Osteoblastoma of scaphoid of the carpus: a case report

Osteoblastoma is a rather uncommon tumor, especially when located in the wrist (and hand). Its diagnosis therefore appears to be problematic. We describe a case of osteoblastoma of the scaphoid bone and its management. To our knowledge, this is the fourth case of osteoblatoma of the carpus reported in the literature. Proximal row carpectomy was chosen because of the aggressive nature of the tumor. A tendon transfer was performed in the same session for wrist stabilization. Other authors have opted for a more conservative approach (tumor curettage with bone grafting).Key words: Osteoblastoma, scaphoid, hand, proximal row carpectomy, Morocc

Estabelecimento e caracterização de modelos resistentes e matastaticos de osteossarcoma humano in vitro e in vivo

Doutoramento em BiologiaOsteossarcoma é uma doença rara, sendo o tipo mais comum de tumor maligno do osso. O pico de incidência ocorre durante a adolescência e desenvolve-se principalmente nos ossos longos. Os tratamentos atuais incluem quimioterapia antes e após a cirurgia e a ressecção cirúrgica de todos os locais envolvidos (tumor primário e metástases quando presente). As metástases, principalmente nos pulmões, são um grande problema no diagnóstico (20-30% dos pacientes) e durante a história natural do osteossarcoma (cerca de 30% de recaída), afetam uma percentagem considerável de pacientes e são considerados os maiores problemas desta doença. Biologicamente, os osteossarcomas são um dos tumores mais complexos observados nas crianças, no que diz respeito à heterogeneidade, anomalias moleculares e cromossómicas e ao seu microambiente específico. A resistência aos agentes quimioterápicos utilizados no tratamento do osteossarcoma também é um fator prognóstico de alto risco de recaída, independentemente da quimioterapia utilizada. É urgente compreender os mecanismos relacionados a esses fenómenos e desenvolver novos quimioterápicos para superar esses problemas e aumentar a taxa de sobrevivência do paciente. O desenvolvimento de novos fármacos requer múltiplos modelos pré-clínicos adequados para mimetizar a complexidade genómica do osteossarcoma que se desenvolve-se num microambiente ósseo e metastático nos pulmões, apesar dos tratamentos quimioterápicos habituais. Nesta tese, foram desenvolvidos e caracterizados diferentes modelos pré-clínicos clinicamente relevantes in vitro e in vivo, incluindo modelos resistentes bioluminescentes, de modo a melhor compreender esta doença e alguns dos mecanismos de resistência relacionados. Desenvolvemos, em primeiro lugar, dois modelos ortotópicos xenotransplantados derivados de linhas celulares (CDX) bioluminescentes (Luc/mKate2), capazes de desenvolver metástases espontaneamente. As células bioluminescentes foram injetadas ortotopicamente, em diferentes contextos: imune (estirpes de ratinhos de laboratório - nude e NSG) e ósseo (intratibial e paratibial com ativação do periósteo). O sistema IVIS SpectrumCT, combinando tomografia computadorizada longitudinal (TC) e bioluminescência, foi utilizado para acompanhar o crescimento primário do tumor e a disseminação metastática em tempo real. O contexto imune murino, o contexto genético dos dois modelos CDX e o contexto ósseo (intratibial ou paratibial) influenciaram o enxerto tumoral, o crescimento primário do tumor e o comportamento agressivo local (osteocondensação e osteólise), bem como a disseminação metastática para os pulmões, ossos e baço (uma localização incomum em seres humanos). Observou-se também que a estirpe de ratinhos NSG e a injeção intratibial apresentam melhores características para o desenvolvimento de modelos que a injeção paratibial ou a estirpe de ratinhos nude. Seguidamente, desenvolvemos modelos resistentes bioluminescentes in vitro, aos principais medicamentos utilizados no osteossarcoma, nomeadamente metotrexato (5modelos) e doxorrubicina (1modelo), por exposição contínua a esses medicamentos. Realizando o mesmo procedimento, não foi obtida resistência à mafosfamida. Investigamos os mecanismos da resistência adquirida relacionados com estas drogas e observamos comportamentos diferenciais in vitro e in vivo (com modelos CDX ortotópicos bioluminescentes) das linhas resistentes e respetivas linhas parentais. Um mecanismo de resistência na linha celular resistente à doxorrubicina foi observado, nomeadamente a indução da proteína PgP. Mostramos diferentes mecanismos de resistência adquirida ao metotrexato de acordo com o backgroud genético das linhas celulares, que afetam a expressão génica e provocam alterações no número de cópias ao nível dos cromossomas. Foram observados diferentes comportamentos dos modelos resistentes bioluminescentes ortotópicos (CDX) in vivo em comparação com as respetivas linhas parentais. Finalmente, utilizando amostras de osteossarcoma humano provenientes de biópsias de pacientes em recidiva após a quimioterapia habitual, foram desenvolvidos modelos resistentes xenotransplantados derivados do paciente (PDX), quer subcutaneamente quer ortotopicamente (no osso). A caracterização desses modelos está em curso, em particular a comparação das características moleculares destes (sequenciamento completo do exoma e sequenciamento do ARN) com as do tumor do paciente na recaída e do mesmo no diagnóstico. Todos esses modelos desenvolvidos em diferentes contextos in vitro e in vivo trazem informações complementares para outros tipos de modelos de osteossarcoma já existentes. Estes modelos são necessários para obter mais informações sobre os diferentes processos que envolvem o desenvolvimento inicial, a progressão e a sensibilidade/resistência ao tratamento no osteossarcoma. Permitem ajudar ainda a avaliação de novos quimioterápicos, de modo a encontrar soluções para a atual falta de terapias eficientes no osteossarcoma.Osteosarcoma is a rare disease and the most common type of malignant bone tumor. The peak incidence occurs during the adolescence and the disease develops mainly in long bones. Current treatments include chemotherapy before and after surgery and surgical resection of all the involved sites (primary tumor and metastasis when present). Metastases mainly in the lungs are a major challenge at diagnosis (20-30% of the patients) and during the natural history of osteosarcoma (around 30% of relapse, most being metastatic), affect a considerable percentage of patients with osteosarcoma, being considered the biggest problem of this disease. Biologically, osteosarcomas are one of the most complex tumours in children in regard to tumour heterogeneity, molecular and chromosomal abnormalities, and their specific microenvironment. Resistance to the chemotherapeutic agents used in osteosarcoma is also a prognostic factor of high risk of relapse, whatever the chemotherapy used. It is urgent to understand the mechanisms related with these phenomena and develop new drugs in order to overcome these challenges and increase patient survival. New drug development requires suitable multiple pre-clinical models to better mimic the genomic complexity of osteosarcoma which develops in a bone microenvironment and in a metastatic setting in the lungs, despite usual chemotherapeutic treatments. In this thesis, we developed and characterised different and clinically relevant in vitro and in vivo preclinical models, including bioluminescent resistant models in order to understand better this disease and some of the resistant mechanism related. First, two bioluminescent (Luc/mKate2) cell line derived xenograft (CDX) models were developed in an orthotopic bone setting able to spontaneously metastasize. Bioluminescent cells were injected orthotopically, in different immune (nude and NSG mouse strains) and bone (intratibial and paratibial with periosteum activation) contexts. IVIS SpectrumCT system, combining longitudinal computed tomography (CT) and bioluminescence, was used to follow primary tumor growth and metastatic spread in real-time. The murine immune context, the genetic background of the two CDX-models, and the bone context (intratibial or paratibial) influenced tumor engraftment, primary tumor growth and local aggressive behavior (osteocondensation and osteolysis) as well as metastatic spread to lungs, bone, and spleen (an unusual localization in humans). It was also observed that intratibial injection in NSG mice showed better characteristics for model development than paratibial injection or nude mice recipient. We further developed in vitro bioluminescent models that were resistant to the main drugs used in osteosarcoma, methotrexate (5 models) and doxorubicin (one model), by continuous exposure to these drugs. With the same technique no resistance was obtained for mafosfamide. We explored the mechanism of the acquired resistance to these drugs and observed the differential in vitro and in vivo behaviors (with CDX bioluminescent orthotopic models) of the resistant lines and their parental counterpart. A multidrug phenomenon by PgP induction was observed in the doxorubicin resistant cells. We show different mechanisms of acquired resistance to methotrexate according to the genetic background of the cell lines affecting either gene expression and copy number abnormalities. Different in vivo behavior of the resistant bioluminescent orthotopic CDX models compared to their parental counterparts were observed. Finally, using human biopsy samples of osteosarcoma relapsing after usual anti-osteosarcoma chemotherapy were developed resistant patient-derived xenograft (PDX) models, either in subcutaneous as in orthotopic bone setting. The characterization of these models are still ongoing, in particular the comparison of their molecular characteristics, i.e. using whole exome and RNA sequencing, in comparison with the patient tumor at relapse and with the same patient tumor at diagnosis. All these multiple models developed in different in vitro and in vivo contexts bring complementary information to other types of existing osteosarcoma models. They are needed to get more insight into the different processes involving osteosarcoma initiation, progression and in particular treatment sensitivity/resistance. They will further help drug testing to find solution to the current lack of efficient new drugs in osteosarcoma

Imaging in pre-clinical cancer research : applied to bone metastases

The aim of this work was to develop methods to measure structural changes in the skeleton using MicroCT. In addition, these new methods should be able to quantify biologically relevant changes. In order to do this, normalized methods to analyse MicroCT scans and perform quantitative measurements within these datasets are described in this thesis. These techniques were combined with a biological angiogenesis assay and used as research tools in a study comparing various different combination treatments of bone metastases.KWF KankerbestrijdingUBL - phd migration 201

Reduction in mesenchymal stem cell numbers in premature aging DNA repair deficient TTD mice

Background: Mice carrying mutations in DNA repair genes often show signs of accelerated ageing and therefore can be used as a model system to study age related diseases like osteoporosis. It has been shown that TTD mice, carrying a mutation in the nucleotide excision repair gene XPD (xeroderma pigmentosa group D), display features of ageing related osteoporosis as well as adipose tissue hypoplasia. Since both cell types involved, osteoblasts as well as adipocytes, arise from the same mesenchymal stem cell population, the aim of the current project was to study the number, proliferation and differentiation potential of these cells in TTD compared to wild type (WT) mice. This might provide us with useful information concerning the mechanism behind age-related osteoporosis and the loss of adipose tissue.Methods: Bone marrow from old TTD and WT mice was cultured under osteogenic or adipogenic conditions and analysed for alkaline phosphatase activity (ALP), mineralisation (osteoblast) and lipid deposition (adipocyte).Results: Under osteogenic conditions the number of ALP-positive colonies after 9 and 14 days of culture was significantly decreased (p=0.02) in TTD compared to WT mice. The rate at which new ALP-positive colonies are formed between day 9 and day 14 of culture has not changed between TTD and WT mice, indicating that the decrease in colony number is not due to a delay in differentiation. Mineralisation of ALP-positive colonies did not seem to be affected, with a borderline significant decrease on day 14 at the onset of mineralisation but no significant changes on day 21 of culture. Lipid deposition was strongly reduced in TTD compared to WT mice (p=0.01) after 35 days of culture.Conclusions: The observed reduction in osteoblast and adipocyte differentiation indicates a reduction of mesenchymal stem cell numbers in TTD mice. This reduction in mesenchymal stem cell numbers and the corresponding decline in osteoblast differentiation could explain the premature osteoporotic features observed in TTD mice. In line with this, the reduction of mesenchymal stem cells and adipocyte differentiation may underlie the adipose tissue hypoplasia observed in TTD mice