## 3 Results
### Genetic and Clinical Characteristics Associated with GPRC5A  
We conducted a genetic analysis of GPRC5A using data from the TCGA PanCancer Atlas, accessed via the cBioPortal database. Our analysis revealed that GPRC5A exhibited a low frequency of genetic alterations, occurring in only 2.2% of cases (13 out of 592 patients in the cohort) (Figure 2A). The mutations identified included one nonsense mutation, one missense mutation, one case of elevated RNA expression, four gene amplifications, and six cases of reduced RNA expression (Figure 2B). This indicates that GPRC5A is mostly maintained in its wild-type form in GBM.  
We then evaluated the correlation between GPRC5A expression levels and various clinical parameters, including age, gender, and race. Our results indicate that GPRC5A expression was significantly higher in the 40-60 (\(p=0.0037\)) and 60-80 age (\(p=0.0038\)) groups compared to the 20-40 group (Figure 2C). There was no significant difference between the age groups of 40-60 and 60-80. No significant correlation was observed between female and male groups (Figure 2D) or different races (Figure 2E).  
Additionally, we compared GPRC5A expression with key clinical factors, such as G-CIMP (CpG island methylator phenotype) [46] and MGMT promoter methylation status [47]. G-CIMP tumors are associated with a better prognosis due to less aggressive behavior and slower progression. Similarly, MGMT promoter methylation enhances sensitivity to alkylating agents, like temozolomide, by impairing DNA repair. Together, G-CIMP positivity and MGMT methylation are key prognosis features. Our analysis showed that GPRC5A was significantly expressed in the group with non-G-CIMP compared to G-CIMP (\(p<0.0001\)) (Figure 2F), suggesting that GPRC5A is associated with poor prognosis. Regarding MGMT status, there was no significance between the unmethylated and methylated groups (Figure 2G).  
Figure 1: Clinical relevance of GPRC5A in GBM. (**A**) Differential GPRC5A gene expression in normal (N, n = 207, gray) versus LGG (T, n = 518, red) and GBM (T, n = 163, red). Statistical test was performed using one-way ANOVA, * \(p\) < 0.05. (**B**) Kaplan–Meier curve of overall and progression-free survival analysis of high (n = 85, red) and low expression (n = 81, blue) of GPRC5A in GBM cohort. The difference between the two curves was determined by the two-sided log-rank test. (**C**) GPCR5A distribution between wild-type (WT, green) and the main genetic mutations (red) in GBM. Statistical testing was performed using the Wilcoxon test, and the p-value is shown on the graph. (**D**) Differential expression of GPCR5A in different GBM subtypes: classical (n = 42), neural (n = 28), proneural (n = 39), and mesenchymal (n = 55). Statistical testing was performed using unpaired Student’s _t_-tests. *****_p_ < 0.001, NS: non-significant. (**E**) Kaplan–Meier curve of overall and progression-free survival analysis of high (n = 29, red) and low expression (n = 26, blue) of GPRC5A in mesenchymal subtype cohort. The difference between the two curves was determined by the two-sided log-rank test.  
Figure 2: Mutation and clinical landscape of GPRC5A. (**A**) Frequency of GPRC5A genetic alterations in the TCGA pan-cancer dataset. (**B**) Mutation site of GPRC5A with missense at the intron and the nonsense mutation localized at the exon of 7 transmembrane sweet-taste receptor of 3 GCPR (38–268) (7 tm_3). Differential expression of GPRC5A across clinical and molecular variables: (**C**) age (20–40, n = 11; 40–60, n = 63; 60–80, n = 88), (**D**) gender (female, n = 58; male, n = 104), (**E**) race (Asian, n = 5; African-American, n = 11; Hispanic, n = 2; Caucasian, n = 146), (**F**) G-CIMP status (non G-CIMP, n = 147; G-CIMP, n = 15), and (**G**) MGMT methylated (n = 57) versus unmethylated (n = 67) status. Data are expressed as the mean \(\pm\) SD. Statistical comparisons were performed using unpaired Student’s \(t\)-test. **\(p<0.01\), **\(\text{\text{\text{\text{\text{\text{\text{\text{\text{\text{\text{\text{\text{ \text{\