Drug-binding Domain Research Articles

Computationally accelerated identification of P-glycoprotein inhibitors.

Overexpression of the polyspecific efflux transporter, P-glycoprotein (P-gp, MDR1, ABCB1 ), is a major mechanism by which cancer cells acquire multidrug resistance (MDR), the resistance to diverse chemotherapeutic drugs. Inhibiting drug transport by P-gp can resensitize cancer cells to chemotherapy, but there are no P-gp inhibitors available to patients. Clinically unsuccessful P-gp inhibitors tend to bind at the pump's transmembrane drug binding domains and are often P-gp transport substrates, resulting in lowered intracellular concentration of the drug and altered pharmacokinetics. In prior work, we used computationally accelerated drug discovery to identify novel P-gp inhibitors that target the pump's cytoplasmic nucleotide binding domains. Our first-draft study provided conclusive evidence that the nucleotide binding domains of P-gp are viable targets for drug discovery. Here we develop an enhanced, computationally accelerated drug discovery pipeline that expands upon our prior work by iteratively screening compounds against multiple conformations of P-gp with molecular docking. Targeted molecular dynamics simulations with our homology model of human P-gp were used to generate docking receptors in conformations mimicking a putative drug transport cycle. We offset the increased computational complexity using custom Tanimoto chemical datasets, which maximize the chemical diversity of ligands screened by docking. Using our expanded, virtual-assisted pipeline, we identified nine novel P-gp inhibitors that reverse MDR in two types of P-gp overexpressing human cancer cell lines, reflecting a 13.4% hit rate. Of these inhibitors, all were non-toxic to non-cancerous human cells, and six were not likely to be transport substrates of P-gp. Our novel P-gp inhibitors are chemically diverse and are good candidates for lead optimization. Our results demonstrate that the nucleotide binding domains of P-gp are an underappreciated target in the effort to reverse P-gp-mediated multidrug resistance in cancer.

Novel pyxinol amide derivatives bearing an aliphatic heterocycle as P-glycoprotein modulators for overcoming multidrug resistance

P-glycoprotein (Pgp) modulators are promising agents for overcoming multidrug resistance (MDR) in cancer chemotherapy. In this study, via structural optimization of our lead compound S54 (nonsubstrate allosteric inhibitor of Pgp), 29 novel pyxinol amide derivatives bearing an aliphatic heterocycle were designed, synthesized, and screened for MDR reversal activity in KBV cells. Unlike S54, these active derivatives were shown to transport substrates of Pgp. The most potent derivative 4c exhibited promising MDR reversal activity (IC50 of paclitaxel = 8.80 ± 0.56 nM, reversal fold = 211.8), which was slightly better than that of third-generation Pgp modulator tariquidar (IC50 of paclitaxel = 9.02 ± 0.35 nM, reversal fold = 206.6). Moreover, the cytotoxicity of this derivative was 8-fold lower than that of tariquidar in human normal HK-2 cells. Furthermore, 4c blocked the efflux function of Pgp and displayed high selectivity for Pgp but had no effect on its expression and distribution. Molecular docking revealed that 4c bound preferentially to the drug-binding domain of Pgp. Overall, 4c is a promising lead compound for developing Pgp modulators.

Design and synthesis of APN and 3CLpro dual-target inhibitors based on STSBPT with anticoronavirus activity.

Coronaviruses (CoVs) have continuously posed a threat to human and animal health. However, existing antiviral drugs are still insufficient in overcoming the challenges caused by multiple strains of CoVs. And methods for developing multi-target drugs are limited in terms of exploring drug targets with similar functions or structures. In this study, four rounds of structural design and modification on salinomycin were performed for novel antiviral compounds. It was based on the strategy of similar topological structure binding properties of protein targets (STSBPT), resulting in the high-efficient synthesis of the optimal compound M1, which could bind to aminopeptidase N and 3C-like protease from hosts and viruses, respectively, and exhibit a broad-spectrum antiviral effect against severe acute respiratory syndrome CoV 2 pseudovirus, porcine epidemic diarrhea virus, transmissible gastroenteritis virus, feline infectious peritonitis virus and mouse hepatitis virus. Furthermore, the drug-binding domains of these proteins were found to be structurally similar based on the STSBPT strategy. The compounds screened and designed based on this region were expected to have broad-spectrum and strong antiviral activities. The STSBPT strategy is expected to be a fundamental tool in accelerating the discovery of multiple targets with similar effects and drugs.

Foretinib, a c-MET receptor tyrosine kinase inhibitor, tackles multidrug resistance in cancer cells by inhibiting ABCB1 and ABCG2 transporters

BackgroundABC transporter-mediated multidrug resistance (MDR) remains a major obstacle for cancer pharmacological treatment. Some tyrosine kinase inhibitors (TKIs) have been shown to reverse MDR. The present study was designed to evaluate for the first time whether foretinib, a multitargeted TKI, can circumvent ABCB1 and ABCG2-mediated MDR in treatment-resistant cancer models. MethodsAccumulation of fluorescent substrates of ABCB1 and ABCG2 in ABCB1-overexpressing MES-SA/DX5 and ABCG2-overexpressing MCF-7/MX and their parenteral cells was evaluated by flow cytometry. The growth inhibitory activity of single and combination therapy of foretinib and chemotherapeutic drugs on MDR cells was examined by MTT assay. Analysis of combined interaction effects was performed using CalcuSyn software. ResultsIt was firstly proved that foretinib increased the intracellular accumulation of rhodamine 123 and mitoxantrone in MES-SA/DX5 and MCF-7/MX cancer cells, with accumulation ratios of 12 and 2.2 at 25 μM concentration, respectively. However, it did not affect the accumulation of fluorescent substrates in the parental cells. Moreover, foretinib synergistically improved the cytotoxic effects of doxorubicin and mitoxantrone. The means of combination index (CI) values at fraction affected (Fa) values of 0.5, 0.75, and 0.9 were 0.64 ± 0.08 and 0.47 ± 0.09, in MES-SA/DX5 and MCF-7/MX cancer cells, respectively. In silico analysis also suggested that the drug-binding domain of ABCB1 and ABCG2 transporters could be considered as potential target for foretinib. ConclusionOverall, our results suggest that foretinib can target MDR-linked ABCB1 and ABCG2 transporters in clinical cancer therapy.

Structure-based discovery of novel P-glycoprotein inhibitors targeting the nucleotide binding domains

P-glycoprotein (P-gp), a membrane transport protein overexpressed in certain drug-resistant cancer cells, has been the target of numerous drug discovery projects aimed at overcoming drug resistance in cancer. Most characterized P-gp inhibitors bind at the large hydrophobic drug binding domain (DBD), but none have yet attained regulatory approval. In this study, we explored the potential of designing inhibitors that target the nucleotide binding domains (NBDs), by computationally screening a large library of 2.6 billion synthesizable molecules, using a combination of machine learning-guided molecular docking and molecular dynamics (MD). 14 of the computationally best-scoring molecules were subsequently tested for their ability to inhibit P-gp mediated calcein-AM efflux. In total, five diverse compounds exhibited inhibitory effects in the calcein-AM assay without displaying toxicity. The activity of these compounds was confirmed by their ability to decrease the verapamil-stimulated ATPase activity of P-gp in a subsequent assay. The discovery of these five novel P-gp inhibitors demonstrates the potential of in-silico screening in drug discovery and provides a new stepping point towards future potent P-gp inhibitors.

Evaluation of the FDA-approved kinase inhibitors to uncover the potential repurposing candidates targeting ABC transporters in multidrug-resistant cancer cells: an in silico approach

Multiple drug resistance (MDR) is characterized by the resistance of cancer cells to a broad spectrum of anticancer drugs. The main mechanism underlying the MDR phenotype is the overexpression of ATP-binding cassette (ABC) transporters by promoting active drug efflux from cancer cells. Some small-molecule protein kinase inhibitors have been found to overcome MDR by inhibiting ABC transporters as substrates or modulators. This study investigated the chemical activity of 58 FDA-approved anticancer kinase inhibitors against three multidrug resistance-related proteins. The studied proteins are ATP-Binding Cassette Sub-Family B Member 1 (ABCB1), ATP-Binding Cassette Subfamily C Member 1 (ABCC1), and ATP-binding cassette superfamily G member 2 (ABCG2). The drug-binding domain and ATP binding sites of the proteins were considered the kinase inhibitors’ probable target. High-throughput virtual screening and molecular docking were employed to find the hit drugs, and the drugs with the highest binding affinity were further evaluated using the molecular dynamics (MD) simulation. The virtual screening revealed that several kinase inhibitors could be considered potential inhibitors of ABCB1, ABCC1, and ABCG2, among which larotrectinib, entrectinib, and infigratinib showed the highest binding affinity, respectively. Based on the obtained results from MD simulation, these drugs can form strong interactions with the essential residues of the target proteins. In silico investigation revealed that larotrectinib, entrectinib, and infigratinib can target the key residues of the studied proteins. Therefore, these approved kinase inhibitors could be considered potential therapies for MDR cancers by targeting these transporters. Communicated by Ramaswamy H. Sarma

High levels of CRBN isoform lacking IMiDs binding domain predicts for a worse response to IMiDs-based upfront therapy in newly diagnosed myeloma patients

In recent years, the immunoderivative (IMiD) agents have been extensively used for the treatment of multiple myeloma (MM). IMiDs and their newer derivatives CRBN E3 ligase modulator bind the E3 ligase substrate recognition adapter protein cereblon (CRBN), which has been recognized as one of the IMiDs’ direct target proteins, and it is essential for the therapeutic effect of these agents.High expression of CRBN was associated with improved clinical response in patients with MM treated with IMiDs, further confirming that the expression of IMiDs’ direct target protein CRBN is required for the anti-MM activity. CRBN’s central role as a target of IMiDs suggests potential utility as a predictive biomarker of response or resistance to IMiDs therapy. Additionally, the presence of alternatively spliced variants of CRBN in MM cells, especially those lacking the drug-binding domain for IMiDs, raise questions concerning their potential biological function, making difficult the transcript measurement, which leads to inaccurate overestimation of full-length CRBN transcripts. In sight of this, in the present study, we evaluated the CRBN expression, both full-length and spliced isoforms, by using real-time assay data from 87 patients and RNA sequencing data from 50 patients (n = 137 newly diagnosed MM patients), aiming at defining CRBN’s role as a predictive biomarker for response to IMiDs-based induction therapy. We found that the expression level of the spliced isoform tends to be higher in not-responding patients, confirming that the presence of a more CRBN spliced transcript predicts for lack of IMiDs response.

Mechanism behind Polysorbates' Inhibitory Effect on P-Glycoprotein.

Much effort has been invested in the search for modulators of membrane transport proteins such as P-glycoprotein (P-gp) to improve drug bioavailability and reverse multidrug resistance in cancer. Nonionic surfactants, a class of pharmaceutical excipients, are known to inhibit such proteins, but knowledge about the exact mechanism of this inhibition is scarce. Here, we perform multiscale molecular dynamics simulations of one of these surfactants, polysorbate 20 (PS20), to reveal the behavior of such compounds on the molecular level and thereby discover the molecular mechanism of the P-gp inhibition. We show that the amphiphilic headgroup of PS20 is too hydrophobic to partition in the water phase, which drives the binding of PS20 to the amphiphilic drug-binding domain of P-gp and thereby causes the inhibition of the protein. Based on our findings, we conclude that PS20 primarily inhibits P-gp through direct binding to the drug-binding domain (DBD) from the extracellular leaflet.

Utilization of Photoaffinity Labeling to Investigate Binding of Microtubule Stabilizing Agents to P-Glycoprotein and β-Tubulin.

Photoaffinity labeling approaches have historically been used in pharmacology to identify molecular targets. This methodology has played a pivotal role in identifying drug-binding domains and searching for novel compounds that may interact at these domains. In this review we focus on studies of microtubule stabilizing agents of natural product origin, specifically taxol (paclitaxel). Taxol and other microtubule interacting agents bind to both P-glycoprotein (ABCB1), a drug efflux pump that reduces intracellular drug accumulation, and the tubulin/microtubule system. Both binding relationships modulate drug efficacy and are of immense interest to basic and translational scientists, primarily because of their association with drug resistance for this class of molecules. We present this body of work and acknowledge its value as fundamental to understanding the mechanisms of taxol and elucidation of the taxol pharmacophore. Furthermore, we highlight the ability to multiplex photoaffinity approaches with other technologies to further enhance our understanding of pharmacologic interactions at an atomic level. Thus, photoaffinity approaches offer a relatively inexpensive and robust technique that will continue to play an important role in drug discovery for the foreseeable future.

Towards establishment of a plant-based model to assess the novel anti-cancerous lead molecule(s): An in silico, in vivo and in vitro assessment of some potential anti-cancerous drugs on Lathyrus sativus L.

The drug development process is one of the important aspects of medical biology. The classical lead identification strategy in the way of drug development based on animal cell is time-consuming, expensive and involving ethical issues. The following study aims to develop a novel plant-based screening of drugs. Study shows the efficacy of certain anti-cancerous drugs (Pemetrexed, 5-Fluorouracil, Methotrexate, Topotecan and Etoposide) on a plant-based (Lathyrus sativus L.) system. Two important characteristics of cancer cells were observed in the colchicine-treated polyploid cell and the callus, where the chromosome numbers were unusual and the division of cells were uncontrolled respectively. With increasing concentration, the drugs significantly reduced the mitotic index, ploidy level and callus growth. Increasing Pemetrexed concentration decreased the plant DHFR activity. A decrease in total RNA content was observed in 5-FU and Methotrexate with increasing concentrations of the drugs. Etoposide and Topotecan inhibited plant topoisomerase II and topoisomerase I activities, which was justified through plasmid nicking and comet assay, respectively. Molecular and biochemical study revealed similar results to the animal system. Thein silicostudy had been done, and the structural similarity of drug binding domains of L. sativus and human beings had also been established. The binding site of the selected drugs to the domains of plant target proteins was also determined. Experimental results are significant in terms of the efficacy of known anti-cancerous drugs on the plant-based system. The proposed assay system is a cost-effective, convenient and less time-consuming process for primary screening of anti-cancerous lead molecules.

HSA-Lys-161 covalent bound fluorescent dye for in vivo blood drug dynamic imaging and tumor mapping.

The specific combination of human serum albumin and fluorescent dye will endow superior performance to a coupled fluorescent platform for in vivo fluorescence labeling. In this study, we found that lysine-161 in human serum albumin is a covalent binding site and could spontaneously bind a ketone skeleton quinoxaline–coumarin fluorescent dye with a specific turn-on fluorescence signal for the first time. Supported by the abundant drug binding domains in human serum albumin, drugs such as ibuprofen, warfarin and clopidogrel could interact with the fluorescent dye labeled human serum albumin to feature a substantial enhancement in fluorescence intensity (6.6-fold for ibuprofen, 4.5-fold for warfarin and 5-fold for clopidogrel). The drug concentration dependent fluorescence intensity amplification realized real-time, in situ blood drug concentration monitoring in mice, utilizing ibuprofen as a model drug. The non-invasive method avoided continuous blood sample collection, which fundamentally causes suffering and consumption of experimental animals in the study of pharmacokinetics. At the same time, the coupled fluorescent probe can be efficiently enriched in tumors in mice which could map a tumor with a high-contrast red fluorescence signal and could hold great potential in clinical tumor marking and surgical resection.

Target Identification of Small Molecules Using Large-Scale CRISPR-Cas Mutagenesis Scanning of Essential Genes.

Target deconvolution of new bioactive agents identified from phenotypic screens remains a challenging task. The discovery of mutations that confer resistance to such agents is regarded as the gold standard proof of target identification. Here, we describe a method that exploits the error-prone repair of CRISPR-induced DNA double-strand breaks to enhance mutagenesis and increase the incidence of drug resistancemutations in essential genes. As each DNA double-strand break is introduced at a targeted genomic site predefined by the presence of a protospacer adjacent motif (PAM) and a particular CRISPR single guide RNA (sgRNA), the genetic location of drug resistance mutations can be easily uncovered through targeted sequencing of CRISPR sgRNAs. Moreover, the method allows for the identification of not only the drug target gene, but also the drug-binding domain within the target gene.

PTEN deletion drives acute myeloid leukemia resistance to MEK inhibitors.

Kinases such as MEK are attractive targets for novel therapy in cancer, including acute myeloid leukaemia (AML). Acquired and inherent resistance to kinase inhibitors, however, is becoming an increasingly important challenge for the clinical success of such therapeutics, and often arises from mutations in the drug-binding domain of the target kinase. To identify possible causes of resistance to MEK inhibition, we generated a model of resistance by long-term treatment of AML cells with AZD6244 (selumetinib). Remarkably, resistance to MEK inhibition was due to acquired PTEN haploinsufficiency, rather than mutation of MEK. Resistance via this mechanism was confirmed using CRISPR/Cas9 technology targeting exon 5 of PTEN. While PTEN loss has been previously implicated in resistance to a number of other therapeutic agents, this is the first time that it has been shown directly and in AML.

Explorations of Drug Transport by P-Glycoprotein using Molecular Dynamics Enabled by High Resolution Crystal Structures

The integral membrane efflux pump P-glycoprotein (P-gp, ABCB1) is a causative agent of multidrug resistance (MDR) to a wide variety of chemotherapeutics in human cancers. In many cancer subtypes, chemotherapy treatment can both induce and select for the overexpression of P-gp. When P-gp is overexpressed, the pump lowers the intracellular concentration of many drugs to sub-therapeutic levels, thereby conferring general MDR to the cancer, and rendering further chemotherapeutic treatment ineffective. Given the clinical importance of the enzyme, P-gp has long been a target for drug discovery and the focus of extensive mechanistic research. Until recently, the lack of known human P-gp structures has hindered efforts to understand the unusually polyspecific substrate profile and complex transport mechanism of the enzyme. Prior research by our laboratory has demonstrated the possibility of multiple transport pathways through the drug binding domains (DBDs) of the transporter, and of variable substrate binding sites using targeted molecular dynamics (TMD) simulations on homology models of human P-gp. Following the recent release of the cryo-EM structure of human P-gp, we performed novel simulations of the solved structure using four known, low energy conformations of P-gp homologues in various states along a putative ABC transporter catalytic efflux cycle. These simulations were done at long timescales using a combination of free and directed GPU-accelerated molecular dynamics with NAMD. These analyses included the new human P-gp structure and demonstrated the pumping of known P-gp substrates across the cell membrane. Parameterizations and simulations of molecules that are either suspected transport substrates or putative transport inhibitors of P-gp were performed. These computational studies support earlier observations, and explore the hypothetical mechanisms of P-gp-mediated substrate efflux and of P-gp transport inhibition. This work was supported by NIH NIGMS [R15GM094771-02].

The C terminus of the bacterial multidrug transporter EmrE couples drug binding to proton release

Ion-coupled transporters must regulate access of ions and substrates into and out of the binding site to actively transport substrates and minimize dissipative leak of ions. Within the single-site alternating access model, competitive substrate binding forms the foundation of ion-coupled antiport. Strict competition between substrates leads to stoichiometric antiport without slippage. However, recent NMR studies of the bacterial multidrug transporter EmrE have demonstrated that this multidrug transporter can simultaneously bind drug and proton, which will affect the transport stoichiometry and efficiency of coupled antiport. Here, we investigated the nature of substrate competition in EmrE using multiple methods to measure proton release upon the addition of saturating concentrations of drug as a function of pH. The resulting proton-release profile confirmed simultaneous binding of drug and proton, but suggested that a residue outside EmrE's Glu-14 binding site may release protons upon drug binding. Using NMR-monitored pH titrations, we trace this drug-induced deprotonation event to His-110, EmrE's C-terminal residue. Further NMR experiments disclosed that the C-terminal tail is strongly coupled to EmrE's drug-binding domain. Consideration of our results alongside those from previous studies of EmrE suggests that this conserved tail participates in secondary gating of EmrE-mediated proton/drug transport, occluding the binding pocket of fully protonated EmrE in the absence of drug to prevent dissipative proton transport.

Molecular insights into antibiotic resistance - how a binding protein traps albicidin

The worldwide emergence of antibiotic resistance poses a serious threat to human health. A molecular understanding of resistance strategies employed by bacteria is obligatory to generate less-susceptible antibiotics. Albicidin is a highly potent antibacterial compound synthesized by the plant-pathogenic bacterium Xanthomonas albilineans. The drug-binding protein AlbA confers albicidin resistance to Klebsiella oxytoca. Here we show that AlbA binds albicidin with low nanomolar affinity resulting in full inhibition of its antibacterial activity. We report on the crystal structure of the drug-binding domain of AlbA (AlbAS) in complex with albicidin. Both α-helical repeat domains of AlbAS are required to cooperatively clamp albicidin, which is unusual for drug-binding proteins of the MerR family. Structure-guided NMR binding studies employing synthetic albicidin derivatives give valuable information about ligand promiscuity of AlbAS. Our findings thus expand the general understanding of antibiotic resistance mechanisms and support current drug-design efforts directed at more effective albicidin analogs.

Novel Inhibitors of P‐Glycoprotein from In Silico Optimizations of Inhibitor SMU‐29 using the ChemGen Program

P‐glycoprotein (P‐gp) is an integral membrane efflux pump that is capable of lowering the intracellular concentration of many drugs to sub‐therapeutic levels. Consequently, P‐gp has been implicated in multidrug resistances (MDR) to cancer chemotherapies. One promising P‐gp inhibitor, SMU‐29, was previously identified by us using in silico methods (Brewer et al., Molecular Pharmacology 86, 716–726, 2014) and was later confirmed to reverse MDR in cancer cell culture experiments (Follit et al., Pharmacol. Res. Perspect. 3, e00170, 2015). We created millions of SMU‐29 variants in silico using our novel medicinal chemistry program, ChemGen, in efforts to pharmacologically optimize SMU‐29. In one set of chemical variants, only part of the structure of SMU‐29 was varied; in a second set of variants, only the central structural scaffold of SMU‐29 was conserved. We used in silico docking to identify chemical variants of SMU‐29 that exhibited high estimated affinities for P‐gp's nucleotide binding domains (NBDs), and low estimated affinity for P‐gp's transmembrane drug‐binding domain (DBD). Using this approach, we identified over 2000 ChemGen‐created variants with equivalent or better estimated affinities at the P‐gp NBDs relative to SMU‐29. We selected a small set of these SMU‐29 variants for chemical synthesis and further screening in vitro against multidrug resistant cancer cell lines. All of the tested and synthesized SMU‐29 variants were observed to act as P‐gp inhibitors with improved PC50 values. Some of these variants were also observed to inhibit the breast cancer resistance protein (BCRP), a related ABC‐transporter that is also implicated in MDR in cancer. Our previous screens that identified SMU‐29 as a hit compound had a 33% P‐gp inhibitor identification success rate (hit rate); the present in silico optimization of SMU‐29 using ChemGen has demonstrated a very high success rate of identifying P‐gp inhibitors with improved affinities for the target protein.Support or Funding InformationThis work is supported by NIH NIGMS [R15GM094771‐02] to John G. Wise, SMU University Research Council, the SMU Center for Drug Discovery, Design and Delivery, the Communities Foundation of Texas, and a private gift from Ms. Suzy Ruff of Dallas, Texas.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Targeted inhibitors of P-glycoprotein increase chemotherapeutic-induced mortality of multidrug resistant tumor cells

Overexpression of ATP-binding cassette (ABC) transporters is often linked to multidrug resistance (MDR) in cancer chemotherapies. P-glycoprotein (P-gp) is one of the best studied drug transporters associated with MDR. There are currently no approved drugs available for clinical use in cancer chemotherapies to reverse MDR by inhibiting P-glycoprotein. Using computational studies, we previously identified several compounds that inhibit P-gp by targeting its nucleotide binding domain and avoiding its drug binding domains. Several of these compounds showed successful MDR reversal when tested on a drug resistant prostate cancer cell line. Using conventional two-dimensional cell culture of MDR ovarian and prostate cancer cells and three dimensional prostate cancer microtumor spheroids, we demonstrated here that co-administration with chemotherapeutics significantly decreased cell viability and survival as well as cell motility. The P-gp inhibitors were not observed to be toxic on their own. The inhibitors increased cellular retention of chemotherapeutics and reporter compounds known to be transport substrates of P-gp. We also showed that these compounds are not transport substrates of P-gp and that two of the three inhibit P-gp, but not the closely related ABC transporter, ABCG2/BCRP. The results presented suggest that these P-gp inhibitors may be promising leads for future drug development.

Basal cell carcinoma pathogenesis and therapy involving hedgehog signaling and beyond.

Basal cell carcinoma (BCC) of the skin is driven by aberrant hedgehog signaling. Thus blocking this signaling pathway by small molecules such as vismodegib inhibits tumor growth. Primary cilium in the epidermal cells plays an integral role in the processing of hedgehog signaling-related proteins. Recent genomic studies point to the involvement of additional genetic mutations that might be associated with the development of BCCs, suggesting significance of other signaling pathways, such as WNT, NOTCH, mTOR, and Hippo, aside from hedgehog in the pathogenesis of this human neoplasm. Some of these pathways could be regulated by noncoding microRNA. Altered microRNA expression profile is recognized with the progression of these lesions. Stopping treatment with Smoothened (SMO) inhibitors often leads to tumor reoccurrence in the patients with basal cell nevus syndrome, who develop 10-100 of BCCs. In addition, the initial effectiveness of these SMO inhibitors is impaired due to the onset of mutations in the drug-binding domain of SMO. These data point to a need to develop strategies to overcome tumor recurrence and resistance and to enhance efficacy by developing novel single agent-based or multiple agents-based combinatorial approaches. Immunotherapy and photodynamic therapy could be additional successful approaches particularly if developed in combination with chemotherapy for inoperable and metastatic BCCs.

Gaining Insights into Specific Drug Formulation Additives for Solubilizing a Potential Anti-Alzheimer Disease Drug B4A1.

The pharmacological profiles of small molecule drugs are often challenged by their poor water solubility. Sequence-defined peptides attached to poly(ethylene glycol) (PEG) offer opportunities to overcome these difficulties by acting as drug-specific formulation additives. The peptide-PEG conjugates enable specific, noncovalent drug binding via tailored peptide/drug interactions as well as provide water solubility and drug shielding by well-solvated PEG-blocks. A systematic set of specific solubilizers for B4A1 as a potential anti-Alzheimer disease drug is synthesized and variations involve the length of the PEG-blocks as well as the sequences of the peptidic drug-binding domain. The solubilizer/B4A1 complexes are studied in order to understand contributions of both PEG and peptide segments on drug payload capacities, drug/carrier aggregate sizes, and influences on inhibition of the Tau-protein aggregation in an in vitro assay.