MYO5B mutations in pheochromocytoma/paraganglioma promote cancer progression

Abstract

Identification of additional cancer-associated genes and secondary mutations driving the metastatic progression in pheochromocytoma and paraganglioma (PPGL) is important for subtyping, and may provide optimization of therapeutic regimens. We recently reported novel recurrent nonsynonymous mutations in the MYO5B gene in metastatic PPGL. Here, we explored the functional impact of these MYO5B mutations, and analyzed MYO5B expression in primary PPGL tumor cases in relation to mutation status. Immunohistochemistry and mRNA expression analysis in 30 PPGL tumors revealed an increased MYO5B expression in metastatic compared to non-metastatic cases. In addition, subcellular localization of MYO5B protein was altered from cytoplasmic to membranous in some metastatic tumors, and the strongest and most abnormal expression pattern was observed in a paraganglioma harboring a somatic MYO5B :p.G1611S mutation. In addition to five previously discovered MYO5B mutations, the present study of 30 PPGL (8 previous and 22 new samples) also revealed two, and hence recurrent, mutations in the gene paralog MYO5A . The three MYO5B missense mutations with the highest prediction scores (p.L587P, p.G1611S and p.R1641C) were selected and functionally validated using site directed mutagenesis and stable transfection into human neuroblastoma cells (SK-N-AS) and embryonic kidney cells (HEK293). In vitro analysis showed a significant increased proliferation rate in all three MYO5B mutated clones. The two somatically derived mutations, p.L587P and p.G1611S, were also found to increase the migration rate. Expression analysis of MYO5B mutants compared to wild type clones, demonstrated a significant enrichment of genes involved in migration, proliferation, cell adhesion, glucose metabolism, and cellular homeostasis. Our study validates the functional role of novel MYO5B mutations in proliferation and migration, and suggest the MYO5-pathway to be involved in the malignant progression in some PPGL tumors.

Composite pheochromocytoma/paraganglioma-ganglioneuroma: analysis of SDH and ATRX status, and identification of frequent HRAS and BRAF mutations

“…A review of the English literature indicated a much lower BRAF and HRAS mutation rate in ordinary PCC/PGL and no concomitant mutations were reported ( 4 , 9 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 ). For ordinary GN, it is not usually associated with genetic abnormalities, and only RET gene has been considered to be causative in its pathogenesis ( 22 ).…”

Myosin Motors: Novel Regulators and Therapeutic Targets in Colorectal Cancer

“…These abnormalities reflect disruption of global vesicle trafficking, leading to a loss of the apico-basal cell polarity in epithelial cells with defective MYO5B functions. It is noteworthy that decreased MYO5B expression was observed in gastric cancer [ 129 ], whereas missense mutations of this motor protein were associated with rare neural tumors, pheochromocytoma and paraganglioma [ 130 ]. Functional studies revealed that MYO5B depletion markedly stimulates migration and Matrigel invasion of gastric cancer cells [ 129 ].…”

“…Functional studies revealed that MYO5B depletion markedly stimulates migration and Matrigel invasion of gastric cancer cells [ 129 ]. Furthermore, overexpression of MYO5B mutants, characteristic of neural tumors, accelerates cancer cell migration along with stimulation of cell proliferation [ 130 ]. The reportedly contrasting functional roles of MYO5A and MYO5B in cancer are puzzling, given the high sequence and structural similarity of these motors.…”

What Have We Learned from Molecular Biology of Paragangliomas and Pheochromocytomas?

“…TERT promoter mutations or hypermethylation and structural TERT rearrangement or amplification of TERT locus) confer information on metastatic progression and poor prognosis of patients with Krebs cycle-associated paraganglionic tumours [48]. Moreover, somatic MYO5B mutations leading to deregulated Rab and Rac/Rho GTPase pathways which appear to be preferentially enriched in PPGL-affected patients with metastatic disease and germline SDHB mutations [47,49].…”