Prognostic Value of Serum Soluble Klotho and Fibroblast Growth Factor-23 in Multiple Myeloma Patients

Multiple myeloma is the plasma cell malignancy in which bone involvement is common. The Fibroblast growth factor-23 (FGF-23)/Klotho pathway plays a major role in mineral metabolism that FGF-23 is mineralization inhibitory. Klotho also has anti-apoptotic and anti-tumor effects by acting as a tumor suppressor gene. There is a negative correlation between serum FGF-23 and serum soluble Klotho (sKL) levels. As such, there can be considerable interest in investigating sKL and FGF-23 as a biomarker in patients with MM. We used an enzyme-linked immunosorbent assay to measure serum FGF-23 and sKL levels in 55 newly diagnosed MM patients and 23 healthy controls. We determined significantly high serum FGF-23 and low serum sKL levels in MM patients when compared to healthy controls. Serum sKL levels correlated negatively with a p53 positive mutation status, with high ISS, elevated lactate dehydrogenase, C-reactive protein, Beta-2 microglobulin levels. Serum FGF-23 levels are associated negatively with serum phosphorus and positively only light chains and p53 mutation. Patients with high serum FGF-23 levels had significantly shorter median overall survival than those with low serum FGF-23 levels (p = 0.008). Additionally, low sKL levels were related to decreased overall survival, but they didn't reach statistically significant (p = 0.072). There is a significant correlation between low serum sKL, high FGF-23 levels, and known prognostic factors in MM patients. We conclude that low sKL and high FGF-23 levels are a probable prognostic biomarker for poor MM patient outcomes.