New Short Term Prediction Method for Chemical Carcinogenicity by Hepatic Transcript Profiling following 28-Day Toxicity Tests in Rats

Mode of action approach supports a lack of carcinogenic potential of six organic UV filters

Ultraviolet (UV) filters, the active ingredients in sunscreens, have been used for several decades to reduce the risk of acute and chronic damage to the skin from solar UV radiation, which can lead to skin cancer. Based on recent clinical studies showing that certain UV filters are absorbed systemically at low levels in humans, the US Food and Drug Administration (FDA) has requested supplementing existing safety data with preclinical studies including oral and dermal 2-year rodent carcinogenicity studies. Although the conduct of 2-year rodent carcinogenicity studies has been the standard approach for evaluating the carcinogenic potential of chemicals and new drugs for approximately 6 decades, there are multiple examples showing that such studies are not predictive of human cancer risk. Given these concerns with 2-year rodent carcinogenicity studies, we have developed and applied an alternative approach for supplementing existing data related to carcinogenic potential for six of the most commonly used UV filters in sunscreen products (i.e. avobenzone, ensulizole, homosalate, octinoxate, octisalate, and octocrylene). This approach evaluates their mode of action (MOA) based on in vivo, in vitro, and in silico data combined with an assessment of exposure margins. This approach is based on the substantial progress in understanding the MOAs that are responsible for tumor induction in humans. It is consistent with those being developed by the International Council for Harmonization (ICH) and other health authorities to replace 2-year carcinogenicity studies given their limitations and questionable biological relevance to humans. The available data for the six UV filters show that they are not genotoxic and show no evidence of biologically relevant carcinogenic MOAs. Furthermore, their systemic exposure levels in humans fall well below concentrations at which they have biologic activity. In conclusion, these data support the continued safe use of these six filters in sunscreen products.

Characteristic molecular signatures of early exposure to volatile organic compounds in rat liver

OBJECTIVE

Investigation on whether the characteristic molecular signatures can discriminate individual volatile organic compounds (VOCs) and provide predictive markers for the detection of VOC exposure.

METHODS

Transcriptomic analysis of liver tissues was performed 48 h after the single oral administration of three VOCs doses at LD25 or LD5 values, to Sprague-Dawley.

RESULTS

Combination analysis of different multi-classifications suggested that 145 genes predicted VOC exposure. Additionally, Gene Set Enrichment Analysis of genes deregulated by VOCs revealed that T cell prolymphatic leukemia signaling was inactivated in all VOCs.

CONCLUSIONS

These molecular markers could be widely implemented to assess and predict environmental exposure to VOCs.