N-myc expression switched off and class I human leukocyte antigen expression switched on after somatic cell fusion of neuroblastoma cells

MYCN-targeting vaccines and immunotherapeutics

Amplification and concomitant overexpression of the MYCN oncogene is a frequent event in many malignancies including the childhood tumors, neuroblastoma and medulloblastoma. MYCN is only expressed in a defined time frame during early developmental processes, (1) which is beneficial for approaches combatting tumor-specific MYCN. However, MYCN is a transcription factors that was considered a poor drug target, until recent approaches suggested that down-regulation of MYCN could be possible by indirect targeting using Aurora kinase inhibitors or BET inhibitors. These concepts were proven using preclinical models (2-6) and are now entering clinical trials.

Immune response modulation by Galectin-1 in a transgenic model of neuroblastoma

Galectin-1 (Gal-1) has been described to promote tumor growth by inducing angiogenesis and to contribute to tumor immune escape by promoting apoptosis of activated T cells. We had previously identified upregulation of Gal-1 in preclinical models of aggressive neuroblastoma (NB), a solid tumor of childhood. However, the clinical and biological relevance of Gal-1 in this tumor entity is unclear. Here, the effect of Gal-1 on the immune system and tumorigenesis was assessed using modulation of Gal-1 expression in immune effector cells and in a transgenic NB model, designated TH-MYCN. The fraction of CD4(+) T cells was decreased in tumor-bearing TH-MYCN mice compared to tumor-free littermates, while both CD4(+) T cells as well as CD8(+) T cells were less activated, compatible with a reduced immune response in tumor-bearing mice. Tumor incidence was not significantly altered by decreasing Gal-1/LGALS1 gene dosage in TH-MYCN mice, but TH-MYCN/Gal-1(-/-) double transgenic mice displayed impaired tumor angiogenesis, splenomegaly, and impaired T cell tumor-infiltration with no differences in T cell activation and apoptosis rate. Additionally, a lower migratory capacity of Gal-1 deficient CD4(+) T cells toward tumor cells was observed in vitro. Transplantation of TH-MYCN-derived tumor cells into syngeneic mice resulted in significantly reduced tumor growth and elevated immune cell infiltration when Gal-1 was downregulated by shRNA. We therefore conclude that T cell-derived Gal-1 mediates T cell tumor-infiltration, whereas NB-derived Gal-1 promotes tumor growth. This opposing effect of Gal-1 in NB should be considered in therapeutic targeting strategies, as currently being developed for other tumor entities.

Mutually exclusive expression of a helix-loop-helix gene and N-myc in human neuroblastomas and in normal development

We have isolated a novel human gene encoding a helix-loop-helix (HLH) protein by molecularly cloning chromosome 1p36-specific CpG islands. The gene termed heir-1 was localized to the neuroblastoma consensus deletion at 1p36.2-p36.12. Its predicted protein is 95.8% identical to the mouse HLH462 protein and has clear homology to the mouse Id and Drosophila emc proteins. Heir-1 does not encode a basic DNA binding domain as found in basic HLH proteins. The gene is expressed specifically at high abundance in adult lung, kidney and adrenal medulla, but not in adult brain. Despite prominent heir-1 expression in adrenal medulla, which is a prime target for neuroblastomas, 10 out of 12 neuroblastoma-derived cell lines revealed very low levels of heir-1 mRNA. Low heir-1 expression was generally found in tumor cell lines with N-myc overexpression, whereas the two cell lines displaying high heir-1 levels did not overexpress N-myc. Mutually exclusive expression of both genes was also found by in situ hybridization in developing mouse tissues, particularly in the forebrain neuroectoderm. We conclude that heir-1 expression is reduced specifically in the majority of neuroblastomas and suggest an inverse correlation between heir-1 and N-myc expression in neuroblastoma tumors and in embryonic development.