Telomeres and telomerase in endometrial cancer and hyperplasia.

Introduction: The study aimed to measure telomeres length (TL) and telomerase expression in normal endometrium and endometrial hyperplasia and cancer. Methods: Total RNA and DNA were isolated from endometrium samples of 117 patients. The RT-PCR method was used to determine telomerase expression and relative telomere length. Results: The control group had the longest telomeres in comparison to the hyperplasia and endometrial cancer groups. Only in the endometrial cancer group was telomerase expressed and positively correlated with telomere length. Conclusions: Telomere extension in endometrial cancer is mediated by telomerase, but telomere length may not be an indicator of endometrioid cancer development.

Current Understanding on Why Ovarian Cancer Is Resistant to Immune Checkpoint Inhibitors.

The standard treatment of ovarian cancer (OC) patients, including debulking surgery and first-line chemotherapy, is unsatisfactory because of recurrent episodes in the majority (~70%) of patients with advanced OC. Clinical trials have shown only a modest (10-15%) response of OC individuals to treatment based on immune checkpoint inhibitors (ICIs). The resistance of OC to therapy is caused by various factors, including OC heterogeneity, low density of tumor-infiltrating lymphocytes (TILs), non-cellular and cellular interactions in the tumor microenvironment (TME), as well as a network of microRNA regulating immune checkpoint pathways. Moreover, ICIs are the most efficient in tumors that are marked by high microsatellite instability and high tumor mutation burden, which is rare among OC patients. The great challenge in ICI implementation is connected with distinguishing hyper-, pseudo-, and real progression of the disease. The understanding of the immunological, molecular, and genetic mechanisms of OC resistance is crucial to selecting the group of OC individuals in whom personalized treatment would be beneficial. In this review, we summarize current knowledge about the selected factors inducing OC resistance and discuss the future directions of ICI-based immunotherapy development for OC patients.

Expression of Gal-9 on Dendritic Cells and Soluble Forms of TIM-3/Gal-9 in Patients Suffering from Endometriosis.

Immune system dysregulation is clinically evident in the pathogenesis of endometriosis (EMS). Changes in the dendritic cells (DCs) activity or phenotype may be involved in the implantation and growth of endometrial tissue outside the uterus in the disease. The TIM-3/Gal-9 axis is implicated in the development of immune tolerance. However, the knowledge about the exact role of this pathway in the EMS is extremely poor. In the present study, we evaluated the expression of Gal-9 on myeloid DCs (mDCs) and plasmacytoid DCs (pDCs) in the peripheral blood (PB) and peritoneal fluid (PF) of both EMS patients (n = 82) and healthy subjects (n = 10) via flow cytometry. We also investigated the concentrations of soluble Gal-9 and TIM-3 in the plasma and PF of EMS patients and the control group using ELISA. We showed significantly elevated percentages of mDCs-Gal-9+ and pDCs-Gal-9+, and significantly higher concentrations of the soluble form of Gal-9 and TIM-3 in the PF of EMS patients than in circulation. Our results led us to conclude that the accumulation of Gal-9 expressing mDCs and pDCs in the PF and high sTIM-3/Gal-9 production in the peritoneal cavity could represent the hallmark of immune regulation in EMS patients, which may augment the inflammatory process and development/maintenance of local immunosuppression.

γδ T Lymphocytes as a Double-Edged Sword-State of the Art in Gynecological Diseases.

Human gamma-delta (γδ) T cells are a heterogeneous cell population that bridges the gap between innate and acquired immunity. They are involved in a variety of immunological processes, including tumor escape mechanisms. However, by being prolific cytokine producers, these lymphocytes also participate in antitumor cytotoxicity. Which one of the two possibilities takes place depends on the tumor microenvironment (TME) and the subpopulation of γδ T lymphocytes. The aim of this paper is to summarize existing knowledge about the phenotype and dual role of γδ T cells in cancers, including ovarian cancer (OC). OC is the third most common gynecological cancer and the most lethal gynecological malignancy. Anticancer immunity in OC is modulated by the TME, including by immunosuppressive cells, cytokines, and soluble factors. Immune cells are exposed in the TME to many signals that determine their immunophenotype and can manipulate their functions. The significance of γδ T cells in the pathophysiology of OC is enigmatic and remains to be investigated.

Clinical Significance of Tie-2-Expressing Monocytes/Macrophages and Angiopoietins in the Progression of Ovarian Cancer-State-of-the-Art.

Tumour growth and metastasis are specific to advanced stages of epithelial ovarian cancer (EOC). Tumour angiogenesis is an essential part of these processes. It is responsible for providing tumours with nutrients, metabolites, and cytokines and facilitates tumour and immune cell relocation. Destabilised vasculature, a distinctive feature of tumours, is also responsible for compromising drug delivery into the bulk. Angiogenesis is a complex process that largely depends on how the tumour microenvironment (TME) is composed and how a specific organ is formed. There are contrary reports on whether Tie-2-expressing monocytes/macrophages (TEMs) reported as the proangiogenic population of monocytes have any impact on tumour development. The aim of this paper is to summarise knowledge about ovarian-cancer-specific angiogenesis and the unique role of Tie-2-expressing monocytes/macrophages in this process. The significance of this cell subpopulation for the pathophysiology of EOC remains to be investigated.

The Dual Blockade of the TIGIT and PD-1/PD-L1 Pathway as a New Hope for Ovarian Cancer Patients.

The prognosis for ovarian cancer (OC) patients is poor and the five-year survival rate is only 47%. Immune checkpoints (ICPs) appear to be the potential targets in up-and-coming OC treatment. However, the response of OC patients to immunotherapy based on programmed cell death pathway (PD-1/PD-L1) inhibitors totals only 6-15%. The promising approach is a combined therapy, including other ICPs such as the T-cell immunoglobulin and ITIM domain/CD155/DNAX accessory molecule-1 (TIGIT/CD155/DNAM-1) axis. Preclinical studies in a murine model of colorectal cancer showed that the dual blockade of PD-1/PD-L1 and TIGIT led to remission in the whole studied group vs. the regression of the tumors with the blockade of a single pathway. The approach stimulates the effector activity of T cells and NK cells, and redirects the immune system activity against the tumor. The understanding of the synergistic action of the TIGIT and PD-1/PD-L1 blockade is, however, poor. Thus, the aim of this review is to summarize the current knowledge about the mode of action of the dual TIGIT and PD-1/PD-L1 blockade and its potential benefits for OC patients. Considering the positive impact of this combined therapy in malignancies, including lung and colorectal cancer, it appears to be a promising approach in OC treatment.

Clinical Value of the PD-1/PD-L1/PD-L2 Pathway in Patients Suffering from Endometriosis.

The interaction between dendritic cells (DCs) and T cells mediated by the programmed cell death 1 (PD-1)/programmed cell death ligand 1 (PD-L1)/programmed cell death ligand 2 (PD-L2) pathway is the most important point in regulating immunological tolerance and autoimmunity. Disturbances in the quantity, maturity, and activity of DCs may be involved in the implantation and growth of endometrial tissue outside the uterus in endometriosis (EMS). However, little is known about the role of the immune checkpoint pathways in EMS. In our study, we examined the expression of PD-L1/PD-L2 on myeloid DCs (mDCs) and plasmacytoid DCs (pDCs) in the peripheral blood (PB) and peritoneal fluid (PF) of both EMS patients (n = 72) and healthy subjects (n = 20) via flow cytometry. The concentration of soluble PD-L1 and PD-L2 in the plasma and PF of EMS patients and the control group were determined using ELISA. We demonstrated an elevated percentage of mDCs, mDCs and pDCs with the PD-L1or PD-L2 expression, and a higher concentration of the soluble forms of PD-L1 and PD-L2 in the PF than in the plasma of EMS patients. We conclude that the peritoneal cavity environment and the PD-1/PD-L1/PD-L2 axis may play an important role in the modulation of immune response and the development and/or progression of EMS.

Immunohistochemical Expression of LHRH Receptor in Different Compartments of Female Genital Tract in Patients With Endometrial Cancer.

Luteinizing hormone-releasing hormone receptor (LHRHR) expression has been reported in various cancers, including endometrial neoplasms. Thus, LHRHR provides a potential point for therapeutic approach using LHRH analogs as carrier molecules for chemotherapeutic agents in this cancer population. However, clinical data did not prove any potential benefits for patients. We decided to assess LHRHR expression in patients with endometrial cancer to explain possible lack of efficacy in previous clinical reports. LHRHR expression was assessed immunohistochemically in different anatomic and histogenetic compartments of female genital tract of patients with endometrial cancer. The study sample consisted of paraffin tissue blocks obtained from patients who has undergone primary surgery owing to endometrial cancer. Strong LHRHR expression was found in endometrial cancer, fallopian tube, and concurrent atypical hyperplasia. Interestingly, LHRHR expression showed significant differences depending on the respective compartment of the ovary analyzed. Level of LHRHR expression in patients with primary advanced and unresectable disease, particularly in certain ovarian compartments may be substantially lower, which may influence the use of new targeted therapy regimens. The studies on secondary Müllerian system compartment and its hormonal receptor status may be crucial to understand mechanisms of lack of efficacy of LHRH hybrid molecules anti-cancer treatment.

The Role of the Adipokine Resistin in the Pathogenesis and Progression of Epithelial Ovarian Cancer.

Obesity is a civilization disease associated with an increased risk of developing cardiovascular diseases, diabetes, and some malignancies. The results concerning the relationship between obesity and epithelial ovarian cancer (EOC) are inconclusive. The higher incidence of neoplasms in obese subjects has led to the development of the adipokine hypothesis. Omental adipocyte cells interact with cancer cells, promoting their migration and metastasis via the secretion of adipokines, growth factors, and hormones. One of the adipokines is resistin. It was shown in vitro that resistin stimulates the growth and differentiation of ovarian cancer cells. Moreover, it increases the level of angiogenesis factors, e.g., matrix metalloproteinase 2 (MMP-2) and vascular epithelial growth factor (VEGF). Additionally, resistin induces epithelial-mesenchymal transition (EMT) and stemness in EOC cell lines. A positive correlation has been shown between a higher level of resistin expression and the stage of histological differentiation of EOC or the occurrence of lymph node metastases. In addition, the overexpression of resistin has been found to act as an independent factor determining disease-free survival as well as overall survival in EOC patients. Growing evidence supports the finding that resistin plays an important role in some mechanisms leading to the progression of EOC, though this issue still requires further research.

Clinical and Prognostic Value of Antigen-Presenting Cells with PD-L1/PD-L2 Expression in Ovarian Cancer Patients.

The latest literature demonstrates the predominant role of the programmed cell death axis (PD-1/PD-L1/PD-L2) in ovarian cancer (OC) pathogenesis. However, data concerning this issue is ambiguous. Our research aimed to evaluate the clinical importance of PD-L1/PD-L2 expression in OC environments. We evaluated the role of PD-L1/PD-L2 in OC patients (n = 53). The analysis was performed via flow cytometry on myeloid (mDCs) and plasmacytoid dendritic cells (pDCs) and monocytes/macrophages (MO/MA) in peripheral blood, peritoneal fluid (PF), and tumor tissue (TT). The data were correlated with clinicopathological characteristics and prognosis of OC patients. The concentration of soluble PD-L1 (sPD-L1) and PD-1 in the plasma and PF were determined by ELISA. We established an accumulation of PD-L1+/PD-L2+ mDCs, pDCs, and MA in the tumor microenvironment. We showed an elevated level of sPD-L1 in the PF of OC patients in comparison to plasma and healthy subjects. sPD-L1 levels in PF showed a positive relationship with Ca125 concentration. Moreover, we established an association between higher sPD-L1 levels in PF and shorter survival of OC patients. An accumulation of PD-L1+/PD-L2+ mDCs, pDCs, and MA in the TT and high sPD-L1 levels in PF could represent the hallmark of immune regulation in OC patients.

Lensoside Aß as an Adjuvant to the Anti-Glioma Potential of Sorafenib.

AIM: The anti-glioma effect of lensoside Aß alone and in combination with sorafenib (pro-survival Raf kinase inhibitor) was evaluated for the first time in terms of programmed cell death induction in anaplastic astrocytoma and glioblastoma multiforme cell lines as an experimental model. Apoptosis, autophagy, and necrosis were identified microscopically (fluorescence and scanning microscopes) and confirmed by flow cytometry (mitochondrial membrane potential MMP and cell death). The expression of apoptotic (caspase 3) and autophagic markers (beclin 1) as well as Raf kinase were estimated by immunoblotting. The FTIR method was used to determine the interaction of the studied drugs with lipid and protein groups within cells, while the modes of drug action within the cells were assessed with the FLIM technique. RESULTS: Lensoside Aß itself does not exhibit anti-glioma activity but significantly enhances the anti-cancer potential of sorafenib, initiating mainly apoptosis of up to 90% of cells. It was correlated with an increased level of active caspase 3, a reduced MMP value, and a lower level of Raf kinase. The interaction with membrane structures led to morphological changes typical of programmed death. CONCLUSIONS: Our results indicate that lensoside Aß plays an important role as an adjuvant in chemotherapy with sorafenib and may be a potential candidate in anti-glioma combination therapy.

Involvement of PI3K Pathway in Glioma Cell Resistance to Temozolomide Treatment.

The aim of the study was to investigate the anticancer potential of LY294002 (PI3K inhibitor) and temozolomide using glioblastoma multiforme (T98G) and anaplastic astrocytoma (MOGGCCM) cells. Apoptosis, autophagy, necrosis, and granules in the cytoplasm were identified microscopically (fluorescence and electron microscopes). The mitochondrial membrane potential was studied by flow cytometry. The activity of caspases 3, 8, and 9 and Akt was evaluated fluorometrically, while the expression of Beclin 1, PI3K, Akt, mTOR, caspase 12, and Hsp27 was determined by immunoblotting. SiRNA was used to block Hsp27 and PI3K expression. Cell migration and localization of Hsp27 were tested with the wound healing assay and immunocytochemistry, respectively. LY294002 effectively diminished the migratory potential and increased programmed death of T98G and MOGGCCM. Autophagy was dominant in MOGGCCM, while apoptosis was dominant in T98G. LY294002 with temozolomide did not potentiate cell death but redirected autophagy toward apoptosis, which was correlated with ER stress. A similar effect was observed after blocking PI3K expression with siRNA. Transfection with Hsp27 siRNA significantly increased apoptosis related to ER stress. Our results indicate that inhibition of the PI3K/Akt/mTOR pathway sensitizes glioma cells to apoptosis upon temozolomide treatment, which was correlated with ER stress. Hsp27 increases the resistance of glioma cells to cell death upon temozolomide treatment.

The Role of Myeloid-Derived Suppressor Cells (MDSCs) in the Development and/or Progression of Endometriosis-State of the Art.

Endometriosis (EMS) is a common gynecological disease characterized by the presence of endometrial tissue outside the uterus. Approximately 10% of women around the world suffer from this disease. Recent studies suggest that endometriosis has potential to transform into endometriosis-associated ovarian cancer (EAOC). Endometriosis is connected with chronic inflammation and changes in the phenotype, activity, and function of immune cells. The underlying mechanisms include quantitative and functional disturbances of neutrophils, monocytes/macrophages (MO/MA), natural killer cells (NK), and T cells. A few reports have shown that immunosuppressive cells such as regulatory T cells (Tregs) and myeloid-derived suppressor cells (MDSCs) may promote the progression of endometriosis. MDSCs are a heterogeneous population of immature myeloid cells (dendritic cells, granulocytes, and MO/MA precursors), which play an important role in the development of immunological diseases such as chronic inflammation and cancer. The presence of MDSCs in pathological conditions correlates with immunosuppression, angiogenesis, or release of growth factors and cytokines, which promote progression of these diseases. In this paper, we review the impact of MDSCs on different populations of immune cells, focusing on their immunosuppressive role in the immune system, which may be related with the pathogenesis and/or progression of endometriosis and its transformation into ovarian cancer.

Gender Dysphoria Disrupting the Course of Treatment of a Recurrent Juvenile Granulosa Cell Tumor in an Adolescent Female: A Case Report.

We present the case of an adolescent female patient with gender dysphoria (GD) who was diagnosed with a recurrent ovarian neoplasm - juvenile granulosa cell tumor (JGCT). The 17-year-old female patient presented multiple endocrine pathologies and a recurrent JGCT. During the surgery qualification process, the patient admitted having identified herself as a male. The patient reported being uncomfortable with her body and with the expected roles of her assigned gender. Due to that, the patient requested a total hysterectomy with a bilateral salpingo-oophorectomy. As a minor, she required the permission of her parents, which was not granted. The patient underwent several specialist consultations, after which she agreed to the unilateral removal of tumor-changed pathologies and additional hormonal, psychological, and psychiatric diagnostics. To the best of our knowledge, this is the first detailed report of co-occurrence of GD spectrum disorders and JGCT in an adolescent female. This case contains many therapeutic and ethical problems regarding both physical and mental health. It should be noted that adolescents with GD spectrum rarely develop persistent transsexuality. Modulations from developmental psychology, psychotherapy, family dynamics, hormonal treatment, and the removal of JGCT in the presented case may have potential therapeutic implications for GD.

Programmed Death-1 Receptor (PD-1) as a Potential Prognosis Biomarker for Ovarian Cancer Patients.

AIM: Ovarian cancer (OC) is one of the most lethal gynecological malignancies. Recent studies suggest a crucial role of the PD-1/PD-L1 pathway in OC pathogenesis. Therefore, our study aimed at evaluation of the clinical importance of PD-1 expression in ovarian cancer patients. PATIENTS AND METHODS: In this study, we investigated the role of PD-1 in OC patients (n=50) by analyzing its expression on CD4+ and CD8+ T cells in three OC environments: peripheral blood (PB), peritoneal fluid (PF), and tumor (TT) as well as soluble PD-1 (sPD-1) in plasma and PF in terms of their clinical and prognostic significance. T cells with PD-1 expression were analyzed using flow cytometry. The concentration of sPD-1 was determined with the use of ELISA. Our research demonstrated differences in PD-1 expression on CD4+ and CD8+ T cells in the OC environments. RESULTS: We found an elevated level of CD4+PD-1+ T cells in tumor and PF, compared to PB. Additionally, we found the highest percentage of CD8+ PD-1+ in tumor, compared to PB and PF. The levels of sPD-1 were higher (p<0.0001) in plasma than in PF. For the first time, we discovered that the higher level of CD4+PD-1+ T cells in the circulation and the higher sPD-1 level in plasma predict poor survival of OC patients. CONCLUSION: We suggest that PD-1 could be a predictive biomarker for OC patients and successful immunotherapy.

Prognostic and Clinical Value of Interleukin 6 and CD45+CD14+ Inflammatory Cells with PD-L1+/PD-L2+ Expression in Patients with Different Manifestation of Ovarian Cancer.

Ovarian cancer (OC) is one of the deadliest gynecological cancers. Recent studies suggest a crucial role of inflammatory immune system cells in the progression and metastasis of OC. The understanding of inflammatory mechanisms is pivotal for the selection of a biomarker that allows the differentiation between malignant and benign tumors, monitoring the progression of the disease, and identification of patients that will respond to implemented treatment. Our study is aimed at evaluating the profile of IL-6 in the plasma and peritoneal fluid (PF) of patients with various clinical manifestations of OC (n = 78). We also examined the relationship between IL-6 and PD-L1/PD-L2 positive CD45+CD14+ inflammatory cell (MO/MA) levels in three OC environments (TME): peripheral blood (PB), PF, and tumor (TT) and their clinical and prognostic relevance in OC patients. The expression of PD-L1/PD-L2 molecules was analyzed by flow cytometry. The IL-6 levels were determined by ELISA. We found an elevated level of PD-L1/PD-L2 positive MO/MA in TT compared to PB (p < 0.0001). Significantly higher (p < 0.0001) levels of IL-6 were observed in PF of the OC patients than in the benign ovarian tumor group (n = 31). Additionally, we found higher IL-6 levels in PF than in the plasma of the OC patients. Interestingly, accumulation of IL-6 was observed in PF of patients with low-differentiated OC and correlated with worse prognosis. Moreover, we observed correlations between the level of IL-6 and CD45+CD14+ cells and between CD45+CD14+PD-L1+ cells and the IL-6 level in PF. For the first time, we discovered that the higher percentage of CD45+CD14+PD-L2+ cells in PF predicts better survival of OC patients. Our study suggests that CD45+CD14+PD-L2+ cells and IL-6 may be predictive biomarkers for OC patients. Understanding how the composition of TME changes during OC development and progression is a prerequisite for projecting new therapeutic strategies. Overall, further validation research is warranted.

Cancer SLC43A2 alters T cell methionine metabolism and histone methylation.

Abnormal epigenetic patterns correlate with effector T cell malfunction in tumours1-4, but the cause of this link is unknown. Here we show that tumour cells disrupt methionine metabolism in CD8+ T cells, thereby lowering intracellular levels of methionine and the methyl donor S-adenosylmethionine (SAM) and resulting in loss of dimethylation at lysine 79 of histone H3 (H3K79me2). Loss of H3K79me2 led to low expression of STAT5 and impaired T cell immunity. Mechanistically, tumour cells avidly consumed methionine and outcompeted T cells for methionine by expressing high levels of the methionine transporter SLC43A2. Genetic and biochemical inhibition of tumour SLC43A2 restored H3K79me2 in T cells, thereby boosting spontaneous and checkpoint-induced tumour immunity. Moreover, methionine supplementation improved the expression of H3K79me2 and STAT5 in T cells, and this was accompanied by increased T cell immunity in tumour-bearing mice and patients with colon cancer. Clinically, tumour SLC43A2 correlated negatively with T cell histone methylation and functional gene signatures. Our results identify a mechanistic connection between methionine metabolism, histone patterns, and T cell immunity in the tumour microenvironment. Thus, cancer methionine consumption is an immune evasion mechanism, and targeting cancer methionine signalling may provide an immunotherapeutic approach.

Potentilla alba Extracts Affect the Viability and Proliferation of Non-Cancerous and Cancerous Colon Human Epithelial Cells.

The aim of this study was to determine the anti-tumor activity of extracts isolated from Potentilla alba L. on human colon cancer cells of the HT-29 line and on non-cancer colon epithelial cells of the CCD 841 CoTr line. The research methods we used to determine the cytotoxic and proliferative properties were 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and neutral red (NR) assays, the ability to produce nitric oxide, the Griess method, and the biochemical properties like 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) methods indicating reduction activity of tested samples. Finally, the effects of the extracts on the morphology and cell counts were assessed by May-Grünwald-Giemsa staining. After a comprehensive analysis of all the experiments, the extracts were found to demonstrate cytotoxic properties, they stimulated the division of non-cancer cells, and they were able to scavenge free radicals. In the NR method, the cell viability dropped to approximately 80% compared to the control. In the MTT assay, tumor cell proliferation decreased to 9.5% compared to the control. Therefore, we concluded that this plant has medical potential.

Coumarins modulate the anti-glioma properties of temozolomide.

In the recent years, coumarin bioactive compounds have been identified to posess anticancer properties. Therefore, the aim of the present study was to investigate for the first time the efficacy of osthole, umbelliferone, esculin, and 4-hydroxycoumarin, alone and in combination with Temozolomide, in the elimination of deadly brain tumors, anaplastic astrocytoma (AA) and glioblastoma multiforme (GBM) cells via programmed death. Our results indicated that osthole, umbelliferone, esculin, and 4-hydroxycoumarin initiated mainly apoptosis in the T98G and MOGGCCM cells. Osthole was the most effective. It also initiated autophagy in a small percentage of the cell population. The co-incubation with Temozolomide did not increase the pro-apoptotic potential of natural compounds but decreased the level of autophagy in the T98G cells. Apoptosis was associated with reduced mitochondrial membrane potential, activation of caspase 3, inhibition of Bcl-2 expression and the presence of a Bcl-2/Beclin 1. Blocking of Bcl-2 expression resulted in promotion of apoptosis, but not autophagy, in the MOGGCCM and T98G lines. It also sensitized astrocytoma cells, but not GBM, to the combined osthole and TMZ treatment, which was correlated with a reduced level of Beclin 1 and increased expression of caspase 3. Osthole and TMZ, alone and in combination, inhibited the migratory phenotype of the GBM and AA cells. In summary, our results indicated that osthole effectively eliminated glioma cells via apoptosis, what was correlated with Bcl-2/Beclin 1 complex formation. Considering the anti-migratory effect, osthole and Temozolomide display antiglioma potential but it needs further extensive studies.

Th17 Cells and IL-17 As Novel Immune Targets in Ovarian Cancer Therapy.

Ovarian cancer (OC) is usually diagnosed at an advanced stage and is related with poor prognosis. Despite numerous studies, the pathogenesis of OC is still unknown. Recent studies indicate the role of the immune system in the development and spread of OC. The identification of factors and mechanisms involved in that process and their modulation is crucial for creating effective antitumor therapy. We investigated the potential role of Th17 cells in OC patients (n = 71) by analyzing the frequencies of Th17 cells in three different environments, i.e., peripheral blood (PB), peritoneal fluid (PF), and tissue (Th17 infiltrating cells), and the concentration of IL-17A in plasma and PF of patients in terms of their clinical and prognostic significance. Th17 cells were analyzed by flow cytometry as a percentage of CD4+ lymphocytes that expressed intracellular expression of IL-17A. The level of IL-17A in plasma and PF were determined by ELISA. Our results showed accumulation of Th17 cells among tumor-infiltrating CD4+ lymphocytes (p < 0.001 in relation to PB). Moreover, the percentage of Th17 cells in both PB and PF of OC patients was significantly lower than that in benign tumors group (n = 35). There were no significant differences in the percentage of Th17 cells in PB, PF, and tissue in relation to clinicopathological characteristics of OC patients and survival. The lower percentage of Th17 cells in the PB and PF of OC patients may promote evasion of host immune response by cancer cells. The concentration of IL-17A in plasma of OC patients was higher (p < 0.0001) than that in both benign tumors and control group (n = 10). The PF IL-17A level in OC patients was higher (p < 0.0001) than that in women with benign ovarian tumors, indicating its synthesis in OC microenvironment. Higher IL-17A level in PF is correlated with longer (median: 36.5 vs. 27 months) survival of OC patients.