 is a high molecular weight, pancarcinoma human tumor mucin which may play an important role in the identification (i.e., staging) and clinical management of patients with gastric carcinoma. In the present study of 242 patients with primary or recurrent gastric cancer, a higher percentage of these patients had measurable serum CA 72-4 levels when compared with either CA 19.9 or CEA. Moreover, the presence of positive serum CA 72-4 levels correlated with the presence of lymph node involvement and with the identification of patients with a poor prognosis due to the presence of an advanced stage of gastric cancer. Post-operative monitoring of serum CA 72-4 revealed that the disappearance of CA 72-4 often indicated curative surgery which correlated with a longer disease-free interval. Additional clinical studies are needed to better evaluate the role of CA 72-4 as a serum marker for human gastric carcinoma. Concomitant studies should also focus on what role CA 72-4 may play in the initiation and/or progression of the gastric carcinoma phenotype.

TAG-72 expression and its role in the biological evaluation of human colorectal cancer

Immunohistochemical studies showed that TAG-72 is expressed in more than 80% of colorectal carcinomas, but is rarely expressed in normal epithelium and benign diseases. TAG-72 can also be found in the body fluids of patients with adenocarcinomas, and its direct measurement can be used in conjunction with immunocytochemical analysis to help in discriminating benign from malignant effusions. The evaluation of TAG-72 in serum of colorectal carcinoma patients showed a sensitivity of approximately 40%, comparable to that of the widely used CEA. TAG-72 serum levels correlate with the stage of disease, suggesting its utility in discriminating between early-stage versus late-stage colon carcinoma. Longitudinal studies demonstrated that TAG-72 serum levels may be used as a predictive marker of recurrences. Moreover, the simultaneous measurement of TAG-72 and CEA serum markers improves the monitoring of recurrent disease. Therefore, these data suggest that TAG-72 is a well suitable marker for colorectal cancer.

Systemic administration of recombinant interferon alfa in carcinoma patients upregulates the expression of the carcinoma-associated antigens tumor-associated glycoprotein-72 and carcinoembryonic antigen

PURPOSE

The ability of interferons (IFNs) to enhance tumor-associated antigen expression may be an important approach to enhance the efficacy of some monoclonal antibody (MAb)-based protocols for tumor diagnosis and/or therapy. The present study was designed to determine whether systemic IFN alpha-2a administration (via the intramuscular [IM] route) could upregulate the expression of tumor-associated glycoprotein-72 (TAG-72) and/or carcinoembryonic antigen (CEA) at histologically confirmed sites of carcinoma.

PATIENTS AND METHODS

Eighteen patients diagnosed with gastrointestinal (GI) carcinoma received systemic IFN alpha-2a according to four dose schedules. In cohorts I and II, patients received two injections of 3 or 6 x 10(6) U IFN alpha-2a per injection, respectively. Patients in cohorts III and IV received the same doses of IFN alpha-2a, 3 and 6 x 10(6) U, respectively, but three injections were given. Tumor and normal colonic mucosa biopsies were obtained from each patient by endoscopy before IFN alpha-2a and after IFN alpha-2a at surgery. The levels of TAG-72 and CEA expression were measured by (1) immunohistochemistry and reported as percent antigen-positive tumor cells, as well as the relative staining intensity, and (2) a quantitative radioimmunoassay.

RESULTS

TAG-72 and CEA levels were consistently increased in tumor biopsies taken from patients in cohorts III and IV. For example, of 10 patients treated in cohorts III and IV, eight had enhanced TAG-72 expression when measured either as percentage TAG-72-positive tumor cells or as an increased MAb staining intensity following IFN alpha-2a. CEA expression in tumor biopsies from seven of 10 patients in cohorts III and IV was also elevated following IFN alpha-2a treatment. Quantitative analysis of TAG-72 and CEA levels in tumor biopsies confirmed higher tumor antigen levels following IFN alpha-2a administration. No such increases in TAG-72 or CEA levels were observed in tumor samples taken from patients in cohorts I and II. CEA or TAG-72 expression in samples of histologically confirmed normal colonic mucosa showed little or no change after IFN alpha-2a treatment.

CONCLUSION

Systemic IFN alpha-2a administration can upregulate TAG-72 and CEA expression at distal tumor sites, which may play an important role in immunodiagnosis and therapy.

Novel approaches to tumor detection and therapy using a combination of monoclonal antibody and cytokine

Cytokine-based tumor antigen augmentation is one of the approaches researchers and clinicians are using to improve the effectiveness of MAb-directed tumor diagnosis and therapy. Other efforts encompass the use of dose-fractionation for multiple administrations of radioimmunoconjugates, exploitation of genetic engineering to construct antibody molecules with specific biological properties (i.e., altered pharmacokinetics, activation of cellular immune responses, etc.) and use of MAb-directed conjugates that can enhance tumor MAb uptake by altering tumor perfusion. The studies summarized here as well as those from other laboratories have served as the framework for clinical investigations designed to determine the effectiveness of the interferons and other differentiation-inducing agents to alter the tumor antigen phenotype in patients. In an earlier study, patients given IFN-alpha had improved tumor uptake of an antimelanoma MAb. Subsequently, we reported that i.p. IFN-gamma administration substantially upregulated TAG-72 and CEA on the surface of human tumor cells isolated from malignant ascites. A seminal investigation showed significant increase of TAG-72 and CEA levels in tumor biopsies from patients diagnosed with colorectal carcinoma and given systemic IFN-alpha. Those studies led to a clinical trial in which late stage breast cancer patients were administered interferon in combination with therapeutic doses of CC49. Some clinical responses were observed, however, the cytokine and MAb combination may have also enhanced marrow toxicity. Future studies will continue to evaluate the ability to enhance tumor antigen expression in the context of genetically engineered MAbs designed to minimize normal organ toxicity.

Improved immunotherapy of a recombinant carcinoembryonic antigen vaccinia vaccine when given in combination with interleukin-2

Interleukin-2 (IL-2) has been an effective immune modulator in several active-specific immunotherapy experimental protocols using either viral or oncolysate-based vaccines. In this report, data indicate that IL-2 administration can appreciably augment the therapeutic effect of a single immunization of a recombinant vaccinia virus-carcinoembryonic antigen (rV-CEA) vaccine using a CEA-expressing syngeneic experimental murine model system. A single rV-CEA immunization of C57BL/6 mice bearing palpable CEA-positive colon adenocarcinoma tumors results in complete tumor regression in approximately 20% of the mice. The addition of a course of low-dose IL-2 results in complete tumor regression in 60-70% of the mice. Moreover, the combination of rV-CEA and IL-2 induces systemic immunity, which protects those tumor-free mice from subsequent rechallenge with the CEA-expressing tumor cells. No such tumor regression or protection was observed in those mice immunized with the wild-type vaccinia vaccine (V-Wyeth) alone or with IL-2 administration alone. Cellular immune assays revealed that the addition of IL-2 to rV-CEA immunization significantly increased the CEA-specific T-cell proliferative responses as well as the cytolytic T-cell responses when compared with rV-CEA immunization alone. The enhanced CEA-specific immune response, coupled with the improved experimental therapeutic outcome following IL-2 administration, suggests that treatment with that cytokine may effectively substitute for multiple rV-CEA immunizations in active-specific immunotherapy clinical protocols directed at CEA-expressing tumors.

In vitro infection of leukemic bone marrow with HTLV-I generates immortalized cell lines expressing T or myeloid cell phenotype

Leukemic bone marrow cells ( > 90% blasts) of a patient with acute myeloblastic leukemia (AML), non-treated or pretreated in vitro with a mutagenic triazene compound, were infected with HTLV-I by coculture with irradiated virus-donor cells. Immortalized, HTLV-I+, double-positive CD4/CD8 euploid T cell lines, expressing HLA class I/II monomorphic determinants, and inappropriate myeloid and progenitor cell markers (ie CD13, CD14, CD15 and CD33 antigens) were obtained. In one out of 10 triazene-pretreated samples, HTLV-I infection resulted in the appearance of a rapidly growing triploid cell line (ie MTLC1 line) showing: (1) myeloid but not lymphoid phenotype; (2) beta and delta T cell receptor in germline configuration; (3) integrated, complete and incomplete HTLV-I provirus genome (also detected in a number of MTLC1 clones); (4) a high percentage of cells positive for non-specific cross-reacting antigen (a CEA-related molecule present in myeloid cells) under the influence of gamma-interferon; (5) absence of HLA class I/II antigen expression; (6) absence of tax gene transcription. Blast cell proliferation was marginal or absent when leukemic marrow was not subjected to retroviral infection. These results show that exposure of leukemic bone marrow to HTLV-I can be followed by immortalization of T and myeloid cells. Although no data are available to establish whether tax expression played a role in the early phase of the immortalization process of MTLC1 line, tax gene product was not required for maintaining long-term growth of MTLC1 cells.

Improved tumor radioimmunodetection using a single-chain Fv and gamma-interferon: potential clinical applications for radioimmunoguided surgery and gamma scanning

Previous studies have shown that (a) single-chain antibody binding proteins, or sFvs, localize experimental tumor xenografts (D.E. Milenic et al, Cancer Res., 51: 6363-6371, 1991) and (b) the administration of gamma-interferon (IFN-gamma) increases the expression of a high molecular weight glycoprotein, tumor-associated glycoprotein 72 (TAG-72), which improves mAb-based tumor targeting as well as radioimmunotherapy (J. W. Greiner et al., Cancer Res., 53: 600-608, 1993). The present experimental study was designed to determine whether exploiting those two observations in combination could augment tumor detection. Initial results revealed significant localization of a single-chain antibody binding protein of CC49 (i.e., CC49 sFv), a second generation anti-TAG-72 mAb, to human colon tumor xenografts (HT-29), which express low constitutive TAG-72 levels. IFN-gamma treatment of mice bearing HT-29 tumors significantly increased TAG-72 levels in the tumor xenografts. Increased TAG-72 expression was accompanied by a 2-4-fold augmentation of CC49 sFv localized to the HT-29 tumors, measured by direct quantitation of 125I-labeled CC49 sFv tumor deposition as well as tumor:normal tissue ratios. Enhanced CC49 sFv tumor localization improved HT-29 tumor visualization by external scintigraphy as well as when using a hand-held gamma-detecting probe to discriminate between normal (i.e., heart, hind leg) and tumor tissue. The gamma-detecting probe was the same as that used intraoperatively with 125I-labeled CC49 IgG to identify occult tumors in patients. The present experimental findings indicate that the efficiency by which 125I-labeled CC49 sFv localizes tumor in vivo can be enhanced with IFN-gamma. Results of the present study suggest that (a) the incorporation of an IFN-gamma treatment schema prior to radioimmunscintigraphy may increase the signal from the tumor site(s), thus providing a better discrimination between tumor and background, and (b) combining 125I-labeled CC49 sFv with IFN-gamma will not only reduce the time interval between antibody injection and surgery, but will also increase the efficiency of tumor localization using the intraoperative gamma-detecting probe.

Macrophage colony-stimulating factor enhancement of antibody-dependent cellular cytotoxicity against human colon carcinoma cells

Antibody-dependent cellular cytotoxicity (ADCC) has been suggested to be an important defense mechanism against tumors. The effects of recombinant human macrophage colony-stimulating factor (rhM-CSF) on ADCC activity of human monocytes were investigated. Human peripheral monocytes were pre-incubated for 72 h with rhM-CSF at various concentrations (50, 100, 200, 400 U/ml) and then used as effector cells in a 24-h 111-Indium release assay. Human carcinoma cell lines LS-174T, CBS, and KLE were used as targets to react with anti-carcinoma monoclonal antibodies (mAbs: murine D612, murine CC49, and chimeric CC49). A significant increase in ADCC activity was observed after monocytes were incubated in 100-400 U/ml of human rhM-CSF. Variation in ADCC activity of monocytes among donors was observed. The enhancement of ADCC activity was blocked by the addition of a neutralizing antibody to rhM-CSF. Less D612 mAb was required for the rhM-CSF-treated monocytes to mediate an equivalent level of ADCC activity as compared to the untreated monocytes. Because of the low levels of rhM-CSF required in these studies to enhance ADCC, treatment of monocytes alone with comparable levels of rhM-CSF did not enhance antibody-independent cytotoxicity. Moreover, it is demonstrated here that recombinant human interleukin-4 (rhIL-4) and rhM-CSF can have a synergistic effect of monocyte-mediated ADCC on human tumor cells. These results thus indicate that rhM-CSF augments ADCC of human peripheral blood monocytes using mAbs to human carcinomas, suggesting a potential role for rhM-CSF in cancer immunotherapy.

Synergistic effects of IL-6 and IFN-gamma on carcinoembryonic antigen (CEA) and HLA expression by human colorectal carcinoma cells: role for endogenous IFN-beta

When administered as single agents, both interferon gamma (IFN-gamma) and interleukin 6 (IL-6) significantly increase carcinoembryonic antigen (CEA) and HLA class I antigen expression on the surface of human colorectal tumour cells. Studies were carried out to determine whether by combining those cytokines a synergistic enhancement of CEA and HLA expression could result. The findings revealed that the administration of 20 units IFN-gamma along with 1.7 ng IL-6, concentrations of each cytokine that individually induced minimal antigenic changes, together synergistically increased CEA and HLA class I as well as induced qualitative changes in HLA expression on WiDr human colon carcinoma cells. The magnitude of the synergistic increases in CEA and HLA class I expression were reminiscent of the level of antigen augmentation observed when administering 20- to 100-fold higher amounts of each cytokine as a single agent. Also, the addition of IL-6 potentiated the IFN-gamma induction of HLA class II expression. The combined administration of IL-6 potentiated the IFN-gamma did not have any additive or synergistic effects on the growth suppression of those tumour cells. Interestingly, utilization of specific neutralizing antibodies for type I interferons abrogated the increases of CEA and HLA expression seen with IL-6 treatment alone or in combination with IFN-gamma. Moreover, reverse transcriptase/polymerase chain reaction analyses revealed a constitutive expression as well as a temporal increase of IFN-beta mRNA transcripts in colon tumour cells treated with IL-6. Therefore, the findings provide indirect evidence that IFN-beta production seems to play a critical role in the ability of IL-6 to upregulate antigen expression alone or in combination with IFN-gamma. These findings provide insight into cytokine combinations that synergistically upregulate tumour-associated and normal HLA antigen expression on the surface of human tumour cells. Those results provide the rationale for the combined use of such cytokines to heighten tumour cell recognition in monoclonal antibody- or cell-mediated-based immunotherapeutic approaches.

CA 72-4 serum marker--a new tool in the management of carcinoma patients

Among the new tumor markers that have been recently proposed, CA 72-4 is of particular interest, not only for its capabilities in diagnosing and monitoring certain neoplastic diseases, but also for its excellent specificity. Several studies focused on the potential clinical usefulness of CA 72-4 in gastrointestinal (GI) and gynecological cancer, showing a sensitivity of approximately 40% in colorectal and gastric cancer and 50% in ovarian cancer, with an overall specificity of more than 95%. Longitudinal evaluations of patients with either GI or gynecological malignant diseases demonstrated that significant elevations of CA 72-4 serum levels may be predictive of recurrent disease. Moreover, the combination of CA 72-4 with other known serum markers, such as CEA and CA 19-9 for GI cancer or CA 125 for ovarian cancer, indicated that an increase in the sensitivity can be achieved without substantial changes in the overall specificity, improving the possibility of monitoring these patients. In conclusion, these results provide a strong argument for the use of CA 72-4 in the management of these neoplastic diseases.

Evaluation of tumor-associated glycoprotein-72 and CA 125 serum markers in patients with gynecologic diseases

OBJECTIVE

This study was performed to evaluate the clinical values of tumor-associated glycoprotein-72 serum levels alone or in combination with CA 125 in the diagnosis and monitoring of patients with ovarian cancer.

STUDY DESIGN

Serum samples from 293 patients, 142 with primary carcinoma and 151 with benign diseases of the genital tract, were evaluated for the presence of CA 125, tumor-associated glycoprotein-72, and carcinoembryonic antigen. All patients underwent surgery for the primary tumor, and stage was defined according to the classification of International Federation of Gynecology and Obstetrics.

RESULTS

When the measurement of serum tumor-associated glycoprotein-72 is combined with that of CA 125, the sensitivity for the detection of primary ovarian cancer increased from 60% to 73%, with no significant change in specificity, and resulted in a more accurate clinical assessment for detection of residual disease before the second-look procedure. In fact, when both markers were positive, 100% specificity was achieved; conversely, when both markers were negative, no residual disease was found.

CONCLUSION

These findings suggest that tumor-associated glycoprotein-72 may be considered as a supplementary serum marker for CA 125, providing further clinical information for the diagnosis of primary and recurrent ovarian cancer.

Differential effects of recombinant interferon-alpha and 5-fluorouracil against colon cancer cells or against peripheral blood mononuclear cells

Comparative studies on the suppressive effects of recombinant interferon-alpha (IFN-alpha), 5-fluorouracil (5-FU), or IFN-alpha + 5-FU have been performed in vitro on colon carcinoma cells (HT-29 cell line) and PHA-stimulated mononuclear cells (MNC) of peripheral blood obtained from healthy donors. IFN-alpha was used at 500 U/ml against HT-29 cells and at 1000 U/ml against MNC on day 1 of culture; 5-FU was used at 250 microM against HT-29 and at 1400 microM against MNC on day 2 of culture. The results show that: (a) IFN-alpha inhibited MNC and HT-29 cells by 13.4% and 32.9%, respectively; (b) 5-FU inhibited MNC and HT-29 cells by 54.7% and 87.0%, respectively; (c) IFN-alpha + 5-FU resulted in a stronger inhibition of HT-29 cells (i.e., 96.1%). In contrast, that combination was significantly less suppressive than 5-FU alone when MNC were used as targets (i.e., 35.9% inhibition). Natural cell-mediated cytotoxic activity relative to 10(6) MNC was not markedly altered by all agents alone or in combination. Moreover, treatment with IFN-alpha, 5-FU or IFN-alpha + 5-FU resulted in a marked increase in the number of HT-29 cells positive for the CEA surface antigen. These data seem to provide further rational support of the clinical use of IFN-alpha + 5-FU in colorectal cancer, based on the differential toxicity of this drug combination on tumor versus normal immunocompetent cells.

Molecular cloning and characterization of the complementary DNA of an M(r) 110,000 antigen expressed by human gastric carcinoma cells and upregulated by gamma-interferon

An M(r) 110,000 antigen was initially described in human gastric carcinoma cells by its cross-reactivity with anti-carcinoembryonic antigen (CEA) monoclonal antibodies, as well as the ability of gamma-interferon to increase its level of expression. We describe the molecular cloning and sequence analyses of overlapping clones that constitute a full-length complementary DNA that encodes for the entire M(r) 110,000 molecule. The 1.5-kilobase message encodes for a 407-amino acid polypeptide whose structural analysis was consistent with an integral membrane glycoprotein. In particular, the extracellular domain was rich in serine and threonine residues at which carbohydrate substitution is likely through O- and N-linked glycosylation. This would explain the higher molecular weight of the antigen whose polypeptide backbone is approximately M(r) 42,000. Further computer-aided sequence analyses revealed no significant homology with any member of the CEA gene family. The cross-reactivity with anti-CEA monoclonal antibodies may be explained by the presence of CEA and normal cross-reacting antigen homologous sites proximal to the transmembrane region. No sequence homology was found with any known protein. Thus, the M(r) 110,000 molecule represents a potentially novel cell membrane glycoprotein whose possible role in human cancer and/or as a gamma-interferon-inducible gene product warrants further investigation.

Biologic evaluation of tumor-associated glycoprotein-72 and carcinoembryonic antigen expression in colorectal cancer, Part I

Tumor-associated glycoprotein-72 has been recently suggested as a new serum marker for colorectal cancer. In fact, approximately 40 percent of colorectal cancer patients have positive tumor-associated glycoprotein-72 serum levels at the time of diagnosis, while only 3 percent of patients with benign diseases are positive. A longitudinal evaluation of colorectal cancer patients suggested the utility of combining the measurement of tumor-associated glycoprotein-72 with that of carcinoembryonic antigen to monitor disease status not only at the time of diagnosis, but also at the time of recurrence. Several reports have indicated that the expression of some tumor antigens in colorectal adenomas may correlate with those parameters conventionally considered as indicative of malignant transformation. The presence of tumor-associated glycoprotein-72 in colorectal adenomas has been recently correlated with preneoplastic lesions, suggesting that tumor-associated glycoprotein-72 may be considered as an early marker of neoplastic transformation. The evaluation of tumor antigens can be considered a new tool in the management of colorectal cancer.

Improved experimental radioimmunotherapy of colon xenografts by combining 131I-CC49 and interferon-gamma

PURPOSE

This study was designed to determine whether the ability of interferon-gamma to upregulate the expression of a human tumor antigen improved the therapeutic efficacy of a radionuclide-conjugated monoclonal antibody.

METHODS

Tumor xenografts of the moderately differentiated human colon tumor cell line HT-29 were grown in athymic mice. Constitutive levels of the human tumor antigen, tumor-associated glycoprotein-72, were measured before and after treatment with interferon-gamma. Antitumor effects of an 131I-labeled antitumor-associated glycoprotein-72 monoclonal antibody, CC49, were determined by measuring changes in tumor volumes in the respective groups of athymic mice.

RESULTS

Interferon-gamma induced a time-dependent and dose-dependent increase in tumor-associated glycoprotein-72 expression in the HT-29 tumors. Immunohistochemical staining revealed a more homogeneous tumor-associated glycoprotein-72-positive tumor cell population in tumors isolated from mice treated for eight days with interferon-gamma, which accounted for the enhanced tumor localization of 131I-CC49 in mice. That experimental model was used to examine the antitumor effects of combining interferon-gamma with 131I-CC49. Administration of 300 microCi of 131I-CC49 to mice bearing HT-29 tumors induced a transient suppression of tumor growth. Conversely, a long-term, sustained HT-29 tumor growth suppression was achieved in mice given 300 microCi of 131I-CC49 and interferon-gamma. In fact, the cytokine/radioimmunoconjugate combination eradicated any evidence of tumor in approximately 30 percent of the mice.

CONCLUSION

The ability of interferon-gamma to enhance tumor-associated glycoprotein-72 expression substantially augmented the antitumor effects of the radioimmunoconjugate. Those observations provide additional argument for use of a radioimmunoconjugate in combination with a cytokine to improve tumor diagnosis and therapy.

Biological response modifiers as adjuvants in monoclonal antibody-based treatment (review)

Compelling experimental evidence suggest that the use of differentiation-inducing agents which enhance tumor antigen expression may play a pivatal role in MAb-based approaches to tumor diagnosis and/or therapy. In particular, interferons can up-regulate CEA and TAG-72 expression on the surface of human carcinoma cells which leads to an enhanced MAb tumor localization. The ability to target additional MAb to the tumor site has subsequently been shown to augment radioimmunodetection and therapy in experimental models. Initial clinical studies reported that interferon administration to patients diagnosed with malignant melanoma improved the tumor distribution of antimelanoma MAb without an accompanying increase of antibody in normal tissues. The findings from our phase 1A trial clearly showed that intracavitary IFN-gamma administration augmented TAG-72 and CEA expression on carcinoma cells isolated from malignant ascites from patients diagnosed with ovarian or gastrointestinal cancer. Future efforts need to further investigate the molecular mechanisms involved in the regulation of these and other human tumor antigens by the interferons as well as other differentiation-inducing agents. Additional clinical studies should evaluate the overall effectiveness of combining an antigen up-regulation protocol with a conjugated MAb in the hope of improving tumor diagnosis and therapy.

TAG-72 (CA 72-4 assay) as a complementary serum tumor antigen to carcinoembryonic antigen in monitoring patients with colorectal cancer

BACKGROUND

Serum carcinoembryonic antigen (CEA) is the most frequently chosen tumor marker in the clinical diagnosis of colorectal carcinoma and in the long-term monitoring of patients after tumor resection. In recent years, monoclonal antibody technology has identified several new markers of neoplasia, two of which, TAG-72 and CA 19-9, are found in the sera of patients with adenocarcinoma. Serum CEA, TAG-72, and CA 19-9 were evaluated in 300 patients with either malignant (n = 200) or benign (n = 100) colorectal disease.

METHODS

Serum CEA, TAG-72 (CA 72-4), and CA 19-9 antigen levels were determined with a double-determinant radioimmunometric assay kit. Samples and appropriate standards were assayed in duplicate. The cutoff limits used for each assay were indicated by the manufacturer. All of the results of the CA 72-4, CEA, and CA 19-9 serum assays were separated from the clinical information until the study was completed.

RESULTS

Of the 200 patients with colorectal carcinoma, the percentage of patients whose serum samples were positive for CEA, TAG-72, or CA 19-9 was 43%, 43%, and 27%, respectively. The measurement of TAG-72 with CEA for patients with primary or recurrent colorectal carcinoma increased substantially (to 60%) the percentage of positive serum samples when compared with measuring each serum tumor marker alone. Moreover, the apparent advantage gained by measuring the two tumor markers was achieved with little increase in the number of false-positive results.

CONCLUSIONS

The findings support previous observations of complementary expression of TAG-72 and CEA and indicate that a significant advantage could be gained in the detection of primary and, perhaps, recurrent colorectal carcinoma by incorporating the measurement of serum TAG-72 with that of CEA.

TAG-72 (CA 72-4 assay) as a complementary serum tumor antigen to carcinoembryonic antigen in monitoring patients with colorectal cancer

BACKGROUND

Serum carcinoembryonic antigen (CEA) is the most frequently chosen tumor marker in the clinical diagnosis of colorectal carcinoma and in the long-term monitoring of patients after tumor resection. In recent years, monoclonal antibody technology has identified several new markers of neoplasia, two of which, TAG-72 and CA 19-9, are found in the sera of patients with adenocarcinoma. Serum CEA, TAG-72, and CA 19-9 were evaluated in 300 patients with either malignant (n = 200) or benign (n = 100) colorectal disease.

METHODS

Serum CEA, TAG-72 (CA 72-4), and CA 19-9 antigen levels were determined with a double-determinant radioimmunometric assay kit. Samples and appropriate standards were assayed in duplicate. The cutoff limits used for each assay were indicated by the manufacturer. All of the results of the CA 72-4, CEA, and CA 19-9 serum assays were separated from the clinical information until the study was completed.

RESULTS

Of the 200 patients with colorectal carcinoma, the percentage of patients whose serum samples were positive for CEA, TAG-72, or CA 19-9 was 43%, 43%, and 27%, respectively. The measurement of TAG-72 with CEA for patients with primary or recurrent colorectal carcinoma increased substantially (to 60%) the percentage of positive serum samples when compared with measuring each serum tumor marker alone. Moreover, the apparent advantage gained by measuring the two tumor markers was achieved with little increase in the number of false-positive results.

CONCLUSIONS

The findings support previous observations of complementary expression of TAG-72 and CEA and indicate that a significant advantage could be gained in the detection of primary and, perhaps, recurrent colorectal carcinoma by incorporating the measurement of serum TAG-72 with that of CEA.

Transfer of the IL-6 gene into a human colorectal carcinoma cell line and consequent enhancement of tumor antigen expression

cDNA encoding the human IL gene (580 bp), inserted into a retroviral expression vector carrying neomycin resistance selective marker, was introduced into HT-29 human colon carcinoma cells by lipofection. Interleukin-6 activity was measured by ELISA and bioassay using B9 cells. Interleukin-6 secreted by transfected HT-29 cells was shown to be biologically active. The expression of the human tumor associated antigen CEA (carcinoembryonic antigen), HLA classes I and II, and ICAM-1 antigens in the transfected HT-29 cells were also analyzed by flow cytometry. Significant enhancement in the expression of CEA but not in the expression of HLA class I, HLA class II and ICAM-1 antigens, was observed in the transfected HT-29 cells as compared to the parental HT-29 cells. These results provide experimental evidence that enhancement of tumor antigen expression on tumor cells can be induced by IL-6 gene transfection, and suggest another potential role for the use of IL-6 gene transfer in the immunotherapy of human cancers.

A human T cell line engineered to secrete chimeric monoclonal antibody

Both monoclonal antibodies (MAbs) and human T cells have been used in human tumor immunotherapy protocols. Tumor-infiltrating lymphocytes (TILs) and MAbs that can mediate antibody-dependent cell-mediated cytotoxicity (ADCC) via human effector cells have shown antitumor effects in both animal models and clinical trials. One potential novel approach would be to combine these two modalities in the creation of a T cell capable of secreting antitumor immunoglobulins (Ig), in essence, creating an antitumor Ig "factory" at the tumor site. In the studies reported here, we have cloned the D612 MAb Ig genes and generated a chimeric D612 IgG1 containing the murine variable region and human constant region. D612 MAb has been shown to mediate lysis of human colon carcinomas via effector cell-mediated ADCC. We have demonstrated that following transfection, chimeric D612 can be expressed and secreted by the human T-cell line MOLT-4 at a rate of 0.25 micrograms/ml per 10(6) cells in 72 hours. The secreted Ig retained its antigen-binding properties as assayed by competition radioimmunoassay and also its ability to mediate ADCC against human tumor cells. To our knowledge, this is the first demonstration of the production of a chimeric IgG by human T cells and opens the possibility of a therapeutic approach in which TILs secrete humanized antitumor MAb capable of mediating ADCC at the tumor site.

Improved radioimmunotherapeutic efficacy of an anticarcinoma monoclonal antibody (131I-CC49) when given in combination with gamma-interferon

The moderately differentiated human colon tumor cell line, HT-29, constitutively expresses low levels of the high molecular weight mucin, tumor-associated glycoprotein 72 (TAG-72), and the M(r) 180,000 carcinoembryonic antigen (CEA) when grown as s.c. tumors in athymic mice. We report that the in vivo administration of gamma-interferon (IFN-gamma) resulted in a time- and dose-dependent increase in both TAG-72 and CEA expression in the HT-29 tumors. Immunohistochemical staining revealed a more homogeneous TAG-72-positive tumor cell population after IFN-gamma. Furthermore, both anti-TAG-72 and anti-CEA monoclonal antibodies (MAbs) showed enhanced localization to the HT-29 tumors in mice treated with IFN-gamma. Using that experimental model, subsequent studies presented evidence showing that the combination of IFN-gamma with 131I-CC49, an anti-TAG-72 MAb, resulted in a statistically significant improvement in therapeutic efficacy when compared with 131I-CC49 alone. For example, treatment with 300 microCi of 131I-CC49 initially suppressed HT-29 tumor growth; however, that reduction in tumor growth was transient as evidenced by the emergence of additional tumor growth at later time points. In contrast, an 8-day treatment with IFN-gamma in combination with 300 microCi 131I-CC49 resulted in sustained suppression of HT-29 tumor growth. Thus, IFN-gamma in vivo can substantially increase the TAG-72 expression in human colon tumor xenografts which leads to an increased tumor localization of anti-TAG-72 MAbs and seems to be responsible for the enhanced antitumor effects when IFN-gamma was combined with 131I-CC49. The results provide further evidence for including a biological response modifier, such as IFN-gamma, which can increase the expression of specific tumor antigens (i.e., TAG-72 and CEA) subsequently leading to a dramatic improvement in the antitumor efficacy of a radionuclide-conjugated MAb.

Comparison of the interferon-gamma-mediated regulation of tumor-associated antigens expressed by human gastric carcinoma cells

The regulation by interferon-gamma (IFN-gamma) of the expression of seven distinct human tumor-associated antigens [M 110,000, carcinoembryonic antigen (CEA), nonspecific crossreacting antigen (NCA), CA19-9, 17-1A, TAG-72, and D612] was studied in eight human gastric cancer cell lines. Six of the seven tumor antigens have been well-characterized and reported to be expressed by human gastric carcinomas. The M(r) 110,000 antigen has been recently identified in six of the eight human gastric cancer cell lines and may represent a potentially novel gastric tumor antigen. IFN-gamma administration substantially increased the expression of the M(r) 110,000 antigen in six gastric tumor cell types, and, furthermore, induced its expression de novo in another gastric tumor cell line (GaCa). Constitutive CEA and NCA expression was detected on the surface of five of the eight gastric carcinoma cell lines. IFN-gamma treatment induced only a modest increase in the level of expression of those related antigens, but those changes were accompanied by increases in the level of the respective mRNA transcripts. Four other human tumor-associated antigens, TAG-72, CA19-9, D612, and 17-1A, were found either to be not constitutively expressed and/or not regulated by IFN-gamma. The results indicate the selective nature by which IFN-gamma regulates the M(r) 110,000 antigen and, to a lesser extent, the antigens of the CEA gene family.

Interleukin-6 increases carcinoembryonic antigen and histocompatibility leukocyte antigen expression on the surface of human colorectal carcinoma cells

Human colorectal carcinoma cells that were treated in vitro with interleukin-6 (IL-6) expressed increased levels of carcinoembryonic antigen (CEA) and normal histocompatibility leukocyte antigen (HLA) class I on their cell surface. The IL-6 mediated increase of CEA expression on the surface of a moderately differentiated colon carcinoma cell line (WiDr) was time- and dose-dependent. A 5-day treatment of the WiDr cells with 100 U IL-6/ml increased the percentage of cells that expressed CEA from 29 to > 80% and enhanced the level of HLA class I expression. The increase in CEA expression as a result of IL-6 treatment was also observed using SDS-PAGE/Western blot analyses, and subsequent Northern blot analyses revealed concomitant increases in CEA-related mRNA transcripts. A comparison of the increases in CEA expression after IL-6, interferon-beta, and interferon-gamma on a nanomolar basis revealed that IL-6 was more potent than either of the interferons. Of 11 different human colorectal tumor cell lines that were treated with IL-6, CEA and/or HLA class I expression were increased in five. Thus, IL-6 can act directly on human colon carcinoma cells and selectively increase the expression of CEA and HLA class I antigens, which may provide some insight into the mechanisms involved in the ability of IL-6 to suppress in vivo tumor growth.

Intraperitoneal administration of interferon-gamma to carcinoma patients enhances expression of tumor-associated glycoprotein-72 and carcinoembryonic antigen on malignant ascites cells

PURPOSE

The study was designed to determine whether in vivo interferon gamma (IFN-gamma) administration could enhance tumor antigen expression on the surface of human tumor cells.

MATERIALS AND METHODS

Eight patients (six with ovarian and two with gastrointestinal tumors) with a diagnosis of adenocarcinoma with secondary malignant ascites were given weekly escalating doses of IFN-gamma (ie, 0.1 to 100 MU) intraperitoneally (IP) each week for 8 weeks. Tumor cells were isolated from the patients' ascites samples, which were collected three times per week: before and 24 and 48 hours post-IFN-gamma administration. The level of expression of tumor-associated glycoprotein-72 (TAG-72) and carcinoembryonic antigen (CEA) was measured using flow cytometry and immunocytochemistry.

RESULTS

IFN-gamma administered IP dramatically increased TAG-72 (as measured by binding of anti-TAG-72 monoclonal antibodies [MoAbs] B72.3 and CC 49) and CEA (measured by MoAb COL-1) expression on the surface of the carcinoma cells. The ascites-derived tumor cells from seven of the eight patients constitutively expressed TAG-72, and the level of TAG-72 expression was increased by IFN-gamma in all seven patients, as evidenced by the enhanced binding of anti-TAG-72 MoAbs to the tumor-cell surface. In some cases, IFN-gamma treatment increased the percentage of MoAb B72.3-reactive tumor cells from 10% to greater than 90%, and those changes were further corroborated by similar increases in the MoAb staining intensity observed with immunoperoxidase analysis. In addition, ascites-derived tumor cells from two patients with gastrointestinal carcinoma also expressed enhanced CEA levels after IFN-gamma. The increased TAG-72 and CEA expression were observed at low IFN-gamma doses (ie, 0.1 to 1.0 MU), which were well tolerated by all patients.

CONCLUSIONS

The ability of IFN-gamma given IP to increase TAG-72 and CEA expression on tumor cells in vivo provides additional argument for the use of the cytokine as an adjuvant to enhance MoAb binding to human carcinoma-cell populations.

CA 72-4 measurement of tumor-associated glycoprotein 72 (TAG-72) as a serum marker in the management of gastric carcinoma

The presence of three distinct serum markers of carcinoma, tumor-associated glycoprotein 72 (TAG-72; as measured by the CA 72-4 assay), CA 19-9, and carcinoembryonic antigen (CEA), was evaluated in 194 patients diagnosed with either malignant (n = 94) or benign (n = 100) gastric disease. Of the 94 patients diagnosed with gastric carcinoma, the percentage of patients whose serum samples were positive for TAG-72, CA 19-9, or CEA was 42.6, 31.9, and 20.2%, respectively. Furthermore, fewer false positive samples were observed for TAG-72 than either CA 19-9 or CEA. The analysis of serum TAG-72, CA 19-9, and CEA levels in patients diagnosed with early (stage I and II) versus advanced (stage III and IV) disease revealed a significantly higher level of TAG-72 and CA 19-9 in the serum of patients with advanced stage gastric carcinoma. The serum samples were also analyzed to determine whether any advantage might be gained by simultaneously measuring two or more of the tumor markers. The data clearly indicate that the measurement of TAG-72 with CA 19-9 significantly increased the percentage of gastric carcinoma patients with positive serum levels of either antigen. This advantage was achieved with no significant increase in the number of false positives. Twenty-one patients were followed postsurgically for up to 3 years to determine whether the appearance or reappearance of TAG-72, CA 19-9, or CEA accurately predicted disease recurrence. Positive serum TAG-72 levels correlated with disease recurrence in 7 of 10 patients, compared with 5 and 2 patients for CA 19-9 and CEA, respectively. The findings suggest that serum TAG-72 as measured by the CA 72-4 assay may be a useful marker for late stage gastric carcinoma and its measurement alone or in combination with CA 19-9 may have utility in the clinical management of gastric carcinoma.

Monoclonal antibodies in the management of carcinoma patients

The use of monoclonal antibodies (MAbs) in the clinical management of carcinoma patients is reported in the present review. Among the various MAbs generated, MAb B72.3 (LTIB, National Cancer Institute, U.S.A.) has been extensively used in clinical trials either for antigen identification (TAG-72) in sera, or for tumor localization in carcinoma patients. Serum assay results, in colorectal cancer patients, showed the usefulness of the MAb B72.3 in monitoring the clinical course of the malignant disease. Its specific tumor localization (70% of the biopsy specimens) and the immunoscintigraphy studies, after in vivo administration, have also been discussed. The positive results obtained, markedly contributed in the development of a new intraoperative methodology termed "radioimmunoguided surgery".

Tumor-associated glycoprotein-72 serum levels complement carcinoembryonic antigen levels in monitoring patients with gastrointestinal carcinoma. A longitudinal study

Eighty-two patients diagnosed with gastrointestinal (GI) adenocarcinoma were evaluated before and for 26 months after primary tumor resection for the presence of two serum tumor markers: tumor-associated glycoprotein-72 (TAG-72) and carcinoembryonic antigen (CEA). Elevated TAG-72 and CEA serum levels were found preoperatively in 32 (39%) and 34 (41.5%) of the 82 patients, respectively. The percentage of patients with elevated serum levels of either TAG-72 or CEA was 56.1% (46 of 82). Twelve (15%) patients who had normal CEA serum levels had elevated TAG-72 serum levels, and conversely, serum from 14 (17%) patients who were TAG-72 negative were CEA positive. Forty-five of the 82 patients were diagnosed with advanced disease (i.e., Stages C and D for colorectal, Stages III and IV for stomach), and 29 (64.4%) and 26 (57.8%) of those patients had elevated serum levels of TAG-72 or CEA, respectively. Elevated levels of either TAG-72 or CEA, however, were found in sera of 82.2% of patients with advanced GI cancer, which is an increase of 24.4% over the use of CEA antigen alone as a marker of disease. The measurement of both TAG-72 and CEA may improve the diagnosis of patients with GI malignant disease due to the apparent complementary association which exists between these tumor markers. Serum TAG-72 and CEA levels were monitored in 31 patients for varying lengths of time after resection of the carcinoma; 11 patients developed recurrent disease. Sera from nine of 11 (81.8%) of these patients had elevated TAG-72 levels and six of 11 (54.5%) had elevated CEA levels. Tumor marker elevations were observed either before (35 to 166 days) or at the time of diagnosis of recurrence. The elevation of one or both markers correlated with the clinical status in ten of 11 (90.9%) patients with recurrence. In addition, 20 patients who were clinically free of disease after more than 700 days' follow-up had normal serum levels of both TAG-72 and CEA. These findings suggest that the combined use of serum TAG-72 and CEA measurements may improve detection of recurrence in patients with GI cancer and may be useful in the postsurgical management of GI adenocarcinoma patients.