2.3.2. Stratification by *KRT5* or *KRT20* Expression

*KRT5* or *KRT20* mRNA is considered a characteristic feature for a basal or luminal lineage, respectively, in bladder cancer [11]. We utilized the expressions of both mRNA markers as proxies to define a more basal or more luminal-like gene expression pattern, respectively. The expression of both markers was separated by median expression into two groups with low/high *KRT5* (≤36.78 vs. >36.78) or low/high *KRT20* (≤37.47 vs. >37.47) mRNA level. In low and high *KRT20* groups, *CXCL9* mRNA was associated with a shorter RFS (RR = 3.04; *p* = 0.019 and RR = 3.28, respectively; *p* = 0.007) (Table 5). Similarly, low *CXCL9* mRNA was associated with a shorter RFS in the low and high *KRT5* groups (RR = 3.76; *p* = 0.004 and RR = 3.33; *p* = 0.013, respectively; Table 5). These results were expected since they reflected findings for all patients. In the high *KRT5* and high *KRT20* groups, low *PD-L1* mRNA was associated with shorter RFS (RR = 3.68; *p* = 0.012 and RR = 4.23, respectively; *p* = 0.009; Table 5), but this was not so in the low *KRT5* or low *KRT20* group.
