Functional role of IL-2 receptors on tumour-infiltrating lymphocytes

Immune microenvironment of cervical cancer and the role of IL-2 in tumor promotion

The tumor microenvironment (TME) is a heterogeneous mixture of resident and tumor cells that maintain close communication through their secretion products. The composition of the TME is dynamic and complex among the different types of cancer, where the immune cells play a relevant role in the elimination of tumor cells, however, under certain circumstances they contribute to tumor development. In cervical cancer (CC) the human papilloma virus (HPV) shapes the microenvironment in order to mediate persistent infections that favors transformation and tumor development. Interleukin-2 (IL-2) is an important TME cytokine that induces CD8+ effector T cells and NKs to eliminate tumor cells, however, IL-2 can also suppress the immune response through Treg cells. Recent studies have shown that CC cells express the IL-2 receptor (IL-2R), that are induced to proliferate at low concentrations of exogenous IL-2 through alterations in the JAK/STAT pathway. This review provides an overview of the main immune cells that make up the TME in CC, as well as the participation of IL-2 in the tumor promotion. Finally, it is proposed that the low density of IL-2 produced by immunocompetent cells is used by tumor cells through its IL-2R as a mechanism to proliferate simultaneously depleting this molecule in order to evade immune response.

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.

Serum soluble interleukin 2 receptor alpha in human cancer of adults and children: a review

Cancer growth and development is associated with the stimulation of the innate immune system, including enhanced interleukin 2 receptor (IL-2R) expression in immune cells and its shedding into the circulation in a soluble form of sIL-2Ralpha. In most haematological malignancies, including different types of leukaemias and lymphomas, sIL-2Ralpha has been found to be released directly from the surface of neoplastic cells thus reflecting the tumour bulk, turnover and activity. Several studies have proved that not only lymphoid cancer cells, but also some non-lymphoid cancer cells, express IL-2R on their surface. They include malignant melanoma and carcinomas of the kidney, head and neck, oesophagus and lung. It is suggested that in most malignant solid tumours, elevated levels of sIL-2Ralpha are likely to be the product of normal peripheral mononuclear cells activated in response to the neoplasm's growth or that they are released from activated lymphoid cells infiltrating neoplastic tissues. This latter hypothesis has been proved by discovering the high expression of CD25 on the cell surface of most of these cells. Although the precise source and biological role of sIL-2Ralpha has not been clarified definitively, pretreatment serum levels of sIL-2Ralpha have been shown to reflect the activity, advancement and biological aggressiveness of many types of cancer in adults and children as well as to correlate with prognosis and overall survival. The possibility of enriching the diagnostic tools of oncologists with a new biochemical marker of activity of neoplasms resulted in numerous studies and reports concerning the clinical usefulness of sIL-2Ralpha measurements in adult and, less frequently, in paediatric malignancies. This article presents the actual knowledge concerning the structure, source and biological function of sIL-2Ralpha in patients with haematological and non-haematological malignancies. The authors review the published data on clinical applicability of soluble IL-2Ralpha determination in terms of diagnostics, prognosis and treatment monitoring of particular types of malignant disorders both in adults and in children. They also provide an insight into the clinical usefulness of sLL-2Ralpha-blocking antibodies in patients with cancer, and in those who reject organ transplants, develop graft-versus-host disease after allogeneic bone marrow transplantation and are affected with autoimmune disorders.

Serum level of soluble interleukin-2 receptor alpha correlates with the clinical course and activity of Wilms' tumour and soft tissue sarcomas in children

Wilms' tumour (WT) and soft tissue sarcomas (SA) in children lack reliable biochemical markers. This study was carried out to determine the clinical significance of serum soluble interleukin-2 receptor alpha (sIL-2Ralpha) in the diagnostics and treatment monitoring of children with WT and SA. The study included 48 children: ten with WT, eight with SA and 30 healthy controls. The sIL-2Ralpha levels (ELISA) and rates of elevated sIL-2Ralpha values were estimated prospectively at diagnosis and in complete remission during treatment and after therapy. As the dependence on age was determined, the levels of sIL-2Ralpha were expressed as multiplications of the upper value of the normal range for a particular age ( xN). Median pretreatment levels of sIL-2Ralpha in patients exceeded those of healthy controls (1.79 xN for WT and 1.53 for SA vs. 0.61 for controls; p < 0.001) as did the rates of elevated sIL-2Ralpha values (80% of WTand 87.5% of SA patients vs. 0% of controls). Good response to therapy was paralleled by a significant decline of pretreatment sIL-2Ralpha levels and its elevated rates. Thus, sIL-2Ralpha determination may be of some value in the diagnostics and treatment monitoring of childhood WT and SA.

Serum adhesion molecules and interleukin-2 receptor as markers of tumour load and prognosis in advanced cutaneous melanoma

Cell adhesion molecules are cell surface glycoproteins that may act as mediators in the metastatic process. Soluble interleukin-2 receptor (sIL-2R) is an immunological marker that may also serve as an indicator of tumour progression. Normal and neoplastic cells are capable of releasing these molecules into circulation. We evaluated the association between pretreatment serum levels of soluble intercellular adhesion molecule 1 (sICAM-1), vascular cell adhesion molecule 1 (sVCAM-1) and sIL-2R and metastases and survival in 50 patients with advanced melanoma. The patients with liver and/or bone metastases had significantly higher sICAM-1 levels than those with soft tissue and/or lung involvement (P=0.002). In addition, there was a trend towards higher sIL-2R levels in patients with more metastatic sites (P=0.07). In univariate analysis, the number of metastatic sites (P=0.0001, odds ratio (OR) 3.0, 95% confidence interval (CI): 1.7-5.3), the metastatic site (P=0.01, OR 2.3, 95% CI: 1.2-4.4) and the levels of sICAM-1 (P=0.011, OR 2.5, 95% CI: 1.2-5.0), sVCAM-1 (P=0.036, OR 2.1, 95% CI: 1.0-4.3) and sIL-2R (P=0.0016, OR 3.0, 95% CI: 1.5-6.0) were found to be statistically significant prognostic factors for survival. In multivariate analysis, the number of metastatic sites was the dominant prognostic indicator. After it was excluded from the analysis, the sIL-2R level and the metastatic site were found to be significant. It can be concluded, that high sICAM-1 levels suggest liver metastases and sIL-2R seems to serve as a marker of tumour load in metastatic melanoma. Furthermore, the sIL-2R level appears to add to clinical data predicting the patient's outcome.

Tumour-infiltrating lymphocytes bear the 75 kDa tumour necrosis factor receptor

Tumour necrosis factor alpha (TNF-alpha) is a cytokine with a variety of immunological properties. The identification of two receptors for this molecule, i.e. the 75 kDa and the 55 kDa TNF receptors (TNF-R), recently clarified the mechanisms through which this cytokine provides its wide range of immunomodulatory activities. In this study we have investigated the expression and the functional properties of these receptors on tumour-infiltrating lymphocytes (TILs) recovered from 17 patients with solid cancers (melanoma, colorectal carcinoma and lung cancer). To this end, TIL lines and freshly isolated TILs were evaluated for (a) the expression and the functional role of TNF receptors following culture in the presence of interleukin 2 (IL-2) and (b) the production of TNF-alpha following culture with IL-2 and the role of this cytokine in IL-2-driven TIL proliferation. Flow cytometry analysis demonstrated that TILs bear the 75 kDa TNF-R. Moreover, TIL lines express detectable messages for TNF-alpha and release this cytokine. Functional in vitro studies have shown that anti-TNF-alpha, as well as anti-75 kDa TNF-R antibodies, are able to inhibit the IL-2-induced TIL proliferation. These data demonstrate that TILs are equipped with a fully functional TNF-R system and suggest a putative role for this receptor and its ligand in the activation and expression of TILs following immunotherapy with IL-2.