PTGDS and diffuse large B-cell lymphoma: As the concentration of serum PGD2 in DLBCL patients reached about 0.6 ng/mL, further study showed that PGD2 (0.6 ng/mL) could promote the proliferation of DLBCL cells (Fig. 2B), indicating that serum PGD2 might promote the progression of DLBCL.