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RelA/p65 is a main subunit of nuclear factor-kappaB (NF-kappaB) that regulates expression of genes involved in cell growth and survival, stress response, and inflammation, but its oncogenic or tumor-suppressive function in tumorigenesis has been highly controversial. Hundreds of NF-kappaB inhibitors have been developed for targeted cancer therapy, but fail to achieve anticipated anticancer efficacy. Complexity of posttranslational modifications may contribute to tumorigenic diversity of RelA/p65, but mechanisms of action remain unclear. Here we show that phosphorylation of RelA/p65 at Ser536 functions as a tumor suppressor. In normal human colon mucosa, RelA/p65 phosphorylation at Ser536 is gradually increased with the maturation and apoptotic shedding of cryptic cells, but the phosphorylation is significantly decreased in colon tumors. In RelA/p65-silenced breast and colon cancer cells, reconstitution of a constitutively active RelA/p65, whose Ser536 was replaced by aspartic acid (named p65/S536D), triggered dramatic apoptosis and autophagy or senescence upon the cell context, by affecting the expression of a range of cell death/survival genes. Reconstitution with a phosphorylation-deficient RelA/p65 whose Ser536 was replaced by alanine (called p65/S536A) had no effect on cell growth and survival. Intratumoral delivery of p65/S536D effectively suppressed tumor growth in nude mice and was marked with apoptotic cell death. Together our data suggest that it is the phosphorylation at Ser536 that confers NF-kappaB RelA/p65 a tumor-suppressive role. In addition to driving cell death, the phosphorylation of RelA/p65 on Ser536 is also beneficial for chemosensitivity in cancer therapy. Literature reports that NF-kappaB activation contributes to chemoresistance by regulating oncogenic pathways and multi-drug resistance genes, but recent studies on senescence and chemotherapy have suggested that NF-kappaB activation is essential for chemotherapy induced senescence and tumor regression. The mechanisms underlying the contradictory observations are elusive. Here we show that site-differential phosphorylation of NF-kappaB RelA/p65 modulates chemosensitivity and results in distinct outcomes in cancer cells. Phospohrylation of RelA/p65 on Ser276, Ser536 and Ser468 were detected in RITA (reactivation of p53 and induction of tumor cell apoptosis) treated cells and RITA-resistant sublines, and they showed distinct dynamics. Ectopic expression of p65/S536D dramatically enhanced RITA sensitivity while the constitutively phosphorylated form of S276 (S276D) compromised RITA effects in treated cells. The constitutive phosphorylation of Ser468 (S468D) showed very mild effects on RITA sensitivity. In addition, p65/S536D resensitized RITA-resistant sublines to RITA treatment. P65/S536D also enhanced the doxorubicin sensitivity, but not paclitaxel in these multi-drug resistant sublines. ATP-binding cassette (ABC) transporters are critical multidrug resistant factors. We found that in the RITA-resistant sublines, multiple ABC transporter genes were upregulated, particularly the ABCC6. Further studies dissected that ABCC6 was involved in site-specific phosphorylation- related chemoresistance. P65/S536D decreased ABCC6 expression and sensitized cells to doxorubicin and RITA, but not paclitaxel that is not the substrate of ABCC6 transporter. Conversely, p65/S276D enhanced chemoresistance by upregulating ABCC6. The p65/S536D enhanced RITA chemosensitivity is also confirmed in in vivo study using tumor xenografts in nude mice. Taken together, phosphorylation of p65 on Ser536 contributes to chemosensitivity by targeting ABCC6 while Ser276 leads to chemoresistance. These findings solve the controversial issues of NF-kappaB RelA/p65 in tumorigenesis and in chemosensitivity, and are important in developing NF-kappaB targeted cancer therapy, such as inhibitors. This study also highlights that better understanding of distinct active sites on NF-kappaB RelA/p65 is necessary for discussing the tumorigenic roles of NF-kappaB and developing efficient NF-kappaB targeted therapies.

No description available.

Etude à l'aide des outils de transcriptomique de 17 cultures primaires, maintenues à l'état vivant par xénogreffes et cultures cellulaires, et issues de patients ayant présenté un adénocarcinome pancréatique. Par clustering hiérarchique basée sur l'ensemble des gènes du transcriptome tumoral, 5 patients avec dénomination anonyme se sont fortement distingués des autres patients et présentaient de façon similaire des tumeurs peu différenciées sur le plan histologique et une survie péjorative de moins de 8 mois. Dans cette population de « courts survivants », un total de 942 gènes exprimés de façon significativement différentielle a été retrouvé. Parmi ces gènes, 439 gènes sont apparus significativement sous exprimés et 505 gènes significativement surexprimés (fold change ≥2). L'analyse par GO a montré que parmi ces 942 gènes différentiellement exprimés, nous avons retrouvé un enrichissement important chez les courts survivants, des gènes impliqués dans le cycle cellulaire et l'activité mitotique, la réponse cellulaire au stress, le métabolisme cellulaire ainsi que le métabolisme de l'ADN et l'organisation chromosomique. Par ailleurs, nous avons choisi parmi les 17 cultures primaires, les 3 lignées cellulaires les plus sensibles et les 3 les plus résistantes aux drogues selon les résultats des tests de « Chimiogramme ». Plusieurs gènes ont été identifiés comme spécifiquement surexprimés ou sous-exprimés en relation avec une sensibilité ou une résistance particulières des cellules aux drogues utilisées. Nous avons identifié 671 gènes associés à la gemcitabine, 1107 à l'oxaliplatine, 308 au 5-FU et seulement 34 et 46 au docétaxel et au SN38 respectivement. / We developed an efficient strategy in which PDAC samples from 17 consecutive patients were collected by Endoscopic Ultrasound-Guided Fine-Needle Aspiration (EUS-FNA) or surgery and preserved, by an original approach, as breathing tumors by xenografting and as a primary culture of epithelial cells. Transcriptomic analysis was performed from breathing tumors by an Affymetrix approach. We observed a significant heterogeneity in the RNA expression profile of tumors. However, the bioinformatic analysis of this data was able to discriminate between patients with long- and short-term survival corresponding to patients carrying poorly-differentiated PDAC tumors respectively. We identified 942 genes with statically different expression. Among these genes, 439 were under-expressed and 505 genes over-expressed (fold change ≥2) in short survivors. Primary culture of cells allowed us to analyze their relative sensitivity to anticancer drugs in vitro by a "Chemogram", by similarity with the antibiogram for microorganisms, establishing an individual profile of drug sensitivity. As expected, the response was patient-dependent. Interestingly, we also found that the transcriptome analysis predict the sensitivity of cells to the five anticancer drugs the most frequently used to treating patients with PDAC. In conclusion, using this approach, we found that the transcriptomic analysis could predict the sensitivity to anticancer drugs and the clinical outcome of patients with PDAC.

Attrition rates for anticancer drugs are much higher than any other therapeutic area. Only 5%#37; of the agents that demonstrate anticancer activity in the preclinical stages of development demonstrate clinical efficacy in phase III trials. This high attrition rate becomes alarming when we consider that the cost of research and development can amount to 1 billion dollars. To exacerbate this problem, many new cancer drugs are being discontinued, withdrawn or suspended. The reasons for this high attrition rate are complex and may be partly attributed to suboptimal preclinical strategies such as the use of two-dimensional (2D) cell culture systems to evaluate new agents during the development and testing stages. Cancer cells cultured in 2D do not mimic the complexity of the three-dimensional (3D) milieu of tumors in vivo. There is overwhelming evidence that in vitro 3D culture systems more accurately reflect the tumor microenvironment and present better predictive value for assessing the efficacy of new chemotherapeutic agents. The development of 3D culture systems for anticancer drug development remains an unmet need. Despite progress, a simple, rapid, scalable and inexpensive 3D-tumor model that recapitulates in vivo tumorigenesis is lacking. Herein, we report on the development and characterization of a 3D nanofibrous scaffold produced by electrospinning a mixture of poly(lactic-co-glycolic acid) (PLGA) and a block copolymer of polylactic acid (PLA) and mono-methoxy polyethylene glycol (mPEG) designated as 3P. Cancer cells cultured on the 3P scaffold formed tight aggregates similar to in vivo tumors, referred to as tumoroids that depended on the topography and net charge of the scaffold. 3P scaffolds induced tumor cells to undergo the epithelial-to-mesenchymal transition (EMT) as demonstrated by up-regulation of vimentin and loss of E-cadherin expression. 3P tumoroids showed higher resistance to anticancer drugs than the same tumor cells grown as monolayers. Inhibition of ERK and PI3K signal pathways prevented EMT conversion and reduced tumoroid formation, diameter and number. Fine needle aspirates, collected from tumor cells implanted in mice when cultured on 3P scaffolds formed tumoroids, but showed decreased sensitivity to anticancer drugs, compared to tumoroids formed by direct seeding. These results show that 3P scaffolds provide an excellent platform for producing tumoroids from tumor cell lines and from biopsies and that the platform can be used to culture patient biopsies, test for anticancer compounds and tailor a personalized cancer treatment.

Whilst progress has been made in reducing mortality in some cancers, mortality rates remain high in many cancers and there is a need to develop novel therapeutic strategies. In this thesis, various pharmacological strategies designed to enhance the activity of existing therapeutic drugs were evaluated. Cancer cells are dependent upon aerobic glycolysis (the Warburg effect) and glutamine uptake. Using clinically approved tyrosine kinase inhibitors and Bortezomib, significant enhancement of chemosensitivity was observed when used in combination with inhibitors of lactate dehydrogenase (Gossypol) and pyruvate kinase dehydrogenase (Dichloroacetate). In contrast, depletion of glutamine from media had to be extensive in order to induce cell death and cell death only occurred after prolonged exposure to glutamine-deprived conditions. This suggests that glutamine depletion strategies alone are unlikely to be successful but may be useful in combination with other agents targeting glutamine addiction in cancer cells. Finally, Temozolomide (TMZ) is an important drug in the treatment of glioblastomas but its activity is reduced by resistance mechanisms including O6 methyl guanine methyltransferase (MGMT) and mismatch repair (MMR). This thesis has identified analogues of TMZ (EA02-45, EA02-59, EA02-64 and EA02-65) that are MGMT and MMR independent in terms of inducing cell kill in vitro. These compounds are promising leads for future development. In conclusion, this thesis has demonstrated that interfering with the metabolic phenotype of cancer can enhance the activity of existing drugs and identified novel analogues of TMZ that circumvent drug resistance mechanisms that hamper the efficacy of TMZ.

Despite therapeutic advances, colorectal cancer still has a 45% mortality rate, and one of the most crucial problems is the development of acquired resistance to treatment with anticancer drugs. Thus the aims of this project are to develop drug-resistant colon cancer cell lines in order to identify mechanisms of resistance for the most commonly drugs used in colorectal cancer: 5-fluorouracil, oxaliplatin, and irinotecan. Following evaluation of drug sensitivity to these agents in an initial panel of eight colorectal cancer cell lines, 3 lines (DLD-1, KM-12 and HT-29) were selected for the development of 5-FU (3 lines), oxaliplatin (2) and irinotecan (1) resistant sublines by continuous drug exposure, with resistance confirmed using the MTT assay. Consistently resistant sublines were subject to a „stable isotope labelling with amino acids in cell culture‟ (SILAC) approach and a MudPIT proteomics strategy, employing 2D LC and Orbitrap Fusion mass spectrometric analysis, to identify novel predictive biomarkers for resistance. An average of 3622 proteins was quantified for each resistant and parent cell line pair, with on average 60-70 proteins up-regulated and 60-70 down-regulated in the drug resistant sublines. The validity of this approach was further confirmed using immunodetection techniques. These studies have provided candidate proteins which can be assessed for their value as predictive biomarkers, or as therapeutic targets for the modulation of acquired drug resistance in colorectal cancer.

L'hétérogénéité de l'adénocarcinome canalaire pancréatique (ADCP) est l'obstacle majeur au traitement efficace des patients. En effet, les caractéristiques cliniques et la sensibilité aux traitements sont associés à un phénotype donné et sont plutôt régis à un niveau transcriptomique. Nous avons donc analysé le transcriptome de xénogreffes provenant des patients (Patients Derived Xenografts : PDX) lors des biopsies de tumeurs ou de pièces chirurgicales. Après extraction d’ARN, nous avons trouvé une signature moléculaire capable de diviser les patients en deux groupes, en fonction de leur survie. Nous avons également montré que la réponse autraitement pouvait être prédite par l‘analyse transcriptomique. Nous avons ensuite analysé les tumeurs et leurs stromas, et mis en évidence deux soustypesde stromas et deux sous-types de tumeurs, définis par la transcriptomique basée sur l'ARN, ou la méthylation de l'ADN. Nous avons étudié la réponse aux traitements administrés seuls ou en combinaison avec des chimiothérapies de routine. Nous avons mis en évidence des sous-groupes de patients plus chimiosensibles à certains traitements. Tous ces résultats sont encourageants,mais pas encore applicables en pratique clinique. Nous développons maintenant les organoïdes, véritable représentation de la tumeur en 3dimensions. Contrairement aux PDX, les organoïdes nous permettent d'obtenir des résultats rapidement exploitables. Nous pensons que dans un avenir proche, le traitement des cancers du pancréas sera précédé d'une caractérisation moléculaire étendue afin de sélectionner les traitements les plus appropriés et de pouvoir enfin proposer une médecine personnalisée. / Heterogeneity of Pancreatic Ductal AdenoCarcinoma (PDAC) has become the majorimpediment to the effective treatment of patients. Clinical outcome and sensitivity to treatments are associated with a given phenotype and associated at a transcriptomic level. Recent data indicate that studying the expressionof a selected gene set could inform selection of the most appropriate treatments.We areoptimizing this approach by analysing transcriptome of Patient-Derived Xenografts (PDX)from surgical as well as endoscopic ultrasound-guided fine needle aspiration (EUS-FNA)biopsies of tumors, as a source of RNA. We have found a molecularsignature capable of dividing patients into two groups, function of theirsurvival.Independently, we have shown that treatment response pattern can also be foundat a transcriptomic level. We thenanalysed tumors and their stromas, and have found two sub-types of stromas and two sub-types of tumors. These wereindinstinctly defined by RNAseq-based transcriptomics, or DNA methylation. We also studied response to treatments administered alone or incombination to routine chemotherapies. All these results are encouraging, but not yetapplicable in clinical pratice. We are now developing the PDAC Biopsy DerivedPancreatic Cancer Organoids (BDPCO): BDPCO culture represents an excellent source of “exvivo” material. Unlike PDX, which take many months to grow, BDPCO allow us to obtainexploitable material rapidly useful for clinical application. We are convinced that in the near future, the treatment ofpancreatic cancers will be preceded by an extensive molecular characterization of cancercells in order to select the most appropriate treatments.

Neurons in the Locus coeruleus (LC) play an important role in the central CO2 chemosensitivity. However, the molecular mechanisms for neuronal CO2 chemosensitivity remain unclear. To demonstrate the expression of pH/CO2 sensitive ion channels, we screened the inward rectifier K+ channels (Kir) and transient receptor protein (TRP) channels, as parallel studies in this lab suggested that certain Kir and TRP channels are involved in neuronal responses to high levels of CO2. Our results showed that several members of the Kir and TRP channel families were robustly expressed in the LC neurons at the mRNA level. Of particular interest are TRPC5, Kir4.1 and Kir5.1 channels that are all pH-sensitive. The rich expression of various pH-sensitive Kir and TRP channels suggests that these ion channels are likely to play a role in the chemosensitivity of LC neurons.

Background: Human head and neck squamous cell carcinoma (HNSCC) fundamentally vary in their susceptibility to different cytotoxic drugs and treatment modalities. There is at present no clinically accepted test system to predict the most effective therapy for an individual patient. Methods: Therefore, we established tumor-derived slice cultures which can be kept in vitro for at least six days. Upon treatment with cisplatin, docetaxel and cetuximab, slices were fixed and paraffin sections were cut for histopathological analysis. Results: Apoptotic fragmentation, activation of caspase 3, and cell loss were observed in treated tumor slices. Counts of nuclei per field in untreated compared to treated slices deriving from the same tumor allowed estimation of the anti-neoplastic activity of individual drugs on an individual tumor. Conclusion: HNSCC-derived slice cultures survive well in vitro and may serve to improve personalized therapies, but also to detect mechanisms of tumor resistance by harvesting surviving tumor cells after treatment.