NEW YORK – A team from China has used single-cell transcriptome sequencing to identify noradrenergic chromaffin cell-like features in adrenal neuroblastomas — a childhood malignancy suspected of arising from precursor trunk neural crest cells (NCC) that go on to become neuroendocrine chromaffin cells or sympathetic neurons.
"Our findings provide insight into developmental trajectories and cellular states underlying human initiation and progression of [neuroblastoma]," co-senior authors Jia Wang, a researcher with Shanghai Jiao Tong University's State Key Laboratory of Oncogenes and Related Genes, and Kai Li, a pediatric surgery researcher at the Children's Hospital of Fudan University, and their colleagues wrote.
For a paper published in Cancer Cell on Thursday, Wang, Li, and colleagues did single-cell RNA sequencing, copy number profiling, and fluorescence in situ hybridization-based MYCN amplification analyses on almost 161,000 individual cells from 14 neuroblastoma and two ganglioneuroblastoma tumors from the adrenal gland — profiles they set alongside available bulk RNA sequence data for another 106 tumor samples.
They went on to compare the single-cell tumor transcriptomes with those from more than 12,100 individual cells from nine cell types in neuroblastoma-free fetal adrenal gland or human embryo samples, which were included to get a look at the cell type clusters contributing to normal neural crest cell development.
"[W]e anticipate that our single-cell datasets and analysis will serve as a useful resource and be beneficial for future studies to decode the cellular and molecular mechanisms underlying spontaneous [neuroblastoma] regression," the authors reported, "as well as the crucial cell-cell cross talk required for maintaining cellular states in developmental and disease conditions."
Along with chromaffin cell-like features in a subset of malignant cells from the neuroblastomas, the researchers saw signs that the extent of differentiation in these chromaffin-like cells may correspond with adrenal neuroblastoma patient outcomes. For example, they linked undifferentiated or poorly differentiated neuroblastomas to more pronounced tumor proliferation and worse survival outcomes, although the overall transcriptional complexity within the tumors was more muted than anticipated from prior studies.
On the other hand, the team's results suggested that tumors marked by an uptick in more differentiated cells were more prone to regression, and more often turned up in cases with better survival patterns.
"Our findings ... indicate that cellular differentiation within the chromaffin lineage largely determines [neuroblastoma] differentiation grades, which has previously been associated with neuronal differentiation to sympathetic ganglion cells," the authors reported. "Future studies are required to understand whether these chromaffin-cell-associated genes, such as PCP4, can serve as useful biomarkers for improving the precision of clinical evaluation of the [neuroblastoma] differentiation status."
Tumor features appeared to be somewhat distinct in neuroblastomas that contained sub-clones with MYCN amplifications, the researchers noted. A handful of MYCN-amplified tumors in the collection appeared a bit more likely to harbor neural crest cells that have undergone an epithelial-to-mesenchymal transition, rather than the chromaffin-like cell features found in the other samples.
"Notably, MYCN-amplified tumors markedly downregulated the signature of chromaffin cells," the authors wrote, adding that these and other findings from the analyses hint that "MYCN amplification plays an important role in preventing differentiation of chromaffin cells."