The camptothecins

The gut microbiome: an orchestrator of xenobiotic metabolism

Microbes inhabiting the intestinal tract of humans represent a site for xenobiotic metabolism. The gut microbiome, the collection of microorganisms in the gastrointestinal tract, can alter the metabolic outcome of pharmaceuticals, environmental toxicants, and heavy metals, thereby changing their pharmacokinetics. Direct chemical modification of xenobiotics by the gut microbiome, either through the intestinal tract or re-entering the gut via enterohepatic circulation, can lead to increased metabolism or bioactivation, depending on the enzymatic activity within the microbial niche. Unique enzymes encoded within the microbiome include those that reverse the modifications imparted by host detoxification pathways. Additionally, the microbiome can limit xenobiotic absorption in the small intestine by increasing the expression of cell-cell adhesion proteins, supporting the protective mucosal layer, and/or directly sequestering chemicals. Lastly, host gene expression is regulated by the microbiome, including CYP450s, multi-drug resistance proteins, and the transcription factors that regulate them. While the microbiome affects the host and pharmacokinetics of the xenobiotic, xenobiotics can also influence the viability and metabolism of the microbiome. Our understanding of the complex interconnectedness between host, microbiome, and metabolism will advance with new modeling systems, technology development and refinement, and mechanistic studies focused on the contribution of human and microbial metabolism.

Dual Inhibitors as a New Challenge for Cancer Multidrug Resistance Treatment

BACKGROUND

Dual-targeting in cancer treatment by a single drug is an unconventional approach in relation to drug combinations. The rationale for the development of dualtargeting agents is to overcome incomplete efficacy and drug resistance frequently present when applying individual targeting agents. Consequently, -a more favorable outcome of cancer treatment is expected with dual-targeting strategies.

METHODS

We reviewed the literature, concentrating on the association between clinically relevant and/or novel dual inhibitors with the potential to modulate multidrug resistant phenotype of cancer cells, particularly the activity of P-glycoprotein. A balanced analysis of content was performed to emphasize the most important findings and optimize the structure of this review.

RESULTS

Two-hundred and forty-five papers were included in the review. The introductory part was interpreted by 9 papers. Tyrosine kinase inhibitors' role in the inhibition of Pglycoprotein and chemosensitization was illustrated by 87 papers. The contribution of naturalbased compounds in overcoming multidrug resistance was reviewed using 92 papers, while specific dual inhibitors acting against microtubule assembling and/or topoisomerases were described with 55 papers. Eleven papers gave an insight into a novel and less explored approach with hybrid drugs. Their influence on P-glycoprotein and multidrug resistance was also evaluated.

CONCLUSION

These findings bring into focus rational anticancer strategies with dual-targeting agents. Most evaluated synthetic and natural drugs showed a great potential in chemosensitization. Further steps in this direction are needed for the optimization of anticancer treatment.

Polymer conjugated graphene-oxide nanoparticles impair nuclear DNA and Topoisomerase I in cancer

Cancer chemotherapy had been dominated by the use of small molecule DNA damaging drugs. Eventually, the emergence of DNA damage repair machinery in cancer cells has led to combination therapy with the DNA topology controlling enzyme, topoisomerase I inhibitor along with DNA impairing agents. However, integrating multiple drugs having diverse water solubility and hence bio-distribution effectively for cancer treatment remains a significant challenge, which can be addressed by using suitable nano-scale materials. Herein, we have chemically conjugated graphene oxide (GO) with biocompatible and hydrophilic polymers [polyethylene glycol (PEG) and ethylene-diamine modified poly-isobutylene-maleic anhydride (PMA-ED)], which can encompass highly hydrophobic topoisomerase I inhibitor, SN38. Interestingly, these sheet structured GO-polymer-SN38 composites self-assembled into spherical nanoparticles in water after complexing with a hydrophilic DNA damaging drug, cisplatin. These nanoparticles showed much improved colloidal stability in water compared to their drug-loaded non-polymeric counterpart. These SN38 and cisplatin laden GO-polymer nanoparticles were taken up by HeLa cancer cells through clathrin-dependent endocytosis to home into lysosomes within 6 h, as confirmed by confocal microscopy. A combination of gel electrophoresis, flow cytometry, and fluorescence microscopy showed that these nanoparticles damaged nuclear DNA and induced topoisomerase I inhibition leading to apoptosis and finally improved HeLa cell death. These self-assembled GO-polymer nanoparticles can be used for strategic impairment of multiple cellular targets involving hydrophobic and hydrophilic drugs for effective combination therapy.

Repurposing of Cetuximab in antibody-directed chemotherapy-loaded nanoparticles in EGFR therapy-resistant pancreatic tumours

The anti-Epidermal Growth Factor Receptor (EGFR) antibody Cetuximab (CTX) has demonstrated limited anti-cancer efficacy in cells overexpressing EGFR due to activating mutations in RAS in solid tumours, such as pancreatic cancer. The utilisation of antibodies as targeting components of antibody-drug conjugates, such as trastuzumab emtansine (Kadcyla), demonstrates that antibodies may be repurposed to direct therapeutic agents to antibody-resistant cancers. Here we investigated the use of CTX as a targeting agent for camptothecin (CPT)-loaded polymeric nanoparticles (NPs) directed against KRAS mutant CTX-resistant cancer cells. CPT was encapsulated within poly(lactic-co-glycolic acid) (PLGA) NPs using the solvent evaporation method. CTX conjugation improved NP binding and delivery of CPT to CTX-resistant cancer cell lines. CTX successfully targeted CPT-loaded NPs to mutant KRAS PANC-1 tumours in vivo and reduced tumour growth. This study highlights that CTX can be repurposed as a targeting agent against CTX-resistant cancers and that antibody repositioning may be applicable to other antibodies restricted by resistance.

In situ condensation of an anti-cancer drug into fibrin gel enabling effective inhibition of tumor cell growth

We show herein the highly effective inhibition of tumor cell growth using a gel consisting of a fibrin polymer formed with the in situ condensation of a camptothecin (CPT) derivative as an anti-cancer drug, which is efficiently conveyed with a carrier aptamer from a solution to the gel in a phenomenon, called selective oligonucleotide entrapment in fibrin polymers (SOEF).

PEG-Derivatized Dual-Functional Nanomicelles for Improved Cancer Therapy

Polymeric micelles have attracted considerable attention for effective delivery of poorly water-soluble cancer drugs. Polyethylene glycol (PEG), which has been approved for human use by the US Food and Drug Administration, is the most commonly used hydrophilic component of polymeric micelles because it is biocompatible and biodegradable. One disadvantage of traditional polymeric micelles is that they include a large amount of inert carrier materials, which do not contribute to therapeutic activity but increase cost and toxicity risk. A better alternative may be "dual-functional" micellar carriers, in which the hydrophobic carrier material (conjugated to PEG) has intrinsic therapeutic activity that complements, or even synergizes with, the antitumor activity of the drug cargo. This review summarizes recent progress in the development of PEG-derivatized dual-functional nanomicelles and surveys the evidence of their feasibility and promise for cancer therapy.

Role of synergy and immunostimulation in design of chemotherapy combinations: An analysis of doxorubicin and camptothecin

Combination chemotherapy is often employed to improve therapeutic efficacies of drugs. However, traditional combination regimens often utilize drugs at or near-their maximum tolerated doses (MTDs), elevating the risk of dose-related toxicity and impeding their clinical success. Further, high doses of adjuvant or neoadjuvant chemotherapies can cause myeloablation, which compromises the immune response and hinders the efficacy of chemotherapy as well as accompanying treatments such as immunotherapy. Clinical outcomes can be improved if chemotherapy combinations are designed to reduce the overall doses without compromising their therapeutic efficacy. To this end, we investigated a combination of camptothecin (CPT) with doxorubicin (DOX) as a low-dose treatment option for breast cancer. DOX-CPT combinations were synergistic in several breast cancer cell lines in vitro and one particular ratio displayed extremely high synergy on human triple negative breast cancer cells (MDA-MB-231). This combination led to excellent long-term survival of mice bearing MDA-MB-231 tumors at doses roughly five-fold lower than the reported MTD values of its constituent drugs. Impact of low dose DOX-CPT treatment on local tumor immune environment was assessed in immunocompetent mice bearing breast cancer (4T1) tumors. The combination was not only superior in inhibiting the disease progression compared to individual drugs, but it also generated a more favorable antitumor immunogenic response. Engineering DOX and CPT ratios to manifest synergy enables treatment at doses much lower than their MTDs, which could ultimately facilitate their translation into the clinic as a promising combination for breast cancer treatment.

Position-Selective Synthesis and Biological Evaluation of Four Isomeric A-Ring Amino Derivatives of the Alkaloid Luotonin A

Following two orthogonal synthetic routes, a series of all four possible A-ring amino derivatives of the natural product Luotonin A (a known Topoisomerase I inhibitor) was synthesized. In both strategies, intramolecular cycloaddition reactions are the key step. The target compounds were obtained in good yields by mild catalytic transfer hydrogenation of the corresponding nitro precursors. In-vitro evaluation of the antiproliferative activity towards human tumor cell lines revealed the 4-amino compound (5b) to be the most effective agent, showing an interesting profile of cytotoxic activity. Among other effects, a significant G2/M cell cycle arrest was observed for this compound, suggesting that either Topoisomerase I is not the only biological target, or that some atypical mechanism is responsible for inhibition of this enzyme.

Graphene oxide nanocells for impairing topoisomerase and DNA in cancer cells

We have engineered graphene oxide based nanocell to target DNA topoisomerases and nuclear DNA in cancer cells to induce apoptosis.

A reversible decomposition approach for the formation of injectable, excipient-free, self-assembling nanocrystals

A chemical procedure to generate excipient-free SN38 nanocrystals with greater efficacy and less toxicity than CPT-11.

Cytoprotective and genotoxic effects of vitamins K1 and B1 on irinotecan in vitro

Cultured human lymphocytes were treated with vitamins K₁ and B₁, potential anticancer agents, either alone or in combination with irinotecan, a semisynthetic analogue of camptothecin. The frequency of sister chromatid exchanges (SCEs) was measured as an indicator of genotoxicity and the proliferation rate index (PRI) and mitotic index (MI) was measured as indicators of cytostatic effect. Vitamin K₁ alone did not induce SCEs at the concentrations tested and combined with irinotecan does not increase SCE rates induced by irinotecan alone. Vitamin B₁ significantly increased SCEs and, in combination with irinotecan, increased rates further (p < 0.05). Vitamin K₁ decreased PRI and MI in combination with irinotecan, there were further increases in MI. At a low concentration, vitamin B₁ reduced the levels of SCE and increased PRI induced by irinotecan. The use of these vitamins in combination with antitumor agents might reduce clinical side effects of the antineoplastics.

Ethyl violet-bovine serum albumin fluorescent protein nanovessels target to lysosomes and mitochondria

AIM

Organelles are essential in maintaining homeostasis of mammalian cells. Monitoring the morphology and dynamics of organelles is of significance in cell state determination and disease diagnosis.

MATERIALS & METHODS

We describe here a new material called ethyl violet-bovine serum albumin fluorescent protein nanovessel (EV-BSA FPN). Upon heating, BSA was denatured to form higher polyhedral structures, which was prone to EV binding. These dye-protein hybrid materials were red fluorescence emissive upon excitation.

RESULTS

EV-BSA FPNs can be readily internalized by mammalian cells and dual localized in lysosomes and mitochondria. Besides, EV-BSA FPN can serve as carriers and efficiently deliver drug into cells.

CONCLUSION

EV-BSA FPNs can be dual function fluorescent vessels for both dual-organelle imaging and drug delivery.

Synthesis, Experimental and Density Functional Theory (DFT) Studies on Solubility of Camptothecin Derivatives

Two camptothecin derivatives, 10-cyclohexyl-7-methyl-20(S)-camptothecin and 7-methyl-10-morpholino-20(S)-camptothecin, were synthesized and their differences in solubility were investigated using four chosen solvent systems. Based on our results, 10-cyclohexyl-7-methyl-20(S)-camptothecin exhibited higher solubilities than 7-methyl-10-morpholino-20(S)-camptothecin in polar aprotic solvents. However, these two camptothecin derivatives did not exhibit apparent differences in solubility between 5% dimethyl sulfoxide (DMSO)/95% normal saline co-solvent system and 5% dimethylacetamide (DMAC)/95% normal saline co-solvent system. To rationalize their differences in solubility, we also tried to perform a DFT-B3LYP study to investigate their interaction with one water molecule.

Nanotechnology for Treatment of Glioblastoma Multiforme

Glioblastoma multiforme (GBM), a grade IV astrocytoma as defined by the World Health Organization (WHO) criteria, is the most common primary central nervous system tumor in adults. After treatment with the current standard of care consisting of surgical resection, concurrent temozolomide (TMZ), and radiation, the median survival is only 15 months. The limited and less-effective treatment options for these highly aggressive GBMs call for the development of new techniques and the improvement of existing technologies. Nanotechnology has shown promise in treating this disease, and some nanomaterials have demonstrated the ability to cross the blood–brain barrier (BBB) and remain in GBM tissues. Although the retention of nanoparticles (NPs) in GBM tissue is necessary to elicit an antitumor response, the delivery of the NP needs to be enhanced. Current research in nanotechnology is directed at increasing the active targeting of GBM tissue not only for the aid of chemotherapeutic drug delivery but also for imaging studies. This review is aimed at describing advancements in increasing nanotechnology specificity to GBM tissue.

Exploring the effect of vitamin E in cancer chemotherapy-A biochemical and biophysical insight

Many oncologists contend that patient undergoing chemotherapy must avoid antioxidant supplementation as it may interfere with the activity of the drug. In the present investigation, we have explored the influence of vitamin E, a well-known antioxidant on Camptothecin (CPT), a potent anti-cancer drug induced cell apoptosis and death of cervical cancer cells. HeLa cells were treated with different concentrations of CPT in presence and absence of 100 μm vitamin E. Treated cells were subjected to cytotoxicity studies, catalase assay, DNA fragmentation assay, clonogenic assay and flow cytometry based apoptosis detection. Also, Raman spectroscopy a label free technique which provides global information, in conjunction with multivariate tools like PCA, PCLDA and FDA, was investigated to explore vitamin E supplementation induced alterations. Our data based on biochemical and biophysical experimental analysis reveals that CPT causes DNA damage along with protein and lipid alteration culminating in cell death. Importantly, Raman spectroscopic analysis could uniquely differentiate the cluster of control and vitamin E control from CPT and CPT + Vit E treated cells. We conclusively prove that presence of vitamin E at 100 μM concentration shows promising antioxidant activity and displays no modulatory role on CPT induced effect, thereby causing no possible hindrance with the efficacy of the drug. Vitamin E may prove beneficial to alleviate chemotherapy associated side effects in patients during clinical settings which may open the doors further for subsequent exploration in in vivo preclinical studies.

Evaluation of Nitrobenzyl Derivatives of Camptothecin as Anti-Cancer Agents and Potential Hypoxia Targeting Prodrugs

As part of our initial efforts into developing a tumor-targeting therapy, C-10 substituted derivatives of a camptothecin analog (SN-38) have been synthesized (2-, 3- and 4-nitrobenzyl) for use as potential hypoxia-activated prodrugs and evaluated for their cytotoxicity, topoisomerase I inhibition and electrochemical (reductive) properties. All three derivatives were found to possess reduced toxicity towards human leukemia K562 cells compared to SN-38, validating a condition for prodrug action. Using an MTS assay, IC₅₀'s were found to be 3.0, 25.9, 12.2 and 58.0 nM for SN-38, 2-nitro-, 3-nitro- and 4-nitrobenzyl-C₁₀-substituted-SN-38, respectively, representing an 8-, 4- and 19-fold decrease in cytotoxicity. Using a topoisomerase I assay, one of the analogs (4-nitrobenzyl) was shown to inhibit the ability of this enzyme to relax supercoiled pBR322 DNA, at a similar concentration to the clinically-approved active metabolite SN-38. Cyclic voltammetry detailed the reductive nature of the analogs, and was used to infer the potential of these compounds to serve as hypoxia-targeting prodrugs. The electrochemical results also validated the quasi-reversible nature of the first reduction step, and served as a proof-of-principle that hypoxia-targeting prodrugs of SN-38 can participate in a redox-futile cycle, the proposed mechanism of activation and targeting. Chemical reduction of the 4-nitrobenzyl analog led to the formation/release of SN-38 and validated the prodrug ability of the C-10 substituted derivative.

Copper-Catalyzed Formal [4+2] Cycloaddition of Enoldiazoimides with Sulfur Ylides

Enoldiazoimides, a new subclass of enoldiazo compounds, generate enol-substituted carbonyl ylides whose reactions with sulfur ylides enable an unprecedented formal [4+2] cycloaddition. The resulting multifunctionalized indolizidinones, which incorporate sulfur, are formed in good yields under mild reaction conditions. The uniqueness of this transformation stems from the role of the silyl-protected enol, since the corresponding acetyldiazoimide failed to provide any cross-products in metal-catalyzed reactions with sulfur ylides. This copper-catalyzed cycloaddition is initiated with the generation of enol-substituted carbonyl ylides and sulfur ylides from enoldiazoimides and sulfonium salts, respectively, and proceeds through stepwise six-membered ring formation, C-O and C-S bond cleavage, and silyl and acetyl group migration.

Randomized Open Label Phase III Trial of Irinotecan Plus Capecitabine versus Capecitabine Monotherapy in Patients with Metastatic Breast Cancer Previously Treated with Anthracycline and Taxane: PROCEED Trial (KCSG BR 11-01)

Purpose

We investigated whether irinotecan plus capecitabine improved progression-free survival (PFS) compared with capecitabine alone in patients with human epidermal growth factor 2 (HER2) negative and anthracycline and taxane pretreated metastatic breast cancer (MBC).

Materials and Methods

A total of 221 patients were randomly assigned to irinotecan (80 mg/m², days 1 and 8) and capecitabine (1,000 mg/m² twice a day, days 1-14) or capecitabine alone (1,250 mg/m² twice a day, days 1-14) every 3 weeks. The primary endpoint was PFS.

Results

There was no significant difference in PFS between the combination and monotherapy arm (median, 6.4 months vs. 4.7 months; hazard ratio [HR], 0.84; 95% confidence interval [CI], 0.63 to 1.11; p=0.84). In patients with triple-negative breast cancer (TNBC, n=90), the combination significantly improved PFS (median, 4.7 months vs. 2.5 months; HR, 0.58; 95% CI, 0.37 to 0.91; p=0.02). Objective response rate was numerically higher in the combination arm, though it failed to reach statistical significance (44.4% vs. 33.3%, p=0.30). Overall survival did not differ between arms (median, 20.4 months vs. 24.0 months; p=0.63). While grade 3 or 4 neutropenia was more common in the combination arm (39.6% vs. 9.0%), hand-foot syndrome was more often observed in capecitabine arm. Quality of life measurements in global health status was similar. However, patients in the combination arm showed significantly worse symptom scales especially in nausea/vomiting and diarrhea.

Conclusion

Irinotecan plus capecitabine did not prove clinically superior to single-agent capecitabine in anthracycline- and taxane-pretreated HER2 negative MBC patients. Toxicity profiles of the two groups differed but were manageable. The role of added irinotecan in patients with TNBC remains to be elucidated.

The Forty-Sixth Euro Congress on Drug Synthesis and Analysis: Snapshot †

The 46th EuroCongress on Drug Synthesis and Analysis (ECDSA-2017) was arranged within the celebration of the 65th Anniversary of the Faculty of Pharmacy at Comenius University in Bratislava, Slovakia from 5-8 September 2017 to get together specialists in medicinal chemistry, organic synthesis, pharmaceutical analysis, screening of bioactive compounds, pharmacology and drug formulations; promote the exchange of scientific results, methods and ideas; and encourage cooperation between researchers from all over the world. The topic of the conference, "Drug Synthesis and Analysis," meant that the symposium welcomed all pharmacists and/or researchers (chemists, analysts, biologists) and students interested in scientific work dealing with investigations of biologically active compounds as potential drugs. The authors of this manuscript were plenary speakers and other participants of the symposium and members of their research teams. The following summary highlights the major points/topics of the meeting.

Camptothecin and its analog SN-38, the active metabolite of irinotecan, inhibit binding of the transcriptional regulator and oncoprotein FUBP1 to its DNA target sequence FUSE

The transcriptional regulator FUSE Binding Protein 1 (FUBP1) is overexpressed in more than 80% of all human hepatocellular carcinomas (HCCs) and other solid tumor entities including prostate and colorectal carcinoma. FUBP1 expression is required for HCC tumor cell expansion, and it functions as an important pro-proliferative and anti-apoptotic oncoprotein that binds to the single-stranded DNA sequence FUSE to regulate the transcription of a variety of target genes. In this study, we screened an FDA-approved drug library and discovered that the Topoisomerase I (TOP1) inhibitor camptothecin (CPT) and its derivative 7-ethyl-10-hydroxycamptothecin (SN-38), the active irinotecan metabolite that is used in the clinics in combination with other chemotherapeutics to treat carcinoma, inhibit FUBP1 activity. Both molecules prevent in vitro the binding of FUBP1 to its single-stranded target DNA FUSE, and they induce deregulation of FUBP1 target genes in HCC cells. Our results suggest the interference with the FUBP1/FUSE interaction as a further molecular mechanism that, in addition to the inactivation of TOP1, may contribute to the therapeutic potential of CPT/SN-38. Targeting of FUBP1 in HCC therapy with SN-38/irinotecan could be a particularly interesting option because of the high FUBP1 levels in HCC cells and their dependency on FUBP1 expression.

Development and evaluation of camptothecin loaded polymer stabilized nanoemulsion: Targeting potential in 4T1-breast tumour xenograft model

Targeted delivery of anticancer agents is poised to improve cancer therapy, for which polymers can serve as targeting ligands or nanocarriers for chemotherapeutic agents. In this study, we have developed and evaluated the efficacy of a camptothecin (CPT)-loaded polymer stabilized nanoemulsion (PSNE) for the passive targeted delivery to breast cancer. Based on the pseudo-ternary phase diagrams, PSNEs were developed using capmul MCM:poloxamer 407 (4:1), solutol HS 15:simulsol P23 (1:2) and water. CPT polymer mixture was developed by solvent evaporation technique. The PSNEs were characterized for droplet size distribution, plasma protein adsorption, drug release, in-vivo targeting potential, hemolytic potential, cytotoxicity, genotoxicity, in-vivo biodistribution and CPT lactone ring stability. The developed PSNEs showed uniform droplet distribution, extended drug release (76.59±6.12% at 24h), acceptable hemolytic potential, significant cytotoxicity (IC₅₀=176±4.3ng/mL) and genotoxicity against MCF-7 cancer cells but low DNA damage potential in human peripheral blood lymphocytes. The efficiency of PSNEs for the targeted delivery of CPT into the tumour regions was documented in 4T1-breast tumour xenografted BALB/c mice. In-vivo biodistribution study shows that 7105.84±568.46ng/g of CPT was passively targeted from PSNE to breast cancer tissue. About 80% of the lactone form was stable for 24h. Taken together, our study provides a promising strategy for developing PSNE-targeted drug delivery system for the breast cancer therapy.

A Facile Oxidative Opening of the C-Ring in Luotonin A and Derivatives

An oxidative ring opening reaction of the central ring C in the alkaloid Luotonin A and two of its derivatives was found to occur upon heating with an excess amine and potassium carbonate in dimethylsulfoxide (DMSO) solution in the presence of air oxygen. The structure of the novel amide-type products was elucidated and a possible mechanism for this reaction is proposed. Four of the new compounds show moderate in vitro anticancer activity towards human colon adenocarcinoma cells.

Peptide grafted and self-assembled poly(γ-glutamic acid)-phenylalanine nanoparticles targeting camptothecin to glioma

Aim: To synthesize cRGDfK peptide conjugated poly(γ-glutamic acid)-phenylalanine nanoparticles to improve the therapeutic efficacy of camptothecin (CPT) against glioblastoma multiforme. Methods: Peptide-conjugated, drug-loaded nanoparticles (cRGDfK-conjugated camptothecin-loaded PGA–PA nanoparticles [RCPN]) were prepared and physico-chemically characterized using different techniques. Nanoparticles were evaluated for in vitro anticancer activity, cellular uptake, induction of apoptosis and wound healing cell migration against U87MG human glioblastoma cells. Results: RCPN, with a particle size of <100 nm and 65% CPT encapsulation efficiency, exhibited a dose- and time-dependent cytotoxicity to glioblastoma cells. Compared with native CPT or unconjugated nanoparticles, RCPN induced apoptosis, increased reactive oxygen species generation and inhibited U87MG cell migration. Conclusion: cRGDfK-mediated and amphiphilic copolymer-based nanomedicines represent a new approach for improved delivery of anticancer drugs to and treatment of glioblastoma multiforme.

Optimization of liposomal topotecan for use in treating neuroblastoma

The purpose of this work was to develop an optimized liposomal formulation of topotecan for use in the treatment of patients with neuroblastoma. Drug exposure time studies were used to determine that topotecan (Hycamtin) exhibited great cytotoxic activity against SK-N-SH, IMR-32 and LAN-1 neuroblastoma human cell lines. Sphingomyelin (SM)/cholesterol (Chol) and 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC)/Chol liposomes were prepared using extrusion methods and then loaded with topotecan by pH gradient and copper-drug complexation. In vitro studies showed that SM/Chol liposomes retained topotecan significantly better than DSPC/Chol liposomes. Decreasing the drug-to-lipid ratio engendered significant increases in drug retention. Dose-range finding studies on NRG mice indicated that an optimized SM/Chol liposomal formulation of topotecan prepared with a final drug-to-lipid ratio of 0.025 (mol: mol) was better tolerated than the previously described DSPC/Chol topotecan formulation. Pharmacokinetic studies showed that the optimized SM/Chol liposomal topotecan exhibited a 10-fold increase in plasma half-life and a 1000-fold increase in AUC0-24 h when compared with Hycamtin administered at equivalent doses (5 mg/kg). In contrast to the great extension in exposure time, SM/Chol liposomal topotecan increased the life span of mice with established LAN-1 neuroblastoma tumors only modestly in a subcutaneous and systemic model. The extension in exposure time may still not be sufficient and the formulation may require further optimization. In the future, liposomal topotecan will be assessed in combination with high-dose radiotherapy such as 131 I-metaiodobenzylguanidine, and immunotherapy treatment modalities currently used in neuroblastoma therapy.

Evaluating the Potential for Delivery of Irinotecan via the Buccal Route: Physicochemical Characterization and In Vitro Permeation Assessment Across Porcine Buccal Mucosa

Irinotecan (CPT-11) is used to treat advanced colorectal cancer as an intravenous therapy. Depending on pH, CPT-11 exists in either a lactone (active) or carboxylate (inactive) form, or both. In this investigation, the feasibility for systemic delivery of CPT-11 through the buccal route was evaluated. Permeation of CPT-11 across porcine buccal mucosa was studied in vitro using side-by-side flow through diffusion cells at 37°C. Experiments were performed over a pH range from 4 to 9, and the permeability of both the lactone and carboxylate forms of CPT-11 was measured. CPT-11 steady state flux was determined over a range of donor concentrations at pH 4 (0.5, 1, 5, 10, 15, 20 mg/ml) and pH 6.8 (0.5, 5, 10 mg/ml). Steady state flux increased linearly with increasing donor concentration of CPT-11 at pH 4 (r ² = 0.9935) and at pH 6.8 (r ² = 0.9886). CPT-11 permeability was independent of pH, although the distribution coefficient increased with increasing pH. Estimates of permeability for the lactone and carboxylate forms were 4.16 × 10^-5 cm/s and 2.6 × 10^-5 cm/s, respectively. These calculated permeability values were in agreement with the in vitro experimental data. Overall, CPT-11 was found to permeate through porcine buccal mucosa via passive diffusion. CPT-11 permeability was independent of pH, suggesting that the compound was transported mainly via a paracellular route. Overall, the results of this research suggest that the buccal route is a potential extravascular mode of delivery for CPT-11.

The long story of camptothecin: From traditional medicine to drugs

20-(S)-Camptothecin (CPT) is a natural alkaloid extracted from the bark of Camptotheca acuminata (Chinese happy tree). It acts as a DNA topoisomerase 1 poison with an interesting antitumor activity and its use is limited by low stability and solubility and unpredictable drug-drug interactions. Since the late 20th century, it has been widely used in cancer therapy and, since extraction yields from plant tissues are very low, various synthetic routes have been developed to satisfy the increase in demand for CPT. Moreover, SAR studies have allowed for the development of more potent CPT analogues topotecan and irinotecan. Unfortunately, resistance has already occurred in several tumour lines. Additional studies are needed to better understand the relationship between substituents and resistance, its clinical relevance and the impact of related gene polymorphism. One of the latest research approaches focuses on modifying the delivery mode to improve tumour cell uptake and reduce toxicity.

Integrating a novel SN38 prodrug into the PEGylated liposomal system as a robust platform for efficient cancer therapy in solid tumors

Liposomal nanoassemblies have been used extensively as carriers for the delivery of both lipophilic and hydrophilic drugs. They represent a mature, versatile technology with considerable potential for improving the pharmacokinetics of drugs. However, the formulation of many chemotherapeutics into liposome systems has posed a significant challenge due to their incompatible physicochemical properties, as was the case with camptothecin-based chemotherapeutics. Here, we present a rational paradigm of potent chemotherapeutics that were reconstructed and subsequently integrated into liposomal nanoassemblies. Using SN38 (7-ethyl-10-hydroxy camptothecin) as a model drug, a lipophilic prodrug 1 (designated as LA-SN38) was constructed by tethering the linoleic acid (LA) moiety via esterification, which was further facilitated to form liposomal nanoparticles (LipoNP) through supramolecular nanoassembly. The resulting 1-loaded LipoNP exhibited sustained drug release kinetics and decreased cellular uptake by macrophage cells. Uptake by tumor cells was enhanced relative to our previous supramolecular nanoparticles (SNP 1), which were derived from the self-assembling prodrug 1. Notably, LipoNP outperformed SNP 1 in terms of pharmacokinetics and in vivo therapeutic efficacy in both human BEL-7402 hepatocellular carcinoma (HCC) and HCT-116 colorectal cancer-derived xenograft mouse models. These results were likely due to the improved systemic circulation and preferential accumulation of nanodrugs in tumors. Hence, our results suggest that the combination of liposomal delivery platforms with rational prodrug engineering may emerge as a promising approach for the effective and safe delivery of anticancer chemotherapeutics.

Human topoisomerase IB is a target of a thiosemicarbazone copper(II) complex

The human topoisomerase IB inhibition and the antiproliferative activity of 3-(4-bromophenyl)-1-pyridin-2-ylprop-2-en-1-one thiosemicarbazone HPyCT4BrPh alone and its copper(II) complex [Cu(PyCT4BrPh)Cl] was investigated. [Cu(PyCT4BrPh)Cl] inhibits both the DNA cleavage and religation step of the enzyme, whilst the ligand alone does not display any effect. In addition we show that coordination to copper(II) improves the cytotoxicity of HPyCT4BrPh against THP-1 leukemia and MCF-7 breast cancer cells. The data indicate that the copper(II) thiosemicarbazone complex may hit human topoisomerase IB and that metal coordination can be useful to improve cytotoxicity of this versatile class of compounds.

Dissociation of NSC606985 induces atypical ER-stress and cell death in prostate cancer cells

Castration-resistant prostate cancer (CRPC) is a major cause of prostate cancer (Pca) death. Chemotherapy is able to improve the survival of CRPC patients. We previously found that NSC606985 (NSC), a highly water-soluble camptothecin analog, induced cell death in Pca cells via interaction with topoisomerase 1 and activation of the mitochondrial apoptotic pathway. To further elucidate the role of NSC, we studied the effect of NSC on ER-stress and its association with NSC-induced cell death in Pca cells. NSC produced a time- and dose-dependent induction of GRP78, CHOP and XBP1s mRNA, and CHOP protein expression in Pca cells including DU145, indicating an activation of ER-stress. However, unlike conventional ER-stress in which GRP78 protein is increased, NSC produced a time- and dose-dependent U-shape change in GRP78 protein in DU145 cells. The NSC-induced decrease in GRP78 protein was blocked by protease inhibitors, N-acetyl-L-leucyl-L-leucylnorleucinal (ALLN), a lysosomal protease inhibitor, and epoxomicin (EPO), a ubiquitin-protease inhibitor. ALLN, but not EPO, also partially inhibited NSC-induced cell death. However, both 4-PBA and TUDCA, two chemical chaperons that effectively reduced tunicamycin-induced ER-stress, failed to attenuate NSC-induced GRP78, CHOP and XBP1s mRNA expression and cell death. Moreover, knockdown of NSC induction of CHOP expression using a specific siRNA had no effect on NSC-induced cytochrome c release and NSC-induced cell death. These results suggest that NSC produced an atypical ER-stress that is dissociated from NSC-induced activation of the mitochondrial apoptotic pathway and NSC-induced cell death in DU145 prostate cancer cells.

Characterization of DNA topoisomerase I in three SN-38 resistant human colon cancer cell lines reveals a new pair of resistance-associated mutations

BACKGROUND

DNA topoisomerase I (Top1) is a DNA unwinding protein and the specific target of the camptothecin class of chemotherapeutic drugs. One of these, irinotecan, acting through its active metabolite SN-38, is used in the treatment of metastatic colorectal cancer. However, resistance to irinotecan represents a major clinical problem. Since molecular alterations in Top1 may result in resistance to irinotecan, we characterized Top1 in three human colon cancer cell lines with acquired resistance to SN-38.

METHODS

Three SN-38 resistant (20-67 fold increased resistance) cell lines were generated and compared to wild-type parental cells with regards to: TOP1 gene copy number and gene sequence, Top1 expression (mRNA and protein), Top1 enzymatic activity in the absence and presence of drug, and Top1-DNA cleavage complexes in drug treated cells. TOP1 mutations were validated by PCR using mutant specific primers. Furthermore, cross-resistance to two indenoisoquinoline Top1-targeting drugs (NSC 725776 and NSC 743400) and two Top2-targeting drugs (epirubicin and etoposide) was investigated.

RESULTS

Two of three SN-38 resistant cell lines carried TOP1 gene copy number aberrations: A TOP1 gene copy gain and a loss of chromosome 20, respectively. One resistant cell line harbored a pair of yet unreported TOP1 mutations (R364K and G717R) in close proximity to the drug binding site. Mutant TOP1 was expressed at a markedly higher level than wild-type TOP1. None or very small reductions were observed in Top1 expression or Top1 activity in the absence of drug. In all three SN-38 resistant cell lines Top1 activity was maintained in the presence of high concentrations of SN-38. None or only partial cross-resistance were observed for etoposide and epirubicin, respectively. SN-38 resistant cells with wild-type TOP1 remained sensitive to NSC 743400, while cells with mutant TOP1 was fully cross-resistant to both indenoisoquinolines. Top1-DNA cleavage complex formation following drug treatment supported the other findings.

CONCLUSIONS

This study adds to the growing knowledge about resistance mechanisms for Top1-targeting chemotherapeutic drugs. Importantly, two yet unreported TOP1 mutations were identified, and it was underlined that cross-resistance to the new indenoisoquinoline drugs depends on the specific underlying molecular mechanism of resistance to SN-38.

Mesenchymal stem cells exhibit resistance to topoisomerase inhibition

BACKGROUND

Inhibition of cellular topoisomerases has been established as an effective way of treating certain cancers, albeit with often high levels of toxicity to the bone marrow. While the involvement of mesenchymal stem cells (MSCs) in bone marrow homeostasis and regeneration has been well established, the effects of topoisomerase-inhibiting anticancer agents remain largely unknown.

MATERIALS AND METHODS

Human bone marrow MSCs were treated with topoisomerase I inhibitor irinotecan or topoisomerase II inhibitor etoposide, and survival and apoptosis levels were measured. The influence of topoisomerase inhibition on cellular morphology, adhesion and migration potential and the ability to differentiate was assessed. Additionally, the role of individual DNA double-strand break repair pathways in MSCs was investigated as a potential cellular mechanism of resistance to topoisomerase inhibitors.

RESULTS

Human bone marrow MSCs were found relatively resistant to topoisomerase I and II inhibitors and show survival levels comparable to these of differentiated fibroblasts. Treatment with irinotecan or etoposide did not significantly influence cellular adhesion, migratory ability, surface marker expression or induction of apoptosis in human MSCs. The ability to differentiate was found preserved in MSCs after exposure to high doses of irinotecan or etoposide. MSCs were able to efficiently repair DNA double-strand breaks induced by topoisomerase inhibitors both by non-homologous end joining and homologous recombination pathways.

CONCLUSION

Our data demonstrate a topoisomerase-resistant phenotype of human MSCs that may at least in part be due to the stem cells' ability to efficiently remove DNA damage caused by these anticancer agents. The observed resistance of MSCs warrants further investigation of these cells as a potential therapeutic option for treating topoisomerase inhibitor-induced bone marrow damage.

Synergistic Effects of Simvastatin and Irinotecan against Colon Cancer Cells with or without Irinotecan Resistance

Aims. We here investigated whether the combination of simvastatin and irinotecan could induce the synergistic effect on colon cancer cells with or without resistance to irinotecan. Methods. We investigated cell proliferation assay and assessed cell death detection ELISA and caspase-3 activity assay of various concentrations of simvastatin and irinotecan to evaluate the efficacy of drug combination on colon cancer cells with or without irinotecan resistance. Results. The IC₅₀ values of simvastatin alone and irinotecan alone were 115.4 ± 0.14 μM (r = 0.98) and 62.5 ± 0.18 μM (r = 0.98) in HT-29 cells without resistance to irinotecan. The IC₅₀ values of these two drugs were 221.9 ± 0.22 μM (r = 0.98) and 195.9 ± 0.16 μM (r = 0.99), respectively, in HT-29 cell with resistance to irinotecan. The results of combinations of the various concentrations of two drugs showed that combined treatment with irinotecan and simvastatin more efficiently suppressed cell proliferation of HT-29 cells even with resistance to irinotecan as well as without resistance. Furthermore, the combination of simvastatin and irinotecan at 2 : 1 molar ratio showed the best synergistic interaction. Conclusion. Simvastatin could act synergistically with irinotecan to overcome irinotecan resistance of colon cancer.

Hyaluronic acid for anticancer drug and nucleic acid delivery

Hyaluronic acid (HA) is widely used in anticancer drug delivery, since it is biocompatible, biodegradable, non-toxic, and non-immunogenic; moreover, HA receptors are overexpressed on many tumor cells. Exploiting this ligand-receptor interaction, the use of HA is now a rapidly-growing platform for targeting CD44-overexpressing cells, to improve anticancer therapies. The rationale underlying approaches, chemical strategies, and recent advances in the use of HA to design drug carriers for delivering anticancer agents, are reviewed. Comprehensive descriptions are given of HA-based drug conjugates, particulate carriers (micelles, liposomes, nanoparticles, microparticles), inorganic nanostructures, and hydrogels, with particular emphasis on reports of preclinical/clinical results.

Molecular Genetics External Quality Assessment Pilot Scheme for Irinotecan-Related UGT1A1 Genotyping in China

Irinotecan is widely used in the treatment of solid tumors, especially in colorectal cancer and lung cancer. Molecular testing for UGT1A1 genotyping is increasingly required in China for optimum irinotecan administration. In order to determine the performance of laboratories with regard to the whole testing process for UGT1A1 to ensure the consistency and accuracy of the test results, the National Center for Clinical Laboratories conducted an external quality assessment program for UGT1A1*28 genotyping in 2015. The panel, which comprised of four known mutational samples and six wild-type samples, was distributed to 45 laboratories that test for the presence of UGT1A1*28 polymorphisms. Participating laboratories were allowed to perform polymorphism analysis by using their routine methods. The accuracy of the genotyping and reporting of results was analyzed. Other information from the individual laboratories, including the number of samples tested each month, accreditation/certification status, and test methodology, was reviewed. Forty-four of the 45 participants reported the correct results for all samples. There was only one genotyping error, with a corresponding analytical sensitivity of 99.44% (179/180 challenges; 95% confidence interval: 96.94-99.99%) and an analytical specificity of 100% (270/270 challenges; 95% confidence interval: 98.64-100%). Both commercial kits and laboratory development tests were commonly used by the laboratories, and pyrosequencing was the main methodology used (n = 26, 57.8%). The style of the written reports showed large variation, and many reports showed a shortage of information. In summary, the first UGT1A1 genotyping external quality assessment result demonstrated that UGT1A1 genotype analysis of good quality was performed in the majority of pharmacogenetic testing centers that were investigated. However, greater education on the reporting of UGT1A1 genetic testing results is needed.

Selective topotecan delivery to cancer cells by targeted pH-sensitive mesoporous silica nanoparticles

Topotecan targeted pH-sensitive delivery system based in mesoporous silica nanoparticles coated with a multifunctional biopolymer coating for cancer therapy.

The distinctive cellular responses to DNA strand breaks caused by a DNA topoisomerase I poison in conjunction with DNA replication and RNA transcription

Camptothecin (CPT) inhibits DNA topoisomerase I (Top1) through a non-catalytic mechanism that stabilizes the Top1-DNA cleavage complex (Top1cc) and blocks the DNA re-ligation step, resulting in the accumulation in the genome of DNA single-strand breaks (SSBs), which are converted to secondary strand breaks when they collide with the DNA replication and RNA transcription machinery. DNA strand breaks mediated by replication, which have one DNA end, are distinct in repair from the DNA double-strand breaks (DSBs) that have two ends and are caused by ionizing radiation and other agents. In contrast to two-ended DSBs, such one-ended DSBs are preferentially repaired through the homologous recombination pathway. Conversely, the repair of one-ended DSBs by the non-homologous end-joining pathway is harmful for cells and leads to cell death. The choice of repair pathway has a crucial impact on cell fate and influences the efficacy of anticancer drugs such as CPT derivatives. In addition to replication-mediated one-ended DSBs, transcription also generates DNA strand breaks upon collision with the Top1cc. Some reports suggest that transcription-mediated DNA strand breaks correlate with neurodegenerative diseases. However, the details of the repair mechanisms of, and cellular responses to, transcription-mediated DNA strand breaks still remain unclear. In this review, combining our recent results and those of previous reports, we introduce and discuss the responses to CPT-induced DNA damage mediated by DNA replication and RNA transcription.

DOSY NMR and MALDI-TOF evidence of covalent binding the DNA duplex by trimethylammonium salts of topotecan upon near UV irradiation

Using DOSY NMR and MALDI-TOF MS techniques, we present evidence that quaternary trimethylammonium salts of topotecan, [TPT-NMe3 ](+) X(-) (X = CF3SO3, HCOO), bind covalently the natural DNA oligomer upon near UV irradiation in water under physiological conditions. It is shown that formate salt is very reactive at pH 7 and requires short irradiation time. This weak irradiation at 365 nm paves the way for a new application of TPT derivatives in clinical use, which can dramatically increase the therapeutic effects of a medicine.

Functional-segregated coumarin-containing telodendrimer nanocarriers for efficient delivery of SN-38 for colon cancer treatment

Four coumarin-containing telodendrimers (denoted as P-I, P-II, P-III and P-IV) were designed and synthesized to self-assemble into the corresponding nanoparticles. Of those, two nanoparticles (P-II and P-IV micelles) were screened and selected for targeted drug delivery of 7-ethyl-10-hydroxy camptothecin (SN-38), a prominent and efficacious anticancer agent, for the treatment of colon cancers. The nanoparticle encapsulation significantly increased the solubility of SN-38 in aqueous solution. Dynamic light scattering (DLS) showed the size of these SN-38 nanoparticles to be around 50 nm, and rod-shaped micelles were observed using transmission electron microscopy (TEM). These two novel nanoformulations of SN-38/P-II and SN-38/P-IV were found to exhibit similar in vitro cytotoxic activity against colon cancer cells as the free drug (SN-38 in DMSO) and were 500-fold more potent than irinotecan (a prodrug of SN-38). In addition, near infrared fluorescent (NIRF) optical imaging was utilized to monitor the tumor targeted delivery of SN-38/NPs via co-loading a NIRF dye. It was demonstrated that these NPs preferentially accumulated in tumors when compared to healthy tissue. A pharmacokinetics study showed that SN-38 micelle formulations had a longer circulating time in blood than irinotecan. Furthermore, SN-38 loaded nanoformulations exhibit superior anti-tumor efficacy when compared with irinotecan at equivalent SN-38 dose in HT-29 human colon cancer xenograft models.