Alloantibodies, autoantibodies, and immune complexes in patients with lung cancer

Single-Molecule Interactions of a Monoclonal Anti-DNA Antibody with DNA

Interactions of DNA with proteins are essential for key biological processes and have both a fundamental and practical significance. In particular, DNA binding to anti-DNA antibodies is a pathogenic mechanism in autoimmune pathology, such as systemic lupus erythematosus. Here we measured at the single-molecule level binding and forced unbinding of surface-attached DNA and a monoclonal anti-DNA antibody MRL4 from a lupus erythematosus mouse. In optical trap-based force spectroscopy, a microscopic antibodycoated latex bead is trapped by a focused laser beam and repeatedly brought into contact with a DNA-coated surface. After careful discrimination of non-specific interactions, we showed that the DNA-antibody rupture force spectra had two regimes, reflecting formation of weaker (20-40 pN) and stronger (>40 pN) immune complexes that implies the existence of at least two bound states with different mechanical stability. The two-dimensional force-free off-rate for the DNA-antibody complexes was ~2.2 × 10^-3 s^-1, the transition state distance was ~0.94 nm, the apparent on-rate was ~5.26 s^-1, and the stiffness of the DNA-antibody complex was characterized by a spring constant of 0.0021 pN/nm, suggesting that the DNA-antibody complex is a relatively stable, but soft and deformable macromolecular structure. The stretching elasticity of the DNA molecules was characteristic of single-stranded DNA, suggesting preferential binding of the MRL4 antibody to one strand of DNA. Collectively, the results provide fundamental characteristics of formation and forced dissociation of DNA-antibody complexes that help to understand principles of DNA-protein interactions and shed light on the molecular basis of autoimmune diseases accompanied by formation of anti-DNA antibodies.

Autoantibodies in the serum of patients with gastric cancer: their prognostic importance

To evaluate the presence in serum and the clinical relevance of several antinuclear autoantibodies, we investigated 31 patients with initially diagnosed gastric cancer and 40 age-matched healthy controls. Autoantibodies against ssDNA, dsDNA, cardiolipin, actin, myosin, tropomyosin, GM1, GD1b and GT3 gangliosides, were detected with an enzyme-linked immunoassay (ELISA). Anti-ssDNA, anti-actin, anti-GM1 and anti-GD1b antibodies were detected in the serum of 11 (p = 0.001), 8 (p = 0.02), 11 (p = 0.001), and 9 (p = 0.008) patients with gastric cancer, respectively. There was no significant difference between patients with cancer and the control group, as far as the other autoantibodies were concerned. Most of the patients (90%) had autoantibodies against at least one of the antigens examined. Patients with anti-ssDNA, anti-actin, anti-GM1 and anti-GD1b antibodies were less likely to survive than the patients being negative to the above autoantibodies: the figures are 1 of 11 (9%) compared with 4 of 20 (20%); 1 of 8 (13%) compared with 5 of 23 (22%); 1 of 11 (9%) compared with 4 of 20 (20%); and 1 of 9 (11%) compared with 4 of 22 (18%), respectively. Our findings suggest that 4 of the 9 autoantibodies that we assayed are significantly more likely to be found in serum of patients with gastric cancer, indicating that the immune system has a role in the process of the malignant disease. If our results are confirmed by forthcoming studies, some of the immunological variables that we examined could be used as markers of prognostic value in patients with gastric cancer.

Lung cancer-induced blindness

Early investigations into the pathogenesis of vision loss in cancer patients noted the higher incidence with small cell carcinoma of the lung (SCCL), a neoplasia with suspected neuroendocrine origins [2-5,12,20,25,56,63,64]. The cause and effect relationship between the cancer and retinal deterioration was recognized, but the processes involved were not understood. Research eventually identified a sub-group of paraneoplastic retinopathy patients who exhibited indications of retinal hypersensitivity through their production of autoantibodies reactive with a single photoreceptor protein. The discovery of a small cell lung cancer culture actively expressing this same retinal autoantigen, provided tangible evidence to define a molecular basis for at least one type of paraneoplastic retinopathy. The identification of this immunologic anomaly illustrates how blindness can occur in some cancer patients, through the serendipitous initiation of ocular hypersensitivity, with vision loss developing as a cancer-induced autoimmune retinopathy.

The presence of anti-carcinoembryonic antigen (CEA) antibodies in the sera of patients with gastrointestinal malignancies

Using an enzyme-linked immunoassay we tested the sera of 71 patients with digestive system cancer, 35 patients with various nonmalignant disorders, and 28 normal individuals for anti-CEA activity. Antibodies were found in the sera of 51% of the patients. Most of the patients positive for the antibodies (70%) had no evidence of metastatic disease. Fewer than 10% of the sera from control groups had anti-CEA activity. The authors concluded that the patients suffering from cancer of the GI system are capable of producing tumor-specific antibodies. These antibodies could be used as a tumor marker and/or as a possible index for the function of the immune system. The presence of a large tumor mass could lead to the removal of these antibodies from the circulation.