By inhibiting key enzymes involved in purine synthesis, such as phosphoribosyl pyrophosphate synthetase (PRPS), the purine supply to tumor cells can be disrupted, and their proliferation can be inhibited (17) Certain antimetabolic drugs, like methotrexate, exert their anti-tumor effects in accordance with this principle (17). The gene discussed is MSMB; the disease is neoplasm.