Dataset Information

Phylogenetic Analyses Reveal Complex Patterns of Melanoma Metastasis

ABSTRACT:

Subpopulations of cells in a primary melanoma can disseminate and establish metastases. Still, the precise ancestral relationship between primary tumors and their metastases is not well understood. Using whole-exome sequencing (for discovery) and targeted sequencing (for validation), we analyzed mutation patterns of primary melanomas and two or more metastases in each of 8 patients to determine their phylogenetic relationships, profiling a total of 31 total tumors. The resulting data show that in 6 of 8 cases, genetically unique cell populations in the primary metastasized in parallel to distinct anatomic sites, rather than sequentially. These data also indicate that individual metastases were sometimes founded by multiple cell populations of the primary that were genetically distinct.

PROVIDER: phs000941 | dbGaP |

SECONDARY ACCESSION(S): PRJNA288058PRJNA288059

REPOSITORIES: dbGaP

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			Action	DRS
	GapExchange_phs000941.v1.p1.xml	Xml
	dbGaPEx2.1.5.xsd	Other
	Study_Report.phs000941.MelanomaMetastaticDissemination.v1.p1.MULTI.pdf	Pdf
	manifest_phs000941.MelanomaMetastaticDissemination.v1.p1.c1.GRU.pdf	Pdf
	manifest_phs000941.MelanomaMetastaticDissemination.v1.p1.c2.DS-M-MDS.pdf	Pdf

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Project description:Following the removal of implanted mammary tumors, nude mice develop multiple-organ metastases at late stage. The metastases may originate from the primary tumors before the resection surgery, or alternatively, from some established metastases. By multiple approaches, we have proved that bone environment could invigorate cancer cells for further dissemination. this study aims to examine if metastatic dissemination from bone to other sites occurs in natural setting of metastatic spread. We herein apply the rapidly evolving barcode system using homing guide RNA/Cas9 to trace the metastases formation in mouse. hgRNA/Cas9 is a self-targeting Crispr system which allows the mutation occurs in the DNA sequence of guide RNA. Tumor cells wer labelled with doxycycline inducible evolving barcoding system. Upon doxycycline treatment the DNA sequence of hgRNA accumulate mutations with time. The diversity of barcodes in each lesion can infer the timeing of seeding while the mutation patterns of barcodes suggest the phylogenetic correlation of metastases. Several findings were made on this study. First, at the terminal stage, multi-organ metastases are not genetically grouped according to sites of metastases. Nonnegative Matrix Factorization (NMF) analysis of mutant barcodes suggested the early disseminated metastases, which have highest level of Shannon entropy, were featured with a common cluster of mutant barcodes irrespective of their locations. Second, most metastases are potentially multiclonal as indicated by multiple clusters of independent mutant barcodes. Third, when we use Shannon entropy as an index of metastasis age , putative parent-child relationship between metastases with unique mutant barcodes clearly exemplified secondary metastatic seeding from bone to other organs. Finally, we did not observe a clear correlation between tumor burden and Shannon entropy across different metastases, suggesting that putative parental metastases might remain small after seeding further metastases.

Project description:Intra-tumor heterogeneity (ITH) results from coexistence of genetically distinct cancer cell (sub)populations, their phenotypic plasticity, and the presence of heterotypic components of the tumor microenvironment (TME). Here we addressed potential association between phenotypic ITH revealed by mass spectrometry imaging (MSI) and the prognosis of breast cancer. Tissue specimens resected from 59 patients treated radically due to the locally advanced HER2-positive invasive ductal carcinoma were included in the study. After on-tissue trypsin digestion of cellu-lar proteins, peptide maps of all cancer regions (about 380,000 spectra in total) were segmented by an unsupervised approach to reveal their intrinsic heterogeneity. A high degree of similarity between spectra was observed, which indicated relative homogeneity of cancer regions. How-ever, when the number and diversity of the detected clusters of spectra were analyzed, differ-ences between patient groups were observed. It is noteworthy that a higher degree of heteroge-neity was found in tumors from patients who remained disease-free during a 5-year follow-up (n=38) compared to tumors from patients with progressive disease (distant metastases detected during follow-up, n=21). Interestingly, such differences were not observed between patients with different status of regional lymph nodes, cancer grade, or expression of estrogen receptor at the time of the primary treatment. Subsequently, spectral components with different abundance in cancer regions were detected in patients with different outcomes, and their hypothetical identity was established by assignment to measured masses of tryptic peptides identified in correspond-ing tissue lysates. Such differentiating components were associated with proteins involved in immune regulation and hemostasis. We postulate that a higher heterogeneity of tumors with a better prognosis could reflect the presence of heterotypic components including the microvas-culature and infiltrating immune cells, that facilitated response to treatment.

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Phylogenetic Analyses Reveal Complex Patterns of Melanoma Metastasis

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