Fig. 4

BRAF and NRAS mutations in PTs and DCCs. a Single cell WGA reliably captures wild-type and mutated alleles. Exon 15 mutation c1799T>A (BRAF) and Exon 2 mutation c181C>A (NRAS) were detected in all single cells (lanes 1–9 or 1–15) of cell lines with BRAF (cell lines 70–61 (n = 9) and MelHo (n = 9)) or NRAS (cell line 102–4; n = 15) mutation. The allelic ratio of wt vs. mut alleles of each cell line was determined using pooled DNA. Note that this ratio is preserved in most single cells. b Summary of results in a and detection of BRAF and NRAS mutation in single gp100+ cells isolated from (i) lymph nodes from healthy controls spiked with melanoma cell line cells, processed and stained as SLN of melanoma patients; (ii) an enzymatically digested DCC-xenograft derived from NRAS-mutated DCCs and (iii) primary melanomas with BRAF mutation. c Mutation analysis of BRAF and NRAS for paired PT-DCC samples (n = 32 patients). Different mutations (either NRAS or BRAF) are indicated by mut1 and mut2. Fisher’s exact test p values indicate differences in BRAF mutational status between PTs and DCCs. d Percentage of patients (n = see Table 1) with homogeneous (all cells harbouring the mutation) and heterogeneous BRAF/NRAS mutational status among DCCs. DCCs were detected using two markers, gp100 (n = 43 cells) or MCSP (n = 61 cells)