ABSTRACT
BACKGROUND: The expression of CD73 in tumor cells plays a significant role in the production of adenosine (Ado) that suppresses antitumor effector cells. METHODS: In this study we analyzed the capability of HPV-positive (HPV+) cervical cancer (CeCa) cell lines CaSki, SiHa, HeLa, and RoVa; and HPV-negative (HPV-) cell lines C33A and ViBo to produce Ado and inhibit effector functions of CD8+ T cells. RESULTS: HPV+ CeCa cells expressed significantly higher levels of CD73 in the membrane (p<0.01) than HPV- CeCa cells and this expression was associated with the production of larger amounts of Ado (>400µM) compared to HPV-CeCa cells (<200µM) in the presence of AMP, as well asa stronger inhibition of (>50%) proliferation, activation, and cytotoxic activity of CD8+ T cells via interaction with A2A adenosine receptor. We also provide evidence that silenced E6/E7 expression in CeCa cells, strongly reduced its CD73 expression level and its capability to generate Ado. CONCLUSION: This results suggest that HPV infection, which is associated with more than 99% of CeCa cases, may present an increased constitutive expression of CD73 in cervical neoplasia to contribute to the suppression of the immune response mediated by the production of large amounts of Ado.
Subject(s)
5'-Nucleotidase/metabolism , Adenosine/metabolism , Papillomaviridae/immunology , Papillomavirus Infections/immunology , Receptor, Adenosine A2A/metabolism , T-Lymphocytes, Cytotoxic/immunology , Uterine Cervical Neoplasms/metabolism , Adenosine Monophosphate/metabolism , Cell Line, Tumor , Cytotoxicity, Immunologic , DNA-Binding Proteins/genetics , Female , GPI-Linked Proteins/metabolism , Humans , Immunosuppression Therapy , Oncogene Proteins, Viral/genetics , Papillomavirus E7 Proteins/genetics , RNA, Small Interfering/genetics , Repressor Proteins/genetics , Tumor Escape , Uterine Cervical Neoplasms/immunologyABSTRACT
Cervical cancer (CeCa) tumors are characterized by increased expression of TGF-ß1 and IL-10, which are correlated with downregulated expression of major histocompatibility complex class I antigens (HLA-I) on cancer cells and a reduced immune response mediated by cytotoxic T lymphocytes (CTLs). Mesenchymal stromal cells (MSCs) are important components in the tumor microenvironment that have been suggested to contribute to cancer progression through the induction of TGF-ß1 and IL-10. In this study, we provided evidence that MSCs derived from cervical tumors (CeCa-MSCs) cocultured with CeCa cells induced significant expression of TGF-ß1 and secretion of IL-10 by CeCa cells compared to MSCs derived from the normal cervix (NCx-MSCs) and normal bone marrow (BM-MSCs; gold standard). This increase in expression was associated with a significant downregulation of HLA-I molecules and protection of the cells against specific CTL lysis. Interestingly, the addition of the neutralizing antibody anti-TGF-ß to the CeCa/CeCa-MSCs coculture strongly inhibited the expression and production of IL-10 by CeCa cells. Anti-TGF-ß as well as anti-IL-10 also abolished HLA-I downregulation, and reversed the inhibition of CTL cytotoxicity. These results provide evidence that TGF-ß1 and IL-10 could play an important role in the downregulation of HLA-I molecules on CeCa cells induced by tumor MSCs. Our findings suggest a novel mechanism through which MSCs may protect tumor cells from immune recognition by specific CTLs.
