VCAN and neoplasm: Under the condition of glycogen metabolism, glycogen accumulated in the tumor is decomposed into glucose-1-phosphate (G1P) by PYGL, then transformed by the enzyme phosphoglucomutase (PGM) into glucose-6-phosphate (G6P), and enter the pentose phosphate pathway (PPP) to produce a large amount of reducing cofactors (NADPH) (16).