PSAT1 and bone metastasis: On analysis of metabolism-related protein expression in the stromal compartment of tumors, the expression of MCT4 (p = 0.002), GLS1 (p = 0.006), GDH (p = 0.035), SDHA (p = 0.004), PHGDH (p = 0.018), PSPH (p = 0.006), PSAT1 (p < 0.001), and SHMT1 (p < 0.001) showed site specificity: higher stromal expression of MCT4, GLS1, GDH, SDHA, PHGDH, and SHMT1 were found in bone metastasis, while PSPH and PSAT1 were higher in brain metastasis (Table 4).