Forensic STR analyses of the MH3 melanoma along with donor and patient pre-BMT lymphocytes.

<p>Shown are “informative” loci exhibiting donor and patient specific alleles in pre-BMT lymphocytes. Tumor loci are listed in order of relative abundance of the donor-specific alleles (red asterisk) compared to patient-specific (blue asterisk) and shared alleles (black asterisk). Allele peaks <50 relative fluorescence units were censored as “no call” (open circles). Loci with no detectable alleles after PCR amplification (—).</p

STR loci with only patient-specific (P) and shared alleles.

*<p>STR units: number of tandem repeats of the locus-specific tetranucleotide sequence. The X and Y chromosomes were detected by the amelogenin assay <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0066731#pone.0066731-Collins1" target="_blank">[25]</a>.</p

A Melanoma Brain Metastasis with a Donor-Patient Hybrid Genome following Bone Marrow Transplantation: First Evidence for Fusion in Human Cancer

<div><p>Background</p><p>Tumor cell fusion with motile bone marrow-derived cells (BMDCs) has long been posited as a mechanism for cancer metastasis. While there is much support for this from cell culture and animal studies, it has yet to be confirmed in human cancer, as tumor and marrow-derived cells from the same patient cannot be easily distinguished genetically.</p><p>Methods</p><p>We carried out genotyping of a metastatic melanoma to the brain that arose following allogeneic bone-marrow transplantation (BMT), using forensic short tandem repeat (STR) length-polymorphisms to distinguish donor and patient genomes. Tumor cells were isolated free of leucocytes by laser microdissection, and tumor and pre-transplant blood lymphocyte DNAs were analyzed for donor and patient alleles at 14 autosomal STR loci and the sex chromosomes.</p><p>Results</p><p>All alleles in the donor and patient pre-BMT lymphocytes were found in tumor cells. The alleles showed disproportionate relative abundances in similar patterns throughout the tumor, indicating the tumor was initiated by a clonal fusion event.</p><p>Conclusions</p><p>Our results strongly support fusion between a BMDC and a tumor cell playing a role in the origin of this metastasis. Depending on the frequency of such events, the findings could have important implications for understanding the generation of metastases, including the origins of tumor initiating cells and the cancer epigenome.</p></div

Model comparisons using Markov chain Monte Carlo analyses of allelic data.

<p>Panels A and B: Deviances under contamination and fusion models; smaller deviances indicate better fit. Panels C and D: A calibration procedure shows the observed LPML difference (red lines) is rare under the contamination model but typical under the fusion model. More detailed statistical analyses are presented in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0066731#pone.0066731.s002" target="_blank">File S2</a>.</p

STR loci with donor (D), patient-specific (P) and shared (S) alleles.

*<p>STR units: number of tandem repeats of the locus-specific tetranucleotide sequence. The X and Y chromosomes were detected by the amelogenin assay <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0066731#pone.0066731-Collins1" target="_blank">[25]</a>.</p

A section of the MH3 melanoma brain metastasis stained for LCA/CD45 (brown chromogen) and counterstained with hematoxylin (blue).

<p>A. An area with brown LCA/CD45-positive leucocytes (arrow) intermixed with blue LCA/CD45-negative cancer cells. B-D. Adjacent areas from the same section containing only blue LCA/CD45-negative cancer cells.</p

An adjacent section to that in Fig. 1 stained for the melanoma-specific antigen S100.

<p>A. An area of S100-positive tumor cells admixed with infiltrating S100-negative leucocytes (arrows). B. An area containing only S100-positive tumor cells. More detailed pathology analyses are presented in Figs S3 and S4 in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0066731#pone.0066731.s001" target="_blank">File S1</a>.</p

<i>SCHIP1</i> locus associated with centroid size.

<p><b>(A)</b> Regional association plot of centroid size at the <i>SCHIP1</i> locus. Association data are shown using GWAS P-values with the meta-analysis P-value for the lead SNP, rs79909949. The LD pattern is based on the 1000 Genomes Project 2012 African reference and GRCh37/hg19. The estimated recombination rate (cM/Mb) is from HapMap samples. <b>(B)</b> Relative facial size at the upper and lower 95% confidence intervals for centroid size after adjusting for sex and age.</p

GWAS, replication, and meta-analysis results of replicated association signals.

<p>GWAS, replication, and meta-analysis results of replicated association signals.</p

Expression of <i>Schip1</i> and <i>Pde8a</i> during mouse embryonic development.

<p>Whole-mount <i>in situ</i> hybridization of <b>(A-D)</b> <i>Schip1</i> and <b>(E-H)</b> <i>Pde8a</i> expression in mouse embryos from E9.5 to E12.5. ba1, first branchial arch (future mandible); ba2, second branchial arch; fb, forebrain; fn, frontonasal process; fl, forelimb; hb, hindbrain; hl, hindlimb; ln, lateronasal process; mb, midbrain; md, mandible; mn, medionasal process; mx, maxilla; ov, otic vesicle.</p