A rare subpopulation of melanoma cells with low expression of metastasis suppressor NME1 is highly metastatic in vivo

Abstract

Despite recent advances in melanoma treatment, metastasis and resistance to therapy remain serious clinical challenges. NME1 is a metastasis suppressor, a class of proteins which inhibits metastatic spread of cancer cells without impact on growth of the primary tumor. We have identified a rare subpopulation of cells with markedly reduced expression of NME1 (NME1 LOW) in human melanoma cell lines. to enable isolation of viable NME1 LOW cells for phenotypic analysis by fluorescence-activated cell sorting (FACS), a CRISPR-Cas9-mediated approach was used to attach an EGFP coding module to the C-terminus of the endogenous NME1 gene in melanoma cell lines. NME1 LOW cells displayed enhanced collective invasion in vitro when implanted as 3D aggregates in Matrigel. NME1 LOW cells were also highly metastatic to lung and liver when xenografted subcutaneously in immune-deficient NSG mice. RNA-seq analysis revealed that NME1 LOW cells express elevated levels of genes associated with tumor aggressiveness, as well as with morphogenesis of tissues of neural crest-like origin (melanocytes and neurons, bone and heart tissues; GO: 0009653). The highly malignant NME1 LOW variant of melanoma cells has potential to provide novel therapeutic targets and molecular markers for improved clinical management of patients with advanced melanoma.

Comprehensive molecular profiling of UV-induced metastatic melanoma in Nme1/Nme2-deficient mice reveals novel markers of survival in human patients

“…NME1 often exhibits reduced expression in melanoma or other cancers but the gene is rarely mutated or deleted, strongly suggesting that transcriptional and/or post-transcriptional mechanisms are at play 10 . Moreover, we previously identified rare cell subpopulations in human melanoma cell lines that exhibit coordinate downregulation of NME1 and NME2 expression, and these cells exhibit elevated metastatic activity 60 . Our HPN melanoma model phenocopies these findings and reveals genomic and transcriptomic changes resulting from Nme1 / Nme2 deficiency that correlate with enhanced lung metastasis.…”

Changes in Biomechanical Properties of A375 Cells Due to the Silencing of TMSB4X Expression Are Not Directly Correlated with Alterations in Their Stemness Features

“…For melanoma cell lines, phenotypic heterogeneity was observed as well. With colleagues [ 83 ], Snyder observed a subpopulation of NME1 low cells within WM9 and WM278 cell lines. NME1 is a metastasis suppressor, and the cells with a lower level of this protein were found to invade collectively better and express higher levels of genes essential for tumor aggressiveness.…”

Nme1 and Nme2 genes exert metastasis-suppressor activities in a genetically engineered mouse model of UV-induced melanoma

“…We recently showed that human melanoma cell lines harbour a rare subpopulation of cells that are profoundly deficient in expression of NME1 and NME2 and exhibit greatly enhanced metastatic activity. 3 By virtue of their complete ablation of Nme1 and Nme2 expression, HPN1 and HPN2 mice are relevant in vivo models for the NME-deficient and highly metastatic subpopulation in human cells. Overall, the robust metastasis-suppressor activities exhibited in the current study by both Nme1 and Nme2 provide novel and compelling in vivo evidence for the individual roles of these genes in malignant progression.…”

“…We recently showed that human melanoma cell lines harbour a rare subpopulation of cells that are profoundly deficient in expression of NME1 and NME2 and exhibit greatly enhanced metastatic activity. 3 By virtue of their complete ablation of Nme1 and Nme2 expression, HPN1 and HPN2 mice are relevant in vivo models for the NME-deficient and highly metastatic subpopulation in human cells.…”

“… 2 In addition, we recently showed that human melanoma cell lines harbour a rare cell subpopulation that exhibits reduced NME1 and NME2 expression, and strong metastatic activity when xenografted in immunocompromised mice. 3 NME1 and NME2 are nucleoside diphosphate kinases, whose activities appear to be effected autonomously and in conjunction with subcellular structures via protein–protein interactions. 4 Disruption of mouse Nme1 confers metastatic potential to chemical-induced hepatocellular carcinoma in vivo, providing evidence of MSG activity in a spontaneously generated cancer.…”