CCN2 and colorectal carcinoma: Generally, PDE4D was important in CRC metastases, the inhibition of PDE4D led to an increase in cAMP, further inhibiting the protein expression of HIF‐1α, as well as the mRNA and protein levels of CCN2 and the phosphorylation of AKT and ERK, and consequently inhibiting metastasis (Figure 5N).