Thiosemicarbazide

Carcinogenicity

Description of key information

Key study: Under the test conditions, thiosemicarbazide gave somewhat ambiguous results, through administered at high enough dose levels to be toxic.

Key value for chemical safety assessment

Carcinogenicity: via oral route

Link to relevant study records

Reference

Endpoint:

carcinogenicity: oral

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

significant methodological deficiencies

Remarks:

No GLP study.

Qualifier:

according to guideline

Guideline:

other: Guideline for carcinogen bioassay in small rodents (Washington, D.C.:US Govt Print Off, 1976)

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: Carcinogenicity testing: A report of the panel of the Cancer Research Commission of UICC, Vol 2. Geneva: UICC, 1969

Deviations:

no

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 451 (Carcinogenicity Studies)

Deviations:

yes

Remarks:

1.In the study, 26 animals/each sex were used,but according the TG 451 there should be used 50 animals/each sex. 2.The length of test. In the present study,length of the test was 18 months, but according the TG 451 the length should be 24 months.

GLP compliance:

not specified

Species:

rat

Strain:

other: Charles River CD

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source:Breeding laboratories, Non Wilmington, Mass.
- Housing: 2 per large plastic cage (12x14x7 inches) on corncob bedding (San-i-cel; Paxton Processing Co.,Inc., Paxton, Ill.).
- Diet (e.g. ad libitum):Wayne Lab Blox meal. Mixtures prepared as for the animal diets were stored for 10 days at room temperature to determine the possible degradation of the compound added.
- Water (e.g. ad libitum): ad libitum.
- Acclimation period:7-10 days

Route of administration:

oral: feed

Vehicle:

unchanged (no vehicle)

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
For diet mixing, a small portion of meal was mixed thoroughly in a mortar with the proper amount of the compound; the resultant concentrate was added to more meal and blended for 15-20 minutes in a twin-shell blender.

DIET PREPARATION
- Rate of preparation of diet (frequency):Diet was prepared in 6-kg lots twice weekly
- Storage temperature of food:in refrigerator at 4ºC

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Required level (ppm): 100-200
Recovery (%) : 83.8+-3.8
Stability in days: 10
Loss % : none

Duration of treatment / exposure:

Total weeks on drug: 78

Frequency of treatment:

Daily

Post exposure period:

6 months

Dose / conc.:

75 ppm

Remarks:

The high dose

Dose / conc.:

37.5 ppm

Remarks:

The low dose

No. of animals per sex per dose:

26 animals per dose/sex (total 104)

Control animals:

yes

Details on study design:

- Dose selection rationale: The doses were selected according the previous study on Acute toxicity. Five distinct levels of each compund were mixed in diet, or given twice weekly in stomach tube to groups of 3 animals each over 30 days, followed by 30 days fo observation for detection of delayed toxicity.

Positive control:

2 groups with N-2-fluorenylacetamide in the diet at 80 ppm (32 rats) or 250 ppm (20 rats).

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes (mortality)

DETAILED CLINICAL OBSERVATIONS: Yes (The presence of palpable masses was noted during weighting, transfer to clean cages.)
- Time schedule: Twice daily, 7 days a week for toxicologic effects and death

BODY WEIGHT: Yes
- Time schedule for examinations: weekly during the initial month of the chronic study and beewekly thereafter.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study):
- Food consumption for each animal determined: Yes - during the initial week and the fourth week of each subsequent 4-week period.

FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: No data

OPHTHALMOSCOPIC EXAMINATION: No data

HAEMATOLOGY: No data

CLINICAL CHEMISTRY: No data

URINALYSIS: No data

NEUROBEHAVIOURAL EXAMINATION: No data

Sacrifice and pathology:

GROSS PATHOLOGY: Yes

HISTOPATHOLOGY: Yes, The tissues were fixed in 10% neutral buffered Formalin, sectioned, and stained with hematoxylin and eosin.Examintaion:cerebrum, cerebellum,pituitary gland, spinal cord plus vertebrae, lung, heart,mediastinum, thymus, thyroid gland, parathyroid gland,liver, spleen, pancreas, adrenal gland, kidney, urinary bladder, ovary, uterus or testis, accessory sex organ, esophagus, stomach, intestinal tract, and any abnormal tissue or mass.Animals were necropsied, and stained sections of the tissues were examined microscopically to detect any changes.

Statistics:

Probabilities of survival were estimated by the product-limit procedure of Kaplan and Meier (10), which is commonly called the "life table method." Animals were statistically censored as of the time they died of other than natural causes or were found to be missing; animals dying from natural causes were not statistically censored. For statistical analyses of a possible dose-related effect on survival, the method : extensions of Cox's methoas for testing for a dose-related trend were used.
One-tailed Fisher's exact probability test was used to compare the tumor incidence of a matched negative or vehicle control group with that of a group of dosed animals at each dose level. Inasmuch as the results for 2 dosed groups were compared simultaneously with those for a control group, a correction to ensure an overall significance level of 0.05 could be made.

The Bonferroni inequality requires that the P-value for any comparison be less than or equal to 0.0512 = 0.025.

The Cochran-Armitage test for linear trend in proportions, with continuity correction was also used, if the slope of the dose-response curve is different from zero at the one-tailed 0.05 level of significance.

Clinical signs:

not specified

Dermal irritation (if dermal study):

not examined

Mortality:

mortality observed, non-treatment-related

Description (incidence):

Low dose females had greater mortality than matched negatve controls had.
At least 22 animals of each treated group survived to 78 weeks.
In the matched control group, male survivals were only 9 and females survivals was 10.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Mean body weight from the treated groups (high dose) was less than in the matched or pooled groups, but no difference noted with treated gropus (low dose).

Food consumption and compound intake (if feeding study):

not specified

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

not examined

Haematological findings:

not examined

Clinical biochemistry findings:

not examined

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

not specified

Gross pathological findings:

not specified

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

not specified

Histopathological findings: neoplastic:

effects observed, treatment-related

Description (incidence and severity):

High dose group: 2 females had mammary adenocarcinomas.
Low dose group, pooled or matched group: None. The diference was not significant.
Ten negative control groups, females: 4 mammary carcinonoms of 184 animals
In the 184 control animals, the incidence of mammary tumors was 45%, which is less than the rate in either the low or high-dose groups but considerably above the 30 and 35% found in the matched and pooled negative controls respectively.
One negative control group had an incidence exceeding the 73% in the low-dose group, and 2 other groups had incidences approaching the 62% in the high-dose groups.

Other effects:

not examined

Relevance of carcinogenic effects / potential:

The author of this study confirmed that these results are ambiguous.

Key result

Dose descriptor:

conc. level:

Effect level:

ca. 75 ppm

Based on:

test mat.

Sex:

female

Basis for effect level:

histopathology: neoplastic

Remarks on result:

other: Ambiguous results

Key result

Critical effects observed:

not specified

Body weight of control groups: MALES: 51 wk 709 g (range of mean body wt 644-760 g); at 77 wk - 766 g (718-854 g); and at 104 wk - 737 g (635-812 g).

FEMALES, corresponding: 402 g (357-447), 486 g (441-549), and 541 g (487-629)

SURVIVALS at 52 wk : 100% for males and females.

Conclusions:

Under the test conditions, thiosemicarbazide gave somewhat ambiguous results, though administered at high enough dose levels to be toxic.

Executive summary:

According the publication from the Journal of the National Cancer Institute,the test item was tested for the carcinogenicity in the Charles River rats. In this chronic study chemicals was given to groups of 26 male and 26 female in the maximum tolerated doses and its half amount (75 ppm and 37.5 ppm) in a diet form during 78 weeks. After the treatment, they were observed during 6 months.Control groups animal (matched and pooled) were used in the study.Two positive control groups with the N-2 -fluorenylacetamide were used to check the response to a known carcinogen at different dose level (80 ppm and 250 ppm). Ten negative male and 10 negative female control groups consisted of 184 animals. Rats were examinated twice daily, 7 days a week for toxicologic effects, weighted weekly during first month and then biweekly. Food consumption was determinated also. After 78 weeks of the study, five animals from each group in the higher dose were killed and necropsied and used for calculation of tumor incidence. At the end of the study were detected the following results: Low dose females had greater mortality than matched negative controls had, but at least 22 animals of each treated group survived to 78 weeks. In the low-dose group, 19 female rats and in high-dose group 16 female rats had mammary tumor. In the matched control group, male survivals were only 9 and females survivals was 10. In the high dose group, two females had mammary adenocarcinomas. Ten negative control groups, females, four of 184 animals had mammary carcinonoms. In the 184 control animals, the incidence of mammary tumors was 45%, which is less than the rate in either the low or high-dose groups but considerably above the 30 and 35% found in the matched and pooled negative controls respectively. One negative control group had an incidence exceeding the 73% in the low-dose group, and 2 other groups had incidences approaching the 62% in the high-dose groups.Finally, it has to be taken into account, that the results of the carcinogenicity of Thiosemicarbazide are ambigious.

Justification for classification or non-classification

According the available data Thiosemicarbazide it can not be classified as carcinogenic according to CLP Regulation no. 1272/2008 due to the ambiguous results.

Additional information

Key study: In the present publication from the Journal of the National Cancer Institute,the test item was tested for the carcinogenicity in the Charles River rats. In this chronic study chemicals was given to groups of 26 male and 26 female in the maximum tolerated doses and its half amount (75 ppm and 37.5 ppm) in a diet form during 78 weeks. After that, there was 6 months observation. Control groups (matched and pooled) were used in the study.Two positive control groups with the N-2 -fluorenylacetamide and ten negative male and 10 negative female control groups were used too. After 78 weeks of the study, five animals from each group in the higher dose were killed and necropsied and used for calculation of tumor incidence. At the end of the study were detected the following results: In the low-dose group, 19 female rats and in high-dose group 16 female rats had mammary tumor. The survivors numbered only 9 in the male group and 10 in the female group. In the high dose group, two females had mammary adenocarcinomas. Ten negative control groups, females, four of 184 animals had mammary carcinonoms. In the 184 control animals, the incidence of mammary tumors was 45%, which is less than the rate in either the low or high-dose groups but considerably above the 30 and 35% found in the matched and pooled negative controls respectively. One negative control group had an incidence exceeding the 73% in the low-dose group, and 2 other groups had incidences approaching the 62% in the high-dose groups. It has to be taken into account, that the results of the carcinogenicity of Thiosemicarbazide are ambigious.