Contribution of organic cation transporter 2 (OCT2) to cisplatin-induced nephrotoxicity

Abstract

Cisplatin is one of the most widely used anticancer agents for the treatment of solid tumors. The clinical use of cisplatin is associated with dose-limiting nephrotoxicity, which occurs in one-third of patients despite intensive prophylactic measures. Organic cation transporter 2 (OCT2) has been implicated in the cellular uptake of cisplatin, but its role in cisplatin-induced nephrotoxicity remains unknown. In mice, deletion of Oct1 and Oct2 resulted in significantly impaired urinary excretion of cisplatin without an apparent influence on plasma levels. Furthermore, the Oct1/Oct2-deficient mice were protected from severe cisplatin-induced renal tubular damage. Subsequently, we found that a nonsynonymous single-nucleotide polymorphism (SNP) in the OCT2 gene SLC22A2 (rs316019) was associated with reduced cisplatin-induced nephrotoxicity in patients. Collectively, these results indicate the critical importance of OCT2 in the renal handling and related renal toxicity of cisplatin and provide a rationale for the development of new targeted approaches to mitigate this debilitating side effect.

Figure 1

Expression of SLC22A2, normalized to the house keeping gene GAPDH, in (A) human normal tissues and (B) human tumor samples. SLC22A2 was predominantly expressed in kidney and low to absent in tumor samples. Tissue and tumor plates containing cDNA tissues were used for real-time PCR analysis. Data are shown as mean values (symbols) of duplicate plates and expressed relative to values observed in normal human kidney, which was set to a value of 1. Numbers represent tissue from (1) Adrenal gland, (2) Bone marrow, (3) Brain, (4) Cervix, (5) Colon, (6) Descending duodenum, (7) Epididymis, (8) Esophagus, (9) Fat, (10) Heart, (11) Small intestine, (12) Intracranial artery, (13) Kidney, (14) Liver, (15) Lung, (16) Lymph node, (17) Plasma blood leucocyte, (18) Mammary gland, (19) Muscle, (20) Nasal mucosa, (21) Optic nerve, (22) Ovary, (23) Oviduct, (24) Pancreas, (25) Penis, (26) Pericardium, (27) Pituitary, (28) Placenta, (29) Prostate, (30) Rectum, (31) Retina, (32) Seminal vesicles, (33) Skin, (34) Spinal cord, (35) Spleen, (36) Stomach, (37) Testis, (38) Thymus, (39) Thyroid, (40) Tongue, (41) Tonsil, (42) Trachea, (43) Urethra, (44) Urinary bladder, (45) Uterus, (46) Uvula, (47) Vagina, (48) Vena cava.

Figure 2

Urinary platinum excretion and gene expression changes in Oct1(−/−) and Oct2(−/−) mice. (A) Effect of simultaneous Oct1 and Oct2 deficiency on renal handling of cisplatin in mice. The cumulative excretion of cisplatin was reduced in Oct1/2(−/−) mice compared to wildtype mice (n = 11–12/group) after drug administration (10 mg/kg; i.p.). Data are shown as mean values; error bars represent standard error. (B) Differential gene expression in the kidney of male Oct1/2(−/−) mice relative to wildtype FVB mice (n = 3/group) assessed using the Affymetrix Mouse 430v2 GeneChip array. Select genes on the volcano plot include enzymes, nuclear receptors, ABC transporters, and solute carriers. (C) The intracellular uptake of methotrexate (MTX), a positive control, and platinum (Pt) was assessed in HEK293 cells transfected with human OAT3 and mouse Oat3 following incubation of 10 µM or 500 µM methotrexate or 500 µM cisplatin for a period of 30 minutes. Data are expressed relative to drug accumulation in cells transfected with an empty vector, which was set to 100%. Data are shown as mean values with standard error.

Figure 3

Plasma pharmacokinetics in mice after cisplatin treatment. (A) Comparative concentration-time profiles of cisplatin in plasma of Oct1/2(−/−) mice (▼) and wildtype mice (●) (n = 4/group) after the administration of cisplatin (10 mg/kg; i.p.). Data are shown as mean values with standard error along with a curve fit from a 2 compartment model. (B) Comparative concentration-time profiles of unbound platinum in plasma of Oct1/2(−/−) mice (▼) and wildtype mice (●) (n = 4/group) after the administration of cisplatin (10 mg/kg, i.p.). Data are shown as mean values with standard error.

Figure 4

Comparative cisplatin-related nephrotoxicity in (A) untreated wildtype and (B) untreated Oct1/2(−/−) mice with (C) treated wildtype, and (D) treated Oct1/2(−/−) mice 72 hours after the administration of cisplatin (10 mg/kg, i.p.) from representative animals. Severe renal tubular necrosis, characterized by dilated tubules filled with necrotic tubular epithelial cells, was observed in kidneys of all wildtype mice but in none of the Oct1/2(−/−) mice (n = 8/group). Arrows indicate tubules.

Figure 5

Changes in serum creatinine, a marker of acute nephrotoxicity, measured at baseline and after the first cycle of cisplatin treatment in cancer patients as a function of SLC22A2 808G>T genotype (GG; n = 68, GT; n = 10).

Figure 6

(A) Unchanged systemic clearance of unbound cisplatin in cancer patients as a function of SLC22A2 808G>T genotype status (GG; n = 68, GT; n = 10). Each point represents a patient and mean values are indicated by lines. (B) Concentration-time profile of unbound cisplatin as a function of SLC22A2 808G>T genotype status (GG; n = 68, GT; n = 10). Data are shown as mean values ± standard error along with a curve fit from a 2-compartment model (lines).