Nonmonoclonal PTCH Gene Mutations in Psoralen Plus UVA-Associated Basal Cell Carcinomas
2007; Elsevier BV; Volume: 128; Issue: 3 Linguagem: Inglês
10.1038/sj.jid.5701128
ISSN1523-1747
Autores Tópico(s)Nonmelanoma Skin Cancer Studies
Resumobasal cell carcinoma patched psoralen plus UVA TO THE EDITOR Cumulative high-dose psoralen plus UVA (PUVA) exposure variantly increases the risk of skin cancer (especially nonmelanoma types). For example, its influence on squamous cell carcinoma risk is enormous (up to 250-fold) (Nijsten and Stern, 2003Nijsten T.E. Stern R.S. The increased risk of skin cancer is persistent after discontinuation of psoralen+ultraviolet A: a cohort study.J Invest Dermatol. 2003; 121: 252-258Abstract Full Text Full Text PDF PubMed Scopus (180) Google Scholar) but remarkably weaker on basal cell carcinoma (BCC) risk, particularly after adjustment for other risk factors and sun exposure (Stern et al., 1998Stern R.S. Liebman E.J. Vakeva L. Oral psoralen and ultraviolet-A light (PUVA) treatment of psoriasis and persistent risk of nonmelanoma skin cancer. PUVA Follow-up Study.J Natl Cancer Inst. 1998; 90: 1278-1284Crossref PubMed Scopus (231) Google Scholar; Nijsten and Stern, 2003Nijsten T.E. Stern R.S. The increased risk of skin cancer is persistent after discontinuation of psoralen+ultraviolet A: a cohort study.J Invest Dermatol. 2003; 121: 252-258Abstract Full Text Full Text PDF PubMed Scopus (180) Google Scholar). Despite the clear link between PUVA and skin cancer and a roster of suspected pathogenic mechanisms (for example, tumor initiation, tumor promotion, local and systemic immunosuppression, and direct stimulation by oncogenic human papillomavirus) (Wolf et al., 2004aWolf P. Seidl H. Back B. Binder B. Hofler G. Quehenberger F. et al.Increased prevalence of human papillomavirus in hairs plucked from patients with psoriasis treated with psoralen-UV-A.Arch Dermatol. 2004; 140: 317-324Crossref PubMed Scopus (28) Google Scholar), the exact mechanisms of human PUVA-associated skin cancer remain unknown. Previously, we reported that the p53 mutations in a sample of 13 PUVA-associated BCCs were most commonly UV fingerprints (that is, C → T or CC → TT transitions at dipyrimidine sites) and less frequently potential PUVA fingerprints at psoralen crosslinking sites (that is, 5′TpA or 5′TpG sequences) (Seidl et al., 2001Seidl H. Kreimer-Erlacher H. Back B. Soyer H.P. Hofler G. Kerl H. et al.Ultraviolet exposure as the main initiator of p53 mutations in basal cell carcinomas from psoralen and ultraviolet A-treated patients with psoriasis.J Invest Dermatol. 2001; 117: 365-370Crossref PubMed Scopus (40) Google Scholar). Half of those tumors, however, contained no p53 mutations at all, suggesting that other genes (for example, the patched (PTCH) gene) may have suffered PUVA damage. Originally identified as the cause of Gorlin's syndrome (Hahn et al., 1996aHahn H. Christiansen J. Wicking C. Zaphiropoulos P.G. Chidambaram A. Gerrard B. et al.A mammalian patched homolog is expressed in target tissues of sonic hedgehog and maps to a region associated with developmental abnormalities.J Biol Chem. 1996; 271: 12125-12128Abstract Full Text Full Text PDF PubMed Scopus (173) Google Scholar; Johnson et al., 1996Johnson R.L. Rothman A.L. Xie J. Goodrich L.V. Bare J.W. Bonifas J.M. et al.Human homolog of patched, a candidate gene for the basal cell nevus syndrome.Science. 1996; 272: 1668-1671Crossref PubMed Scopus (1566) Google Scholar), the PTCH gene has since been found to be lost or mutated in more than the half of sporadic BCCs (Hahn et al., 1996bHahn H. Wicking C. Zaphiropoulous P.G. Gailani M.R. Shanley S. Chidambaram A. et al.Mutations of the human homolog of Drosophila patched in the nevoid basal cell carcinoma syndrome.Cell. 1996; 85: 841-851Abstract Full Text Full Text PDF PubMed Scopus (1606) Google Scholar; Unden et al., 1996Unden A.B. Holmberg E. Lundh-Rozell B. Stahle-Backdahl M. Zaphiropoulos P.G. Toftgard R. et al.Mutations in the human homologue of Drosophila patched (PTCH) in basal cell carcinomas and the Gorlin syndrome: different in vivo mechanisms of PTCH inactivation.Cancer Res. 1996; 56: 4562-4565PubMed Google Scholar; Xie et al., 1997Xie J. Johnson R.L. Zhang X. Bare J.W. Waldman F.M. Cogen P.H. et al.Mutations of the PATCHED gene in several types of sporadic extracutaneous tumors.Cancer Res. 1997; 57: 2369-2372PubMed Google Scholar; Aszterbaum et al., 1998Aszterbaum M. Rothman A. Johnson R.L. Fisher M. Xie J. Bonifas J.M. et al.Identification of mutations in the human PATCHED gene in sporadic basal cell carcinomas and in patients with the basal cell nevus syndrome.J Invest Dermatol. 1998; 110: 885-888Crossref PubMed Scopus (239) Google Scholar). More recently, we detected PTCH gene mutations in almost half (48% (29/60)) of a sampling of BCCs obtained from the general population (Heitzer et al., 2007Heitzer E. Lassacher A. Quehenberger F. Kerl H. Wolf P. UV fingerprints predominate in the PTCH mutation spectra of basal cell carcinomas independent of clinical phenotype.J Invest Dermatol. 2007https://doi.org/10.1038/sj.jid.5700923Abstract Full Text Full Text PDF Scopus (30) Google Scholar). This led us to examine the potential role of PTCH gene mutation in the molecular carcinogenesis of PUVA-associated BCCs. In brief, we analyzed the PTCH gene in paraffin-embedded tumor specimens from 8 of the 13 previously analyzed PUVA-associated BCCs mentioned above (Seidl et al., 2001Seidl H. Kreimer-Erlacher H. Back B. Soyer H.P. Hofler G. Kerl H. et al.Ultraviolet exposure as the main initiator of p53 mutations in basal cell carcinomas from psoralen and ultraviolet A-treated patients with psoriasis.J Invest Dermatol. 2001; 117: 365-370Crossref PubMed Scopus (40) Google Scholar). Tissue sections were manually macrodissected (i) to eliminate nontumor cells in tumor samples and (ii) to obtain tumor-adjacent normal tissue from each sample for control purposes. DNA from PTCH gene exons 2–23 and adjacent introns was amplified by PCR and sequenced as previously described (Heitzer et al., 2007Heitzer E. Lassacher A. Quehenberger F. Kerl H. Wolf P. UV fingerprints predominate in the PTCH mutation spectra of basal cell carcinomas independent of clinical phenotype.J Invest Dermatol. 2007https://doi.org/10.1038/sj.jid.5700923Abstract Full Text Full Text PDF Scopus (30) Google Scholar). The study was conducted according to the Declaration of Helsinki Principles. At the time when the study was performed, institutional approval was not necessary for it, according to Austrian laws and regulations. Those patients who were still alive gave their informed consent to DNA analysis of the tumor samples. Of the 8 BCCs analyzed, 5 (63%) contained a total of 19 mutations (that is, 9 missense, 1 nonsense, 7 silent exonic, and 2 intronic mutations) (Table 1). Four of those 5 BCCs had multiple mutations. Of the 19 mutations, 17 (89%) occurred at dipyrimidine sites, and 15 (79%) were C → T transitions. Eleven mutations (58%) unambiguously bore the UV fingerprint. Three mutations (16%) that occurred at a 5′TpG site (tumor C1, codon 72) or 5′TpT site (tumor A3, codon 388 and tumor C1, codon 83) unambiguously bore the PUVA fingerprint, and one (5%) was of other type, according to our previous definition (Wolf et al., 2004bWolf P. Kreimer-Erlacher H. Seidl H. Back B. Soyer H.P. Kerl H. The ultraviolet fingerprint dominates the mutational spectrum of the p53 and Ha-ras genes in psoralen+ultraviolet A keratoses from psoriasis patients.J Invest Dermatol. 2004; 122: 190-200Abstract Full Text Full Text PDF PubMed Scopus (18) Google Scholar). The remaining four mutations (21%) (tumor A1, codon 289; tumor A2, codon 415; tumor B2, codon 256; and tumor C1, codon 514) were of uncertain (UV or PUVA) origin, having occurred at a dipyrimidine opposite a possible psoralen-binding site (5′TpG). Comparison of DNA from tumor and adjacent normal tissue samples revealed that every specific mutation, whether silent or not, occurred only in tumor tissue, thus indicating that each mutation was somatic. Three mutations (tumor A1, codon 289; tumor A3, codon 388; and tumor B2, codon 293) in our study population occurred at PTCH mutation sites already entered in the PTCH data bank (http://www.cybergene.se/cgi-bin/w3-msql/ptchbase/index.html) but exhibited base changes different to those previously entered for the applicable mutation sites. The other detected mutations in our study were novel. Consistent with previous work regarding BCC, most (6 of 10) of the exonic nonsense or missense PTCH mutations in our study population were clustered in the extracellular loop (four mutations) or sterol-sensing domain (two mutations) (data not shown), regions shown to be functionally important in several previous studies (Heitzer et al., 2007Heitzer E. Lassacher A. Quehenberger F. Kerl H. Wolf P. UV fingerprints predominate in the PTCH mutation spectra of basal cell carcinomas independent of clinical phenotype.J Invest Dermatol. 2007https://doi.org/10.1038/sj.jid.5700923Abstract Full Text Full Text PDF Scopus (30) Google Scholar, and references cited therein). In addition, in tumor and normal tissue we detected a total of seven different polymorphisms (IVS11-51G/C, 1665T/C, 1686C/T, IVS15+9G/C, IVS16-80G/C, IVS17+21G/A, and 3944C/T or its combinations) (data not shown), which all had been previously described (Heitzer et al., 2007Heitzer E. Lassacher A. Quehenberger F. Kerl H. Wolf P. UV fingerprints predominate in the PTCH mutation spectra of basal cell carcinomas independent of clinical phenotype.J Invest Dermatol. 2007https://doi.org/10.1038/sj.jid.5700923Abstract Full Text Full Text PDF Scopus (30) Google Scholar).Table 1PTCH mutations in PUVA-associated BCCsTumor suppressor genePTCHp531These p53 data were previously reported (Seidl et al., 2001).Tumor2These tumor data were previously reported (Seidl et al., 2001). No material from tumors A4, D1, E2, E4, and E5 was available for this study, having been completely used up in the previous study by Seidl et al. (2001).Mutation statusExonic/intronic positionCodonCodon and flanking sequence3The sequence for the strand (transcribed or nontranscribed) containing a pyrimidine at the mutation site is shown in the 5′ → 3′ direction. Nucleotides of the affected codon are shown in capital letters. Mutated bases are shown in bold letters. Multi- and dipyrimidines bearing the UV fingerprint are underlined once; potential psoralen-binding sites (i.e., 5′TpG/5′CpA and 5′TpT/5ApA) containing mutations are underlined twice.Base changeAmino-acid changeStrand containing affected pyrimidine4T, transcribed strand containing an affected pyrimidine; NT, nontranscribed strand containing an affected pyrimidine.Mutation type5UV, UV fingerprint (C → T transition at dipyrimidine); PUVA fingerprint, mutation arising at potential psoralen-binding site (see footnote 3).Mutation statusA1Yes6289tCATgC → THis → TyrTUV/PUVAYes10461gGACtC → TNoneTUV10471gCTGgC → TNoneTUV231,344gGGCcC → TAla → ThrNTUVA2Yes9415cTCCaC → TNoneTUV/PUVAYesA3Yes2131cTTCcC → TGlu → LysNTUVYes8388cGTTcT → CAsn → AspNTPUVA191,099tCACgC → TNoneTOther231,423cCCTcC → TNoneNTUVB1NoNoB2Yes2100aCTTgC → TNoneNTUVNo6256tCCAcC → TTrp → StopNTUV/PUVA6293gGACcC → TNoneTUV10481cCACtC → TVal → MetNTUVIVS2+10—ccgcccC → T——UV211,163cGCCgC → TGly → AspNTUVC1Yes272tGGCcG → TGly → SerNTPUVANo283gTTTcT → CPhe → LeuTPUVAIVS10+61—GgccaC → T——UV11514cATCaC → TAsp → AsnNTUV/PUVAE1NoNoE3NoYesBCC, basal cell carcinoma; PTCH, patched; PUVA, psoralen plus UVA.1 These p53 data were previously reported (Seidl et al., 2001Seidl H. Kreimer-Erlacher H. Back B. Soyer H.P. Hofler G. Kerl H. et al.Ultraviolet exposure as the main initiator of p53 mutations in basal cell carcinomas from psoralen and ultraviolet A-treated patients with psoriasis.J Invest Dermatol. 2001; 117: 365-370Crossref PubMed Scopus (40) Google Scholar).2 These tumor data were previously reported (Seidl et al., 2001Seidl H. Kreimer-Erlacher H. Back B. Soyer H.P. Hofler G. Kerl H. et al.Ultraviolet exposure as the main initiator of p53 mutations in basal cell carcinomas from psoralen and ultraviolet A-treated patients with psoriasis.J Invest Dermatol. 2001; 117: 365-370Crossref PubMed Scopus (40) Google Scholar). No material from tumors A4, D1, E2, E4, and E5 was available for this study, having been completely used up in the previous study by Seidl et al., 2001Seidl H. Kreimer-Erlacher H. Back B. Soyer H.P. Hofler G. Kerl H. et al.Ultraviolet exposure as the main initiator of p53 mutations in basal cell carcinomas from psoralen and ultraviolet A-treated patients with psoriasis.J Invest Dermatol. 2001; 117: 365-370Crossref PubMed Scopus (40) Google Scholar.3 The sequence for the strand (transcribed or nontranscribed) containing a pyrimidine at the mutation site is shown in the 5′ → 3′ direction. Nucleotides of the affected codon are shown in capital letters. Mutated bases are shown in bold letters. Multi- and dipyrimidines bearing the UV fingerprint are underlined once; potential psoralen-binding sites (i.e., 5′TpG/5′CpA and 5′TpT/5ApA) containing mutations are underlined twice.4 T, transcribed strand containing an affected pyrimidine; NT, nontranscribed strand containing an affected pyrimidine.5 UV, UV fingerprint (C → T transition at dipyrimidine); PUVA fingerprint, mutation arising at potential psoralen-binding site (see footnote 3T, transcribed strand containing an affected pyrimidine; NT, nontranscribed strand containing an affected pyrimidine.). Open table in a new tab BCC, basal cell carcinoma; PTCH, patched; PUVA, psoralen plus UVA. We compared the mutational status of both PTCH and p53. Three tumors (A1, A2, and A3) bore mutations in both genes; two tumors (B2 and C1), only in PTCH; one tumor (E3), only in p53; and two tumors (B1 and E1), in neither gene (Table 1). We also compared the PTCH mutation spectra of our sample of PUVA-associated BCCs versus sporadic (presumably non-PUVA treated) BCCs from the general population. We found no significant difference between them (Fisher exact test, P>0.05) (Figure 1). Interestingly, the UV fingerprint predominated in both sets of BCCs. The prevalence of PTCH and p53 gene mutations in BCCs in this study (63 and 46%, respectively) is consistent with that reported by Zhang et al., 2001Zhang H. Ping X.L. Lee P.K. Wu X.L. Yao Y.J. Zhang M.J. et al.Role of PTCH and p53 genes in early-onset basal cell carcinoma.Am J Pathol. 2001; 158: 381-385Abstract Full Text Full Text PDF PubMed Scopus (70) Google Scholar in early-onset BCCs from the general population (54% (13/24) and 46% (11/24), respectively). Our mutational analyses are consistent with previous mutational analyses of other tumor suppressor genes and oncogenes in PUVA-associated skin cancers and precursor lesions, including p53 in BCC (Seidl et al., 2001Seidl H. Kreimer-Erlacher H. Back B. Soyer H.P. Hofler G. Kerl H. et al.Ultraviolet exposure as the main initiator of p53 mutations in basal cell carcinomas from psoralen and ultraviolet A-treated patients with psoriasis.J Invest Dermatol. 2001; 117: 365-370Crossref PubMed Scopus (40) Google Scholar) and p53, Ha-ras, and INK4a-ARF in squamous cell carcinoma or PUVA keratoses (Nataraj et al., 1997Nataraj A.J. Wolf P. Cerroni L. Ananthaswamy H.N. p53 mutation in squamous cell carcinomas from psoriasis patients treated with psoralen+UVA (PUVA).J Invest Dermatol. 1997; 109: 238-243Crossref PubMed Scopus (62) Google Scholar; Wang et al., 1997Wang X.M. McNiff J.M. Klump V. Asgari M. Gasparro F.P. An unexpected spectrum of p53 mutations from squamous cell carcinomas in psoriasis patients treated with PUVA.Photochem Photobiol. 1997; 66: 294-299Crossref PubMed Scopus (34) Google Scholar; Kreimer-Erlacher et al., 2001Kreimer-Erlacher H. Seidl H. Back B. Kerl H. Wolf P. High mutation frequency at Ha-ras exons 1–4 in squamous cell carcinomas from PUVA-treated psoriasis patients.Photochem Photobiol. 2001; 74: 323-330Crossref PubMed Scopus (33) Google Scholar, Kreimer-Erlacher et al., 2003Kreimer-Erlacher H. Seidl H. Back B. Cerroni L. Kerl H. Wolf P. High frequency of ultraviolet mutations at the INK4a-ARF locus in squamous cell carcinomas from psoralen-plus-ultraviolet-A-treated psoriasis patients.J Invest Dermatol. 2003; 120: 676-682Crossref PubMed Scopus (33) Google Scholar; Seidl et al., 2001Seidl H. Kreimer-Erlacher H. Back B. Soyer H.P. Hofler G. Kerl H. et al.Ultraviolet exposure as the main initiator of p53 mutations in basal cell carcinomas from psoralen and ultraviolet A-treated patients with psoriasis.J Invest Dermatol. 2001; 117: 365-370Crossref PubMed Scopus (40) Google Scholar; Stern et al., 2002Stern R.S. Bolshakov S. Nataraj A.J. Ananthaswamy H.N. p53 mutation in nonmelanoma skin cancers occurring in psoralen ultraviolet a-treated patients: evidence for heterogeneity and field cancerization.J Invest Dermatol. 2002; 119: 522-526Abstract Full Text Full Text PDF PubMed Scopus (68) Google Scholar; Wolf et al., 2004bWolf P. Kreimer-Erlacher H. Seidl H. Back B. Soyer H.P. Kerl H. The ultraviolet fingerprint dominates the mutational spectrum of the p53 and Ha-ras genes in psoralen+ultraviolet A keratoses from psoriasis patients.J Invest Dermatol. 2004; 122: 190-200Abstract Full Text Full Text PDF PubMed Scopus (18) Google Scholar). In all those studies, UV fingerprints and 5′TpG mutations dominated the mutation spectra, whereas 5′TpA mutations (that is, the most typical psoralen photoadducts and PUVA-induced mutations in cell culture (Monti et al., 2000Monti P. Inga A. Aprile A. Campomenosi P. Menichini P. Ottaggio L. et al.p53 mutations experimentally induced by 8-methoxypsoralen plus UVA (PUVA) differ from those found in human skin cancers in PUVA-treated patients.Mutagenesis. 2000; 15: 127-132Crossref PubMed Scopus (12) Google Scholar) and animal studies (Nataraj et al., 1996Nataraj A.J. Black H.S. Ananthaswamy H.N. Signature p53 mutation at DNA cross-linking sites in 8-methoxypsoralen and ultraviolet A (PUVA)-induced murine skin cancers.Proc Natl Acad Sci USA. 1996; 93: 7961-7965Crossref PubMed Scopus (61) Google Scholar)) were comparatively rare. This predominance of UV fingerprint mutations may have been due to UVB and/or natural sunlight exposure, which is known to benefit psoriatic skin lesions (Seidl et al., 2001Seidl H. Kreimer-Erlacher H. Back B. Soyer H.P. Hofler G. Kerl H. et al.Ultraviolet exposure as the main initiator of p53 mutations in basal cell carcinomas from psoralen and ultraviolet A-treated patients with psoriasis.J Invest Dermatol. 2001; 117: 365-370Crossref PubMed Scopus (40) Google Scholar). Indeed, all patients with PUVA-associated BCCs in this study also had a history of UVB therapy (Seidl et al., 2001Seidl H. Kreimer-Erlacher H. Back B. Soyer H.P. Hofler G. Kerl H. et al.Ultraviolet exposure as the main initiator of p53 mutations in basal cell carcinomas from psoralen and ultraviolet A-treated patients with psoriasis.J Invest Dermatol. 2001; 117: 365-370Crossref PubMed Scopus (40) Google Scholar). However, the prominence of 5′TpG mutations particularly in squamous cell carcinoma is also consistent with the results of a laboratory study (Gunther et al., 1995Gunther E.J. Yeasky T.M. Gasparro F.P. Glazer P.M. Mutagenesis by 8-methoxypsoralen and 5-methylangelicin photoadducts in mouse fibroblasts: mutations at cross-linkable sites induced by offoadducts as well as cross-links.Cancer Res. 1995; 55: 1283-1288PubMed Google Scholar) in which a third of all mutations induced in supF-containing murine fibroblasts by low (but clinically relevant) PUVA doses occurred at 5′TpG sequences. Conversely, the similar frequency of 5′TpG mutations in both PUVA-associated and non-PUVA-associated BCCs (Figure 1) suggests that those mutations might have been caused by agents (yet unidentified) other than PUVA. Together, our results argue—at least in the case of PUVA-associated BCCs—against the controversial theory that multiple BCCs arising in a single individual are monoclonal in origin (Walsh et al., 1998Walsh D.S. Peacocke M. Harrington A. James W.D. Tsou H.C. Patterns of X chromosome inactivation in sporadic basal cell carcinomas: evidence for clonality.J Am Acad Dermatol. 1998; 38: 49-55Abstract Full Text Full Text PDF PubMed Scopus (11) Google Scholar; Saldanha et al., 2002Saldanha G. Shaw J.A. Fletcher A. Evidence that superficial basal cell carcinoma is monoclonal from analysis of the Ptch1 gene locus.Br J Dermatol. 2002; 147: 931-935Crossref PubMed Scopus (17) Google Scholar; Shulman et al., 2006Shulman O. Laitman Y. Vilan A. Leviav A. Friedman E. Monoclonal origin of anatomically distinct basal cell carcinomas.J Invest Dermatol. 2006; 126: 676-679Abstract Full Text Full Text PDF PubMed Scopus (13) Google Scholar; Van Steensel and Frank, 2006Van Steensel M.A. Frank J. Monoclonal origin of anatomically distinct basal cell carcinomas: is there really hard evidence at hand?.J Invest Dermatol. 2006; 126 (author reply 2729–2730): 2727-2729Crossref PubMed Scopus (2) Google Scholar). For example, Shulman et al., 2006Shulman O. Laitman Y. Vilan A. Leviav A. Friedman E. Monoclonal origin of anatomically distinct basal cell carcinomas.J Invest Dermatol. 2006; 126: 676-679Abstract Full Text Full Text PDF PubMed Scopus (13) Google Scholar inferred from loss of heterozygosity analyses and X-chromosome inactivation studies of multiple BCCs from single patients that most of the lesions originated from a single tumor cell clone, independent of the anatomical site and time of occurrence. Our analysis of the PTCH mutations in two individuals with multiple BCCs suggests otherwise (Table 1). Three lesions from one individual (A1–A3) bore distinctly different PTCH mutations. Two lesions from another individual differed in that one bore no PTCH mutations (B1) and the other bore three diverse mutations (B2), nor did our previous p53 sequencing analyses (Seidl et al., 2001Seidl H. Kreimer-Erlacher H. Back B. Soyer H.P. Hofler G. Kerl H. et al.Ultraviolet exposure as the main initiator of p53 mutations in basal cell carcinomas from psoralen and ultraviolet A-treated patients with psoriasis.J Invest Dermatol. 2001; 117: 365-370Crossref PubMed Scopus (40) Google Scholar) give any indication of BCC monoclonality, as evidenced by a diversity of p53 mutations in four lesions from patient A and in five lesions from patient E. As others have already noted (Van Steensel and Frank, 2006Van Steensel M.A. Frank J. Monoclonal origin of anatomically distinct basal cell carcinomas: is there really hard evidence at hand?.J Invest Dermatol. 2006; 126 (author reply 2729–2730): 2727-2729Crossref PubMed Scopus (2) Google Scholar), this in turn suggests that DNA sequencing analysis of BCCs from the general population (like that of PUVA-associated BCCs reported here) might help resolve the controversy surrounding monoclonality. The authors state no conflict of interest. This work was supported by Austrian National Bank Jubilee Fund nos. 9740 and 11729.
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