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Basal cell carcinoma (BCC) is the commonest cancer in Caucasians. Its incidence is rising and many patients develop multiple primary tumours at separate sites. Factors determining time between first primary tumour presentation and the next new primary lesion are unclear. We used Cox's proportional hazards model to study, in 856 Caucasians, the influence of tumour site, individual characteristics and polymorphism in glutathione S-transferase (GSTM1, GSTT1) and cytochrome P450 (CYP2D6, CYP1A1) loci on time to next primary tumour presentation. More than one tumour at first presentation (P <0.0001, hazard ratio 2.72) and GSTT1 null (P = 0.028, hazard ratio 1.74) were associated with decreased time to next primary tumour presentation. Significant two-factor interactions, corrected for number of tumours at presentation, were identified between a truncal tumour at first presentation and each of male gender, GSTM1 null and CYP2D6 EM (P <0.003, hazard ratios 3.09-3.82). In each of these cases, all patients with the risk combination demonstrated further separate tumours within 5 years of first presentation. Thus, patients with a truncal tumour at first presentation, especially males and those presenting with more than one lesion have a significantly decreased time to presentation of further tumours and should receive more meticulous follow-up. Polymorphism in GSTM1 and CYP2D6 also influences the rate of new primary tumour accrual giving insights into the link between ultraviolet exposure and multiple tumour development.

Basal cell carcinoma (BCC) places increasing burdens on clinicians; incidence is rising and patients may develop multiple primary tumors. Although UV exposure is critical, many patients develop tumors at less-exposed sites, such as the trunk, suggesting a genetic predisposition. We previously showed that polymorphism in loci encoding the detoxifying enzymes, glutathione S-transferase (GSTM1, GSTM3, GSTT1) and cytochrome P450 (CYP2D6, CYP1A1) influences susceptibility to BCC. We now describe a case-control approach in 345 patients with BCC that examines the role of these polymorphisms and patient characteristics (age, gender, skin type, hair color, eye color, smoking, occupation) in determining susceptibility to truncal tumors. GST and CYP genotypes were identified using polymerase chain reaction-based methods. Patients with one or more truncal tumors were significantly younger (p = 0.0170) than those with no truncal tumors. Male gender also appeared more common in the truncal tumor group, although this did not achieve significance (p = 0.0925). Patients whose first tumor was truncal had significantly more tumors (p = 0.0297). GSTT1 null (p = 0.0245, odds ratio 2.24) and CYP1A1 Ile/Ile (p = 0.0386, odds ratio 2.86) were associated with truncal site after correction for age and gender. The combination, GSTT1 null and CYP1A1 Ile/Ile, was particularly significant (p = 0.0059, odds ratio = 2.95). These effects were present after correction for tumor numbers. These data show first, patients with truncal tumors constitute a high-risk group for BCC, second, a significant genetic influence on BCC site, and third, a significant interaction between GSTT1 and CYP1A1 genotypes.

The genetic factors that mediate the pathogenesis of multiple primary cutaneous basal cell carcinomas (BCC) are largely unclear. Thus, some patients suffer many BCC (>30) and/or rapid accrual (number of tumours/year from first presentation) of further lesions. We have studied, in 827 English Caucasians, the influence of polymorphism in carcinogen-metabolizing enzymes on susceptibility to this cancer. Accordingly, we describe, first, a cross-sectional analysis of the influence of GSTM1, GSTT1, CYP2D6 and CYP1A1 genotypes on tumour numbers, and secondly, a longitudinal analysis, in 169 of these cases, of the effect of these genes on tumour accrual. We have confirmed the expected importance of age and number of lesions at presentation, and male gender and skin type as risk factors. Furthermore, the cross-sectional analysis showed CYP1A1 m1m1 (P = 0.004; rate ratio 1.242) and CYP2D6 EM (P < 0.001, rate ratio 1.266) are associated with increased numbers of BCC. The longitudinal study showed, after adjustment for age and tumour number at presentation, that GSTT1 null (P < 0.001, rate ratio 2.677) and CYP2D6 EM (P < 0.001, rate ratio 2.154) were significant determinants of accrual while CYP1A1 Ile/Ile was associated with slower accrual than the Ile/Val and Val/Val genotypes (P = 0.008, rate ratio 0.690). We believe these are the first genetic factors to be associated with tumour accrual. No significant interactions between genotypes were identified, though the combinations GSTM1 null/skin type 1 (P < 0.001, rate ratio 2.702), CYP2D6 EM/male gender (P = 0.049, rate ratio 1.279) and CYP2D6 EM/blue+green eyes (P = 0.046, rate ratio 1.388) influenced tumour numbers. Previous studies indicate the importance of effective repair of UV-damaged DNA in the pathogenesis of multiple BCC; indeed the influence of GSTM1 may result from its ability to utilize 5'-hydroxymethyluracil. However, the finding that CYP2D6 and CYP1A1 influence tumour numbers and accrual indicates detoxification of unknown molecules is important and supports the view that factors other than UV are important in the pathogenesis BCC.

The influence of polymorphism in the glutathione S-transferase, GSTM3 gene on susceptibility to cutaneous basal cell carcinoma (BCC) has been investigated. We have reported previously two GSTM3 alleles, GSTM3*A and GSTM3*B, distinguished by a recognition motif for the YY1 transcription factor in GSTM3*B. In this study, immunohistochemistry was used to identify GSTM3 expression in the epidermis of skin samples from 11 controls and 9 patients with BCC. A PCR method was used to identify GSTM3*A and GSTM3*B and thereby the GSTM3 AA, GSTM3 AB, and GSTM3 BB genotypes in 300 controls and 286 Caucasians with 1-35 primary BCCs. Genotypes at GSTM1, GSTT1, and the cytochrome P450 CYP1A1 and CYP2D6 loci were also determined. Frequencies of GSTM3, GSTM1, GSTT1, CYP2D6, and CYP1A1 genotypes in the cases and controls were not different. Dividing the BCC cases into groups of 92 patients with 1 lesion and 194 patients with 2-35 lesions showed that the frequencies of GSTM3 BB (2.6%) and GSTM1 A/B (1.3%) in the group with 2-35 tumors were almost significantly lower than in the group with 1 lesion (7.6%, exact P = 0.0601, chi 2(1) = 3.390; 6.5%, exact P = 0.055, chi 2(1) = 4.946, respectively). Within the cases with 2-35 tumors, a Poisson regression model was used to identify genotypes, characteristics such as skin type, and interactions between genotypes and characteristics associated with increasing numbers of tumors. This showed, after correction for male gender and age, that GSTM3 AA was not associated with risk of increased numbers of tumors, although in combination with skin type 1, GSTM1 null, and CYP1A1 m1m1, the genotype did confer increased risk (P < 0.001, rate ratio, 2.058; P < 0.001, rate ratio, 1.606; P < 0.001, rate ratio, 1.470 respectively). The data suggest that, like other allelic GST, GSTM3 influences cancer risk. As GSTM3 AA was associated with increased tumor numbers, it appears that YY1 acts as an activator of the recognition motif in GSTM3*B.

The factors that determine development of single and multiple primary cutaneous basal cell carcinomas (BCCs) are unclear. We describe a case-control study firstly, to examine the influence of allelism at the glutathione S-transferase GSTM1 and GSTT1 and cytochrome P450 CYP2D6 loci on susceptibility to these tumours and, secondly, to identify interactions between genotypes and relevant individual characteristics, such as skin type and gender. Frequency distributions for GSTM1 genotypes in cases and controls were not different, although the frequency of GSTM1 A/B was significantly lower (P = 0.048) in the multiple BCCs than in controls. We found no significant differences in the frequencies of GSTT1 and CYP2D6 genotypes in cases and controls. Interactions between genotypes were studied by comparing multinomial frequency distributions in mutually exclusive groups. These identified no differences between cases and controls for combinations of the putatively high risk GSTM1 null, GSTT1 null, CYP2D6 EM genotypes. Interactions between GSTM1 A/B and the CYP2D6 PM and GSTT1-positive genotypes were also not different. Frequency distributions of GSTM1 A/B with CYP2D6 EM in controls and multiple BCCs were significantly different (P = 0.033). The proportion of males in the multiple BCC group (61.3%) was greater than in controls (47.0%) and single BCC (52.2%), and the frequency of the combination GSTM1 null/male gender was significantly greater in patients with multiple tumours (P = 0.002). Frequency distributions of GSTM1 null/skin type 1 were also significantly different (P = 0.029) and the proportion of subjects who were GSTM1 null with skin type 1 was greater (P = 0.009) in the multiple BCC group. We examined the data for interactions between GSTM1 null/skin type 1/male gender by comparing frequency distributions of these factors in the single and multiple BCC groups. The distributions were almost significantly different (exact P = 0.051). No significant interactions between GSTT1 null or CYP2D6 EM and skin type 1 were identified. Comparisons of frequency distributions of smoking with the GSTM1 null, GSTT1 null and CYP2D6 EM genotypes identified no differences between patients with single and multiple tumours.