# Hypermethylation-mediated silencing of RASD1 drives multiple myeloma pathogenesis

## TL;DR

This study finds that RASD1 is silenced in multiple myeloma due to hypermethylation, linking this to worse outcomes and suggesting RASD1 acts as a tumor suppressor.

## Contribution

The novel contribution is identifying RASD1 as a tumor suppressor silenced by hypermethylation in multiple myeloma.

## Key findings

- RASD1 mRNA and protein are significantly downregulated in multiple myeloma patients.
- RASD1 promoter hypermethylation is associated with adverse clinical features in MM.
- Demethylating agents restore RASD1 expression and increase apoptosis in MM cells.

## Abstract

The role of Ras-related dexamethasone-induced 1 (RASD1) in multiple myeloma (MM) pathogenesis remains unclear. This study investigated the expression profile, clinical significance, and epigenetic regulation of RASD1 in MM.

Bone marrow samples were collected from 26 newly diagnosed patients with MM and 8 healthy controls. RASD1 messenger RNA (mRNA) and protein expression were analyzed using reverse transcription quantitative polymerase chain reaction (RT-qPCR) and immunohistochemistry, respectively. DNA methylation status was assessed via methylation-specific PCR (MSP). The U266 MM cell line was treated with the demethylating agent decitabine (DAC) to evaluate its effects on RASD1 expression and apoptosis.

RASD1 mRNA and protein expression were significantly downregulated in patients with MM compared to healthy controls (P < 0.001). Low RASD1 mRNA levels correlated significantly with advanced DS stage, anemia, hypercalcemia, and elevated M-protein concentrations (P < 0.05). The receiver operating characteristic curve indicated that RASD1 mRNA expression was a robust discriminator between patients with MM and healthy individuals (area under the curve = 0.882, sensitivity = 100%, specificity = 75%). MSP analysis revealed RASD1 promoter hypermethylation in patients with MM, whereas controls exhibited hypomethylation. Treatment of U266 cells with DAC restored RASD1 expression and significantly increased apoptosis compared with controls (12.08% vs. 5.04%, P < 0.01).

RASD1 is frequently silenced in MM through promoter hypermethylation. This epigenetic inactivation is associated with adverse clinical features and enhanced cell survival, supporting a tumor suppressor role for RASD1 in MM pathogenesis.