Immune Modulation in HLA-G Expressing Head and Neck Squamous Cell Carcinoma in Relation to Human Papilloma Virus Positivity: A Study From Northeast India

Abstract

Background: Tumor specific ectopic expression of the immunomodulatory molecule, HLA-G is known to mediate immune tolerance and promote carcinogenesis. Viruses too employ strategies to evade immune surveillance. Considering the role of both HLA-G and HPV in tumor growth and progression, it is pertinent to investigate the relationship between HLA-G and HPV in context of immune modulation in HNSCC. Method: A hospital based case–control study was conducted in histopathologically confirmed HNSCC tissues. HLA-G isoform expression and HPV association studies were carried out and mRNA levels of HLA-G, markers of proliferation and differentiation (ki-67, keratin 18, cyclin D1), immune checkpoint molecules (IL-10, PD-1. TGF-β), SOCS (SOCS1 and SOCS3) and pro-inflammatory cytokine IFN-γ were determined. Results: Higher expression of HLA-G was noted in HPV positive tumors (5.14 fold, p = 0.002). HLA-G7 was the most frequent isoform (29/80) found in HNSCC particularly in HPV positive tumors (13/16). In HPV negative tumors, all the checkpoint molecules were upregulated along with pro–inflammatory IFN-γ. In contrast, in HPV positive tumors, IFN-γ expression was higher (2.12 fold) but levels of IL-10, PD-1, TGF-β, SOCS1 and SOCS3 were markedly lower (fold change of IL-10 = 0.37, PD1 = 0.41, TGF-β = 0.17, SOCS1 = 0.055, SOCS3 = 0.027). HPV positive tumors were more proliferative and differentiated with higher expression of ki-67 and keratin18 (6.25 fold, p = 0.079 and 10.62 fold, p = 0.009). Decreased expression of cyclin D1 was noted in HPV positive tumors (6.94 fold, p = 0.006) than HPV negative tumors (17.69 fold). Also, HLA-G7 expressing HPV positive tumors showed lowest expression of cyclin D1. Interestingly, SOCS showed normal expression in HLA-G7 expressing HPV negative tumors (1.2 and 1.4 fold). IFN-γ was downregulated in HPV positive tumors without HLA-G7 (0.31 fold). Conclusion: Our data suggests that SOCS were downregulated irrespective of HLA-G positivity and IFN- γ expression appeared to be mediated by HLA-G. SOCS are reported to have anti-tumor activity and also SOCS and soluble HLA-G are known to interfere with cell cycle progression. Hence, through regulating HLA-G expression, HPV positive tumors could mediate immune suppression by manipulating SOCS, IFN-γ, IL-10 and cyclin D1 pathways which needs further exploration.

HLA-G: A New Immune Checkpoint in Cancer?

“…KIR2DL4 is expressed by NK cells and a subset of T cells [ 23 , 24 ], and has been shown to induce the inhibition of immune functions of these cells [ 25 , 26 ] as well as activation [ 27 ] upon binding with HLA-G. For instance, a study by Rajagopalan et al reported that soluble HLA-G induced a proinflammatory response via KIR2DL4 in resting NK cells [ 27 ]. The heterogeneous expression patterns of the different isoforms of HLA-G [ 10 , 28 ] and their receptors [ 29 , 30 , 31 ] suggest a fine-tuned network which is closely involved in the regulation of immune interactions. Unfortunately, little is known about the signaling pathways regulating this network.…”

“…Furthermore, RT-qPCR has been used to study HLA-G isoform mRNA expression. For instance, Sarmah et al reported on HLA-G isoform frequency in 35 head and neck squamous cell carcinoma patients [ 28 ]. We did a similar study in CRC and detected mRNA of HLA-G3 in different samples [ 9 ].…”

Serum sHLA-G: Significant diagnostic biomarker with respect to therapy and immunosuppressive mediators in Head and Neck Squamous Cell Carcinoma

“…HLA-G has been also shown to modulate the release of cytokines from peripheral blood mononuclear cells or get modulated by several cytokines such as IL-10 and IFNs 28 . In accordance with this, a study from north-east suggests that IFN-γ expression appeared to be mediated by HLA-G in HNSCC tissues and through regulating HLA-G expression, HPV positive tumors could mediate immune suppression by manipulating SOCS, IFN-γ, IL-10 and cyclin D1 pathways 29 . In view of previous study, we have correlated the proinflammatory (IFN-γ) and anti-inflammatory cytokines (IL-10) with of sHLA-G levels in HNSCC patients.…”

Immune Escape Mechanisms and Their Clinical Relevance in Head and Neck Squamous Cell Carcinoma

“…Next to classical HLA class I antigens, the non-classical HLA-G expression was detected in more than 50% of HNSCC lesions, while healthy controls lacked HLA-G expression [ 51 , 52 , 59 , 60 ]. A higher frequency of HLA-G expression was found in HPV + HNSCC when compared to HPV - HNSCC [ 61 ]. Furthermore, significantly higher HLA-G expression levels were detected in metastases compared to primary tumors [ 62 ].…”