Determinants of the cytotoxicity of irinotecan in two human colorectal tumor cell lines

New Hydrazone Derivatives Based on Pyrazolopyridothiazine Core as Cytotoxic Agents to Colon Cancers: Design, Synthesis, Biological Evaluation, and Molecular Modeling

In this research, a series of novel hydrazone derivatives based on pyrazolopyridothiazinylacetohydrazide were designed, synthesized, and evaluated for their in vitro cytotoxic potency on several human colon cancer cells (HTC116, HT-29, and LoVo). After MTT and SRB assays four of the most active derivatives: hydrazide GH and hydrazones GH7, GH8, and GH11, were chosen for further investigation. Hydrazone GH11 had the highest cytotoxic activity (IC50 values of c.a. 0.5 μM). Additionally, the impact of novel derivatives on the oxidative stress level, apoptosis induction, and modulation of inflammation in colon cancer cells was examined. In all studies, the activity of the derivatives increased in order GH < GH7 < GH8 < GH11. At the same time, most of the research was conducted on compounds combined with apple pectin (PC). The most interesting observation was that all the studied derivatives applied together with PC showed significantly higher activity than observed in the case of using PC, hydrazide, or hydrazones separately. Finally, computational chemistry methods (molecular modeling and Density Functional Theory - DFT) were used to complement the experimental studies.

Oral delivery of solid lipid nanoparticles surface decorated with hyaluronic acid and bovine serum albumin: A novel approach to treat colon cancer through active targeting

The present study aims to prepare and evaluate solid lipid nanoparticles (SLNs) loaded with irinotecan (IRN) drug and daidzein (DZN) isoflavonoid and surface coated with ligand materials such as hyaluronic acid (HA) and bovine serum albumin (BSA) with additional coating of chitosan for active targeting to receptors present on colon surface epithelium for oral targeted delivery. The optimized batch was evaluated for particle size, zeta potential exhibiting nanometric size with good entrapment efficiency. Nanoparticles were found to be spherical. FTIR and DSC revealed that all the excipients and formulation were compatabile to each other and showed better encapsulation exhibiting amorphous and crystallinity forms. In vitro drug release of SLNs confirmed that initially a burst release, followed by sustained release pattern was exhibited. Cell lines studied performed on HT-29 cells showed demonstrated that conjugated SLNs inhibited cytotoxicity at 75 μg/ml, indicating that cells were taken up through a receptor-mediated endocytosis process. Cell cycle analysis showed that cell arrest was done at 67.8 % (G0/G1 phase) and inhibited apoptosis by 56 %. Further during In vivo studies, RT-PCR study revealed downregulation of Carcinoembryonic antigen (CEA), a non-specific serum biomarker overexpressed in tumor cells and upregulation of pro-inflammatory cytokine TNF-α. Histopathological study revealed that conjugated (HA-BSA) coated with chitosan SLNs restored normal mucosa and colon architecture, depicting all mucosal layers. Hence, these conjugated SLNs may serve as a novel combination for the treatment of colon cancer.

Phase I study of intraperitoneal irinotecan combined with palliative systemic chemotherapy in patients with colorectal peritoneal metastases

BACKGROUND

Patients with colorectal peritoneal metastases who are not eligible for cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) owing to extensive peritoneal disease have a poor prognosis. It was hypothesized that these patients may benefit from the addition of intraperitoneal irinotecan to standard palliative systemic chemotherapy.

METHODS

This was a classical 3 + 3 phase I dose-escalation trial in patients with colorectal peritoneal metastases who were not eligible for CRS-HIPEC. Intraperitoneal irinotecan was administered every 2 weeks, concomitantly with systemic FOLFOX (5-fluorouracil, folinic acid, oxaliplatin)-bevacizumab. The primary objective was to determine the maximum tolerated dose and dose-limiting toxicities. Secondary objectives were to elucidate the systemic and intraperitoneal pharmacokinetics, safety profile, and efficacy.

RESULTS

Eighteen patients were treated. No dose-limiting toxicities were observed with 50 mg (4 patients) and 75 mg (9 patients) intraperitoneal irinotecan. Two dose-limiting toxicities occurred with 100 mg irinotecan among five patients. The maximum tolerated dose of intraperitoneal irinotecan was established to be 75 mg, and it was well tolerated. Intraperitoneal exposure to SN-38 (active metabolite of irinotecan) was high compared with systemic exposure (median intraperitoneal area under the curve (AUC) to systemic AUC ratio 4.6). Thirteen patients had a partial radiological response and five had stable disease. Four patients showed a complete response during post-treatment diagnostic laparoscopy. Five patients underwent salvage resection or CRS-HIPEC. Median overall survival was 23.9 months.

CONCLUSION

Administration of 75 mg intraperitoneal irinotecan concomitantly with systemic FOLFOX-bevacizumab was safe and well tolerated. Intraperitoneal SN-38 exposure was high and prolonged. As oncological outcomes were promising, intraperitoneal administration of irinotecan may be a good alternative to other, more invasive and costly treatment options. A phase II study is currently accruing.

NEDDylated Cullin 3 mediates the adaptive response to topoisomerase 1 inhibitors

DNA topoisomerase 1 (TOP11) inhibitors are mainstays of anticancer therapy. These drugs trap TOP1 on DNA, stabilizing the TOP1-cleavage complex (TOP1-cc). The accumulation of TOP1-ccs perturbs DNA replication fork progression, leading to DNA breaks and cell death. By analyzing the genomic occupancy and activity of TOP1, we show that cells adapt to treatment with multiple doses of TOP1 inhibitor by promoting the degradation of TOP1-ccs, allowing cells to better tolerate subsequent doses of TOP1 inhibitor. The E3-RING Cullin 3 ligase in complex with the BTBD1 and BTBD2 adaptor proteins promotes TOP1-cc ubiquitination and subsequent proteasomal degradation. NEDDylation of Cullin 3 activates this pathway, and inhibition of protein NEDDylation or depletion of Cullin 3 sensitizes cancer cells to TOP1 inhibitors. Collectively, our data uncover a previously unidentified NEDD8-Cullin 3 pathway involved in the adaptive response to TOP1 inhibitors, which can be targeted to improve the efficacy of TOP1 drugs in cancer therapy.

Orally delivered solid lipid nanoparticles of irinotecan coupled with chitosan surface modification to treat colon cancer: Preparation, in-vitro and in-vivo evaluations

Irinotecan-loaded solid lipid nanoparticles (IRI-SLNs) was formulated and tested for its potential activity against colon cancer. IRI-SLNs were prepared by applying the principles of DoE. Nanoparticles were further surface modified using chitosan. Characterizations such as size, poly-dispersity, surface charge, morphology, entrapment, drug release pattern, cytotoxicity were conducted. In-vivo studies in male Wistar rats were carried to ascertain distribution pattern of SLNs and their acute toxicity on various vital organs. Lastly, stability of the SLNs were evaluated. Particles had a size, polydispersity and zeta potential of 430.77 ± 8.69 nm, 0.36 ± 0.02 and -40.06 ± 0.61 mV, respectively. Entrapment of IRI was 62.24 ± 2.90% in IRI-SLNs. Sustained drug release was achieved at a colonic pH and long-term stability of NPs was seen. Cytotoxicity assay results showed that SLNs exhibited toxicity on HCT-116 cells. Biodistribution studies confirmed higher concentration of drug in the colon after surface modification. An acute toxicity study conducted for 7 days showed no severe toxic effects on major organs. Thus, we picture that the developed SLNs may benefit in delivering IRI to the tumour cells, therefore decreasing the dose and dose-associated toxicities.

Evaluation of the target-specific therapeutic potential of herbal compounds for the treatment of cancer

Cancer is among one of the most fatal diseases leading to millions of death around the globe. Chemotherapy is the most popular conventional approach for the treatment of cancer. However, this is usually associated with various side effects and puts the patients under extreme physical and mental stress. Besides, there are increasing concerns about drug resistance. Thus, to surmount these limitations, there is a need to explore some alternative treatments. Studies related to plant-derived compounds are crucial in the search for safer and more efficient treatments. Plants and their associated secondary metabolites have been a revolutionary approach in the field of cancer treatment, as they give answers to almost all the constraints faced by synthetic drugs. Various plants and associated secondary metabolites display a great prospective as cytotoxic anticancer agents due to their specific interference with validated drug targets, such as inhibitors of mitosis, topoisomerase I and II inhibitor, DNA interactive agent, protein kinase inhibitors, inhibitors of DNA synthesis. In this review, the therapeutic potential of various natural compounds and their derivatives are presented based on their molecular targets. These herbal compounds and their derivatives could provide a rich resource for novel anticancer drug development.

A Prospective Feasibility Trial to Challenge Patient-Derived Pancreatic Cancer Organoids in Predicting Treatment Response

Real-time isolation, propagation, and pharmacotyping of patient-derived pancreatic cancer organoids (PDOs) may enable treatment response prediction and personalization of pancreatic cancer (PC) therapy. In our methodology, PDOs are isolated from 54 patients with suspected or confirmed PC in the framework of a prospective feasibility trial. The drug response of single agents is determined by a viability assay. Areas under the curves (AUC) are clustered for each drug, and a prediction score is developed for combined regimens. Pharmacotyping profiles are obtained from 28 PDOs (efficacy 63.6%) after a median of 53 days (range 21-126 days). PDOs exhibit heterogeneous responses to the standard-of-care drugs, and are classified into high, intermediate, or low responder categories. Our developed prediction model allows a successful response prediction in treatment-naïve patients with an accuracy of 91.1% for first-line and 80.0% for second-line regimens, respectively. The power of prediction declines in pretreated patients (accuracy 40.0%), particularly with more than one prior line of chemotherapy. Progression-free survival (PFS) is significantly longer in previously treatment-naïve patients receiving a predicted tumor sensitive compared to a predicted tumor resistant regimen (mPFS 141 vs. 46 days; p = 0.0048). In conclusion, generation and pharmacotyping of PDOs is feasible in clinical routine and may provide substantial benefit.

Implications of ABCC4-Mediated cAMP Eflux for CRC Migration

Colorectal cancer (CRC) presents significant molecular heterogeneity. The cellular plasticity of epithelial to mesenchymal transition (EMT) is one of the key factors responsible for the heterogeneous nature of metastatic CRC. EMT is an important regulator of ATP binding cassette (ABC) protein expression; these proteins are the active transporters of a broad range of endogenous compounds and anticancer drugs. In our previous studies, we performed a transcriptomic and functional analysis of CRC in the early stages of metastasis induced by the overexpression of Snail, the transcription factor involved in EMT initiation. Interestingly, we found a correlation between the Snail expression and ABCC4 (MRP4) protein upregulation. The relationship between epithelial transition and ABCC4 expression and function in CRC has not been previously defined. In the current study, we propose that the ABCC4 expression changes during EMT and may be differentially regulated in various subpopulations of CRC. We confirmed that ABCC4 upregulation is correlated with the phenotype conversion process in CRC. The analysis of Gene Expression Omnibus (GEO) sets showed that the ABCC4 expression was elevated in CRC patients. The results of a functional study demonstrated that, in CRC, ABCC4 can regulate cell migration in a cyclic nucleotide-dependent manner.

Cellular Mechanisms Accounting for the Refractoriness of Colorectal Carcinoma to Pharmacological Treatment

Simple Summary

Colorectal cancer (CRC) causes a high number (more than 800,000) of deaths worldwide each year. Better methods for early diagnosis and the development of strategies to enhance the efficacy of the therapeutic approaches used to complement or substitute surgical removal of the tumor are urgently needed. Currently available pharmacological armamentarium provides very moderate benefits to patients due to the high resistance of tumor cells to respond to anticancer drugs. The present review summarizes and classifies into seven groups the cellular and molecular mechanisms of chemoresistance (MOC) accounting for the failure of CRC response to the pharmacological treatment.

Abstract

The unsatisfactory response of colorectal cancer (CRC) to pharmacological treatment contributes to the substantial global health burden caused by this disease. Over the last few decades, CRC has become the cause of more than 800,000 deaths per year. The reason is a combination of two factors: (i) the late cancer detection, which is being partially solved by the implementation of mass screening of adults over age 50, permitting earlier diagnosis and treatment; (ii) the inadequate response of advanced unresectable tumors (i.e., stages III and IV) to pharmacological therapy. The latter is due to the existence of complex mechanisms of chemoresistance (MOCs) that interact and synergize with each other, rendering CRC cells strongly refractory to the available pharmacological regimens based on conventional chemotherapy, such as pyrimidine analogs (5-fluorouracil, capecitabine, trifluridine, and tipiracil), oxaliplatin, and irinotecan, as well as drugs targeted toward tyrosine kinase receptors (regorafenib, aflibercept, bevacizumab, cetuximab, panitumumab, and ramucirumab), and, more recently, immune checkpoint inhibitors (nivolumab, ipilimumab, and pembrolizumab). In the present review, we have inventoried the genes involved in the lack of CRC response to pharmacological treatment, classifying them into seven groups (from MOC-1 to MOC-7) according to functional criteria to identify cancer cell weaknesses. This classification will be useful to pave the way for developing sensitizing tools consisting of (i) new agents to be co-administered with the active drug; (ii) pharmacological approaches, such as drug encapsulation (e.g., into labeled liposomes or exosomes); (iii) gene therapy interventions aimed at restoring the impaired function of some proteins (e.g., uptake transporters and tumor suppressors) or abolishing that of others (such as export pumps and oncogenes).

A452, an HDAC6-selective inhibitor, synergistically enhances the anticancer activity of chemotherapeutic agents in colorectal cancer cells

Although histone deacetylase inhibitors (HDACi) alone could be clinically useful, these are most recently used in combination with other anticancer agents in clinical trials for cancer treatment. Recently, we reported the anticancer activity of an HDAC6-selective inhibitor A452 toward various cancer cell types. This study aims to present a potent synergistic antiproliferative effect of A452/anticancer agent treatment in colorectal cancer cells (CRC) cells, independently of the p53 status. A452 in combination with irinotecan, or SAHA is more potent than either drug alone in the apoptotic pathway as evidenced by activated caspase-3 and PARP, increased Bak and pp38, decreased Bcl-xL, pERK, and pAKT, and induced apoptotic cells. Furthermore, A452 enhances DNA damage induced by anticancer agents as indicated by the increased accumulation of γH2AX and the activation of the checkpoint kinase Chk2. The silencing of HDAC6 enhances the cell growth inhibition and cell death caused by anticancer agents. In addition, A452 induces the synergistic suppression of cell migration and invasion. This study suggests a mechanism by which HDAC6-selective inhibition can enhance the efficacy of specific anticancer agents in CRC cells.

The role of p53 in cancer drug resistance and targeted chemotherapy

Cancer has long been a grievous disease complicated by innumerable players aggravating its cure. Many clinical studies demonstrated the prognostic relevance of the tumor suppressor protein p53 for many human tumor types. Overexpression of mutated p53 with reduced or abolished function is often connected to resistance to standard medications, including cisplatin, alkylating agents (temozolomide), anthracyclines, (doxorubicin), antimetabolites (gemcitabine), antiestrogenes (tamoxifen) and EGFR-inhibitors (cetuximab). Such mutations in the TP53 gene are often accompanied by changes in the conformation of the p53 protein. Small molecules that restore the wild-type conformation of p53 and, consequently, rebuild its proper function have been identified. These promising agents include PRIMA-1, MIRA-1, and several derivatives of the thiosemicarbazone family. In addition to mutations in p53 itself, p53 activity may be also be impaired due to alterations in p53s regulating proteins such as MDM2. MDM2 functions as primary cellular p53 inhibitor and deregulation of the MDM2/p53-balance has serious consequences. MDM2 alterations often result in its overexpression and therefore promote inhibition of p53 activity. To deal with this problem, a judicious approach is to employ MDM2 inhibitors. Several promising MDM2 inhibitors have been described such as nutlins, benzodiazepinediones or spiro-oxindoles as well as novel compound classes such as xanthone derivatives and trisubstituted aminothiophenes. Furthermore, even naturally derived inhibitor compounds such as a-mangostin, gambogic acid and siladenoserinols have been discovered. In this review, we discuss in detail such small molecules that play a pertinent role in affecting the p53-MDM2 signaling axis and analyze their potential as cancer chemotherapeutics.

Effect of Cellular Location of Human Carboxylesterase 2 on CPT-11 Hydrolysis and Anticancer Activity

CPT-11 is an anticancer prodrug that is clinically used for the treatment of metastatic colorectal cancer. Hydrolysis of CPT-11 by human carboxylesterase 2 (CE2) generates SN-38, a topoisomerase I inhibitor that is the active anti-tumor agent. Expression of CE2 in cancer cells is under investigation for the tumor-localized activation of CPT-11. CE2 is normally expressed in the endoplasmic reticulum of cells but can be engineered to direct expression of active enzyme on the plasma membrane or as a secreted form. Although previous studies have investigated different locations of CE2 expression in cancer cells, it remains unclear if CE2 cellular location affects CPT-11 anticancer activity. In the present study, we directly compared the influence of CE2 cellular location on substrate hydrolysis and CPT-11 cytotoxicity. We linked expression of CE2 and enhanced green fluorescence protein (eGFP) via a foot-and-mouth disease virus 2A (F2A) peptide to facilitate fluorescence-activated cell sorting to achieve similar expression levels of ER-located, secreted or membrane-anchored CE2. Soluble CE2 was detected in the medium of cells that expressed secreted and membrane-anchored CE2, but not in cells that expressed ER-retained CE2. Cancer cells that expressed all three forms of CE2 were more sensitive to CPT-11 as compared to unmodified cancer cells, but the membrane-anchored and ER-retained forms of CE2 were consistently more effective than secreted CE2. We conclude that expression of CE2 in the ER or on the membrane of cancer cells is suitable for enhancing CPT-11 anticancer activity.

Evaluation of the plasmatic and parenchymal elution kinetics of two different irinotecan-loaded drug-eluting embolics in a pig model

PURPOSE

To evaluate and compare irinotecan elution kinetics of two drug-eluting embolic agents in a porcine model.

MATERIALS AND METHODS

Embolization of the left liver lobe was performed in 16 domestic pigs, with groups of two receiving 1 mL of DC Bead M1 (70-150 µm) or Embozene TANDEM (75 µm) loaded with 50 mg irinotecan. Irinotecan plasma levels were measured at 0, 10, 20, 30, 60, 120, 180, and 240 minutes after completed embolization and at the time of euthanasia (24 h, 48 h, 72 h, or 7 d). Liver tissue samples were taken to measure irinotecan tissue concentrations.

RESULTS

The highest irinotecan plasma concentrations of both embolic agents were measured 10 and 20 minutes after embolization, and concentrations were significantly higher for DC Bead M1 versus Embozene TANDEM (P = .0019 and P = .0379, respectively). At 48 hours and later follow-up, no irinotecan was measurable in the plasma. For both embolic agents, the highest irinotecan tissue concentration was found after 24 hours and decreased in a time-dependent manner at later follow-up intervals. Additionally, SN-38 tissue levels for both agents were therapeutic at 24 hours, with therapeutic levels of SN-38 at 48 hours in one liver embolized with TANDEM particles. Histopathologic analysis revealed ischemic, inflammatory, and fibrotic tissue reactions.

CONCLUSIONS

Irinotecan is measurable in plasma and hepatic tissue after liver embolization with both types of irinotecan-eluting embolic agents. DC Bead M1 shows early burst elution kinetics, whereas Embozene TANDEM has a lower and slower release profile. The initial burst is significantly greater after embolization with DC Bead M1 than with Embozene TANDEM.

Preclinical activity of nanoliposomal irinotecan is governed by tumor deposition and intratumor prodrug conversion

A major challenge in the clinical use of cytotoxic chemotherapeutics is maximizing efficacy in tumors while sparing normal tissue. Irinotecan is used for colorectal cancer treatment but the extent of its use is limited by toxic side effects. Liposomal delivery systems offer tools to modify pharmacokinetic and safety profiles of cytotoxic drugs. In this study, we defined parameters that maximize the antitumor activity of a nanoliposomal formulation of irinotecan (nal-IRI). In a mouse xenograft model of human colon carcinoma, nal-IRI dosing could achieve higher intratumoral levels of the prodrug irinotecan and its active metabolite SN-38 compared with free irinotecan. For example, nal-IRI administered at doses 5-fold lower than free irinotecan achieved similar intratumoral exposure of SN-38 but with superior antitumor activity. Tumor response and pharmacokinetic modeling identified the duration for which concentrations of SN-38 persisted above a critical intratumoral threshold of 120 nmol/L as determinant for antitumor activity. We identified tumor permeability and carboxylesterase activity needed for prodrug activation as critical factors in achieving longer duration of SN-38 in tumors. Simulations varying tumor permeability and carboxylesterase activity predicted a concave increase in tumor SN-38 duration, which was confirmed experimentally in 13 tumor xenograft models. Tumors in which higher SN-38 duration was achieved displayed more robust growth inhibition compared with tumors with lower SN-38 duration, confirming the importance of this factor in drug response. Overall, our work shows how liposomal encapsulation of irinotecan can safely improve its antitumor activity in preclinical models by enhancing accumulation of its active metabolite within the tumor microenvironment.

Pharmacogenetics research on chemotherapy resistance in colorectal cancer over the last 20 years

During the past two decades the first sequencing of the human genome was performed showing its high degree of inter-individual differentiation, as a result of large international research projects (Human Genome Project, the 1000 Genomes Project International HapMap Project, and Programs for Genomic Applications NHLBI-PGA). This period was also a time of intensive development of molecular biology techniques and enormous knowledge growth in the biology of cancer. For clinical use in the treatment of patients with colorectal cancer (CRC), in addition to fluoropyrimidines, another two new cytostatic drugs were allowed: irinotecan and oxaliplatin. Intensive research into new treatment regimens and a new generation of drugs used in targeted therapy has also been conducted. The last 20 years was a time of numerous in vitro and in vivo studies on the molecular basis of drug resistance. One of the most important factors limiting the effectiveness of chemotherapy is the primary and secondary resistance of cancer cells. Understanding the genetic factors and mechanisms that contribute to the lack of or low sensitivity of tumour tissue to cytostatics is a key element in the currently developing trend of personalized medicine. Scientists hope to increase the percentage of positive treatment response in CRC patients due to practical applications of pharmacogenetics/pharmacogenomics. Over the past 20 years the clinical usability of different predictive markers has been tested among which only a few have been confirmed to have high application potential. This review is a synthetic presentation of drug resistance in the context of CRC patient chemotherapy. The multifactorial nature and volume of the issues involved do not allow the author to present a comprehensive study on this subject in one review.

Mesostructured silica matrix for irinotecan delivery systems

Three mesostructured silica-type carriers, MCM-41 and MCM-41 functionalized by a postsynthesis grafting procedure with hydrophilic aminopropyl groups (MCM-APTES) and hydrophobic vinyl moieties (MCM-VTES), respectively, were investigated in order to elaborate drug delivery systems (DDS) for irinotecan molecules. All studied drug delivery systems exhibited higher cytotoxicity on murine embrionary fibroblastic (MEF) cells than free irinotecan at the same content of the cytostatic agent, whereas no toxicity was observed for the three unloaded carriers. The cytotoxic effect of irinotecan loaded on MCM-41-type carriers continued to increase even 24 h after ceasing the cell exposure to the drug and remained significantly higher than that of free irinotecan. The cellular uptake of silica-type hybrids was investigated by labelling MCM-APTES with Rhodamine B. In the case of the studied DDS, an endocytotic mechanism was found to be involved in the cell uptake process, and it was used to explain the cytotoxicity differences between free irinotecan and drug loaded on MCM-41-type supports.

Regulation and expression of aberrant methylation on irinotecan metabolic genes CES2, UGT1A1 and GUSB in the in-vitro cultured colorectal cancer cells

OBJECTIVE

To evaluate the aberrant methylation gene expression related to the irinotecan (CPT-11) metabolic enzymes in different colorectal cancer cell strains; provide new thoughts and measures for reverse of tumor drug resistance.

METHODS

Studied the aberrant methylation state of CES2, UGT1A1 and GUSB in eight colorectal cancer cell strains through MSP method; and analyze the expression of the target gene after being dealt with DAC.

RESULTS

UGT1A1 showed methylation in five cell strains, while CES2 and GUSB respectively showed consistent unmethylation or hemimethylation. After being dealt with DAC, CES2 and GUSB mRNA showed different expressions but not significant. The expression quantity of UGT1A1mRNA in the low-expression cell strains increased significantly. The expression of UGT1A1 protein where POSITIVE presented low expression was up-regulated to different degrees. Negative tropism was found in CES2 and UGT1A1.

CONCLUSION

Methylation in UGT1A1 gene expression silencing as an important mechanism; methylation could provide an effective target for methylation regulation intervening in the treatment of CPT-11. Meanwhile, studies found that the changes in expressions of CES2 and GUSB might be resulted from some unknown target that still existed during the regulation, or from the influence of methylation in the non-core zone of promoters on the gene transcription.

Photoswitchable particles for on-demand degradation and triggered release

On-demand degradable polymer particles are fabricated via electrospraying of a solution of acetal-protected dextran that further includes 2-(4-methoxystyryl)-4,6-bis(trichloromethyl)-1,3,5-triazine as a photoacid generator. The illumination of UV light gives rise to photoacid and activates the catalytic deprotection of hydroxyl groups of dextran, leading to controlled dissolution of the microparticles in water.

Clinical implications of CES2 RNA expression in neuroblastoma

BACKGROUND/PURPOSE

Human carboxylesterase 2 (CES2) is the key enzyme for metabolic activation of irinotecan (CPT-11). The aim was to evaluate the clinical implications of CES2 RNA expression in neuroblastoma cells.

METHODS

CES2 RNA expression was determined by real-time reverse transcription-polymerase chain reaction in five neuroblastoma cell lines and 42 clinical samples of untreated neuroblastoma. Sensitivity to CPT-11 was assessed by WST-8 colorimetric assays. Induction of apoptosis was evaluated by flow cytometry after CPT-11 exposure. Protein expression of CES2 was evaluated by Western blotting analysis. CES2 RNA expression in clinical samples was investigated for its associations with the clinicopathological characteristics.

RESULTS

CES2 RNA expression was observed in neuroblastoma cells, and its expression in neuroblastoma cell lines was positively correlated with sensitivity to CPT-11 and apoptosis after CPT-11 exposure in vitro. CES2 RNA expression was correlated with the protein levels of CES2 in vitro. CES2 RNA expression was significantly higher in patients with a characteristic related to advanced disease.

CONCLUSIONS

Our results suggest the potential of clinical application of CPT-11 in neuroblastoma treatment for patients with advanced disease.

Chemoprevention, chemotherapy, and chemoresistance in colorectal cancer

Colorectal cancer (CRC) is the third most common cancer and the second leading cause of cancer-related death in industrialized countries. Chemoprevention is a promising approach, but studies demonstrating their usefulness in large populations are still needed. Among several compounds with chemopreventive ability, cyclooxygenase inhibitors have received particular attention. However, these agents are not without side effects, which must be weighed against their beneficial actions. Early diagnosis is critical in the management of CRC patients, because, in early stages, surgery is curative in >90% of cases. If diagnosis occurs at stages II and III, which is often the case, neoadjuvant chemotherapy and radiotherapy before surgery are, in a few cases, recommended. Because of the high risk of recurrence in advanced cancers, chemotherapy is maintained after tumor resection. Chemotherapy is also indicated when the patient has metastases and in advanced cancer located in the rectum. In the last decade, the use of anticancer drugs in monotherapy or in combined regimens has markedly increased the survival of patients with CRC at stages III and IV. Although the rate of success is higher than in other gastrointestinal tumors, adverse effects and development of chemoresistance are important limitations to pharmacological therapy. Genetic profiling regarding mechanisms of chemoresistance are needed to carry out individualized prediction of the lack of effectiveness of pharmacological regimens. This would minimize side effects and prevent the selection of aggressive, cross-resistant clones, as well as avoiding undesirable delays in the use of the most efficient therapeutic approaches to treat these patients.

A combined experimental and mathematical approach for molecular-based optimization of irinotecan circadian delivery

Circadian timing largely modifies efficacy and toxicity of many anticancer drugs. Recent findings suggest that optimal circadian delivery patterns depend on the patient genetic background. We present here a combined experimental and mathematical approach for the design of chronomodulated administration schedules tailored to the patient molecular profile. As a proof of concept we optimized exposure of Caco-2 colon cancer cells to irinotecan (CPT11), a cytotoxic drug approved for the treatment of colorectal cancer. CPT11 was bioactivated into SN38 and its efflux was mediated by ATP-Binding-Cassette (ABC) transporters in Caco-2 cells. After cell synchronization with a serum shock defining Circadian Time (CT) 0, circadian rhythms with a period of 26 h 50 (SD 63 min) were observed in the mRNA expression of clock genes REV-ERBα, PER2, BMAL1, the drug target topoisomerase 1 (TOP1), the activation enzyme carboxylesterase 2 (CES2), the deactivation enzyme UDP-glucuronosyltransferase 1, polypeptide A1 (UGT1A1), and efflux transporters ABCB1, ABCC1, ABCC2 and ABCG2. DNA-bound TOP1 protein amount in presence of CPT11, a marker of the drug PD, also displayed circadian variations. A mathematical model of CPT11 molecular pharmacokinetics-pharmacodynamics (PK-PD) was designed and fitted to experimental data. It predicted that CPT11 bioactivation was the main determinant of CPT11 PD circadian rhythm. We then adopted the therapeutics strategy of maximizing efficacy in non-synchronized cells, considered as cancer cells, under a constraint of maximum toxicity in synchronized cells, representing healthy ones. We considered exposure schemes in the form of an initial concentration of CPT11 given at a particular CT, over a duration ranging from 1 to 27 h. For any dose of CPT11, optimal exposure durations varied from 3h40 to 7h10. Optimal schemes started between CT2h10 and CT2h30, a time interval corresponding to 1h30 to 1h50 before the nadir of CPT11 bioactivation rhythm in healthy cells.

Treatment timing within the 24-h timescale, that is, circadian (circa, about; dies, day) timing, can change by several fold the tolerability and antitumor efficacy of anticancer agents both in experimental models and in cancer patients. Chronotherapeutics aims at improving the tolerability and/or the efficacy of medications through the administration of treatments according to biological rhythms. Recent findings highlight the need of individualizing circadian delivery schedules according to the patient genetic background. In order to address this issue, we propose a combined experimental and mathematical approach in which molecular mathematical models are fitted to experimental measurements of critical biological variables in the studied experimental model or patient. Optimization procedures are then applied to the calibrated mathematical model for the design of theoretically optimal circadian delivery patterns. As a first proof of concept we focused on the anticancer drug irinotecan. A mathematical model of the drug molecular PK-PD was built and fitted to experimental data in Caco-2 colon cancer cells. Numerical algorithms were then applied to theoretically optimize the chronomodulated exposure of Caco-2 cells to irinotecan.

DTS-108, a novel peptidic prodrug of SN38: in vivo efficacy and toxicokinetic studies

PURPOSE

Irinotecan is a prodrug converted to the active cytotoxic molecule SN38 predominantly by the action of liver carboxylesterases. The efficacy of irinotecan is limited by this hepatic activation that results in a low conversion rate, high interpatient variability, and dose-limiting gastrointestinal toxicity. The purpose of this study was to evaluate a novel peptidic prodrug of SN38 (DTS-108) developed to bypass this hepatic activation and thus reduce the gastrointestinal toxicity and interpatient variability compared with irinotecan.

EXPERIMENTAL DESIGN

SN38 was conjugated to a cationic peptide (Vectocell) via an esterase cleavable linker. The preclinical development plan consisted of toxicity and efficacy evaluation in a number of different models and species.

RESULTS

The conjugate (DTS-108) is highly soluble, with a human plasma half-life of 400 minutes in vitro. Studies in the dog showed that DTS-108 liberates significantly higher levels of free SN38 than irinotecan without causing gastrointestinal toxicity. In addition, the ratio of the inactive SN38-glucuronide metabolite compared with the active SN38 metabolite is significantly lower following DTS-108 administration, compared with irinotecan, which is consistent with reduced hepatic metabolism. In vivo efficacy studies showed that DTS-108 has improved activity compared with irinotecan. A significant dose-dependent antitumoral efficacy was observed in all models tested and DTS-108 showed synergistic effects in combination with other clinically relevant therapeutic agents.

CONCLUSIONS

DTS-108 is able to deliver significantly higher levels of SN38 than irinotecan, without the associated toxicity of irinotecan, resulting in an increased therapeutic window for DTS-108 in preclinical models. These encouraging data merit further preclinical and clinical investigation.

The fungus Ustilago maydis and humans share disease-related proteins that are not found in Saccharomyces cerevisiae

Background

The corn smut fungus Ustilago maydis is a well-established model system for molecular phytopathology. In addition, it recently became evident that U. maydis and humans share proteins and cellular processes that are not found in the standard fungal model Saccharomyces cerevisiae. This prompted us to do a comparative analysis of the predicted proteome of U. maydis, S. cerevisiae and humans.

Results

At a cut off at 20% identity over protein length, all three organisms share 1738 proteins, whereas both fungi share only 541 conserved proteins. Despite the evolutionary distance between U. maydis and humans, 777 proteins were shared. When applying a more stringent criterion (≥ 20% identity with a homologue in one organism over at least 50 amino acids and ≥ 10% less in the other organism), we found 681 proteins for the comparison of U. maydis and humans, whereas the both fungi share only 622 fungal specific proteins. Finally, we found that S. cerevisiae and humans shared 312 proteins. In the U. maydis to H. sapiens homology set 454 proteins are functionally classified and 42 proteins are related to serious human diseases. However, a large portion of 222 proteins are of unknown function.

Conclusion

The fungus U. maydis has a long history of being a model system for understanding DNA recombination and repair, as well as molecular plant pathology. The identification of functionally un-characterized genes that are conserved in humans and U. maydis opens the door for experimental work, which promises new insight in the cell biology of the mammalian cell.

Irinotecan Toxicity to Human Blood Cells in vitro: Relationship between Various Biomarkers

Toxic effects of the antineoplastic drug irinotecan on human blood cells at concentrations of 9.0 microg/ml and 4.6 microg/ml were evaluated in vitro. Using the alkaline and neutral comet assay significantly increased levels of primary DNA damage in lymphocytes were detected. The induction of apoptosis/necrosis, as determined by a fluorescent assay, was also notably increased. Cytogenetic outcomes of the treatment were assessed by the analysis of structural chromosome aberrations and fluorescence in situ hybridization. A significantly higher incidence of chromatid breaks and complex quadriradials was observed. Painted chromosomes 1, 2 and 4 were equally involved in translocations, but only the chromosome 1 was involved in the formation of quadriradials. Sister chromatid exchange analysis was performed in parallel with the analysis of lymphocyte proliferation kinetics. The higher concentration of irinotecan caused almost seven-time increase, while the lower one caused a five-time increase of the basal sister chromatid exchange frequency, accompanied with significant lowering of the lymphocyte proliferation index. Using the cytokinesis-block micronucleus assay, a dose-dependent increase in micronucleus frequency along with the formation of nuclear buds and nucleoplasmic bridges was noticed. Inhibitory effects of irinotecan on enzyme acetylcholinesterase (AChE) were studied in erythrocytes. An IC(50) value of 5.0 x 10(-7) was established. Irinotecan was found to be strong inhibitor of the acetylcholine hydrolysis and to cause a continuous decrease of catalytic activity of AChE. The results obtained on a single donor may contribute to the understanding of irinotecan toxicity, but further in vitro and in vivo studies are essential in order to clarify remaining issues, especially on possible inter-individual variability in genotoxic responses to the drug.

Functional study of the 830C>G polymorphism of the human carboxylesterase 2 gene

PURPOSE

Carboxylesterase 2 (CES2) is involved in the activation of the anticancer drug irinotecan to its active metabolite SN-38. We previously identified a single nucleotide polymorphism (SNP), with an allele frequency around 10%, as possibly involved in enzyme expression (Clin Pharmacol Ther 76:528-535, 2004), which could explain the large individual variation in SN-38 disposition.

METHODS

The 830C>G SNP, located in the 5' untranslated region of the gene, was analysed in various DNA samples extracted from: (1) the National Cancer Institute NCI-60 panel of human tumour cell lines; (2) a collection of 104 samples of normal tissue from colorectal cancer patients; (3) blood samples from a population of 95 normal subjects; (4) a collection of 285 human livers. CES2 genotypes were tentatively related to irinotecan cytotoxicity and CES2 expression in the NCI-60 panel; to response to treatment and event-free survival in colorectal cancer patients; and to CES2 expression and catalytic activity in subsets of the human liver collection.

RESULTS

No significant relationship was found in the NCI-60 panel between CES2 830C>G genotype and irinotecan cytotoxicity or CES2 expression. No significant relationship was found between CES2 830C>G genotype and the toxicity and therapeutic efficacy (tumour response, event-free survival) of irinotecan in colorectal cancer patients. There was no significant relationship between CES2 830C>G genotype and CES2 expression and catalytic activity determined in a subset of genotype-selected liver samples.

CONCLUSION

The 830C>G SNP of CES2 is unlikely to have significant functional consequences on CES2 expression, activity or function.

[Hydrolysis by carboxylesterase and disposition of prodrug with ester moiety]

Prodrug is a useful approach for improving the bioavailability of therapeutic agents through increased passive transport. Carboxylesterases (CESs, EC.3.1.1.1.) that show ubiquitous expression profiles play an important role in the biotransformation of ester-containing prodrugs into their therapeutically active forms in the body. High levels of CESs are found in the liver, small intestine and lungs where prodrugs are firstly hydrolyzed before entering the systemic circulation. Rat intestine single-pass perfusion experiments have shown that CES is involved in the intestinal first-pass hydrolysis. Extensive pulmonary first-pass hydrolysis has been observed in accordance to the substrate specificity of CES1 isozyme. Hydrolysis in the human liver and lungs is mainly catalyzed by hCE1 (a human CES1 family isozyme), whereas that in the small intestine is predominantly mediated by hCE2 (a human CES2 family isozyme). hCE2 preferentially hydrolyzes substrates with a small acyl moiety such as CPT-11, due to conformational steric hindrance in its active site. In contrast, hCE1 is able to hydrolyze a variety of substrates due to spacious and flexible substrate binding region in its active site. In addition, hCE1 has been found to catalyze transesterification. Caco-2 cells mainly expresses CES1 isozyme but not CES2 isozyme. Because of the differences in substrate specificity between CES1 and CES2 enzymes, Caco-2 cell monolayer is not suitable for predicting intestinal absorption of prodrugs. These findings indicate that identification of substrate specificity of CES isozymes and development of an in vitro experimental method are essential to support rational design of prodrug.

Irinotecan-cisplatin interactions assessed in cell-based screening assays: cytotoxicity, drug accumulation and DNA adduct formation in an NSCLC cell line

PURPOSE

The use of in vitro drug cytotoxicity assays for the assessment of drug-drug interactions that lead to synergy may not take into account the many cellular determinants responsible for combination effects. Administration of the anticancer drug CPT-11, for example, is associated with rapid conversion of drug from its active lactone form to the inactive carboxylate form. Thus it is difficult to model, in vitro, the behavior of this drug when used as a single agent and when used in a combination setting, this factor may contribute to the interactions measured. Therefore, the objective of this study was to examine the influence of CPT-11 lactone ratio on the cellular accumulation of CPT-11 when used as a single agent and under conditions where it is used in combination with cisplatin.

METHODS

A fixed ratio experimental design was used and drug ratios of CPT-11 and cisplatin were judged to be antagonistic, additive, or synergistic to the non-small cell lung cancer cell line, H460, on the basis of the median effect analysis methodology of Chou and Talalay. The influence of extracellular pH on CPT-11 accumulation was evaluated at pH 7.4 and pH 6.6 when the drug was added immediately to the cells or first pre-equilibrated at the indicated pH. These studies were completed in the presence and absence of cisplatin.

RESULTS

When CPT-11 was added as a single agent to cells in pH = 7.4 media, the drug underwent hydrolysis to the carboxylate form; however, there was a rapid accumulation of the CPT-11 lactone form which peaked at 3,800 pmol/mg protein by 30 min and drops to 570 pmol/mg protein by 24 h. In pH = 6.6 media, accumulation of CPT-11 lactone was substantially lower over a 60 min timecourse; however, the cellular uptake measured at 24 h was comparable to that observed when the drug was added into pH 7.4 media. When evaluating CPT-11 lactone accumulation in a combination setting with cisplatin no significant difference in either CPT-11 lactone accumulation or cisplatin accumulation was observed, suggesting that drug interactions that led to synergy were mechanistically based. Results are presented which suggest that when cisplatin and CPT-11 are used in combination, there was a significant prolongation of platinum association with DNA compared to results obtained when cisplatin was used alone.

CONCLUSION

These results suggest that the CPT-11 lactone to carboxylate ratio does not influence the accumulation of the active CPT-11 lactone form in H460 cells and that CPT-11 does not influence cisplatin uptake when used in combination. It is argued, therefore, that the improved cytotoxicity between CPT-11 and cisplatin, as determined using cell-based assay, has the potential to be preserved in vivo assuming the optimal drug-drug ratio and concentration can be effectively delivered to the tumor.

Human carboxylesterase isozymes: catalytic properties and rational drug design

Human carboxylesterase 1 (hCE-1, CES1A1, HU1) and carboxylesterase 2 (hCE-2, hiCE, HU3) are a serine esterase involved in both drug metabolism and activation. Although both hCE-1 and hCE-2 are present in several organs, the hydrolase activity of liver and small intestine is predominantly attributed to hCE-1 and hCE-2, respectively. The substrate specificity of hCE-1 and hCE-2 is significantly different. hCE-1 mainly hydrolyzes a substrate with a small alcohol group and large acyl group, but its wide active pocket sometimes allows it to act on structurally distinct compounds of either large or small alcohol moiety. In contrast, hCE-2 recognizes a substrate with a large alcohol group and small acyl group, and its substrate specificity may be restricted by a capability of acyl-hCE-2 conjugate formation due to the presence of conformational interference in the active pocket. Furthermore, hCE-1 shows high transesterification activity, especially with hydrophobic alcohol, but negligible for hCE-2. Transesterification may be a reason for the substrate specificity of hCE-1 that hardly hydrolyzes a substrate with hydrophobic alcohol group, because transesterification can progress at the same time when a compound is hydrolyzed by hCE-1. From the standpoint of drug absorption, the intestinal hydrolysis by CES during drug absorption is evaluated in rat intestine and Caco2-cell line. The rat in situ single-pass perfusion shows markedly extensive hydrolysis in the intestinal mucosa. Since the hydrolyzed products are present at higher concentration in the epithelial cells rather than blood vessels and intestinal lumen, hydrolysates are transported by a specific efflux transporter and passive diffusion according to pH-partition. The expression pattern of CES in Caco-2 cell monolayer, a useful in vitro model for rapid screening of human intestinal drug absorption, is completely different from that in human small intestine but very similar to human liver that expresses a much higher level of hCE-1 and lower level of hCE-2. Therefore, the prediction of human intestinal absorption using Caco-2 cell monolayers should be carefully monitored in the case of ester and amide-containing drugs such as prodrugs. Further experimentation for an understanding of detailed substrate specificity for CES and development of in vitro evaluation systems for absorption of prodrug and its hydrolysates will help us to design the ideal prodrug.

Equivalent effect of DNA damage-induced apoptotic cell death or long-term cell cycle arrest on colon carcinoma cell proliferation and tumour growth

Knowledge of the type of biological reaction to chemotherapy is a prerequisite for its rational enhancement. We previously showed that irinotecan-induced DNA damage triggers in the HCT116p53(wt) colon carcinoma cell line a long-term cell cycle arrest and in HCT116p53(-/-) cells apoptosis (Magrini et al., 2002). To compare the contribution of long-term cell cycle arrest and that of apoptosis to inhibition of cell proliferation after irinotecan-induced DNA damage, we used this isogenic system as well as the cell lines LS174T (p53(wt)) and HT-29 (p53(mut)). Both p53(wt) cell lines responded to damage by undergoing a long-term tetraploid G1 arrest, whereas the p53(mut) cell lines underwent apoptosis. Cell cycle arrest as well as apoptosis caused a similar delay in cell proliferation. Irinotecan treatment also induced in mouse tumours derived from the p53(wt) cell lines a tetraploid G1 arrest and in those derived from the p53-deficient cell lines a transient G2/M arrest and apoptosis. The delay of tumour growth was in the same range in both groups, that is, arrest- and apoptosis-mediated tumour growth inhibition was comparable. In conclusion, cell cycle arrest as well as apoptosis may be equipotent mechanisms mediating the chemotherapeutic effects of irinotecan.

Identification of esterases expressed in Caco-2 cells and effects of their hydrolyzing activity in predicting human intestinal absorption

The absorption characteristics of temocapril were investigated using Caco-2 cells, and the esterases expressed in Caco-2 cells were identified. Temocapril was almost completely hydrolyzed to temocaprilat during transport across Caco-2 cells. Hydrolysis experiments of temocapril in Caco-2 cell 9000g supernatant (S9) and brush-border membrane vesicles showed that temocapril was mainly hydrolyzed within the cells after uptake, after which the temocaprilat formed was transported to both the apical and basolateral surfaces. In native polyacrylamide gel electrophoresis by detection of hydrolase activity for 1-naphthylbutyrate, Caco-2 cell S9 showed a band with high esterase activity and another band with extremely low activity. The proteins in the major and minor bands were identified as carboxylesterase-1 (hCE-1) and carboxylesterase-2 (hCE-2). The abundant expression of hCE-1 in Caco-2 cells was supported by reverse transcription-polymerase chain reaction. In the normal human small intestine, hCE-2 is abundantly present, although the human liver expresses much higher levels of hCE-1 and lower levels of hCE-2. The expression pattern of carboxylesterases in Caco-2 cells is completely different from that in human small intestine but very similar to that in human liver. Since the substrate specificity of hCE-1 differs from that of hCE-2, it is suggested that the prediction of human intestinal absorption using Caco-2 cell monolayers should be performed carefully in the case of ester- and amide-containing drugs such as prodrugs.

Enhanced therapeutic efficacy of a novel liposome-based formulation of SN-38 against human tumor models in SCID mice

SN-38 is an active metabolite of CPT-11. The poor solubility of SN-38 in any pharmaceutically acceptable solvent and pH-dependent activity has limited its clinical use. Our objective was to evaluate an easy-to-use liposome-based formulation of SN-38 (LE-SN38) and compare the antitumor activity with its pro-drug CPT-11 against cancer cell lines and human xenograft tumor models. The cytotoxicity of LE-SN38 and CPT-11 was determined in four human cancer cell lines using the sulforhodamine B assay. The therapeutic efficacy was tested against human colon (HT-29) and breast (MX-1) xenograft tumor models in SCID mice. LE-SN38 with greater than 95% drug entrapment was found to be highly cytotoxic against four different cell lines with GI50 values of less than 0.1 microM. In the HT-29 tumor model, LE-SN38 (q x d5) at 2, 4 or 8 mg/kg resulted in 33, 81 and 91% tumor growth inhibition, respectively, compared to the drug-free liposome group. In contrast, similar dose levels of CPT-11 treatment led to only 2, 36 and 46% growth inhibition. For the MX-1 model, LE-SN38 (q x d5) regressed tumor growth by 44 and 88% at 4 and 8 mg/kg dose, respectively, whereas no regression was observed in the CPT-11-treated group. We conclude that LE-SN38 is a novel liposome-based formulation with enhanced therapeutic efficacy against human tumor models.