NLRC5 regulates expression of MHC-I and provides a target for anti-tumor immunity in transmissible cancers

Abstract

Downregulation of major histocompatibility complex I (MHC-I) on tumor cells is a primary means of immune evasion by many types of cancer. Additionally, MHC-I proteins are a primary target of humoral and cellular mechanisms associated with transplant rejection. Transmissible tumors that overcome allograft rejection mechanisms and evade anti-tumor immunity have killed thousands of wild Tasmanian devils (Sarcophilus harrisii). Interferon-gamma (IFNG) upregulates surface MHC-I expression on devil facial tumor (DFT) cells but is not sufficient to induce tumor regressions. Transcriptome analysis of IFNG-treated DFT cells revealed strong upregulation of NLRC5, a master regulator of MHC-I in humans and mice. To explore the role of NLRC5 in transmissible cancers, we developed DFT cells lines that constitutively overexpress NLRC5. Transcriptomic results suggest that the role of NLRC5 as a master regulator of MHC-I is conserved in devils. Furthermore, NLRC5 was shown to drive the expression of many components of the antigen presentation pathway. To determine if MHC-I is a target of allogeneic immune responses, we tested serum from devils with natural DFT regressions against DFT cells. Antibody binding occurred with cells treated with IFNG and overexpressed NLRC5. However, CRISPR/Cas9-mediated knockout of MHC-I subunit beta-2-microglobulin (B2M) eliminated antibody binding to DFT cells. Consequently, MHC-I could be identified as a target for anti-tumor and allogeneic immunity and provides mechanistic insight into MHC-I expression and antigen presentation in marsupials. NLRC5 could be a promising target for immunotherapy and vaccines to protect devils from transmissible cancers and inform development of transplant and cancer therapies for humans.

Transcriptomic Profiling of Fibropapillomatosis in Green Sea Turtles (Chelonia mydas) From South Texas

“…Studies have shown that NLRC5 is a transcriptional regulator of MHC class I genes ( 66 ) and through this, activates cytotoxic CD8 + T cells as part of an anti-tumor immune response ( 67 ). The increased tumor expression of NLRC5 is associated with better outcomes in human cancer ( 68 ) and is a target of interest in anti-tumor immunity in transmissible tumors of another endangered species; the Tasmanian devil ( 69 ). Furthermore, downregulation of LGR5 in FP (log 2 FoldChange = −4.56, p adj = 1.03 × 10 −9 ) may also demonstrate evidence of an anti-tumor response through regulation of the Wnt/β-catenin signaling pathway, as increased expression of LGR5 is associated with poor prognosis in glioma ( 70 ), breast cancer ( 71 ) and oral squamous cell carcinoma ( 72 ).…”

CIITA induces expression of MHC-I and MHC-II in transmissible cancers

“…Natural and immunotherapy-induced tumour regressions have been observed in devils, along with antibody responses to DFT1 cells, albeit primarily in the context of MHC-I [7][8][9] . Conversely, the emerging DFT2 tumours do express MHC-I 10 , suggesting that other immune evasion mechanisms are important.…”

“…The presence of MHC-II molecules in DFT cells has not been described, although CIITA and some MHC-II transcripts can be upregulated in vitro in DFT1 cells with IFNG treatment 5 . We have previously genetically modified DFT1 and DFT2 cells that overexpress the MHC-I transactivator NLRC5 to induce stable expression of MHC-I on the cell surface 8 . The lack of MHC-II expression in DFT cells provided an opportunity to conduct similar investigations into the role of CIITA in MHC-II regulation in marsupials and transmissible cancers.…”

Transcriptomic profiling of fibropapillomatosis in green sea turtles (Chelonia mydas) from South Texas

“…Studies have shown that NLRC5 is a transcriptional regulator of MHC class I genes 62 and through this, activates cytotoxic CD8 + T cells as part of an anti-tumor immune response 63 . The increased tumor expression of NLRC5 is associated with better outcomes in human cancer 64 and is a target of interest in anti-tumor immunity in transmissible tumors of another endangered species; the Tasmanian devil 65 . Furthermore, downregulation of LGR5 in FP (log2FoldChange = −4.56, padj = 1.03×10 −9 ) may also demonstrate evidence of an anti-tumor response through regulation of the Wnt/β-catenin signaling pathway, as increased expression of LGR5 is associated with poor prognosis in glioma 66 , breast cancer 67 and oral squamous cell carcinoma.…”