[Mutagenic Activity of AID/APOBEC Deaminases in Antiviral Defense and Carcinogenesis]

Proteins of the AID/APOBEC family are capable of cytidine deamination in nucleic acids forming uracil. These enzymes are involved in mRNA editing, protection against viruses, the introduction of point mutations into DNA during somatic hypermutation, and antibody isotype switching. Since these deaminases, especially AID, are potent mutagens, their expression, activity, and specificity are regulated by several intra-cellular mechanisms. In this review, we discuss the mechanisms of impaired expression and activation of AID/APOBEC proteins in human tumors and their role in carcinogenesis and tumor progression. Also, the diagnostic and potential therapeutic value of increased expression of AID/APOBEC in different types of tumors is analyzed. We assume that in the case of solid tumors, increased expression of endogenous deaminases can serve as a marker of response to immunotherapy since multiple point mutations in host DNA could lead to amino acid substitutions in tumor proteins and thereby increase the frequency of neoepitopes.

[Body's Own Epitopes among Foreign Ones: T Cells and Autoantigens]

T cells play a key role in adaptive immunity reactions, recognizing antigens using variable TCRs. Functional TCR subunit genes are formed by somatic rearrangement, and some of the resulting TCRs recognize autoantigens, the body's own molecules. The autoreactive T cells that carry such TCRs pose a threat of inducing immune reactions against their own organism. In the course of the immune system's development, some autoreactive T lymphocytes are eliminated by apoptosis, some differentiate into immunosuppressive regulatory T cells, which support immunological tolerance to autoantigens, and the rest fall into a non-functional state of anergy. Suppression of effector T cells by regulatory T cells is mediated by immunosuppressive cytokines and costimulatory molecules, depletion of stimulating IL-2, removal of autoreactive peptides together with MHC molecules, and in other ways. Impairment of self-tolerance leads to autoimmune diseases. However, the loss of immunological tolerance can be employed in tumor treatment, allowing immunotherapy and the use of the potential of autoreactive effector T cells. The fact that the efficacious immunotherapy of tumors is often accompanied by adverse autoimmune reactions currently seems to be the inevitable price paid by using this approach.

[Splicing Pattern of mRNA in Thymus Epithelial Cells Limitsthe Transcriptome Available for Negative Selection of Autoreactive T Cells]

Successful negative selection of autoreactive T cells requires expression of maximum amount of epitopes representing all possible protein isoforms in the thymus. Absence of some possible protein spliceforms in the thymus due to realization of some, but not all splicing combination, may limit the negative selection. Here we show that about 25% of studied mouse genes with well-described alternative splicing event encode some epitopes hidden from thymus. For five out of 10 randomly selected genes with predicted "hidden" epitopes, namely, Add2, Dst, Golga7, Lmna, Nasp, these findings were confirmed experimentally. Thus, for approximately 10-15% of alternatively expressed genes, their splicing patterns in Thymus may limit the set of epitopes available for negative selection.

[Evolutionary plasticity of IL-6 cytokine family]

The IL-6 family of cytokines includes a variety of proteins that function not only within the immune system, but also in other organs, tissues, and types of cells, including neurons. The common evolutionary origin of the IL-6 family proteins determines similar mechanisms of reception and intracellular signaling, although their primary structures are highly variable, as well as their biological functions. We have demonstrated that the members of the IL-6 family have high evolutionary plasticity. This manifests in a high degree of population polymorphism for IL-6 family genes, as well as varying degrees of evolutionary conservation among members of the family. The degree of evolutionary conservation of IL-6 family proteins does not correlate with the mechanisms of interaction between these cytokines and their receptors.

Possible Mechanisms of Acquisition of Herpesvirus Virokines

The genomes of certain types of human and primate herpesviruses contain functional homologs of important host cytokines (IL-6, IL-17, and IL-10), or so-called virokines. Virokines can interact with immune cell receptors, transmit a signal to them, and thus switch the type of immune response that facilitates viral infection development. In this work, we have summarized possible ways of virokine origin and proposed an evolutionary scenario of virokine acquisition with involvement of retroviral coinfection of the host. This scenario is probably valid for vIL-6 of HHV-8 and MRV-5 viruses, vIL-17 of HVS virus, and vIL-10 of HHV-4, Bonobo-HV, RhLCV, and BaLCV viruses. The ability to acquire cytokine genes allows herpesviruses to implement unique strategies of avoiding the immune response and provides them an evolutionary advantage: more than 90% of the host population can be chronically infected with different herpesviruses. It is possible that the biological success of herpesviruses can be partially due to their cooperation with another group of viruses. This hypothesis emphasizes the importance of studies on the reciprocal influence of pathogens on their coinfection, as well as their impact on the host organism.

[Genetic mechanisms of adaptive immunity emergence in vertebrates]

The adaptive immune system in vertebrates emerged in a multistep process that can be reconstructed on the basis of the data concerning the structure of immune systems of modern cartilaginous and bony fishes, as well as of cyclostomes. The most probable evolutionary scenario is likely to be as follows: the T cell receptor loci emerged on the basis of NK cell-like receptor genes; the antibody loci evolved on the basis of T cell receptor loci; the MHC locus arose on the basis of the locus responsible for innate immunity of early chordates. The ancestral MHC molecules likely participated in the transplantation immunity before they acquired the ability of antigen peptide presentation.

Serum Immunoproteomics Combined With Pathological Reassessment of Surgical Specimens Identifies TCP-1ζ Autoantibody as a Potential Biomarker in Thyroid Neoplasia

CONTEXT

Current methods of preoperative diagnostics frequently fail to discriminate between benign and malignant thyroid neoplasms. In encapsulated follicular-patterned tumors (EnFPT), this discrimination is challenging even using histopathological analysis. Autoantibody response against tumor-associated antigens is a well-documented phenomenon with prominent diagnostic potential; however, autoantigenicity of thyroid tumors remains poorly explored.

OBJECTIVES

Objectives were exploration of tumor-associated antigen repertoire of thyroid tumors and identification of candidate autoantibody biomarkers capable of discrimination between benign and malignant thyroid neoplasms.

DESIGN, SETTING, AND PATIENTS

Proteins isolated from FTC-133 cells were subjected to two-dimensional Western blotting using pooled serum samples of patients originally diagnosed with either papillary thyroid carcinoma (PTC) or EnFPT represented by apparently benign follicular thyroid adenomas, as well as healthy individuals. Immunoreactive proteins were identified using liquid chromatography-tandem mass-spectrometry. Pathological reassessment of EnFPT was performed applying nonconservative criteria for capsular invasion and significance of focal PTC nuclear changes (PTC-NCs). Recombinant T-complex protein 1 subunitζ (TCP-1ζ) was used to examine an expanded serum sample set of patients with various thyroid neoplasms (n = 89) for TCP-1ζ autoantibodies. All patients were included in tertiary referral centers.

RESULTS

A protein demonstrating a distinct pattern of EnFPT-specific seroreactivity was identified as TCP-1ζ protein. A subsequent search for clinicopathological correlates of TCP-1ζ seroreactivity revealed nonclassical capsular invasion or focal PTC-NC in all TCP-1ζ antibody-positive cases. Further studies in an expanded sample set confirmed the specificity of TCP-1ζ autoantibodies to malignant EnFPT.

CONCLUSIONS

We identified TCP-1ζ autoantibodies as a potential biomarker for presurgical discrimination between benign and malignant encapsulated follicular-patterned thyroid tumors. Our results suggest the use of nonconservative morphological criteria for diagnosis of malignant EnFPT in biomarker identification studies and provide a peculiar example of uncovering the diagnostic potential of a candidate biomarker using incorporation of pathological reassessment in the pipeline of immunoproteomic research.

[Hyperplastic skin growth on the head of goldfish--comparative oncology aspects]

Dynamics of development and morphology of hyperplastic skin lesions ("hoods") on the head of goldfish, which were bred using artificial selection for more than thousand years, were studied. During monitoring of hundred fishes, at the age of 6 months "hoods" were found in 39.5%, among 14 months-old fishes in 60,7%. Morphologic examination of "hoods" on various stages of development revealed epithelial hyperplasia with increased clear mucous cells number, dermis thickening and oedema. On later stages developed papillomatous outgrowth and areas of epithelial intrusion. The comparative oncology analysis allow to hypothesize these skin growth to be a genetically determined benign neoplasm. This is the first example of artificially selected neoplasm described in the literature. It supports our hypothesis of the possible evolutionary role of tumors.

Cytochrome c: the Achilles' heel in apoptosis

Cytochrome c is a well-known mitochondrial protein that fulfills life-supporting functions by transferring electrons to the respiratory chain to maintain ATP production. However, during the activation of apoptotic machinery, it is released from mitochondria and, being in the cytosol, it either triggers the activation of the caspase cascade in intrinsic apoptotic pathway, or it is involved in the amplification of extrinsic apoptotic signaling. Accumulating evidence suggests that only unmodified holocytochrome c is efficient in the stimulation of apoptosis. Considering the importance of cytochrome c in both life and death, it was of significant interest to investigate the complete or partial cytochrome c deficiency in vivo. Here, we discuss the importance of distinct amino acid residues for various functions of cytochrome c in cells and mice with targeted cytochrome c mutations.

[Tumor-specific expression of PBOV1, a new gene in evolution]

We identified mRNA of the newly discovered gene PBOV1 in a multitude of samples from tumors of the brain, lung, liver, gallbladder, colon, small intestine, mammary gland, uterus, ovary, ureter, adrenals, parotid, thymus and spleen. However, out of 29 intact adult and 8 fetal tissues, only pancreas was characterized by weak expression of the gene. Our results demonstrated that the PBOV1 gene expression is tumor-specific and has a potential as tumor marker. It is worth mentioning that we had predicted that property on the basis of available evolutionary data.