Advanced renal cell carcinoma - The role of orellanine and associated therapeutic challenges

Orellanine is a fungal nephrotoxin selectively toxic to the human tubular epithelial cells (HTEC) of the kidney nephrons leading to kidney failure. Patients treated with renal replacement therapy after orellanine poisoning show no signs of damage to other organs in the body. Aims: Our main aim in this thesis is to develop chronic peritoneal dialysis (PD) in anuric rodents, to better understand the pharmacokinetic properties of orellanine and to evaluate orellanine as an experimental treatment against metastasized clear cell renal cell carcinoma (ccRCC). Methods: The first paper is an in vivo study of chronic automated PD in anuric rats. Orellanine was used to induce uremia. Blood, dialysis fluid, and tissue samples were examined for electrolyte profiles, inflammatory status, and morphology. The second paper is an in vivo study in which rats were given intravenous injections of labeled/unlabeled orellanine. The distribution of orellanine was imaged, and orellanine plasma concentrations were measured over different time points. The third paper had two parts: an in vitro part examining the effect of orellanine on HTEC, epithelial cells, ccRCC cells, and other cancer cell lines, and an in vivo part with a xenograft rat model testing the effect of orellanine on metastasized ccRCC tumors. Results: The levels of urea and creatinine in orellanine-treated rats indicated severe uremia. The automated PD system developed in our lab provided adequate dialysis. The rats gained weight and had normal homeostasis. Orellanine was cleared renally and was mainly distributed to the renal cortex and the urinary bladder. Orellanine induced necrosis, apoptosis, and disruption of cellular functions and growth on HTEC and ccRCC cells while having no significant effect on other tested cell lines at the same doses. Finally, orellanine induced significant apoptosis and necrosis in the xenografted tumors in vivo. Conclusions: Orellanine selectively causes renal failure, which is irreversible at high doses. We describe the first successful treatment of rats with severe uremia that, despite anuria, were kept healthy over a period of at least 21 days. The system can be used to improve PD and to study various aspects of uremia. The pharmacokinetic properties of orellanine were investigated and it was shown that orellanine is distributed mainly to the urinary system. Orellanine induced significant apoptosis and necrosis in metastasized xenografted tumors in vivo and showed no signs of affecting other organs. Therefore, we suggest that its therapeutic effects should be further examined as a treatment option for late stage ccRCC patients

Pharmacokinetic Properties of the Nephrotoxin Orellanine in Rats

Orellanine is a nephrotoxin found in mushrooms of the Cortinarius family. Accidental intake of this substance may cause renal failure. Orellanine is specific for proximal tubular cells and could, therefore, potentially be used as treatment for metastatic renal cancer, which originates from these cells. However, more information is needed about the distribution and elimination of orellanine from the body to understand its potential use for therapy. In this study, 5 mg/kg orellanine (unlabeled and 3H-labeled) was injected intravenously in rats (Wistar and Sprague Dawley). Distribution was measured (Wistar rats, n = 10, n = 12) using radioluminography and the highest amount of orellanine was found in the kidney cortex and bladder at all time-points investigated. The pharmacokinetic properties of orellanine was investigated using LC-MS/MS and β-scintillation to measure the amount of orellanine in plasma. Three groups of rats were investigated: control rats with intact kidneys (n = 10) and two groups with bilateral renal artery ligation (n = 7) where animals in one of these groups were treated with peritoneal dialysis (n = 8). Using LC-MS/MS, the half-life of orellanine was found to be 109 ± 6 min in the controls. In the groups with ligated renal arteries, orellanine had a half-life of 756 ± 98 min without and 238 ± 28 min with dialysis. Thus, orellanine was almost exclusively eliminated by glomerular filtration as well as by peritoneal dialysis

Orellanine specifically targets renal clear cell carcinoma

Renal cell carcinoma (RCC), arising from the proximal tubule in the kidney, accounts for approximately 85% of kidney cancers and causes over 140,000 annual deaths worldwide. In the last decade, several new therapies have been identified for treatment of metastatic RCC. Although these therapies increase survival time compared to standard care, none of them has curative properties. The nephrotoxin orellanine specifically targets proximal tubular epithelial cells, leaving other organs unaffected. We therefore hypothesized that the selective toxicity of orellanine extends to clear cell RCC (ccRCC) cells since they emanate from proximal tubular cells. Orellanine would thus target both primary and metastatic ccRCC in vitro and in vivo. We found that orellanine induces dose-dependent cell death in proximal tubular cells and in all ccRCC cells tested, both primary and cell lines, with no toxicity detected in control cells. The toxic action of orellanine involve decreased protein synthesis, disrupted cell metabolism and induction of apoptosis. In nude rats carrying human ccRCC xenografts, brief orellanine treatment eliminated more than 90% of viable tumor mass compared to control rats. This identifies orellanine as a potential treatment concept for ccRCC patients on dialysis, due to its unique selective toxicity towards ccRCC