The dynamic relationships between tumor cells and their microenvironment are of crucial importance in the development and progression of the malignant process. Given the multifunctional potential of heterogeneous populations surrounding a tumor, targeting components of the microenvironment has long been regarded as a promising strategy in modern anticancer therapy. This review discusses the role of the components of the cellular microenvironment in carcinogenesis, analyzes in detail the main ways and mechanisms of action on the main cell populations, which are of the greatest interest in the context of the development of innovative anticancer therapy.

It has been proven that 98 % of the human genome is transcribed. The main part of resulting molecules after their processing function as various RNA molecules, among which the best known are long noncoding RNA (lncRNA)  and microRNA. There are 126,000 lncRNA genes in humans that regulate transcription, translation, histone modifications, heterochromatin formation, splicing, microRNA expression and formation, and matrix RNA (mRNA)  post-transcriptional modifications. An important property of lncRNAs is their mutual and self-regulation by peptides formed during their translation, which also affect the expression of protein-coding genes. This property may be due to origin of lncRNAs from transposable elements and is a conservative evolutionary characteristic of lncRNA, as one of properties in formation of new genes for variability and adaptation.  The role of lncRNAs originating from retroelements and microRNAs formed during their processing in the specific regulation of genes involved in carcinogenesis has been proven. The peptides formed during lncRNA translation can be used as universal tools for targeted therapy of malignant neoplasms. Analysis of the scientific literature  made it possible to describe 21 lncRNAs that  are translated  to form peptides involved in specific tumors pathogenesis. Since the ability of lncRNA to self-regulate by products of its own translation, which is characteristic of all lncRNAs, is also a property of transposable elements, it is promising to study transposons and their relationship with lncRNAs for designing new therapeutic models.

In normal tissue, cellular homeostasis is largely driven by two catabolic pathways: apoptosis and autophagy. Apoptosis, or programmed cell death, is regulated by pro-apoptotic factors, and promotes the removal of problematic cells. Autophagy, which in turn includes three forms: macro-, micro-, and chaperone-mediated autophagy, can promote both cell survival by selectively removing potentially apoptosis-inducing factors and raising the threshold of stress required for the induction of cell death. Recently, evidence has been accumulating suggesting the existence of common molecular pathways between autophagy and apoptosis, as well as the influence of the extracellular matrix on these processes. One of the important enzymes involved in the coordination and regulation of these processes is transglutaminase 2 (TG2). Different types of TG2 activities are involved in maintaining the dynamic balance between extracellular matrix and intracellular autophagy/apoptosis processes, while dysregulation of these processes may contribute to the pathogenesis of various human diseases, including oncogenesis. For example, TG2 can promote the degradation of pro-apoptotic proteins and the survival of renal cell carcinoma cells under nutrient-deficient conditions by modulating the autophagy process. In cells of various tissues deprived of TG2, aggregates of ubiquitinated proteins and damaged mitochondria are observed, which in turn induces proteotoxic stress and cell death. conversely, the transamidase activity of TG2 was observed to inhibit anti-apoptotic  signaling in a human leukemic monocytic lymphoma model. In the present review, a number of important functions of TG2 in oncogenesis are described, along with the dual role of TG2 in modulating such opposite processes as cell survival and cell death.

Growth factors signaling cascades and their interaction with the central regulatory targets of tumor cells and estrogens are considered as the main mechanisms of hormonal resistance in breast cancer. The integration  of the transforming growth factor β1 (TGF-β1) and PI3K (phosphoinositide 3-kinase)/Akt (protein kinase B)/mTOR (mammalian target of rapamycin) signaling pathway may result in the activation of proliferation and, as a result, the development of an in-effective response to therapy and disease progression. The review summarizes a systematic analysis of the literature data on the role of TGF-β1 signaling in the mechanisms of tamoxifen resistance to in the aspect of interaction  with the PI3K/Akt/mTOR. The interaction between the estrogen receptors α signaling and tamoxifen, the mechanisms of regulatory activation of TGF-β1 and PI3K/Akt/mTOR, as well as their contribution to the tamoxifen response are considered. The direct involvement of TGF-β1/PI3K in the mechanisms of tamoxifen resistance to determines the prospects for studying the effector of these cascades as molecular targets. The knowledge accumulated to date allows considering the TGF-β1/PI3K signaling pathway as a potential molecular tool for the search for effective strategies for blocking the resistance of tumor cells to tamoxifen.

Gastrointestinal stromal tumors (GIST) are the most common mesenchymal tumors of the gastrointestinal tract. Their main features are the expression of CD117 (KIT) and mutations of KIT or PDGFRA in 85 % of patients. however, 10–15 % of adult GIST and 85 % of pediatric GIST do not have KIT/PDGFRA mutations (KIT/PDGFRA WT GIST or “wild-type” GIST). The prognosis and clinical course of these tumors and GIST with KIT/PDGFRA mutations differ. “Wild-type” GIST are quite heterogeneous group of tumors in terms of clinical phenotype, genetic etiology, and molecular pathways. Gastrointestinal stromal tumors are divided into SDH-deficient and SDH-competent based on the succinate dehydrogenase (SDH) complex. SDH-deficient GIST occur predominantly in children and young patients  with Carney–Stratakis syndrome and Carney triad; there are also sporadic tumors. More than half of SDH-deficient GIST contain mutations in SDHA, SDHB, SDHD or SDHC, while the rest are caused by hypermethylation of the SDHC promoter. SDH-competent “wild-type” GIST include tumors with BRAF, RAS, or NF1 mutations that activate the RAS-RAF-MAPK pathway and KIT/PDGFRA/SDH/RAS-P WT GIST subtype or “quadruple wild type” GIST. The genomic profiles of these tumors and GIST with KIT/PDGFRA mutation or SDH deficiency differ significantly. One of the features of “quadruple wild type” GIST is activation of the FGFR (fibroblast growth factor receptors) signaling pathway due to chimeric FGFR, FGFR mutations, or overexpression of FGF (fibroblast growth factor). Another feature is chimeric genes containing fragments of NTRK, BRAF, FGFR and other genes that behave as oncogene drivers. In “quadruple wild-type” GIST the somatic mutations in TP53, MAX, MEN1, CTNND2, CHD4, ARIDIA and other genes were revealed as well as in the cell cycle genes RB1, CDK4, CDKN1B. There is no specific treatment for patients with “wild-type” GIST; the choice of drug is determined by the genetic disorder. There is a need to improve our understanding of the molecular mechanisms underlying the different GIST subtypes to develop more effective therapeutic approaches.

Cytokeratins (CKs) are well studied as intermediate filaments of the cytoskeleton of epithelial cells, providing specific cell structure and morphology, in particular, apico-basal cell polarization. Meanwhile, a certain specificity of the association of CK with different types of epithelia is noted. CK heterogeneity  in the glandular epithelium is particularly pronounced and is associated with anatomical localization. The relative specificity of CKs in epithelium of different localization is preserved to a great extent in carcinomas originating from this epithelium as well. Due to this fact the determination of CK spectrum in tumor cells is quite an effective tool for nosological diagnostics of carcinomas. however, the function of CKs is not limited to providing the cell structure. The presence and amount of CK changes during the most important processes in normal and tumor cells: movement/invasion, apoptosis, proliferation, epithelial-mesenchymal plasticity.

A question arises: Is initiation of the above-listed processes happens first, and therefore CK changes are secondary and «passive», or in some processes CK changes can play a role of a trigger? Knowing the answer to this question is not only of fundamental importance, but is also important for finding ways to control the above processes by influencing the CKs.

Cardiotoxicity of anticancer therapy is a severe adverse cardiovascular event affecting the survival of cancer patients. Modern methods for diagnosing cardiotoxicity allow to identify already occurred myocardial transformations, accompanied by symptoms of heart failure and are not predict and detect early changes in the heart tissue during treatment. Recently, increasing attention is paid to the search for molecular genetic markers, a single identification of which before starting treatment will make possible to determining the risks of cardiotoxicity and change treatment taking into account individual genetic characteristics. At the same time, most research on the effect of allelic variants of genes on cardio-vascular complications relate to chemotherapy of solid tumors. The review considered possible prognostic genetic variants of cardiotoxicity induced by chemotherapy in patients with the hematopoietic and lymphatic malignancies.

Introduction. The absence of specific clinical symptoms in the early stages of colorectal cancer development leads to the fact that a quarter of patients who seek help for the first time have a metastatic stage of the disease. For the timely detection of pre-tumor disorders or hidden foci of malignancy, the possibilities of modern molecular biological technologies are being actively studied today.

Aim. To develop a method for diagnosing tumor diseases of the colon based on molecular genetic analysis of morphologically unchanged intestinal epithelium distant from the focus of the tumor lesion.

Materials and methods. We examined the matrix RNA (mRNA)  expression profile of 63 candidate genes potentially associated with the pathogenesis of neoplastic changes in rectal mucosal samples. Samples were obtained during prophylactic and/or diagnostic video colonoscopy of 122 patients, 41 of whom had no history of breast cancer (“Normal”), 32 patients were diagnosed with breast cancer polyps (“Polyposis”) and 49 patients were diagnosed with breast cancer (“colorectal cancer”). mRNA expression was assessed by reverse transcription polymerase chain reaction.

Results. Using the discriminant analysis method, it was established that  the cellular material of scrapings from the rectum in the “colorectal cancer” group reliably, with a classification accuracy above 96 %, differs in expression phenotype from the “Normal” and “Polyposis” groups.

Conclusion. The data obtained are a prerequisite for the development of a minimally invasive diagnostic method that can be used as part of an outpatient  examination to assess the risk of colon tumor disease.

Introduction. The study of the effect of irradiation or any other DNA-damaging agents on the sensitivity of tumors to conservative therapy, drug or hormonal, is among the most imporant tasks that determine the efficiency of combined therapy of cancer patients.

Aim. To investigate the effect of irradiation on the activity of key signaling proteins and the level of hormone dependence of breast cancer cells.

Materials and methods. The experiments were performed on in vitro cultured estrogen-dependent MCF-7 breast cancer cells. Ultraviolet (UV) irradiation in the range of 254 nm with the intensity of 25–50 J/m²  was used as an experimental model to study the response of tumor cells to DNA damage. Cell growth rate was determined using the MTT test, cell survival after irradiation was analyzed using the colony-forming test.  Estrogen receptor transcriptional  activity was determined by reporter assay; cellular protein expression was determined by immunoblotting.

Results. Single UV irradiation of MCF-7 cells leads to a marked increase in the level of apoptotic markers: p53, cPARP, suppression of expression of growth signaling proteins: CDK4/6 and estrogen receptor α (ERα). The above changes are accompanied with an increase in phosphorylation of Akt protein kinase and a marked increase in the expression of Snail1, one of the key proteins of epithelial-mesenchymal transition. In UV-resistant MCF-7/UVR cell subline obtained under repeated irradiation cycles, the levels of apoptotic and growth signaling proteins (p53, cPARP, CDK4/6) return to control levels, except for the phosphorylated form of Akt and Snail1, whose content  remains high. Transfection of Snail1-expressing plasmid into MCF-7 cells is accompanied by activation of apoptotic signaling, suppression of ERα activity, and development of partial hormone resistance; however, the sensitivity of cells to irradiation is practically unchanged. Transfection of microRNA-181a-2, one of the microRNAs associated with cell resistance, simultaneously activates Akt and Snail1 and leads to the development of cross-resistance of cells to irradiation and hormonal drugs.

Conclusion. The obtained data allow us to consider irradiation-induced Snail1 activation as one of the factors involved in deregulation of estrogen signaling and formation of cell resistance to hormonal drugs, while simultaneous activation of Akt and Snail1 is accompanied by the development of cross-resistance to irradiation and hormonal drugs.

Rationale. The discovery of two Epstein–Barr virus (EBV) types, EBV-1 and EBV-2, which differ in their transforming abilities stimulated their study in various populations in order to elucidate the relationship with malignant neoplasms.

Aim. To study EBV-1 and EBV-2 in representatives of four ethnic groups of Russia, sequence analysis of the LMP1 oncogene in virus isolates, and search for a correlation between the types of EBV and the incidence of certain types of malignant tumors in four ethnic groups.

Materials and methods. From total DNA obtained from oral washings of Adygeans, Kalmyks, Tatars and Slavs, representatives of 3 Russian republics and the Moscow region, EBV DNA was amplified; its presence and concentration were analyzed by nested PCR, and each product was examined for the virus type and LMP1 variant. Types of EBV found in representatives of In four ethnic  groups were compared with the incidence rates of malignant tumors, among which EBV-associated cases may occur, in population of three republics and the Moscow region.

Results. It was observed that  higher gastric cancer and lymphomas morbidity among Tatarstan and Moscow region populations (compared to populations of Adygea and Kalmykia) correlated with predominance in these ethnic groups – Tatars and Slavs – EBV-1 type having transforming potential in vitro. In Adygeis, non-transforming EBV-2 type was prevalent, and Kalmyks were infected with both types in approximately equal proportion. however, differences between tumor morbidities between the compared groups were statistically insignificant (p >0.05). The identified spectrum of LMP1 variants, as well as the results of their sequencing, show genetic relations between EBV strains circulating in the studied ethnic groups.

Conclusion. Study of EBV isolates for the first time performed in 4 ethnic groups of this country showed differences in distribution of the types of this virus but there was no correlation with tumor morbidity.

Introduction. Current approaches are being developed for adoptive cancer therapy using T-cells genetically modified with T-cell receptors (TCRs) with specificity for tumor antigens. The complexities of identifying antigen-specific TCRs in a patient’s repertoire and selecting therapeutic  receptors necessitate the development of experimental strategies for generating tumor-specific T cells. One of such approaches could be the xenogeneic immunization of mice with human tumor cells. It seems plausible that the T cell repertoire stimulated by xenogeneic vaccination could be a source of TCRs suitable for adoptive cancer immunotherapy.

Aim. To assess the prospects for using xenogeneic immunizations to generate tumor-specific memory T cells and identify their TCRs suitable for adoptive immunotherapy, we studied the dynamics of the secondary xenogeneic response in a model of induction of an immune response in mice to human melanoma cells.

Materials and methods. Mice were immunized with human melanoma cells, and 45 days later, they were re-challenged with the immunizing tumor. The dynamics of the development of the secondary immune response in vivo and the composition of the involved effectors of adaptive immunity were analyzed by flow cytometry. The proliferation of lymphocytes from immune mice in response to human melanoma cells was evaluated in in vitro culture.

Results. The secondary xenogeneic response was characterized by a more intense accumulation of T cells and the rapid development of the effector phase at the injection site of human melanoma. This correlated with an enhanced in vitro proliferative response of lymphocytes from immune animals to xenoantigens of the immunizing tumor. CD4⁺ and CD8⁺ memory  T cells contributed equally to the development of a secondary response to human melanoma cells expressing HLA class I and II molecules. When only HLA class I was expressed on the cells of the immunizing xenogeneic tumor, CD8⁺ memory cells were formed, which dominated the secondary immune response.

Conclusion. Our findings confirmed the formation of a specific immunological memory for xenoantigens during xenogeneic immunization. This suggests the possibility of generating xenogeneic TCRs specific for human tumor antigens, which opens up opportunities to developing approaches for screening among them for receptor variants suited for adoptive immunotherapy of human cancers.

Introduction. There is currently no effective therapy for the treatment of glioblastoma. This is partly explained by the high degree of intra- and intertumor heterogeneity of GB, the source of which is believed to be glioblastoma stem cells (GSC). The question of the origin of GSC, which is important for improving clinical outcomes, still remains open. It is believed that GSCs can be formed as a result of oncogenic transformation of neural stem and progenitor cells (NSPcs), which have morphological and functional properties similar to them. Despite significant progress in elucidating the nature of GSCs, little is yet known about the specifically expressed genes and transcripts in these cells in comparison with NSPcs. In this regard, it becomes relevant to study the molecular mechanisms of gliomagenesis using model cell systems based on various clones of GSC.

Aim. To conduct a comparative transcriptomic analysis of CD133⁺-NSPCs and CD133⁺-GSCs to study the molecular genetic differences between the phenotypes of these cells and identify potential targets for therapeutic effects on GSCs.

Materials and methods. Used: highly sensitive transcriptomic analysis on high-density microarrays, cellular technologies, modern bioinformatics analysis.

Results. Transcriptomic analysis of CD133⁺-GSCs and CD133⁺-NSPCs identified 1825 differentially expressed genes. The biological processes and signaling cascades activated in CD133⁺-GSCs have been established. It was shown that significant transcriptomic aberrations in CD133⁺-GSC compared to CD133⁺-NSPC are primarily due to a group of transcripts regulated by the Shh (Sonic hedgehog), mTOR (mammalian target of rapamycin), ALK (anaplastic lymphoma kinase) signaling cascades, transcription factors E2F1, PRC2, HOXA9, MYC, as well as oncogenes ERBB2 and KRAS. Six transcripts (AQP9, TOX15, HOXB2, STEAP3, TREM1, RFC2) highly expressed in CD133⁺-GSC and closely associated with the survival of patients with glioblastoma, which may be potential targets for therapeutic effects on CD133⁺-GSC associated with gliomagenesis, which may be potential targets for therapeutic effects on CD133⁺-GSC, have been identified and annotated.

Conclusion. The data obtained indicate a number of significant molecular genetic differences between the two cell phenotypes, which can be used in the development of new therapeutic approaches for the treatment of glioblastoma.

Introduction. Rearrangement of molecular pathways and activation of bypass signaling determine the progression of tumor cell resistance to various drugs. Study of the common features of resistant formation mechanisms is essential for breast and other cancer beneficial treatments.

Materials and methods. The present work was performed on estrogen receptor α ERα-positive (ERα – estrogen receptor α) McF-7 breast cancer cells, established sublines resistant to the mTOR inhibitor rapamycin or antiestrogen tamoxifen, and ERα-negative MDA-MB-231 breast cancer cells. Methods used include MTT test, transient transfection, immunoblotting, real-time polymerase chain reaction and methylation analysis by bisulfite pyrosequencing.

Results. We have shown that the resistance of breast cancer cells to targeted and hormonal drugs is associated with the suppression of DNA methyltransferase 3A (DNMT3A) and respective changes in DNA methylation; DNMT3A knockdown results in the partial resistance to both drugs demonstrating the pivotal role of DNMT3A suppression in the progression of cell resistance.

Conclusion. Totally, the results obtained highlight the possible mechanism of tumor cell resistance to targeting/hormonal drugs based on the deregulation of DNMTs expression and demonstrate  direct connection between DNMT3A suppression and resistance progression.