Genomic and transcriptomic features of dermatofibrosarcoma protuberans: Unusual chromosomal origin of the COL1A1-PDGFB fusion gene and synergistic effects of amplified regions in tumor development.

The dermatofibrosarcoma protuberans family of tumors (DPFT) comprises cutaneous soft tissue neoplasms associated with aberrant PDGFBR signaling, typically through a COL1A1-PDGFB fusion. The aim of the present study was to obtain a better understanding of the chromosomal origin of this fusion and to assess the spectrum of secondary mutations at the chromosome and nucleotide levels. We thus investigated 42 tumor samples from 35 patients using chromosome banding, fluorescence in situ hybridization, single nucleotide polymorphism arrays, and/or massively parallel sequencing (gene panel, whole exome and transcriptome sequencing) methods. We confirmed the age-associated differences in the origin of the COL1A1-PDGFB fusion and could show that it in most cases must arise after DNA synthesis, i.e., in the S or G2 phase of the cell cycle. Whereas there was a non-random pattern of secondary chromosomal rearrangements, single nucleotide variants seem to have little impact on tumor progression. No clear genomic differences between low-grade and high-grade DPFT were found, but the number of chromosomes and chromosomal imbalances as well as the frequency of 9p deletions all tended to be greater among the latter. Gene expression profiling of tumors with COL1A1-PDGFB fusions associated with unbalanced translocations or ring chromosomes identified several transcriptionally up-regulated genes in the amplified regions of chromosomes 17 and 22, including TBX2, PRKCA, MSI2, SOX9, SOX10, and PRAME.

Gains of Chromosome 1p and 15q are Associated with Poor Survival After Cytoreductive Surgery and HIPEC for Treating Colorectal Peritoneal Metastases.

PURPOSE: Genetic alterations in colorectal peritoneal metastases (PM) are largely unknown. This study was designed to analyze whole-genome copy number alterations (CNA) in colorectal PM and to identify alterations associated with prognosis after cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC). METHODS: All patients with PM, originating from a colorectal adenocarcinoma, who were treated with CRS and HIPEC in Uppsala Sweden, between 2004 and 2015, were included (n = 114). DNA derived from formalin-fixed paraffin-embedded (FFPE) specimens were analyzed for CNA using molecular inversion probe arrays. RESULTS: There were extensive but varying degrees of CNA, ranging from minimal CNA to total aneuploidy. In particular, gain of parts of chromosome 1p and major parts of 15q were associated with poor survival. A combination of gains of 1p and 15q was associated with poor survival, also after adjustment for differences in peritoneal cancer index and completeness of cytoreduction score [hazard ratio (HR) 5.96; 95% confidence interval (CI) 2.19-16.18]. These patients had a mean copy number (CN) of 3.19 compared with 2.24 in patients without gains. Complete CN analysis was performed in 53 patients. Analysis was unsuccessful for the remaining patients due to insufficient amounts of DNA and signals caused by interstitial components and normal cells. There was no difference in survival between patients with successful and unsuccessful CN analysis. CONCLUSIONS: This study shows that gains of parts of chromosome 1p and of major parts of chromosome 15q were significantly associated with poor survival after CRS and HIPEC, which could represent future prognostic biomarkers.

Integrated Molecular Analysis of Undifferentiated Uterine Sarcomas Reveals Clinically Relevant Molecular Subtypes.

PURPOSE: Undifferentiated uterine sarcomas (UUS) are rare, extremely deadly, sarcomas with no effective treatment. The goal of this study was to identify novel intrinsic molecular UUS subtypes using integrated clinical, histopathologic, and molecular evaluation of a large, fully annotated, patient cohort. EXPERIMENTAL DESIGN: Fifty cases of UUS with full clinicopathologic annotation were analyzed for gene expression (n = 50), copy-number variation (CNV, n = 40), cell morphometry (n = 39), and protein expression (n = 22). Gene ontology and network enrichment analysis were used to relate over- and underexpressed genes to pathways and further to clinicopathologic and phenotypic findings. RESULTS: Gene expression identified four distinct groups of tumors, which varied in their clinicopathologic parameters. Gene ontology analysis revealed differential activation of pathways related to genital tract development, extracellular matrix (ECM), muscle function, and proliferation. A multivariable, adjusted Cox proportional hazard model demonstrated that RNA group, mitotic index, and hormone receptor expression influence patient overall survival (OS). CNV arrays revealed characteristic chromosomal changes for each group. Morphometry demonstrated that the ECM group, the most aggressive, exhibited a decreased cell density and increased nuclear area. A cell density cutoff of 4,300 tumor cells per mm2 could separate ECM tumors from the remaining cases with a sensitivity of 83% and a specificity of 94%. IHC staining of MMP-14, Collagens 1 and 6, and Fibronectin proteins revealed differential expression of these ECM-related proteins, identifying potential new biomarkers for this aggressive sarcoma subgroup. CONCLUSIONS: Molecular evaluation of UUS provides novel insights into the biology, prognosis, phenotype, and possible treatment of these tumors.

Different patterns of clonal evolution among different sarcoma subtypes followed for up to 25 years.

To compare clonal evolution in tumors arising through different mechanisms, we selected three types of sarcoma-amplicon-driven well-differentiated liposarcoma (WDLS), gene fusion-driven myxoid liposarcoma (MLS), and sarcomas with complex genomes (CXS)-and assessed the dynamics of chromosome and nucleotide level mutations by cytogenetics, SNP array analysis and whole-exome sequencing. Here we show that the extensive single-cell variation in WDLS has minor impact on clonal key amplicons in chromosome 12. In addition, only a few of the single nucleotide variants in WDLS were present in more than one lesion, suggesting that such mutations are of little significance in tumor development. MLS displays few mutations other than the FUS-DDIT3 fusion, and the primary tumor is genetically sometimes much more complex than its relapses, whereas CXS in general shows a gradual increase of both nucleotide- and chromosome-level mutations, similar to what has been described in carcinomas.

Four evolutionary trajectories underlie genetic intratumoral variation in childhood cancer.

A major challenge to personalized oncology is that driver mutations vary among cancer cells inhabiting the same tumor. Whether this reflects principally disparate patterns of Darwinian evolution in different tumor regions has remained unexplored1-5. We mapped the prevalence of genetically distinct clones over 250 regions in 54 childhood cancers. This showed that primary tumors can simultaneously follow up to four evolutionary trajectories over different anatomic areas. The most common pattern consists of subclones with very few mutations confined to a single tumor region. The second most common is a stable coexistence, over vast areas, of clones characterized by changes in chromosome numbers. This is contrasted by a third, less frequent, pattern where a clone with driver mutations or structural chromosome rearrangements emerges through a clonal sweep to dominate an anatomical region. The fourth and rarest pattern is the local emergence of a myriad of clones with TP53 inactivation. Death from disease was limited to tumors exhibiting the two last, most dynamic patterns.

Scattered genomic amplification in dedifferentiated liposarcoma.

BACKGROUND: Atypical lipomatous tumor (ALT), well differentiated liposarcoma (WDLS) and dedifferentiated liposarcoma (DDLS) are cytogenetically characterized by near-diploid karyotypes with no or few other aberrations than supernumerary ring or giant marker chromosomes, although DDLS tend to have somewhat more complex rearrangements. In contrast, pleomorphic liposarcomas (PLS) have highly aberrant and heterogeneous karyotypes. The ring and giant marker chromosomes contain discontinuous amplicons, in particular including multiple copies of the target genes CDK4, HMGA2 and MDM2 from 12q, but often also sequences from other chromosomes. RESULTS: The present study presents a DDLS with an atypical hypertriploid karyotype without any ring or giant marker chromosomes. SNP array analyses revealed amplification of almost the entire 5p and discontinuous amplicons of 12q including the classical target genes, in particular CDK4. In addition, amplicons from 1q, 3q, 7p, 9p, 11q and 20q, covering from 2 to 14 Mb, were present. FISH analyses showed that sequences from 5p and 12q were scattered, separately or together, over more than 10 chromosomes of varying size. At RNA sequencing, significantly elevated expression, compared to myxoid liposarcomas, was seen for TRIO and AMACR in 5p and of CDK4, HMGA2 and MDM2 in 12q. CONCLUSIONS: The observed pattern of scattered amplification does not show the characteristics of chromothripsis, but is novel and differs from the well known cytogenetic manifestations of amplification, i.e., double minutes, homogeneously staining regions and ring chromosomes. Possible explanations for this unusual distribution of amplified sequences might be the mechanism of alternative lengthening of telomeres that is frequently active in DDLS and events associated with telomere crisis.

Rawcopy: Improved copy number analysis with Affymetrix arrays.

Microarray data is subject to noise and systematic variation that negatively affects the resolution of copy number analysis. We describe Rawcopy, an R package for processing of Affymetrix CytoScan HD, CytoScan 750k and SNP 6.0 microarray raw intensities (CEL files). Noise characteristics of a large number of reference samples are used to estimate log ratio and B-allele frequency for total and allele-specific copy number analysis. Rawcopy achieves better signal-to-noise ratio and higher proportion of validated alterations than commonly used free and proprietary alternatives. In addition, Rawcopy visualizes each microarray sample for assessment of technical quality, patient identity and genome-wide absolute copy number states. Software and instructions are available at http://rawcopy.org.

1p36 deletion is a marker for tumour dissemination in microsatellite stable stage II-III colon cancer.

BACKGROUND: The clinical behaviour of colon cancer is heterogeneous. Five-year overall survival is 50-65% with all stages included. Recurring somatic chromosomal alterations have been identified and some have shown potential as markers for dissemination of the tumour, which is responsible for most colon cancer deaths. We investigated 115 selected stage II-IV primary colon cancers for associations between chromosomal alterations and tumour dissemination. METHODS: Follow-up was at least 5 years for stage II-III patients without distant recurrence. Affymetrix SNP 6.0 microarrays and allele-specific copy number analysis were used to identify chromosomal alterations. Fisher's exact test was used to associate alterations with tumour dissemination, detected at diagnosis (stage IV) or later as recurrent disease (stage II-III). RESULTS: Loss of 1p36.11-21 was associated with tumour dissemination in microsatellite stable tumours of stage II-IV (odds ratio = 5.5). It was enriched to a similar extent in tumours with distant recurrence within stage II and stage III subgroups, and may therefore be used as a prognostic marker at diagnosis. Loss of 1p36.11-21 relative to average copy number of the genome showed similar prognostic value compared to absolute loss of copies. Therefore, the use of relative loss as a prognostic marker would benefit more patients by applying also to hyperploid cancer genomes. The association with tumour dissemination was supported by independent data from the The Cancer Genome Atlas. CONCLUSION: Deletions on 1p36 may be used to guide adjuvant treatment decisions in microsatellite stable colon cancer of stages II and III.