Michael Weichenthal

Ultraviolet-induced formation of micronuclei and sister chromatid exchange in cultured fibroblasts of patients with cutaneous malignant melanoma

Genetically enhanced sensitivity to ultraviolet (UV) radiation may play an important role in the development of cutaneous malignant melanoma (CMM). This was studied in cultured fibroblasts of 26 CMM patients and controls by micronucleus (MN) test and sister chromatid exchange (SCE) after UV irradiation (375 J/m2). Sister chromatid exchange and MN formation were used as parameters to detect the UV-induced genotoxic damage in the individual cell strains. We found that the UV-induced level of MN was significantly increased in CMM patients (p = 0.0005), being most pronounced in the familial cases (p = 0.0001). Ultraviolet-induced SCE was also elevated in CMM patients (p = 0.001), but there was no difference between familial and nonfamilial cases. The present findings indicate that genetic predisposition contributes to the development of CMM in a subset of CMM patients and may be due to an enhanced susceptibility to UV light.

Increased numbers of spontaneous micronuclei in blood lymphocytes and cultures fibroblasts of individuals with familial cutaneous malignant melanoma

SummaryIn vitro detection of micronuclei was used to determine spontaneous chromosomal instability in cultured fibroblasts of 28 healthy normal controls, 28 individuals with nonfamilial cutaneous malignant melanoma (CMM) and 14 people with familial occurrence of CMM. Lymphocytes from 40 healthy controls, 40 CMM patients and 6 individuals with familial CMM were also compared for spontaneous expression of micronuclei in vitro. In the familial cases micronucleus frequency was found to be higher, both in cultured fibroblasts (P<0.005) and in lymphocytes (P<0.001) as compared to normal controls. There was no significant difference between nonfamilial cases and normal controls. We conclude that chromosomal instability may contribute to a genetic risk for development of cutaneous malignant melanoma.

Ultraviolet-induced chromosomal instability in cultured fibroblasts of heterozygote carriers for xeroderma pigmentosum

Fibroblast cultures of seven patients with xeroderma pigmentosum (XP), 19 healthy sibs or parents of XP patients (XP-heterozygotes), and 24 healthy normal controls were studied for chromosome instability induced by ultraviolet rays (UV). We used a UV source that contained predominantly UV-A and UV-B at an intensity of 500 J/m2 and evaluated the induction of micronuclei (MN) and sister chromatid exchange (SCE). the XP homozygotes had a UV sensitivity that was clearly above that of all heterozygotes and normal controls. Heterozygotes had an increased rate of UV-induced MN (4.76 +/- 1.96 vs. 1.82 +/- 2.05, p less than 0.0001) and increased UV induction of SCE (13.21 +/- 3.49 vs. 9.01 +/- 1.25, p less than 0.001), as compared to normal controls. These data support epidemiologic findings that suggest that XP heterozygotes are particularly cancer prone. In addition, the determination of the UV sensitivity in vitro as described may be used for genetic counseling of asymptomatic relatives of XP patients.

Fotemustine and interferon α2b in metastatic malignant melanoma

The efficacy of treatment with fotemustine and interferon (IFN) α was evaluated in metastatic melanoma. A group of 50 patients with metastatic malignant melanoma were treated with a combination of IFNα2b and the nitrosourea fotemustine. The patients received 10 MU IFN three times weekly for 3 weeks and fotemustine at a dose of 100 mg/m2 on days 8, 15 and 22. After a 5-week rest period, patients with stabilized or responding disease received a maintenance therapy consisting of 10 MU IFN three times a week for 1 week followed by administration of fotemustine (100 mg/m2) on day 8. This cycle was repeated every 4 weeks until progression occurred. If there was complete remission (CR), treatment was stopped after an additional three cycles. Toxicity and clinical response were scored according to WHO criteria. Objective response was seen in 14 patients (28%; 95% confidence interval 15.6%–40.4%) with four CR and ten partial responses (PR). The median duration of CR was 73 weeks, that of PR 26 weeks. Toxicity was acceptable, enabling treatment on an outpatient basis. The combination of fotemustine with IFNα is effective and well tolerated, but there is no evident advantage over fotemustine monotherapy in the treatment of metastatic melanoma.

Elevated serum-soluble ELAM-1 levels in patients with severe plaque-type psoriasis

Cell-surface adhesion molecules are thought to play an important role in establishing the intercellular contacts necessary for immunological reactions. Endothelial leukocyte adhesion molecule-1 (ELAM-1, E-selectin) is a cytokine-inducible adhesion molecule expressed on vascular endothelial cells [1]. It is an adhesion receptor for neutrophils, monocytes, subsets of T cells and possibly for eosinophils and certain tumour cells [2-4]. Its expression on activated endothelium parallels the intraand perivascular accumulation of neutrophils [5], suggesting a role in neutrophil adhesion and extravasation. ELAM-1 is not expressed in unstimulated endothelial cells in culture [6]. In normal skin only minimal staining for ELAM-1 is detectable on vascular endothelium of the upper dermis [7]. Following stimulation with IL-1 or TNF-alpha, but not with IFN-gamma, cultured endothelial cells express ELAM-1 [6]. In inflammatory skin diseases, such as allergic contact dermatitis, atopic dermatitis, polymorphic light eruption, sunburn and psoriasis, marked vascular endothelial expression has been demonstrated [5, 7, 8]. In addition to the membrane-bound ELAM-1 molecules, a soluble form of this molecule (sELAM-1) which is functionally active has been detected in sera and cell supernatants [9-12]. In the present study we sought to determine whether elevated serum levels of sELAM-I are present in patients with severe plaque-type psoriasis before and after successful therapy. Ten hospitalized male patients with severe plaque-type psoriasis (PASI score above 10.0, mean 18.6 + 7.2) and a mean age of 46.0 + 9.8 years were examined. The first serum sample from the patients was taken on admission before specific antipsoriatic treatment. All underwent a combined treatment including topical dithranol ointment and UVB radiation. The latter was performed in a Wald-

Increased UV-induced sister-chromatid exchange in cultured fibroblasts of first-degree relatives of melanoma patients

Cultured fibroblasts of 17 first-degree relatives of familial melanoma patients and six first-degree relatives of cutaneous melanoma (CMM) patients with multiple CMM primaries were tested for in vitro sensitivity to UV light. Fibroblasts of nine familial CMM patients with a known UV-sensitivity and 19 healthy probands served as a control. Sister chromatid exchange (SCE) was used as a parameter to detect UV-induced genotoxic damage. We found significantly (p less than 0.001) increased UV-induced SCE levels in familial melanoma patients, as well as in first-degree relatives of familial melanoma patients (p less than 0.001) after UV-A,B irradiation (375 J/m2), compared to the healthy probands without a family history of CMM. A significant (p less than 0.001) increase of UV-induced SCE was also observed in the relatives of CMM patients with multiple CMM primaries. In addition, the spontaneous SCE were significantly increased (p less than 0.05) in familial CMM patients. This study shows that increased UV sensitivity is a familial phenomenon. It is consistent with the concept of a genetic predisposition to CMM, which is based on increased UV sensitivity and may help to define groups with an elevated risk of developing cutaneous malignant melanoma.

Increased mutagen sensitivity in human cultured fibroblasts with constitutively high micronucleus levels

The induction of micronuclei (MN) by incubation with different mutagenic agents was tested in diploid fibroblast cultures obtained from 15 probands with constitutively high MN rates (15.75-77.25 MN/500 cells; average 36.27 +/- 17.60 MN) and 15 probands (controls) with low MN rates (4-13.75 MN/500 cells; average 8.97 +/- 2.73 MN). In order to find out whether fibroblast cultures of individuals with increased spontaneous MN levels exhibit an increased sensitivity to various agents with different genotoxic mechanisms, we studied the induction of MN in these cell cultures by ultraviolet (UV) irradiation, mitomycin C (MMC), N-methyl-N-nitro-N-nitrosoguanidine (MNNG) and benzo-(a)pyrene-diol-expoxid (BPDE). In addition, we tested aphidicolin (APC), a polymerase alpha inhibitor, which is a potent inducer of common fragile sites. Probands with spontaneously high MN showed an significantly increased sensitivity to UV (p less than or equal to 0.005), MMC (p less than or equal to 0.005), and BPDE (p less than or equal to 0.005). No significant differences were found for MNNG and APC as compared to controls.

Constitutively increased micronuclei are predominantly caused by acentric fragments.

The frequency of kinetochore (centromere)-positive micronuclei (MN) was determined in 32 fibroblast cell lines. We tested 16 probands with spontaneously high MN levels (greater than or equal to 20 MN/500 cells (4%] and 8 probands (controls) with low MN levels (less than or equal to 13 MN/500 cells (2.6%]. To study whether the elevation of MN levels is due to increased chromosomal breakage we used the antikinetochore antibody fluorescent staining method. Probands with spontaneously high MN had kinetochore-positive MN increased by a factor 2.1 compared to the controls whereas the kinetochore-negative MN were increased by a factor 6.14. This shows that spontaneous elevation of MN is mainly caused by increased chromosomal breakage and only in a minor proportion by chromosome segregation errors as a consequence of spindle defects.

Elevated frequencies of micronuclei in cultured fibroblasts after freezing and thawing

Spontaneous micronuclei (MN) were determined in 69 fibroblast lines in the first subculture after cryoconservation. 45 cultures (65%) showed micronuclei in the normal range (less than 10 MN/500 cells), but 24 (35%) exhibited an elevation up to 60 MN/500 cells. In order to determine whether freezing and thawing is responsible for the enhanced MN level we studied the persistence of elevated MN in 10 cell cultures after freezing and thawing, and found that the MN levels returned to normal after 3 subcultures. In addition, the micronucleus formation before and after freezing was investigated in 2 newly established cell cultures obtained from probands whose cells had a particularly high number of MN. Both cultures had regular MN levels before freezing but a more than doubled number of MN when frozen samples were recultivated. This effect of the freezing procedure was confirmed with 5 separate biopsies obtained from the same donor. Since a freezing-related increase in MN was constantly observed in cells from some individuals but not in others, it might be possible that it is a constitutive trait which causes cultured fibroblasts of some individuals to be hypersensitive to the freezing and thawing procedure. It is also noteworthy that fibroblasts from 8 out of 12 probands with a familial malignant melanoma exhibited this phenomenon.

Increased spontaneous formation of micronuclei in cultured fibroblasts of first-degree relatives of familial melanoma patients

The phenomenon of spontaneous increased micronuclei and enhanced UV-sensitivity, which is known for familial cutaneous malignant melanoma (CMM) patients, could be demonstrated again in fibroblasts of 17 familial CMM patients. In order to determine if close relatives of familial CMM patients show both a comparable spontaneous chromosomal instability and enhanced UV-sensitivity, cultured fibroblasts of 24 healthy, first-degree relatives of patients with familial malignant melanoma were investigated. The cytokinesis-block micronucleous technique was used to detect enhanced chromosomal instability. Fibroblasts of the investigated relatives showed a significantly increased spontaneous formation of micronuclei, in comparison to 19 healthy controls, but no enhanced UV-sensitivity was evident. We conclude that chromosomal instability might be a hereditary trait and a causative factor in developing familial malignant melanoma. This supports the concept of a genetic predisposition to familial CMM and may help to identify high-risk family members at a cytogenetic level in addition to the common clinicopathological traits.