Abstract P3-04-04: Germline and somatic mutation status in tissues from BRCA1/2 carriers

Background – aim: In carriers of BRCA1/2 pathogenic mutations (mut), it is expected that the germline mut is present in all tissues, particularly in normal; the somatic mut status in normal tissues from these patients is usually not addressed. We investigated the mut status in normal and tumor tissues in a real-life cohort of BRCA1/2 carriers who underwent prophylactic surgery.

Methods: All 53 women had known BRCA1/2 germline mut that had been assessed independently; 42 had previous cancer manifestation (PCM); all had prophylactic mastectomy; 22 had prophylactic hystero-salpingo-oophorectomy. By using a 60-gene NGS panel, we examined the mut status of 231 samples, 39 peripheral blood and 192 paraffin tissues (FFPE: 46 tumors, out of which 43 breast; 97 normal breast [NB]; 49 normal ovary and salpinx [NGYN]). Germline mut status was interrogated in tissues with the above panel, Sanger sequencing and a multiplex PCR protocol for large exonic deletions, along with extensive FFPE DNA quality control (QC) to exclude false negatives.

Results: Eight patients carried germline BRCA2 and 45 BRCA1 mut (29 in the BRCT-domain; 31 substitutions/indels). We identified somatic mut in 85% of the tumors and in 64% of the normal samples; mut were found significantly more often (p=0.003) and in higher numbers (p<0.001) in NGYN than in NB. In NB and NGYN, top 3 genes with somatic mut were BRCA2 (28%), BRCA1 (17%), TP53 (7%). In tumors, somatic mut were most frequent in TP53 (49%; p<0.001) and BRCA1 (38%; p=0.039). Among all tissue types, the 5 tumors post-neoadjuvant treatment had the highest and NB the lowest mut load (p=0.001). In NB and NGYN, mut load was not affected by PCM or BRCA1 mut domain but it was higher in BRCA1 vs. BRCA2 carriers (p=0.027) and in those with BRCA1 substitutions/indels vs. exon deleting and skipping mut (p<0.001). In tumors, germline BRCA1 substitutions/indels were associated with higher mut load (p=0.014). We validated germline mut status in all blood samples and in 111 tissue samples that passed FFPE DNA QC from 40 patients. The germline mut was not found in 14 samples (4 breast tumors; 3 NB; 7 NGYN) from 10 (25%) patients, all BRCA1 carriers, 9 with germline mut in the BRCT-domain. The only non-BRCT domain germline mut that was lost in one breast tumor, p.V1234fs, was replaced by the R1751* (validated), again in the BRCT domain. In normal tissues, those with lost germline mut had significantly less somatic mut compared to those with preserved germline mut (p<0.001).

Conclusions: In BRCA1/2 carriers, somatic mut in BRCA genes and TP53 are present in normal breast and GYN tissues, more frequently in the latter, and seem associated with the mutated gene and with the type of mut in the germline. The mut status of normal breast tissue does not seem to be affected by neoadjuvant chemotherapy for breast cancer. The observed BRCA1 germline mut loss, particularly in normal tissues, may be approached as a negative selection for the inherited mut; similarly to the described germline mut reversion after chemotherapy, tissues may react to deleterious effects of haploinsufficiency, which needs functional validation.

Citation Format: Kotoula V, Demiri E, Fostira F, Vrettou E, Papadopoulou K, Tikas I, Papazisis K, Zaramboukas T, Asimaki-Vlachopoulou A, Miliaras S, Fountzilas E, Ananiadis A, Chrisafi S, Poulios C, Natsiopoulos I, Tsiftsoglou A, Fountzilas G. Germline and somatic mutation status in tissues from BRCA1/2 carriers [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P3-04-04.

Angiogenic Potential and Secretome of Human Apical Papilla Mesenchymal Stem Cells in Various Stress Microenvironments

Stem cells from the apical papilla (SCAP) of human adult teeth are considered an accessible source of cells with angiogenic properties. The aims of this study were to investigate the endothelial transdifferentiation of SCAP, the secretion of pro- and antiangiogenic factors from SCAP, and the paracrine effects of SCAP when exposed to environmental stress to stimulate tissue damage. SCAP were exposed to serum deprivation (SD), glucose deprivation (GD), and oxygen deprivation/hypoxia (OD) conditions, individually or in combination. Endothelial transdifferentiation was evaluated by in vitro capillary-like formation assays, real-time polymerase chain reaction, western blot, and flow cytometric analyses of angiogenesis-related markers; secretome by antibody arrays and enzyme-linked immunosorbent assays (ELISA); and paracrine impact on human umbilical vein endothelial cells (HUVECs) by in vitro transwell migration and capillary-like formation assays. The short-term exposure of SCAP to glucose/oxygen deprivation (GOD) in the presence, but mainly in deprivation, of serum (SGOD) elicited a proangiogenesis effect indicated by expression of angiogenesis-related genes involved in vascular endothelial growth factor (VEGF)/VEGFR and angiopoietins/Tie pathways. This effect was unachievable under SD in normoxia, suggesting that the critical microenvironmental condition inducing rapid endothelial shift of SCAP is the combination of SGOD. Interestingly, SCAP showed high adaptability to these adverse conditions, retaining cell viability and acquiring a capillary-forming phenotype. SCAP secreted higher numbers and amounts of pro- (angiogenin, IGFBP-3, VEGF) and lower amounts of antiangiogenic factors (serpin-E1, TIMP-1, TSP-1) under SGOD compared with SOD or SD alone. Finally, secretome obtained under SGOD was most effective in inducing migration and capillary-like formation by HUVECs. These data provide new evidence on the microenvironmental factors favoring endothelial transdifferentiation of SCAP, uncovering the molecular mechanisms regulating their fate. They also validate the angiogenic properties of their secretome giving insights into preconditioning strategies enhancing their therapeutic potential.

CD133 marks a stem cell population that drives human primary myelofibrosis

Primary myelofibrosis is a myeloproliferative neoplasm characterized by bone marrow fibrosis, megakaryocyte atypia, extramedullary hematopoiesis, and transformation to acute myeloid leukemia. To date the stem cell that undergoes the spatial and temporal chain of events during the development of this disease has not been identified. Here we describe a CD133(+) stem cell population that drives the pathogenesis of primary myelofibrosis. Patient-derived circulating CD133(+) but not CD34(+)CD133(-) cells, with a variable burden for JAK2 (V617F) mutation, had multipotent cloning capacity in vitro. CD133(+) cells engrafted for up to 10 months in immunocompromised mice and differentiated into JAK2-V617F(+) myeloid but not lymphoid progenitors. We observed the persistence of human, atypical JAK2-V617F(+) megakaryocytes, the initiation of a prefibrotic state, bone marrow/splenic fibrosis and transition to acute myeloid leukemia. Leukemic cells arose from a subset of CD133(+) cells harboring EZH2 (D265H) but lacking a secondary JAK2 (V617F) mutation, consistent with the hypothesis that deregulation of EZH2 activity drives clonal growth and increases the risk of acute myeloid leukemia. This is the first characterization of a patient-derived stem cell population that drives disease resembling both chronic and acute phases of primary myelofibrosis in mice. These results reveal the importance of the CD133 antigen in deciphering the neoplastic clone in primary myelofibrosis and indicate a new therapeutic target for myeloproliferative neoplasms.

Manufacturing, characterization and control of cell-based medicinal products: challenging paradigms toward commercial use

During the past decade, a large number of cell-based medicinal products have been tested in clinical trials for the treatment of various diseases and tissue defects. However, licensed products and those approaching marketing authorization are still few. One major area of challenge is the manufacturing and quality development of these complex products, for which significant manipulation of cells might be required. While the paradigms of quality, safety and efficacy must apply also to these innovative products, their demonstration may be demanding. Demonstration of comparability between production processes and batches may be difficult for cell-based medicinal products. Thus, the development should be built around a well-controlled manufacturing process and a qualified product to guarantee reproducible data from nonclinical and clinical studies.

Assessment of the impact of two different isolation methods on the osteo/odontogenic differentiation potential of human dental stem cells derived from deciduous teeth

Human deciduous teeth have been proposed as a promising source of mesenchymal stem cells for application in bone and dental tissue engineering. We established cultures of mesenchymal stem cells from the pulp of human deciduous teeth (deciduous teeth stem cells, DTSCs) and analyzed their morphologic, growth, immunophenotypic, and osteo/odontogenic differentiation characteristics using different isolation methods and culturing environments. We compared the biologic behavior of DTSCs isolated either by enzymatic dissociation (DTSCs-ED) or by direct outgrowth from pulp tissue explants (DTSCs-OG). We found that different isolation methods give rise to different populations/lineages of cells with respect to their phenotypic and differentiation characteristics. DTSCs-ED cultures comprised heterogeneous cell populations, whereas DTSCs-OG comprised more homogenous spindle-shaped cells. We have characterized DTSCs as STRO-1(+)/CD146(+)/CD34(+)/CD45(-) cells. However, the percentage of STRO-1(+) and CD34(+) cells was higher in DTSCs-ED (STRO-1, 17.01 ± 5.04%; CD34, 19.79 ± 4.66%) compared to DTSCs-OG cultures (STRO-1, 5.18 ± 2.39%; CD34, 9.94 ± 3.41%), probably as a result of a higher release of stem/progenitor cells from the perivascular niche during enzymatic dissociation. DTSCs isolated using either method displayed an active potential for cellular migration and biomineralization, giving rise to 3D mineralized structures when challenged with dexamethasone, monopotassium phosphate, and β-glycerophosphate. These cellular aggregates progressively expressed differentiation markers of functional odontoblasts, including dentin sialophosphoprotein, bone sialoprotein, osteocalcin, and alkaline phosphatase, having the characteristics of osteodentin. However, in DTSCs-ED, the mineralization rate and the amount of mineralized matrix produced was higher compared to DTSCs-OG cultures. Therefore, DTSCs-ED cells display enhanced biomineralization potential, which might be of advantage for application in clinical therapy.

Comparative analysis of in vitro osteo/odontogenic differentiation potential of human dental pulp stem cells (DPSCs) and stem cells from the apical papilla (SCAP)

OBJECTIVE

The aim of this study was to compare the in vitro osteo/odontogenic differentiation potential of mesenchymal stem cells (MSCs) derived from the dental pulp (dental pulp stem cells - DPSCs) or the apical papilla (stem cells from the apical papilla - SCAP) of permanent developing teeth.

DESIGN

DPSCs and SCAP cultures were established from impacted third molars of young healthy donors at the stage of root development. Cultures were analysed for stem cell markers, including STRO-1, CD146, CD34 and CD45 using flow cytometry. Cells were then induced for osteo/odontogenic differentiation by media containing dexamethasone, KH(2)PO(4) and β-glycerophosphate. Cultures were analysed for morphology, growth characteristics, mineralization potential (Alizarin Red method) and differentiation markers (dentine sialophosphoprotein-DSPP, bone sialoprotein-BSP, osteocalcin-OCN, alkaline phosphatase-ALP), using immunocytochemistry and reverse transcriptase-polymerase chain reaction.

RESULTS

All DPSCs and SCAP cultures were positive for STRO-1, CD146 and CD34, in percentages varying according to cell type and donor, but negative for CD45. Both types of MSCs displayed an active potential for cellular migration, organization and mineralization, producing 3D mineralized structures. These structures progressively expressed differentiation markers, including DSPP, BSP, OCN, ALP, having the characteristics of osteodentin. SCAP, however, showed a significantly higher proliferation rate and mineralization potential, which might be of significance for their use in bone/dental tissue engineering.

CONCLUSIONS

This study provides evidence that different types of dental MSCs can be used in tissue engineering/regeneration protocols as an approachable stem cell source for osteo/odontogenic differentiation and biomineralization that could be further applied for stem cell-based clinical therapies.

Challenges with advanced therapy medicinal products and how to meet them

Advanced therapy medicinal products (ATMPs), which include gene therapy medicinal products, somatic cell therapy medicinal products and tissue-engineered products, are at the cutting edge of innovation and offer a major hope for various diseases for which there are limited or no therapeutic options. They have therefore been subject to considerable interest and debate. Following the European regulation on ATMPs, a consolidated regulatory framework for these innovative medicines has recently been established. Central to this framework is the Committee for Advanced Therapies (CAT) at the European Medicines Agency (EMA), comprising a multidisciplinary scientific expert committee, representing all EU member states and European Free Trade Association countries, as well as patient and medical associations. In this article, the CAT discusses some of the typical issues raised by developers of ATMPs, and highlights the opportunities for such companies and research groups to approach the EMA and the CAT as a regulatory advisor during development.

Primary osteogenic sarcoma of the breast

Primary osteogenic sarcomas of the breast are exceptionally uncommon. We describe such a case occurring in a 66-year-old woman who presented with a hard mass in her left breast. Mammography and breast ultrasonography showed a calcified breast lump, but features were not diagnostic. Modified radical mastectomy of the left breast, including axillary lymph node dissection, was performed. Microscopical and immunohistochemical findings established the diagnosis of primary osteogenic sarcoma. Because there was no evidence of metastasis, no further treatment was considered necessary. She remained well 15 months later, without tumour recurrence. We discuss in detail the diagnostic implications of this rare entity.

Patterns of cell death and cell cycle profiles of cultured WEHI 13 var fibroblasts exposed to eluates of composite resins used for direct and indirect restorations

Previous studies have shown that in vitro exposure to single compounds released from composite resins may induce cell death. In the present study the effects of eluates from commercially available composite resins used for direct or indirect restorations were evaluated on the cell cycle progression and type of cell death of cultured WEHI 13 var fibroblasts. Cells exposed to eluates of the materials were assessed for cytotoxicity by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay for cell death, for cell cycle profiles by flow cytometry, for caspase-3 biochemically and by immunocytochemistry, and for morphological changes by fluorescence microscopy with acridine orange. The direct composite resin eluates induced extensive apoptosis, followed by secondary necrosis. This was accompanied by cell enlargement, micromultinucleation, chromatin disintegration, cell cycle arrest at different phases, and caspase-3 activation. The composites for indirect restorations were much less cytotoxic at all biological end-points investigated. The findings suggest that composite resins used for direct and indirect dental restorations differ in their cytotoxic potential and their ability to affect basic cellular functions. This underlines the impact of improved polymerization with respect to their biologic behavior.

Molecular analysis of ampicillin-resistant sporadic Salmonella typhi and Salmonella paratyphi B clinical isolates

OBJECTIVE: To study the mechanisms of antibiotic resistance in Salmonella typhi and Salmonella paratyphi B clinical isolates, and the clonality of resistant strains. METHODS: Antibiotic susceptibility was tested by disk-agar diffusion. Conjugation experiments and plasmid analysis by agarose gel electrophoresis after EcoRI digestion were followed by hybridization to a digoxigenin-labeled TEM-type beta-lactamase probe. DNA fingerprints were obtained by pulsed-field gel electrophoresis of Xbal-digested chromosomal DNA. RESULTS: Three S. typhi isolates (7% of the isolates studied), of which one was ampicillin resistant and the other two multiresistant (ampicillin, chloramphenicol, tetracycline, sulfamethoxazole/trimethoprim and streptomycin), and two ampicillin-resistant S. paratyphi B isolates (25% of the isolates studied) were further evaluated. A 34-MDa conjugative plasmid, previously isolated from Salmonella enteritidis, conferred ampicillin resistance. A 100-MDa conjugative plasmid encoded resistance to chloramphenicol, tetracycline and sulfamethoxazole/trimethoprim, as well as ampicillin. Chromosomal fingerprinting revealed two distinct resistant strains for each serovar which were different from a matched set of sensitive S. typhi strains. CONCLUSIONS: Two conjugative, TEM-type beta-lactamase-encoding plasmids conferred ampicillin resistance to S. typhi and S. paratyphi B. The 34-MDa plasmid was identical to that previously characterized from S. enteritidis, while the 100-MDa plasmid also encoded resistance to chloramphenicol, tetracycline and sulfamethoxazole/trimethoprim. Resistant isolates did not belong to a single clone but rather represented distinct strains.

The inhibition of commitment of mouse erythroleukemia cells by steroids involves a glucocorticoid-receptor mediated process(es) acting at the nuclear level

Dexamethasone has been shown to inhibit dimethylsulfoxide (DMSO)-induced differentiation of mouse erythroleukemia (or Friend) cells by blocking commitment to terminal erythroid maturation. In this study, we confirmed previous reports indicating the presence of glucocorticoid receptors in murine erythroleukemia cells and examined the mechanism(s) by which steroids block commitment. Untreated murine erythroleukemia cells contain dexamethasone receptors which decrease in number during DMSO-induced cell differentiation. When steroids of different classes (estrogenic, androgenic, glucocorticoid) were tested for inhibition of commitment and for displacement of [3H]dexamethasone from its receptors in DMSO-treated cells, we observed that the glucocorticoids dexamethasone, prednisolone and hydrocortisone, all blocked commitment and substantially displaced [3H]dexamethasone. In contrast, steroids other than glucocorticoids failed to inhibit commitment or displace [3H]dexamethasone. Analysis of kinetics of dexamethasone binding to chromatin revealed that dexamethasone binds to the nucleus via the receptor and preferentially interacts with active chromatin. Inhibition of commitment by dexamethasone persisted in cells released from this agent and reincubated with DMSO in the presence of another glucocorticoid of similar affinity to steroid receptors; inhibition of commitment, however, was not obtained when cells removed from dexamethasone were incubated in the presence of beta-estradiol, progesterone and testosterone. These data indicate that inhibition of commitment of mouse erythroleukemia cells by steroids is associated with binding to glucocorticoid receptors and may involve interactions of steroids and their receptors with regions of chromatin.