IMPDH1 and small cell lung carcinoma: For instance, work with small-cell lung cancer (SCLC) models showed that SCLC with elevated MYC expression were more sensitive to the inhibition of the de novo purine biosynthesis enzyme inosine-5′-monophosphate dehydrogenase (IMPDH1/2), which affected rRNA production and thus, cell proliferation [133,134].