Mutation Status of Pleckstrin Homology-Like Domain Family A Member 3 (PHLDA3) in the Radiation-Induced Insulinoma...

Background Pleckstrin homology-like domain family A member 3 (PHLDA3) has emerged as an important tumor suppressor gene, particularly in pancreatic neuroendocrine tumors (PanNETs), such as insulinomas. PHLDA3 is also known to function as a p53-inducible tumor suppressor and plays a critical role in regulating Akt signaling and apoptosis. It is also recognized as a key component of a radiation-responsive gene signature, highlighting its potential as a biomarker for radiation exposure. Previous studies have shown that PHLDA3 mRNA is upregulated in irradiated mouse hematopoietic cells by quantitative RT-PCR. The RIN-5F cell line, a rat islet β-cell line derived from a radiation-induced insulinoma, is widely used in diabetes and endocrinology research. However, PHLDA3 mutations have not previously been investigated in radiation-induced insulinoma cell lines, even though ionizing radiation is known to cause genetic abnormalities. Methodology A putative p53-responsive element (p53RE) overlapping the transcription initiation site of the PHLDA3 gene has been identified. Because rat PHLDA3 is a single-exon gene, it lacks intronic regions. This study examined the DNA mutation status of the single exon and the putative p53RE of the PHLDA3 gene in the RIN-5F insulinoma cell line to determine whether radiation exposure induces mutations in PHLDA3. Results No mutations were detected in either the single exon or the putative p53RE of the PHLDA3 gene in this cell line. Conclusions The study was designed as an initial exploratory analysis specifically focused on insulinoma, which has been reported to exhibit altered PHLDA3 expression. Therefore, establishing whether genomic alterations exist in RIN-5F, one of the insulinoma cell lines, was a necessary first step. These findings suggest that radiation may promote the transformation of islet β-cells into insulinoma cells through mechanisms that do not involve direct mutations in the PHLDA3 gene. This highlights the complexity of radiation-associated cellular transformation and suggests that factors other than PHLDA3 mutational inactivation, such as epigenetic regulation or transcriptional changes, may contribute to islet β-cell oncogenesis.