GRK4 and cancer: In granulosa cell tumors (GCT), lower expression of GRK4α/β was observed in malignant tumors than in nonmalignant tumors, whereas GRK4γ/δ expression was observed in all tumor samples, and GRK4 isoforms may weaken follicle-stimulating hormone receptor uncoupling and desensitization in the pathogenesis of GCT [24].