Cervical cancer cells suppress effector functions of cytotoxic T cells through the adenosinergic pathway

Adenosinergic Signalling in Cervical Cancer Microenvironment

Despite the emergence of the first human papillomavirus vaccine, the incidence of cervical cancer is still responsible for more than 350,000 deaths yearly. Over the past decade, ecto-5'-nucleotidase (CD73/5'-NT) and extracellular adenosine (ADO) signalling has been the subject of many investigations to target cancer progression. In general, the adenosinergic axis has been linked to tumourigenic effects. However, CD73 can play contradictory effects, probably dependent on the tumour type, tumour microenvironment and tumour stage, thus being in some circumstances, inversely related to tumour progression. We herein reviewed the pathophysiological function of CD73 in cervical cancer and performed in silico analysis of the main components of the adenosinergic signalling in human tissues of cervical cancer compared to non-tumour cervix tissue. Our data showed that the NT5E gene, that encoded CD73, is hypermethylated, leading to a decreased CD73 expression in cervical cancer cells compared to normal cells. Consequently, the high availability of ADO cytoplasmatic/extracellular leads to its conversion to AMP by ADK, culminating in global hypermethylation. Therefore, epigenetic modulation may reveal a new role for CD73 in cervical cancer.

Targeting ENPP1 for cancer immunotherapy: Killing two birds with one stone

Cancer immunotherapy, particularly with immune checkpoint inhibitors, has revolutionized the paradigm of cancer treatment. Nevertheless, the efficacy of cancer immunotherapy remains limited in most clinical settings due to the lack of a preexisting antitumor T-cell response in tumors. Therefore, the clinical outcomes of cancer immunotherapy must be improved crucially. With increased awareness of the importance of the innate immune response in the recruitment of T cells, as well as the onset and maintenance of the T cell response, great interest has been shown in activating the cGAS-STING signaling pathway to awaken the innate immune response, thereby orchestrating both innate and adaptive immune responses to induce tumor clearance. However, tumor cells have evolved to overexpress ectonucleotide pyrophosphate phosphodiesterase 1 (ENPP1), which degrades the immunotransmitter 2',3'-cGAMP and promotes the production of immune-suppressing adenosine, resulting in inhibition of the anticancer immune response in the tumor microenvironment. Clinically, ENPP1 overexpression is closely associated with poor prognosis in patients with cancer. Conversely, depleting or inhibiting ENPP1 has been verified to elevate extracellular 2',3'-cGAMP levels and inhibit the generation of adenosine, thereby reinvigorating the anticancer immune response for tumor elimination. A variety of ENPP1 inhibitors have recently been developed and have demonstrated significant promise for cancer immunotherapy. In this review, we provide an overview of ENPP1, dissect its immunosuppressive mechanisms, and discuss the development of ENPP1 inhibitors with the potential to further improve the efficacy of cancer immunotherapy.

Expression of HPV-16 E6 and E7 oncoproteins alters Chlamydia trachomatis developmental cycle and induces increased levels of immune regulatory molecules

Introduction

Infection with Human Papillomavirus (HPV) is a recognized risk factor for Chlamydia trachomatis (CT) infection and vice versa. Coinfection of HPV and CT in women is a very common and usually asymptomatic finding that has been linked to increased risk of cervical cancer. It has been demonstrated that CT facilitates the entry of multiple high risk HPV genotypes, leading to damage of the mucosal barrier and interfering with immune responses and viral clearance, which ultimately favours viral persistence and malignant transformation. Although the facilitating effects elicited by CT infection on viral persistence have been reported, little is known about the consequences of HPV infection on CT development.

Methods

Herein, we took advantage of a genetically modified human cervical cell line co-expressing HPV-16 major oncogenic proteins E6 and E7, as an experimental model allowing to investigate the possible effects that HPV infection would have on CT development.

Results and discussion

Our results show that CT infection of HPV-16 E6E7 expressing cells induced an upregulation of the expression of E6E7 oncoproteins and host cell inhibitory molecules PD-L1, HVEM and CD160. Additionally, smaller chlamydial inclusions and reduced infectious progeny generation was observed in E6E7 cells. Ultrastructural analysis showed that expression of E6 and E7 did not alter total bacterial counts within inclusions but resulted in increased numbers of reticulate bodies (RB) and decreased production of infectious elementary bodies (EB). Our results indicate that during CT and HPV coinfection, E6 and E7 oncoproteins impair RB to EB transition and infectious progeny generation. On the other hand, higher expression of immune inhibitory molecules and HPV-16 E6E7 are cooperatively enhanced in CT-infected cells, which would favour both oncogenesis and immunosuppression. Our findings pose important implications for clinical management of patients with HPV and CT coinfection, suggesting that screening for the mutual infection could represent an opportunity to intervene and prevent severe reproductive health outcomes, such as cervical cancer and infertility.

Tumor-intrinsic metabolic reprogramming and how it drives resistance to anti-PD-1/PD-L1 treatment

The development of immune checkpoint blockade (ICB) therapies has been instrumental in advancing the field of immunotherapy. Despite the prominence of these treatments, many patients exhibit primary or acquired resistance, rendering them ineffective. For example, anti-programmed cell death protein 1 (anti-PD-1)/anti-programmed cell death ligand 1 (anti-PD-L1) treatments are widely utilized across a range of cancer indications, but the response rate is only 10%-30%. As such, it is necessary for researchers to identify targets and develop drugs that can be used in combination with existing ICB therapies to overcome resistance. The intersection of cancer, metabolism, and the immune system has gained considerable traction in recent years as a way to comprehensively study the mechanisms that drive oncogenesis, immune evasion, and immunotherapy resistance. As a result, new research is continuously emerging in support of targeting metabolic pathways as an adjuvant to ICB to boost patient response and overcome resistance. Due to the plethora of studies in recent years highlighting this notion, this review will integrate the relevant articles that demonstrate how tumor-derived alterations in energy, amino acid, and lipid metabolism dysregulate anti-tumor immune responses and drive resistance to anti-PD-1/PD-L1 therapy.

Inhibition of CD73 expression or A2AR blockade reduces MRP1 expression and increases the sensitivity of cervical cancer cells to cisplatin

Recently, a link between the biological activity of CD73 in solid tumors and multidrug resistance protein (MRP) has been proposed. Cisplatin (CP) is the most widely used anticancer agent to treat advanced and recurrent cervical cancer (CC). However, multidrug resistance protein-1 (MRP1) is overexpressed in approximately 85% of these tumors and has been strongly associated with cisplatin resistance (CPR). In this study, we examine the involvement of CD73 and the interaction of adenosine (ADO) with its receptors (ARs) in MRP1 expression in CC cells. We found that ADO positively modulates MRP1 expression in CC cells in a dose-dependent manner. The inhibition of CD73 expression with a CD73-targeted siRNA and A2AR blockade with the selective antagonist ZM241385 significantly decreased MRP1 expression and the extrusive capacity of CC cells, making them significantly more sensitive to CP treatment than cancer cells treated with MK-751, a specific MRP1 inhibitor. These results suggest CD73 inhibition or blocking ADO signaling through A2AR could be strategies to reverse CPR in patients with advanced or recurrent CC, which is characterized by very low response rates to CP (10%-20%).

Evidence that cervical cancer cells cultured as tumorspheres maintain high CD73 expression and increase their protumor characteristics through TGF-β production

Recently, a link between the biological activity of CD73 and tumorigenicity in solid tumors has been proposed. We previously reported that the generation of adenosine (Ado) by the activity of CD73 in cervical cancer (CC) cells induces transforming growth factor-beta 1 (TGF-β1) production to maintain CD73 expression. In the present study, we analyzed the participation of TGF-β1 in CD73 expression and the development of protumoral characteristics in CaSki CC cells cultured as tumorspheres (CaSki-T) and in monolayers (CaSki-M). Compared with those in CaSki-M cells, CD73 expression and Ado generation ability were significantly increased in CaSki-T cells. CaSki-T cells exhibited enrichment in the CSC-like phenotype due to increases in the expression levels of stem cell markers (CD49f, CK17, and P63; OCT4 and SOX2), greater sphere formation efficiency (SFE), and an increase in the percentage of side population (SP) cells. Interestingly, compared with CaSki-M cells, CaSki-T cells produced a greater amount of TGF-β1 and presented a marked protumor phenotype characterized by a significant decrease in the expression of major histocompatibility complex class-I (MHC-I) molecules, an increase in the expression of multidrug resistance protein-I (MRP-I) and vimentin, and an increase in the protein expression levels of Snail-1 and Twist, which was strongly reversed with TGF-β1 inhibition. These results suggest that the presence of TGF-β1-CD73-Ado feedback loop can promote protumoral characteristics in the CC tumor microenvironment.

Inhibition of adenosine deaminase activity reverses resistance to the cytotoxic effect of high adenosine levels in cervical cancer cells

Adenosine (ADO) generation in the tumor microenvironment (TME) plays important roles in the promotion of tumor growth, invasion, and metastasis and in suppression of the antitumor immune response. Recently, adenosine deaminase (ADA) activity in the TME has been proposed to be a compensatory mechanism against toxic accumulation of ADO in cancerous tissues. In the present study, the expression and functional activity of ADA in cervical cancer (CeCa) tumor cells were analyzed: C33A (HPV-), CaSki (HPV + ), and HeLa (HPV + ) cells. CeCa tumor cells, as well as activated T lymphocytes (ATLs), which were used as a positive control, showed different ADA contents in the membrane and intracellularly and a strong ability to convert ADO into inosine (INO). Treatment of tumor cells with EHNA, a specific ADA inhibitor, decreased the viability of CeCa tumor cells in a dose-dependent manner. In C33A (EHNA half maximal inhibitory concentration (IC₅₀) = 374 μM), CaSki (EHNA IC₅₀ = 273.6 μM), and HeLa (EHNA IC₅₀ = 252.2 μM) cells, EHNA strongly reversed the resistance of tumor cells to the cytotoxic effect of high concentrations of ADO; 38.82 ± 3.1%, 47.18 ± 4.7%, and 71.63 ± 6.9% of the cells were apoptotic, and 40 ± 4.8%, 52 ± 5.3% and 70 ± 6.8% of the cells had mitochondrial membrane damage, respectively. In ATLs (EHNA IC₅₀ = 391.8 μM) treated with EHNA, 32.4 ± 4.4% were apoptotic, and 32 ± 4.3% had mitochondrial membrane damage. These results suggest that the presence and activity of ADA in CeCa tumor cells can provide protection against the cytotoxic effect of high ADO contents in the TME. Therefore, the inhibition of ADA could be a strategy for the treatment of CeCa.

Evidence that the viral oncoproteins E6 and E7 of HPV induce the expression of a functional IL-2R on cervical cancer cells

HPV-positive (HPV+) cervical cancer (CC) cells have been reported to express the IL-2 receptor (IL-2R) in contrast to virus-negative CC cells. This work was carried out to evaluate whether HPV infection induces IL-2R expression in CC cells. The analysis of the IL-2R expression data collected from The Cancer Genome Atlas (TCGA) and Genotype Tissue Expression project (GTEx) using the Xena platform demonstrate a higher expression of IL-2R subunits in CC tumors in comparison with normal tissues. Moreover IL-2Rβ expression is consistently higher in HPV+ tumors versus HPV- tumors. Furthermore, it was demonstrated that transfection of the HPV E6/E7 genes into the C33A (HPV-) cell line promotes IL-2R expression and regulates proliferation in response to exogenous IL-2. Additionally, we found that HPV+ cell lines enhances their proliferation in co-culture with peripheral blood lymphocytes (PBLs). To corroborate that the viral proteins E6 and E7 were related to the effects mediated by IL-2, we used cells derived from the HeLa cell line in which the expression of E6/E7 has decreased, we found that it loses the ability to respond to the exogenous IL-2 stimuli. Finally, the importance of IL-2R in CC, as an immune escape mechanism, is discussed.

Cancer Biology, Epidemiology, and Treatment in the 21st Century: Current Status and Future Challenges From a Biomedical Perspective

Since the second half of the 20th century, our knowledge about the biology of cancer has made extraordinary progress. Today, we understand cancer at the genomic and epigenomic levels, and we have identified the cell that starts neoplastic transformation and characterized the mechanisms for the invasion of other tissues. This knowledge has allowed novel drugs to be designed that act on specific molecular targets, the immune system to be trained and manipulated to increase its efficiency, and ever more effective therapeutic strategies to be developed. Nevertheless, we are still far from winning the war against cancer, and thus biomedical research in oncology must continue to be a global priority. Likewise, there is a need to reduce unequal access to medical services and improve prevention programs, especially in countries with a low human development index.

Detection of CD39 and a Highly Glycosylated Isoform of Soluble CD73 in the Plasma of Patients with Cervical Cancer: Correlation with Disease Progression

Persistent infection with high-risk human papillomavirus (HR-HPV) is the main factor in the development of cervical cancer (CC). The presence of immunosuppressive factors plays an important role in the development of this type of cancer. To determine whether CD39 and CD73, which participate in the production of immunosuppressive adenosine (Ado), are involved in the progression of CC, we compared the concentrations and hydrolytic activity of these ectonucleotidases in platelet-free plasma (PFP) samples between patients with low-grade squamous intraepithelial lesions (LSILs) (n = 18), high-grade squamous intraepithelial lesions (HSILs) (n = 12), and CC (n = 19) and normal donors (NDs) (n = 15). The concentrations of CD39 and CD73 in PFP increased with disease progression (r = 0.5929, p < 0.001). The PFP of patients with HSILs or CC showed the highest concentrations of CD39 (2.3 and 2.2 times that of the NDs, respectively) and CD73 (1.7 and 2.68 times that of the NDs, respectively), which were associated with a high capacity to generate Ado from the hydrolysis of adenosine diphosphate (ADP) and adenosine monophosphate (AMP). The addition of POM-1 and APCP, specific inhibitors of CD39 and CD73, respectively, inhibited the ADPase and AMPase activity of PFP by more than 90%. A high level of the 90 kD isoform of CD73 was detected in the PFP of patients with HSILs or CC. Digestion with endoglycosidase H and N-glycanase generated CD73 with weights of approximately 90 kD, 85 kD, 80 kD, and 70 kD. In addition, the levels of transforming grow factor-β (TGF-β) in the PFPs of patients with LSIL, HSIL and CC positively correlated with those of CD39 (r = 0.4432, p < 0.001) and CD73 (r = 0.5786, p < 0.001). These results suggest that persistent infection by HR-HPV and the concomitant production of TGF-β promote the expression of CD39 and CD73 to favor CC progression through Ado generation.

Adenosine augments the production of IL-10 in cervical cancer cells through interaction with the A2B adenosine receptor, resulting in protection against the activity of cytotoxic T cells

Cervical cancer (CeCa) produces large amounts of IL-10, which downregulates the major histocompatibility complex class I molecules (HLA-I) in cancer cells and inhibits the immune response mediated by cytotoxic T lymphocytes (CTLs). In this study, we analyzed the ability of CeCa cells to produce IL-10 through the CD73-adenosine pathway and its effect on the downregulation of HLA-I molecules to evade CTL-mediated immune recognition. CeCa cells cultured in the presence of ≥10 µM AMP or adenosine produced 4.5-6 times as much IL-10 as unstimulated cells. The silencing of CD73 or the blocking of A2BR with the specific antagonist MRS1754 reversed this effect. In addition, IL-10 decreased the expression of HLA-I molecules, resulting in the protection of CeCa cells against the cytotoxic activity of CTLs. The addition of MRS1754 or anti-IL-10 reversed the decrease in HLA-I molecules and favored the cytotoxic activity of CTLs. These results strongly suggest the presence of a feedback loop encompassing the adenosinergic pathway, the production of IL-10, and the downregulation of HLA-I molecules in CeCa cells that favors immune evasion and thus tumor progression. This pathway may have clinical importance as a therapeutic target.

Comprehensive gene and pathway analysis of cervical cancer progression

Cervical Cancer is one of the leading causes of cancer-associated mortality in women. The present study aimed to identify key genes and pathways involved in cervical cancer (CC) progression, via a comprehensive bioinformatics analysis. The GSE63514 dataset from the Gene Expression Omnibus database was analyzed for hub genes and cancer progression was divided into four phases (phases I-IV). Pathway enrichment, protein-protein interaction (PPI) and pathway crosstalk analyses were performed, to identify key genes and pathways using a criterion nodal degree ≥5. Gene pathway analysis was determined by mapping the key genes into the key pathways. Co-expression between key genes and their effect on overall survival (OS) time was assessed using The Cancer Genome Atlas database. A total of 3,446 differentially expressed genes with 107 hub genes were identified within the four phases. A total of 14 key genes with 11 key pathways were obtained, following extraction of ≥5 degree nodes from the PPI and pathway crosstalk networks. Gene pathway analysis revealed that CDK1 and CCNB1 regulated the cell cycle and were activated in phase I. Notably, the following terms, 'pathways in cancer', 'focal adhesion' and the 'PI3K-Akt signaling pathway' ranked the highest in phases II-IV. Furthermore, FN1, ITGB1 and MMP9 may be associated with metastasis of tumor cells. STAT1 was indicated to predominantly function at the phase IV via cancer-associated signaling pathways, including 'pathways in cancer' and 'Toll-like receptor signaling pathway'. Survival analysis revealed that high ITGB1 and FN1 expression levels resulted in significantly worse OS. CDK1 and CCNB1 were revealed to regulate proliferation and differentiation through the cell cycle and viral tumorigenesis, while FN1 and ITGB1, which may be developed as novel prognostic factors, were co-expressed to induce metastasis via cancer-associated signaling pathways, including PI3K-Art signaling pathway, and focal adhesion in CC; however, the underlying molecular mechanisms require further research.

Purinergic signaling and tumor microenvironment in cervical Cancer

Cervical cancer is the fourth most common type of cancer incidence in the world female population, and it has become a public health problem worldwide. Several factors are involved in this type of cancer, including intrinsic factors related to the inflammatory process, such as extracellular nucleotides and adenosine-components of the purinergic system. The present review focuses on the role of the purinergic system in cervical cancer, especially regarding the interaction of extracellular nucleotides with their respective receptors expressed in the tumor microenvironment of cervical cancer and their role in the host immune response. The high concentrations of extracellular nucleotides in the tumor microenvironment of cervical cancer interfere in the regulation, proliferation, differentiation, and apoptosis of cancer cells of the uterine cervix through different P1 and P2 receptor subtypes. Such diverse cellular processes that are mediated by adenosine triphosphate and adenosine across the tumor microenvironment and that also have effects on host immune defense will be reviewed here in detail.

Adenosine Generated by Regulatory T Cells Induces CD8+ T Cell Exhaustion in Gastric Cancer through A2aR Pathway

BACKGROUND

Adenosine, derived from the degradation of ATP via ectonucleotidases CD39 and CD73, is a critical immunosuppressive metabolite in the hypoxic microenvironment of tumor tissue. Adenosine signaling via A2aR can inhibit the antitumor immune response of CD8+ T cells. CD39 and CD73 high-expressing Tregs play a critical role in tumor immune evasion of gastric cancer (GC). The present study investigated the underlying mechanism by which Tregs suppress antitumor immune responses in GC.

MATERIALS AND METHODS

Fifty-two GC samples were collected, and the frequency of FoxP3+ Tregs and CD8+ T cells and density ratios of A2aR+/CD8+ T cells, CD39+/FoxP3+ Tregs, and CD73+/FoxP3+ Tregs in GC were assessed with multiplex immunofluorescence. The expression of FoxP3 and A2aR in GC tissues was also detected by the immunoblotting assay. We next investigated the relationship between density of FoxP3+ Tregs, ratio of A2aR+/CD8+ T cells, and clinicopathological parameters. At the same time, Tregs and CD8+ T cells were isolated from peripheral blood of five GC patients, and the antagonists of CD39 and CD73 were used to assess the ability of Tregs to decompose ATP into adenosine. In addition, we cocultured CD8+ T cells and Tregs with antagonists of A2aR and A2bR in order to examine the alterations in immune function of CD8+ T cells.

RESULTS

The density of both FoxP3+ Tregs and A2aR+/CD8+ T cells was higher in GC tissue compared to peritumoral normal tissue and significantly correlated with the TNM stage, lymph node metastasis, and distant metastasis of GC. The process of Treg hydrolysis of ATP into adenosine was blocked by the antagonists of CD39 and CD73. In addition, Tregs could induce apoptosis and inhibit proliferation of CD8+ T cells, while this effect could be obviously reduced by applying the antagonist of A2aR or A2aR+A2bR. Moreover, IFN-γ, TNF-α, and perforin generated by CD8+ T cells could also be inhibited through the adenosine A2aR pathway.

CONCLUSIONS

The FoxP3+ Tregs and A2aR+/CD8+ T cells were excessively infiltrated in GC tissue. Tregs from GC can decompose ATP to adenosine and in turn induce apoptosis and inhibit the proliferation of CD8+ T cells through the A2aR pathway, further leading to immune escape of GC.

Decreased local immune response and retained HPV gene expression during chemoradiotherapy are associated with treatment resistance and death from cervical cancer

More than one-third of patients with locally advanced cervical cancer do not respond to chemoradiation therapy (CRT). We aimed to characterize the transcriptional landscape of paired human cervical tumors before and during CRT in order to gain insight into the evolution of treatment response and to elucidate mechanisms of treatment resistance. We prospectively collected cervical tumor biopsies from 115 patients both before and 3 weeks into CRT. RNA-sequencing, Gene Set Enrichment Analysis and HPV gene expression were performed on 20 paired samples that had adequate neoplastic tissue mid-treatment. Tumors from patients with no evidence of disease (NED) at last follow-up had enrichment in pathways related to the immune response both pretreatment and mid-treatment, while tumors from patients dead of disease (DOD) demonstrated enrichment in biosynthetic and mitotic pathways but not in immune-related pathways. Patients DOD had decreased expression of T-cell and cytolytic genes and increased expression of PD-L2 mid-treatment compared to patients NED. Histological and immunohistochemical analysis revealed a decrease in tumor-associated lymphocytes (TAL) during CRT in all patients but tumors from patients DOD had a significantly more pronounced decrease in TALs and CD8+ cells mid-treatment, which was validated in a larger mid-treatment cohort. Finally, patients DOD retained more HPV E6/E7 gene expression during CRT and this was associated with increased expression of genes driving mitosis, which was corroborated in vitro. Our results suggest that decreased local immune response and retained HPV gene expression may be acting together to promote treatment resistance during CRT in patients with cervical cancer.

HPV-16 Infection Is Associated with a High Content of CD39 and CD73 Ectonucleotidases in Cervical Samples from Patients with CIN-1

The development of cervical cancer (CeCa) is associated with high-risk human papilloma virus (HR-HPV) infections, mainly HPV-16, which is present in more than 50% of cases. The presence of immunosuppressive factors in the early stages of the disease is also strongly linked to CeCa progression. In this context, it is unknown whether ectonucleotidases CD39 and CD73, which are involved in the production of adenosine (Ado) that suppresses the specific antitumor immune response, are present in precursor lesions of CeCa. In this pilot study, we analyzed the presence of CD39 and CD73 and their capacity to generate Ado in 25 cervical samples from patients with grade 1 cervical intraepithelial neoplasms (CIN-1) and 25 samples from normal donors (NDs) free of HPV infection. Cells obtained from cervical samples of CIN-1 patients positive for HPV-16 showed higher CD39 and CD73 contents compared to samples obtained from CIN-1 patients negative for HPV-16 and NDs. Interestingly, solubilized cervical mucus from these patients also showed higher contents of soluble CD39 and CD73, which were associated with a greater capacity to produce Ado from the hydrolysis of adenosine triphosphate (ATP) and adenosine monophosphate (AMP). In addition, serum samples of these patients showed higher levels of TGF-β than those of CIN-1 patients negative for HPV-16 and ND. These results suggest that persistent infection with HR-HPV, mostly HPV-16, in CIN-1 patients may promote the expression of CD39 and CD73 through the production of TGF-β in precursor lesions to generate an immunosuppressive microenvironment and allow its progression to CeCa.

Cervical Cancer Cells Express Markers Associated with Immunosurveillance

Cervical cancer is the second most frequent cancer in women in Mexico, and its development depends on the presence of human papillomaviruses in the uterine cervix. These oncogenic viruses transform cells where the control over cell cycle disappears, and the capacity to induce apoptosis is absent. On the other hand, some mutations confer to the transformed cells the ability to evade recognition by the immune system. The expression of markers of the immune system such as CD95, MICA/B, CD39, CD73, NKp30, NKp46, CD44, CD24, NKG2A, and CTLA-4 was analysed by flow cytometry on cervical cancer cells INBL (HPV 18, stage IVB), HeLa (HPV 18), CaSki (HPV 16), and C33A (HPV-). Our results showed the presence of atypical markers on cervical cancer cells; some of them are molecules involved in tumour cell recognition such as MICA/B and CD95. Other markers associated with immune system escape, such as CD39, CD73, and CTLA-4, were also present. Furthermore, we found that some cervical cancer cells expressed typical markers of NK cells like NKp30, NKp46, NKG2A, and KIR3DL1. It is not clear whether these molecules confer any gain to the tumour cells or if they represent a disadvantage, but we hypothesise that these molecules that are present in cervical cancer cells allow them to mimic in front of the immune system.

Cervical cancer cells produce TGF-β1 through the CD73-adenosine pathway and maintain CD73 expression through the autocrine activity of TGF-β1

In cancer, the adenosinergic pathway participates in the generation of an immunosuppressive microenvironment and in the promotion of tumor growth through the generation of adenosine (Ado). The present study analyzed the participation of Ado, generated through the functional activity of the cervical cancer (CeCa) pathway in CeCa cells, to induce the expression and secretion of TGF-β1, as well as the participation of this factor to maintain CD73 expression. Ado concentrations greater than 10 μM were necessary to induce an increase of over 50% in the production and expression of TGF-β1 in CeCa tumor cells. Blockade of A2AR and A2BR with the specific antagonists, ZM241385 and MRS1754, respectively, strongly reversed the production of TGF-β1. TGF-β1 produced by CeCa cells was necessary to maintain CD73 expression because the addition of anti-TGF-β neutralizing antibodies or the inhibition of TGF-βRI strongly reversed the expression of CD73 in the CeCa cells. These results suggested a feedback loop in CeCa cells that favors immunosuppressive activity through the production of TGF-β1 and Ado as well as the autocrine activity of TGF-β1 and expression of CD73.