AHCY and cancer: Particularly, neplanocin A (NepA), a naturally occurring cyclopentenyl analog of adenosine with notable antiviral activity, significantly inhibited the proliferation of cancer cells by inhibiting S-adenosylhomocysteine hydrolase (SAH) [28,29,30], an enzyme that catalyzes the hydrolysis of S-adenosylhomocysteine into L-homocysteine and adenosine.