The Increase of Circulating PD-1- and PD-L1-Expressing Lymphocytes in Endometriosis: Correlation with Clinical and Laboratory Parameters

Exploring the Shared Pathogenesis Mechanisms of Endometriosis and Cancer: Stemness and Targeted Treatments of Its Molecular Pathways-A Narrative Review

Endometriosis is a benign disease but with malignant behavior, sharing numerous features with cancers. Endometriosis is the development of endometrial tissue outside the uterus, with the presence of both glands and stroma. Approximately 10% of women of reproductive age suffer from endometriosis; it involves high social costs and affects the patient's quality of life. In this review, we attempt to capture the pathogenesis mechanisms that are common to endometriosis and cancer based on molecular biology, focusing more on the principle of immunological changes and stemness. Clinical applicability will consist of targeted treatments that represent future directions in these diseases, which impose a burden on the healthcare system. Unlike endometriosis, cancer is a disease with fatal evolution, with conventional treatment based on chemo/radiotherapy. Here, we focus on the niche of personalized treatments that target molecular pathways. Our findings show that, in both pathologies, the resistance to treatments is due to the stemness of the stem cells, which might play a role in the appearance and evolution of both diseases. More research is needed before we can draw firm conclusions.

The Role of NK and T Cells in Endometriosis

Endometriosis, a debilitating condition, affects one in ten women of reproductive age. Its pathophysiology remains unclear, though deficiencies in immune surveillance are thought to create an environment conducive to the evasion of ectopic endometrial cells from the immune system. Our research explores the immunological impact of endometriosis both locally and systemically, emphasizing natural killer (NK) and T cell subpopulations. We incorporated 62 female patients who underwent laparoscopic surgery; of those, 47 had endometriosis, and 15 were controls. We collected peritoneal fluid (PF) and peripheral blood (PB) samples which were tagged with monoclonal antibodies and subsequently scrutinized using flow cytometry. Our findings revealed significant differences in immunological profiles based on demographic factors and symptomatology. In the endometriosis cohort, there was an increase in PB CD56HiCD16dim and PF CD8+ CD56dimCD16Hi NK cells. CD16+ CD4 T cell levels were significantly lower in the PB of endometriosis patients who smoke. Individuals with more severe disease displayed significantly higher levels of PB CD16+ CD8 T cells, which also increased in those with non-menstrual pelvic pain. Dysmenorrhea severity correlated with a progressive increase in PF CD8+ CD56dimCD16Hi NK cells. These variations in specific lymphocyte subsets, namely, within NK and T cells, suggest potential immunological mechanisms in the evolution and clinical presentation of endometriosis.

Efficacy of colchicine and melatonin in the treatment of rat endometriosis model: An animal study

OBJECTIVE

This study investigates the therapeutic effects of colchicine and melatonin on endometriotic implants in an experimentally created endometriosis model in rats.

STUDY DESIGN

Forty-four adult female Wistar albino rats weighing between 260 and 300 g, 8 weeks old, were selected for the study. The unilateral uterine horn of rats with a bicornuate uterus was excised for 1 cm, washed with sterile saline, incised longitudinally, and the endometrium was exposed. A 0.5*0.5 cm endometrial tissue sample taken with a scalpel was implanted with suturing (4/0 Vicryl) to the abdominal wall. Forty-four rats were divided into four groups. Group 1 was randomized as the endometriosis group (control), Group 2 as endometriosis + colchicine treatment, Group 3 as endometriosis + melatonin treatment, and Group 4 as the endometriosis + melatonin + colchicine treatment group. The colchicine (Sigma Chemical Co., St Louis, Missouri) group was administered orally at a dose of 0.1 mg/kg, and the Melatonin group orally at a dose of melatonin (20 mg/kg per day). Treatment continued daily for 30 days.

RESULTS

In the post-treatment focal diameter measurements, the endometrial focal diameter in the colchicine and colchicine + melatonin group was significantly lower than the control group (p=0.026). Bcl-2 levels of the colchicine group were lower than the control group and the melatonin group (p=0.021).

CONCLUSION

Colchicine and melatonin reduce adhesion to the peritoneal surface in ectopic endometrial cells. It also acts by increasing apoptosis and decreasing cell survival.

The dysfunction of CD8+ T cells triggered by endometriotic stromal cells promotes the immune survival of endometriosis

Endometriosis is defined as an oestrogen-dependent and inflammatory gynaecological disease of which the pathogenesis remains unclear. This study aimed to investigate the cellular heterogeneity and reveal the effect of CD8+ T cells on the progress of endometriosis. Three ovarian endometriosis patients were collected, and single-cell RNA sequencing (scRNA-seq) progressed and delineated the cellular landscape of endometriosis containing five cell clusters. The endometrial cells (EMCs) were the major component, of which the mesenchymal cells were preponderant and characterized with increased inflammation and oestrogen synthesis in endometriosis. The proportion of T cells, mainly CD8+ T cells rather than CD4+, was reduced in endometriotic lesions, and the cytokines and cytotoxicity of ectopic T cells were depressed. CD8+ T cells depressed the proliferation of ESCs through inhibiting CDK1/CCNB1 pathway to arrest the cell cycle and triggered inflammation through activating STAT1 pathway. Correspondingly, the coculture with ESCs resulted in the dysfunction of CD8+ T cells through upregulating STAT1/PDCD1 pathway and glycolysis-promoted metabolism reprogramming. The endometriotic lesions were larger in nude mouse models with T-cell deficiency than the normal mouse models. The inhibition of T cells via CD90.2 or CD8A antibody increased the endometriotic lesions in mouse models, and the supplement of T cells to nude mouse models diminished the lesion sizes. In conclusion, this study revealed the global cellular variation of endometriosis among which the cellular count and physiology of EMCs and T cells were significantly changed. The depressed cytotoxicity and aberrant metabolism of CD8+ T cells were induced by ESCs with the activation of STAT1/PDCD1 pathway resulting in immune survival to promote endometriosis.

The PD-1/PD-L1 Gateway: Peripheral Immune Regulation in the Pathogenesis of Endometriosis

Endometriosis is a chronic inflammatory disease characterized by the presence of endometrial-like tissue outside the uterine cavity, causing pain and infertility. Despite the rather unclear etiopathogenesis, recent studies suggest the involvement of the immune system in the development and progression of endometriosis. The role of the PD-1/PD-L1 axis in the modulation of the immune response in this disease seems to be particularly interesting. This preliminary study aimed to investigate the expression of PD-1 and PD-L1 on T and B lymphocytes in peripheral blood in patients with endometriosis to assess their potential impact on disease progression. Our study involved peripheral blood samples from 80 patients diagnosed with endometriosis and 20 healthy women as a control group were analyzed. Flow cytometry was used to assess the expression of PD-1 and PD-L1 on T and B lymphocytes, and enzyme-linked immunosorbent assays were used to assess their soluble forms in serum and peritoneal fluid.in our research we observe significantly higher expression of PD-1 and PD-L1 on T and B lymphocytes was found in patients with endometriosis compared to the control group. Higher expression of both tested molecules correlated with the stage of endometriosis. The results of our preliminary studies indicate a potential role of the PD-1/PD-L1 axis in the modulation of the immune response in endometriosis. Modified expression of these proteins may contribute to immune evasion by ectopic tissues, supporting their survival and proliferation. These findings suggest that targeting PD-1/PD-L1 could be explored as a therapeutic option for the treatment of endometriosis, though further research with larger sample sizes is necessary to confirm these results and clarify the role of PD-1/PD-L1 in the pathogenesis of the disease.

Immune Checkpoints in Endometriosis-A New Insight in the Pathogenesis

Endometriosis (EMS) is an oestrogen-dependent, chronic disease affecting women of a reproductive age. One of the important factors involved in the development of this disease is the complex disorders associated with the functioning of the immune system. Recent evidence has shown that EMS development is associated with changes in systemic and local immunity, including functional disturbances of effector and antigen-presenting cells. One of the reasons for immune imbalance can be the improper expression of immune checkpoints (ICPs). ICPs and their ligands are responsible for maintaining self-tolerance and the modulation of the initiation, duration, and magnitude of the immune response of effector cells in normal tissues to avoid tissue damage. Considering the complex nature of co-stimulatory or co-inhibitory ICPs and the signalling between effector cells and APCs, we hypothesise that changes in cells' activity caused by ICPs may lead to serious immune system disturbances in patients with endometriosis. Moreover, both upregulation and downregulation in the expression of ICPs may be implicated in this process, including the reduced activity of effector cells against endometrial implants and disturbances in the antigen-presenting process. In this narrative review, we discuss, for the first time, key findings from the emerging literature, describing the associations between ICPs and their possible implication in the pathogenesis of endometriosis.

Does Programmed Cell Death 1 Ligand (Pd-L1) Expression Predict Recurrence in Women With Endometrioma?

The study aimed to evaluate whether there is a difference in the expression of programmed cell death 1 ligand (PD-L1) in the cell lining of endometrioma between cases with and without recurrent disease. Additionally, we sought to assess the effect of cyst size and serum CA125 level on the expression of PD-L1 staining. The pathological specimens were immunohistochemically stained for PD-L1 in women who underwent surgery for endometrioma. All patients were evaluated to confirm if their endometriomas had recurred or not. A total of 36 patients who underwent surgery for endometrioma were included. The study population was divided into two groups according to their recurrence status. The study group (having recurrence) (n=12) and the control group (having no recurrence) (n=24) were compared regarding their demographic and clinical characteristics and PD-L1 staining. PD-L1 staining and the intensity of PD-L1 staining did not differ between the patients with and without recurrence. No variable, including parity, cyst size, serum CA125 level, and PD-L1 staining, was found to be significant in determining recurrence. No significant difference was found between the groups with and without PD-L1 staining in terms of cyst size and serum CA125 level. Although we have shown that PD-L1 expression could not be used for the prediction of recurrence, further studies are needed to assess this issue and to guide the development of new immunotherapeutic agents on this basis.

Crimson clues: advancing endometriosis detection and management with novel blood biomarkers

Endometriosis is an inflammatory condition affecting approximately 10% of the female-born population. Despite its prevalence, the lack of noninvasive biomarkers has contributed to an established global diagnostic delay. The intricate pathophysiology of this enigmatic disease may leave signatures in the blood, which, when detected, can be used as noninvasive biomarkers. This review provides an update on how investigators are utilizing the established disease pathways and innovative methodologies, including genome-wide association studies, next-generation sequencing, and machine learning, to unravel the clues left in the blood to develop blood biomarkers. Many blood biomarkers show promise in the discovery phase, but because of a lack of standardized and robust methodologies, they rarely progress to the development stages. However, we are now seeing biomarkers being validated with high diagnostic accuracy and improvements in standardization protocols, providing promise for the future of endometriosis blood biomarkers.

Exploring Patient Adherence to Post-Surgical Follow-Up in Pelvic Endometriosis

Endometriosis is a significant cause of disability that affects 5-10% of reproductive-aged women. Laparoscopy with histological confirmation is the gold standard in establishing the diagnosis as therapeutic management surgery is addressed to a certain category of patients. The objective of this study was to assess patient adherence to follow-up after surgery for endometriosis as the primary endpoint, pain symptoms, quality of life, mental health, and fertility as the secondary endpoints. We have analyzed patients' adherence to follow-up after surgery for endometriosis after 1, 3, 5, and 7 years. Out of the 2538 total number of surgeries, 453 patients replied just to the first questionnaire (group A), 528 to the first and second (group B), and only 356 carried out the entire follow-up schedule. General health was significantly lower for group A (46.6 vs. 56.4) but with no statistical difference in the post-surgical improvement in both groups. Pain level score improvement was lower for group A (10.5 vs. 18.8), which is statistically significant. In this light, laparoscopy still remains the gold standard in diagnosis only. Furthermore, no malignancy was discovered. The mental component was improved by laparoscopy based on SF-36 in group B. Studies on patient preference for surgery versus alternative treatment are needed.

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.

Coexpression of PD-L1/PD-1 with CXCR3/CD36 and IL-19 Increase in Extranodal Lymphoma

Many studies have demonstrated that PD-L1/PD-1 signaling is an immune evasion mechanism in tumors. PD-L1/PD-1 coexpression with CXCR3/CD36 in peripheral lymphocytes in lymphoma still needs to be clarified. The current study investigated PD-L1/PD-1 coexpression with CXCR3/CD36 in circulating lymphocytes, serum IL-19 levels, and their correlation with clinical outcome and extranodal involvement in lymphoma. Subjects and Methods. The coexpression of PD-L1/PD-1 with CXCR3/CD36 on circulating lymphocytes was analyzed by flow cytometry in 78 lymphoma patients before and after therapy and in 50 healthy controls. The concentration levels of IL-19 in serum were assessed by an ELISA. Results. PD-L1 and PD-1 were expressed on circulating CXCR3+ and CD36+ lymphocytes in lymphoma and were significantly higher in patients with extranodal involvement than in lymphoma patients without extranodal involvement (P < 0.001). Elevated IL-19 levels were observed in lymphoma patients and increased significantly in extranodal involvement (P < 0.001). High percentages of PD-L1+CXCR3+ and PD-1+CXCR3+ lymphocytes were associated with high LDH levels, hepatomegaly, lymphedema, advanced tumor stage, and recurrence. Furthermore, patients with splenomegaly and generalized lymphadenopathy had high percentages of PD-L1+CXCR3+ lymphocytes. In addition, levels of PD-L1/PD-1 coexpression with CXCR3 and IL-19 were significantly associated with bone marrow, lung, and lymph vessel involvement. Further analysis revealed that high percentages of PD-L1+CD36+ and PD-1+CD36+ lymphocytes were associated with lung and bone marrow involvement. Patients with high levels of PD-L1/PD-1 coexpression with CXCR3 and IL-19 had inferior event-free survival (EFS) compared with that in lymphoma patients with low levels. EFS was decreased in patients with high percentages of PD-L1+CD36+ and PD-1+CD36+ lymphocytes. When using the receiver operating characteristic (ROC) curve, the superiority of IL-19 (area under the curve (AUC): 0.993) and PD-L1+CXCR3+% (AUC: 0.961) to PD-1+CXCR3+% (AUC: 0.805), PD-L1+CD36+% (AUC: 0.694), and PD-1+CD36+% (AUC 0.769) was evident in the diagnosis of extranodal involvement, identifying lymphoma patients with extranodal involvement from patients without extranodal involvement. Conclusions. Coexpression of PD-L1/PD-1 with CXCR3/CD36 in circulating lymphocytes and serum IL-19 levels contributes to poor prognosis and might be potential markers for extranodal involvement in lymphoma.

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.

EMAP II Expression Is Increased on Peripheral Blood Cells from Non-Hodgkin Lymphoma

Tumor immune evasion is a lineament of cancer. Endothelial monocyte activating polypeptide-II (EMAP II) has been assumed to impact tumor immune escape significantly. EMAP II was first reported in the murine methylcholanthrene A-induced fibrosarcoma supernatant and identified as a tumor-derived cytokine. This study evaluated EMAP II expression in peripheral blood cells and its association with treatment outcome, lactate dehydrogenase (LDH) levels, and clinical criteria in non-Hodgkin's lymphoma (NHL) patients. EMAP II expression on different blood cells obtained from the peripheral blood of 80 NHL patients was evaluated by two-color flow cytometry. The study reported that EMAP II expression was significantly increased in peripheral blood cells in patients with NHL compared to normal volunteers (P < 0.001). Additionally, EMAP II expression levels on blood cells decreased in complete remission (CR) while they increased in relapse. This study showed coexpression of EMAP II and CD36 on peripheral lymphocytes in NHL patients but not in healthy controls (P < 0.001). EMAP II expression on blood cells was associated with increased serum LDH levels. Furthermore, the percentages of EMAP II+/CD36+ peripheral lymphocytes were significantly higher in relapse than in CR and healthy controls. Analyses revealed that higher percentages of EMAP II+CD36+ cells were positively correlated with hepatomegaly, splenomegaly, and an advanced (intermediate and high risk) NHL stage. The results assume that EMAP II might be involved in NHL development and pathogenesis.

The role of the Immune System in the Development of Endometriosis

Endometriosis is a chronic disease that affects about 10% of women of reproductive age. It can contribute to pelvic pain, infertility or other conditions such as asthma, cardiovascular disease, breast or ovarian cancer. Research has shown that one of the conditions for the development of endometrial lesions is the dysfunction of the immune system. It appears that immune cells, such as neutrophils, macrophages, NK cells and dendritic cells, may play a specific role in the angiogenesis, growth and invasion of endometriosis cells. Immune cells secrete cytokines and defensins that also affect the endometriosis environment. This review discusses the various components of the immune system that are involved in the formation of endometrial lesions in women.

Serum Level of Ligand Programmed Death-1 in Endometriosis

AIM: In this study, is to evaluate serum level of ligand programmed death-1 (PDL1) in patients with genital endometriosis. MATERIAL AND METHODS: For PDL-1, cancer antigen 125 (CA 125), interleukin (IL)-6, IL-8, tumor necrosis factor (TNF), and vascular endothelial growth factor (VEGF) determination, venous blood was taken 1 h before surgery and/or treatment. All patients were stratified by the presence or absence of endometriosis according to the American Society of Reproductive Medicine’s Revised Classification of Endometriosis of the American Society of Reproductive Medicine. RESULTS: Twenty-one patients with endometriosis participated in the study. The PDL-1 level an experienced group was 55.32 ng/ml (interquartile range [IQR] 34.53–76.20); in the control group was 19.72 ng/ml (IQR 14.72–24.78), which was a statistically significant decrease (p < 0.001). A significant increase in CA125 31.87 (IQR 15.43–36.96) was detected (p < 0.001). In the experimental group, all pro-inflammatory cytokines were elevated (IL-6, IL-8, and TNF, p < 0.013; <0.001; and <0.001) and almost twice increased VEGF 243.44 (IQR 194.56–328.07), (p = 0.016). A noticeable correlation was found between the following indicators PDL-1-CA125, PDL-1-IL-8, and PDL-1-TNF, and a moderate correlation was found between PDL-1 and VEFF (p = 0.006). CONCLUSIONS: The results of the study showed that the levels of PDL-1, CA 125, IL-6, IL-8, TNF, and VEGF were statistically significantly different in the experimental and control groups, and a correlation was also revealed between the levels of PDL-1 and CA125, IL-8 and TNF in patients with genital endometriosis. Therefore, further studies with larger numbers of patients are required.

Immunopathogenesis of endometriosis - a novel look at an old problem

This review aims to cast a look at endometriosis as a chronic and progressive gynecological disease.Endometriosis-affected tissues show a variety of pathologic features: alterations in cell growth, apoptosis, activation, angiogenesis, cell adhesion, and cytokine production. Fresh endometriotic lesions are associated with induction of an inflammatory reaction represented by overproduction of prostaglandins (PGE2), metalloproteinases (MMP-2, -3, -9), cytokines (IL-1β, IL-8, IFN-γ, TNF-α, MCP-1 and MIF) and adhesive molecules (ICAM-1, VCAM-1) and activation of synthesis of reactive oxygen and nitrogen species. The inflammatory process may lead to defective folliculogenesis by an altered follicular milieu. An increase in the number and change in function of macrophages, T- and B-lymphocytes and reduction of NK cells have been reported. Treg lymphocytes are known to play an extremely important role in controlling and modulating changes in the aberrant immune response in endometriosis. Dysregulation of the immune system results in both increased progression of endometriosis and its severity. In inflammatory conditions the immune cells provide immune defense at the local level - in peritoneal fluid - and could further cause: 1) a decrease of the number of NK CD16+ cells with expression of KIRs and an increase of NK CD57+; 2) increased numbers of CD8+ cells and CD11b- immature dendritic cells; 3) an increase of FoxP3 expression in the regulatory T cell (Treg) population; 4) an increase of macrophages activating T- and B-lymphocytes leading to elevated synthesis of cytokines and/or autoantibodies. We may conclude that endometriosis resembles an immunodependent disease with the autoimmune background and breakdown of immunosuppressive mechanisms. Further immunological investigations may open a new avenue to discover innovative immunomodulatory treatments of endometriosis.

Infiltrating T lymphocytes and programmed cell death protein-1/programmed death-ligand 1 expression in endometriosis-associated ovarian cancer

OBJECTIVE

To characterize T lymphocyte infiltration and programmed cell death protein-1 (PD-1)/programmed death-ligand 1 (PD-L1) expression in early-stage endometriosis-associated ovarian cancer (EAOC), ovarian endometriosis (OE), atypical endometriosis (AE), and deep endometriosis (DE).

DESIGN

Case-control, retrospective study.

SETTING

Research University Hospital.

PATIENT(S)

A total of 362 patients with a histologic diagnosis of EAOC, OE, AE, or DE were identified between 2000 and 2019 from Fondazione Policlinico Universitario Agostino Gemelli IRCCS and Gemelli Molise SpA tissue data banks. A 1:1 propensity score-matched method yielded matched pairs of 55 subjects with EAOC, 55 patients with OE, 12 patients with AE, and 42 patients with DE, resulting in no differences in family history of cancer, parity, and use of oral contraceptives.

INTERVENTION(S)

Immunohistochemistry assays using the following primary antibodies: CD3+; CD4+; CD8+; PD-1; and PD-L1.

MAIN OUTCOME MEASURE(S)

To characterize T lymphocyte infiltration and PD-1/PD-L1 expression in 4 different endometriosis-related diseases.

RESULT(S)

Endometriosis-associated ovarian cancer cases displayed significantly higher levels of PD-1/PD-L1 expression compared with all other endometriosis-related diseases (vs. OE vs. AE vs. DE). Moreover, a significantly lower count of infiltrating T lymphocytes was observed in EAOC cases compared with OE ones. Finally, one-third of OE cases showed a cancer-like PD-1/PD-L1 expression profile.

CONCLUSION(S)

Endometriosis-associated ovarian cancer is characterized by higher levels of PD-1/PD-L1 expression compared with benign endometriosis-related diseases. This profile was found in one-third of clinically benign cases, suggesting that it develops early in the carcinogenesis process.

Immune checkpoints and reproductive immunology: Pioneers in the future therapy of infertility related Disorders?

As co-stimulatory receptors, immune checkpoint molecules are found on the surface of various immune cells and transduce inhibitory signals following ligand binding. The most studied members in this regard include PD-1, TIM-3, and CTLA-4. The physiological part immune checkpoints possess is the prevention of dangerous immune attacks towards self-antigens throughout an immune response, which takes place through the negative regulation of the effector immune cells, through the induction of T-cell exhaustion, for instance. It has recently been suggested that each checkpoint reduces immunoactivation via distinct intracellular mechanisms of signaling. Regulators of immune checkpoints are supposed to participate actively in immune defense mechanisms against infections, preventing autoimmunity, transplantation, and tumor immune evasion. In pregnancy, as an active immunotolerance mechanism which is also natural, the maternal immune system encounters two simultaneous challenges; in addition to accepting the semi-allogeneic fetus, the maternal immune system should also prevent infections. In this regard, the part immune checkpoint molecules possess is particularly interesting. Herein, the current understanding of such part in reproductive immunology is described.

Endometriosis stromal cells induce bone marrow mesenchymal stem cell differentiation and PD-1 expression through paracrine signaling

Endometriosis is an estrogen-dependent, inflammatory gynecological disorder characterized by the growth of endometrial cells in lesions outside the uterus. Bone marrow-derived cells (BMDCs) engraft lesions and increase lesion size. Do endometriosis cells regulate differentiation of engrafted BMDCs in the pathogenesis and growth of endometriosis? Here, we report endometriosis derived stromal cells promote the differentiation of BMDCs to stromal, epithelial and leukocyte cell fates through paracrine signaling. In-vitro studies demonstrated that both mRNA and protein levels of vimentin, cytokeratin and PD-1 were significantly increased in BMDCs cocultured with stromal cells from endometriosis (ENDO) patients compared to stromal cells from normal endometrium (CNTL). Increased expression of PD-1 has been reported in malignancy where it promotes T cell quiescence and immune tolerance. Increased PD-1 was also confirmed in-vivo where we showed that PD-1 expression was induced in BMDCs engrafted into endometriotic lesions in a murine model of endometriosis. AMD3100, an antagonist for CXCR4 receptor inhibited PD-1 expression in BMDCs suggesting that PD-1 induction requires CXCL12. These results suggest that endometriosis stimulated BMDC differentiation through paracrine signaling and increased T cell PD-1 expression. Increased PD-1 expression may be one mechanism by which endometriosis avoids immune surveillance.

Cancer-associated mutations in endometriosis: shedding light on the pathogenesis and pathophysiology

BACKGROUND

Endometriosis is a benign gynaecological disease. Thus, it came as a complete surprise when it was reported recently that the majority of deep endometriosis lesions harbour somatic mutations and a sizeable portion of them contain known cancer-associated mutations (CAMs). Four more studies have since been published, all demonstrating the existence of CAMs in different subtypes of endometriosis. While the field is still evolving, the confirmation of CAMs has raised many questions that were previously overlooked.

OBJECTIVE AND RATIONALE

A comprehensive overview of CAMs in endometriosis has been produced. In addition, with the recently emerged understanding of the natural history of endometriotic lesions as well as CAMs in normal and apparently healthy tissues, this review attempts to address the following questions: Why has there been such a wild discrepancy in reported mutation frequencies? Why does ectopic endometrium have a higher mutation rate than that of eutopic endometrium? Would the presence of CAMs in endometriotic lesions increase the risk of cancer to the bearers? Why do endometriotic epithelial cells have much higher mutation frequencies than their stromal counterpart? What clinical implications, if any, do the CAMs have for the bearers? Do these CAMs tell us anything about the pathogenesis and/or pathophysiology of endometriosis?

SEARCH METHODS

The PubMed database was searched, from its inception to September 2019, for all papers in English using the term 'endometriosis and CAM', 'endometriosis and cancer-driver mutation', 'somatic mutations', 'fibrosis', 'fibrosis and epigenetic', 'CAMs and tumorigenesis', 'somatic mutation and normal tissues', 'oestrogen receptor and fibrosis', 'oxidative stress and fibrosis', 'ARID1A mutation', and 'Kirsten rat sarcoma mutation and therapeutics'. All retrieved papers were read and, when relevant, incorporated into the review results.

OUTCOMES

Seven papers that identified CAMs in endometriosis using various sequencing methods were retrieved, and their results were somewhat different. Yet, it is apparent that those using microdissection techniques and more accurate sequencing methods found more CAMs, echoing recent discoveries that apparently healthy tissues also harbour CAMs as a result of the replicative aging process. Hence endometriotic lesions, irrespective of subtype, if left intact, would generate CAMs as part of replicative aging, oxidative stress and perhaps other factors yet to be identified and, in some rare cases, develop cancer. The published data still are unable to paint a clear picture on pathogenesis of endometriosis. However, since endometriotic epithelial cells have a higher turnover than their stromal counterpart due to cyclic bleeding, and since the endometriotic stromal component can be formed by refresh influx of mesenchymal cells through epithelial-mesenchymal transition, endothelial-mesenchymal transition, mesothelial-mesenchymal transition and other processes as well as recruitment of bone-marrow-derived stem cells and outflow due to smooth muscle metaplasia, endometriotic epithelial cells have much higher mutation frequencies than their stromal counterpart. The epithelial and stromal cellular components develop in a dependent and co-evolving manner. Genes involved in CAMs are likely to be active players in lesional fibrogenesis, and hyperestrogenism and oxidative stress are likely drivers of both CAMs and fibrogenesis. Finally, endometriotic lesions harbouring CAMs would conceivably be more refractory to medical treatment, due, in no small part, to their high fibrotic content and reduced vascularity and cellularity.

WIDER IMPLICATIONS

The accumulating data on CAMs in endometriosis have shed new light on the pathogenesis and pathophysiology of endometriosis. They also suggest new challenges in management. The distinct yet co-evolving developmental trajectories of endometriotic stroma and epithelium underscore the importance of the lesional microenvironment and ever-changing cellular identity. Mutational profiling of normal endometrium from women of different ages and reproductive history is needed in order to gain a deeper understanding of the pathogenesis. Moreover, one area that has conspicuously received scant attention is the epigenetic landscape of ectopic, eutopic and normal endometrium.

Cellular Origins of Endometriosis: Towards Novel Diagnostics and Therapeutics

Endometriosis remains an enigmatic disease of unknown etiology, with delayed diagnosis and poor therapeutic options. This review will discuss the cellular, physiological, and genomic evidence of Sampson's hypothesis of retrograde menstruation as a cause of pelvic endometriosis and as the basis of phenotypic heterogeneity of the disease. We postulate that collaborative research at the single cell level focused on unlocking the cellular, physiological, and genomic mechanisms of endometriosis will be accompanied by advances in personalized diagnosis and therapies that target unique subtypes of endometriosis disease. These advances will address the clinical conundrums of endometriosis clinical care—including diagnostic delay, suboptimal treatments, disease recurrence, infertility, chronic pelvic pain, and quality of life. There is an urgent need to improve outcomes for women with endometriosis. To achieve this, it is imperative that we understand which cells form the lesions, how they arrive at distant sites, and what factors govern their ability to survive and invade at ectopic locations. This review proposes new research avenues to address these basic questions of endometriosis pathobiology that will lay the foundations for new diagnostic tools and treatment pathways.

CD200 and CD200R Expression on Peripheral Blood Lymphocytes and Serum CD200 Concentration as a New Marker of Endometriosis

The causes of endometriosis (EMS) remain unknown; however, a number of immunological abnormalities contribute to the pathogenesis of the disease. The cluster of differentiation-200 (CD200) and its receptor (CD200R) maintain peripheral self-tolerance by negatively regulating immune responses. In this comparative cross-sectional study, we investigated the expression of CD200 and CD200R on T and B lymphocytes and the serum level of soluble CD200 (sCD200) using flow cytometry and ELISA, respectively. Peripheral blood samples were collected from 54 female patients and 20 healthy, age-matched controls. Results were tested for correlation with disease severity and selected clinical parameters. We demonstrated that the differences in sCD200 levels (p = 0.001), the frequencies of CD200-positive T and B lymphocytes (p < 0.001 and p = 0.004, respectively), and the frequencies of CD200R-positive T and B lymphocytes (p < 0.001 for all comparisons) in the study group correlated positively with disease severity. Receiver operating characteristic (ROC) analysis indicated that aberrant expression of CD200/CD200R might serve as a marker to distinguish between EMS cases. Finally, negative co-stimulatory factors may contribute to the induction and persistence of inflammation associated with EMS. It seems that it is essential to determine whether alteration in the CD200/CD200R pathway can be therapeutically targeted in EMS.

Granzyme B levels and granzyme B polymorphisms in peripheral blood of patients with endometriosis: a preliminary study

The chronic course of endometriosis suggests that the immune system may play a role in its aetiology. There may be resistance to cell lysis, as well as an immune defect underlying endometriosis. Granzyme B is a serine protease that is secreted by Natural Killer (NK) cells and cytotoxic T lymphocytes during a cellular immune response and can induce apoptosis. The aim of this study was to evaluate the relationship between both Granzyme B levels and Granzyme B gene polymorphisms in endometriosis patients. Women between the ages of 20 - 45 were included in the study. The patients were divided into two groups: those diagnosed with endometriosis and those who had not been diagnosed with endometriosis. In the blood samples, Granzyme B gene polymorphisms and serum levels of Granzyme B were studied. There was no difference between the groups in terms of median Granzyme B levels and the presence of AA, AG, and GG genotypes. There was a difference in median granzyme levels for the control group; the GG genotype was found at a lower frequency. The immune defect within endometriosis-related immune cells may not be exclusively due to Granzyme B. Other mediators that are secreted from immune cells may have additive effects.IMPACT STATEMENTWhat is already known on this subject? NK cells are cytotoxic and inhibit the implantation of autologous endometrial cells that are spilled into the peritoneum by retrograde menstruation. Thus, a reduction in NK cell activity may facilitate the progression of endometriosis. The literature review reveals that there are studies suggesting that NK cell activity may be insufficient in endometriosis. Granzyme B is a serine protease that is secreted by NK cells and cytotoxic T lymphocytes during a cellular immune response.What do the results of this study add? Granzyme B is one of the cytotoxic granules in NK and cytotoxic T lymphocyte cells and its genetic polymorphisms were tested in endometriosis. We found that median Granzyme B levels were significantly different in patients with the GG genotype in the control group, compared to those with the AA and AG genotype. However, this difference was not detected between the control and endometriosis groups.What are the implications of these findings for clinical practice and/or further research? Our results contribute to uncovering the pathogenesis of endometriosis since there are no previous studies in the literature regarding this topic. Although we did not find a difference, our results will inform further studies made on this topic. Studies with different molecules and an increased number of patients are needed. The immune defect of endometriosis may not be due exclusively to Granzyme B. Other mediators that are secreted from immune cells may have mutual effects and interactions.

NK Cells as Potential Targets for Immunotherapy in Endometriosis

Endometriosis is a common gynecological disease defined by the presence of endometrial-like tissue outside the uterus, most frequently on the pelvic viscera and ovaries, which is associated with pelvic pains and infertility. It is an inflammatory disorder with some features of autoimmunity. It is accepted that ectopic endometriotic tissue originates from endometrial cells exfoliated during menstruation and disseminating into the peritoneum by retrograde menstrual blood flow. It is assumed that the survival of endometriotic cells in the peritoneal cavity may be partially due to their abrogated elimination by natural killer (NK) cells. The decrease of NK cell cytotoxic activity in endometriosis is associated with an increased expression of some inhibitory NK cell receptors. It may be also related to the expression of human leukocyte antigen G (HLA-G), a ligand for inhibitory leukocyte immunoglobulin-like receptor subfamily B member 1 (LILRB1) receptors. The downregulated cytotoxic activity of NK cells may be due to inhibitory cytokines present in the peritoneal milieu of patients with endometriosis. The role of NK cell receptors and their ligands in endometriosis is also confirmed by genetic association studies. Thus, endometriosis may be a subject of immunotherapy by blocking NK cell negative control checkpoints including inhibitory NK cell receptors. Immunotherapies with genetically modified NK cells also cannot be excluded.

Bibliometric analysis of global research on PD-1 and PD-L1 in the field of cancer

OBJECTIVES

To identify the cooperation of authors, countries, and institutions and explore the hot topics and future prospects regarding programmed cell death protein 1 (PD-1) and programmed cell death 1 ligand 1 (PD-L1) research.

MATERIALS AND METHODS

Publications on PD-1 and PD-L1 research were retrieved from the Web of Science Core Collection. Bibliometric analyses were performed using VOSviewer 1.6.9, HistCite 2.1, and CiteSpace V software. Network maps were generated to evaluate the collaborations between different authors, countries, and institutions.

RESULTS

A total of 7359 articles related to PD-1 and PD-L1 research in the field of cancer were identified. We observed rapid growth in the number of publications since 2014. Oncoimmunology (326, 4.43%) had the highest number of publications, while N Engl J Med (18,828 co-citations, 6.30%) was the most co-cited journal. Hodi FS and Wolchok JD were key researchers. There were active collaborations among the top authors. The USA was the leading contributor in this field with 3496 publications. Active cooperations between countries and between institutions were observed. The main hot topics included matters related to the efficacy and prognosis of various tumors after treatment with PD-1 and/or PD-L1 inhibitors, as well as the activation or expression of important immunological factors targeted at tumors.

CONCLUSION

PD-1 and PD-L1 studies have significantly increased after 2014. The USA contributed the most publications. There were active cooperations between authors, countries, and institutions. Further research should expand and develop new topics such as those likely to boost therapeutic strategies for cancer.