For example, chronic lymphocytic leukemia (CLL) cells have been found to have decreased expression of the cAMP-degrading isozymes that are commonly expressed in lymphocytes under physiological conditions, PDE3B and 4D, with proportional increased expression of PDE7B, a PDE isozyme not expressed in healthy lymphocytes [66]. This evidence concerns the gene PDE7B and B-cell chronic lymphocytic leukemia.