Le cancer du sein est la première cause de mortalité chez la femme par cancer. Différents travaux ont montré l’implication des fibroblastes associés au cancer (CAFs) dans la résistance thérapeutique, ainsi que leur rôle dans le développement de cancer du sein. L’adrénomédulline (AM) joue un rôle crucial dans la croissance des tumeurs. Dans notre étude, nous nous sommes interrogés sur l’apport de l’AM sécrétée par la composante majeure du stroma tumoral les CAFs, dans le développement du cancer du sein. Dans cette étude nous avons montré que les CAFs isolés à partir des tumeurs issues du cancer du sein, présentent une augmentation de l’expression du système d’AM (AM et ses récepteurs) par rapport aux fibroblastes non activés (NHDFs). Nos études dans le modèle d’angiogenèse in vivo montrent que les CAFs sont plus compétents à mettre en place une vascularisation stable et fonctionnelle par rapport aux NHDFs. Cependant, le traitement des souris avec des anticorps anti récepteurs de l’AM (αAMRs) bloque la vascularisation. De plus, les xénogreffes issues du mélange MCF-7/CAFs génèrent des tumeurs plus importantes par rapport aux tumeurs issues de MCF-7 seules ou combinées aux NHDFs. Les souris traitées par voie i.p. avec des αAMRs ou l’antagoniste AM22-52, montrent une inhibition de la croissance tumorale des xénogreffes. Les études immunohistochimiques montrent une vascularisation bien établie chez le groupe MCF-7/CAFs, qui est altérée suite au blocage du système de l’AM.Notre étude montre le rôle important de l’AM sécrétée par les CAFs dans le processus de la tumorigenèse du cancer du sein. / Breast cancer is the leading cause of death among women with cancer. Various studies have shown the involvement of cancer associated fibroblasts (CAFs) in this therapeutic resistance and their role in the development of the tumor. Adrenomedullin (AM) plays a critical role in tumor growth. In our study, we asked about the contribution of AM secreted by the major component of the tumor stroma CAFs in breast cancer development. In this study, we demonstrate that CAFs isolated from tumors derived from breast cancer, showed an increase in the expression of AM (AM and its receptors) compared to non-activated fibroblasts (NHDFs). Our studies in vivo angiogenesis model shows that CAFs are more competent to set-up a stable and functional vasculature compared to NHDFs. However, treatment of mice with antibodies anti AM receptor (αAMRs) blocks vascularization, indicating the role of AM secreted by CAFs in the establishment of neovascularization. Additionally, xenografts from MCF-7 mixture / CAFs generate larger tumors compared to tumors from MCF-7 alone or combined with NHDFs. Mice treated, mice treated by intra-peritoneal (i.p.) injection with αAMRs or antagonist AM22-52, show inhibition of tumor growth of xenografts. Immunohistochemical studies show an established vasculature in the MCF-7 / CAFs group, which is impaired due to the blocking of the AM system.Our study shows the important role of the AM secreted by CAFs in the process of breast cancertumorigenesis. It provides an evidence of the effectiveness of a therapy anti-AM, which will target as one of the most predominant components of breast cancer tumor microenvironment.

G3BP1 and G3BP2 are members of a highly conserved family of multi-functional RNA binding proteins, which appear to co-ordinate signal transduction and post-transcriptional gene regulation. Both proteins are over-expressed in cancer, and G3BP1 promotes cell proliferation and survival. Aberrant expression of various RNA binding proteins is common in cancer, and several of these proteins influence tumorigenesis. Therefore, detailed examination of RNA binding proteins, such as G3BPs, may provide insights into the post-transcriptional mechanisms underlying tumorigenesis. Tumours arise as a consequence of genetic mutation or alteration, which often result from stress-induced DNA damage. Cancer progression is facilitated by various epigenetic stress adaptation mechanisms. Stressful stimuli induce transitory translational shut-off, mediated by phosphorylation of eukaryotic initiation factor alpha;(eIF2alpha;). This phosphorylation event leads to formation of discrete cytoplasmic foci known as stress granules (SGs), which are translationally-silent sites of mRNA sorting. It was initially thought that an RNA-binding protein, T-cell internal antigen 1 (TIA-1), was instrumental in both the formation and functioning of SGs, because over-expression of TIA-1 induces spontaneous SGs and concomitantly causes a decrease in reporter gene expression. It is now clear that SG content can change depending on the type of stress, and that various proteins, including G3BP1, can induce spontaneous SGs. In vitro evidence previously implicated both G3BP1 and G3BP2 as endoribonucleases, so it was suggested that G3BPs act to target mRNA for decay at the SG. This project sought to further investigate this proposal, and in this way gain insight into the specific function of G3BPs in post-transcriptional regulation during tumorigenesis. Characterisation of G3BP1 and G3BP2 expression and localisation patterns in human cells and cancer was necessary before functional analyses in human cell systems could be undertaken. Both proteins were found to be over-expressed in breast cancer, irrespective of cancer stage or grade. G3BP1 and G3BP2 were also expressed in all human cell lines tested, despite previously observed tissue-specific expression. These results support the notion that G3BP expression is switched on in parallel with cell proliferation, and as such, may influence tumorigenesis. The results of further analyses suggested that the diverse functions attributed to G3BP1 and G3BP2 may be facilitated by isoform-specific expression, various post-translational modifications and sub-cellular localisation. Despite the absence of a canonical endoribonuclease domain, it was previously reported that site-specific phosphorylation of G3BP1 enables the protein to degrade a synthetic c-myc RNA substrate in vitro. This finding implicated G3BP in the specific regulation of a proto-oncogene. Tailored reporter assays were thus designed in order to address the in vivo consequences of G3BP's putative endoribonuclease activity. Contrary to expectations, all G3BP family members increased or maintained the expression of a range of reporters, at both the mRNA and protein level, irrespective of the presence of any particular cis-acting element, coding sequence or promoter. These results support the emerging notion that G3BPs positively affect the expression of at least some of their target mRNAs, and may also indirectly promote transcription. In contrast to the theory that G3BPs degrade proto-oncogenic mRNA/s, these findings are consistent with a role for G3BP in promoting cell proliferation and survival. Further analyses showed that G3BP1 and G3BP2 simultaneously increased reporter gene expression and induced SG formation. These findings highlighted the fact that SGs are dynamic sorting stations for mRNAs, and not merely sites of stalled translation. This result also supports the notion that a variety of proteins may be recruited to the SG to facilitate a multitude of mRNA fates. Although the precise role of the SG in stress adapation is not known, it is clear that an appropriate integrated stress response (ISR) is required for cells to survive in sub-optimal conditions. It was found that specific G3BP1 knockdown inhibited SG formation and cell survival, and this appeared to occur downstream of eIF2alpha; phosphorylation. The phosphorylation of eIFalpha; is the only factor known to be necessary for SG formation and cell survival. This data is the first to implicate SG formation itself, downstream of eIF2alpha; phosphorylation, in the survival phase of the ISR. The results also suggest that G3BP1 plays a pivotal role in the post-transcriptional mechanisms underlying stress adaptation. To facilitate future analysis of G3BP roles in the regulation of specific transcripts and in SG biology, a pilot study to identify G3BP RNA ligands was undertaken. Immunoprecipitation of epitope-tagged G3BP1 from stable cell lines facilitated purification and isolation of RNA in association with G3BP1. Specific RNA transcripts were subsequently detected and identified by microarray. Many genes were enriched in the G3BP1 immunoprecipitate. Transcript enrichment in the control immunoprecipitate was comparatively weak and seemingly random, suggesting that several replicates will enable generation of a reliable target list. This work forms a promising basis for further investigations into G3BP functionality, and also provides a platform for broader and more large-scale analyses of the mechanisms of post-transcriptional gene regulation. The work presented in this thesis addressed the potential post-transcriptional mechanisms by which the G3BP family of proteins mediate cell proliferation and survival. Both G3BP1 and G3BP2 were shown to be over-expressed in tumours and each appeared to promote reporter gene expression. G3BP1 was also found to play a pivotal role in stress adaptation. A technique to identify novel RNA ligands was assessed, and it was found that G3BP1 may interact with various mRNA transcripts. It is hypothesised that the G3BP family of proteins, and in particular G3BP1, function to determine the fate of specific RNAs in response to cellular stress and other stimuli. In this way, G3BP proteins may facilitate appropriate responses to extra-cellular stimuli which allow for cell proliferation and survival.

<p>Correa, P. 2002. Vitamin D and its receptor in parathyroid tumors. Acta Universitatis Upsaliensis. Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine 1186. 49 pp. Uppsala. ISBN 91-554-541-0 </p><p>Hyperparathyroidism (HPT) is characterized by tumor development in the parathyroid glands and excessive production of parathyroid hormone. Parathyroidectomy is the only considered therapy for the majority of patients. </p><p>LOH (loss of heterozygosity) analysis revealed putative tumor suppressor genes on chromosome regions 1p and 11q in tumors from patients with truly mild hypercalcemia.</p><p>Active vitamin D [1,25(OH)2D3] and its receptors, the vitamin D receptor (VDR), are essential regulators of the calcium homeostasis and are involved in HPT development. The VDR-FokI polymorphism, coupled to bone mineral density, was found not to be associated to development of primary HPT (pHPT). The total VDR mRNA levels is reduced in adenomas of pHPT as well as in hyperplastic glands of secondary HPT (sHPT). The VDR exon 1f transcripts were exclusively downregulated in the adenomas of pHPT, suggesting default regulation of the tissue-specially expressed VDR 1f promoter. The cytochrome P450 enzymes responsible for synthesis and degradation of 1,25(OH)2D3, namely vitamin D3 25-hydroxylase (25-hydroxylase), 25-hydroxyvitamin D3 1a-hydroxylase (1a-hydroxylase) and 25-hydroxyvitamin D3 24-hydroxylase (24-hydroxylase) were found to be expressed in normal and pathological parathyroid glands. Tumors of pHPT and sHPT demonstrated increased 1a-hydroxylase and reduced 24- and 25-hydroxylase expression, suggesting an augmented local production of active vitamin D. In contrast, parathyroid carcinomas displayed reduced expression of all three hydroxylases. The gained knowledge of vitamin D metabolism and catabolism in parathyroid tumors may indicate possibilities for novel treatment of sHPT and perhaps pHPT.</p>

<p>Hyaluronan (HA), a structural component in the extracellular matrix (ECM), has been recognized as a signaling molecule. It is important during various biological activities such as embryogenesis, angiogenesis, wound healing and tumor progression. Increased amount of hyaluronan during embryonic development is necessary for cell migration and differentiation, but the increased production of hyaluronan by tumor cells or tissue fibroblasts is correlated to poor prognosis for tumor progression and chronic inflammation, respectively. Therefore, understanding the mechanisms regulating HA-enriched matrices and the roles of HA in the biological functions is of fundamental biological importance.</p><p>Four novel findings are described in this thesis: (1) HA fragments (HA12) and the known angiogenic factor FGF-2 promote endothelial cell differentiation by induction of common but also distinct sets of genes, particularly, upregulation of the chemokine <i>CXCL1/GRO1</i> gene is necessary for HA12-induced angiogenesis and this effect is dependent on CD44 activation. (2) High concentrations of hyaluronan suppress PDGF-BB-induced fibroblasts migration and PDGFRβ tyrosine phosphorylation upon activation of hyaluronan receptor CD44, probably by recruiting a CD44-associated phosphatase to the PDGFRβ. (3) PDGF-BB stimulates <i>HAS2</i> transcriptional activity and HA synthesis through upregulation of MAP kinase and PI3 kinase signaling pathways in human dermal fibroblasts. (4) Specific suppression of <i>HAS2</i> gene in the invasive breast cancer cell line Hs578T by RNA interference (RNAi) leads to a less aggressive phenotype of breast tumor cells. This suppressive effect can be reversed by exogenously added hyaluronan.</p><p>In conclusion, binding of hyaluronan to CD44 plays an important role in cell signaling, inflammation and tumor progression. Further studies are required to elucidate the molecular mechanisms through which hyaluronan levels are regulated under physiological or pathological conditions, and to explore compounds involved in hyaluronan accumulation and activity as targets for therapies of chronic inflammation and tumors.</p>

New technologies to probe the global output of the normal and cancer genomes have recently reached widespread use. The resulting genomewide gene expression profiles, e.g, a gene expression measurement per gene and per tissue sample, remain challenging to analyze and interpret, but have already provided new insights into the pathophysiology of cancer and towards personalized care. In vitro cell culture-based experimental models are used to elucidate cancer onset and progression because experimentation in humans is difficult practically and ethically unacceptable, and because they provide simplified, reproducible and controlled systems to test hypotheses. The thyroid tumors and their in vitro experimental models are particularly suited to compare the molecular phenotypes of experimental models and tumors. From one type of cell, the thyrocyte, at least five distinct benign and malignant tumors can arise. In addition, many immortalized tumor-derived cell lines and primary cultures models of these cells exist. This thesis has focused on the bioinformatic comparison of these in vitro models to the in vivo tumors, from the point of view of their gene expression profiles, to gain insight into the pathogenesis of thyroid tumors, and of tumors in general. In a first study, we showed that primary cultures of freshly isolated normal thyroid cells where proliferation and differentiation through the TSHR/cAMP pathway was chronically activated experimentally resemble specifically the autonomous thyroid adenomas, a type of benign thyroid tumor, and provide insight into a general mechanism of tumor progression: the suppression of negative feedbacks that normally restrain excessive cell division. Subsequently, we found that immortalized thyroid tumor-derived cell lines have converged to a common phenotype regardless of their tumor subtype of origin. A TSHR/cAMP thyroid cell differentiation signature, derived from data obtained for the first study, was used to show that the cell lines were dedifferentiated. Accordingly, we showed that the cell lines resemble most the phenotype of the more dedifferentiated, clinically aggressive anaplastic thyroid cancers. Finally, using large databases of gene expression profiles publicly available, we extended the comparison of cell lines and tumors to cancers of five other organs: breast, colon, kidney, ovary and lung. We discuss the correct use of these models and advance an hypothesis regarding the nature of the state to which these cells have converged: they could represent a surviving subpopulation of tumors cells, cancer stem cells, capable of initiating and maintaining tumor growth. As other technologies designed to perturb the genome in experimental models are emerging, careful characterization and validation of the experimental models are needed to extrapolate the results in vivo. Although many differences exist between the experimental models and their in vivo disease counterparts, focusing on the similarities could provide a path to design successful therapeutic interventions more systematically.

New technologies to probe the global output of the normal and cancer genomes have recently reached widespread use. The resulting genomewide gene expression profiles, e.g, a gene expression measurement per gene and per tissue sample, remain challenging to analyze and interpret, but have already provided new insights into the pathophysiology of cancer and towards personalized care. In vitro cell culture-based experimental models are used to elucidate cancer onset and progression because experimentation in humans is difficult practically and ethically unacceptable, and because they provide simplified, reproducible and controlled systems to test hypotheses. The thyroid tumors and their in vitro experimental models are particularly suited to compare the molecular phenotypes of experimental models and tumors. From one type of cell, the thyrocyte, at least five distinct benign and malignant tumors can arise. In addition, many immortalized tumor-derived cell lines and primary cultures models of these cells exist. This thesis has focused on the bioinformatic comparison of these in vitro models to the in vivo tumors, from the point of view of their gene expression profiles, to gain insight into the pathogenesis of thyroid tumors, and of tumors in general. In a first study, we showed that primary cultures of freshly isolated normal thyroid cells where proliferation and differentiation through the TSHR/cAMP pathway was chronically activated experimentally resemble specifically the autonomous thyroid adenomas, a type of benign thyroid tumor, and provide insight into a general mechanism of tumor progression: the suppression of negative feedbacks that normally restrain excessive cell division. Subsequently, we found that immortalized thyroid tumor-derived cell lines have converged to a common phenotype regardless of their tumor subtype of origin. A TSHR/cAMP thyroid cell differentiation signature, derived from data obtained for the first study, was used to show that the cell lines were dedifferentiated. Accordingly, we showed that the cell lines resemble most the phenotype of the more dedifferentiated, clinically aggressive anaplastic thyroid cancers. Finally, using large databases of gene expression profiles publicly available, we extended the comparison of cell lines and tumors to cancers of five other organs: breast, colon, kidney, ovary and lung. We discuss the correct use of these models and advance an hypothesis regarding the nature of the state to which these cells have converged: they could represent a surviving subpopulation of tumors cells, cancer stem cells, capable of initiating and maintaining tumor growth. As other technologies designed to perturb the genome in experimental models are emerging, careful characterization and validation of the experimental models are needed to extrapolate the results in vivo.

Correa, P. 2002. Vitamin D and its receptor in parathyroid tumors. Acta Universitatis Upsaliensis. Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine 1186. 49 pp. Uppsala. ISBN 91-554-541-0 Hyperparathyroidism (HPT) is characterized by tumor development in the parathyroid glands and excessive production of parathyroid hormone. Parathyroidectomy is the only considered therapy for the majority of patients. LOH (loss of heterozygosity) analysis revealed putative tumor suppressor genes on chromosome regions 1p and 11q in tumors from patients with truly mild hypercalcemia. Active vitamin D [1,25(OH)2D3] and its receptors, the vitamin D receptor (VDR), are essential regulators of the calcium homeostasis and are involved in HPT development. The VDR-FokI polymorphism, coupled to bone mineral density, was found not to be associated to development of primary HPT (pHPT). The total VDR mRNA levels is reduced in adenomas of pHPT as well as in hyperplastic glands of secondary HPT (sHPT). The VDR exon 1f transcripts were exclusively downregulated in the adenomas of pHPT, suggesting default regulation of the tissue-specially expressed VDR 1f promoter. The cytochrome P450 enzymes responsible for synthesis and degradation of 1,25(OH)2D3, namely vitamin D3 25-hydroxylase (25-hydroxylase), 25-hydroxyvitamin D3 1a-hydroxylase (1a-hydroxylase) and 25-hydroxyvitamin D3 24-hydroxylase (24-hydroxylase) were found to be expressed in normal and pathological parathyroid glands. Tumors of pHPT and sHPT demonstrated increased 1a-hydroxylase and reduced 24- and 25-hydroxylase expression, suggesting an augmented local production of active vitamin D. In contrast, parathyroid carcinomas displayed reduced expression of all three hydroxylases. The gained knowledge of vitamin D metabolism and catabolism in parathyroid tumors may indicate possibilities for novel treatment of sHPT and perhaps pHPT.

Hyaluronan (HA), a structural component in the extracellular matrix (ECM), has been recognized as a signaling molecule. It is important during various biological activities such as embryogenesis, angiogenesis, wound healing and tumor progression. Increased amount of hyaluronan during embryonic development is necessary for cell migration and differentiation, but the increased production of hyaluronan by tumor cells or tissue fibroblasts is correlated to poor prognosis for tumor progression and chronic inflammation, respectively. Therefore, understanding the mechanisms regulating HA-enriched matrices and the roles of HA in the biological functions is of fundamental biological importance. Four novel findings are described in this thesis: (1) HA fragments (HA12) and the known angiogenic factor FGF-2 promote endothelial cell differentiation by induction of common but also distinct sets of genes, particularly, upregulation of the chemokine CXCL1/GRO1 gene is necessary for HA12-induced angiogenesis and this effect is dependent on CD44 activation. (2) High concentrations of hyaluronan suppress PDGF-BB-induced fibroblasts migration and PDGFRβ tyrosine phosphorylation upon activation of hyaluronan receptor CD44, probably by recruiting a CD44-associated phosphatase to the PDGFRβ. (3) PDGF-BB stimulates HAS2 transcriptional activity and HA synthesis through upregulation of MAP kinase and PI3 kinase signaling pathways in human dermal fibroblasts. (4) Specific suppression of HAS2 gene in the invasive breast cancer cell line Hs578T by RNA interference (RNAi) leads to a less aggressive phenotype of breast tumor cells. This suppressive effect can be reversed by exogenously added hyaluronan. In conclusion, binding of hyaluronan to CD44 plays an important role in cell signaling, inflammation and tumor progression. Further studies are required to elucidate the molecular mechanisms through which hyaluronan levels are regulated under physiological or pathological conditions, and to explore compounds involved in hyaluronan accumulation and activity as targets for therapies of chronic inflammation and tumors.

Diss. (sammanfattning) Uppsala : Uppsala universitet, 2006. / Härtill 4 uppsatser.

Malgré les avancées récentes, le cancer reste la première cause de mortalité en France avec ~ 150000 décès recensés par an (INCa 2012). Notamment, le cancer broncho-pulmonaire est l’un des plus agressifs, avec 29100 décès en 2011. La survie à cinq ans de seulement 10% des patients atteints des cancers du poumon non à petites cellules (NSCLC, 80% des cancers bronchiques), pose un problème d’ordre scientifique, médical et de santé publique. Il est communément admis qu’une sous-population de la tumeur acquiert en raison d’une instabilité génétique de nouvelles propriétés agressives nécessaires à sa dissémination, sa prolifération et une plus grande résistance aux chimiothérapies. Une meilleure compréhension de ces propriétés tumorales constitue un enjeu majeur pour prévenir à terme cette progression maligne. Nous avons axé notre recherche sur la macro-autophagie, un processus catabolique lysosomal essentiel à l’homéostasie cellulaire et sur un de ses substrats SQSTM1 (séquestosome ou p62). Au moment où j’ai initié ma thèse, une relation étroite entre l’autophagie, SQSTM1 et la progression tumorale venait d’être mise en lumière. Plusieurs membres de la machinerie autophagique sont fréquemment mutés/déletés dans les cancers. De façon paradoxale, l’autophagie peut également permettre la survie des cellules tumorales face à l’hypoxie, la carence nutritionnelle ou les chimiothérapies. / Despite recent advances, cancer remains the leading cause of death in France with~150,000 annual deaths (INCA, 2012). Notably, lung cancer is one of the most aggressive, with 29 100 deaths in 2011. The five-year survival is only 10 % of patients with lung cancer non-small cell (NSCLC, 80% of lung cancers), so it’s a medical/scientific challenge, and public health problem. Due to genetic instability, it’s commonly accepted that a subpopulation of tumor acquires new aggressive properties for its dissemination, its proliferation and greater resistance to chemotherapy. A better understanding of these tumor properties is a major issue to prevent this malignant progression. We focused our research on macro-autophagy, a lysosomal catabolic process essential for cellular homeostasis, and alos on one of its substrates SQSTM1 (Sequestosome or p62). When I started my PhD, a close relationship between autophagy, SQSTM1 and tumor progression had been highlighted. Several members of the autophagic machinery are frequently mutated/deleted in cancers. Paradoxically, autophagy can also allow the survival of tumor cells under hypoxia, nutritional deficiency or chemotherapy. How could we understand these conflicting functions, considering that the only autophagy substrates known are long half-lives proteins, damaged organelles and scaffold SQSTM1? Thus, SQSTM1 is essential for RasV12 driven oncogenesis (A Duran et al, Cancer Cell 2008).