Novel Calcium-Binding Ablating Mutations Induce Constitutive RET Activity and Drive Tumorigenesis

Area of Science:

• Oncology
• Molecular Biology
• Genetics

Background:

• Distinguishing oncogenic mutations from variants of unknown significance (VUS) is critical for precision cancer medicine.
• The RET proto-oncogene is frequently altered in various cancers, but the functional impact of many RET variants remains unclear.

Purpose of the Study:

• To identify novel oncogenic mutations within the RET gene.
• To characterize the functional consequences of RET variants of unknown significance (VUS) located in the calmodulin-like motif (CaLM).
• To explore therapeutic strategies targeting identified oncogenic RET variants.

Main Methods:

• Computational modeling and in silico analysis of 71,756 RET variants.
• Functional assays and molecular dynamics simulations of 110 representative RET variants.
• Assessment of oncogenic and tumorigenic activities of RET mutants.
• Evaluation of therapeutic efficacy of tyrosine kinase inhibitors.

Main Results:

• A cluster of VUSs in the RET CaLM was identified in multiple human cancers.
• CaLM mutations disrupt Ca2+ binding, induce conformational changes, and lead to ligand-independent RET kinase activation via homodimerization.
• RET-CaLM mutants exhibit oncogenic and tumorigenic properties.
• These oncogenic activities can be effectively suppressed by RET-targeting tyrosine kinase inhibitors.

Conclusions:

• Calcium-binding ablating mutations in the RET CaLM represent a novel class of oncogenic mutations.
• In silico annotation of VUSs in druggable oncogenes is a powerful strategy for identifying actionable driver mutations.
• Targeting RET-CaLM mutants with existing tyrosine kinase inhibitors offers a promising therapeutic avenue for cancers harboring these alterations.