Auranofin-Based Analogues Are Effective against Clear Cell Renal Carcinoma in Vivo and Display No Significant Systemic Toxicity

Effective pharmacological treatments for patients with advanced clear cell renal carcinoma (ccRCC) are limited. Bimetallic titanium-gold containing compounds exhibit significant cytotoxicity against ccRCC in vitro and in vivo and inhibit invasion and angiogenisis in vitro and markers driving these phenomena. However, in vivo preclinical evaluations of such compounds have not examined their pharmacokinetics, pathology, and hematology. Here we use NOD.CB17-Prkdc SCID/J mice bearing xenograft ccRCC Caki-1 tumors to evaluate the in vivo efficacies of two titanium-gold compounds Titanocref and Titanofin (based on auranofin analogue scaffolds) accompanied by pharmacokinetic and pathology studies. A therapeutic trial was performed over 21 days at 5 mg/kg/72h of Titanocref and 10 mg/kg/72h of Titanofin tracking changes in tumor size. We observed a significant reduction of 51% and 60%, respectively (p < 0.01) in tumor size in the Titanocref- and Titanofin-treated mice compared to the starting size, while the vehicle-treated mice exhibited a tumor size increase of 138% (p < 0.01). Importantly, no signs of pathological complication as a result of treatment were found. In addition, Titanocref and Titanofin treatment reduced angiogenesis by 38% and 54%, respectively. Microarray and qRT-PCR analysis of ccRCC Caki-1 cells treated with Titanocref revealed that the compound alters apoptosis, JNK MAP kinase, and ROS pathways within 3 h of treatment. We further show activation of apoptosis by Titanocref and Titanofin in vivo by caspase 3 assay. Titanocref is active against additional kidney cancer cells. Titanocref and Titanofin are therefore promising candidates for further evaluation toward clinical application in the treatment of ccRCC.