Interestingly, study of CrT gene expression in tumor-infiltrating WT CD8 T cell subsets showed an up-regulation of CrT gene expression that was more significant in the PD-1hi subset than in the PD-1lo subset, suggesting a possible feedback loop in PD-1hi CD8 T cells that compensates for bioenergy insufficiency by increasing creatine uptake (Fig. S1 K). Here, SLC6A8 is linked to neoplasm.