Phytochemical mediated-modulation of the expression and transporter function of breast cancer resistance protein at the blood-brain barrier:an in-vitro study

Clinical translation of BCRP inhibitors have failed due to neurotoxicity and novel approaches are required to identify suitable modulators of BCRP to enhance CNS drug delivery. In this study we examine 18 compounds, primarily phytochemicals, as potential novel modulators of AhR-mediated regulation of BCRP expression and function in immortalised and primary porcine brain microvascular endothelial cells as a mechanism to enhance CNS drug delivery. The majority of modulators possessed a cellular viability IC50 > 100 µM in both cell systems. BCRP activity, when exposed to modulators for 1 hour, was diminished for most modulators through significant increases in H33342 accumulation at < 10 µM with 2,6,4-trimethoflavone increasing H33342 intracellular accumulation by 3.7–6.6 fold over 1–100 µM. Western blotting and qPCR identified two inducers of BCRP (quercetin and naringin) and two down-regulators (17-β-estradiol and curcumin) with associated changes in BCRP efflux transport function further confirmed in both cell lines. siRNA downregulation of AhR resulted in a 1.75 ± 0.08 fold change in BCRP expression, confirming the role of AhR in the regulation of BCRP. These findings establish the regulatory role AhR of in controlling BCRP expression at the BBB and confirm quercetin, naringin, 17-β-estradiol, and curcumin as novel inducers and down-regulators of BCRP gene, protein expression and functional transporter activity and hence potential novel target sites and candidates for enhancing CNS drug delivery.

The human organic cation transporter OCT1 mediates high affinity uptake of the anticancer drug daunorubicin

Les anthracyclines tels que la doxorubicin et la daunorubicin sont une famille de médicaments anticancéreux hydrophiles qui doivent être transportés dans les cellules afin d’exercer leur action par intercalation à l’ADN dans le noyau cellulaire. Ceci mène à la perturbation du métabolisme de l’ADN et entraine la mort cellulaire. Les anthracyclines sont utilisés pour le traitement d’une variété de cancers incluant la leucémie, les lymphomes, le cancer du sein, le cancer des poumons et le cancer des ovaires. Étant donné que le transport actif des anthracyclines dans les cellules a partiellement été démontré, le transporteur spécifique impliqué dans ce processus n’est pas encore connu. En utilisant un modèle de cancer des ovaires, la lignée cellulaire TOV2223G, nous avons démontré que des substrats spécifiques au transporteur de cations organiques 1 (OCT1), notamment la ergothionéine, la thiamine et la phenformin, ont partiellement inhibé l’absorption de la daunorubicin en différence de la carnitine qui est un substrat de haute affinité des transporteurs CT2 et OCTN2. Ces résultats suggèrent que les transporteurs organiques spécifiques au transport de la carnitine ne sont pas impliqués dans le transport des anthracyclines. Ainsi, nos résultats ont démontré que l’absorption de la daunorubicin est orchestrée par le transporteur OCT1 dans les cellules TOV2223G (Km ~ 5 μM) et des concentrations micromolaires de choline ont complètement abolies l’absorption de la drogue. De plus, un ARN sh dirigé contre OCT1 a réprimé son expression protéique, ce qui a été confirmé par la technique d’immuno-buvardage en utilisant un anti-OCT1 anticorps. Les cellules déficientes en OCT1 n’ont pas été capables d’absorber la daunorubicin et ont été plus résistantes à l’action de la drogue par rapport aux cellules contrôle. La transfection des cellules HEK293T avec un plasmide construit de façon à faire exprimer OCT1 comme protéine de fusion avec la protéine fluorescente EYFP a montré que celle-ci est localisée dans la membrane plasmique. Les cellules transfectées ont été capables d’absorber cinq fois plus de daunorubicin comparé aux cellules contrôles. Cette étude est, selon nous, la première à démontrer que OCT1 est un transporteur de haute affinité des anthracyclines. Ainsi, nous avons émis l’hypothèse que des défauts de OCT1 peuvent contribuer à l’efficacité de la réponse des cellules cancéreuses à la chimiothérapie avec les anthracyclines.

La résistance à l’insuline en insuffisance rénale chronique et le risque de développer un diabète de type 2 : un cercle vicieux

L’insuffisance rénale chronique (IRC) est caractérisée par de multiples déséquilibres homéostatiques tels que la résistance à l’insuline. Peu d’études se sont intéressées aux mécanismes sous-jacents à cette résistance à l’insuline en IRC. De plus, il est méconnu si cette résistance à l’insuline peut mener au développement d’un diabète de type II chez des patients prédisposés. Dans un modèle d’IRC, le rat Sprague-Dawley (CD) néphrectomisé 5/6e, on observe une corrélation entre la gravité de l’atteinte rénale, évaluée par la créatinine sérique, et l’hyperglycémie, évaluée par la fructosamine sérique (R2 = 0.6982, p < 0.0001). Cependant, cet état hyperglycémique n’est pas observable lors d’une glycémie à jeun. Lors d’un test de tolérance au glucose, on observe une plus grande élévation de la glycémie (AUC 1.25 fois, p < 0.0001) chez le rat atteint d’IRC. Par contre, la sécrétion d’insuline au cours de ce même test n’augmente pas significativement (AUC ≈ 1.30 fois, N.S.) en comparaison aux rats témoins. Malgré une élévation des taux d’insuline en IRC suivant un bolus de glucose, les tissus périphériques ne montrent pas d’augmentation de la captation du glucose sanguin suggérant un défaut d’expression et/ou de fonction des transporteurs de glucose chez ces rats. En effet, on observe une diminution de ces transporteurs dans divers tissus impliqués dans le métabolisme du glucose tel que le foie (≈ 0.60 fois, p < 0.01) et le muscle (GLUT1 0.73 fois, p < 0.05; GLUT4 0.69 fois, p < 0.01). En conséquence, une diminution significative du transport insulinodépendant du glucose est observable dans le muscle des rats atteint d’IRC (≈ 0.63 fois, p < 0.0001). Puisque les muscles sont responsables de la majorité de la captation insulinodépendante du glucose, la diminution de l’expression du GLUT4 pourrait être associée à la résistance à l’insuline observée en IRC. La modulation de l’expression des transporteurs de glucose pourrait être à l’origine de la résistance à l’insuline en IRC. Cela dit, d’autres mécanismes peuvent aussi être impliqués. En dépit de cette importante perturbation du transport du glucose, nous n’avons pas observé de cas de diabète de type II chez le rat CD atteint d’IRC. Dans un modèle de rat atteint d’un syndrome métabolique, le rat Zucker Leprfa/fa, l’IRC provoque une forte hyperglycémie à jeun (1.5 fois, p < 0.0001). De plus, l’IRC chez le rat Zucker provoque une réponse glycémique (AUC 1.80 fois, p < 0.0001) exagérée lors d’un test de tolérance au glucose. Une forte résistance à l’insuline est mesurée au niveau des muscles puisque la dose usuelle d’insuline (2mU/mL) n’est pas suffisante pour stimuler la captation du glucose chez le rat Zucker atteint d’IRC. De plus, une modulation similaire des transporteurs de glucose peut être observée chez ces deux espèces. Par contre, environ 30% (p < 0.001) des rats Zucker atteints d’IRC avaient une glycosurie. L’IRC en soi ne mènerait donc pas au développement d’un diabète de type II. Par contre, lorsqu’une résistance à l’insuline est présente antérieurement au développement d’une IRC, cela pourrait précipiter l’apparition d’un diabète de type II chez ces patients prédisposés.

Tetraspanin 3: A central endocytic membrane component regulating the expression of ADAM10, presenilin and the amyloid precursor protein

Despite existing knowledge about the role of the A Disintegrin and Metalloproteinase 10 (ADAM10) as the α-secretase involved in the non-amyloidogenic processing of the amyloid precursor protein (APP) and Notch signalling we have only limited information about its regulation. In this study, we have identified ADAM10 interactors using a split ubiquitin yeast two hybrid approach. Tetraspanin 3 (Tspan3), which is highly expressed in the murine brain and elevated in brains of Alzheimer's disease (AD) patients, was identified and confirmed to bind ADAM10 by co-immunoprecipitation experiments in mammalian cells in complex with APP and the γ-secretase protease presenilin. Tspan3 expression increased the cell surface levels of its interacting partners and was mainly localized in early and late endosomes. In contrast to the previously described ADAM10-binding tetraspanins, Tspan3 did not affect the endoplasmic reticulum to plasma membrane transport of ADAM10. Heterologous Tspan3 expression significantly increased the appearance of carboxy-terminal cleavage products of ADAM10 and APP, whereas N-cadherin ectodomain shedding appeared unaffected. Inhibiting the endocytosis of Tspan3 by mutating a critical cytoplasmic tyrosine-based internalization motif led to increased surface expression of APP and ADAM10. After its downregulation in neuroblastoma cells and in brains of Tspan3-deficient mice, ADAM10 and APP levels appeared unaltered possibly due to a compensatory increase in the expression of Tspans 5 and 7, respectively. In conclusion, our data suggest that Tspan3 acts in concert with other tetraspanins as a stabilizing factor of active ADAM10, APP and the γ-secretase complex at the plasma membrane and within the endocytic pathway.

MicroRNA modulation of aldosterone production in the adrenal gland

Hypertension is the major risk factor for coronary disease worldwide. Primary hypertension is idiopathic in origin but is thought to arise from multiple risk factors including genetic, lifestyle and environmental influences. Secondary hypertension has a more definite aetiology; its major single cause is primary aldosteronism (PA), the greatest proportion of which is caused by aldosteroneproducing adenoma (APA), where aldosterone is synthesized at high levels by an adenoma of the adrenal gland. There is strong evidence to show that high aldosterone levels cause adverse effects on cardiovascular, cerebrovascular, renal and other systems. Extensive studies have been conducted to analyse the role that regulation of CYP11B2, the gene encoding the aldosterone synthase enzyme plays in determining aldosterone production and the development of hypertension. One significant regulatory factor that has only recently emerged is microRNA (miRNA). miRNAs are small non-coding RNAs, synthesized by a series of enzymatic processes, that negatively regulate gene expression at the posttranscriptional level. Detection and manipulation of miRNA is now known to be a viable method in the treatment, prevention and prognosis of certain diseases. The aim of the present study was to identify miRNAs likely to have a role in the regulation of corticosteroid biosynthesis. To achieve this, the miRNA profile of APA and normal human adrenal tissue was compared, as was the H295R adrenocortical cell line model of adrenocortical function, under both basal conditions and following stimulation of aldosterone production. Key differentially-expressed miRNAs were then identified and bioinformatic tools used to identify likely mRNA targets and pathways for these miRNAs, several of which were investigated and validated using in vitro methods. The background to this study is set out in Chapter 1 of this thesis, followed by a description of the major technical methods employed in Chapter 2. Chapter 3 presents the first of the study results, analysing differences in miRNA profile between APA and normal human adrenal tissue. Microarray was implemented to detect the expression of miRNAs in these two tissue types and several miRNAs were found to vary significantly and consistently between them. Furthermore, members of several miRNA clusters exhibited similar changes in expression pattern between the two tissues e.g. members of cluster miR-29b-1 (miR-29a-3p and miR-29b-3p) and of cluster miR-29b-2 (miR-29b-3p and miR-29c- 3p) are downregulated in APA, while members of cluster let-7a-1 (let-7a-5p and let-7d-5p), cluster let-7a-3 (let-7a-5p and let-7b-5p) and cluster miR-134 (miR- 134 and miR-382) are upregulated. Further bioinformatic analysis explored the possible biological function of these miRNAs using Ingenuity® Systems Pathway Analysis software. This led to the identification of validated mRNAs already known to be targeted by these miRNAs, as well as the prediction of other mRNAs that are likely targets and which are involved in processes relevant to APA pathology including cholesterol synthesis (HMGCR) and corticosteroidogenesis (CYP11B2). It was therefore hypothesised that increases in miR-125a-5p or miR- 335-5p would reduce HMGCR and CYP11B2 expression. Chapter 4 describes the characterisation of H295R cells of different strains and sources (H295R Strain 1, 2, 3 and HAC 15). Expression of CYP11B2 was assessed following application of 3 different stimulants: Angio II, dbcAMP and KCl. The most responsive strain to stimulation was Strain 1 at lower passage numbers. Furthermore, H295R proliferation increased following Angio II stimulation. In Chapter 5, the hypothesis that increases in miR-125a-5p or miR-335-5p reduces HMGCR and CYP11B2 expression was tested using realtime quantitative RT-PCR and transfection of miRNA mimics and inhibitors into the H295R cell line model of adrenocortical function. In this way, miR-125a-5p and miR-335-5p were shown to downregulate CYP11B2 and HMGCR expression, thereby validating certain of the bioinformatic predictions generated in Chapter 3. The study of miRNA profile in the H295R cell lines was conducted in Chapter 6, analysing how it changes under conditions that increase aldosterone secretion, including stimulation Angiotensin II, potassium chloride or dibutyryl cAMP (as a substitute for adrenocorticotropic hormone). miRNA profiling identified 7 miRNAs that are consistently downregulated by all three stimuli relative to basal cells: miR-106a-5p, miR-154-3p, miR-17-5p, miR-196b-5p, miR-19a-3p, miR-20b- 5p and miR-766-3p. These miRNAs include those derived from cluster miR-106a- 5p/miR-20b-5p and cluster miR-17-5p/miR-19a-3p, each producing a single polycistronic transcript. IPA bioinformatic analysis was again applied to identify experimentally validated and predicted mRNA targets of these miRNAs and the key biological pathways likely to be affected. This predicted several interactions between miRNAs derived from cluster miR-17-5p/miR-19a-3p and important mRNAs involved in cholesterol biosynthesis: LDLR and ABCA1. These predictions were investigated by in vitro experiment. miR-17-5p/miR-106a-p and miR-20b-5p were found to be consistently downregulated by stimulation of aldosterone biosynthesis. Moreover, miR-766-3p was upregulation throughout. Furthermore, I was able to validate the downregulation of LDLR by miR-17 transfection, as predicted by IPA. In summary, this study identified key miRNAs that are differentially-expressed in vivo in cases of APA or in vitro following stimulation of aldosterone biosynthesis. The many possible biological actions these miRNAs could have were filtered by bioinformatic analysis and selected interactions validated in vitro. While direct actions of these miRNAs on steroidogenic enzymes were identified, cholesterol handling also emerged as an important target and may represent a useful point of intervention in future therapies designed to modulate aldosterone biosynthesis and reduce its harmful effects.

TAZ role in lung cancer: resistance to BET inhibitors and functional interaction with lncRNA

Despite extensive research and introduction of innovative therapy, lung cancer prognosis remains poor, with a five years survival of only 17%. The success of pharmacological treatment is often impaired by drug resistance. Thus, the characterization of response mechanisms to anti-cancer compounds and of the molecular mechanisms supporting lung cancer aggressiveness are crucial for patient’s management. In the first part of this thesis, we characterized the molecular mechanism behind resistance of lung cancer cells to the Inhibitors of the Bromodomain and Extraterminal domain containing Proteins (BETi). Through a CRISPR/Cas9 screening we identified three Hippo Pathway members, LATS2, TAOK1 and NF2 as genes implicated in susceptibility to BETi. These genes confer sensitivity to BETi inhibiting TAZ activity. Conversely, TAZ overexpression increases resistance to BETi. We also displayed that BETi downregulate both YAP, TAZ and TEADs expression in several cancer cell lines, implying a novel BETi-dependent cytotoxic mechanism. In the second part of this work, we attempted to characterize the crosstalk between the TAZ gene and its cognate antisense long-non coding RNA (lncRNA) TAZ-AS202 in lung tumorigenesis. As for TAZ downregulation, TAZ-AS202 silencing impairs NSCLC cells proliferation, migration and invasion, suggesting a pro-tumorigenic function for this lncRNA during lung tumorigenesis. TAZ-AS202 regulates TAZ target genes without altering TAZ expression or localization. This finding implies an uncovered functional cooperation between TAZ and TAZ-AS202. Moreover, we found that the EPH-ephrin signaling receptor EPHB2 is a downstream effector affected by both TAZ and TAZ-AS202 silencing. EPHB2 downregulation significantly attenuates cells proliferation, migration and invasion, suggesting that, at least in part, TAZ-AS202 and TAZ pro-oncogenic activity depends on EPH-ephrin signaling final deregulation. Finally, we started to dissect the mechanism underlying the TAZ-AS202 regulatory activity on EPHB2 in lung cancer, which may involve the existence of an intermediate transcription factor and is the object of our ongoing research.

Impact of Glycosyltransferases on the Phenotype, Signaling and Transcriptome of Colorectal Cancer Cell Lines. Focus on the role of glycosyltransferases B4GALNT2 and FUT6 and their cognate Sda and sLex antigens

In colorectal cancer (CRC), two carbohydrate structures are modulated: the Sda antigen, synthesized by B4GALNT2, and sLex antigen, mainly synthesized by FUT6. sLex antigen is often overexpressed and associated with worse prognosis; B4GALNT2/Sda antigen are dramatically downregulated but their role in tumor progression and development is not fully clear. TCGA interrogation revealed a dramatic down-regulation of B4GALNT2 mRNA in CRC, compared with normal samples. Patients with higher B4GALNT2 mRNA in CRC samples displayed longer survival. Yet, methylation and miRNA expression play a relevant role in B4GALNT2 downregulation in CRC. To clarify the mechanisms linking the B4GALNT2/Sda expression level to CRC phenotype, three different CRC cell lines were modified to express B4GALNT2: LS174T cell line, in which the constitutively expressed sLex antigen was partially replaced by Sda; SW480/SW620 pair, both lacking Sda and sLex antigens. In LS174T cells, the expression of B4GALNT2 reduced the ability to grow in poor adherence conditions and the expression of ALDH, a stemness marker. In SW620 cells, B4GALNT2 expression impacted on the main aspects of malignancy. In SW480 cells the expression of B4GALNT2 left unchanged the proliferation rate and the wound healing ability. To clarify the impact of sLex on CRC phenotype, the SW480/SW620 pair were permanently transfected to express FUT6 cDNA. In both cell lines, overexpression of FUT6/sLex boosted the clonogenic ability in standard growth conditions. Conversely, the growth in soft agar and the capacity to close a wound were enhanced only in SW620 cells. Transcriptome analysis of CRC cell lines transfected either with B4GALNT2 or FUT6 showed a relevant impact of both enzymes on gene expression modulation. Overall, current data may help to personalize therapies for CRC patients according to the B4GALNT2 levels and support a causal effect of this glycosyltransferase on reducing malignancy independently of sLex inhibition.

Research of predictive biomarkers to anti-CD22 antibody-drug conjugate treatment in B-cell acute lymphoblastic leukemia

Background: The treatment of B-cell acute lymphoblastic leukemia (B-ALL) has been enriched by novel agents targeting surface markers CD19 and CD22. Inotuzumab ozogamicin (INO) is a CD22-calicheamicin conjugated monoclonal antibody approved in the setting of relapse/refractory (R/R) B-ALL able to induce a high rate of deep responses, not durable over time. Aims: This study aims to identify predictive biomarkers to INO treatment in B- ALL by flow cytometric analysis of CD22 expression and gene expression profile. Materials and methods: Firstly, the impact on patient outcome in 30 R/R B-ALL patients of baseline CD22 expression in terms of CD22 blast percentage and CD22 fluorescent intensity (CD22-FI) was explored. Secondly, baseline gene expression profile of 18 R/R B-ALL patient samples was analyzed. For statistical analysis of differentially expressed genes (DEGs) patients were divided in non-responders (NR), defined as either INO-refractory or with duration of response (DoR) < 3 months, and responders (R). Gene expression results were analyzed with Ingenuity pathway analysis (IPA). Results: In our patient set higher CD22-FI, defined as higher quartiles (Q2-Q4), correlated with better patient outcome in terms of CR rate, OS and DoR, compared to lower CD22-FI (Q1). CD22 blast percentage was less able to discriminate patients’ outcome, although a trend for better outcome in patients with CD22 ≥ 90% could be appreciated. Concerning gene expression profile, 32 genes with corrected p value <0.05 and absolute FC ≥2 were differentially expressed in NR as compared to R. IPA upstream regulator and regulator effect analysis individuated the inhibition of tumor suppressor HIPK2 as causal upstream condition of the downregulation of 6 DEGs. Conclusions: CD22-FI integrates CD22-percentage on leukemic blasts for a more comprehensive target pre-treatment evaluation. Moreover, a unique pattern of gene expression signature based on HIPK2 downregulation was identified, providing important insights in mechanisms of resistance to INO.

The role of Phospholipases as novel potential modulators of aggressiveness in Glioblastoma

Glioblastoma is the most malignant brain tumor in adults. The standard care of treatment is tumor resection, radiotherapy, and chemotherapy. Despite these invasive therapeutic approaches, glioblastoma prognosis remains unchanged. Therefore, a better understanding of the molecular mechanisms driving tumor transformation is needed to uncover novel therapeutic strategies. Several studies have shown the significance of lipid signaling and phospholipases (PLCs) in the regulation of different mechanisms in the central nervous system as well as in glioblastoma pathogenesis. This work suggests a potential role of PLCβ1 in the maintenance of a less aggressive phenotype of the tumor. Indeed, it was demonstrated that PLCβ1 gene was relatively less expressed in glioblastoma patients compared to their healthy/low-grade counterparts. Moreover, PLCβ1 silencing, in both immortalized and primary cell lines, led to increased cell migration, invasion, proliferation, cell survival and induced the upregulation of mesenchymal markers and metalloproteinases. Moreover, PLCγ1, another abundant PLC isoform in the brain, has been identified as a key element for the aggressiveness of glioblastoma. Data collected on patients’ biopsies and engineered cell models, suggested a strong correlation between PLCγ1 expression level and the acquisition of a more aggressive tumor phenotype. Finally, this trend was further probed using patient-derived glioblastoma stem cells (GSCs), which are a specific tumor population that drives aggressiveness, resistance, and recurrence in glioblastoma. GSCs analysis on the transcriptomic profiles confirmed that PLCγ1 downregulation modulated positively the activation of pathways that negatively regulate cell motility and migration and led to a decreased expression of genes involved in cancer development and progression. Taken together, these data highlight the importance of further investigating phospholipases as potential prognostic biomarkers and targets in the development of new therapeutic strategies for glioblastoma.

Decoding Agc1 deficiency: bioinformatics approaches to unveil the functional implications of Slc25a12 on the transcriptome and epigenome

In the brain, mutations in SLC25A12 gene encoding AGC1 cause an ultra-rare genetic disease reported as a developmental and epileptic encephalopathy associated with global cerebral hypomyelination. Symptoms of the disease include diffused hypomyelination, arrested psychomotor development, severe hypotonia, seizures and are common to other neurological and developmental disorders. Amongst the biological components believed to be most affected by AGC1 deficiency are oligodendrocytes, glial cells responsible for myelination. Recent studies (Poeta et al, 2022) have also shown how altered levels of transcription factors and epigenetic modifications greatly affect proliferation and differentiation in oligodendrocyte precursor cells (OPCs). In this study we explore the transcriptomic landscape of Agc1 in two different system models: OPCs silenced for Agc1 and iPSCs from human patients differentiated to neural progenitors. Analyses range from differential expression analysis, alternative splicing, master regulator analysis. ATAC-seq results on OPCs were integrated with results from RNA-Seq to assess the activity of a TF based on the accessibility data from its putative targets, which allows to integrate RNA-Seq data to infer their role as either activators or repressors. All the findings for this model were also integrated with early data from iPSCs RNA-seq results, looking for possible commonalities between the two different system models, among which we find a downregulation in genes encoding for SREBP, a transcription factor regulating fatty acids biosynthesis, a key process for myelination which could explain the hypomyelinated state of patients. We also find that in both systems cells tend to form more neurites, likely losing their ability to differentiate, considering their progenitor state. We also report several alterations in the chromatin state of cells lacking Agc1, which confirms the hypothesis for which Agc1 is not a disease restricted only to metabolic alterations in the cells, but there is a profound shift of the regulatory state of these cells.