Comparative evaluation of three mammalian cell transformation assay systems

Area of Science:

• Toxicology
• Cell Biology
• Genetics

Background:

• Cell transformation assays are crucial for predicting chemical carcinogenicity.
• Standardization and interlaboratory reproducibility are key for assay validation.

Purpose of the Study:

• To assess the intra- and interlaboratory reproducibility of three distinct cell transformation assay systems.
• To establish a basis for objective comparisons between the Syrian hamster embryo (SHE) cellular transformation assay, SHE/Simian adenovirus type 7 (SA7), and Rat/Rauscher leukemia virus (RLV) systems.
• To evaluate the performance of these assays in detecting chemical-induced genetic toxicity.

Main Methods:

• Three transformation assay systems were used: Syrian hamster embryo (SHE) primary cells, SHE infected with Simian adenovirus type 7 (SHE/SA7), and a rat fibroblast cell line (2FR450) infected with Rauscher leukemia virus (Rat/RLV).
• Nine "model" and five coded chemicals were tested across eight collaborating laboratories.
• Each system's endpoint for positive response was defined, and results were analyzed for reproducibility and dose-response relationships.

Main Results:

• All assay systems demonstrated a response to known carcinogens, with qualitative reproducibility observed across laboratories.
• Significant differences were noted in the assays' ability to show dose-related effects.
• Assay performance was inconsistent, often requiring multiple tests or modified procedures for adequate chemical evaluation.

Conclusions:

• Current limitations in scoring, reagent influence, and response reproducibility hinder the routine application of these assays for chemical testing.
• Further research is needed to overcome technical and procedural challenges before these systems can be reliably used for genetic toxicity screening.
• Standardization and refinement are essential for advancing cell transformation assays in toxicological risk assessment.