Blood diffusion and Th1-suppressive effects of galectin-9–containing exosomes released by Epstein-Barr virus–infected nasopharyngeal carcinoma cells

Abstract

Epstein-Barr virus (EBV)-associated nasopharyngeal carcinoma (NPC)is the third most frequent virus-associated human malignancy. How this tumor escapes immune recognition despite the expression of several viral antigens has remained poorly understood. Our previous in vitro studies have shown that NPC cells release exosomes containing high amounts of galectin-9, a ligand of the membrane receptor Tim-3, which is able to induce apoptosis in mature Th1 lymphocytes.Here, we sought to determine whether galectin-9-carrying exosomes were produced in NPC patients and whether such exosomes might play a role in the immune evasion of NPC cells. We report that galectin-9-containing exosomes are selectively detected in plasma samples from NPC patients and mice xenografted with NPC tumors. The incorporation into exosomes protects galectin-9 against proteolytic cleavage but retains its Tim-3-binding capacity. Importantly, NPC exosomes induce massive apoptosis in EBVspecific CD4 ؉ cells used as a model of target T cells. This effect is inhibited by both anti-Tim-3 and antigalectin-9 blocking antibodies. These results indicate that blocking galectin-9/Tim-3 interaction in vivo might alleviate the Th1-suppressive effect of NPC exosomes and sustain antitumoral T-cell responses and thereby improve clinical efficacy of immunotherapeutic approaches against NPC. (Blood. 2009;113:1957-1966 IntroductionNasopharyngeal carcinoma (NPC) is an Epstein-Barr virus (EBV)-associated malignancy and the third most frequent virus-associated human malignancy after hepatocarcinomas and cervix carcinomas. Each year, approximately 80 000 new cases are diagnosed worldwide. The geographic distribution of NPC is not uniform. It is relatively rare in European and North American countries. Very high incidence foci are found in South China, especially in Guandong and Guangxi provinces (25-40 per 100 000 per year). 1 Areas of intermediate incidence (approximately 3-8 per 100 000 per year) include a large number of developing or emerging countries, especially in North and Central Africa (Tunisia, Algeria, Morocco, Somalia, and Kenya) and in Southeast Asia (Philippines, Vietnam, Indonesia).NPC is an epithelial malignancy with a complex etiology involving viral, environmental, and hereditary factors. Except for some very rare cases of atypical highly differentiated NPC occurring in Western countries, the intact EBV genome is always contained in the nuclei of all malignant cells. 2,3 Many of the approximately 80 EBV genes are silent, but several viral RNAs and proteins are consistently expressed in NPC and contribute to the malignant phenotype. 4 NPC oncogenesis also requires a variable assortment of cellular genetic or epigenetic alterations. 5 Another important biologic feature of NPC is the presence of a massive lymphoid infiltrate in the primary tumor. This infiltrate contains mostly T lymphocytes and a minority of B cells, monocytes, dendritic cells, and eosinophils. The abundant production by malignant NPC cells of inflammatory cytokines, including interle...

Increase of programmed death-1-expressing intratumoral CD8 T cells predicts a poor prognosis for nasopharyngeal carcinoma

“…4,5 Multiple immunosuppressive mechanisms in nasopharyngeal carcinoma have been proposed: interleukin-10, 26 transforming growth factor b1, 27 Fas ligand, 28 regulatory T cells, 29 and galectin-9. 30 As most of these mechanisms converge to inhibit effector T cells, we hypothesized that a marker summarizing the suppressive status of TILs would help identify nasopharyngeal cancer patients with a high risk of treatment failure after standard radiotherapy or chemotherapy. PD-1 is a candidate marker because it is not only a specific receptor that suppresses T cells, but it is also an indicator of the severity of T-cell dysfunction.…”

The inhibition of the T-cell immunoglobulin and mucin domain 3 (Tim3) pathway enhances the efficacy of tumor vaccine

“…The interaction of Tim3 with galectin-9 enhances anti-tumor immunity and prolongs the survival of tumor-bearing mice [21]. Nasopharyngeal tumors secrete exosomes containing galectin-9, which have been implicated in immune escape by the tumor through the induction of tumor-specific Tim3 + T-cell death [22]. Furthermore, Tim3 expressed in lymphoma-associated endothelium leads to tumor progression through the inhibition of CD4 + T-cell activation and Th1 polarization [23].…”

Activation of mitogen activated protein kinase-Erk kinase (MEK) increases T cell immunoglobulin mucin domain-3 (TIM-3) transcription in human T lymphocytes and a human mast cell line

“…TIM-3 expression is inversely correlated with interferon (IFN)-␥ production and proliferation of T cells in chronic hepatitis C (Golden-Mason et al, 2009). TIM-3 interaction with its ligand is suggested as an immune evasion mechanism of Epstein-Barr virus-induced nasopharyngeal carcinoma (Klibi et al, 2009).…”