The Microenvironment-Specific Transformation of Adult Stem Cells Models Malignant Triton Tumors

Here, we demonstrated the differentiation potential of murine muscle-derived stem/progenitor cells (MDSPCs) toward myogenic, neuronal, and glial lineages. MDSPCs, following transplantation into a critical-sized sciatic nerve defect in mice, showed full regeneration with complete functional recovery of the injured peripheral nerve at 6 weeks post-implantation. However, several weeks after regeneration of the sciatic nerve, neoplastic growths were observed. The resulting tumors were malignant peripheral nerve sheath tumors (MPNSTs) with rhabdomyoblastic differentiation, expressing myogenic, neurogenic, and glial markers, common markers of human malignant triton tumors (MTTs). No signs of tumorigenesis were observed 17 weeks post-implantation of MDSPCs into the gastrocnemius muscles of dystrophic/mdx mice, or 1 year following subcutaneous or intravenous injection. While MDSPCs were not oncogenic in nature, the neoplasias were composed almost entirely of donor cells. Furthermore, cells isolated from the tumors were serially transplantable, generating tumors when reimplanted into mice. However, this transformation could be abrogated by differentiation of the cells toward the neurogenic lineage prior to implantation. These results establish that MDSPCs participated in the regeneration of the injured peripheral nerve but transformed in a microenvironment- and time-dependent manner, when they likely received concomitant neurogenic and myogenic differentiation signals. This microenvironment-specific transformation provides a useful mouse model for human MTTs and potentially some insight into the origins of this disease

Tumor BRCA Testing in High Grade Serous Carcinoma: Mutation Rates and Optimal Tissue Requirements

Background: Approximately 25% of women diagnosed with tubo-ovarian high-grade serous carcinoma have germline deleterious mutations in BRCA1 or BRCA2, characteristic of hereditary breast and ovarian cancer syndrome, while somatic mutations have been detected in 3–7%. We set out to determine the BRCA mutation rates and optimal tissue requirements for tumor BRCA testing in patients diagnosed with tubo-ovarian high-grade serous carcinoma. Methods: Sequencing was performed using a multiplexed polymerase chain reaction-based approach on 291 tissue samples, with a minimum sequencing depth of 500X and an allele frequency of >5%. Results: There were 253 surgical samples (87%), 35 biopsies (12%) and 3 cytology cell blocks (1%). The initial failure rate was 9% (25/291), including 9 cases (3%) with insufficient tumor, and 16 (6%) with non-amplifiable DNA. Sequencing was successful in 78% (228/291) and deemed indeterminate due to failed exons or variants below the limit of detection in 13% (38/291). Repeat testing was successful in 67% (28/42) of retested samples, with an overall success rate of 86% (251/291). Clinically significant (pathogenic, likely pathogenic) variants were identified in 17% (48/276) of complete and indeterminate cases. Successful sequencing was dependent on sample type, tumor cellularity and size (p ≤ 0.001) but not on neoadjuvant chemotherapy or age of blocks (p > 0.05). Conclusions: Our study shows a 17% tumor BRCA mutation rate, with an overall success rate of 86%. Biopsy and cytology samples and post-chemotherapy specimens can be used for tumor BRCA testing, and optimal tumors measure ≥5 mm in size with at least 20% cellularity

Identification of genes expressed by immune cells of the colon that are regulated by colorectal cancer-associated variants.

A locus on human chromosome 11q23 tagged by marker rs3802842 was associated with colorectal cancer (CRC) in a genome-wide association study; this finding has been replicated in case-control studies worldwide. In order to identify biologic factors at this locus that are related to the etiopathology of CRC, we used microarray-based target selection methods, coupled to next-generation sequencing, to study 103 kb at the 11q23 locus. We genotyped 369 putative variants from 1,030 patients with CRC (cases) and 1,061 individuals without CRC (controls) from the Ontario Familial Colorectal Cancer Registry. Two previously uncharacterized genes, COLCA1 and COLCA2, were found to be co-regulated genes that are transcribed from opposite strands. Expression levels of COLCA1 and COLCA2 transcripts correlate with rs3802842 genotypes. In colon tissues, COLCA1 co-localizes with crystalloid granules of eosinophils and granular organelles of mast cells, neutrophils, macrophages, dendritic cells and differentiated myeloid-derived cell lines. COLCA2 is present in the cytoplasm of normal epithelial, immune and other cell lineages, as well as tumor cells. Tissue microarray analysis demonstrates the association of rs3802842 with lymphocyte density in the lamina propria (p = 0.014) and levels of COLCA1 in the lamina propria (p = 0.00016) and COLCA2 (tumor cells, p = 0.0041 and lamina propria, p = 6 × 10(-5)). In conclusion, genetic, expression and immunohistochemical data implicate COLCA1 and COLCA2 in the pathogenesis of colon cancer. Histologic analyses indicate the involvement of immune pathways

Mule Regulates the Intestinal Stem Cell Niche via the Wnt Pathway and Targets EphB3 for Proteasomal and Lysosomal Degradation

The E3 ubiquitin ligase Mule is often overexpressed in human colorectal cancers, but its role in gut tumorigenesis is unknown. Here, we show in vivo that Mule controls murine intestinal stem and progenitor cell proliferation by modulating Wnt signaling via c-Myc. Mule also regulates protein levels of the receptor tyrosine kinase EphB3 by targeting it for proteasomal and lysosomal degradation. In the intestine, EphB/ephrinB interactions position cells along the crypt-villus axis and compartmentalize incipient colorectal tumors. Our study thus unveils an important new avenue by which Mule acts as an intestinal tumor suppressor by regulation of the intestinal stem cell niche

High prevalence of mismatch repair deficiency in prostate cancers diagnosed in mismatch repair gene mutation carriers from the colon cancer family registry

The question of whether prostate cancer is part of the Lynch syndrome spectrum of tumors is unresolved. We investigated the mismatch repair (MMR) status and pathologic features of prostate cancers diagnosed in MMR gene mutation carriers. Prostate cancers (mean age at diagnosis = 62 ± SD = 8 years) from 32 MMR mutation carriers (23 MSH2, 5 MLH1 and 4 MSH6) enrolled in the Australasian, Mayo Clinic and Ontario sites of the Colon Cancer Family Registry were examined for clinico-pathologic features and MMR-deficiency (immunohistochemical loss of MMR protein expression and high levels of microsatellite instability; MSI-H). Tumor MMR-deficiency was observed for 22 cases [69 %; 95 % confidence interval (CI) 50–83 %], with the highest prevalence of MMR-deficiency in tumors from MSH2 mutation carriers (19/23, 83 %) compared with MLH1 and MSH6 carriers combined (3/9, 33 %; p = 0.01). MMR-deficient tumors had increased levels of tumor infiltrating lymphocytes compared with tumors without MMR-deficiency (p = 0.04). Under the assumption that tumour MMR-deficiency occurred only because the cancer was caused by the germline mutation, mutation carriers are at 3.2-fold (95 % CI 2.0–6.3) increased risk of prostate cancer, and when assessed by gene, the relative risk was greatest for MSH2 carriers (5.8, 95 % CI 2.6–20.9). Prostate cancer was the first or only diagnosed tumor in 37 % of carriers. MMR gene mutation carriers have at least a twofold or greater increased risk of developing MMR-deficient prostate cancer where the risk is highest for MSH2 mutation carriers. MMR IHC screening of prostate cancers will aid in identifying MMR gene mutation carriers

Digital pathology: Attitudes and practices in the Canadian pathology community

Digital pathology is a rapidly evolving niche in the world of pathology and is likely to increase in popularity as technology improves. We performed a questionnaire for pathologists and pathology residents across Canada, in order to determine their current experiences and attitudes towards digital pathology; which modalities digital pathology is best suited for; and to assess the need for training in digital pathology amongst pathology residents and staff. An online survey consisting of 24 yes/no, multiple choice and free text questions regarding digital pathology was sent out via E-mail to all members of the Canadian Association of Pathologists and pathology residents across Canada. Survey results showed that telepathology (TP) is used in approximately 43% of institutions, primarily for teaching purposes (65%), followed by operating room consults (46%). Seventy-one percent of respondents believe there is a need for TP in their practice; 85% use digital images in their practice. The top two favored applications for digital pathology are teaching and consultation services, with the main advantage being easier access to cases. The main limitations of using digital pathology are cost and image/diagnostic quality. Sixty-two percent of respondents would attend training courses in pathology informatics and 91% think informatics should be part of residency training. The results of the survey indicate that Pathologists and residents across Canada do see a need for TP and the use of digital images in their daily practice. Integration of an informatics component into resident training programs and courses for staff Pathologists would be welcomed

Transplanted MDSPCs foster repair of critical-size sciatic nerve defects.

<p>(<b>A</b>) A 4- to 5 mm segment of the sciatic nerve was removed from the hind limb of each mouse, (<b>B</b>) resulting in a 6.5 to 7 mm defect. (<b>C</b>) Following transplantation of MDSPCs into the defect, complete regeneration from proximal to distal end was observed <i>(n</i>  =  28). Blood vessel networks (arrowheads) were also present around all regenerated nerves. (<b>D</b>) Many <i>nLacZ</i>-positive cells (blue) were observed between weeks 5 and 9 following injury. “<i>p</i>” corresponds to the proximal stump and “<i>d</i>” to the distal stump. (<b>E</b>) The regenerated nerve exhibited both NF (green) and CNPase (red) immunoreactivity. (<b>F</b>) CNPase (red) staining of the regenerated sciatic nerve revealed nodes of Ranvier-like structures (white circles). (<b>G</b>) Cross-sections of regenerated nerve showed <i>nLacZ</i>-positive cells (blue) and exhibited NF-positive axons (green, inset) encompassed by FluoroMyelin-positive cells (red, inset). (<b>H, I, J</b>) Colocalization of β-gal (red) with (<b>H, I</b>) GFAP (green) or (<b>J</b>) CNPase (green), and DAPI (blue) suggests possible differentiation of the MDSPCs into Schwann cells (double-positive cells denoted by arrows). (<b>K-M</b>) Electron microscopy of semi-thin cross-sections of (<b>K</b>) non-operated (uninjured) control, and (<b>L, M</b>) MDSPC-regenerated peripheral nerve 10 weeks after implantation, show a high number of myelin-producing Schwann cells. Arrows indicate Schwann cells surrounding the myelinated axon. “Sc” corresponds to Schwann cells, “M” to myelin sheath, and “Ax” to axons. (<b>N</b>) Graphical quantification of the g-ratio (axonal area: myelinated fiber area) represents the median values of both uninjured and MDSPC-regenerated nerves (<i>P</i><0.001, Mann-Whitney Rank Sum Test). Sciatic nerve regeneration studies represent three independent experiments. The morphometric parameters represent results from 5 mice (2 controls and 3 treated) and analysis of 1000 fibers. Scale bars represent 100 µm (<b>D, E, and G</b>) or 10 µm (<b>F, H-M</b>).</p