CEA-containing immune complexes in sera of patients with colorectal and breast cancer--analysis of complexed immunoglobulin classes

Novel isoelectric target depletion (ITaD) protocol reduces the need for specific reagents for immunogenicity testing

Background: The development of immunogenicity assays for clinical drug candidates targeting soluble proteins is challenging when the soluble target might produce either false-positive or false-negative signals in bridging anti-drug antibody screening assays. A generic soluble target removal protocol that uses a pH-dependent depletion was evaluated. Results: An anti-drug antibody bridging assay with a pH-dependent soluble target depletion step was successfully developed. Endogenous target levels of ∼600 nM could be depleted below 8 pM. The assay was highly drug tolerant and met regulatory requirements. Conclusion: A reagent-independent target depletion protocol can be used for immunogenicity testing in the presence of a soluble target. The generic protocol circumvents common depletion or masking protocols.

PSA-IgM and iXip in the diagnosis and management of prostate cancer: clinical relevance and future potential. A review

The Prostate Specific Antigen (PSA) is the first filter in the diagnosis of prostate cancer. Unfortunately, it is organ-specific but not cancer-specific. In addition, some prostate cancers are not clinically-significant and their diagnosis and treatment may lead to overdiagnosis and overtreatment. For these reasons, other markers have been proposed in the last years, such as PCA3 and PHI, but none of these are currently used in the clinical practice on large scale. In the last decade, PSA-IgM and the algorithm iXip have emerged for the diagnosis of prostate cancer and showed to perform well in decreasing the detection of clinically-insignificant prostate cancer and in reducing the number of unnecessary prostate biopsies. This review focuses on data reported in the literature on PSA-IgM and iXip as well as on the future perspectives of their usage in the clinical practice on large scale.

The role of immune PSA complex (iXip) in the prediction of prostate cancer

PURPOSE

To analyse the performance of iXip in the prediction of prostate cancer (PCa) and high-grade PCa.

METHODS

A consecutive series of men undergoing MRI/FUSION prostate biopsies were enrolled in one centre. Indications for prostate biopsy included abnormal prostate-specific antigen (PSA) levels (PSA > 4 ng/ml) and/or abnormal digital rectal examination (DRE) and/or abnormal MRI. All patients underwent the evaluation of serum PSA-IgM concentration and the iXip ratio was calculated. Accuracy iXip for the prediction of PCa was evaluated using multivariable binary regression analysis and receiver operator characteristics (ROC) curves.

RESULTS

Overall 160 patients with a median age of 65 (62/73) years were enrolled. Overall, 42% patients were diagnosed with PCa and 75% of them had high-grade cancer (Epstein ≥ 3). Patients with PCa were older and presented higher PSA levels, higher PIRADS scores and lower prostate volumes (PVs). On ROC analysis iXip presented an area under the curve (AUC) of 0.57 in the prediction of PCa and of 0.54 for the prediction of high-grade PCa.

CONCLUSIONS

In our experience, immune PSA complexes are not predictors of PCa. iXip analysis should not be included in the diagnostic pathway of patients at increased risk of PCa.

Immune-complex level of cofilin-1 in sera is associated with cancer progression and poor prognosis in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal malignancies. To improve its outcome, reliable biomarkers are urgently needed. In this study, we aimed to elucidate the key molecules involved in PDAC progression using proteomics approaches. First, we undertook 2‐D electrophoresis to identify the proteins overexpressed in PDAC tissues. Following the analysis of agarose gel spots, cofilin‐1 was identified and verified as a candidate protein commonly upregulated in PDAC tissues. In immunohistochemistry, cofilin‐1 was strongly expressed in the cytoplasm of PDAC cells. Samples were divided into two groups based on the level of cofilin‐1 expression. The high expression group showed significantly higher incidence of hematogenous dissemination in relapsed patients than the low expression group (P = 0.0083). In in vitro experiments, knockdown of cofilin‐1 significantly decreased chemotaxis in PDAC cell lines. After we confirmed that cofilin‐1 was secreted from PDAC cells, we established a detection system for the immune‐complex of cofilin‐1 in sera. Using this system, we measured the IC levels of cofilin‐1 in sera and observed that the IC levels of cofilin‐1 in PDAC patients were higher than those in healthy volunteers and patients with pancreatitis (PDAC vs. healthy volunteers, P < 0.0001; PDAC vs. patients with pancreatitis, P < 0.026). Notably, the IC levels of cofilin‐1 showed a stepwise increase during PDAC progression (P = 0.0034), and high IC levels of cofilin‐1 indicated poor prognosis of patients after surgery (P = 0.039). These results suggest that the IC of cofilin‐1 in sera is a potentially attractive serum biomarker for the prognosis of PDAC.

High-throughput screening for native autoantigen-autoantibody complexes using antibody microarrays

We report on a novel, high-dimensional method to detect autoantibodies that are complexed with their natural autoantigens. Specifically, autoantibody-autoantigen complexes in serum or plasma are directly incubated onto a high-density antibody microarray. Detection of the bound autoantibody-antigen complex is made via fluorescently labeled antihuman immunoglobulin G or other immunoglobulin isotype secondary antibodies and quantification in a microarray scanner. Uncomplexed antibodies do not interfere with this assay. The whole process is very rapid and applicable for high-throughput screening without the need for production of proteins or immunoglobulin purification from the samples. Using these methods, we found that plasma from healthy individuals contains hundreds of autoantibodies complexed with cellular proteins. Thus, this highly sensitive, multiplex method is capable of discovering new autoantibody-antigen or circulating immune complexes, many of which will likely be useful for disease detection and characterization.

Circulating Natural IgM Antibodies Against Angiogenin in the Peripheral Blood Sera of Patients with Osteosarcoma as Candidate Biomarkers and Reporters of Tumorigenesis

BACKGROUND

Tumor immunology research has led to the identification of a number of tumor-associated self antigens, suggesting that most tumors trigger an immunogenic response, as is the case in osteosarcoma, where the detection of natural serum IgM antibodies might achieve the diagnosis of osteosarcoma. Natural IgM antibodies to tumor-associated proteins may expand the number of available tumor biomarkers for osteosarcoma and may be used together in a serum profile to enhance test sensitivity and specificity. Natural IgM antibodies can be consistently detected in the peripheral blood sera months to years before the tumor is diagnosed clinically. The study of the level of a potential biomarker many months (or years) prior to diagnosis is fundamentally important. Integrated circulating and imaging markers in clinical practice treating osteosarcoma have potential applications for controlling tumor angiogenesis.

OBJECTIVES

To study the expression of natural IgM antibodies to the tumor antigens of angiogenesis in the peripheral blood sera of osteosarcoma patients and healthy individuals, and to develop serum-based predictive biomarkers.

METHODS

Peripheral venous blood samples were collected from 117 osteosarcoma patients and 117 patients with other tumors. All diagnosis was histologically confirmed. Staging of patients was performed according to the Enneking Surgical Staging System. The control group consisted of 117 age- and sex- matched healthy individuals. In this study, novel immunoconjugates were designed, synthesized and then used to develop a rapid, specific and sensitive enzyme-linked immunosorbent assay (ELISA) method to detect angiogenin (ANG)-IgM directly in the peripheral blood sera of humans.

RESULTS

Serum ANG-IgM levels are significantly higher in osteosarcoma patients than in healthy individuals (P < 0.005). Serum ANG-IgM levels varied widely, but were highly dependent on the concentration of IgM (r = 0.85; P < 0.0005). We found ANG-IgM in the sera of 85% of newly diagnosed osteosarcoma patients and ANG-IgM levels were significantly higher in osteosarcoma patients compared to any other tumors (P < 0.001).

CONCLUSIONS

These results demonstrated that the combined biomarker ANG-IgM has greater sensitivity and specificity in early diagnosis of osteosarcoma patients than the traditional biomarkers (ANG and vascular endothelial growth factor). Circulating ANG-IgM immune complexes can potentially serve as a biomarker for increased risk of osteosarcoma, because relatively high serum levels were also detected in otherwise healthy individuals with a first degree family history of osteosarcoma and in patients with a diagnosis of benign conditions. Immunological aspects of angiogenesis for managing osteosarcoma will have a practical value in early diagnosis, prognosis and monitoring response to antiangiogenic therapy.

Detection of prostate-specific antigen coupled to immunoglobulin M in prostate cancer patients

BACKGROUND

Several reports indicate that the main biomarkers for liver and colorectal cancer circulating in the blood stream associate with immunoglobulin M (IgM) to form stable complexes that show increased diagnostic relevance compared to circulating free biomarkers.

METHODS

To further investigate the association between cancer biomarkers and IgM, we assessed the presence of prostate-specific antigen (PSA) as IgM complexes in sera of patients with prostate cancer (PC) or benign prostatic hyperplasia (BPH) in comparison with PSA measurements.

RESULTS

PSA-IgM levels were significantly elevated in 40% (20/50) and 12% (6/51) of PC and BPH patients, respectively, compared to 22% (11/50) and 29% (15/51) of PSA positive patients in the same groups. Detection of cancer markedly increased from 22 to 60% by co-determination of both markers (30/50 patients). Significantly elevated levels of PSA-IgM were found in 13 out of 30 patients affected by PC with a PSA value between 4 and 10 ng/mL and only in 4 out of 34 BPH patients in the same PSA range.

CONCLUSIONS

The results are the first evidence of the occurrence of PSA-IgM complexes in patients with prostate cancer. The gain achieved in cancer detection by using the combination of PSA and PSA-IgM suggests that PSA-IgM could be a complementary serological marker of prostate cancer.

Individual mouse analysis of the cellular immune response to tumor antigens in peripheral blood by intracellular staining for cytokines

Among the experimental animal models, mice remain the most widely used for the evaluation of immunotherapeutic strategies. Vaccines against parasites and viral antigens are commonly administered to the appropriate mouse strain which also allows testing of the therapeutic effect. Similarly, in mice transgenic for human tumor associated antigens (TAA), cancer vaccines must lead to breakage of immune tolerance to elicit a significant effect on the tumor. However, one of the major drawbacks in the monitoring of cellular immune responses induced by vaccination is that functional immunological assays require suppression of the animals to collect the spleen or lymph nodes for analysis. Here, we report the application of a rapid intracellular staining (ICS) method to quantify antigen-specific T cells responses in small volumes of murine blood. Genetic vaccination with plasmid DNA followed by electroporation (DNA-EP) and the use of adenoviral vectors (Ad) encoding CEA as a model target antigen were applied to different strains of mice. Optimal blood volume, number of lymphocytes, sensitivity and reproducibility of intracellular staining for IFN-gamma were determined both in non-tolerant/wild type mice as well as in tolerant CEA transgenic mice upon restimulation of PBMCs with CEA peptides. Groups of vaccinated mice were then sacrificed and PBMCs and splenocytes from individual animals were compared for intracytoplasmic detection of IFN-gamma and TNF-alpha. A significant correlation was observed between splenic and blood immune responses. Finally, the cellular immune response was followed over time in groups of vaccinated mice. The kinetics of IFN-gamma producing effectors were measured after priming and successive boosting with adenoviral vectors. We show that intracellular staining for mouse PBMCs is a rapid and simple method to measure antigen-specific immune responses. It does not require animal euthanasia and mirrors the response observed in lymphoid organs such as the spleen.

Squamous cell carcinoma antigen-immunoglobulin M complexes as novel biomarkers for hepatocellular carcinoma

BACKGROUND

Early detection of hepatocellular carcinoma (HCC), one of the most common and deadly tumors worldwide, still is difficult due to the lack of adequate biomarkers that show high sensitivity and specificity. The authors recently demonstrated that squamous cell carcinoma antigen (SCCA) variants were overexpressed remarkably in all surgically resected HCCs.

METHODS

For the current study, the authors assessed the presence of SCCA, as a free form and complexed with immunoglobulins, in serum from patients with HCC, cirrhosis, and chronic hepatitis and from healthy control participants and compared SCCA measurement with the measurement of alpha-fetoprotein (AFP) levels.

RESULTS

Circulating immune complexes (ICs) composed by SCCA and immunoglobulin M (IgM) IC (SCCA-IgM IC) were undetectable (< 120 arbitrary units [AU]/mL) in serum from a healthy control population (0 of 73 controls); however, 35 of 50 patients with HCC (70%) were reactive for SCCA-IgM IC independent of etiology (mean +/- standard deviation [SD], 2568.5 +/- 6797.3 AU/mL). No correlation was found with AFP levels, which were elevated significantly in only 21 of 50 patients with HCC (42%). By using an AFP cut-off value of 20 ng/mL, 96% of patients with HCC were positive for at least 1 marker. Among cirrhotic patients, the presence of circulating SCCA-IgM IC was displayed in 13 of 50 patients (26%), but at lower levels compared with the patients who had HCC (mean +/- SD, 147.5 +/- 348.3 AU/mL; P < 0.01; Student t test), whereas 9 of 50 patients with chronic hepatitis (18%) were reactive (mean +/- SD, 39.5 +/- 89.7 AU/mL). No significant presence of free SCCA, free anti-SCCA variants IgG or IgM, or SCCA-IgG IC was found.

CONCLUSIONS

The study results indicated that SCCA-IgM ICs represent novel serologic biomarkers, which, alone or in combination with AFP, can increase the sensitivity for diagnosing HCC significantly.

Phase I study in cancer patients of a replication-defective avipox recombinant vaccine that expresses human carcinoembryonic antigen

PURPOSE

A phase I clinical trial in patients with advanced carcinoma was conducted, using a replication-defective avipox vaccine containing the gene for the human carcinoembryonic antigen (CEA). The canarypox vector, designated ALVAC, has the ability to infect human cells but cannot replicate.

PATIENTS AND METHODS

The recombinant vaccine, designated ALVAC-CEA, was administered intramuscularly three times at 28-day intervals. Each cohort of six patients received three doses of either 2.5 x 10(5), 2.5 x 10(6), or 2.5 x 10(7) plaque-forming units of vaccine.

RESULTS

The vaccine was well tolerated at all dose levels and no significant toxicity was attributed to the treatment. No objective antitumor response was observed during the trial in patients with measurable disease. Studies were conducted to assess whether ALVAC-CEA had the ability to induce cytolytic T-lymphocyte (CTL) responses in patients with advanced cancer. Peripheral blood mononuclear cells (PBMCs) from patients with the MHC class I A2 allele were obtained before vaccine administration and 1 month after the third vaccination. Peripheral blood mononuclear cells were incubated with the CEA immunodominant CTL epitope carcinoembryonic antigen peptide-1 and interleukin 2 and quantitated using CTL precursor frequency analysis. In seven of nine patients evaluated, statistically significant increases in CTL precursors specific for CEA were observed in PBMCs after vaccination, compared with before vaccination.

CONCLUSION

These studies constitute the first phase I trial of an avipox recombinant in cancer patients. The recombinant vaccine ALVAC-CEA seems to be safe and has been demonstrated to elicit CEA-specific CTL responses. These studies thus form the basis for the further clinical exploration of the ALVAC-CEA recombinant vaccine in phase I/II studies in protocols designed to enhance the generation of human T-cell responses to CEA.

Gene therapy for colon cancer

The enormous number of newly diagnosed cases of colorectal cancer that occur each year and the lack of agents that are highly effective for all patients underscore the need for novel approaches to combating the disease. Gene therapy as a developing treatment modality is already well established, with a number of trials ongoing and a vast range of other approaches being assessed in animal and cell culture experiments. In this brief review, we have discussed five gene therapy trials in colon carcinoma that are ongoing or in the approval process in the United States. The gene therapy approaches being employed can be divided into three major categories: (1) enzyme/prodrug systems (HSVtk/ganciclovir; CD/5-fluorocytosine); (2) tumor suppressor gene replacement therapy with wild-type p53; and (3) immune-gene therapy which is based on cytokine or tumor antigen expression to induce tumor immunity (e.g., CEA). Replication-deficient recombinant adenoviral vectors are predominantly used for colon cancer gene therapy, because they can be produced at high titer and they readily infect a number of different cell types. One trial uses polynucleotide therapy for antitumor immunization with intramuscular injection. All of these studies are phase I trials, principally designed to evaluate safety, but they will also provide data on gene delivery. Some trials may provide some insight into potential therapeutic effects. We have alluded to some of the concerns on toxicity related to the use of adenovirus, risks and side effects from transgenes, lack of tumor-specificity of transgene expression, and potential problems with efficient gene delivery to solid tumors. The clinical trials, however, will provide insight that will inform design of future studies with respect to dose, form, and frequency of administration, as well as to the value of biologic and clinical endpoints. The molecular analysis of the fundamental basis of colon cancer has moved at a remarkable pace and that progress seems set to continue. Thus, the basic foundations for gene therapy are undoubtedly in place: a clinical need; growing understanding of basic tumor biology; and ever-improving delivery systems. The field is at a very early stage in its evolution, and one concern is that the considerable hurdles that must be overcome are seen as examples of the failure of cancer gene therapy; however, we believe these challenges will be overcome. The authors also believe that colon cancer gene therapy is likely to take new directions, such as use as adjuvant to radical surgery, rather than attempts to treat end-stage disease when the liver is replaced by metastases. Other new directions might include prophylactic gene-based immunization against a panel of well-characterized tumor antigens, at least for persons shown to be at high risk of colon cancer because of genetic or other predisposition. A marriage between gene therapy approaches and conventional anticancer treatments such as radiotherapy and chemotherapy also seems likely. There is already evidence of this move with demonstration of synergism between p53 replacement and radiotherapy and chemotherapy. It is also likely that therapies will be developed that combine elements from the cancer gene therapies discussed previously, namely, suicide gene transfer, immune modulation, and modulation of defective cancer genes. Perhaps one of the main concerns is not that researchers in cancer gene therapy want to walk before they can run, but that the public and government agencies believe they can. The next 10 years will be an interesting time in the development of novel treatments against colon cancer.

Ultrasensitive heterogeneous immunoassay using photothermal deflection spectroscopy. 2. Quantitation of ultratrace carcinoembryonic antigen in human sera

We previously proposed a photothermal immunoassay based on highly sensitive detection by a photothermal beam deflection method using colloidal gold as a labeling material. The assay system was significantly improved in terms of background reduction of ultrasensitive laser spectrometry through the newly designed reaction and separation procedure using microspheres for a solid phase. Highly sensitive laser spectrometric analysis is often susceptible to interference by even a small amount of admixtures. In this subsequent study, we improved our photothermal immunoassay so that it possesses further selectivity, matching that of the highly sensitive photothermal detection method. It was proved that our method could be applied to determine ultratrace quantities of a carcinoembryonic antigen (CEA) in cancer patients' and normal sera. The lower detection limit of CEA was 0.078 ng/mL (9.8 amol, absolute quantity). This is 10 times superior to that of any other immunoassay method and has enough detectability to measure a low level of CEA in healthy individuals. Intraassay coefficient of variation is about 8% at eight different concentrations (n = 6). We assayed 61 serum samples, and there was a good correlation between this method and previously established ELISA. We obtained clearer demarcation of healthy persons and colon cancer patients in terms of the CEA value than was obtained by ELISA. We believe this is the first report in which the laser-based ultrasensitive immunoassay is proved to be applicable to human sera, although the matrix admixtures causing interference in the assay were quite different in each sample serum.

Strategies for the development of recombinant vaccines for the immunotherapy of breast cancer

The development of recombinant vaccines for specific immunotherapy of carcinoma represents a novel approach for the treatment of breast cancer and other tumor types. This article reviews the various parameters that should be considered in the development of recombinant vaccines. Several breast cancer associated antigens are also discussed which may provide potential target molecules. The human carcinoembryonic antigen (CEA), which is expressed on approximately 50% of breast cancers, represents one such target for immunotherapy. To enhance the immunogenicity of this antigen, a recombinant CEA-vaccinia vaccine, designated rV-CEA, was produced. To study the effects of this vaccine in an animal model, a murine colon carcinoma cell line was transduced with CEA and transplanted into immunocompetent mice for protection and therapy studies. Pre-clinical toxicity studies were also conducted in non-human primates. The results of these studies showed the rV-CEA vaccine to be immunogenic and safe in both rodents and primates, and to elicit good anti-tumor responses in the rodent model. In a Phase I clinical trial in metastatic breast, lung, and colorectal cancer patients involving three immunizations of rV-CEA, at three dose levels, enhancement of T-cell and antibody responses to vaccinia virus proteins were observed with no toxicity. Specific T-cell responses were studied via stimulation of peripheral blood lymphocytes with specific peptide epitopes from the CEA molecule. These studies demonstrated clear cut differences in establishment of T-cell lines pre- versus post-immunization. The T-cell lines were shown to be CD8+ and/or CD4+/CD8+, to lyse EBV transformed B-cells transduced with the CEA gene, and to lyse CEA positive carcinoma cells in a HLA restricted manner. Thus, in a Phase I clinical trial the rV-CEA vaccine has been shown to stimulate a CTL response specific for CEA defined epitopes in cancer patients.

Serological and biochemical characterization of recombinant baculovirus carcinoembryonic antigen

Carcinoembryonic antigen (CEA), a glycosylated protein of M(r) 180 kDa, is one of the most widely used human tumor markers. A majority of gastrointestinal cancers as well as breast and nonsmall cell lung carcinomas express CEA. We have previously described a recombinant baculovirus BVCEA-140 expressing the full-length human CEA and a variant, BVCEA-16, that encodes only the NH2-terminal domain, as well as a recombinant (BVNCA) expressing the closely related molecule nonspecific cross-reactive antigen (NCA). We have now compared a panel of 24 anti-CEA and anti-NCA monoclonal antibodies (MAbs) for their ability to bind to these recombinant CEA and NCA proteins, as well as with a new 60 kDa subgenomic form designated BVCEA-60. The epitope mapping studies indicate that all the CEA specific MAbs can recognize BVCEA-140. We also compared the sugar composition of BVCEA-140 to native CEA, using a lectin-linked immunoradiometric assay. The results demonstrated that both the native and recombinant baculovirus CEA contain simple high-mannose carbohydrates as well as biantennary and biantennary hybrid complexes. However, native CEA also contains triantennary and tetraantennary complex sugars, while the recombinant CEA molecule does not. Immunogenicity of the recombinant CEA molecules was demonstrated in mice. ELISA and Western blot analyses were used to determine the cross-reactivity of the anti-CEA sera. Mice immunized with BVCEA-140 elicit antibodies that are reactive to native CEA. When the BVCEA-16 was used as an immunogen, the antisera failed to detect native CEA or BVCEA-140. These studies demonstrate that minor sugar differences exist between native and baculovirus-derived CEA. However, epitope mapping with a panel of 24 anti-CEA MAbs (recognizing at least 10 CEA epitopes) stowed virtual immunologic identity between these two molecules. Moreover, BVCEA-140 appears to be a more potent humoral immunogen in mice than native CEA. These purified recombinant proteins can thus serve as standards in CEA serum assays for the possible detection and characterization of cell-mediated immune responses to CEA and as a potential source of immunogen (primary or for boosting) for active specific immunotherapy protocols of human carcinomas.

Circulating immune complexes in HIV-infected persons

Circulating immune complexes are part of normal immune defense mechanisms and, therefore, present in various infectious--bacterial and viral--diseases. On the other hand, they are obviously involved in pathogenic mechanisms, e.g., autoimmune diseases or different forms of malignancies. Both autoimmune and infectious features are recorded in the acquired immunodeficiency syndrome. Thus, elevated levels of antigen-antibody complexes in HIV-infected persons had to be expected, and they were in fact demonstrated by several authors. In a cohort study, it was additionally shown that circulating immune complexes are of prognostic relevance. After an introduction concerning the physiological and pathophysiological role of circulating immune complexes in general, their involvement in the course of HIV infections is presented and discussed. In addition, there is a critical review of the most commonly applied assay systems for the detection and quantification of circulating immune complexes.