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Updated: Jul 18, 2026
Induction of Invasive Transitional Cell Bladder Carcinoma in Immune Intact Human MUC1 Transgenic Mice: A Model for Immunotherapy Development
Published on: October 30, 2013
Arsenic-induced bladder cancer in an animal model
Samuel M Cohen1, Takamasa Ohnishi, Lora L Arnold
1Department of Pathology and Microbiology and Eppley Institute for Cancer Research, University of Nebraska Medical Center, Omaha, NE 68198-3135, USA. scohen@unmc.edu
Abstract:
Dimethylarsinic acid (DMA(V)) is carcinogenic to the rat urinary bladder, but not in mice. The carcinogenic mode of action involves cytotoxicity followed by regenerative cell proliferation. Dietary DMA(V) does not produce urinary solids or significant alterations in urinary composition. The cytotoxicity is due to formation of a reactive metabolite, likely dimethylarsinous acid (DMA(III)), concentrated and excreted in the urine. Urinary concentrations of DMA(III) are dose-dependent, and the urinary concentrations are at cytotoxic levels based on in vitro studies. The no observed effect level (NOEL) in these rat dietary studies for detectable levels of DMA(III), cytotoxicity, and proliferation is 2 ppm, with marginal changes at 10 ppm. The tumorigenic dose is 100 ppm. Recent investigations have demonstrated that arsenicals administered to the rat result in binding to a specific cysteine in the hemoglobin alpha chain as DMA(III), regardless of the arsenical being administered. Monomethylarsonic acid (MMA(V)) is not carcinogenic in rats or mice. In short term experiments (< or =10 weeks), sodium arsenate in the drinking water induces significant cytotoxicity and regenerative proliferation. There is little evidence that the cytotoxicity produced following administration of arsenicals is caused by oxidative damage, as antioxidants show little inhibitory activity of the cytotoxicity of the various arsenicals either in vitro or in vivo. In summary, the mode of action for DMA(V)-induced bladder carcinogenesis in the rat involves generation of a reactive metabolite (DMA(III)) leading to cytotoxicity and regenerative proliferation, is a non-linear process, and likely involves a threshold. Extrapolation to human risk needs to take this into account along with the significant differences in toxicokinetics and toxicodynamics that occur between different species.
Insights
Dimethylarsinic acid (DMA(V)) causes rat bladder cancer via a reactive metabolite (DMA(III)) leading to cell damage and regrowth. This non-linear process likely has a threshold, differing from human toxicokinetics.
Area of Science:
- Toxicology
- Carcinogenesis
- Environmental Health
Background:
- Dimethylarsinic acid (DMA(V)) is a known carcinogen in rat urinary bladders, but its mechanism and species-specific effects require clarification.
- Arsenical compounds can induce cytotoxicity and regenerative cell proliferation, key events in carcinogenesis.
- Understanding the metabolic activation and toxicokinetics of DMA(V) is crucial for accurate risk assessment.
Purpose of the Study:
- To elucidate the carcinogenic mode of action of DMA(V) in the rat urinary bladder.
- To identify the reactive metabolite responsible for DMA(V)-induced cytotoxicity.
- To determine the dose-response relationship and identify the no observed effect level (NOEL) for DMA(V) toxicity and carcinogenesis.
Main Methods:
- Dietary administration of DMA(V) to rats and mice at various doses.
- In vitro and in vivo studies to assess cytotoxicity and metabolite formation.
- Analysis of urinary composition, solids, and metabolite concentrations.
- Investigation of potential oxidative damage mechanisms.
Main Results:
- DMA(V) induces rat bladder cancer through cytotoxicity and regenerative proliferation, mediated by a reactive metabolite, likely dimethylarsinous acid (DMA(III)).
- Urinary DMA(III) concentrations are dose-dependent and reach cytotoxic levels, with a NOEL of 2 ppm for DMA(III), cytotoxicity, and proliferation.
- The tumorigenic dose is 100 ppm; DMA(V) is not carcinogenic in mice, and Monomethylarsonic acid (MMA(V)) is not carcinogenic in rats or mice.
- Cytotoxicity is not primarily driven by oxidative damage.
Conclusions:
- The mode of action for DMA(V)-induced bladder carcinogenesis in rats is a non-linear process involving DMA(III)-mediated cytotoxicity and regenerative proliferation, likely with a threshold.
- Significant interspecies differences in toxicokinetics and toxicodynamics necessitate caution when extrapolating rat data to human risk assessment.
