PSPH and hepatocellular carcinoma: This activation of PHGDH increases SSP flux, enabling HCC cells to become more invasive, proliferative, and resistant to oxidative stress and the chemotherapy agent sorafenib.209 Rawat et al.210 demonstrated that phosphoserine phosphatase (PSPH), a crucial enzyme in the serine metabolism pathway, is significantly upregulated in patient-derived melanoma samples.