Analysis of somatic mutations in braf, CDKN2A/p16 and PI3KCA in patients with medullary thyroid carcinoma
- Authors:
- Published online on: December 29, 2015 https://doi.org/10.3892/mmr.2015.4731
- Pages: 1653-1660
Abstract
Introduction
Medullary thyroid carcinoma (MTC), a neuroendocrine tumor originating from thyroid parafollicular cells, accounts for ~4% of thyroid cancer cases (1). The majority are sporadic cases, however, 20-25% occur as a hereditary syndrome termed multiple endocrine neoplasia type 2 (MEN 2A and MEN 2B) and as familial MTC, both of which are associated with germline mutations in the RET oncogene (2).
Mutations in the RET oncogene have previously been identified in the tumor tissue of up to 64% of sporadic MTC cases (3). In addition, RAS gene mutations are observed in 10% of RET-negative cases and are associated with a subset of tumors with less aggressive behavior (4). While certain studies identified that ~90% of sporadic MTCs exhibited mutually exclusive mutations in RET, HRAS and KRAS (4–8), Moura et al (3) reported the presence of the RAS mutation in one case with RET-positive sporadic MTC and Rapa et al (9) identified no RAS mutations in 49 examined cases. Nevertheless, the clinical phenotype of sporadic and inherited MTCs is heterogeneous even in the presence of the same mutation; however the molecular mechanisms underlying the pathology remain to be fully elucidated.
In addition, it remains unclear whether there is a modulatory role in MTC tumor progression for additional genes such as BRAF, CDKN2A and PI3KCA. These genes participate in the tumorigenesis of several types of human malignancies such as tumors derived from neural crest cells, including melanoma, pheochromocytoma and paraganglioma (10–12).
BRAF, like RET and RAS, is involved in the mitogen-activated protein kinase pathway and has a well-established role in the pathogenesis of malignancies such as melanoma and papillary thyroid cancer (13). Nevertheless, the contribution in the tumorigenesis of MTC remains controversial. A previous study reported a high prevalence of the p.Val600Glu BRAF mutation in sporadic MTC cases (14); however, subsequent studies did not confirm this observation (3,9,15,16).
An additional tumor suppressor gene, CDKN2A/p16INK4A, is involved in the G1/S transition in the cell cycle. Mutations and deletions have been identified in melanoma, and polymorphisms in its 3′ untranslated region (UTR) have been associated with earlier progression from primary to metastatic disease (17). By contrast, polymorphisms in another tumor suppressor gene, CDKN1B, which is in the same CDKN family, are associated with improved outcomes (18).
Additionally, PI3KCA is a gene that serves an important role in signaling pathways and cell growth, and contributes to tumorigenesis in several types of human malignancy (19,20). However, the role of this gene in the tumorigenesis of MTC remains to be fully understood.
Therefore, the current study aimed to verify the prevalence of somatic mutations in BRAF, CDKN2A and PI3KCA, which have already been described in other neural crest-derived tumors, and to determine the possible supporting role of these genes in the tumorigenesis of MTC.
Patients and methods
Patients and tissue samples
From 128 patients with MTC assessed at the Multiple Endocrine Neoplasia outpatient clinic at the Universidade Federal de Sao Paulo (Sao Paulo, Brazil) between February 2007 and June 2013, formalin-fixed paraffin-embedded (FFPE) tumor tissues were selected from 31 patients on the basis of the availability of tumor tissues, with no other selection criteria. DNA extraction was subsequently performed, using an in-house method as previously described (21). Subsequent to DNA extraction, 20 samples (from 13 males and 7 females; mean age, 40.55±16.74 years) provided the appropriate quantity and quality of DNA. The study was approved by the Ethics and Research Committee of the Universidade Federal de Sao Paulo (protocol number 1945/10), and all patients provided informed consent. Additionally, 1,092 genotypes of variant frequencies (single nucleotide polymorphisms; SNPs) were obtained from the 1000 Genomes database (http://www.1000genomes.org/) as a population genetics control.
DNA extraction and genotyping
DNA from peripheral blood and somatic DNA from 10-µm sections of FFPE MTC tissues was extracted using an in-house method as previously described (21). Polymerase chain reaction (PCR) was performed to amplify DNA corresponding to hotspot exons 2, 3 and 4 of HRAS; 2, 3 and 4 of KRAS; 2 and 3 of NRAS; 15 of BRAF; 9 and 20 of PI3KCA; and exons 2, 3 and the 3′UTR of the CDKN2A gene. The sequences of the primers are listed in Table I. The reactions were performed using 10 pM of each specific primer, 2.5 µl PCR buffer, 200 µM dNTP, 1.5 µM MgCl2 and 0.2 units Taq DNA polymerase (Invitrogen; Thermo Fisher Scientific, Waltham, MA, USA) in a 25-µl total reaction volume. The cycling conditions were as follows: 5 min at 95°C, 38 cycles of 45 sec at 95°C, 45 sec for annealing and 1 min at 72°C, and a final elongation for 10 min at 72°C. The PCR products were purified using the Illustra GFX PCR DNA and Gel Purification kit (GE Healthcare Life Sciences, Chalfont, UK) and were subject to sequencing using the Sanger method, with the Big Dye™ Terminator Cycle Sequencing Ready Reaction kit and the ABI PRISM 3130xl Genetic Analyzer (Applied Biosystems; Thermo Fisher Scientific). Gel electrophoresis of the PCR products was performed to analyze product quality and yield using a 1.8% agarose gel and a DNA ladder.
In silico analysis of HRAS mutations and CDKN2A polymorphisms
Mutational analysis of HRAS was performed by the use of Project HOPE to obtain structural information from the analysis of PDB-file 1CTQ (22). The in silico analysis for the CDKN2A polymorphisms was performed using the Functional Single Nucleotide Polymorphism database (http://compbio.cs.queensu.ca/F-SNP/) as previously described (23). This database provides information regarding potential deleterious effects of SNPs with respect to splicing, transcription, translation and post-translation based on SNP functional significance (FS). The FS score for neutral SNPs is 0.1764, whereas the FS score for disease-associated SNPs is in the range of 0.5-1.
Statistical analysis
The allele and genotype frequencies were compared between patients with MTC and the 1000 Genomes database controls using a χ2 test. The clinicopathological features of patients carrying each of the polymorphisms rs11515 and rs3088440 were compared with those of patients without such polymorphisms using the χ2 test or the Student's unpaired t-test as appropriate. P<0.05 was considered to indicate a statistically significant difference, and the Hardy-Weinberg equilibrium was evaluated. Statistical analyses were performed using SPSS, version 22.0 (IBM SPSS, Armonk, NY, USA) and GraphPad Prism, version 3.0 (GraphPad Software, Inc., La Jolla, CA, USA).
Results
Screening of the RET, HRAS, KRAS and NRAS genes
Mutational screening of the RET gene was performed on all 20 patients. A total of 10 cases were identified to be familial tumors as confirmed by the presence of a germline mutation. In total, 30% of the sporadic cases (3/10) presented with a RET somatic mutation. The clinicopathological features and molecular analysis, including tumor staging based on the American Joint Committee in Cancer staging system (24), are summarized in Table II.
To investigate exclusive causative mutations in cases of sporadic MTC other than RET mutations, HRAS, KRAS and NRAS were screened for somatic mutations in the hotspots. The majority of these patients had been previously analyzed for RET germline mutations as part of our routine evaluation, and for RET somatic mutations in a previous study (25) Two novel HRAS mutations, p.Asp33Asn and p.His94Tyr, were detected in RET-negative MTC tumors. Mutational analysis using Project HOPE suggests that the p.His94Tyr mutation is deleterious, and that the p.Asp33Asn mutation is likely to be damaging (Fig. 1). No differences in the clinical presentation or histological observations were noted between patients with MTC that had a mutation in the RAS gene (Table II).
No somatic mutations were identified in exon 15 of BRAF or in exons 9 and 20 of PI3KCA. Patient 9 was not analyzed for somatic mutations in PI3KCA due to an insufficient number of tumor samples.
Despite not having identified somatic mutations in CDKN2A hotspots, two polymorphisms in the 3′UTR regulatory region, 500 C→G (rs11515) and 540 C→T (rs3088440), were identified in the patients observed. The heterozygotic pattern of the two SNPs was observed in the same proportion, 7/20 MTC (35%). The genotype distribution was identified to be in the Hardy-Weinberg equilibrium and was not identified to exhibit linkage disequilibrium. To investigate whether the observed polymorphisms were limited to a somatic event, they were further analyzed in the peripheral blood, which confirmed germline inheritance. The in silico analysis demonstrated that the CDKN2A polymorphisms rs11515 and rs3088440 are located in the transcriptional regulatory region and that the nucleotide alterations may affect the binding of transcription factors.
In seven cases, it was possible to detect the presence of these polymorphisms in the secondary tumors in the lymph nodes (tumor metastases), however no differences between the genotypes of the primary and secondary tumors were observed, indicating that there was no additional somatic event in CDKN2A involved in the metastatic process. This analysis was additionally performed for BRAF and PI3KCA in metastatic tissues.
No associations between the polymorphisms and the clinicopathological features observed were identified (Table III). In addition, the frequency of the SNPs was compared with a population genetics control, and there was no significant difference between the two populations (Table IV).
Table IVComparative analysis of the frequency of the non-coding CDKN2A germ line single nucleotide polymorphisms in patients with MTC and the control. |
Discussion
The adjuvant role of additional genes in the tumorigenesis of MTC was investigated in the current study through analysis of tumor tissues from 20 patients. Screening in hotspot regions of BRAF, CDKN2A and PI3KCA did not identify any somatic mutations in the coding region. In addition, the results of the current study were not in agreement with the BRAF mutation frequency of 68.2% observed by Goutas et al (14). This suggests that BRAF does not serve an important role in the tumorigenesis of MTC. The observations of the current study concerning MTC are consistent with a previous study that demonstrated that somatic mutations in genes other than RET and RAS are very rare or even absent (5). Notably, the present study identified two novel HRAS mutations.
Additionally, two common polymorphisms in the 3′-UTR non-coding region of the gene CDKN2A were identified, rs11515 and rs3088440 (26). It is known that protein synthesis can be modulated by regulatory elements located in the 5′-UTR and 3′-UTR regions. The 3′-UTR, the site of the polymorphisms identified in the current study, serves an important role in translation and mRNA stability. Alterations in this region may be associated with the onset or progression of disease (27).
These polymorphisms have been investigated in various tumor types including urinary bladder neoplasm (28), esophageal adenocarcinoma (29) and cervical cancer (30) as presented in Table V. The two identified polymorphisms have been previously associated with an earlier progression from primary to metastatic disease in the case of melanoma (17), and rs3088440 was associated with the mechanism of tumor invasion in bladder cancer (28). Controversially, this polymorphism has been previously associated with a sub-group with reduced vertical growth of melanoma and a favorable outcome (31). However, additional studies have not identified a clinical correlation with tumor behavior (30,32,33).
Using in silico analysis, the current study identified that the polymorphisms rs11515 and rs3088440 are located within a transcriptional regulatory region, and the alteration of nucleotides can affect the binding of potential transcriptional factors. For example, the presence of the C allele in rs3088440 favors the binding of the transcription factor c-Myb, which potentially results in the transcriptional repression of the CDKN2A gene, compromising its normal function in cell cycle control (42). However, no association was identified between this polymorphism and the clinicopathological parameters investigated in the cohort studied (Table III).
In conclusion, it is suggested that BRAF, CDKN2A and PI3KCA, listed as potential adjuvants in the tumorigenesis of MTC, do not participate through somatic mutations as modulators of oncogenesis. To the best of our knowledge, the current study is the first to investigate these two CDKN2A polymorphisms in the pathophysiology of MTC. Therefore, CDKN2A and its regulatory regions and the additional genes involved in tumorigenesis warrant further investigation in MTC.
Acknowledgments
The authors would like to thank the team of the Laboratory of Molecular and Translational Endocrinology, particularly Ms. Teresa Kasamatsu, Mr. Gilberto Furuzawa, Dr João Roberto Martins, Dr Ji Hoon Yang, Dr Fausto Germano Neto and Mr. Fernando Soares. The authors would additionally like to acknowledge Mr. Gilmar Miranda from Siratec Ltd. for graphic art design. The current study was supported grants from the Sao Paulo State Research Foundation (grant nos. 2012/11036-3, 2012/02465-8, 2012/01628-0, 2009/50575-4, 2012/00079-3 and 2011/20747-8).
References
American Thyroid Association Guidelines Task Force; Kloos RT, Eng C, Evans DB, Francis GL, Gagel RF, Gharib H, Moley JF, Pacini F and Ringel MD: Medullary thyroid cancer: Management guidelines of the American thyroid association. Thyroid. 19:565–612. 2009. View Article : Google Scholar : PubMed/NCBI | |
Nosé V: Familial thyroid cancer: A review. Mod Pathol. 24(Suppl 2): S19–S33. 2011. View Article : Google Scholar : PubMed/NCBI | |
Moura MM, Cavaco BM, Pinto AE and Leite V: High prevalence of RAS mutations in RET-negative sporadic medullary thyroid carcinomas. J Clin Endocrinol Metab. 96:E863–E868. 2011. View Article : Google Scholar : PubMed/NCBI | |
Ciampi R, Mian C, Fugazzola L, Cosci B, Romei C, Barollo S, Cirello V, Bottici V, Marconcini G, Rosa PM, et al: Evidence of a low prevalence of RAS mutations in a large medullary thyroid cancer series. Thyroid. 23:50–57. 2013. View Article : Google Scholar | |
Agrawal N, Jiao Y, Sausen M, Leary R, Bettegowda C, Roberts NJ, Bhan S, Ho AS, Khan Z, Bishop J, et al: Exomic sequencing of medullary thyroid cancer reveals dominant and mutually exclusive oncogenic mutations in RET and RAS. J Clin Endocrinol Metab. 98:E364–E369. 2013. View Article : Google Scholar : | |
Tamburrino A, Molinolo AA, Salerno P, Chernock RD, Raffeld M, Xi L, Gutkind JS, Moley JF, Wells SA Jr and Santoro M: Activation of the mTOR pathway in primary medullary thyroid carcinoma and lymph node metastases. Clin Cancer Res. 18:3532–3540. 2012. View Article : Google Scholar : PubMed/NCBI | |
Simbolo M, Mian C, Barollo S, Fassan M, Mafficini A, Neves D, Scardoni M, Pennelli G, Rugge M, Pelizzo MR, et al: High-throughput mutation profiling improves diagnostic stratification of sporadic medullary thyroid carcinomas. Virchows Arch. 465:73–78. 2014. View Article : Google Scholar : PubMed/NCBI | |
Puppin C, Durante C, Sponziello M, Verrienti A, Pecce V, Lavarone E, Baldan F, Campese AF, Boichard A, Lacroix L, et al: Overexpression of genes involved in miRNA biogenesis in medullary thyroid carcinomas with RET mutation. Endocrine. 47:528–536. 2014. View Article : Google Scholar : PubMed/NCBI | |
Rapa I, Saggiorato E, Giachino D, Palestini N, Orlandi F, Papotti M and Volante M: Mammalian target of rapamycin pathway activation is associated to RET mutation status in medullary thyroid carcinoma. J Clin Endocrinol Metab. 96:2146–2153. 2011. View Article : Google Scholar : PubMed/NCBI | |
Berrocal A, Cabañas L, Espinosa E, Fernández-de-Misa R, Martín-Algarra S, Martínez-Cedres JC, Ríos-Buceta L and Rodríguez-Peralto JL: Melanoma: Diagnosis, staging and treatment. Consensus group recommendations. Adv Ther. 31:945–960. 2014. View Article : Google Scholar : PubMed/NCBI | |
Muscarella P, Bloomston M, Brewer AR, Mahajan A, Frankel WL, Ellison EC, Farrar WB, Weghorst CM and Li J: Expression of the p16INK4A/Cdkn2a gene is prevalently downregulated in human pheochromocytoma tumor specimens. Gene Expr. 14:207–216. 2008. View Article : Google Scholar : PubMed/NCBI | |
Güran S and Tali ET: p53 and p16INK4A mutations during the progression of glomus tumor. Pathol Oncol Res. 5:41–45. 1999. View Article : Google Scholar : PubMed/NCBI | |
Nikiforova MN, Kimura ET, Gandhi M, Biddinger PW, Knauf JA, Basolo F, Zhu Z, Giannini R, Salvatore G, Fusco A, et al: BRAF mutations in thyroid tumors are restricted to papillary carcinomas and anaplastic or poorly differentiated carcinomas arising from papillary carcinomas. J Clin Endocrinol Metab. 88:5399–5404. 2003. View Article : Google Scholar : PubMed/NCBI | |
Goutas N, Vlachodimitropoulos D, Bouka M, Lazaris AC, Nasioulas G and Gazouli M: BRAF and K-RAS mutation in a Greek papillary and medullary thyroid carcinoma cohort. Anticancer Res. 28:305–308. 2008.PubMed/NCBI | |
Schulten HJ, Al-Maghrabi J, Al-Ghamdi K, Salama S, Al-Muhayawi S, Chaudhary A, Hamour O, Abuzenadah A, Gari M and Al-Qahtani M: Mutational screening of RET, HRAS, KRAS, NRAS, BRAF, AKT1 and CTNNB1 in medullary thyroid carcinoma. Anticancer Res. 31:4179–4183. 2011.PubMed/NCBI | |
Boichard A, Croux L, Al Ghuzlan A, Broutin S, Dupuy C, Leboulleux S, Schlumberger M, Bidart JM and Lacroix L: Somatic RAS mutations occur in a large proportion of sporadic RET-negative medullary thyroid carcinomas and extend to a previously unidentified exon. J Clin Endocrinol Metab. 97:E2031–E2035. 2012. View Article : Google Scholar : PubMed/NCBI | |
Sauroja I, Smeds J, Vlaykova T, Kumar R, Talve L, Hahka-Kemppinen M, Punnonen K, Jansèn CT, Hemminki K and Pyrhönen S: Analysis of G(1)/S checkpoint regulators in metastatic melanoma. Genes Chromosomes Cancer. 28:404–414. 2000. View Article : Google Scholar : PubMed/NCBI | |
Pasquali D, Circelli L, Faggiano A, Pancione M, Renzullo A, Elisei R, Romei C, Accardo G, Coppola VR, De Palma M, et al: CDKN1B V109G polymorphism a new prognostic factor in sporadic medullary thyroid carcinoma. Eur J Endocrinol. 164:397–404. 2011. View Article : Google Scholar | |
Tian Q, Frierson HF Jr, Krystal GW and Moskaluk CA: Activating c-kit gene mutations in human germ cell tumors. Am J Pathol. 154:1643–1647. 1999. View Article : Google Scholar : PubMed/NCBI | |
Samuels Y and Ericson K: Oncogenic PI3K and its role in cancer. Curr Opin Oncol. 18:77–82. 2006. View Article : Google Scholar | |
Kizys MM, Cardoso MG, Lindsey SC, Harada MY, Soares FA, Melo MC, Montoya MZ, Kasamatsu TS, Kunii IS, Giannocco G, et al: Optimizing nucleic acid extraction from thyroid fine-needle aspiration cells in stained slides, formalin-fixed/paraffin-embedded tissues and long-term stored blood samples. Arq Bras Endocrinol Metabol. 56:618–626. 2012. View Article : Google Scholar | |
Venselaar H, Te Beek TA, Kuipers RK, Hekkelman ML and Vriend G: Protein structure analysis of mutations causing inheritable diseases. An e-Science approach with life scientist friendly interfaces. BMC Bioinformatics. 11:5482010. View Article : Google Scholar : PubMed/NCBI | |
Lee PH and Shatkay H: F-SNP: Computationally predicted functional SNPs for disease association studies. Nucleic Acids Res. 36(Database issue): D820–D824. 2008. View Article : Google Scholar : | |
Edge SE, Byrd DR, Carducci MA, Compton CC, Fritz AG, Greene F and Trotti A: AJCC Cancer Staging Manual. Springer-Verlag; New York: 2009 | |
Lindsey SC, Kunii IS, Germano-Neto F, Sittoni MY, Camacho CP, Valente FO, Yang JH, Signorini PS, Delcelo R, Cerutti JM, et al: Extended RET gene analysis in patients with apparently sporadic medullary thyroid cancer: Clinical benefits and cost. Horm Cancer. 3:181–186. 2012. View Article : Google Scholar : PubMed/NCBI | |
Kumar R, Smeds J, Berggren P, Straume O, Rozell BL, Akslen LA and Hemminki K: A single nucleotide polymorphism in the 3′untranslated region of the CDKN2A gene is common in sporadic primary melanomas but mutations in the CDKN2B, CDKN2C, CDK4 and p53 genes are rare. Int J Cancer. 95:388–393. 2001. View Article : Google Scholar : PubMed/NCBI | |
Chatterjee S and Pal JK: Role of 5′- and 3′-untranslated regions of mRNAs in human diseases. Biol Cell. 101:251–262. 2009. View Article : Google Scholar : PubMed/NCBI | |
Sakano S, Berggren P, Kumar R, Steineck G, Adolfsson J, Onelöv E, Hemminki K and Larsson P: Clinical course of bladder neoplasms and single nucleotide polymorphisms in the CDKN2A gene. Int J Cancer. 104:98–103. 2003. View Article : Google Scholar : PubMed/NCBI | |
Geddert H, Kiel S, Zotz RB, Zhang J, Willers R, Gabbert HE and Sarbia M: Polymorphism of p16 INK4A and cyclin D1 in adenocarcinomas of the upper gastrointestinal tract. J Cancer Res Clin Oncol. 131:803–808. 2005. View Article : Google Scholar : PubMed/NCBI | |
Chansaenroj J, Theamboonlers A, Junyangdikul P, Swangvaree S, Karalak A, Chinchai T and Poovorawan Y: Polymorphisms in TP53 (rs1042522), p16 (rs11515 and rs3088440) and NQO1 (rs1800566) genes in Thai cervical cancer patients with HPV 16 infection. Asian Pac J Cancer Prev. 14:341–346. 2013. View Article : Google Scholar : PubMed/NCBI | |
Straume O, Smeds J, Kumar R, Hemminki K and Akslen LA: Significant impact of promoter hypermethylation and the 540 C>T polymorphism of CDKN2A in cutaneous melanoma of the vertical growth phase. Am J Pathol. 161:229–237. 2002. View Article : Google Scholar : PubMed/NCBI | |
Boonstra JJ, van Marion R, Tilanus HW and Dinjens WN: Functional polymorphisms associated with disease-free survival in resected carcinoma of the esophagus. J Gastrointest Surg. 15:48–56. 2011. View Article : Google Scholar : | |
Pinheiro UB, de Carvalho Fraga CA, Mendes DC, Marques-Silva L, Farias LC, de Souza MG, Soares MB, Jones KM, Santos SH, de Paula AM, et al: p16 (CDKN2A) SNP rs11515 was not associated with head and neck carcinoma. Tumour Biol. 35:6113–6118. 2014. View Article : Google Scholar : PubMed/NCBI | |
Jin L, Xu L, Song X, Wei Q, Sturgis EM and Li G: Genetic variation in MDM2 and p14ARF and susceptibility to salivary gland carcinoma. PloS One. 7:e493612012. View Article : Google Scholar : PubMed/NCBI | |
Polakova V, Pardini B, Naccarati A, Landi S, Slyskova J, Novotny J, Vodickova L, Bermejo JL, Hanova M, Smerhovsky Z, et al: Genotype and haplotype analysis of cell cycle genes in sporadic colorectal cancer in the czech republic. Hum Mutat. 30:661–668. 2009. View Article : Google Scholar : PubMed/NCBI | |
Royds JA, Al Nadaf S, Wiles AK, Chen YJ, Ahn A, Shaw A, Bowie S, Lam F, Baguley BC, Braithwaite AW, et al: The CDKN2A G500 allele is more frequent in GBM patients with no defined telomere maintenance mechanism tumors and is associated with poorer survival. PloS One. 6:e267372011. View Article : Google Scholar : PubMed/NCBI | |
Thakur N, Hussain S, Nasare V, Das BC, Basir SF and Bharadwaj M: Association analysis of p16 (CDKN2A) and RB1 polymorphisms with susceptibility to cervical cancer in Indian population. Mol Biol Rep. 39:407–414. 2012. View Article : Google Scholar | |
Zhang Y, Sturgis EM, Zafereo ME, Wei Q and Li G: p14ARF genetic polymorphisms and susceptibility to second primary malignancy in patients with index squamous cell carcinoma of the head and neck. Cancer. 117:1227–1235. 2011. View Article : Google Scholar : PubMed/NCBI | |
Zhang F, Xu L, Wei Q, Song X, Sturgis EM and Li G: Significance of MDM2 and P14 ARF polymorphisms in susceptibility to differentiated thyroid carcinoma. Surgery. 153:711–717. 2013. View Article : Google Scholar : | |
De Giorgi V, Savarese I, D'Errico A, Gori A, Papi F, Colombino M, Cristina Sini M, Stanganelli I, Palmieri G and Massi D: CDKN2A mutations could influence the dermoscopic pattern of presentation of multiple primary melanoma: A clinical dermoscopic genetic study. J Eur Acad Dermatol Venereol. 29:574–580. 2014. View Article : Google Scholar : PubMed/NCBI | |
Song X, Sturgis EM, Huang Z, Li X, Li C, Wei Q and Li G: Potentially functional variants of p14ARF are associated with HPV-positive oropharyngeal cancer patients and survival after definitive chemoradiotherapy. Carcinogenesis. 35:62–68. 2014. View Article : Google Scholar | |
Stenman G, Andersson MK and Andrén Y: New tricks from an old oncogene: Gene fusion and copy number alterations of MYB in human cancer. Cell Cycle. 9:2986–2995. 2010. View Article : Google Scholar : PubMed/NCBI |