Biomarkers of polycystic kidney disease and uses thereof

A method of determining the efficacy of treatment for polycystic kidney disease (PKD) in a PKD patient, the method comprising:

• (a) providing a first sample comprising urine obtained from the PKD patient at a first time point;
• (b) concentrating the first sample for exosomes;
• (c) determining the level(s) of at least one marker selected from the group consisting of Proliferating Cell Nuclear Antigen (PCNA), cyclin D1, cyclin D3, MAPK-ERK kinase 1 (MEK), and ribosomal protein S6 (S6) in the first sample after step (b);
• (d) administering a glucosyl ceramide synthase (GCS) inhibitor to the PKD patient;
• (e) providing a second sample comprising urine obtained from the PKD patient at a second time point after step (d) and performing steps (b) and (c) on the second sample;
• and
• (f) identifying the administered treatment as being effective if the level of the at least one marker is decreased at the second time point as compared to the first time point.