Sulforaphane Inhibits Adhesion and Migration of Cisplatin- and Gemcitabine-Resistant Bladder Cancer Cells In Vitro.

Only 20% of patients with muscle-invasive bladder carcinoma respond to cisplatin-based chemotherapy. Since the natural phytochemical sulforaphane (SFN) exhibits antitumor properties, its influence on the adhesive and migratory properties of cisplatin- and gemcitabine-sensitive and cisplatin- and gemcitabine-resistant RT4, RT112, T24, and TCCSUP bladder cancer cells was evaluated. Mechanisms behind the SFN influence were explored by assessing levels of the integrin adhesion receptors ß1 (total and activated) and ß4 and their functional relevance. To evaluate cell differentiation processes, E- and N-cadherin, vimentin and cytokeratin (CK) 8/18 expression were examined. SFN down-regulated bladder cancer cell adhesion with cell line and resistance-specific differences. Different responses to SFN were reflected in integrin expression that depended on the cell line and presence of resistance. Chemotactic movement of RT112, T24, and TCCSUP (RT4 did not migrate) was markedly blocked by SFN in both chemo-sensitive and chemo-resistant cells. Integrin-blocking studies indicated ß1 and ß4 as chemotaxis regulators. N-cadherin was diminished by SFN, particularly in sensitive and resistant T24 and RT112 cells, whereas E-cadherin was increased in RT112 cells (not detectable in RT4 and TCCSup cells). Alterations in vimentin and CK8/18 were also apparent, though not the same in all cell lines. SFN exposure resulted in translocation of E-cadherin (RT112), N-cadherin (RT112, T24), and vimentin (T24). SFN down-regulated adhesion and migration in chemo-sensitive and chemo-resistant bladder cancer cells by acting on integrin ß1 and ß4 expression and inducing the mesenchymal-epithelial translocation of cadherins and vimentin. SFN does, therefore, possess potential to improve bladder cancer therapy.

Alcohol Promotes Lipogenesis in Sebocytes-Implications for Acne.

The oral consumption of alcohol (ethanol) has a long tradition in humans and is an integral part of many cultures. The causal relationship between ethanol consumption and numerous diseases is well known. In addition to the well-described harmful effects on the liver and pancreas, there is also evidence that ethanol abuse triggers pathological skin conditions, including acne. In the present study, we addressed this issue by investigating the effect of ethanol on the energy metabolism in human SZ95 sebocytes, with particular focus on qualitative and quantitative lipogenesis. It was found that ethanol is a strong trigger for lipogenesis, with moderate effects on cell proliferation and toxicity. We identified the non-oxidative metabolism of ethanol, which produced fatty acid ethyl esters (FAEEs), as relevant for the lipogenic effect-the oxidative metabolism of ethanol does not contribute to lipogenesis. Correspondingly, using the Seahorse extracellular flux analyzer, we found an inhibition of the mitochondrial oxygen consumption rate as a measure of mitochondrial ATP production by ethanol. The ATP production rate from glycolysis was not affected. These data corroborate that ethanol-induced lipogenesis is independent from oxygen. In sum, our results give a causal explanation for the prevalence of acne in heavy drinkers, confirming that alcoholism should be considered as a systemic disease. Moreover, the identification of key factors driving ethanol-dependent lipogenesis may also be relevant in the treatment of acne vulgaris.

Loss of Key EMT-Regulating miRNAs Highlight the Role of ZEB1 in EGFR Tyrosine Kinase Inhibitor-Resistant NSCLC.

Despite recent advances in the treatment of non-small cell lung cancer (NSCLC), acquired drug resistance to targeted therapy remains a major obstacle. Epithelial-mesenchymal transition (EMT) has been identified as a key resistance mechanism in NSCLC. Here, we investigated the mechanistic role of key EMT-regulating small non-coding microRNAs (miRNAs) in sublines of the NSCLC cell line HCC4006 adapted to afatinib, erlotinib, gefitinib, or osimertinib. The most differentially expressed miRNAs derived from extracellular vesicles were associated with EMT, and their predicted target ZEB1 was significantly overexpressed in all resistant cell lines. Transfection of a miR-205-5p mimic partially reversed EMT by inhibiting ZEB1, restoring CDH1 expression, and inhibiting migration in erlotinib-resistant cells. Gene expression of EMT-markers, transcription factors, and miRNAs were correlated during stepwise osimertinib adaptation of HCC4006 cells. Temporally relieving cells of osimertinib reversed transition trends, suggesting that the implementation of treatment pauses could provide prolonged benefits for patients. Our results provide new insights into the contribution of miRNAs to drug-resistant NSCLC harboring EGFR-activating mutations and highlight their role as potential biomarkers and therapeutic targets.

Increased MCL1 dependency leads to new applications of BH3-mimetics in drug-resistant neuroblastoma.

BACKGROUND: Neuroblastoma is a paediatric cancer that is characterised by poor prognosis for chemoresistant disease, highlighting the need for better treatment options. Here, we asked whether BH3-mimetics inhibiting BCL2 proteins may eliminate chemoresistant neuroblastoma cells. METHODS: We utilised cisplatin-adapted neuroblastoma cell lines as well as patient tissues before and after relapse to study alterations of BCL2 proteins upon chemoresistance. RESULTS: In a direct comparison of cisplatin-resistant cells we identified a prominent loss of sensitivity to BCL2/BCL-XL inhibitors that is associated with an increase in MCL1 dependency and high expression of MCL1 in patient tumour tissues. Screening of FDA-approved anti-cancer drugs in chemoresistant cells identified therapeutics that may be beneficial in combination with the clinically tested BH3-mimetic ABT263, but no synergistic drug interactions with the selective MCL1 inhibitor S63845. Further exploration of potential treatment options for chemoresistant neuroblastoma identified immunotherapy based on NK cells as highly promising, since NK cells are able to efficiently kill both parental and chemoresistant cells. CONCLUSIONS: These data highlight that the application of BH3-mimetics may differ between first line treatment and relapsed disease. Combination of NK cell-based immunotherapy with BH3-mimetics may further increase killing of chemoresistant neuroblastoma, outlining a new treatment strategy for relapsed neuroblastoma.

Elevated Expression of LGR5 and WNT Signaling Factors in Neuroblastoma Cells With Acquired Drug Resistance.

Neuroblastoma (NB) is a pediatric solid cancer with high fatality, relapses, and acquired resistance to chemotherapy, that requires new therapeutic approaches to improve survival. LGR5 is a receptor that potentiates WNT/signaling pathway and has been reported to promote development and survival in several adult cancers. In this study we investigated LGR5 expression in a panel of NB cell lines with acquired resistance to vincristine or doxorubicin. We show LGR5-LRP6 cooperation with enhanced expression in drug resistant NB cell lines compared to parental cells, suggesting a role for LGR5 in the emergence of drug resistance, warranting further investigation.

ERBB and P-glycoprotein inhibitors break resistance in relapsed neuroblastoma models through P-glycoprotein.

Chemotherapy resistance is a persistent clinical problem in relapsed high-risk neuroblastomas. We tested a panel of 15 drugs for sensitization of neuroblastoma cells to the conventional chemotherapeutic vincristine, identifying tariquidar, an inhibitor of the transmembrane pump P-glycoprotein (P-gp/ABCB1), and the ERBB family inhibitor afatinib as the top resistance breakers. Both compounds were efficient in sensitizing neuroblastoma cells to vincristine in trypan blue exclusion assays and in inducing apoptotic cell death. The evaluation of ERBB signaling revealed no functional inhibition, that is, dephosphorylation of the downstream pathways upon afatinib treatment but direct off-target interference with P-gp function. Depletion of ABCB1, but not ERRB4, sensitized cells to vincristine treatment. P-gp inhibition substantially broke vincristine resistance in vitro and in vivo (zebrafish embryo xenograft). The analysis of gene expression datasets of more than 50 different neuroblastoma cell lines (primary and relapsed) and more than 160 neuroblastoma patient samples from the pediatric precision medicine platform INFORM (Individualized Therapy For Relapsed Malignancies in Childhood) confirmed a pivotal role of P-gp specifically in neuroblastoma resistance at relapse, while the ERBB family appears to play a minor part.

Increased HRD score in cisplatin resistant penile cancer cells.

BACKGROUND/INTRODUCTION: Penile cancer is a rare disease in demand for new therapeutic options. Frequently used combination chemotherapy with 5 fluorouracil (5-FU) and cisplatin (CDDP) in patients with metastatic penile cancer mostly results in the development of acquired drug resistance. Availability of cell culture models with acquired resistance against standard therapy could help to understand molecular mechanisms underlying chemotherapy resistance and to identify candidate treatments for an efficient second line therapy. METHODS: We generated a cell line from a humanpapilloma virus (HPV) negative penile squamous cell carcinoma (UKF-PEC-1). This cell line was subject to chronic exposure to chemotherapy with CDDP and / or 5-FU to induce acquired resistance in the newly established chemo-resistant sublines (PEC-1rCDDP2500, adapted to 2500 ng/ml CDDP; UKF-PEC-1r5-FU500, adapted to 500 ng/ml 5- FU; UKF-PEC1rCDDP2500/r5-FU500, adapted to 2500 ng/ml CDDP and 500 ng/ml 5 -FU). Afterwards cell line pellets were formalin-fixed, paraffin embedded and subject to sequencing as well as testing for homologous recombination deficiency (HRD). Additionally, exemplary immunohistochemical stainings for p53 and gammaH2AX were applied for verification purposes. Finally, UKF-PEC-1rCDDP2500, UKF-PEC-1r5-FU500, UKF-PEC1rCDDP2500/r5-FU500, and UKF-PEC-3 (an alternative penis cancer cell line) were tested for sensitivity to paclitaxel, docetaxel, olaparib, and rucaparib. RESULTS AND CONCLUSIONS: The chemo-resistant sublines differed in their mutational landscapes. UKF-PEC-1rCDDP2500 was characterized by an increased HRD score, which is supposed to be associated with increased PARP inhibitor and immune checkpoint inhibitor sensitivity in cancer. However, UKF-PEC-1rCDDP2500 did not display sensitivity to PARP inhibitors.

Plant-Derived Sulforaphane Suppresses Growth and Proliferation of Drug-Sensitive and Drug-Resistant Bladder Cancer Cell Lines In Vitro.

Combined cisplatin-gemcitabine (GC) application is standard for treating muscle-invasive bladder cancer. However, since rapid resistance to treatment often develops, many patients turn to supplements in the form of plant-based compounds. Sulforaphane (SFN), derived from cruciferous vegetables, is one such compound, and the present study was designed to investigate its influence on growth and proliferation in a panel of drug-sensitive bladder cancer cell lines, as well as their gemcitabine- and cisplatin-resistant counterparts. Chemo-sensitive and -resistant RT4, RT112, T24, and TCCSUP cell lines were exposed to SFN in different concentrations, and tumor growth, proliferation, and clone formation were evaluated, in addition to apoptosis and cell cycle progression. Means of action were investigated by assaying cell-cycle-regulating proteins and the mechanistic target of rapamycin (mTOR)/AKT signaling cascade. SFN significantly inhibited growth, proliferation, and clone formation in all four tumor cell lines. Cells were arrested in the G2/M and/or S phase, and alteration of the CDK-cyclin axis was closely associated with cell growth inhibition. The AKT/mTOR signaling pathway was deactivated in three of the cell lines. Acetylation of histone H3 was up-regulated. SFN, therefore, does exert tumor-suppressive properties in cisplatin- and gemcitabine-resistant bladder cancer cells and could be beneficial in optimizing bladder cancer therapy.

Functional Downregulation of PD-L1 and PD-L2 by CpG and non-CpG Oligonucleotides in Melanoma Cells.

The clinical application of immune checkpoint inhibitors represents a breakthrough progress in the treatment of metastasized melanoma and other tumor entities. In the present study, it was hypothesized that oligonucleotides (ODNs), known as modulators of the immune response, have an impact on the endogenous expression of checkpoint molecules, namely PD-L1 and PD-L2 (PD-L1/2). IFNγ-stimulated melanoma cells (A375, SK-Mel-28) were treated with different synthetically manufactured oligonucleotides which differed in sequence, length and backbone composition. It was found that a variety of different ODN sequences significantly suppressed PD-L1/2 expression. This effect was dependent on length and phosphorothioate (PTO) backbone. In particular, a sequence containing solely guanines (nCpG-6-PTO) was highly effective in downregulating PD-L1/2 at the protein, mRNA and promoter levels. Mechanistically, we gave evidence that ODNs with G-quartet-forming motifs suppress the interferon signaling axis (JAK/STAT/IRF1). Our findings identify a subset of ODNs as interesting pharmacological compounds that could expand the arsenal of targeted therapies to combat the immunological escape of tumor cells.

Allyl-, Butyl- and Phenylethyl-Isothiocyanate Modulate Akt-mTOR and Cyclin-CDK Signaling in Gemcitabine- and Cisplatin-Resistant Bladder Cancer Cell Lines.

Combined cisplatin-gemcitabine treatment causes rapid resistance development in patients with advanced urothelial carcinoma. The present study investigated the potential of the natural isothiocyanates (ITCs) allyl-isothiocyanate (AITC), butyl-isothiocyanate (BITC), and phenylethyl-isothiocyanate (PEITC) to suppress growth and proliferation of gemcitabine- and cisplatin-resistant bladder cancer cells lines. Sensitive and gemcitabine- and cisplatin-resistant RT112, T24, and TCCSUP cells were treated with the ITCs, and tumor cell growth, proliferation, and clone formation were evaluated. Apoptosis induction and cell cycle progression were investigated as well. The molecular mode of action was investigated by evaluating cell cycle-regulating proteins (cyclin-dependent kinases (CDKs) and cyclins A and B) and the mechanistic target of the rapamycin (mTOR)-AKT signaling pathway. The ITCs significantly inhibited growth, proliferation and clone formation of all tumor cell lines (sensitive and resistant). Cells were arrested in the G2/M phase, independent of the type of resistance. Alterations of both the CDK-cyclin axis and the Akt-mTOR signaling pathway were observed in AITC-treated T24 cells with minor effects on apoptosis induction. In contrast, AITC de-activated Akt-mTOR signaling and induced apoptosis in RT112 cells, with only minor effects on CDK expression. It is concluded that AITC, BITC, and PEITC exert tumor-suppressive properties on cisplatin- and gemcitabine-resistant bladder cancer cells, whereby the molecular action may differ among the cell lines. The integration of these ITCs into the gemcitabine-/cisplatin-based treatment regimen might optimize bladder cancer therapy.

In Vitro Safety, Off-Target and Bioavailability Profile of the Antiviral Compound Silvestrol.

We characterized the in vitro safety and bioavailability profile of silvestrol, a compound effective against various viruses, such as corona- and Ebolaviruses, with an EC50 value of about 5 nM. The cytotoxic profile of silvestrol was assessed in various cancer cell lines, as well as the mutagenic and genotoxic potential with Ames and micronuclei tests, respectively. To identify off-target effects, we investigated whether silvestrol modulates G-protein coupled receptor (GPCR) signaling pathways. To predict the bioavailability of silvestrol, its stability, permeability and cellular uptake were determined. Silvestrol reduced viability in a cell-type-dependent manner, mediated no off-target effects via GPCRs, had no mutagenic potential and minor genotoxic effects at 50 nM. Silvestrol did not disturb cell barrier integrity, showed low membrane permeability, was stable in liver microsomes and exhibited good cellular uptake. Efficient cellular uptake and increased cytotoxicity were observed in cell lines with a low expression level of the transport protein P-glycoprotein, the known efflux transporter of silvestrol. In conclusion, silvestrol showed low permeability but good cellular uptake and high stability. Cell-type-dependent cytotoxicity seems to be caused by the accumulation of silvestrol in cells lacking the ability to expel silvestrol due to low P-glycoprotein levels.

USP22 controls type III interferon signaling and SARS-CoV-2 infection through activation of STING.

Pattern recognition receptors (PRRs) and interferons (IFNs) serve as essential antiviral defense against SARS-CoV-2, the causative agent of the COVID-19 pandemic. Type III IFNs (IFN-λ) exhibit cell-type specific and long-lasting functions in auto-inflammation, tumorigenesis, and antiviral defense. Here, we identify the deubiquitinating enzyme USP22 as central regulator of basal IFN-λ secretion and SARS-CoV-2 infections in human intestinal epithelial cells (hIECs). USP22-deficient hIECs strongly upregulate genes involved in IFN signaling and viral defense, including numerous IFN-stimulated genes (ISGs), with increased secretion of IFN-λ and enhanced STAT1 signaling, even in the absence of exogenous IFNs or viral infection. Interestingly, USP22 controls basal and 2'3'-cGAMP-induced STING activation and loss of STING reversed STAT activation and ISG and IFN-λ expression. Intriguingly, USP22-deficient hIECs are protected against SARS-CoV-2 infection, viral replication, and the formation of de novo infectious particles, in a STING-dependent manner. These findings reveal USP22 as central host regulator of STING and type III IFN signaling, with important implications for SARS-CoV-2 infection and antiviral defense.

Amygdalin Exerts Antitumor Activity in Taxane-Resistant Prostate Cancer Cells.

Despite recent advances in the treatment of metastatic prostate cancer (PCa), resistance development after taxane treatments is inevitable, necessitating effective options to combat drug resistance. Previous studies indicated antitumoral properties of the natural compound amygdalin. However, whether amygdalin acts on drug-resistant tumor cells remains questionable. An in vitro study was performed to investigate the influence of amygdalin (10 mg/mL) on the growth of a panel of therapy-naïve and docetaxel- or cabazitaxel-resistant PCa cell lines (PC3, DU145, and LNCaP cells). Tumor growth, proliferation, clonal growth, and cell cycle progression were investigated. The cell cycle regulating proteins (phospho)cdk1, (phospho)cdk2, cyclin A, cyclin B, p21, and p27 and the mammalian target of rapamycin (mTOR) pathway proteins (phospho)Akt, (phospho)Raptor, and (phospho)Rictor as well as integrin ß1 and the cytoskeletal proteins vimentin, ezrin, talin, and cytokeratin 8/18 were assessed. Furthermore, chemotactic activity and adhesion to extracellular matrix components were analyzed. Amygdalin dose-dependently inhibited tumor growth and reduced tumor clones in all (parental and resistant) PCa cell lines, accompanied by a G0/G1 phase accumulation. Cell cycle regulating proteins were significantly altered by amygdalin. A moderate influence of amygdalin on tumor cell adhesion and chemotaxis was observed as well, paralleled by modifications of cytoskeletal proteins and the integrin ß1 expression level. Amygdalin may, therefore, block tumor growth and disseminative characteristics of taxane-resistant PCa cells. Further studies are warranted to determine amygdalin's value as an antitumor drug.

Value of c-MET and Associated Signaling Elements for Predicting Outcomes and Targeted Therapy in Penile Cancer.

Whereas the lack of biomarkers in penile cancer (PeCa) impedes the development of efficacious treatment protocols, preliminary evidence suggests that c-MET and associated signaling elements may be dysregulated in this disorder. In the following study, we investigated whether c-MET and associated key molecular elements may have prognostic and therapeutic utility in PeCa. Formalin-fixed, paraffin-embedded tumor tissue from therapy-naïve patients with invasive PeCa was used for tissue microarray (TMA) analysis. Immunohistochemical staining was performed to determine the expression of the proteins c-MET, PPARg, ß-catenin, snail, survivin, and n-MYC. In total, 94 PeCa patients with available tumor tissue were included. The median age was 64.9 years. High-grade tumors were present in 23.4%, and high-risk HPV was detected in 25.5%. The median follow-up was 32.5 months. High expression of snail was associated with HPV-positive tumors. Expression of ß-catenin was inversely associated with grading. In both univariate COX regression analysis and the log-rank test, an increased expression of PPARg and c-MET was predictive of inferior disease-specific survival (DSS). Moreover, in multivariate analysis, a higher expression of c-MET was independently associated with worse DSS. Blocking c-MET with cabozantinib and tivantinib induced a significant decrease in viability in the primary PeCa cell line UKF-PeC3 isolated from the tumor tissue as well as in cisplatin- and osimertinib-resistant sublines. Strikingly, a higher sensitivity to tivantinib could be detected in the latter, pointing to the promising option of utilizing this agent in the second-line treatment setting.

Artesunate Inhibits the Growth Behavior of Docetaxel-Resistant Prostate Cancer Cells.

Novel therapeutic strategies are urgently needed for advanced metastatic prostate cancer (PCa). Phytochemicals used in Traditional Chinese Medicine seem to exhibit tumor suppressive properties. Therefore, the therapeutic potential of artesunate (ART) on the progressive growth of therapy-sensitive (parental) and docetaxel (DX)-resistant PCa cells was investigated. Parental and DX-resistant PCa cell lines DU145, PC3, and LNCaP were incubated with artesunate (ART) [1-100 µM]. ART-untreated and 'non-cancerous' cells served as controls. Cell growth, proliferation, cell cycle progression, cell death and the expression of involved proteins were evaluated. ART, dose- and time-dependently, significantly restricted cell growth and proliferation of parental and DX-resistant PCa cells, but not of 'normal, non-cancerous' cells. ART-induced growth and proliferation inhibition was accompanied by G0/G1 phase arrest and down-regulation of cell cycle activating proteins in all DX-resistant PCa cells and parental LNCaP. In the parental and DX-resistant PC3 and LNCaP cell lines, ART also promoted apoptotic cell death. Ferroptosis was exclusively induced by ART in parental and DX-resistant DU145 cells by increasing reactive oxygen species (ROS). The anti-cancer activity displayed by ART took effect in all three PCa cell lines, but through different mechanisms of action. Thus, in advanced PCa, ART may hold promise as a complementary treatment together with conventional therapy.

The routine use of LCD-Array hybridisation technique for HPV subtyping in the diagnosis of penile carcinoma compared to other methods.

BACKGROUND: Routine human papillomavirus (HPV) testing is performed in cervival cancer and is required for classification of some head and neck cancers. In penile cancer a statement on HPV association of the carcinoma is required. In most cases p16 immunohistochemistry as a surrogate marker is applied in this setting. Since differing clinical outcomes for HPV positive and HPV negative tumors are described we await HPV testing to be requested more frequently by clinicians, also in the context of HPV vaccination, where other HPV subtypes are expected to emerge. METHOD: Therefore, a cohort of archived, formalin-fixed paraffin embedded (FFPE) penile neoplasias was stained for p16 and thereafter tested for HPV infection status via PCR based methods. Additionally to Sanger sequencing, we chose LCD-Array technique (HPV 3.5 LCD-Array Kit, Chipron; LCD-Array) for the detection of HPV in our probes expecting a less time consuming and sensitive HPV test for our probes. RESULTS: We found that LCD-Array is a sensitive and feasible method for HPV testing in routine diagnostics applicable to FFPE material in our cohort. Our cohort of penile carcinomas and carcinomas in situ was associated with HPV infection in 61% of cases. We detected no significant association between HPV infection status and histomorphological tumor characteristics as well as overall survival. CONCLUSIONS: We showed usability of molecular HPV testing on a cohort of archived penile carcinomas. To the best of our knowledge, this is the first study investigating LCD-Array technique on a cohort of penile neoplasias.

CETSA interaction proteomics define specific RNA-modification pathways as key components of fluorouracil-based cancer drug cytotoxicity.

The optimal use of many cancer drugs is hampered by a lack of detailed understanding of their mechanism of action (MoA). Here, we apply a high-resolution implementation of the proteome-wide cellular thermal shift assay (CETSA) to follow protein interaction changes induced by the antimetabolite 5-fluorouracil (5-FU) and related nucleosides. We confirm anticipated effects on the known main target, thymidylate synthase (TYMS), and enzymes in pyrimidine metabolism and DNA damage pathways. However, most interaction changes we see are for proteins previously not associated with the MoA of 5-FU, including wide-ranging effects on RNA-modification and -processing pathways. Attenuated responses of specific proteins in a resistant cell model identify key components of the 5-FU MoA, where intriguingly the abrogation of TYMS inhibition is not required for cell proliferation.

Differences between intrinsic and acquired nucleoside analogue resistance in acute myeloid leukaemia cells.

BACKGROUND: SAMHD1 mediates resistance to anti-cancer nucleoside analogues, including cytarabine, decitabine, and nelarabine that are commonly used for the treatment of leukaemia, through cleavage of their triphosphorylated forms. Hence, SAMHD1 inhibitors are promising candidates for the sensitisation of leukaemia cells to nucleoside analogue-based therapy. Here, we investigated the effects of the cytosine analogue CNDAC, which has been proposed to be a SAMHD1 inhibitor, in the context of SAMHD1. METHODS: CNDAC was tested in 13 acute myeloid leukaemia (AML) cell lines, in 26 acute lymphoblastic leukaemia (ALL) cell lines, ten AML sublines adapted to various antileukaemic drugs, 24 single cell-derived clonal AML sublines, and primary leukaemic blasts from 24 AML patients. Moreover, 24 CNDAC-resistant sublines of the AML cell lines HL-60 and PL-21 were established. The SAMHD1 gene was disrupted using CRISPR/Cas9 and SAMHD1 depleted using RNAi, and the viral Vpx protein. Forced DCK expression was achieved by lentiviral transduction. SAMHD1 promoter methylation was determined by PCR after treatment of genomic DNA with the methylation-sensitive HpaII endonuclease. Nucleoside (analogue) triphosphate levels were determined by LC-MS/MS. CNDAC interaction with SAMHD1 was analysed by an enzymatic assay and by crystallisation. RESULTS: Although the cytosine analogue CNDAC was anticipated to inhibit SAMHD1, SAMHD1 mediated intrinsic CNDAC resistance in leukaemia cells. Accordingly, SAMHD1 depletion increased CNDAC triphosphate (CNDAC-TP) levels and CNDAC toxicity. Enzymatic assays and crystallisation studies confirmed CNDAC-TP to be a SAMHD1 substrate. In 24 CNDAC-adapted acute myeloid leukaemia (AML) sublines, resistance was driven by DCK (catalyses initial nucleoside phosphorylation) loss. CNDAC-adapted sublines displayed cross-resistance only to other DCK substrates (e.g. cytarabine, decitabine). Cell lines adapted to drugs not affected by DCK or SAMHD1 remained CNDAC sensitive. In cytarabine-adapted AML cells, increased SAMHD1 and reduced DCK levels contributed to cytarabine and CNDAC resistance. CONCLUSION: Intrinsic and acquired resistance to CNDAC and related nucleoside analogues are driven by different mechanisms. The lack of cross-resistance between SAMHD1/ DCK substrates and non-substrates provides scope for next-line therapies after treatment failure.

A Potential Role of the CD47/SIRPalpha Axis in COVID-19 Pathogenesis.

The coronavirus SARS-CoV-2 is the cause of the ongoing COVID-19 pandemic. Most SARS-CoV-2 infections are mild or even asymptomatic. However, a small fraction of infected individuals develops severe, life-threatening disease, which is caused by an uncontrolled immune response resulting in hyperinflammation. However, the factors predisposing individuals to severe disease remain poorly understood. Here, we show that levels of CD47, which is known to mediate immune escape in cancer and virus-infected cells, are elevated in SARS-CoV-2-infected Caco-2 cells, Calu-3 cells, and air-liquid interface cultures of primary human bronchial epithelial cells. Moreover, SARS-CoV-2 infection increases SIRPalpha levels, the binding partner of CD47, on primary human monocytes. Systematic literature searches further indicated that known risk factors such as older age and diabetes are associated with increased CD47 levels. High CD47 levels contribute to vascular disease, vasoconstriction, and hypertension, conditions that may predispose SARS-CoV-2-infected individuals to COVID-19-related complications such as pulmonary hypertension, lung fibrosis, myocardial injury, stroke, and acute kidney injury. Hence, age-related and virus-induced CD47 expression is a candidate mechanism potentially contributing to severe COVID-19, as well as a therapeutic target, which may be addressed by antibodies and small molecules. Further research will be needed to investigate the potential involvement of CD47 and SIRPalpha in COVID-19 pathology. Our data should encourage other research groups to consider the potential relevance of the CD47/ SIRPalpha axis in their COVID-19 research.

Genome-scale integration of transcriptome and metabolome unveils squalene synthase and dihydrofolate reductase as targets against AML cells resistant to chemotherapy.

The development of resistance to chemotherapeutic agents, such as Doxorubicin (DOX) and cytarabine (AraC), is one of the greatest challenges to the successful treatment of Acute Myeloid Leukemia (AML). Such acquisition is often underlined by a metabolic reprogramming that can provide a therapeutic opportunity, as it can lead to the emergence of vulnerabilities and dependencies to be exploited as targets against the resistant cells. In this regard, genome-scale metabolic models (GSMMs) have emerged as powerful tools to integrate multiple layers of data to build cancer-specific models and identify putative metabolic vulnerabilities. Here, we use genome-scale metabolic modelling to reconstruct a GSMM of the THP1 AML cell line and two derivative cell lines, one with acquired resistance to AraC and the second with acquired resistance to DOX. We also explore how, adding to the transcriptomic layer, the metabolomic layer enhances the selectivity of the resulting condition specific reconstructions. The resulting models enabled us to identify and experimentally validate that drug-resistant THP1 cells are sensitive to the FDA-approved antifolate methotrexate. Moreover, we discovered and validated that the resistant cell lines could be selectively targeted by inhibiting squalene synthase, providing a new and promising strategy to directly inhibit cholesterol synthesis in AML drug resistant cells.