Activation of RHOA-VAV1 signaling in angioimmunoblastic T-cell lymphoma

Area of Science:

• Oncology
• Immunology
• Molecular Biology

Background:

• Somatic G17V RHOA mutations are prevalent in angioimmunoblastic T-cell lymphoma (AITL), impacting classical RHOA signaling.
• The precise role of these mutations in AITL pathogenesis remains incompletely understood.

Purpose of the Study:

• To elucidate the novel functions of G17V RHOA mutations in AITL.
• To identify potential therapeutic targets by investigating the molecular mechanisms downstream of G17V RHOA.

Main Methods:

• High-throughput screening to identify G17V RHOA binding partners.
• Phosphorylation assays and Western blotting to analyze VAV1 activation and T-cell receptor (TCR) signaling.
• Analysis of VAV1 mutations and translocations (VAV1-STAP2) in AITL patient samples.
• In vitro studies using dasatinib, a multikinase inhibitor, to assess its effect on signaling pathways.
• Immunohistochemical staining of clinical specimens for phospho-VAV1.

Main Results:

• VAV1 was identified as a specific binding partner for G17V RHOA, augmenting its adaptor function via 174Tyr phosphorylation and accelerating TCR signaling.
• Cytokine and chemokine pathways were enriched in cells expressing G17V RHOA.
• VAV1 mutations and the VAV1-STAP2 translocation were found in RHOA mutation-negative AITL samples, also showing augmented 174Tyr phosphorylation.
• Dasatinib effectively inhibited accelerated VAV1 phosphorylation and TCR signaling induced by both G17V RHOA and VAV1-STAP2.
• Phospho-VAV1 was frequently detected in clinical AITL specimens with G17V RHOA or VAV1 mutations.

Conclusions:

• The G17V RHOA-VAV1 axis represents a novel signaling pathway in AITL pathogenesis.
• This axis, characterized by enhanced VAV1 phosphorylation and TCR signaling, presents a promising therapeutic target.
• Targeting the G17V RHOA-VAV1 interaction with inhibitors like dasatinib may be beneficial for AITL treatment.