Abstract. In cancer, the retinal Ca 2+ -binding protein recoverin is a paraneoplastic antigen, the aberrant expression of which is capable of triggering the appearance of specific autoantibodies in the serum of patients with malignant tumors and the subsequent development of a paraneoplastic syndrome, cancer-associated retinopathy (CAR). The frequency of serum autoantibodies against recoverin (AAR), earlier determined at a rate of 15-20% in lung cancer, is much higher than the frequency of CAR syndrome, which is approximately 1%. In the present study, we estimated for the first time the frequencies of serum AAR in patients with various types of malignancies other than lung cancer. Patient biospecimens were collected to analyze for the presence of AAR. Additionally, various cell lines were cultivated and analyses were performed using Western blotting and RT-PCR. Results showed that in all cases tested, the AAR frequencies did not exceed 10%. Five AAR-positive patients with various types of cancer were available for ophthalmological investigation and only one of these patients had CAR syndrome. This result is consistent with the conclusion made in our previous studies of lung cancer that serum AAR do not necessarily trigger the development of CAR syndrome. IntroductionNeuronal proteins, which are usually present only within the nervous system but may also be expressed in malignant tumors localized outside the nervous system, are assigned to paraneoplastic (onconeural) antigens (PNA). The immune system of certain patients responds to PNA by producing specific autoantibodies and/or cytotoxic T-cells that trigger the development of a paraneoplastic neurological syndrome (PNS) (1). One such PNA is the photoreceptor Ca 2+ -binding protein recoverin (2,3), which is normally specific to the retina and the pineal gland but may also be aberrantly expressed in malignant tumors of the lung and other tissues (4,5). In certain patients with lung cancer, high-titer serum autoantibodies against recoverin (AAR) trigger the development of a PNS, cancer-associated retinopathy (CAR) (6,7). However, low-titer serum AAR of patients with lung cancer do not necessarily cause CAR syndrome (8-10). Instead, this syndrome only occurs in approximately 1% of cancer patients, whereas the frequencies of serum AAR in patients with small cell lung carcinoma (SCLC) and non-small cell lung carcinoma (NSCLC) equal 15 and 20%, respectively (10).By analogy with cancer-testis antigens, recoverin has been classified as a cancer-retina antigen (5) for the following reasons: i) its normal expression is restricted to an immunoprivileged tissue (retina), ii) it is aberrantly expressed in tumor cells, iii) it subsequently demonstrates high antigenicity (autoantibodies and/or T-cells), and iv) aberrant demethylation of the gene promoter is involved in the aberrant expression of recoverin (11).In this study, we analyzed serial specimens of blood sera of patients with a number of different malignancies to estimate the frequency of serum AAR in oncological disea...
The objective of the present study was to reveal antitumour antibodies in sera of patients with small cell lung cancer (SCLC).The antibodies in sera of patients with SCLC and other tumours were detected by immunoblotting with whole extracts of SCLC cells as the antigen source. Sera of patients with various pulmonological disorders, irradiated during the liquidation of consequences of the Chernobyl nuclear power plant incident (a high-risk group in lung cancer), were also analysed.The present authors9 found that SCLC sera contain a set (pattern) of antitumour antibodies which are rarely detected in sera of patients with cancers different from SCLC and very rarely, if ever, present in sera of healthy individuals. The sensitivity and the specificity of the pattern are equal to 80% and 91%, correspondingly. In the highrisk group in lung cancer, the frequencies of the antibodies are somewhat lower than the corresponding values in SCLC sera, but significantly larger than those in healthy sera.The findings of the present study create a basis for clinical application of the antitumour antibodies described.
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