Dimethyl itaconate

Carcinogenicity

Description of key information

Carcinogenicity oral: no reliable data available
Carcinogenicity dermal: no data available
Carcinogenicity inhalation: no data available

Key value for chemical safety assessment

Carcinogenicity: via oral route

Endpoint conclusion

Endpoint conclusion:

no study available

Carcinogenicity: via inhalation route

Endpoint conclusion

Endpoint conclusion:

no study available

Carcinogenicity: via dermal route

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

The following statement bases on DSD, the Commission Directive 2001/59/EC (28th ATP of Council Directive 67/548/EEC) and CLP (5th ATP of Regulation (EC) No 1272/2008 of the European Parliament and of the Council) as implementation of UN-GHS in the EU:

There is a strong indication from the available data that DMI is not an inducer of carcinogenic processes. Thus no classification is required.

Additional information

Three published studies touching the carcinogenic potential of dimethyl itaconate are available to date:

- "Talalay (1988) / K2 SS / induction of quinone reductase and GST by DMI treatment" describes the testing of Dimethyl itaconate (DMI) in vitro (in Hepa 1c1c7 murine hepatoma cells) for its potency to induce quinone reductase (QR) activity as surrogate for phase II metabolic enzymes. In addition in the same study in an in vivo experiment in female CD1 mice treated 5 d via gavage with DMI the induction of QR and glutathione-S-transferase (GST) activity was measured. In the in vitro experiment Hepa lc1c7 murine hepatoma cells were grown in microtiter plates and the QR activity measured after incubation with the test item. In the in vivo experiment the compound was administered in single daily doses in 0.1 ml of Emulphor EL620P for 5 days. Cytosols were prepared from the tissues 24 hr after the last treatment and assayed for enzyme activities (using CDNB (1 -chloro-2,4 -dinitrobenzene) and DCNB (1,2 -dichloro-4 -nitrobenzene) as substrates for GST).

 

- In "Moon (1993) / K2 SS / Promotion of gastric tumours induced by MNNG treatment", a non-guideline study, 6 week old male Wistar rats were subjected to the following treatment:

Repeated dose experiment:

- 8 rats were treated with 200 mg/kg bw N-methyl-N'-nitro-N-nitrosoguanidine in 1:9 DMSO:water solution at day 0 and day 14.

- no further treatment in week 1

- exposure to 5 or 10 % NaCl in the diet from d 7 to d 14

- treatment with 0.2% dimethyl itaconate (DMI) in drinking water (= 2000 ppm = ca. 200 mg/kg bw) from d 15 on until the end of experiment (5 or 20 wks after first MNNG treatment)

- sacrifice of animals at the end of the treatment period and histopathologic analysis of the stomach

- measurement of quinone reductase activity in samples from stomach and liver in the 5 week experiment

Single oral treatment:

- measurement of ornithine decarboxylase activity in rats singly treated with 200 mg/kg bw MNNG in DMSO or NaCl in water (1.5 g/kg bw) or DMI in corn oil (1.1 g/kg bw)

In the biochemical experiment in the 5 week experiment a higher quinone reductase specific activities in forestomach tissue of rats treated with DMI + NaCl + MNNG as compared to a treatment with NaCl + MNNG (ca. factor of 2) was seen. In addition quinone reductase specific activities in liver are significantly lower than in forestomach tissue of rats treated with DMI + NaCl + MNNG (ca. a factor of 12). The evaluation of Ornithine Decarboxylase after single treatment with MNNG (200 mg/kg bw) revealed a ODC activity induction up to 288 pmol CO2/hr/mg protein at 24 hr after the administration (ca. 40 pmol CO2/hr/mg protein in controls). NaCl treatment (1.5 g/kg bw) lead to an induction of ODC activity up to 179 pmol CO2/hr/mg protein at 8 hr after the administration (ca. 10 pmol CO2/hr/mg protein in controls). DMI treatment (1.1 g/kg bw) induced ODC activity up to 539 pmol CO2/hr/mg protein at 16 hr after the administration (ca. 70 pmol CO2/hr/mg protein in controls).

The gross analysis of stomachs revealed no lesions neither in the glandular nor in the pylorus area of the stomach of any treatment group in the 5 and 20 week experiment. Control animals and animals treated with NaCl and/or DMI alone showed no gross lesion in the stomach. Treatment with MNNG + NaCl + DMI lead to stronger gross lesions than treatment with either MNNG + DMI or MNNG + NaCI (groups 7 and 8) or MNNG alone.

These results suggest that neither NaCl or DMI alone or in combination have any neoplastic effects on forestomach tissues.

Treatment with NaCl and/or DMI in combination at the levels used in the experiment promoted neo-plastic effects inflicted by MNNG.

Histopathologic analysis of the forestomach tissues revealed that gross lesion found in the 5 week experiments can be classified as hyperplasia or papilloma while in the 20 week experiment forestomach lesions classified as squamous cell carcinoma.

Some evidence was provided that treatment with high concentrations of DMI (2'000 ppm in drinking water) enhances the tumorigenic effect of MNNG. Induction of Quinone Reductase was seen in the 5 week treatment groups. Induction of Ornithine Decarboxylase after single treatment with a high amount of DMI (1.1 g/kg bw) was seen.

As these results were derived only with a low number of animals per group, as the used doses are high and as the informative value of the biochemical experiments is not established, the relevance of these results remain unclear.

On the other hand the experiments show that that neither NaCl or DMI alone or in combination have any neoplastic effects on forestomach tissues after oral gavage.

 

- In "Lee (1994)/K2 SS/(1 yr - Assessment of tumour promoting potential in F344 rats)" dimethyl itaconate (DMI) was tested for its tumour promoting effect on post-initiation stage of N-Methylnitrosourea induced gastric carcinogenesis in male Fischer 344 rats in a 1 year drinking water study.

Groups 1 and 2 were administered with N-methylnitrosourea (MNU) at a concentration of 100 ppm in the drinking water for the first 15 weeks. Group 2 was treated with 5000 ppm DMI in the drinking water for 37 weeks after the MNU treatment. Groups 3 and 4 were DMI alone and vehicle (water) treated control, respectively. In addition in two special experiments the effect of DMI on proliferation was tested by measuring of integration of BrdU or 3H-Thd in gastric tissue (application: oral doses of 200 mg/kg bw/d on 7 consecutive days (BrdU) or single oral dose of 1.25 g/kg bw respectively).

In the main experiment animals were observed for clinical signs, mortality and body weight development. After 52 wks they were sacrificed subjected to gross necroscopy and the gastric tissues were analysed histologically.

Tumours were found almost exclusively located in the pyloric region. Treatment with DMI alone (at 5000 ppm in drinking water = ca. > 500 mg/Kg bw/d) increased the incidence of gastric hyperplasia significantly (13.3 % in controls, 40 % in DMI alone treatment group). The combination of MNU pre-treatment with DMI treatment increase the gastric cancer incidence from 11.8 to 95 % (compared to MNU treatment alone). On the other hand DMI treatment alone did not lead to increased incidence of adenoma or carcinoma.

This is further supported by the results of the BrdU assay and the 3HdThd assay where it is shown that replicative DNA synthesis is significantly increased in pyloric tissues after DMI treatment.

These results suggest that DMI is able to enhance tumours if applied at high doses probably through induction of cell proliferation, but that it is not an inducer of tumour formation. Nevertheless the relatively low number of animals used, does not allow a final assessment of the carcinogenic potential of DMI.

 

Summary:

Based on the results from skin and eye irritation effects DMI is an irritating/corrosive substance.

From Talalay (1988) it can be learned that DMI is most probably an inducer of phase II metabolic enzymes. Such substances are usually believed to have a protective effect against carcinogenesis. On the contrary both Moon (1993) and Lee (1994) show that carcinogenesis in the forestomach induced by methylating agents (MNNG and MNU respectively) in rodents is increased by subsequent treatment with DMI via drinking water.

On the other hand, these studies both agree in the finding that DMI treatment alone does not induce tumour formation or carcinogenesis.

In addition it has to be taken into account that the treatment dose of ca. 200 and ca. 500 mg/kg bw/d (in Moon (1993) and Lee (1994) respectively) are relatively high. Finally the animal numbers are quite low in both studies and therefore the reliability of the derived data is limited and the results can only be regarded as to be indicative.

Conclusion:

There is a strong indication from the available data that DMI is not an inducer of carcinogenic processes.

The most likely explanation of the tumour promotion seen in the forestomach of rodent orally treated with DMI at high doses after induction of tumours by treatment with methylating agents is, that proliferation is induced through irritation/corrosion at the portal of entry that might lead to tumour promotion. This proliferating effect would only be seen at concentrations that are efficient to induce irritation/corrosion of local tissue.

Therefore a threshold value based on repeated dose oral treatment that guards from local adverse effects would be sufficient to cover a potential risk on enhancement of tumours at the portal of entry (forestomach/stomach) stemming from the irritating/corrosive effect of DMI.