Related Experiment Video
Updated: Jun 23, 2026
Magnetic Resonance Imaging Assessment of Carcinogen-induced Murine Bladder Tumors
Published on: March 29, 2019
Evidence for toxicity differences between inorganic arsenite and thioarsenicals in human bladder cancer cells
Hua Naranmandura1, Yasumitsu Ogra, Katsuya Iwata
1Analytical and Environmental Toxicology, Department of Laboratory Medicine and Pathology, University of Alberta, Edmonton, Alberta, Canada.
Abstract:
Arsenic toxicity is dependent on its chemical species. In humans, the bladder is one of the primary target organs for arsenic-induced carcinogenicity. However, little is known about the mechanisms underlying arsenic-induced carcinogenicity, and what arsenic species are responsible for this carcinogenicity. The present study aimed at comparing the toxic effect of DMMTA(V) with that of inorganic arsenite (iAs(III)) on cell viability, uptake efficiency and production of reactive oxygen species (ROS) toward human bladder cancer EJ-1 cells. The results were compared with those of a previous study using human epidermoid carcinoma A431 cells. Although iAs(III) was known to be toxic to most cells, here we show that iAs(III) (LC(50)=112 microM) was much less cytotoxic than DMMTA(V) (LC(50)=16.7 microM) in human bladder EJ-1 cells. Interestingly, pentavalent sulfur-containing DMMTA(V) generated a high level of intracellular ROS in EJ-1 cells. However, this was not observed in the cells exposed to trivalent inorganic iAs(III) at their respective LC(50) dose. Furthermore, the presence of N-acetyl-cysteine completely inhibited the cytotoxicity of DMMTA(V) but not iAs(III), suggesting that production of ROS was the main cause of cell death from exposure to DMMTA(V), but not iAs(III). Because the cellular uptake of iAs(III) is mediated by aquaporin proteins, and because the resistance of cells to arsenite can be influenced by lower arsenic uptake due to lower expression of aquaporin proteins (AQP 3, 7 and 9), the expression of several members of the aquaporin family was also examined. In human bladder EJ-1 cells, mRNA/proteins of AQP3, 7 and 9 were not detected by reverse transcription polymerase chain reaction (RT-PCR)/western blotting. In A431 cells, only mRNA and protein of AQP3 were detected. The large difference in toxicity between the two cell lines could be related to their differences in uptake of arsenic species.
Insights
Dimethylmonothiocarbamate arsenic (DMMTA(V)) is more toxic to human bladder cancer cells than inorganic arsenite (iAs(III)). DMMTA(V) induces cell death via reactive oxygen species (ROS), unlike iAs(III).
Area of Science:
- Environmental Toxicology
- Cancer Research
- Cell Biology
Background:
- Arsenic toxicity and carcinogenicity vary by chemical species.
- The bladder is a primary target organ for arsenic-induced cancer.
- Mechanisms of arsenic carcinogenicity and responsible species remain unclear.
Purpose of the Study:
- To compare the toxicity of DMMTA(V) and iAs(III) in human bladder cancer EJ-1 cells.
- To investigate the roles of reactive oxygen species (ROS) and aquaporin expression in arsenic toxicity.
Main Methods:
- Assessed cell viability, ROS production, and arsenic uptake in EJ-1 cells exposed to DMMTA(V) and iAs(III).
- Utilized N-acetyl-cysteine to investigate the role of ROS in DMMTA(V) and iAs(III) cytotoxicity.
- Examined aquaporin (AQP 3, 7, 9) mRNA and protein expression in EJ-1 and A431 cells using RT-PCR and Western blotting.
Main Results:
- DMMTA(V) (LC50=16.7 microM) was significantly more cytotoxic than iAs(III) (LC50=112 microM) in EJ-1 cells.
- DMMTA(V) induced high intracellular ROS levels, which were inhibited by N-acetyl-cysteine, indicating ROS-mediated toxicity.
- EJ-1 cells lacked AQP3, 7, and 9 expression, while A431 cells expressed AQP3, potentially explaining differential arsenic uptake and toxicity.
Conclusions:
- Pentavalent DMMTA(V) is a potent inducer of ROS and cytotoxicity in human bladder cancer cells.
- Trivalent iAs(III) toxicity is not primarily mediated by ROS and may be influenced by aquaporin-mediated uptake.
- Differences in aquaporin expression may contribute to the varying toxicity of arsenic species between different cell types.
