Registration Dossier

Administrative data

Endpoint:
specific investigations: other studies
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
Not reported
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Study conducted in accordance with generally accepted scientific principles, possibly with incomplete reporting or methodological deficiencies, which do not affect the quality of the relevant results.

Data source

Reference
Reference Type:
publication
Title:
Inhibitory Effects of Phenolic Compounds on Benzo(a)pyrene-induced Neoplasia
Author:
Wattenberg LW, Coccia JB & Lam KT
Year:
1980
Bibliographic source:
Cancer Res. 40: 2820-2823

Materials and methods

Test guideline
Qualifier:
no guideline followed
Principles of method if other than guideline:
The study was conducted to investigate the inhibitory effects of 18 synthetic phenolic compounds, including the test material, on benzo(a)pyrene-induced neoplasia of the forestomach of female ICR/Ha mice.
The investigation was designed to explore the relationships between the chemical structure of phenols and their potency as inhibitors of BP-induced neoplasia.
Female mice were exposed to the test material in the diet for approximately 5 and a half weeks, along with benzo(a)pyrene. At the end of the experiment, any tumour suppression caused by the test material was evaluated.
GLP compliance:
not specified
Type of method:
in vivo
Endpoint addressed:
other: tumour suppression

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
not specified
Details on test material:
- Name of test material (as cited in study report): 2,4,6-Tri-tert-butylphenol
- Supplier: Aldrich Chemical Co. (Milwaukee, WI, USA)
- Purity: 97 %

Test animals

Species:
mouse
Strain:
ICR
Sex:
female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Harlan Sprague-Dawley, Madison, WI, USA
- Strain: ICR/Ha
- Age at study initiation: 9 weeks of age
- Diet: Powdered Purina rat chow whilst being administered the test material, pellets of Purina rat chow following cessation of dosing

Administration / exposure

Route of administration:
other: Test material was administered orally in the diet; the carcinogen benzo(a)pyrene was administered by oral gavage
Vehicle:
other: No vehicle was used in test material administration; benzo(a)pyrene was dosed in corn oil
Details on exposure:
PREPARATION OF DOSING SOLUTIONS: Mice were dosed with benzo(a)pyrene at a concentration of 1 mg in 0.2 mL of corn oil by gavage.
Analytical verification of doses or concentrations:
no
Duration of treatment / exposure:
Approximately 5.5 weeks
Frequency of treatment:
Animals were exposed to the test material continually in the diet. The carcinogen benzo(a)pyrene was administered for the first time following 8 days of test material administration. Overall the mice were given 8 doses of benzo(a)pyrene (twice weekly for 4 weeks). The exposure to the diet containing the test material continued for a further 3 days after the last dose of carcinogen.
Post exposure period:
Approximately 109 days.
Dosing began when animals were 9 weeks of age and continued for approximately 5.5 weeks. The mice were sacrificed at 211 days of age.
Doses / concentrations
Remarks:
Doses / Concentrations:
0.03 mmol/g in the diet
Basis:
nominal in diet
No. of animals per sex per dose:
15 female mice were dosed with the test material
Control animals:
other: Control mice were administered plain diet and benzo(a)pyrene by gavage

Examinations

Examinations:
The mice were killed when they were 211 days old and autopsied. The stomachs were fixed in an expanded state produced by i.g. injection of formalin. Subsequently, they were split longitudinally. Tumours of the forestomach were counted under a dissecting microscope. Tumours that were 1 mm or larger were recorded and checked histologically.

Results and discussion

Details on results:
The test material was determined to be ineffective as an inhibitor of tumour formation. Some of the other materials studied did exhibit inhibitory properties; however, analysis of the structures and activity determined that substitution of a third tert-butyl group para to the OH totally destroys the inhibitory activity. In general, 3 or more substitutions on the phenol ring render the molecule inactive as an inhibitor.

Any other information on results incl. tables

Table 1: Effect of the Test Material in the Diet on Benzo(a)pyrene-induced Neoplasia of the Forestomach in Female Mice

Dose Group (mmol/g in the diet)

No. of Mice

Weight Gain from 63 to 211 days of Age (g)

Tumours of the Forestomach

Percentage of Mice with Tumours

No. of Tumours / Mouse*

No. of Tumours per Mouse (test / control)

Control

19

100

100

4.8 ± 0.5

-

0.03

15

93

93

5.9 ± 0.7

1.23

*Number of tumours occurring in the entire group divided by the number of mice at risk

Applicant's summary and conclusion

Conclusions:
Under the conditions of this study, the test material did not exhibit an inhibitory effect on benzo(a)pyrene-induced neoplasia.
Executive summary:

The study was conducted to investigate the inhibitory effects of 18 synthetic phenolic compounds, including the test material, on benzo(a)pyrene-induced neoplasia of the forestomach of female ICR/Ha mice.

The investigation was designed to explore the relationships between the chemical structure of phenols and their potency as inhibitors of BP-induced neoplasia.

Female mice were exposed to the test material in the diet for approximately 5 and a half weeks, along with the carcinogen benzo(a)pyrene. At the end of the experiment, any tumour suppression caused by the test material was evaluated.

The test material was determined to be ineffective as an inhibitor of tumour formation. Some of the other materials studied did exhibit inhibitory properties; however, analysis of the structures and activity determined that substitution of a third tert-butyl group para to the OH totally destroys the inhibitory activity. In general, 3 or more substitutions on the phenol ring render the molecule inactive as an inhibitor.

Under the conditions of this study, the test material did not exhibit an inhibitory effect on benzo(a)pyrene-induced neoplasia.