Introduction: Gastric cancer (GC) is the 5th most prevalent cancer and is the third leading cause of cancer-related deaths in many regions worldwide. In Iran, it is the fourth most common cancer and the leading cause of cancer mortality. Notably, the incidence and mortality rates of gastric cancer are significantly higher in the northern and northwestern regions of the country compared to other areas. Non-coding RNAs (ncRNAs) play crucial roles in various cellular processes, and their dysregulation has been linked to several cancers, including gastric cancer. Vault RNAs (vtRNAs) are a class of ncRNAs transcribed by RNA polymerase III and associated with a ribonucleoprotein complex known as vault particle. Among the four human vtRNA genes, vtRNA1-1, vtRNA1-2, and vtRNA1-3 are clustered at locus 1 and are integral components of the vault particle, while vtRNA2-1 is a more divergent homologue located at a second locus. Although the functions of vtRNAs are still under investigation, some studies suggest their involvement in various processes such as nucleo-cytoplasmic transport, cellular signaling, DNA damage repair, innate immune response, apoptosis resistance, and nuclear-pore complex formation. The aim of this study was to investigate the expression levels of vtRNA1-3 and vtRNA2-1 in patients with gastric adenocarcinoma and compare them with healthy individuals.
Methods: Blood samples were collected from 50 patients with gastric adenocarcinoma and 50 healthy controls. After RNA extraction, the concentration and purity of total RNAs were determined with an absorption ratio of 280/260, and the accuracy of the extraction was confirmed by gel electrophoresis. The total RNA was reverse-transcribed into cDNA before real-time PCR. The vtRNA1-3 and vtRNA2-1 threshold (Ct) values were normalized to U6 snRNA as housekeeping gene control. Quantitative measurements were performed in triplicate and relative expression was measured using the comparative Ct method (2−ΔΔCt). Statistical data were analyzed using GraphPad Prism (version 9.0.2) and were presented as mean ± standard deviation. The differences were considered significant when the p-value was less than 0.05.
Results: Total RNA was successfully extracted from all samples. The 260/280 nm absorbance ratio of total RNA was 1.8. A single peak was observed in all the dissociation curves in real-time PCR. The qRT-PCR analysis revealed that the relative level of vtRNA2-1 and vtRNA1-3 expression were lower in cases compared to normal. The expression level of vtRNA2-1 significantly decrease in patients (P=0.001), however, the decrease in vtRNA1-3 was not significant (P = 0.087). Moreover, the relationship between the expression level of aforementioned RNAs and the stages of the disease was investigated. There was no significant relationship between vtRNA1-3 expression level and the stage of the disease (0.211), however, the expression level of vtRNA2-1 was found to be related to the progression of the disease (P=0.0001).
Conclusion: In summary, based on the result of this preliminary study, changes in vtRNA2-1 expression may be important in the development and progression of gastric cancer. However, further research is needed to understand the exact functions and significance of vtRNAs in gastric tumorigenesis process.