For definition of Groups, see Preamble Evaluation.
Supplement 7: (1987) (p. 366)
Chem. Abstr. Name: 2,5,9-Trimethyl-7H-furo[3,2-g]benzopyran-7-one
A. Evidence for carcinogenicity to humans (inadequate)
Malignant melanoma was diagnosed in a 30-year-old male shortly after commencement of treatment with 4,5',8-trimethylpsoralen for vitiligo. No skin cancer was observed during two to 14 months of follow-up in 57 patients with psoriasis treated for one to 23 months with 4,5',8-trimethylpsoralen [ref: 1].
B. Evidence for carcinogenicity to animals (inadequate)
No skin tumour was observed in mice given thrice-weekly skin applications of 4,5',8-trimethylpsoralen followed by low doses of ultraviolet A irradiation for nine months [ref: 1,2].
C. Other relevant data
No data were available on the genetic and related effects of 4,5',8-trimethylpsoralen in humans.
In combination with ultra-violet A radiation, 4,5',8-trimethylpsoralen bound covalently to DNA in guinea-pig skin in vivo. It induced sister chromatid exchanges and unscheduled DNA synthesis in human cells in vitro, and DNA cross-links in human and rodent cells in vitro. It induced mutation in yeast and DNA damage in bacteria. Results on the induction of mutation in bacteria were inconclusive [ref: 3].
In the absence of ultra-violet A radiation, 4,5',8-trimethylpsoralen did not induce sister chromatid exchanges in human lymphocytes in vitro; results for induction of unscheduled DNA synthesis were equivocal. Mutagenicity studies in bacteria were inconclusive [ref: 3].
4,5,8'-Trimethylpsoralen is not classifiable as to its carcinogenicity to humans (Group 3).
For definition of the italicized terms, see Preamble Evaluation.
Also see previous evaluation: Vol. 40 (1986)
1. IARC Monographs, 40, 357-371, 1986
2. Hannuksela, M., Stenbäck, F. & Lahti, A. (1986) The carcinogenic properties of topical PUVA. A lifelong study in mice. Arch. Dermatol. Res., 278, 347-351
3. IARC Monographs, Suppl. 6, 541-544, 1987
See Also: Toxicological Abbreviations