Prognostic role of antibody reactivity to melanoma

New perspectives on the role of vitiligo in immune responses to melanoma

Melanoma-associated vitiligo is the best-studied example of the linkage between tumor immunity and autoimmunity. Although vitiligo is an independent positive prognostic factor for melanoma patients, the autoimmune destruction of melanocytes was long thought to be merely a side effect of robust anti-tumor immunity. However, new data reveal a key role for vitiligo in supporting T cell responses to melanoma. This research perspective reviews the history of melanoma-associated vitiligo in patients, the experimental studies that form the basis for understanding this relationship, and the unique characteristics of melanoma-specific CD8 T cells found in hosts with vitiligo. We also discuss the implications of our recent findings for the interpretation of patient responses, and the design of next-generation cancer immunotherapies.

Selective expression of inhibitory Fcgamma receptor by metastatic melanoma impairs tumor susceptibility to IgG-dependent cellular response

During melanoma progression, patients develop anti-tumor immunity including the production of anti-tumor antibodies. Although the strategies developed by malignant cells to escape anti-tumor cellular immunity have been extensively investigated, little is known about tumor resistance to humoral immunity. The main effect of IgG antibodies is to activate the immune response by binding to host Fc gamma receptors (FcgammaR) expressed by immune cells. We previously reported in a limited study that some human metastatic melanoma cells ectopically express the FcgammaRIIB1, an inhibitory isoform of FcgammaR. By analyzing a large panel of different types of human primary and metastatic solid tumors, we report herein that expression of FcgammaRIIB is restricted to melanoma and is acquired during tumor progression. We show that FcgammaRIIB expression prevents the lysis of human metastatic melanoma cells by NK cell-mediated antibody-dependent cellular cytotoxicity (ADCC) in vitro, independently of the intracytoplasmic region of FcgammaRIIB. Using experimental mouse models, we demonstrate that expression of FcgammaRIIB protects B16F0 melanoma tumors from the ADCC induced by monoclonal and polyclonal anti-tumor IgG in vivo. Thus, our results identify FcgammaRIIB as a marker of human metastatic melanoma that impairs the tumor susceptibility to FcgammaR-dependent innate effector responses.

Cross-reactivity between murine melanoma antigen B700 and a human melanoma-associated antigen (M-66) recognized by autologous antibody: evidence suggesting shared epitopes

We have previously reported the purification and partial characterization of a human melanoma-associated antigen (M-66) recognized by autologous antibody. This antigen was found to be an unusually acidic 66 kDa glycoprotein. In studies of murine melanoma, a 67-kDa albumin-like melanoma-associated antigen (MAA) isolated from B16 melanoma cells has also been reported by our laboratories. Because the murine MAA, B700, has a molecular weight that is nearly the same as M-66, we sought to determine what similarities and differences existed between these two antigens. Human sera S150, which is known to recognize M-66, was found to bind to murine melanoma cell line B16. The addition of purified M-66 inhibited binding of S150 to B16 cells. Binding by S150 was not noted against murine melanoma cell line S91, which is known not to express cell surface B700. Conversely, reactivity of S150 against Y-Mel 84:420, known to express M-66, could be inhibited by preincubation with B16 cells. Four monoclonal antibodies known to recognize B700 were evaluated for-binding against murine B16 and human melanoma cell line Y-Mel 84:420. Binding was noted against both B16 and Y-Mel 84:420 which could be inhibited by the addition of M-66. Binding of S150 was also noted against purified B700 as tested by ELISA. While a comparison of the amino acid composition of the two antigens revealed similarities, M-66 contained 2.8 times as much serine and 0.4 times as much proline as B700. B700 has been reported to be related to serum albumin, which is not the case for M-66.(ABSTRACT TRUNCATED AT 250 WORDS)

Serial studies of autologous antibody reactivity to squamous cell carcinoma of the head and neck

In previous studies we evaluated the incidence and specificity of autologous antibody reactivity against squamous cell carcinoma of the head and neck (SCCHN). We were able to demonstrate that autologous antibody reactivity is present in native sera but was usually of too low a titer to allow further analysis. Dissociation of immune complexes by acidification and ultrafiltration of serum augmented autologous antibody reactivity in nine out of nine autologous systems tested. Native antibody and antibody derived from immune complexes produced by the host and reactive with autologous tumor cells may be directed against physiologically relevant antigens. Therefore, correlations of antibody titers with clinical course may provide insight into the nature of the host response to cancer. In the present analysis, serological studies of six patients with SCCHN were performed with serum samples obtained over many months. Results of serial serological assays were correlated to tumor progression and clinical course. Fluctuations in autologous antibody reactivity were noted over time. In four cases, rises in autologous antibody titers preceded the clinical diagnosis of recurrence by several months. Drops in autologous antibody reactivity were noted in two cases following surgery or radiation therapy. In two cases of long-term survivors, no correlation between antibody reactivity and clinical course was noted. Specificity analysis of the six autologous systems demonstrated reactivity against autologous and allogeneic SCCHN as well as melanoma cell lines. These sera did not react with glioma, neuroblastoma, renal cell, breast, bladder and colon carcinoma cell lines nor with fetal calf serum, pooled lymphocytes, red blood cells and platelets. Autologous serial serological studies may provide a means by which to evaluate the host/tumor relationship in patients with SCCHN.

Purification and partial characterization of a shed 66 kDa melanoma-associated antigen identified by autologous antibody

We have previously reported the isolation of a 66 kDa melanoma-associated antigen, identified by autologous antibody, in serum and unfractionated spent tissue culture media by Western blot analysis. The antigen, detected by autologous serum S150, was found to be broadly represented on melanoma, glioma, renal cell carcinoma, neuroblastoma and head and neck carcinoma cell lines. S150 did not react with bladder or colon carcinoma, fetal fibroblasts, pooled platelets, lymphocytes and red blood cells, autologous cultured lymphocytes or fetal calf serum. To further characterize the antigen, spent tissue culture media, obtained from autologous melanoma cell line, Y-Mel 84:420, was separated by an isoelectric focusing column. Unabsorbed control serum S150 was noted to have a maximum titer of 1:2040 against autologous melanoma cells as measured by protein A hemadsorption. Following isoelectric focusing the greatest decrease in autologous antibody titer (30-fold) occurred with fractions having a pI between 2 and 3. Further resolution of the antigen was accomplished with high-pressure ion-exchange chromatography. One of these fractions showed a significantly higher concentration of antigen and was distinctly resolved from bulk serum albumin. Subsequent Western blot analysis, with autologous antibody, of the isolated antigen-containing fraction, confirmed the presence of a single 66 kDa band. Exposure of the antigen, purified by high-pressure ion-exchange chromatography, to neuraminidase ablated recognition by autologous antibody and suggests that sialic acid is present on the protein and may be part of the antigenic epitope. Binding of antigen, obtained following DEAE anion exchange chromatography, was noted to lectins derived from Triticum vulgaris, Dolichos biflorus and Lycopersicon esculentum. Preparative purification of the antigen was accomplished by anion exchange followed by lectin affinity chromatography with a Dolichos biflorus column. Antigen obtained following lectin affinity chromatography subjected to SDS-PAGE and silver stain revealed a single band at 66 kDa. We conclude that a melanoma-associated antigen detected by autologous antibody in spent tissue culture media is an unusually acidic glycoprotein (pI 2-3).

The use of biomarkers in the prediction of survival in patients with pulmonary carcinoma

Data on ten variables and 16 biomarkers were obtained on 119 patients with newly diagnosed pulmonary cancer. The prognostic value of 16 biomarkers (alpha-1-antitrypsin [AAT], adrenocorticotropic hormone [ACTH], alpha-fetoprotein [AFP], carcinoembryonic antigen [CEA], human chorionic gonadotropin [HCG], immune complexes, immunoglobulins, N-terminal peptide of proopiomelanocortin [NTERM], and tumor-associated antibody [TAA]) was tested by adding these to the model of age, gender, stage, morphology, Feinstein's classification of symptoms, Karnofsky scale, leukocyte count, recent weight loss, and liver enzymes. Using Cox's regression method and a forward stepwise procedure, seven biomarkers (ACTH, AAT, AFP, calcitonin, HCG, TAA, and prolactin) entered the model. Elevated levels of cortisol and TAA were associated with longer survival. The selection of biomarkers by stepwise regression needs to be interpreted with caution, especially since the Z scores were found to be dependent on the particular variables included in the model. Furthermore, when dichotomized on maximum of the normal laboratory values, HCG and AFP were infrequently (2%) elevated. The lack of correlation among the biomarkers supports the hypothesis of random derepression of the genome of cancer cells. Further studies in improved modeling and the formulation of a biomarker index could enhance our understanding of the biology of cancer.

Detection and isolation of antigen-specific immune complexes from sera of melanoma patients

Detection of antigen-specific circulating immune complexes (IC) in sera from cancer patients provides an approach for defining tumor antigens that induce a host immune response and could prove useful for purposes of immunoprognosis. In the present study, a sandwich ELISA was developed to detect antigen-specific IC in cancer patients, utilizing a murine monoclonal antibody designated MAb JSI. The MAb was produced by cell fusion using standard hybridoma technology following immunization with a partially purified fetal antigen that had been isolated from the spent culture medium of a melanoma cell line. The partially purified antigen appeared to be broadly expressed on melanomas, sarcomas, and carcinomas. The MAb was mass-produced in pristine-primed mice. MAb JSI reacted with the cultured melanoma cell M14 but not the autologous lymphoblastoid cell L14. Following purification by ammonium sulfate precipitation, the MAb was immobilized on polystyrene plates and utilized to capture antigen-specific immune complexes from sera of melanoma patients which were detected with anti-human globulins. The second antibody in the sandwich was shown to be endogenous human IgG. Antigen-specific immune complexes were present in melanoma patients but only infrequently in sera from normal individuals and patients with active autoimmune disease. Antigen-specific immune complexes detected in melanoma sera were isolated by affinity chromatography utilizing the MAb JSI. The assay described in this report is simple and reproducible, without plate effect (p = 0.97) or time effect (p = 0.34) and could provide a useful new approach to examine the role of antigen-specific circulating immune complex analysis in cancer patients.

Human IgG and IgM monoclonal antibodies against autologous melanoma produced by Epstein-Barr-virus-transformed B lymphocytes

The serum antibody response to human melanoma has prognostic and potential physiological consequences. The specificity of the host B cell antibody response may be an important determinant of disease outcome. We have utilized Epstein-Barr virus (EBV) transformation to analyze the repertory of the host B cell response to melanoma. Production of antibody that binds selectively to autologous (eight cases) or allogeneic (four cases) short-term-cultured melanoma cells was assessed from EBV-transformed B lymphoblastoid cells. Forty-two cultures of EBV-transformed B cells that secreted IgM and 23 that secreted IgG antibodies gave patterns of differential reactivity with autologous or allogeneic melanoma. Antibody-forming B cells persisted in producing melanoma-reactive IgG and IgM for 8-21 weeks. Preselection of B cells by adsorption to tumor cell antigens before transformation enhanced the frequency of antibody secretion. The specificity of the antibody produced by the longest-producing culture appears to be restricted to a subset of melanomas. The patient from whom this tumor-restricted IgG-producing B cell was retrieved was unusual, having had a transient serum IgG of similar specificity, and having manifest a syndrome of vitiligo at the time of her development of serum antimelanoma antibody, followed by disease-free survival of resected recurrent metastatic melanoma to the present (more than 6 years). This study has given support to findings of conventional serology, revealing the production of melanoma-reactive antibody from B cells of patients who have demonstrable serological response to tumor.

Isolation and partial characterization of melanoma-associated antigens identified by autologous antibody

The study of the autologous immune response to cancer avoids the difficulties encountered in the use of xenoantisera and may identify antigens of physiological relevance. However, the low titer and incidence of autologous antibody to melanoma have hampered further evaluation. By utilizing acid dissociation and ultrafiltration of serum, we have been able to augment the detectable autologous immune response to melanoma in the majority of patients studied. In autologous system Y-Mel 84:420, serum S150 demonstrated a rise in titer from 1:32 in native sera to 1:262,044 after dissociation. The antigen detected by S150 was found to be broadly represented on melanoma, glioma, renal cell carcinoma, neuroblastoma, and head and neck carcinoma cell lines. It did not react with bladder or colon carcinoma, fetal fibroblasts, pooled platelets, lymphocytes and red blood cells, or autologous cultured lymphocytes. Using polyacrylamide gel electrophoresis, S150 detects a 66,000-mol wt antigen in spent tissue culture media and serum ultrafiltrate. In cell lysate two bands between 20,000 and 30,000 mol wt are detected by S150. The 66,000-mol wt antigen is sensitive to trypsin digestion and but is resistant to pepsin and heat inactivation. Exposure of spent media to trypsin results in the development of a 24,000-mol wt band that appears to correspond to the antigen detected in the cell lysate. The difference between the antigens detected in the cell lysate as compared with spent media and serum ultrafiltrate may be due to degradation during cell lysis. We conclude that melanoma-associated antigens are present in the serum of patients with melanoma and are shed or secreted by their tumor cells.