NF-κB, and not MYCN, Regulates MHC Class I and Endoplasmic Reticulum Aminopeptidases in Human Neuroblastoma Cells

Abstract

Neuroblastoma (NB) is the most common solid extracranial cancer of childhood. Amplification and overexpression of the MYCN oncogene characterize the most aggressive forms and are believed to severely downregulate MHC class I molecules by transcriptional inhibition of the p50 NF-κB subunit. In this study, we found that in human NB cell lines, high MYCN expression is not responsible for low MHC class I expression because neither transfection-mediated overexpression nor small interfering RNA suppression of MYCN affects MHC class I and p50 levels. Furthermore, we identified NF-κB as the immediate upstream regulator of MHC class I because the p65 NF-κB subunit binds MHC class I promoter in chromatin immunoprecipitation experiments, and MHC class I expression is enhanced by p65 transfection and reduced by (a) the chemical NF-κB inhibitor sulfasalazine, (b) a dominant-negative IKBα gene, and (c) p65 silencing. Moreover, we showed that the endoplasmic reticulum aminopeptidases ERAP1 and ERAP2, which generate MHC class I binding peptides, are regulated by NF-κB, contain functional NF-κB-binding elements in their promoters, and mimic MHC class I molecules in the expression pattern. Consistent with these findings, nuclear p65 was detected in NB cells that express MHC class I molecules in human NB specimens. Thus, the coordinated downregulation of MHC class I, ERAP1, and ERAP2 in aggressive NB cells is attributable to a low transcriptional availability of NF-κB, possibly due to an unknown suppressor other than MYCN. Cancer Res; 70(3); 916-24. ©2010 AACR.

Tumor-infiltrating T lymphocytes improve clinical outcome of therapy-resistant neuroblastoma

“…Tumor cells from high-risk neuroblastoma patients express low levels of MHC class I molecules, whereas tumor cells from low-risk neuroblastoma patients express high levels of MHC class I molecules . 16,33,[38][39][40] Tumor cells from high-risk neuroblastoma patients are also known to express low levels of components of the antigen processing machinery [38][39][40] and a limited number of tumor-specific CD8 C T cells. 41 The scarcity of these cells limits their effectiveness.…”

Natural Killer Cells Efficiently Reject Lymphoma Silenced for the Endoplasmic Reticulum Aminopeptidase Associated with Antigen Processing

“…Acetone-fixed tumor sections were stained with specific mAbs and analyzed by confocal microscope. Western blotting, microsomal aminopeptidase activity tests, pulse-chase, and in vitro assembly were performed as described (15,26,27). For further details see Supplementary Materials.…”

Endoplasmic Reticulum Aminopeptidase 2, a common immunological link to adverse pregnancy outcomes and cancer clearance?

“…It is not known exactly when the ERAP gene evolved, and equally uncertain is the functional consequence its evolution has for human pregnancy and cancer immunology. However, ERAP2 protein expression is detected in many tissues, and is induced by type I and type II interferon (IFNs) and tumor necrosis factor-alpha (TNF-α), suggesting that ERAP2 is essential for immune control, and that further investigation is needed to clarify its roles [8, 9]. …”