Cancer-Associated Point Mutations in the DLC1 Tumor Suppressor and Other Rho-GAPs Occur Frequently and Are Associated...

Area of Science:

• Oncology
• Molecular Biology
• Genetics

Background:

• The RHOA GTPase is often hyperactive in advanced cancers, correlating with decreased expression of Rho-specific GTPase-accelerating proteins (Rho-GAPs) that normally inhibit RHOA.
• Understanding the role of Rho-GAP mutations in cancer development is crucial for identifying new therapeutic targets.

Purpose of the Study:

• To investigate the frequency of codon mutations in 10 Rho-GAP genes across 12 cancer types using The Cancer Genome Atlas (TCGA) dataset.
• To experimentally determine the biochemical and biological consequences of cancer-associated mutations in the DLC1 tumor suppressor gene.

Main Methods:

• Analysis of TCGA data to identify missense mutations in 10 Rho-GAP genes across 12 tumor types.
• Biochemical assays to assess Rho-GAP activity of DLC1 mutants.
• Cell-based assays to evaluate the impact of DLC1 mutants on cell migration and anchorage-independent growth.

Main Results:

• DLC1 was the most frequently mutated Rho-GAP gene, with 5%-8% of tumors in five cancer types exhibiting DLC1 missense mutations.
• 20%-26% of tumors in four of these cancer types had mutations in at least one of the 10 Rho-GAP genes.
• Seven of nine DLC1 mutants in the Rho-GAP domain showed deficient Rho-GAP activity, suppressed cell migration, and anchorage-independent growth.

Conclusions:

• Point mutations in Rho-GAP genes are unexpectedly common in several cancer types.
• The majority of evaluated cancer-associated DLC1 mutants exhibit reduced tumor-suppressive function through diverse mechanisms, including impaired Rho-GAP activity, altered protein binding (14-3-3, Caveolin-1), and effects on cell migration and growth.