The susceptibility CDKN2 locus may have a role on prognosis of melanoma patients
Authors: M. Casula, M. Budroni, A. Cossu, P.A. Ascierto, N. Mozzillo, S. Canzanella, A. Muggiano, G. Palmieri
Journal: Annals of Oncology (2010)

Recently, a multimarker prognostic assay has been correlated with overall survival in melanoma patients [1.Rothberg B.E.G. Berger A.J. Molinaro A.M. et al.Melanoma prognostic model using tissue microarrays and genetic algorithms.J Clin Oncol. 2009; 27: 5772-5780Crossref PubMed Scopus (78) Google Scholar]. Such an assay was based on detection of the expression levels of proteins involved in melanoma pathogenesis; among few candidates, an increased nuclear expression of the p16CDKN2A protein was described to significantly improve prognosis in melanoma [1.Rothberg B.E.G. Berger A.J. Molinaro A.M. et al.Melanoma prognostic model using tissue microarrays and genetic algorithms.J Clin Oncol. 2009; 27: 5772-5780Crossref PubMed Scopus (78) Google Scholar] (probably, reflecting the established role for p16CDKN2A in inducing inhibition of aberrant cell proliferation in melanocytic cells [2.Palmieri G. Casula M. Sini M.C. et al.Issues affecting molecular staging in the management of patients with melanoma.J Cell Mol Med. 2007; 11: 1052-1068Crossref PubMed Scopus (25) Google Scholar]). Moreover, an elevated p16CDKN2A expression has been reported to be protective for disease-specific mortality among melanoma patients [3.Rothberg B.E.G. Bracken M.B. Rimm D.L. Tissue biomarkers for prognosis in cutaneous melanoma: a systematic review and meta-analysis.J Natl Cancer Inst. 2009; 101: 452-474Crossref PubMed Scopus (144) Google Scholar]. Consistently, allelic losses in p16CDKN2A gene and subsequent impairment of p16CDKN2A protein expression have been demonstrated to contribute to melanoma progression [2.Palmieri G. Casula M. Sini M.C. et al.Issues affecting molecular staging in the management of patients with melanoma.J Cell Mol Med. 2007; 11: 1052-1068Crossref PubMed Scopus (25) Google Scholar] as well as to correlate with a shorter overall survival in different tumor types (including melanoma) [4.Grafstrom E. Egyhazi S. Ringborg U. et al.Biallelic deletions in INK4 in cutaneous melanoma are common and associated with decreased survival.Clin Cancer Res. 2005; 11: 2991-2997Crossref PubMed Scopus (48) Google Scholar]. To date, a correct measurement of the p16CDKN2A alleles in melanoma tissues cannot be considered as a reliable and reproducible approach for clinical applications.Transition from expression markers (whose classification is quantitative or semiquantitative, depending on subjective evaluation of both intensity and distribution of immunohistochemical staining) to genetic markers (whose assessment is qualitative, detecting the objective occurrence of each specific sequence variant) is therefore largely awaited.Toward the characterization of a genetic profile with prognostic value, the CDKN2 locus at chromosome 9p21, harboring the CDKN2A and CDKN2B genes, may represent the main candidate genomic region to be investigated in melanoma. To determine whether a genotype of single-nucleotide polymorphisms (SNPs) within the CDKN2 locus may correlate with the melanoma outcome, we analyzed nine SNPs (Figure 1A) jointly by logistic regression among 396 melanoma patients and 383 healthy controls originating from south Italy. Disease stage (according to the American Joint Committee on Cancer criteria) was defined by medical records and pathology reports. Three hundred twenty-five (82%) of the 396 patients presented localized disease [stages IA (107, 27%), IB (55, 14%), IIA (127, 32%), and IIB (36, 9%)] and 71 (18%) had regional nodal involvement (stage III); no patient with metastatic disease (stage IV) was included into the study.Among all analyzed genotypes, coexistence of T/T genotype in three SNPs spanning the coding exon 1α (rs2811710), the first intron (rs2518720), and the 5′ regulatory DNA (rs2811708) of p16CDKN2A was the only genetic combination significantly associated with melanoma [P < 0.0001, odds ratio 5.63, 95% confidence interval (CI) 2.96–10.7] (Figure 1B).After a median follow-up of 68 months (range 13–212 months), patients carrying the rs2811710–rs2518720–rs2811708 T/T genotype presented a lower overall survival in comparison with those carrying different genetic combinations (Figure 1C). Using the Cox model for a multivariate analysis, the disease stage [P < 0.001, hazard ratio (HR) 2.05, 95% CI 1.43–2.98] and the presence of the rs2811710–rs2518720–rs2811708 T/T genotype (P = 0.047, HR 1.54, 95% CI 1.17–1.91) remained the parameters with a significant impact on prognosis in our series (Figure 1D).If confirmed in other populations, such a polymorphic pattern might become a useful marker that simultaneously mediates susceptibility and prognosis in melanoma. The advent of large-scale genome-wide association studies has resulted in the identification of many susceptibility loci for melanoma [5.Pharoah P.D.P. Shedding light on skin cancer.Nat Genet. 2009; 40: 817-818Crossref Scopus (9) Google Scholar]. As a consequence, future correlations between molecular signatures and clinical outcome will provide even more reliable tools for improving characterization of molecular biomarkers that may predict prognosis and response to treatment in patients with melanoma.fundingItalian Ministry of University and Research . Recently, a multimarker prognostic assay has been correlated with overall survival in melanoma patients [1.Rothberg B.E.G. Berger A.J. Molinaro A.M. et al.Melanoma prognostic model using tissue microarrays and genetic algorithms.J Clin Oncol. 2009; 27: 5772-5780Crossref PubMed Scopus (78) Google Scholar]. Such an assay was based on detection of the expression levels of proteins involved in melanoma pathogenesis; among few candidates, an increased nuclear expression of the p16CDKN2A protein was described to significantly improve prognosis in melanoma [1.Rothberg B.E.G. Berger A.J. Molinaro A.M. et al.Melanoma prognostic model using tissue microarrays and genetic algorithms.J Clin Oncol. 2009; 27: 5772-5780Crossref PubMed Scopus (78) Google Scholar] (probably, reflecting the established role for p16CDKN2A in inducing inhibition of aberrant cell proliferation in melanocytic cells [2.Palmieri G. Casula M. Sini M.C. et al.Issues affecting molecular staging in the management of patients with melanoma.J Cell Mol Med. 2007; 11: 1052-1068Crossref PubMed Scopus (25) Google Scholar]). Moreover, an elevated p16CDKN2A expression has been reported to be protective for disease-specific mortality among melanoma patients [3.Rothberg B.E.G. Bracken M.B. Rimm D.L. Tissue biomarkers for prognosis in cutaneous melanoma: a systematic review and meta-analysis.J Natl Cancer Inst. 2009; 101: 452-474Crossref PubMed Scopus (144) Google Scholar]. Consistently, allelic losses in p16CDKN2A gene and subsequent impairment of p16CDKN2A protein expression have been demonstrated to contribute to melanoma progression [2.Palmieri G. Casula M. Sini M.C. et al.Issues affecting molecular staging in the management of patients with melanoma.J Cell Mol Med. 2007; 11: 1052-1068Crossref PubMed Scopus (25) Google Scholar] as well as to correlate with a shorter overall survival in different tumor types (including melanoma) [4.Grafstrom E. Egyhazi S. Ringborg U. et al.Biallelic deletions in INK4 in cutaneous melanoma are common and associated with decreased survival.Clin Cancer Res. 2005; 11: 2991-2997Crossref PubMed Scopus (48) Google Scholar]. To date, a correct measurement of the p16CDKN2A alleles in melanoma tissues cannot be considered as a reliable and reproducible approach for clinical applications. Transition from expression markers (whose classification is quantitative or semiquantitative, depending on subjective evaluation of both intensity and distribution of immunohistochemical staining) to genetic markers (whose assessment is qualitative, detecting the objective occurrence of each specific sequence variant) is therefore largely awaited. Toward the characterization of a genetic profile with prognostic value, the CDKN2 locus at chromosome 9p21, harboring the CDKN2A and CDKN2B genes, may represent the main candidate genomic region to be investigated in melanoma. To determine whether a genotype of single-nucleotide polymorphisms (SNPs) within the CDKN2 locus may correlate with the melanoma outcome, we analyzed nine SNPs (Figure 1A) jointly by logistic regression among 396 melanoma patients and 383 healthy controls originating from south Italy. Disease stage (according to the American Joint Committee on Cancer criteria) was defined by medical records and pathology reports. Three hundred twenty-five (82%) of the 396 patients presented localized disease [stages IA (107, 27%), IB (55, 14%), IIA (127, 32%), and IIB (36, 9%)] and 71 (18%) had regional nodal involvement (stage III); no patient with metastatic disease (stage IV) was included into the study. Among all analyzed genotypes, coexistence of T/T genotype in three SNPs spanning the coding exon 1α (rs2811710), the first intron (rs2518720), and the 5′ regulatory DNA (rs2811708) of p16CDKN2A was the only genetic combination significantly associated with melanoma [P < 0.0001, odds ratio 5.63, 95% confidence interval (CI) 2.96–10.7] (Figure 1B). After a median follow-up of 68 months (range 13–212 months), patients carrying the rs2811710–rs2518720–rs2811708 T/T genotype presented a lower overall survival in comparison with those carrying different genetic combinations (Figure 1C). Using the Cox model for a multivariate analysis, the disease stage [P < 0.001, hazard ratio (HR) 2.05, 95% CI 1.43–2.98] and the presence of the rs2811710–rs2518720–rs2811708 T/T genotype (P = 0.047, HR 1.54, 95% CI 1.17–1.91) remained the parameters with a significant impact on prognosis in our series (Figure 1D). If confirmed in other populations, such a polymorphic pattern might become a useful marker that simultaneously mediates susceptibility and prognosis in melanoma. The advent of large-scale genome-wide association studies has resulted in the identification of many susceptibility loci for melanoma [5.Pharoah P.D.P. Shedding light on skin cancer.Nat Genet. 2009; 40: 817-818Crossref Scopus (9) Google Scholar]. As a consequence, future correlations between molecular signatures and clinical outcome will provide even more reliable tools for improving characterization of molecular biomarkers that may predict prognosis and response to treatment in patients with melanoma. fundingItalian Ministry of University and Research . Italian Ministry of University and Research .