Utilizing non-coding RNA-mediated regulation of ATP binding cassette (ABC) transporters to overcome multidrug resistance to cancer chemotherapy.

Multidrug resistance (MDR) is one of the primary factors that produces treatment failure in patients receiving cancer chemotherapy. MDR is a complex multifactorial phenomenon, characterized by a decrease or abrogation of the efficacy of a wide spectrum of anticancer drugs that are structurally and mechanistically distinct. The overexpression of the ATP-binding cassette (ABC) transporters, notably ABCG2 and ABCB1, are one of the primary mediators of MDR in cancer cells, which promotes the efflux of certain chemotherapeutic drugs from cancer cells, thereby decreasing or abolishing their therapeutic efficacy. A number of studies have suggested that non-coding RNAs (ncRNAs), particularly microRNAs (miRNAs), long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs), play a pivotal role in mediating the upregulation of ABC transporters in certain MDR cancer cells. This review will provide updated information about the induction of ABC transporters due to the aberrant regulation of ncRNAs in cancer cells. We will also discuss the measurement and biological profile of circulating ncRNAs in various body fluids as potential biomarkers for predicting the response of cancer patients to chemotherapy. Sequence variations, such as alternative polyadenylation of mRNA and single nucleotide polymorphism (SNPs) at miRNA target sites, which may indicate the interaction of miRNA-mediated gene regulation with genetic variations to modulate the MDR phenotype, will be reviewed. Finally, we will highlight novel strategies that could be used to modulate ncRNAs and circumvent ABC transporter-mediated MDR.

CD39/CD73/A2AR pathway and cancer immunotherapy.

Cancer development is closely associated with immunosuppressive tumor microenvironment (TME) that attenuates antitumor immune responses and promotes tumor cell immunologic escape. The sequential conversion of extracellular ATP into adenosine by two important cell-surface ectonucleosidases CD39 and CD73 play critical roles in reshaping an immunosuppressive TME. The accumulated extracellular adenosine mediates its regulatory functions by binding to one of four adenosine receptors (A1R, A2AR, A2BR and A3R). The A2AR elicits its profound immunosuppressive function via regulating cAMP signaling. The increasing evidence suggests that CD39, CD73 and A2AR could be used as novel therapeutic targets for manipulating the antitumor immunity. In recent years, monoclonal antibodies or small molecule inhibitors targeting the CD39/CD73/A2AR pathway have been investigated in clinical trials as single agents or in combination with anti-PD-1/PD-L1 therapies. In this review, we provide an updated summary about the pathophysiological function of the adenosinergic pathway in cancer development, metastasis and drug resistance. The targeting of one or more components of the adenosinergic pathway for cancer therapy and circumvention of immunotherapy resistance are also discussed. Emerging biomarkers that may be used to guide the selection of CD39/CD73/A2AR-targeting treatment strategies for individual cancer patients is also deliberated.

BET Bromodomain Inhibitors: Novel Design Strategies and Therapeutic Applications.

The mammalian bromodomain and extra-terminal domain (BET) family of proteins consists of four conserved members (Brd2, Brd3, Brd4, and Brdt) that regulate numerous cancer-related and immunity-associated genes. They are epigenetic readers of histone acetylation with broad specificity. BET proteins are linked to cancer progression due to their interaction with numerous cellular proteins including chromatin-modifying factors, transcription factors, and histone modification enzymes. The spectacular growth in the clinical development of small-molecule BET inhibitors underscores the interest and importance of this protein family as an anticancer target. Current approaches targeting BET proteins for cancer therapy rely on acetylation mimics to block the bromodomains from binding chromatin. However, bromodomain-targeted agents are suffering from dose-limiting toxicities because of their effects on other bromodomain-containing proteins. In this review, we provided an updated summary about the evolution of small-molecule BET inhibitors. The design of bivalent BET inhibitors, kinase and BET dual inhibitors, BET protein proteolysis-targeting chimeras (PROTACs), and Brd4-selective inhibitors are discussed. The novel strategy of targeting the unique C-terminal extra-terminal (ET) domain of BET proteins and its therapeutic significance will also be highlighted. Apart from single agent treatment alone, BET inhibitors have also been combined with other chemotherapeutic modalities for cancer treatment demonstrating favorable clinical outcomes. The investigation of specific biomarkers for predicting the efficacy and resistance of BET inhibitors is needed to fully realize their therapeutic potential in the clinical setting.

The prospects of tumor chemosensitivity testing at the single-cell level.

Tumor chemosensitivity testing plays a pivotal role in the optimal selection of chemotherapeutic regimens for cancer patients in a personalized manner. High-throughput drug screening approaches have been developed but they failed to take into account intratumor heterogeneity and therefore only provided limited predictive power of therapeutic response to individual cancer patients. Single cancer cell drug sensitivity testing (SCC-DST) has been recently developed to evaluate the variable sensitivity of single cells to different anti-tumor drugs. In this review, we discuss how SCC-DST overcomes the obstacles of traditional drug screening methodologies. We outline critical procedures of SCC-DST responsible for single-cell generation and sorting, cell-drug encapsulation on a microfluidic chip and detection of cell-drug interactions. In SCC-DST, droplet-based microfluidics is emerging as an important platform that integrated various assays and analyses for drug susceptibility tests for individual patients. With the advancement of technology, both fluorescence imaging and label-free analysis have been used for detecting single cell-drug interactions. We also discuss the feasibility of integrating SCC-DST with single-cell RNA sequencing to unravel the mechanisms leading to drug resistance, and utilizing artificial intelligence to facilitate the analysis of various omics data in the evaluation of drug susceptibility. SCC-DST is setting the stage for better drug selection for individual cancer patients in the era of precision medicine.

Intercellular transfer of exosomal wild type EGFR triggers osimertinib resistance in non-small cell lung cancer.

BACKGROUND: Epidermal growth factor receptor (EGFR)-mutated lung cancer constitutes a major subgroup of non-small cell lung cancer (NSCLC) and osimertinib is administrated as first-line treatment. However, most patients with osimertinib treatment eventually relapse within one year. The underlying mechanisms of osimertinib resistance remain largely unexplored. METHODS: Exosomes isolation was performed by differential centrifugation. Co-culture assays were conducted to explore the alteration of drug sensitivity by cell viability and apoptosis assays. Immunofluorescence and flow cytometry were performed to visualize the formation or absorption of exosomes. Exosomes secretion was measured by Nanoparticle Tracking Analysis or ELISA. The xenograft tumor model in mice was established to evaluate the effect of exosomes on osimertinib sensitivity in vivo. RESULTS: Intercellular transfer of exosomal wild type EGFR protein confers osimertinib resistance to EGFR-mutated sensitive cancer cells in vitro and in vivo. Co-culture of EGFR-mutated sensitive cells and EGFR-nonmutated resistant cells promoted osimertinib resistance phenotype in EGFR-mutated cancer cells, while depletion of exosomes from conditioned medium or blockade of exosomal EGFR by neutralizing antibody alleviated this phenotype. Mechanistically, osimertinib promoted the release of exosomes by upregulated a Rab GTPase (RAB17). Knockdown of RAB17 resulted in the decrease of exosomes secretion. Moreover, exosomes could be internalized by EGFR-mutated cancer cells via Clathrin-dependent endocytosis and then the encapsulated exosomal wild type EGFR protein activated downstream PI3K/AKT and MAPK signaling pathways and triggered osimertinib resistance. CONCLUSIONS: Intercellular transfer of exosomal wild type EGFR promotes osimertinib resistance in NSCLC, which may represent a novel resistant mechanism of osimertinib and provide a proof of concept for targeting exosomes to prevent and reverse the osimertinib resistance.

Drug repurposing to overcome resistance to various therapies for colorectal cancer.

Emergence of novel treatment modalities provides effective therapeutic options, apart from conventional cytotoxic chemotherapy, to fight against colorectal cancer. Unfortunately, drug resistance remains a huge challenge in clinics, leading to invariable occurrence of disease progression after treatment initiation. While novel drug development is unfavorable in terms of time frame and costs, drug repurposing is one of the promising strategies to combat resistance. This approach refers to the application of clinically available drugs to treat a different disease. With the well-established safety profile and optimal dosing of these approved drugs, their combination with current cancer therapy is suggested to provide an economical, safe and efficacious approach to overcome drug resistance and prolong patient survival. Here, we review both preclinical and clinical efficacy, as well as cellular mechanisms, of some extensively studied repurposed drugs, including non-steroidal anti-inflammatory drugs, statins, metformin, chloroquine, disulfiram, niclosamide, zoledronic acid and angiotensin receptor blockers. The three major treatment modalities in the management of colorectal cancer, namely classical cytotoxic chemotherapy, molecular targeted therapy and immunotherapy, are covered in this review.

CUDC-907, a dual HDAC and PI3K inhibitor, reverses platinum drug resistance.

Platinum (Pt)-based anticancer drugs are the mainstay of treatment for solid cancers. However, resistance to Pt drugs develops rapidly, which can be caused by overexpression of multidrug resistance transporters and activation of DNA repair. CUDC-907 is a potent molecular targeted anticancer agent, rationally designed to simultaneously inhibit histone deacetylase (HDAC) and phosphatidylinositol 3-kinase (PI3K). We investigated the potentiation effect of CUDC-907 on Pt drugs in resistant cancer cells. ABCC2 stably-transfected HEK293 cells and two pairs of parental and Pt-resistant cancer cell lines were used to test for the circumvention of resistance by CUDC-907. Chemosensitivity was assessed by the sulphorhodamine B assay. Drug combinations were evaluated by the median effect analysis. ABCC2 transport activity was examined by flow cytometric assay. Cellular Pt drug accumulation and DNA platination were detected by inductively coupled plasma optical emission spectroscopy. ABCC2, ERCC1 and p21 expression were evaluated by quantitative real-time PCR. Cell cycle analysis and apoptosis assay were performed by standard flow cytometric method. The combination of CUDC-907 with cisplatin were found to exhibit synergistic cytotoxic effect in cisplatin-resistant cancer cells. In Pt-resistant cancer cells, CUDC-907 apparently circumvented the resistance through inhibition of ABCC2 and DNA repair but induction of cell cycle arrest. In the presence of CUDC-907, cellular accumulation of Pt drugs and formation of DNA-Pt adducts were found to be increased whereas expression levels of ABCC2 and ERCC1 was inhibited in Pt-resistant cells. The data advocates further development of CUDC-907 as a resistance reversal agent for use in combination cancer chemotherapy.

A novel miR-203-DNMT3b-ABCG2 regulatory pathway predisposing colorectal cancer development.

Colorectal cancer (CRC) is a major cause of mortality and morbidity worldwide. The majority of studies to date focused on genetic mutations and epigenetic changes that drive the CRC carcinogenesis process. Xenobiotic transporters play an important role in safeguarding our body from external toxic substances. These transporters lining the gastrointestinal tract protect us from dietary carcinogens. This study aimed to investigate the downregulation of an efflux transporter ABCG2 in CRC versus normal colon mucosa, so as to shed light on its relevance to CRC initiation and progression. We found that ABCG2 expression is at least 50-fold lower in adenomatous polyps and colon carcinoma specimens obtained from CRC patients than in their matched pair of adjacent normal colon mucosa. The underlying mechanism(s) for ABCG2 under-expression in CRC is currently not known. To this end, aberrant promoter methylation of ABCG2 has been reported to cause its repression in a few cancer types including renal carcinoma and multiple myeloma. In this study, miR-203 was found to be downregulated in all polyps and CRC specimens, relative to adjacent normal colon mucosa. We demonstrated that the de novo DNA methyltransferase DNMT3b is a direct target of miR-203. Importantly, by relieving the repression on DNMT3b, the lower expression of miR-203 in CRC caused ABCG2 promoter methylation and remarkable lower ABCG2 expression in colon cancer cell lines and the patient CRC specimens. The restoration of ABCG2 function via modulating this new microRNA-methylation mechanism in precancerous cells may represent an attractive strategy to delay the carcinogenesis process. © 2016 Wiley Periodicals, Inc.

Telmisartan increases systemic exposure to rosuvastatin after single and multiple doses, and in vitro studies show telmisartan inhibits ABCG2-mediated transport of rosuvastatin.

PURPOSE: The ATP-binding cassette transporter G2 (ABCG2) plays an important role in the disposition of rosuvastatin. Telmisartan, a selective angiotension-II type 1 (AT1) receptor blocker, inhibits the transport capacity of ABCG2, which may result in drug interactions. This study investigated the pharmacokinetic interaction between rosuvastatin and telmisartan and the potential mechanism. METHODS: In this two-phase fixed-order design study, healthy subjects received single doses of 10 mg rosuvastatin at baseline and after telmisartan 40 mg daily for 14 days. Patients with hyperlipidaemia who had been taking rosuvastatin 10 mg daily for at least 4 weeks were given telmisartan 40 mg daily for 14 days together with rosuvastatin. Plasma concentrations of rosuvastatin were measured over 24 h before and after telmisartan administration. In vitro experiments using a bidirectional transport assay were performed to investigate the involvement of ABCG2 in the interaction. RESULTS: Co-administration of telmisartan significantly increased the maximum plasma concentration (C max) and the area under the plasma concentration-time curve (AUC) of rosuvastatin by 71 and 26 %, respectively. The T max values were reduced after administration of telmisartan. There was no significant difference in the interaction of rosuvastatin with telmisartan between healthy volunteers and patients receiving long-term rosuvastatin therapy or among subjects with the different ABCG2 421 C>A genotypes. The in vitro experiment demonstrated that telmisartan inhibited ABCG2-mediated efflux of rosuvastatin. CONCLUSION: This study demonstrated that telmisartan significantly increased the systemic exposure to rosuvastatin after single and multiple doses.

Exploiting a novel miR-519c-HuR-ABCG2 regulatory pathway to overcome chemoresistance in colorectal cancer.

Colorectal cancer (CRC) is a major cause of mortality and morbidity worldwide. While surgery remains the mainstay of treatment for early stage CRC, adjuvant chemotherapy is usually given to reduce the risk of recurrence after colectomy. Overexpression of a multidrug resistance (MDR) transporter ABCG2 in vitro has been shown to cause resistance to 5-fluorouracil (5-FU) and irinotecan, components of the most commonly adopted regimens for treating CRC. Both anticancer drugs are known ABCG2 substrates. An effective way to predict drug response may provide guidance for better cancer treatment. We investigated the effect of ABCG2 dysregulation on cancer cell sensitivity to chemotherapy using pairs of snap-frozen paraffin-embedded archival blocks of human colorectal cancer tissues and their matched non-cancerous colon tissues from CRC patients. In CRC patients responding to chemotherapy, the tumors were found to have remarkable lower ABCG2 expression than the adjacent normal colon tissues. On the contrary, the tumors from patients not responding to 5-FU-based chemotherapy have higher ABCG2 level than the adjacent normal tissues. The high ABCG2 expression in the tumor is associated with the concomitant overexpression of the mRNA binding protein HuR but a low expression of miR-519c because miR-519c is known to target both ABCG2 and HuR. Further investigation in CRC cell lines revealed that the ABCG2 overexpression was caused by an interplay between miR-519c, HuR and the length of the 3' untranslated region (UTR) of ABCG2. These parameters may be further developed as useful biomarkers to predict patient response to adjuvant chemotherapy. Besides being predictive biomarkers, the microRNAs and mRNA binding protein identified may also be potential drug targets for modulating ABCG2 to combat resistance in CRC chemotherapy.

A gold@polydopamine core-shell nanoprobe for long-term intracellular detection of microRNAs in differentiating stem cells.

The capability of monitoring the differentiation process in living stem cells is crucial to the understanding of stem cell biology and the practical application of stem-cell-based therapies, yet conventional methods for the analysis of biomarkers related to differentiation require a large number of cells as well as cell lysis. Such requirements lead to the unavoidable loss of cell sources and preclude real-time monitoring of cellular events. In this work, we report the detection of microRNAs (miRNAs) in living human mesenchymal stem cells (hMSCs) by using polydopamine-coated gold nanoparticles (Au@PDA NPs). The PDA shell facilitates the immobilization of fluorescently labeled hairpin DNA strands (hpDNAs) that can recognize specific miRNA targets. The gold core and PDA shell quench the fluorescence of the immobilized hpDNAs, and subsequent binding of the hpDNAs to the target miRNAs leads to their dissociation from Au@PDA NPs and the recovery of fluorescence signals. Remarkably, these Au@PDA-hpDNA nanoprobes can naturally enter stem cells, which are known for their poor transfection efficiency, without the aid of transfection agents. Upon cellular uptake of these nanoprobes, we observe intense and time-dependent fluorescence responses from two important osteogenic marker miRNAs, namely, miR-29b and miR-31, only in hMSCs undergoing osteogenic differentiation and living primary osteoblasts but not in undifferentiated hMSCs and 3T3 fibroblasts. Strikingly, our nanoprobes can afford long-term tracking of miRNAs (5 days) in the differentiating hMSCs without the need of continuously replenishing cell culture medium with fresh nanoprobes. Our results demonstrate the capability of our Au@PDA-hpDNA nanoprobes for monitoring the differentiation status of hMSCs (i.e., differentiating versus undifferentiated) via the detection of specific miRNAs in living stem cells. Our nanoprobes show great promise in the investigation of the long-term dynamics of stem cell differentiation, identification and isolation of specific cell types, and high-throughput drug screening.

Synergistic cytotoxicity from combination of imatinib and platinum-based anticancer drugs specifically in Bcr-Abl positive leukemia cells.

Imatinib, a multitargeted tyrosine kinase inhibitor, exhibits potent anticancer activity against leukemia harboring the Bcr-Abl oncogene and some solid tumors overexpressing c-kit and PDGFR. However, its clinical efficacy is severely compromised by the emergence of resistance primarily due to acquired mutations in the Bcr-Abl kinase domain. In this study, we showed that combination of imatinib with platinum (Pt)-based anticancer agents, including cisplatin and oxaliplatin, exhibited synergistic cytotoxic effect specifically in Bcr-Abl+ human chronic myeloid leukemia cell line K562 but not in Bcr-Abl- RPMI8226 cells. Importantly, the synergistic effect was also found to circumvent imatinib resistance in an imatinib-selected resistant subline K562 ima1.0. The combination treatment increased apoptosis and DNA damage. Mechanistic study revealed that increased inhibition of Bcr-Abl and downstream ERK phosphorylation by the drug combination may contribute to the synergistic effect.

Synergism of colistin and globular endolysins against multidrug-resistant gram-negative bacteria.

Endolysins (lysins), a novel class of antibacterial agents derived from bacteriophages, efficiently lyse bacteria by degrading the peptidoglycan layer within the bacterial wall. Colistin, a classic peptide antibiotic with the ability to permeabilize the outer membrane, has recently shown great promise in synergizing with lysins against gram-negative bacteria. However, the exact mechanisms responsible for their synergy remain unclear. Here, we first demonstrated the synergistic bacterial killing of various lysin and colistin combinations. With a model lysin, LysAB2, we then confirmed that there is a threshold concentration of colistin causing sufficient permeabilization of the outer membrane for lysin to access the peptidoglycan layer and subsequently exert its lytic ability. The threshold colistin concentrations were found to range 0.2-0.8 µM for the tested bacteria, with the exact value largely depending on the density of lipopolysaccharides on the outer membrane. Beyond the threshold colistin level, LysAB2 could synergize with colistin at a concentration as low as 0.31 µM. Next, we proved for the first time that lysin-induced degradation of the peptidoglycan layer facilitated the disruption of cytoplasmic membrane by colistin, elevated the level of reactive oxygen species in bacterial cells, and boosted the killing effect of colistin. Additionally, the colistin-lysin combination could effectively eliminate established biofilms due to the biofilm dispersal ability of lysin. The in-vivo efficacy was preliminary confirmed in a Galleria mellonella infection model for combination with colistin doses (≥ 1.8 µg/larvae), which could reach beyond the threshold concentration, and a fixed LysAB2 dose (10 µg/larvae). In summary, our study provided the first experimental evidence unravelling the mechanisms behind the synergy of colistin and lysins. All these findings provided important insights in guiding the dosing strategy for applying this combination in future development.

Circulating tumor cells shielded with extracellular vesicle-derived CD45 evade T cell attack to enable metastasis.

Circulating tumor cells (CTCs) are precursors of distant metastasis in a subset of cancer patients. A better understanding of CTCs heterogeneity and how these CTCs survive during hematogenous dissemination could lay the foundation for therapeutic prevention of cancer metastasis. It remains elusive how CTCs evade immune surveillance and elimination by immune cells. In this study, we unequivocally identified a subpopulation of CTCs shielded with extracellular vesicle (EVs)-derived CD45 (termed as CD45+ CTCs) that resisted T cell attack. A higher percentage of CD45+ CTCs was found to be closely correlated with higher incidence of metastasis and worse prognosis in cancer patients. Moreover, CD45+ tumor cells orchestrated an immunosuppressive milieu and CD45+ CTCs exhibited remarkably stronger metastatic potential than CD45- CTCs in vivo. Mechanistically, CD45 expressing on tumor surfaces was shown to form intercellular CD45-CD45 homophilic interactions with CD45 on T cells, thereby preventing CD45 exclusion from TCR-pMHC synapse and leading to diminished TCR signaling transduction and suppressed immune response. Together, these results pointed to an underappreciated capability of EVs-derived CD45-dressed CTCs in immune evasion and metastasis, providing a rationale for targeting EVs-derived CD45 internalization by CTCs to prevent cancer metastasis.

MicroRNA: a prognostic biomarker and a possible druggable target for circumventing multidrug resistance in cancer chemotherapy.

Multidrug resistance (MDR) is a major obstacle to successful cancer treatment. It is often associated with an increased efflux of a variety of structurally unrelated anticancer drugs by ATP-binding cassette (ABC) transporters including P-gp, ABCG2 and MRP1. MicroRNAs (miRNAs) are small non-coding RNAs that govern posttranscriptional regulation of target genes by interacting with specific sequences in their 3' untranslated region (3'UTR), thereby promoting mRNA degradation or suppressing translation. Accumulating evidence suggests that alterations in miRNAs contribute to resistance to anticancer drugs. While miRNAs are well-known to be dysregulated in cancer, recent literature revealed that miRNA levels in biological samples may be correlated with chemotherapy response. This review summarized the coordinated network by which miRNA regulated MDR transporters. The usefulness of miRNAs as prognostic biomarkers for predicting chemotherapeutic outcome is discussed. MiRNAs may also represent druggable targets for circumvention of MDR.

Drug Repurposing to Circumvent Immune Checkpoint Inhibitor Resistance in Cancer Immunotherapy.

Immune checkpoint inhibitors (ICI) have achieved unprecedented clinical success in cancer treatment. However, drug resistance to ICI therapy is a major hurdle that prevents cancer patients from responding to the treatment or having durable disease control. Drug repurposing refers to the application of clinically approved drugs, with characterized pharmacological properties and known adverse effect profiles, to new indications. It has also emerged as a promising strategy to overcome drug resistance. In this review, we summarized the latest research about drug repurposing to overcome ICI resistance. Repurposed drugs work by either exerting immunostimulatory activities or abolishing the immunosuppressive tumor microenvironment (TME). Compared to the de novo drug design strategy, they provide novel and affordable treatment options to enhance cancer immunotherapy that can be readily evaluated in the clinic. Biomarkers are exploited to identify the right patient population to benefit from the repurposed drugs and drug combinations. Phenotypic screening of chemical libraries has been conducted to search for T-cell-modifying drugs. Genomics and integrated bioinformatics analysis, artificial intelligence, machine and deep learning approaches are employed to identify novel modulators of the immunosuppressive TME.

Repurposing of triamterene as a histone deacetylase inhibitor to overcome cisplatin resistance in lung cancer treatment.

PURPOSE: Cisplatin is the core chemotherapeutic drug used for first-line treatment of advanced non-small cell lung cancer (NSCLC). However, drug resistance is severely hindering its clinical efficacy. This study investigated the circumvention of cisplatin resistance by repurposing non-oncology drugs with putative histone deacetylase (HDAC) inhibitory effect. METHODS: A few clinically approved drugs were identified by a computational drug repurposing tool called "DRUGSURV" and evaluated for HDAC inhibition. Triamterene, originally indicated as a diuretic, was chosen for further investigation in pairs of parental and cisplatin-resistant NSCLC cell lines. Sulforhodamine B assay was used to evaluate cell proliferation. Western blot analysis was performed to examine histone acetylation. Flow cytometry was used to examine apoptosis and cell cycle effects. Chromatin immunoprecipitation was conducted to investigate the interaction of transcription factors to the promoter of genes regulating cisplatin uptake and cell cycle progression. The circumvention of cisplatin resistance by triamterene was further verified in a patient-derived tumor xenograft (PDX) from a cisplatin-refractory NSCLC patient. RESULTS: Triamterene was found to inhibit HDACs. It was shown to enhance cellular cisplatin accumulation and potentiate cisplatin-induced cell cycle arrest, DNA damage, and apoptosis. Mechanistically, triamterene was found to induce histone acetylation in chromatin, thereby reducing the association of HDAC1 but promoting the interaction of Sp1 with the gene promoter of hCTR1 and p21. Triamterene was further shown to potentiate the anti-cancer effect of cisplatin in cisplatin-resistant PDX in vivo. CONCLUSION: The findings advocate further clinical evaluation of the repurposing use of triamterene to overcome cisplatin resistance.

Sequential treatment effects on phage-antibiotic synergistic application against multi-drug-resistant Acinetobacter baumannii.

Bacteriophage (phage) therapy, exploiting phages which are the natural enemies of bacteria, has been re-introduced to treat multidrug-resistant (MDR) bacterial infections. However, some intrinsic drawbacks of phages are overshadowing their clinical use, particularly the narrow host spectrum and rapid emergence of resistance upon treatment. The use of phage-antibiotic combinations exhibiting synergistic bacterial killing [termed 'phage-antibiotic synergy' (PAS)] has therefore been proposed. It is well reported that the types and doses of phages and antibiotics are critical in achieving PAS. However, the impact of treatment order has received less research attention. As such, this study used an Acinetobacter baumannii phage vB_AbaM-IME-AB2 and colistin as a model PAS combination to elucidate the order effects in-vitro. While application of the phage 8 h before colistin treatment demonstrated the greatest antibacterial synergy, it failed to prevent the development of phage resistance. On the other hand, simultaneous application and antibiotic followed by phage application were able to suppress/delay the development of resistance effectively, and simultaneous application demonstrated superior antibacterial and antibiofilm activities. Further in-vivo investigation is required to confirm the impact of treatment order on PAS.

A thermosensitive hydrogel formulation of phage and colistin combination for the management of multidrug-resistant Acinetobacter baumannii wound infections.

Chronic skin wounds are often associated with multidrug-resistant bacteria, impeding the healing process. Bacteriophage (phage) therapy has been revitalized as a promising strategy to counter the growing concerns of antibiotic resistance. However, phage monotherapy also faces several application drawbacks, such as a narrow host spectrum, the advent of resistant phenotypes and poor stability of phage preparations. Phage-antibiotic synergistic (PAS) combination therapy has recently been suggested as a possible approach to overcome these shortcomings. In the present study, we employed a model PAS combination containing a vB_AbaM-IME-AB2 phage and colistin to develop stable wound dressings of PAS to mitigate infections associated with Acinetobacter baumannii. A set of thermosensitive hydrogels were synthesized with varying amounts of Pluronic® F-127 (PF-127 at 15, 17.5 and 20 w/w%) modified with/without 3 w/w% hydroxypropyl methylcellulose (HPMC). Most hydrogel formulations had a gelation temperature around skin temperature, suitable for topical application. The solidified gels were capable of releasing the encapsulated phage and colistin in a sustained manner to kill bacteria. The highest bactericidal effect was achieved with the formulation containing 17.5% PF-127 and 3% HPMC (F5), which effectively killed bacteria in both planktonic (by 5.66 log) and biofilm (by 3 log) states and inhibited bacterial regrowth. Good storage stability of F5 was also noted with negligible activity loss after 9 months of storage at 4 °C. The ex vivo antibacterial efficacy of the F5 hydrogel formulation was also investigated in a pork skin wound infection model, where it significantly reduced the bacterial burden by 4.65 log. These positive outcomes warrant its further development as a topical PAS-wound dressing.

Circumvention of Gefitinib Resistance by Repurposing Flunarizine via Histone Deacetylase Inhibition.

Gefitinib is an epidermal growth factor receptor tyrosine kinase inhibitor (EGFR TKI) for treating advanced non-small cell lung cancer (NSCLC). However, drug resistance seriously impedes the clinical efficacy of gefitinib. This study investigated the repositioning of the non-oncology drug capable of inhibiting histone deacetylases (HDACs) to overcome gefitinib resistance. A few drug candidates were identified using the in silico repurposing tool "DRUGSURV" and tested for HDAC inhibition. Flunarizine, originally indicated for migraine prophylaxis and vertigo treatment, was selected for detailed investigation in NSCLC cell lines harboring a range of different gefitinib resistance mechanisms (EGFR T790M, KRAS G12S, MET amplification, or PTEN loss). The circumvention of gefitinib resistance by flunarizine was further demonstrated in an EGFR TKI (erlotinib)-refractory patient-derived tumor xenograft (PDX) model in vivo. The acetylation level of cellular histone protein was increased by flunarizine in a concentration- and time-dependent manner. Among the NSCLC cell lines evaluated, the extent of gefitinib resistance circumvention by flunarizine was found to be the most pronounced in EGFR T790M-bearing H1975 cells. The gefitinib-flunarizine combination was shown to induce the apoptotic protein Bim but reduce the antiapoptotic protein Bcl-2, which apparently circumvented gefitinib resistance. The induction of Bim by flunarizine was accompanied by an increase in the histone acetylation and E2F1 interaction with the BIM gene promoter. Flunarizine was also found to upregulate E-cadherin but downregulate the vimentin expression, which subsequently inhibited cancer cell migration and invasion. Importantly, flunarizine was also shown to significantly potentiate the tumor growth suppressive effect of gefitinib in EGFR TKI-refractory PDX in vivo. The findings advocate for the translational application of flunarizine to circumvent gefitinib resistance in the clinic.