ANTICANCER IMMUNOGENIC POTENTIAL OF ONCOLYTIC PEPTIDES: RECENT ADVANCES AND NEW PROSPECTS.

Oncolytic peptides are derived from natural host defense peptides/antimicrobial peptides produced in a wide variety of life forms. Over the past two decades, they have attracted much attention in both basic research and clinical applications. Oncolytic peptides were expected to act primarily on tumor cells and also trigger the immunogenic cell death. Their ability in the tumor microenvironment remodeling and potentiating the anticancer immunity has long been ignored. Despite the promising results, clinical application of oncolytic peptides is still hindered by their unsatisfactory bioactivity and toxicity to normal cells. To ensure safer therapy, various approaches are being developed. The idea of the Ukrainian research group was to equip peptide molecules with a "molecular photoswitch" - a diarylethene fragment capable of photoisomerization, allowing for the localized photoactivation of peptides within tumors reducing side effects. Such oncolytic peptides that may induce the membrane lysis-mediated cancer cell death and subsequent anticancer immune responses in combination with the low toxicity to normal cells have provided a new paradigm for cancer therapy. This review gives an overview of the broad effects and perspectives of oncolytic peptides in anticancer immunity highlighting the potential issues related to the use of oncolytic peptides in cancer immunotherapy. We summarize the current status of research on peptide-based tumor immunotherapy in combination with other therapies including immune checkpoint inhibitors, chemotherapy, and targeted therapy.

COMPARISON OF 2D AND 3D PRIMARY CELL CULTURES OBTAINED FROM EXPLANT OF HIGH-GRADE UROTHELIAL BLADDER CANCER.

Studying the biological characteristics of bladder cancer in primary culture can be an effective way for diagnostic and prognostic purposes, as well as choosing a scheme for personalized therapy. AIM: To characterize and compare 2D and 3D primary cell cultures obtained from the same tumor sample resected from a patient with high-grade bladder cancer. MATERIALS AND METHODS: 2D and 3D primary cell cultures were obtained from explants of resected bladder cancer. Glucose metabolism, lactate dehydrogenase (LDH) activity, and level of apoptosis were studied. RESULTS: Multicellular tumor spheroids (3D) differ from planar culture (2D) by more pronounced consumption of glucose from the culture medium (1.7 times higher than 2D on Day 3 of culture), increased lactate dehydrogenase activity (2.5 times higher on Day 3 vs. Day 1 of cultivation, while in 2D culture LDH activity is constant), stronger acidification of the extracellular environment (pH dropped by 1 in 3D and by 0.5 in 2D). Spheroids demonstrate enhanced resistance to apoptosis (1.4 times higher). CONCLUSION: This methodological technique can be used both for tumor characterization and for selection of optimal postoperative chemotherapeutic schemes.

DENDRITIC CELLS IN GLIOBLASTOMA TREATMENT: A MODERN VIEW OF THE PROBLEM AND OWN EXPERIENCE.

Glioblastoma (GBM) is the most aggressive primary malignant brain tumor in adults. The improvement of the efficacy of GBM treatment is an urgent problem encouraging the development of novel therapeutic strategies, in particular, immunotherapeutic modalities. With more understanding of the intimate interrelationships between the immune system and the mechanisms involved in cancer origin and progression, the skepticism related to the relevance of the immunotherapeutic approaches in the treatment of brain tumors is gradually decreasing. The review discloses the modern concepts on the association between CNS and the immune system. For a long time, CNS was considered as the immunoprivileged site that prevents the effects of immunotherapy in the treatment of brain tumors. Nowadays, these views are reconsidered, which opens the way to the use of immunotherapeutic approaches in GBM treatment. The results of the recent clinical trials on immunotherapy as a supplement to the conventional GBM treatment are considered. Vaccines based on the dendritic cell (DC) technology are regarded as the most promising for this purpose. The preliminary results of the Ukrainian clinical study are also presented and discussed. The results of the international clinical trials as well as our own experience give evidence of the relevance for using DC vaccines in the complex treatment of GBM, which is supported by the increased survival of patients and the safety of vaccine application. It is of high importance that GBM patients with the most unfavorable prognosis can benefit from DC vaccines as a component of the complex treatment. The prospects for immunotherapy in neurooncology are discussed.

Magnetically sensitive nanocomplex enhances antitumor efficacy of dendritic cell-based immunotherapy.

BACKGROUND: One of the major factors restricting in vivo efficacy of dendritic cells (DCs) based immunotherapy is the inefficient migration of these cells to the lymphoid tissue, wherein DCs activate antigen-specific T cells. A fundamentally new approach for the possibility of enhancing the antitumor effects of DC-based immunotherapy may be the use of magnetically sensitive nanocomplexes to increase the target delivery of DCs to the lymph nodes of the recipient. AIM: To study the antitumor and immunomodulatory effects of the DC-nanovaccine with magnetosensitive properties and its influence on the immunosuppressive tumor microenvironment in mice with sarcoma 37. MATERIALS AND METHODS: The antitumor, antimetastatic and immunomodulatory effects of DCs loaded with magnetic nanocomplex under magnetic field (MF) control in mice with sarcoma 37 have been investigated. RESULTS: Combined therapy contributed to a significant reduction in tumor volume and weight compared to the control group of mice and mice that received the DC vaccine without MF. Therapy with magnetically sensitive DC nanovaccine with and without the addition of the MF was accompanied by a significant down-regulation of the level of FoxP3, transforming growth factor ß, interleukin (IL)-10 and vascular endothelial growth factors, mRNA expression in tumor tissues. A significant increase in interferon-γ and IL-4 mRNA expression was found in mice treated with the magnetically sensitive DC nanovaccine under MF control. CONCLUSION: A significant increase in the antitumor efficacy of the DC vaccine can be achieved using magnetosensitive nanocarriers of tumor antigens under MF control.

Expression of TLR4 and major inflammatory cytokines in patients with bladder cancer of different grade and stage.

BACKGROUND: The bladder cancer is immunogenic, and neoantigens generated by tumor cells trigger a notable immune response in the host. On the other hand, multiple immune escape mechanisms allow for avoiding the recognition by the host immune system. Toll-like receptor type 4 and inflammatory cytokines play major role in the immune response to bladder cancer. AIM: To assess the expression of TLR4 and the genes of major inflammatory cytokines in tumor cells and in unaffected tissue of the bladder. MATERIALS AND METHODS: The pairs of samples from the urinary bladder tumor and unaffected adjacent tissue were obtained from 50 surgically treated patients with bladder cancer. The level of expression of TLR4, TGF-ß1, INF-γ, TNF-α genes was evaluated by real-time polymerase chain reaction. RESULTS: Bladder cancer cells are characterized by lower expression levels of TLR4, TGF-ß1, INF-γ, TNF-α as compared to unaffected tissue. In patients with recurrent cancer, expression of TLR-4 and cytokines does not change both in tumor and in unaffected tissue of the bladder. Expression of TLR4 is identically low both in low- and high-grade cancer. Expression levels of the INF-γ and TNF-α are remarkably low in muscle-invasive cancer compared to the unaffected bladder tissue. The level of TGF-ß1 in bladder cancer is comparable to the unaffected tissue of the bladder, while in the intact and metastatic lymph nodes it is significantly upregulated. CONCLUSION: Bladder cancer tissue differs from the unaffected part of the bladder wall in the level of TLR4, TGF-ß1, INF-γ, TNF-α expression.

ROS production by circulating phagocytes and Guerin carcinoma resistance to cisplatin.

BACKGROUND: Tumor drug resistance remains a primary cause of unsuccessful cancer therapy. The search for biological markers of the sensitivity/resistance of malignant neoplasms to drug therapy is an urgent and important task, the solution of which will increase the effectiveness of anticancer chemotherapy. AIM: To study the relationship between the functional activity (parameters of the phagocytosis and reactive oxygen species (ROS) production) of neutrophils and monocytes in the peripheral blood of rats with transplanted Guerin carcinoma and the degree of its sensitivity to cisplatin (Cpt). MATERIALS AND METHODS: The original and Cpt-resistant variants of Guerin carcinoma were transplanted to female Wistar rats 2.5 months old. The parameters of the phagocytic activity of circulating neutrophils and monocytes were determined by the degree of ingestion of inactivated and FITC-labeled staphylococci using flow cytometry. The number of ROS-generating cells and the intensity of ROS production by phagocytes were determined by flow cytometry using 2',7'-dichlorodihydrofluorescein diacetate. RESULTS: The growth of both variants of Guerin carcinoma caused a statistically significant decrease in the intensity of neutrophil phagocytosis by more than 47% with a tendency to the reduction of the intensity of phagocytosis by monocytes. The phagocytic activity of circulating neutrophils and monocytes did not differ significantly between the groups of animals with the original and Cpt-resistant variant of Guerin carcinoma. In contrast, the intensity of ROS generation by both monocytes and neutrophils in the peripheral blood of animals with Cpt-resistant tumor increased by more than 86% as compared to original carcinoma-bearing rats. CONCLUSION: This study provides evidence that the intensity of ROS production by circulating monocytes and neutrophils may reflect the degree of tumor sensitivity to Cpt. Increased intensity of ROS production could serve as a pretreatment predictor of the formation of tumor drug resistance.

Changes in expression of TLR-4, TGF-ß, INF-γ, TNF-α in cultured T24/83 cells of invasive bladder cancer treated with cisplatin and/or polyphenolic adjuvant melanin.

BACKGROUND: Toll-like receptor 4 (TLR4) is known to be involved in carcinogenesis and cancer progression. Changes in TLR4 expression are associated with changes in the expression of key cellular cytokines (transforming growth factor-ß (TGF-ß), tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ)), which affect cancer progression and metastasis. AIM: To study changes in the expression of TLR4, TGF-ß, TNF-α, IFN-γ genes, the level of apoptosis and cell cycle distribution in human invasive urothelial carcinoma T24/83 cells under the treatment with polyphenolic adjuvant compound of fungal origin melanin, cytotoxic drug cisplatin, and combination of both. MATERIALS AND METHODS: T24/83 cells were incubated with cisplatin (0.05 mM), melanin (5 µg/ml), or their combination. The expression level of TLR-4, TGF-ß, INF-γ, TNF-α was evaluated by the real time polymerase chain reaction. The flow cytometry was used to study cell cycle distribution, proliferative activity and level of apoptosis. Morphological analysis of the Т24/83 cells was performed as well. RESULTS: Melanin, cisplatin, and their combination downregulate TLR4 expression (2.67; 1.28; and 2.73-fold decrease, respectively) and TNF-α expression (6.5; 1.4; and 1.7-fold decrease, respectively). Melanin did not affect TGF-ß expression while cisplatin caused 13-fold downregulation of TGF-ß. The combined use of cisplatin and melanin decreased TGF-ß expression by 6.5 times. The upregulation of IFN-γ by melanin, cisplatin, and their combination was demonstrated (4.3; 6.7; and 2-fold increase, respectively). All treatment modalities increased the level of apoptosis in T24/83 cells. Melanin treatment increased significantly the proportion of fibroblast-like cells in T24/83 culture with decreased cell adhesion to the substrate. CONCLUSIONS: Melanin, cisplatin, and combination of both agents affect significantly TLR4, TNF-α, TGF-ß, INF-γ expression, cell cycle distribution and morphology in T24/83 cells suggesting their transition to less aggressive phenotype.

Tumor microenvironment changes tumor cell sensitivity to action of energy metabolism modifiers.

BACKGROUND: Taking into account differences in the bioenergetics between malignant and normal cells a search of antitumor drugs among the modifiers of tumor metabolism has a reasonable excuse. Earlier it was found that the cytotoxic/cytostatic action of sodium dichloroacetate (DCA) against Lewis lung carcinoma (LLC) cells in vitro was enhanced in the case of its combination with metformin (MTF). AIM: To study the antitumor action of DCA in combination with MTF against LLC in vivo. MATERIALS AND METHODS: LLC/R9, a low metastatic variant of LLC cells, was used. LLC/R9 bearing mice were treated with MTF (at a total dose 0.15 g/kg b.w.) alone or in combination with DCA (at a total dose of 0.75 g/kg b.w.). LLC/R9 growth kinetics and the primary tumor growth and metastasis indices on the 23rd day after tumor cell inoculation were evaluated by routine procedures. The state of the electron transport chain of mitochondria in tumor cells was studied using electron paramagnetic resonance. The content of lactate and glucose in blood plasma from mice was measured by enzymatic methods using biochemical analyzer. The number of tumor-associated macrophages (TAMs) and their distribution by M1/M2 phenotype were estimated by flow cytometry using antibodies against CD68 and CD206. RESULTS: In LLC/R9-bearing mice treated with DCA in combination with MTF, tumor growth and metastasis indices, as well as circulating glucose and lactate levels were not significantly different from those in the control group. The level of nitrosylation of non-heme and heme proteins and the content of iron-sulfur centers in the mitochondria of tumor cells in LLC/R9-bearing mice administered with DCA in combination with MTF did not also differ from the corresponding indices in control. Instead, in tumors treated with MTF alone and in combination with DCA the total CD68+ TAMs count was almost 27% (p < 0.05) and 43% lower (p < 0.05) correspondingly than that in control, but this decrease was not accompanied by redistribution of CD68+/CD206+ and CD68+/D206- subsets. CONCLUSION: DCA in combination with MTF, at least in doses applied, did not affect LLC/R9 growth and metastasis in vivo. The complete absence of an antitumor effect of DCA in combination with MTF was simultaneously associated with the absence of significant changes in the functional state of electron transport chain of mitochondria in tumor cells, circulating glucose and lactate levels, and the decrease of the TAMs amount in tumors. It suggests that the antitumor activity of DCA and MTF could be determined by both their local effects within a tumor and their multiple systemic impacts.

Metformin enhances cytotoxic action of dichloroacetate against Lewis lung carcinoma cells in vitro.

Tumor cell metabolism is considered one of the hallmarks of cancer. This concept is exploited in the development of new ways of anticancer therapy based on the use of substances capable of changing drastically bioenergetic metabolism of tumor cells. Among them, sodium dichloroace-tate (DCA), an inhibitor of pyruvate dehydrogenase kinase, and metformin (MTF), an antidiabetic hypoglycemic drug, an inhibitor of the mitochondrial respiratory chain (complex I), both have been long used in clinical non-oncological practice, and presently are considered promising candidates in oncology. AIM: To study the capability of MTF to enhance the antitumor action of DCA against Lewis lung carcinoma cells in vitro. MATERIALS AND METHODS: LLC/R9, a low metastatic variant of Lewis lung carcinoma cells, was used. Effects of 30 mM DCA in combination with 2 mM MTF on cell survival, cell cycle distribution, apoptosis, mitochondrial potential, intracellular ATP level, glucose consumption, and lactate production rates were determined in vitro. RESULTS: MTF was shown to enhance the cytotoxic/cytostatic action of DCA against LLC/R9 cells in vitro. Treatment of LLC/R9 cells with 30 mM DCA in combination with 2 mM MTF resulted in a 39% decrease in the number of viable cells (p < 0.05), a 2.8-fold increase of the number of dead cells (p < 0.05), a near 2-fold decrease in the proportion of cells at the S-phase (p < 0.05), a 4-fold increase in the apoptosis (p < 0.05) and significant reduction (p < 0.05) of the mitochondrial membrane potential of tumor cells as compared to corresponding values in control. DCA alone reduced glucose consumption and lactate production rates by more than 26% (p < 0.05) and 34% (p < 0.05), respectively, whereas MTF counteracted these effects. Nevertheless, in the cells treated with both DCA and DCA in combination with MTF, the intracellular adenosine triphosphate increased by 33-35% compared with that in the control (p < 0.05). CONCLUSION: MTF enhanced the cytotoxic/cytostatic action of DCA against LLC/R9 cells in vitro, which points on their possible synergistic antitumor action in vivo.

Ukraine Data on Prognostic Factors and Treatment Outcomes in Patients with Peripheral T-Cell Lymphomas.

BACKGROUND: Peripheral T-cell lymphomas (PTCLs) is a diverse group of lymphomas (10-15% of all non-Hodgkins lymphomas) with aggressive behavior. Despite the standard of 1st line anthracycline-containing regimens, clinical outcomes are poor compared to B-cell lymphomas. In addition, there are still debates about specific prognostic factors (PF) in PTCLs. AIMS: Primary endpoints - event-free survival (EFS) and overall survival (OS). To evaluate the prognostic significance of five PTCLs scores (International Prognostic Index - IPI, International Peripheral T-cell lymphoma Project Score - IPTCL, Prognostic Index for T-cell lymphoma - PIT, modified Prognostic Index for T-cell lymphoma - mPIT and T-cell score). PATIENTS AND METHODS: From 67 enrolled patients, only 50 were included: PTCL not otherwise specified (22, 44%), anaplastic large cell lymphoma ALK+ (anaplastic lymphoma kinase-positive) (10, 20%) and ALK (anaplastic lymphoma kinase-negative) (18, 36%). Patients received CHOP-like regimens (CHOP, CHOEP, EPOCH). RESULTS: The overall rate response was observed in 66% of cases (complete response 78%). There were 48% of relapses after the 1st line therapy during follow-up (median 11 months; range 1-85 months). Median age 57 (range 22-80) with male predominance 62%. In total, 40% of patients were > 60 years old, 48% had stage III-IV. Majority of patients were assessed by five prognostic scores. IPI (45 patients): the 3-year EFS and OS were higher for IPI 1 vs. IPI > 2 (80 vs. 18% and 87 vs. 27%, respectively; p = 0.0002). Receiver operating characteristic analysis confirmed poor clinical outcome to patients with PF > 1 (Se = 88 %; Sp = 68 %; AUC = 0.7; p = 0.0081). IPTCLP (41 patients): the presence of PF = 1-2 showed EFS and OS reduction. A 3-year EFS rate for 1-2 PF was 25 vs. 70% for PF = 0 (p = 0.003). Thus, 3-year OS in patients with PF = 0 vs. PF = 1-2 was 100 vs. 20% (p = 0.0001). PIT (42 patients): better 3-year EFS and OS in patients with PF = 0 vs. PF = 1-3 (88 vs. 28% and 100 vs. 34%, respectively, p = 0.001). Patients with PF = 1-3 have a higher rate of relapses vs. PF = 0 (p = 0.0005 by Cox-test). mPIT (21 patients): no significant difference between PF and clinical outcomes. T-cell score (18 patients): higher survival rates with PF 2. More than 2 PF have an impact on EFS (p = 0.005). The 3-years OS in patients with PF 2 was 77 vs. 25% in cases with PF 3 (p = 0.001). CONCLUSION: IPI, PIT, IPTCLP are still very useful in defining risk stratification. As to mPIT and T-cell score, more patients to evaluate their prognostication possibility are needed.

Prognostic significance of MDM2 gene expression in childhood neuroblastoma.

AIM: To investigate the association of MDM2 expression at the mRNA levels in neuroblastoma with clinical features and unfavorable disease factors to determine the possibility of it usage as a prognostic marker of neuroblastoma. MATERIALS AND METHODS: Total RNA and DNA were extracted from tumor tissue samples of total 91 neuroblastoma patients (mean age: 39.45 ± 4.81 months). MDM2 mRNA levels were detected with Q-PCR. TP53 gene deletion was detected with FISH method. MYCN amplification was detected with -Q-PCR analysis in fresh tumor samples and FISH in FFPE samples. RESULTS: We investigated the association of MDM2 mRNA expression with clinical outcome in neuroblastoma patients (n = 91). Kaplan - Meier curves showed a significant association of high MDM2 expression with poor event-free survival (p < 0.001). Clinical outcome of patients without MYCN amplification with low MDM2 expression was associated with better event-free survival than with high MDM2 expression (p < 0.001). Overexpression of MDM2 can be used as significant prognostic marker for patient stratification on risk groups and treatment optimization. CONCLUSION: Our results showed that the high expression of MDM2 at mRNA levels is an important factor of neuroblastoma prognosis. It may be a valuable additional molecular marker in guiding specific therapy in MYCN non-amplified NB patients without TP53 gene deletion.

Immunological markers of anti-tumor dendritic cells vaccine efficiency in patients with non-small cell lung cancer.

AIM: To investigate the quantitative and functional status of peripheral blood lymphocytes in patients with non-small cell lung cancer during DC-vaccine therapy and identify the most informative immunological parameters which are associated with clinical outcome. MATERIALS AND METHODS: The study was conducted within the framework of randomized phase III clinical trial of DC-vaccine efficacy in patients with non-small cell lung cancer. Quantitative composition of peripheral blood lymphocytes was determined by flow cytometry. Cytokines mRNA expression level was estimated using real-time RT-PCR. RESULTS: In our study the most pronounced changes in the immune system have been defined after fourth DC-vaccine injection. Immunologic features such as reduction the MIP-1α mRNA expression level, increasing the RANTES mRNA expression level and NK-cells count, retention CD4/CD8 ratio at physiological level were associated with favorable clinical outcome after DC-immunotherapy. CONCLUSIONS: Immunological markers established in our investigation can be used for estimation of DC-immunotherapy efficiency. The results of our research are very promising, but these data should be confirmed in further studies with a large cohort of patients.

[Bone and cartilaginous tumours in the sino-paranasal region with intracranial extension. Peculiarities of surgical treatment].

The objective of the present work was to study peculiarities of diagnostics of bone and cartilaginous tumours in the sino-paranasal region with intracranial extension, to substantiate the choice of the strategy and methods for the surgical intervention for the treatment of these neoplasms. The study included 19 patients with various bone and cartilaginous neoplasms in the craniofacial region. Diagnostics was based on computed tomography allowing for 3D reconstruction of the structures of interest, magnetic resonance imaging (with amplification whenever necessary), and angiography. It is proposed to use the microsurgical and pneumatic techniques to ensure the maximally complete removal of the tumours with a minimal injury to the surrounding tissues. The extension of fascial approach is recommended for the management of intracranially spreading tumours. This technique was used for the treatment of 9 patients (7 undergoing anterior craniofacial resection, 1 lateral craniofacial resection, and 1 subcranial resection) in combination with Moure and Denker rhinotomy. The transcranial approach was employed in 8 patients one of whom underwent transoral surgery and another transnasal intervention. Also, the histological structure of the tumours needs to be taken into consideration when planning the approach and the extent of the surgical intervention. It is concluded that preliminary courses of chemo and radiotherapy do not significantly improve the outcome of surgical treatment; in contrast, they promote the development of complications during the postoperative period. The results of this study indicate that for the management of benign tumours characterized by the slow growth rate (osteoma, chondroma, chordoma) the traditional ENT approaches can be supplemented by transcranial surgery. Extensive interventions (anterior craniofacial reseaction, lateral craniofacial resection) are needed for the management of aggressive malignant tumours (ostesarcoma, chondrosarcoma) without serious injury the healthy tissues; moreover, such approach increases the survival rate of the patients.

Comparative analysis of anxiety-like behavior in partition and plus-maze tests after agonistic interactions in mice.

The behavior of C57BL/6J male mice with experience of repeated victories (winners) or defeats (losers) in daily agonistic interactions, was examined in the plus-maze and partition tests. The latter procedure assesses the reactivity of mice to another conspecific in the neighboring compartment of a common cage, communicative behavior or level of sociability. The behavior of mice after 10 days (T10) and 20 days (T20) of agonistic confrontations, as well as in controls (5 days of individual housing) was analyzed. Significant differences were found between T10 and T20 losers and controls in both tests. In the partition test, a decrease in the number of approaches and total and average time spent near the partition was found in T10 and, more pronounced, in T20 losers. In the plus-maze, losers showed fewer open and total entries than controls. Moreover, rarely did they pass from one enclosed arm to another, and also showed a decreased number of 'peepings' from enclosed arms. Percentage of open time did not differ significantly in losers compared to controls. It is suggested that the level of losers' sociability, estimated as low by the partition test, can include anxiety as a component, which is confirmed, at least partly, by some parameters of the plus-maze test. There were no differences in the partition or plus-maze tests between T10 winners and controls. However, all parameters of partition behavior were significantly different between T20 winners and controls. In the plus-maze, similar to losers, T20 winners displayed fewer open arm entries, number of "peepings,' and passages than controls. It was concluded that parameters of the partition and plus-maze tests correlate in mice with the alternative experience of agonistic confrontations, positive or negative. A combination of these two tests may be used for estimation of developing anxiety in mice.

[The effect of the repeated experience of victories and defeats in social conflicts on the function of the brain serotoninergic system in male mice]. / Vliianie povtornogo opyta pobed i porazhenii v sotsial'nykh konfliktakh na sostoianie serotoninergicheskoi sistemy golovnogo mozga samtsov myshei.

Serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) levels, tryptophan hydroxylase (TPH) activity, and 5-HT1A receptor binding were studied in brain areas of male mice after repeated experience of victories (winners) and defeats (losers) in daily male confrontations. A decrease in the TPH activity in midbrain and its decrease in hypothalamus were shown in winners in comparison with controls. The victory experiences were accompanied by a pronounced increase of Bmax of 5-HT1A receptors in the frontal cortex and decrease of Kd in the hypothalamus. Repeated defeats in social confrontations were accompanied by an increase in 5-HT level in the amygdala and increase of 5-HIAA/5-HT index in the hippocampus in comparison with controls. A decrease of Bmax in the hypothalamus and of Kd of 5-HT1A receptors both in the frontal cortex and hypothalamus was shown in losers as compared to controls. An increase in TPH activity under the influence of repeated defeats was shown in striatum and hypothalamus. The obtained evidence point to specific changes in serotonergic activity which characterize aggressive or submissive types of social behaviour, and unspecific changes which are similar in winners and losers and are likely to be induced by social stress.