Medizinische Universität Graz Austria/Österreich - Forschungsportal - Medical University of Graz

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Gewählte Publikation:

Stadelmeyer, E.
Detection of BRAF mutations in Lentigo maligna melanoma using a highly sensitive method
Doktoratsstudium der Medizinischen Wissenschaft; Humanmedizin; [ Dissertation ] Medical University of Graz; 2012. pp.84. [OPEN ACCESS]


Autor*innen der Med Uni Graz:
Stadelmeyer Elke
Dandachi Nadia
Wolf Peter

Better understanding of tumor progression at the molecular level has led to development of promising therapies for the treatment of otherwise poorly responsive malignant tumors. Compared to other subtypes of malignant melanoma (MM), lentigo maligna melanoma (LMM) is characterized by slow progression from a melanoma in situ to an invasive form. The structure of LMM tumors, with their solitary units or small nests of atypical melanocytes, has hampered molecular characterization and necessitates sensitive methods for mutation analysis. While BRAF mutation has been shown to be an early event in the development of MM, it has not been explored in LMM in adequately large sample sizes. Therefore, the objective of this study was to determine the occurrence of mutations in codon 600 of the BRAF gene in a large cohort of LMM patient samples. In order to analyze low tumor cell portions within LMM lesions, a highly sensitive PCR method was established for the detection of the BRAF V600E, as well as the BRAF V600K mutation. We found that in our hands allele specific PCR was more sensitive than other methods to detect low abundance mutations. We investigated the prevalence of BRAF mutations in a total of 61 LMM lesions. These lesions were prescreened for suitable DNA quality and manually dissected for the presence of at least 5% tumor cells within the tissue samples to be subjected to PCR analysis. In addition, from 39 of these LMM lesions DNA from normal tumor-adjacent tissue could be extracted and investigated for control purposes. Unexpectedly, the BRAF V600K mutation was predominant in our set of LMM lesions and found exclusively in the DNA from tumor area in 16% (10/61) of the samples analyzed. In comparison, the BRAF V600E mutation was detected in only 5% (3/61) of the DNA samples from tumor area. Moreover, an additional 5% (2/39) of tumor adjacent normal skin carried a BRAF V600E mutation as well. However, it needs to be noted that in one of those cases the tumor adjacent skin contained a melanocytic nevus, a condition commonly associated with BRAF V600E mutation. Taken together, the relatively low portion of LMM lesions mutated at the BRAF gene indicates that BRAF mutation plays a role at maximum in a subset of LMM lesions. At this time point due to limited follow-up no conclusion can be drawn, if there is any correlation between the presence of a BRAF mutation in a LMM in situ and the probability of tumor progression. However, the knowledge of the predominant existence of the BRAF V600K mutation in a subset of LMM lesions may contribute to a better understanding of the underlying mechanisms in melanoma development.

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