Aristolactam-DNA adducts are a biomarker of environmental exposure to aristolochic acid

Abstract

Balkan endemic nephropathy is a chronic tubulointerstitial disease frequently accompanied by urothelial cell carcinomas of the upper urinary tract. This disorder has recently been linked to exposure to aristolochic acid, a powerful nephrotoxin and human carcinogen. Following metabolic activation, aristolochic acid reacts with genomic DNA to form aristolactam-DNA adducts that generate a unique TP53 mutational spectrum in urothelium. The aristolactam-DNA adducts are concentrated in the renal cortex, thus serving as biomarkers of internal exposure to aristolochic acid. Here, we present molecular epidemiologic evidence relating carcinomas of the upper urinary tract to dietary exposure to aristolochic acid. DNA was extracted from the renal cortex and urothelial tumor tissue of 67 patients that underwent nephroureterectomy for carcinomas of the upper urinary tract and resided in regions of known endemic nephropathy. Ten patients from non-endemic regions with carcinomas of the upper urinary tract served as controls. Aristolactam-DNA adducts were quantified by 32P-post-labeling, the adduct was confirmed by mass spectroscopy, and TP53 mutations in tumor tissues were identified by chip-sequencing. Adducts were present in 70% of the endemic cohort and in 94% of patients with specific A:T to T:A mutations in TP53. In contrast, neither aristolactam-DNA adducts nor specific mutations were detected in tissues of patients residing in non-endemic regions. Thus, in genetically susceptible individuals, dietary exposure to aristolochic acid is causally related to endemic nephropathy and carcinomas of the upper urinary tract.

Is herbal tea consumption a factor in endemic nephropathy?

“…However, in the past Group A observed A. clematitis more frequently in their fields and among wheat seeds than those from non-endemic villages. This finding is in concordance with our previous results [2,7]. We failed to observe differences in their dietary habits, including baking their own bread from their own wheat (data not shown).…”

“…Nikolić used the same questionnaire for EN patients from different Serbian endemic areas and none reported use of herbal products based on A. clematitis [2]. Therefore, in three countries Our results suggest that farmers from endemic villages do not differ from non-endemic farmers in their herbal tea habits, which might be considered a marker of use of traditional medicine in general.…”

“…Nevertheless, products containing AA remain a part of traditional medicine and are sold in many countries that do not have strict control protocols. Recently we reported that AA DNA adducts were present in 95% of patients with EN who underwent surgery for upper urothelial cancers [2] and affirmed the idea that bread contaminated with AA might be the cause of EN [6,7]. However, the causative relationship between AA and EN again raised the question whether bread intake is the only route of ingestion or whether AA was ingested also in EN as a part of folkloric medicine.…”

“…Gluhovschi et al reported that although therapeutic remedies based on AA products are used in the EN affected area, no relationship between these remedies and the development of EN or of tumors was observed [8]. However, they used HPLC for detection of AA in plasma, which is less sensitive than the mass spectrometry we recently used [1,2]. In addition, when re-analyzing their data, it does appear that AA was used more frequently in the endemic area.…”

“…with upper urothelial cancer exclusively affecting farming villagers [1,2,3]. Based on our results, EN is considered to be an environmental form of aristolochic acid nephropathy (AAN) [1,2.3].…”