Reciprocal impacts of telomerase activity and ADRN/MES differentiation state in neuroblastoma tumor biology

Abstract

Telomere maintenance and tumor cell differentiation have been separately implicated in neuroblastoma malignancy. Their mechanistic connection is unclear. We analyzed neuroblastoma cell lines and morphologic subclones representing the adrenergic (ADRN) and mesenchymal (MES) differentiation states and uncovered sharp differences in their telomere protein and telomerase activity levels. Pharmacologic conversion of ADRN into MES cells elicited consistent and robust changes in the expression of telomere-related proteins. Conversely, stringent down-regulation of telomerase activity triggers the differentiation of ADRN into MES cells, which was reversible upon telomerase up-regulation. Interestingly, the MES differentiation state is associated with elevated levels of innate immunity factors, including key components of the DNA-sensing pathway. Accordingly, MES but not ADRN cells can mount a robust response to viral infections in vitro. A gene expression signature based on telomere and cell lineage-related factors can cluster neuroblastoma tumor samples into predominantly ADRN or MES-like groups, with distinct clinical outcomes. Our findings establish a strong mechanistic connection between telomere and differentiation and suggest that manipulating telomeres may suppress malignancy not only by limiting the tumor growth potential but also by inducing tumor cell differentiation and altering its immunogenicity.

Connecting telomere maintenance and regulation to the developmental origin and differentiation states of neuroblastoma tumor cells

“…As described in the opening section, another critical determinant of NB malignancy that is dictated by its neural crest origin is tumor cell differentiation. NB displays two major differentiation states that may reflect different stages of neural crest development: undifferentiated MES cells and committed ADRN cells, and these two cell types are interconvertible [ 14 , 17 ]. Ectopic expression of key transcription factors (e.g., NOTCH and PRRX1), associated with the differentiation program, can trigger the conversion between cell types through a feedforward mechanism [ 13 ].…”

“…For examples, ADRN-specific super-enhancers are associated with the expression of adrenergic differentiation makers such as PHOX2A , PHOX2B, and DBH [ 14 ], whereas MES-specific super-enhancers are similar to those found in neural crest-derived cells [ 14 , 16 ]. Consistent with phenotypic plasticity, MES and ADRN cells can trans-differentiate from one cell type into the other [ 14 , 17 ]. Comparison of the earlier morphologic/biochemical and the later genetic classifications revealed broad congruence between cell types from both schemes, with the N/I-type cells resembling the ADRN cells and the S-type cells resembling MES cells [ 9 , 14 , 17 ] (Fig.…”

“…Consistent with phenotypic plasticity, MES and ADRN cells can trans-differentiate from one cell type into the other [ 14 , 17 ]. Comparison of the earlier morphologic/biochemical and the later genetic classifications revealed broad congruence between cell types from both schemes, with the N/I-type cells resembling the ADRN cells and the S-type cells resembling MES cells [ 9 , 14 , 17 ] (Fig. 1 ).…”

“…Notably, studies to date have highlighted tumor cell differentiation and telomere maintenance as two separate determinants of NB disease biology. However, a recent report suggests that these determinants are not independent, but instead mechanistically connected [ 17 ]. In particular, the ADRN and MES cell types were found to exhibit dramatically different levels of telomere-related factors, and inhibition of telomerase triggered the conversion of ADRN into MES cell types in a reversible manner [ 17 ].…”

“…However, a recent report suggests that these determinants are not independent, but instead mechanistically connected [ 17 ]. In particular, the ADRN and MES cell types were found to exhibit dramatically different levels of telomere-related factors, and inhibition of telomerase triggered the conversion of ADRN into MES cell types in a reversible manner [ 17 ]. While unexpected, a potential role of telomeres and telomerase in NB differentiation is plausible in light of multiple studies linking telomere proteins to neural development and neural differentiation.…”