Adenosine increases PD-L1 expression in mesenchymal stromal cells derived from cervical cancer through its interaction with A2AR/A2BR and the production of TGF-ß1.

Mesenchymal stromal cells (MSCs) together with malignant cells present in the tumor microenvironment (TME), participate in the suppression of the antitumor immune response through the production of immunosuppressive factors, such as transforming growth factor beta 1 (TGF-ß1). In previous studies, we reported that adenosine (Ado), generated by the adenosinergic activity of cervical cancer (CeCa) cells, induces the production of TGF-ß1 by interacting with A2AR/A2BR. In the present study, we provide evidence that Ado induces the production of TGF-ß1 in MSCs derived from CeCa tumors (CeCa-MSCs) by interacting with both receptors and that TGF-ß1 acts in an autocrine manner to induce the expression of programmed death ligand 1 (PD-L1) in CeCa-MSCs, resulting in an increase in their immunosuppressive capacity on activated CD8+ T lymphocytes. The addition of the antagonists ZM241385 and MRS1754, specific for A2AR and A2BR, respectively, or SB-505124, a selective TGF-ß1 receptor inhibitor, in CeCa-MSC cultures significantly inhibited the expression of PD-L1. Compared with CeCa-MSCs, MSCs derived from normal cervical tissue (NCx-MSCs), used as a control and induced with Ado to express PD-L1, showed a lower response to TGF-ß1 to increase PD-L1 expression. Those results strongly suggest the presence of a feedback mechanism among the adenosinergic pathway, the production of TGF-ß1, and the induction of PD-L1 in CeCa-MSCs to suppress the antitumor response of CD8+ T lymphocytes. The findings of this study suggest that this pathway may have clinical importance as a therapeutic target.

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 cervical cancer cells cultured as tumorspheres maintain high CD73 expression and increase their protumor characteristics through TGF-ß 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-ß1) production to maintain CD73 expression. In the present study, we analyzed the participation of TGF-ß1 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-ß1 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-ß1 inhibition. These results suggest that the presence of TGF-ß1-CD73-Ado feedback loop can promote protumoral characteristics in the CC tumor microenvironment.

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.

Cervical cancer cells produce TGF-ß1 through the CD73-adenosine pathway and maintain CD73 expression through the autocrine activity of TGF-ß1.

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-ß1, 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-ß1 in CeCa tumor cells. Blockade of A2AR and A2BR with the specific antagonists, ZM241385 and MRS1754, respectively, strongly reversed the production of TGF-ß1. TGF-ß1 produced by CeCa cells was necessary to maintain CD73 expression because the addition of anti-TGF-ß neutralizing antibodies or the inhibition of TGF-ßRI 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-ß1 and Ado as well as the autocrine activity of TGF-ß1 and expression of CD73.

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-ß 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-ß in precursor lesions to generate an immunosuppressive microenvironment and allow its progression to CeCa.

Mesenchymal stromal cells derived from cervical cancer produce high amounts of adenosine to suppress cytotoxic T lymphocyte functions.

BACKGROUND: In recent years, immunomodulatory mechanisms of mesenchymal stem/stromal cells (MSCs) from bone marrow and other "classic" sources have been described. However, the phenotypic and functional properties of tumor MSCs are poorly understood. The aim of this study was to analyze the immunosuppressive capacity of cervical cancer-derived MSCs (CeCa-MSCs) on effector T lymphocytes through the purinergic pathway. METHODS: We determined the expression and functional activity of the membrane-associated ectonucleotidases CD39 and CD73 on CeCa-MSCs and normal cervical tissue-derived MSCs (NCx-MSCs). We also analyzed their immunosuppressive capacity to decrease proliferation, activation and effector cytotoxic T (CD8+) lymphocyte function through the generation of adenosine (Ado). RESULTS: We detected that CeCa-MSCs express higher levels of CD39 and CD73 ectonucleotidases in cell membranes compared to NCx-MSCs, and that this feature was associated with the ability to strongly suppress the proliferation, activation and effector functions of cytotoxic T-cells through the generation of large amounts of Ado from the hydrolysis of ATP, ADP and AMP nucleotides. CONCLUSIONS: This study suggests that CeCa-MSCs play an important role in the suppression of the anti-tumor immune response in CeCa through the purinergic pathway.

Adenosine Increases the Immunosuppressive Capacity of Cervical Cancer Cells by Increasing PD-L1 Expression and TGF-ß Production through Its Interaction with A2AR/A2BR.

The present study provides evidence showing that adenosine (Ado) increases the expression of programmed death ligand 1 (PD-L1) in cervical cancer (CeCa) cells by interacting with A2AR/A2BR and that TGF-ß1 acts in an autocrine manner to induce PD-L1 expression, enhancing the immunosuppressive effects of CeCa cells on activated T lymphocytes (ATLs) and CD8+ cytotoxic T lymphocytes (CTLs) specific for antigenic peptides derived from E6 and E7 proteins of HPV-16. Interestingly, the addition of the antagonists ZM241385 and MRS1754, which are specific for A2AR and A2BR, respectively, or SB-505124, which is a selective TGF-ß1 receptor inhibitor, to CeCa cell cultures significantly inhibited PD-L1 expression. In addition, supernatants from CeCa cells that were treated with Ado (CeCa-Ado Sup) increased the expression of PD-1, TGF-ß1, and IL-10 and decreased the expression of IFN-γ in ATLs. Interestingly, the addition of an anti-TGF-ß neutralizing antibody strongly reversed the effect of CeCa-Ado Sup on PD-1 expression in ATLs. These results strongly suggest the presence of a feedback mechanism that involves the adenosinergic pathway, the production of TGF-ß1, and the upregulation of PD-L1 expression in CeCa cells that suppresses the antitumor response of CTLs. The findings of this study suggest that this pathway may be clinically important and may be a therapeutic target.

GLMEEMSAL epitope common in different isoforms of hMena elicits in vitro activation of cytotoxic T cells and stimulates specific antitumor immunity in BALB/c mice.

BACKGROUND: Alternative expression of human ortholog of murine Mena (hMena) hMena/hMena11a and hMena/hMenaΔv6 isoforms regulate the invasiveness and metastatic potential of tumor cells. It is then important to identify epitopes of these proteins that can elicit antitumor immune response to contribute to the elimination of cells with metastatic potential. METHODS: We assayed the capacity of the peptide GLMEEMSAL, common in hMena/hMena11a and hMena/hMenaΔv6 isoforms, to generate an antitumor immune response through an in vitro vaccination system with mature dendritic cells (MDC) loaded with this peptide and in vivo immunization using a tumor model with the mammary adenocarcinoma JC cell line to induce tumors in BALBc mice. RESULTS: MDC loaded with the peptide GLMEEMSAL elicited strong proliferation and activation of CD8+ T lymphocytes. The CTLs generated with this system were capable to lyse specifically BrCa and CeCa cell lines expressing either hMena/hMena11a or hMena/hMenaΔv6. Immunization with GLMEEMSAL provided protective and therapeutic antitumor activity as well as increased survival in BALB/c mice. CONCLUSION: These results are highly relevant for the use of common peptides among the different isoforms of hMena to develop immunotherapy protocols to counteract the growth and metastatic potential of tumors with over-expression of hMena.