Irinotecan: mechanisms of tumor resistance and novel strategies for modulating its activity

pH-Responsive PEG-Shedding and Targeting Peptide-Modified Nanoparticles for Dual-Delivery of Irinotecan and microRNA to Enhance Tumor-Specific Therapy

Irinotecan is one of the main chemotherapeutic agents for colorectal cancer (CRC). MicroRNA-200 (miR-200) has been reported to inhibit metastasis in cancer cells. Herein, pH-sensitive and peptide-modified liposomes and solid lipid nanoparticles (SLN) are designed for encapsulation of irinotecan and miR-200, respectively. These peptides include one cell-penetrating peptide, one ligand targeted to tumor neovasculature undergoing angiogenesis, and one mitochondria-targeting peptide. The peptide-modified nanoparticles are further coated with a pH-sensitive PEG-lipid derivative with an imine bond. These specially-designed nanoparticles exhibit pH-responsive release, internalization, and intracellular distribution in acidic pH of colon cancer HCT116 cells. These nanoparticles display low toxicity to blood and noncancerous intestinal cells. Delivery of miR-200 by SLN further increases the cytotoxicity of irinotecan-loaded liposomes against CRC cells by triggering apoptosis and suppressing RAS/β-catenin/ZEB/multiple drug resistance (MDR) pathways. Using CRC-bearing mice, the in vivo results further indicate that irinotecan and miR-200 in pH-responsive targeting nanoparticles exhibit positive therapeutic outcomes by inhibiting colorectal tumor growth and reducing systemic toxicity. Overall, successful delivery of miR and chemotherapy by multifunctional nanoparticles may modulate β-catenin/MDR/apoptosis/metastasis signaling pathways and induce programmed cancer cell death. Thus, these pH-responsive targeting nanoparticles may provide a potential regimen for effective treatment of colorectal cancer.

Identification of candidate genes and miRNAs for sensitizing resistant colorectal cancer cells to oxaliplatin and irinotecan

Drug resistance to irinotecan and oxaliplatin, two widely used chemotherapeutic, has become a common problem in cancerous patients. Despite numerous valuable studies, distinct molecular mechanisms involved in the acquisition of resistance to these anti-cancer drugs have remained a challenge. In this study, we studied the possible resistance mechanisms to irinotecan and oxaliplatin in three CRC cell lines (HCT116, HT29, and LoVo) via integration of microarray data with gene regulatory networks. After determination of hub genes, corresponding miRNAs were predicted using several databases and used in construction and subsequent analysis of miRNA-gene networks. Following to preparation of chemo-resistance CRC cells, a standard real-time PCR was conducted for validation of in silico findings. Topological and functional enrichment analyses of the resulted networks introduced several previously reported drug-resistance genes as well as novel biomarkers as hub genes which seem to be crucial in resistance of colon cancer cells to irinotecan and oxaliplatin. Furthermore, results of the functional annotation revealed the essential role of different signaling pathways like metabolic pathways in drug resistance of CRC cell lines to these drugs. A part of in silico findings was also validated in vitro using oxaliplatin-resistant cell lines. While FOXC1 and NFIC were upregulated in cell lines which were resistant to oxaliplatin, silencing FOXC1 decreased the resistance of SW480 cell line to oxaliplatin. In conclusion, our comparative in silico and in vitro study introduces several novel genes and miRNAs as the resistance-mediators which can be used for sensitizing resistant CRC cells to oxaliplatin and irinotecan.

The identification of CRNDE, H19, UCA1 and HOTAIR as the key lncRNAs involved in oxaliplatin or irinotecan resistance in the chemotherapy of colorectal cancer based on integrative bioinformatics analysis

With the increasing rate of chemoresistance in colorectal cancer (CRC) patients with advanced tumor stages, it is a matter of urgent importance to delineate the factors involved in the drug resistance process. In this study, gene expression profiles were downloaded from the Gene Expression Omnibus database and an integrated analysis with the aim of detecting hub long non‑coding RNAs (lncRNAs) and their regulated, differentially expressed genes (DEGs) during treatment with oxaliplatin (OxPt) or irinotecan was conducted. A total of seven differentially expressed lncRNAs were correlated with OxPt resistance and 21 were correlated with resistance to SN‑38, the active metabolite of irinotecan. Gene Ontology annotation and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis confirmed that drug resistance was strongly associated with an imbalance between cell proliferation and apoptosis, cell energetic metabolism under hypoxic conditions, and angiogenesis. Moreover, a large number of lncRNA‑targeted DEGs were located in extracellular exosomes. Further analyses identified four hub lncRNAs involved in the process of drug resistance, including CRNDE, H19, UCA1 and HOTAIR, which are predictive factors for treatment sensitivity. Among them, HOTAIR stands out as a strong factor, the elevated expression of which is also associated with advanced tumor node and metastasis stage and poor CRC disease prognosis.

Pharmacokinetic and Pharmacogenetic Markers of Irinotecan Toxicity

BACKGROUND

Irinotecan (IRI) is a widely used chemotherapeutic drug, mostly used for first-line treatment of colorectal and pancreatic cancer. IRI doses are usually established based on patient's body surface area, an approach associated with large inter-individual variability in drug exposure and high incidence of severe toxicity. Toxic and therapeutic effects of IRI are also due to its active metabolite SN-38, reported to be up to 100 times more cytotoxic than IRI. SN-38 is detoxified by the formation of SN-38 glucuronide, through UGT1A1. Genetic polymorphisms in the UGT1A1 gene are associated to higher exposures to SN-38 and severe toxicity. Pharmacokinetic models to describe IRI and SN-38 kinetic profiles are available, with few studies exploring pharmacokinetic and pharmacogenetic-based dose individualization. The aim of this manuscript is to review the available evidence supporting pharmacogenetic and pharmacokinetic dose individualization of IRI in order to reduce the occurrence of severe toxicity during cancer treatment.

METHODS

The PubMed database was searched, considering papers published in the period from 1995-2017, using the keywords irinotecan, pharmacogenetics, metabolic genotyping, dose individualization, therapeutic drug monitoring, pharmacokinetics and pharmacodynamics, either alone or in combination, with original papers being selected based on the presence of relevant data.

CONCLUSION

The findings of this review confirm the importance of considering individual patient characteristics to select IRI doses. Currently, the most straightforward approach for IRI dose individualization is UGT1A1 genotyping. However, this strategy is sub-optimal due to several other genetic and environmental contributions to the variable pharmacokinetics of IRI and its active metabolite. The use of dried blood spot sampling could allow the clinical application of limited sampling and population pharmacokinetic models for IRI doses individualization.

The design, analysis and application of mouse clinical trials in oncology drug development

Background

Mouse clinical trials (MCTs) are becoming wildly used in pre-clinical oncology drug development, but a statistical framework is yet to be developed. In this study, we establish such as framework and provide general guidelines on the design, analysis and application of MCTs.

Methods

We systematically analyzed tumor growth data from a large collection of PDX, CDX and syngeneic mouse tumor models to evaluate multiple efficacy end points, and to introduce statistical methods for modeling MCTs.

Results

We established empirical quantitative relationships between mouse number and measurement accuracy for categorical and continuous efficacy endpoints, and showed that more mice are needed to achieve given accuracy for syngeneic models than for PDXs and CDXs. There is considerable disagreement between methods on calling drug responses as objective response. We then introduced linear mixed models (LMMs) to describe MCTs as clustered longitudinal studies, which explicitly model growth and drug response heterogeneities across mouse models and among mice within a mouse model. Case studies were used to demonstrate the advantages of LMMs in discovering biomarkers and exploring drug’s mechanisms of action. We introduced additive frailty models to perform survival analysis on MCTs, which more accurately estimate hazard ratios by modeling the clustered mouse population. We performed computational simulations for LMMs and frailty models to generate statistical power curves, and showed that power is close for designs with similar total number of mice. Finally, we showed that MCTs can explain discrepant results in clinical trials.

Conclusions

Methods proposed in this study can make the design and analysis of MCTs more rational, flexible and powerful, make MCTs a better tool in oncology research and drug development.

Electronic supplementary material

The online version of this article (10.1186/s12885-019-5907-7) contains supplementary material, which is available to authorized users.

Targeting Topoisomerase I in the Era of Precision Medicine

Irinotecan and topotecan have been widely used as anticancer drugs for the past 20 years. Because of their selectivity as topoisomerase I (TOP1) inhibitors that trap TOP1 cleavage complexes, camptothecins are also widely used to elucidate the DNA repair pathways associated with DNA-protein cross-links and replication stress. This review summarizes the basic molecular mechanisms of action of TOP1 inhibitors, their current use, and limitations as anticancer agents. We introduce new therapeutic strategies based on novel TOP1 inhibitor chemical scaffolds including the indenoisoquinolines LMP400 (indotecan), LMP776 (indimitecan), and LMP744, and on tumor-targeted delivery TOP1 inhibitors using liposome, PEGylation, and antibody-drug conjugates. We also address how tumor-specific determinants such as homologous recombination defects (HRD and BRCAness) and Schlafen 11 (SLFN11) expression can be used to guide clinical application of TOP1 inhibitors in combination with DNA damage response inhibitors including PARP, ATR, CHEK1, and ATM inhibitors.

Emerging targets in cancer drug resistance

Drug resistance is a complex phenomenon that frequently develops as a failure to chemotherapy during cancer treatment. Malignant cells increasingly generate resistance to various chemotherapeutic drugs through distinct mechanisms and pathways. Understanding the molecular mechanisms involved in drug resistance remains an important area of research for identification of precise targets and drug discovery to improve therapeutic outcomes. This review highlights the role of some recent emerging targets and pathways which play critical role in driving drug resistance.

A Multifunctional Nanotherapy for Targeted Treatment of Colon Cancer by Simultaneously Regulating Tumor Microenvironment

Colitis-associated colon cancer (CAC) is a widely recognized cancer, while treatment with the existing chemotherapeutic drugs affords limited clinical benefits. Herein we proposed a site-specific, combination nanotherapy strategy for targeted treatment of CAC by the oral route. Methods: A reactive oxygen species (ROS)-responsive and hydrogen peroxide-eliminating material OCD was synthesized, which was further produced into a functional nanoparticle (OCD NP). The antioxidative stress and anti-inflammatory effects of OCD NP were examined by in vitro and in vivo experiments. By packaging an anticancer drug camptothecin-11 (CPT-11) into OCD NP, a ROS-responsive nanotherapy CPT-11/OCD NP was obtained, and its antitumor activity was evaluated by both in vitro and in vivo studies. Preliminary safety studies were also performed for CPT-11/OCD NP in mice. Results: OCD NP significantly attenuated oxidative stress and inhibited inflammatory response in different cells and mice with induced colitis. CPT-11/OCD NP could selectively release drug molecules under intestinal pH conditions and at high levels of ROS. In C26 murine colon carcinoma cells, this nanotherapy showed significantly higher antitumor activity compared to free CPT-11 and a non-responsive CPT-11 nanotherapy. Correspondingly, oral delivery of CPT-11/OCD NP notably inhibited tumorigenesis and tumor growth in mice with induced CAC. By combination therapy with the nanovehicle OCD NP in the inflammatory phase, more desirable therapeutic effects were achieved. Furthermore, CPT-11/OCD NP displayed excellent safety profile for oral administration at a dose that is 87.3-fold higher than that employed in therapeutic studies. Conclusions: Anticancer nanotherapies derived from intrinsic anti-inflammatory nanocarriers are promising for targeted combination treatment of inflammation-associated tumors by simultaneously shaping pro-inflammatory microenvironment toward a relatively normal niche sensitive to chemotherapy.

Prediction of irinotecan toxicity in metastatic colorectal cancer patients based on machine learning models with pharmacokinetic parameters

Irinotecan (CPT-11) is a drug used against a wide variety of tumors, which can cause severe toxicity, possibly leading to the delay or suspension of the cycle, with the consequent impact on the prognosis of survival. The main goal of this work is to predict the toxicities derived from CPT-11 using artificial intelligence methods. The data for this study is conformed of 53 cycles of FOLFIRINOX, corresponding to patients with metastatic colorectal cancer. Supported by several demographic data, blood markers and pharmacokinetic parameters resulting from a non-compartmental pharmacokinetic study of CPT-11 and its metabolites (SN-38 and SN-38-G), we use machine learning techniques to predict high degrees of different toxicities (leukopenia, neutropenia and diarrhea) in new patients. We predict high degree of leukopenia with an accuracy of 76%, neutropenia with 75% and diarrhea with 91%. Among other variables, this study shows that the areas under the curve of CPT-11, SN-38 and SN-38-G play a relevant role in the prediction of the studied toxicities. The presented models allow to predict the degree of toxicity for each cycle of treatment according to the particularities of each patient.

Toward a better understanding of the mechanism of action for intra-arterial delivery of irinotecan from DC Bead(TM) (DEBIRI)

DC Bead is designed for the embolization of liver malignancies combined with local sustained chemotherapy delivery. It was first demonstrated around a decade ago that irinotecan could be loaded into DC Bead and used in a transarterially directed procedure to treat colorectal liver metastases, commonly referred to as drug-eluting bead with irinotecan (DEBIRI). Despite numerous reports of its safe and effective use in treating colorectal liver metastases patients, there remains a perceived fundamental paradox as to how this treatment works. This review of the mechanism of action of DEBIRI provides a rationale for why intra-arterial delivery of this prodrug from an embolic bead provides for enhanced tumor selectivity, sparing the normal liver while reducing adverse side effects associated with the irinotecan therapy.

Crabp2 Promotes Metastasis of Lung Cancer Cells via HuR and Integrin β1/FAK/ERK Signaling

Increased Crabp2 levels have been found in various types of cancer, and are associated with poor patients’ survival. Although Crabp2 is found to be overexpressed in lung cancer, its role in metastasis of lung cancer is unclear. In this study, Crabp2 was overexpressed in high-metastatic C10F4 than low-metastatic lung cancer cells. Analysis of clinical samples revealed that high CRABP2 levels were correlated with lymph node metastases, poor overall survival, and increased recurrence. Knockdown of Crabp2 decreased migration, invasion, anoikis resistance, and in vivo metastasis. Crabp2 was co-immunoprecipitated with HuR, and overexpression of Crabp2 increased HuR levels, which promoted integrin β1/FAK/ERK signaling. Inhibition of HuR or integrin β1/FAK/ERK signaling reversed the promoting effect of Crabp2 in migration, invasion, and anoikis resistance. Knockdown of Crabp2 further inhibited the growth of cancer cells as compared with that by gemcitabine or irinotecan alone. The expression of Crabp2 in human lung tumors was correlated with stress marker CHOP. In conclusion, our findings have identified the promoting role of Crabp2 in anoikis resistance and metastasis. CRABP2 may serve as a prognostic marker and targeting CRABP2 may be exploited as a modality to reduce metastasis.

Association of CHFR Promoter Methylation with Treatment Outcomes of Irinotecan-Based Chemotherapy in Metastatic Colorectal Cancer

Aberrant promoter methylation plays a vital role in colorectal carcinogenesis. However, its role in treatment responses is unclear, especially for metastatic disease. Here, we investigated the association between promoter methylation and treatment outcomes of irinotecan-based chemotherapy in 102 patients with metastatic colorectal cancer. Promoter methylation was examined by methylation-specific polymerase chain reaction for three loci (CHFR, WRN, and SULF2) associated with chemotherapy response and five CpG island methylator phenotype (CIMP)–specific markers (CACNA1G, IGF2, NEUROG1, RUNX3, and SOCS1). Association between CHFR methylation and in vitro sensitivity to irinotecan was also evaluated. Promoter methylation of CHFR, WRN, and SULF2 was identified in 16 (15.7%), 24 (23.5%), and 33 (32.4%) patients, respectively. CIMP status was positive in 22 (21.6%) patients. CHFR methylation was associated with a significantly longer time to progression (TTP) (median: 8.77 vs. 4.43 months, P = .019), with trends favoring higher overall survival (OS) (median: 22.83 vs. 20.17 months, P = .300) and response rates (31.3% vs. 17.4%, P = .300). For patients with unmethylated CHFR, TTP (median: 5.60 vs. 3.53, P = .020) and OS (median: 20.57 vs. 9.23, P = .006) were significantly different according to CIMP status. Colorectal cancer cell lines with CHFR methylation demonstrated increased sensitivity to irinotecan. Both CHFR overexpression and combination with 5-aza-2′-deoxycytidine reversed irinotecan sensitivity in CHFR-methylated cell lines, whereas CHFR knockdown in unmethylated cells restored sensitivity to irinotecan. These data suggest that CHFR methylation may be associated with favorable treatment outcomes of irinotecan-based chemotherapy in patients with metastatic colorectal cancer.

NF-κB pathways in the development and progression of colorectal cancer

Nuclear factor-κB (NF-κB) has been widely implicated in the development and progression of cancer. In colorectal cancer (CRC), NF-κB has a key role in cancer-related processes such as cell proliferation, apoptosis, angiogenesis, and metastasis. The role of NF-κB in CRC is complex, owed to the cross talk with other signaling pathways. Although there is sufficient evidence gained from cell lines and animal models that NF-κB is involved in cancer-related processes, because of a lack of studies in human tissue, the clinical evidence of its importance is limited in patients with CRC. This review summarizes evidence relating to how NF-κB is involved in the development and progression of CRC and comments on future work to be carried out.

The emergence of trophoblast cell-surface antigen 2 (TROP-2) as a novel cancer target

TROP-2 is a glycoprotein first described as a surface marker of trophoblast cells, but subsequently shown to be increased in many solid cancers, with lower expression in certain normal tissues. It regulates cancer growth, invasion and spread by several signaling pathways, and has a role in stem cell biology and other diseases. This review summarizes TROP-2's properties, especially in cancer, and particularly its role as a target for antibody-drug conjugates (ADC) or immunotherapy. When the irinotecan metabolite, SN-38, is conjugated to a humanized anti-TROP-2 antibody (sacituzumab govitecan), it shows potent broad anticancer activity in human cancer xenografts and in patients with advanced triple-negative breast, non-small cell and small-cell lung, as well as urothelial cancers.

Irinotecan and Δ⁸-Tetrahydrocannabinol Interactions in Rat Liver: A Preliminary Evaluation Using Biochemical and Genotoxicity Markers

There is growing interest regarding the use of herbal preparations based on Cannabis sativa for medicinal purposes, despite the poorly understood interactions of their main constituent Δ⁸-tetrahydrocannabinol (THC) with conventional drugs, especially cytostatics. The objective of this pilot study was to prove whether the concomitant intake of THC impaired liver function in male Wistar rats treated with the anticancer drug irinotecan (IRI), and evaluate the toxic effects associated with this exposure. IRI was administered once intraperitoneally (at 100 mg/kg of the body weight (b.w.)), while THC was administered per os repeatedly for 1, 3, and 7 days (at 7 mg/kg b.w.). Functional liver impairments were studied using biochemical markers of liver function (aspartate aminotransferase-AST, alanine aminotransferase-ALP, alkaline phosphatase-AP, and bilirubin) in rats given a combined treatment, single IRI, single THC, and control groups. Using common oxidative stress biomarkers, along with measurement of primary DNA damage in hepatocytes, the degree of impairments caused at the cellular level was also evaluated. THC caused a time-dependent enhancement of acute toxicity in IRI-treated rats, which was confirmed by body and liver weight reduction. Although single THC affected ALP and AP levels more than single IRI, the levels of liver function markers measured after the administration of a combined treatment mostly did not significantly differ from control. Combined exposure led to increased oxidative stress responses in 3- and 7-day treatments, compared to single IRI. Single IRI caused the highest DNA damage at all timepoints. Continuous 7-day oral exposure to single THC caused an increased mean value of comet tail length compared to its shorter treatments. Concomitant intake of THC slightly affected the levels of IRI genotoxicity at all timepoints, but not in a consistent manner. Further studies are needed to prove our preliminary observations, clarify the underlying mechanisms behind IRI and THC interactions, and unambiguously confirm or reject the assumptions made herein.

Structural and photodynamic properties of the anti-cancer drug irinotecan in aqueous solutions of different pHs

This work reports on photophysical studies of the irinotecan (IRT) anti-cancer drug in water solutions of different acidities (pH = 1.11-9.46). We found that IRT co-exists as mono-cationic (C1), di-cationic (C2), or neutral (N) forms. The population of each prototropic species depends on the pH of the solution. At pH = 1.11-3.01, the C1 and C2 structures are stabilized. At pH = 7.00, the most populated species is C1, while at pH values larger than 9.46 the N form is the most stable species. In the 1.11-2.61 pH range, the C1* emission is efficiently quenched by protons to give rise to the emission from C2*. The dynamic quenching constant, KD, is ∼32 M-1. While the diffusion governs the rate of excited-state proton-transfer (ESPT) under these conditions, the reaction rate increases with the proton concentration. A two-step diffusive Debye-Smoluchowski model was applied at pH = 1.11-2.61 to describe the protonation of C1*. The ESPT time constants derived for C1* are 382 and 1720 ps at pH = 1.11 and 1.95, respectively. We found that one proton species is involved in the protonation of C1* to give C2*, in the analyzed acidic pH range. Under alkaline conditions (pH = 9.46), the N form is the most stable structure of IRT. These results indicate the influence of the pH of the medium on the structural and dynamical properties of IRT in water solution. They may help to provide a better understanding on the relationship between the structure and biological activity of IRT.

Pharmacomicrobiomics: exploiting the drug-microbiota interactions in anticancer therapies

Cancer is a major health burden worldwide, and despite continuous advances in medical therapies, resistance to standard drugs and adverse effects still represent an important cause of therapeutic failure. There is a growing evidence that gut bacteria can affect the response to chemo- and immunotherapeutic drugs by modulating either efficacy or toxicity. Moreover, intratumor bacteria have been shown to modulate chemotherapy response. At the same time, anticancer treatments themselves significantly affect the microbiota composition, thus disrupting homeostasis and exacerbating discomfort to the patient. Here, we review the existing knowledge concerning the role of the microbiota in mediating chemo- and immunotherapy efficacy and toxicity and the ability of these therapeutic options to trigger dysbiotic condition contributing to the severity of side effects. In addition, we discuss the use of probiotics, prebiotics, synbiotics, postbiotics, and antibiotics as emerging strategies for manipulating the microbiota in order to improve therapeutic outcome or at least ensure patients a better quality of life all along of anticancer treatments.

Butyrate, a dietary fiber derivative that improves irinotecan effect in colon cancer cells

A diet rich in fiber is associated with a low risk of developing colorectal cancer. Dietary fiber fermentation by intestinal microflora results in the production of butyrate, which has been reported as a chemopreventive agent and a histone deacetylase inhibitor (HDACi). Irinotecan is used as second-line treatment and induces adverse effects with serious life-threatening toxicities in at least 36% of patients. Our study intends to find a synergy that could improve the efficacy and decrease the toxicity of chemotherapy. Results demonstrate that milimolar concentrations of butyrate has an anti-proliferative effect in all three colon cancer cell lines under study, leading to a decrease on cell viability, expression of P21, P53 and β-catenin, being able to modulate P-glycoprotein activity and to induce apoptosis by modulation of BAX/BCL-2 ratio. Combined therapy has a cytotoxic potential, resulting in a synergistic effect, and allows a reduction in irinotecan concentration needed to reduce IC₅₀. This potential was verified in terms of cell viability and death, cell cycle and expression of P21 and P53. Butyrate and irinotecan act synergistically in the three cancer cell lines, despite the different genetic background and location, and inhibited tumor growth in a xenograft model. Butyrate is able to influence the mechanism of LS1034 cell line chemoresistance. Butyrate in combination with chemotherapeutic agents has an important role for the treatment of colorectal cancer. Such understanding can guide decisions about which patients with colorectal cancer may benefit from therapy with butyrate demonstrating the important role of diet in colorectal cancer treatment.

Comparative studies on the interaction of anticancer drug irinotecan with dsDNA and ssDNA

The binding mode and thermodynamic characteristics of the anticancer drug irinotecan (Irino) with dsDNA were investigated. The interaction of Irino with dsDNA indicated its intercalation into the base stacking domain of dsDNA double helix.

CRISPR/Cas9 and cancer targets: future possibilities and present challenges

All cancers have multiple mutations that can largely be grouped into certain classes depending on the function of the gene in which they lie and these include oncogenic changes that enhance cellular proliferation, loss of function of tumor suppressors that regulate cell growth potential and induction of metabolic enzymes that confer resistance to chemotherapeutic agents. Thus the ability to correct such mutations is an important goal in cancer treatment. Recent research has led to the developments of reagents which specifically target nucleotide sequences within the cellular genome and these have a huge potential for expanding our anticancer armamentarium. One such a reagent is the clustered regulatory interspaced short palindromic repeat (CRISPR)-associated 9 (Cas9) system, a powerful, highly specific and adaptable tool that provides unparalleled control for editing the cellular genome. In this short review, we discuss the potential of CRISPR/Cas9 against human cancers and the current difficulties in translating this for novel therapeutic approaches.

Simvastatin enhances irinotecan-induced apoptosis in prostate cancer via inhibition of MCL-1

Prostate cancer is one of the most common malignant tumors around the world. Hyperlipidemia is considered as one of the most important risk factors for the development of prostate cancer. Simvastatin is widely used for the treatment of hyperlipidemia and was previously shown to induce apoptosis in several cancer types including lung, colon, pancreas, breast, and prostate cancer. In this study we aimed to explore the potential role of simvastatin in enhancing irinotecan-induced apoptosis in prostate cancer cells. In addition, the underlying molecular mechanisms driving this potential effect of simvastatin were also explored. PC3 cells were treated with simvastatin, irinotecan or combination. Cell viability was assessed by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) colorimetric assay. Flow cytometry technique was used to analyze apoptosis and cell cycle progression. Western blot was used for detection of protein expression. Results showed that simvastatin has a significant anti-proliferative activity on PC3 cells. Combined treatment of simvastatin with irinotecan exhibited a significant inhibition of PC3 cell growth compared to each treatment alone. Flow cytometry analysis showed that PC3 cell treatment with simvastatin and irinotecan combination demonstrated a remarkable increase in the percentage of apoptotic cells and those accumulated at G0/G1 phase when compared to each treatment alone. Moreover, induction of apoptosis was caspase-independent. Western blot showed that apoptosis was accompanied by upregulation of GRP-78 level and downregulation of Mcl-1 levels in a time-dependent manner. The results of this study demonstrated that combined treatment of simvastatin with chemotherapeutic agents such as irinotecan resulted in enhancement of growth inhibition and induction of prostate cancer cell apoptosis.

The novel tankyrase inhibitor (AZ1366) enhances irinotecan activity in tumors that exhibit elevated tankyrase and irinotecan resistance

BACKGROUND

Dysregulation of the canonical Wnt signaling pathway has been implicated in colorectal cancer (CRC) development as well as incipient stages of malignant transformation. In this study, we investigated the antitumor effects of AZ1366 (a novel tankyrase inhibitor) as a single agent and in combination with irinotecan in our patient derived CRC explant xenograft models.

RESULTS

Six out of 18 CRC explants displayed a significant growth reduction to AZ1366. There was one CRC explant (CRC040) that reached the threshold of sensitivity (TGII ≤ 20%) in this study. In addition, the combination of AZ1366 + irinotecan demonstrated efficacy in 4 out of 18 CRC explants. Treatment effects on the WNT pathway revealed that tankyrase inhibition was ineffective at reducing WNT dependent signaling. However, the anti-tumor effects observed in this study were likely a result of alternative tankyrase effects whereby tankyrase inhibition reduced NuMA levels.

MATERIALS AND METHODS

Eighteen CRC explants were treated with AZ1366 single agent or in combination for 28 days and treatment responses were assessed. Pharmacokinetic (AZ1366 drug concentrations) and pharmacodynamic effects (Axin2 levels) were investigated over 48 hours. Immunohistochemistry of nuclear β-catenin levels as well as western blot was employed to examine the treatment effects on the WNT pathway as well as NuMA.

CONCLUSIONS

Combination AZ1366 and irinotecan achieved greater anti-tumor effects compared to monotherapy. Activity was limited to CRC explants that displayed irinotecan resistance and increased protein levels of tankyrase and NuMA.

Pilot trial of CRLX101 in patients with advanced, chemotherapy-refractory gastroesophageal cancer

Background

CRLX101 is an investigational nanoparticle-drug conjugate with a camptothecin payload. Preclinical evidence indicated preferential uptake in tumors, and tumor xenograft models demonstrate superiority of CRLX101 over irinotecan. A pilot trial was conducted at recommended phase 2 dosing (RP2D) using the bimonthly schedule to assess preferential uptake of CRLX101 in tumor vs. adjacent normal tissue in endoscopically accessible tumors in chemotherapy-refractory gastroesophageal cancer. Results from the biopsies were previously reported and herein we present the clinical outcomes.

Methods

Patients initiated CRLX101 dosed at RP2D (15 mg/m²) on days 1 and 15 of a 28-day cycle. Detection of preferential CRLX101 tumor uptake was the primary endpoint and objective response rate (ORR) was a secondary endpoint. With a sample size of ten patients, the study had 90% power to detect ≥1 responder if the true response rate is ≥21%.

Results

Between Dec. 2012 and Dec. 2014, ten patients with chemotherapy-refractory (median 2 prior lines of therapy, range 1-4) gastric adenocarcinoma were enrolled. The median time-to-progression was 1.7 months. Best response was seen in one patient with stable disease (SD) for 8 cycles. Only ≥ grade 3 drug-related toxicity occurred in one patient with grade 3 cardiac chest pain who was able to resume therapy after CRLX101 was reduced to 12 mg/m².

Conclusions

Bimonthly CRLX101 demonstrated minimal activity with SD as best response in this heavily pretreated population. Future efforts with CRLX101 in gastric cancer should focus on combination and more dose-intensive strategies given its favorable toxicity profile and evidence of preferential tumor uptake.

Not Just Antibiotics: Is Cancer Chemotherapy Driving Antimicrobial Resistance?

The global spread of antibiotic-resistant pathogens threatens to increase the mortality of cancer patients significantly. We propose that chemotherapy contributes to the emergence of antibiotic-resistant bacteria within the gut and, in combination with antibiotics, drives pathogen overgrowth and translocation into the bloodstream. In our model, these processes are mediated by the effects of chemotherapy on bacterial mutagenesis and horizontal gene transfer, the disruption of commensal gut microbiology, and alterations to host physiology. Clinically, this model manifests as a cycle of recurrent sepsis, with each episode involving ever more resistant organisms and requiring increasingly broad-spectrum antimicrobial therapy. Therapies that restore the gut microbiota following chemotherapy or antibiotics could provide a means to break this cycle of infection and treatment failure.

Transformative Nanomedicine of an Amphiphilic Camptothecin Prodrug for Long Circulation and High Tumor Uptake in Cancer Therapy

We report a camptothecin (CPT) prodrug that was well formulated in solution and rapidly transformed into long-circulating nanocomplexes in vivo for highly efficient drug delivery and effective cancer therapy. Specifically, using a redox-responsive disulfide linker, CPT was conjugated with an albumin-binding Evans blue (EB) derivative; the resulting amphiphilic CPT-ss-EB prodrug self-assembled into nanostructures in aqueous solution, thus conferring high solubility and stability. By binding CPT-ss-EB to endogenous albumin, the 80 nm CPT-ss-EB nanoparticles rapidly transformed into 7 nm albumin/prodrug nanocomplexes. CPT-ss-EB was efficient at intracellular delivery into cancer cells, released intact CPT in a redox-responsive manner, and exhibited cytotoxicity as potent as CPT. In mice, the albumin/CPT-ss-EB nanocomplex exhibited remarkably long blood circulation (130-fold greater than CPT) and efficient tumor accumulation (30-fold of CPT), which consequently contributed to excellent therapeutic efficacy. Overall, this strategy of transformative nanomedicine is promising for efficient drug delivery.

Microscale Mass Spectrometry Analysis of Extracellular Metabolites in Live Multicellular Tumor Spheroids

Extracellular compounds in tumors play critical roles in intercellular communication, tumor proliferation, and cancer cell metastasis. However, the lack of appropriate techniques leads to limited studies of extracellular metabolite. Here, we introduced a microscale collection device, the Micro-funnel, fabricated from biocompatible fused silica capillary. With a small probe size (∼25 μm), the Micro-funnel can be implanted into live multicellular tumor spheroids to accumulate the extracellular metabolites produced by cancer cells. Metabolites collected in the Micro-funnel device were then extracted by a microscale sampling and ionization device, the Single-probe, for real-time mass spectrometry (MS) analysis. We successfully detected the abundance change of anticancer drug irinotecan and its metabolites inside spheroids treated under a series of conditions. Moreover, we found that irinotecan treatment dramatically altered the composition of extracellular compounds. Specifically, we observed the increased abundances of a large number of lipids, which are potentially related to the drug resistance of cancer cells. This study provides a novel way to detect the extracellular compounds inside live spheroids, and the successful development of our technique can benefit the research in multiple areas, including the microenvironment inside live tissues, cell-cell communication, biomarker discovery, and drug development.

Terminating the criminal collaboration in pancreatic cancer: Nanoparticle-based synergistic therapy for overcoming fibroblast-induced drug resistance

Pancreatic ductal adenocarcinoma (PDAC) is a lethal cancer with a dismal overall prognosis mainly unchanged over the past decades. PDAC is generally refractory to conventional treatments, and thus novel therapies are urgently needed. Recently, accumulating evidence has indicated that human pancreatic stellate cells (PSCs) facilitate PDAC development and drug resistance through paracrine activation of hedgehog pathway. Here, we report that smart SN38 (active metabolite of irinotecan) polymeric prodrug-based nanoparticles effectively encapsulate the commercial hedgehog pathway inhibitor GDC-0449 for co-delivery. More intriguingly, we obtained size-tunable nanoparticles with increased GDC-0449 loading efficiency by simply extending the chain length of the hydrophobic SN38 block. To better evaluate the efficacy and investigate the synergistic mechanisms, we immortalized human PSCs and established fibroblast-containing models in vitro and in vivo. In PSCs, BxPC-3 cells and MIA PaCa-2 cells, GDC-0449 suppressed the co-culture induced up-regulations of the two drug resistance contributors: sonic hedgehog transcription factor glioma-associated protein1 (GLI-1) and UGT1A glucuronosyltransferase. Importantly, the nanoparticle-mediated co-delivery system exhibited potent antitumor efficacy with enhanced apoptosis and reduced collagen, α-SMA and GLI-1 expression in tumor tissues. These findings reveal a potential strategy to utilize nanoparticle-mediated drug co-delivery platform as an effective combination therapy for fibroblast-enriched PDAC.

Self-assembled polypeptide nanoparticles for intracellular irinotecan delivery

In this research poly(l-lysine)-b-poly(l-leucine) (PLys-b-PLeu) polymersomes were developed. It was shown that the size of nanoparticles depended on pH of self-assembly process and varied from 180 to 650nm. The biodegradation of PLys-b-PLeu nanoparticles was evaluated using in vitro polypeptide hydrolysis in two model enzymatic systems, as well as in human blood plasma. The experiments on the visualization of cellular uptake of rhodamine 6g-loaded and fluorescein-labeled nanoparticles were carried out and the possibility of their penetration into the cells was approved. The cytotoxicity of polymersomes obtained was tested using three cell lines, namely, HEK, NIH-3T3 and A549. It was shown that tested nanoparticles did not demonstrate any cytotoxicity in the concentrations up to 2mg/mL. The encapsulation of specific to colorectal cancer anti-tumor drug irinotecan into developed nanocontainers was performed by means of pH gradient method. The dispersion of drug-loaded polymersomes in PBS was stable at 4°C for a long time (at least 1month) without considerable drug leakage. The kinetics of drug release was thoroughly studied using two model enzymatic systems, human blood serum and PBS solution. The approximation of irinotecan release profiles with different mathematical drug release models was carried out and allowed identification of the release mechanism, as well as the morphological peculiarities of developed particles. The dependence of encapsulation efficiency, as well as maximal loading capacity, on initial drug concentration was studied. The maximal drug loading was found as 320±55μg/mg of polymersomes. In vitro anti-tumoral activity of irinotecan-loaded polymersomes on a colon cancer cell line (Caco-2) was measured and compared to that for free drug.

Modulations in the Peripheral Immune System of Glioblastoma Patient Is Connected to Therapy and Tumor Progression-A Case Report from the IMMO-GLIO-01 Trial

Immune responses are important for efficient tumor elimination, also in immune privileged organs such as the brain. Fostering antitumor immunity has therefore become an important challenge in cancer therapy. This cannot only be achieved by immunotherapies as already standard treatments such as radiotherapy and chemotherapy modify the immune system. Consequently, the understanding of how the tumor, the tumor microenvironment, and immune system are modulated by cancer therapy is required for prognosis, prediction, and therapy adaption. The prospective, explorative, and observational IMMO-GLIO-01 trial was initiated to examine the detailed immune status and its modulation of about 50 patients suffering from primary glioblastoma multiforme (GBM) or anaplastic astrocytoma during standard therapy. Prior to the study, a flow cytometry-based assay was established allowing the analysis of 34 immune cell subsets and their activation state. Here, we present the case of the first and longest accompanied patient, a 53-year-old woman suffering from GBM in the front left lobe. In context of tumor progression and therapy, we describe the modulation of the peripheral immune status over 17 months. Distinct immune modulations that were connected to therapy response or tumor progression were identified. Inter alia, a shift of CD4:CD8 ratio was observed that correlated with tumor progression. Twice we observed a unique composition of peripheral immune cells that correlated with tumor progression. Thus, following up these immune modulations in a closely-meshed manner is of high prognostic and predictive relevance for supporting personalized therapy and increasing therapy success.

Clinical Trial registration: ClinicalTrials.gov, identifier NCT02022384 (registered retrospectively on 13th of December, 2013).

MicroRNAs as a tool to aid stratification of colorectal cancer patients and to guide therapy

Colorectal cancer is a common type of malignant disease with high rates of morbidity and mortality. Although treatment options have been expanded over the last years, the mainstay of curative treatment remains surgical removal of the tumor-bearing organ. Systemic treatment options include classic cytotoxic drugs as well as some biological agents. Noncoding RNAs are an evolving field in cancer diagnosis, prognosis and possible treatment. Noncoding miRNAs are small molecules with huge impact on gene expression. They have been a substantial part of cancer research for more than a decade. In this review article, the current knowledge of miRNAs and colorectal cancer diagnosis, prognosis and novel or evolving therapeutic concepts are discussed. Examples of how miRNAs might change the management of the disease will be described.

Epithelial-mesenchymal transition and cancer stem cell-like phenotype induced by Twist1 contribute to acquired resistance to irinotecan in colon cancer

Inherent and acquired chemoresistance reduce the effectiveness of irinotecan in the treatment of metastatic colorectal cancer (CRC). However, the molecular mechanisms underlying this resistance process are still unclear. Twist1 is one of the master transcription factors of epithelial-mesenchymal transition (EMT). Our previous study indicated that Twist1 is overexpressed in colon cancer tissues, and demonstrated that Twist1 plays a crucial role in the chemoresistance of CRC. In the present study, we further investigated how Twist1 contribute to acquired resistance to irinotecan in colon cancer. The irinotecan-resistant cells were established by gradual adaptation of increasing irinotecan concentrations in LoVo cells, named LoVo/CPT-11R cells. Results showed that cell viabilities to different anticancer drugs were markedly increased in LoVo/CPT-11R cells compared to LoVo cells. Moreover, LoVo/CPT-11R cells displayed EMT, CSC-like cellular morphology and relative biomarkers were also significantly increased. In addition, overexpressed Twist1 LoVo cells were established by lentivirus transfection assay, named LoVo/Twist1 cells. Results showed that the LoVo/Twist1 cells perform a distinctly decreased sensitivity to irinotecan, downregulated expression of E-cadherin, upregulated expression of cluster of differentiation 44 (CD44), and a significant enhancement of invasion and migration potential by regulation of MMP2 compared with control cells. In contrast, the inhibition of Twist1 transfected with siRNA could enhance the irinotecan sensitivity in LoVo/CPT-11R cells and downregulate the expression of vimentin and CD44. Our data provide evidence that EMT and CSC-like phenotype induced by Twist1 contribute to acquire resistance to irinotecan and enhanced migration and invasion in colon cancer.

Irinotecan-Induced Gastrointestinal Dysfunction Is Associated with Enteric Neuropathy, but Increased Numbers of Cholinergic Myenteric Neurons

Gastrointestinal dysfunction is a common side-effect of chemotherapy leading to dose reductions and treatment delays. These side-effects may persist up to 10 years post-treatment. A topoisomerase I inhibitor, irinotecan (IRI), commonly used for the treatment of colorectal cancer, is associated with severe acute and delayed-onset diarrhea. The long-term effects of IRI may be due to damage to enteric neurons innervating the gastrointestinal tract and controlling its functions. Balb/c mice received intraperitoneal injections of IRI (30 mg/kg⁻¹) 3 times a week for 14 days, sham-treated mice received sterile water (vehicle) injections. In vivo analysis of gastrointestinal transit via serial x-ray imaging, facal water content, assessment of gross morphological damage and immunohistochemical analysis of myenteric neurons were performed at 3, 7 and 14 days following the first injection and at 7 days post-treatment. Ex vivo colonic motility was analyzed at 14 days following the first injection and 7 days post-treatment. Mucosal damage and inflammation were found following both short and long-term treatment with IRI. IRI-induced neuronal loss and increases in the number and proportion of ChAT-IR neurons and the density of VAChT-IR fibers were associated with changes in colonic motility, gastrointestinal transit and fecal water content. These changes persisted in post-treatment mice. Taken together this work has demonstrated for the first time that IRI-induced inflammation, neuronal loss and altered cholinergic expression is associated with the development of IRI-induced long-term gastrointestinal dysfunction and diarrhea.

Athymic nude mice as an experimental model for cancer treatment

Athymic nude mice, a murine strain bearing spontaneous deletion in the Foxn1 gene that causes deteriorated or absent thymus (which results in inhibited immune system with reduction of number of T cells), represent a widely used model in cancer research having long lasting history as a tool for preclinical testing of drugs. The review describes three models of athymic mice that utilize cancer cell lines to induce tumors. In addition, various methods that can be applied in order to evaluate activity of anticancer agents in these models are shown and discussed. Although each model has certain disadvantages, they are still considered as inevitable instruments in many fields of cancer research, particularly in finding new drugs that would more effectively combat the cancer disease or enhance the use of current chemotherapy. Finally, the review summarizes strengths and weaknesses as well as future perspectives of the athymic nude mice model in cancer research.

Hypomethylating agents synergize with irinotecan to improve response to chemotherapy in colorectal cancer cells

Colorectal cancer (CRC) is the second leading cause of cancer death in the United States. In the metastatic setting, the majority of patients respond to initial therapies but eventually develop resistance and progress. In this study, we test the hypothesis that priming with epigenetic therapy sensitizes CRC cell lines, which were previously resistant to subsequent chemotherapeutic agents. When multiple CRC cell lines are first exposed to 500 nM of the DNA demethylating agent, 5-aza-cytidine (AZA) in-vitro, and the cells then established as in-vivo xenografts in untreated NOD-SCID mice; there is an enhanced response to cytotoxic chemotherapy with agents commonly used in CRC treatment. For irinotecan (IRI), growth diminished by 16–62 fold as assessed, by both proliferation (IC50) and anchorage independent cell growth soft agar assays. Treatment of resistant HCT116 cell line along with in-vivo, for CRC line xenografts, AZA plus IRI again exhibits this synergistic response with significant improvement in survival and tumor regression in the mice. Genome-wide expression correlates changes in pathways for cell adhesion and DNA repair with the above responses. A Phase 1/2 clinical trial testing this concept is already underway testing the clinical efficacy of this concept in IRI resistant, metastatic CRC (NCT01896856).

Baicalein increases cisplatin sensitivity of A549 lung adenocarcinoma cells via PI3K/Akt/NF-κB pathway

Baicalein, a bioactive flavonoid, exhibits anti-inflammatory and anti-cancer activities. However, few studies reported the interaction of baicalein with chemotherapeutic agents. Our study showed that baicalein significantly enhanced the chemosensitivity of cisplatin (CDDP) in vivo and in vitro. We found that A549/CDDP (resistant to CDDP) cells not only acquired epithelial-mesenchymal transition (EMT) phenotype, but also showed increased NF-κB activity compared with A549 cells (sensitive to CDDP). Our study further demonstrated that PI3K/Akt/NF-κB pathway controlled CDDP resistance via EMT and NF-κB-mediated apoptosis. Baicalein significantly suppressed the PI3K/Akt/NF-κB pathway, leading to conversion of EMT to mesenchymal-epithelial transition (MET, the reciprocal mesenchymal to epithelial transition), and inhibition of NF-κB-mediated antiapoptotic proteins in A549/CDDP cells. In conclusion, our study demonstrated that baicalein reversed the resistance of human A549 lung adenocarcinoma cells to cisplatin by inhibiting EMT and attenuating apoptosis via PI3K/Akt/NF-κB pathway.

Depletion of enteric bacteria diminishes leukocyte infiltration following doxorubicin-induced small intestinal damage in mice

Background & aims

While enteric bacteria have been shown to play a critical role in other forms of intestinal damage, their role in mediating the response to the chemotherapeutic drug Doxorubicin (Doxo) is unclear. In this study, we used a mouse model of intestinal bacterial depletion to evaluate the role enteric bacteria play in mediating Doxo-induced small intestinal damage and, more specifically, in mediating chemokine expression and leukocyte infiltration following Doxo treatment. An understanding of this pathway may allow for development of intervention strategies to reduce chemotherapy-induced small intestinal damage.

Methods

Mice were treated with (Abx) or without (NoAbx) oral antibiotics in drinking water for four weeks and then with Doxo. Jejunal tissues were collected at various time points following Doxo treatment and stained and analyzed for apoptosis, crypt damage and restitution, and macrophage and neutrophil number. In addition, RNA expression of inflammatory markers (TNFα, IL1-β, IL-10) and cytokines (CCL2, CC7, KC) was assessed by qRT-PCR.

Results

In NoAbx mice Doxo-induced damage was associated with rapid induction of apoptosis in jejunal crypt epithelium and an increase weight loss and crypt loss. In addition, we observed an increase in immune-modulating chemokines CCL2, CCL7 and KC and infiltration of macrophages and neutrophils. In contrast, while still positive for induction of apoptosis following Doxo treatment, Abx mice showed neither the overall weight loss nor crypt loss seen in NoAbx mice nor the increased chemokine expression and leukocyte infiltration.

Conclusion

Enteric bacteria play a critical role in Doxo-induced small intestinal damage and are associated with an increase in immune-modulating chemokines and cells. Manipulation of enteric bacteria or the damage pathway may allow for prevention or treatment of chemotherapy-induced small intestinal damage.

Nursing Implications of Chemotherapy Agents and Their Associated Side Effects in Patients With Pancreatic Cancer

BACKGROUND

Survival for patients with advanced (locally advanced unresectable and metastatic disease) pancreatic cancer is very poor; however, several advances in treatment have been made during the past several years. Gemcitabine (Gemzar®)-based regimens, FOLFIRINOX, and nab-paclitaxel (Abraxane®)-based regimens have demonstrated efficacy in patients with advanced pancreatic cancer. Understanding the unique safety profile of each of these regimens is crucial in helping nurses identify symptoms, develop patient education strategies, and ultimately improve outcomes.

OBJECTIVES

This article aims to provide background information on and nursing implications of the treatment of patients with advanced pancreatic cancer by exploring the mechanism of action and efficacy and safety profiles of standard treatment regimens.

METHODS

Key trials of standard treatment regimens used in the treatment of advanced pancreatic cancer were examined with respect to efficacy outcomes and the most commonly observed adverse events. Symptom identification and management strategies are discussed from the nursing perspective.

FINDINGS

The current standard treatment options for patients with advanced pancreatic cancer have differences in efficacy and safety profiles. Nurses should educate themselves on these differences, particularly on associated adverse events and their management.

Chemotherapeutic agent CPT-11 eliminates peritoneal resident macrophages by inducing apoptosis

CPT-11 (Irinotecan) is a first-line chemotherapeutic agent in clinic, but it may induce side effects including diarrhea and enteritis in patients. The underlying mechanism of CPT-11's intestinal toxicity is unclear. Peritoneal resident macrophages have been reported to be important for the maintenance of intestinal homeostasis. In this study, we evaluated the cytotoxic effects of CPT-11 on mouse peritoneal resident macrophages. CPT-11 was administered intraperitoneally to mice and their peritoneal exudate cells were isolated for evaluation. CPT-11 treatment strikingly decreased the ratio of F4/80(hi)MHCII(low) large peritoneal macrophages (LPMs), which are regarded as prenatally-originated peritoneal resident macrophages. Consistent with this, the transcription factor GATA6 specifically expressed in LPMs was barely detectable in the macrophages from CPT-11-treated mice, indicative of elimination of LPMs. Such elimination of LPMs was at least partly due to CPT-induced apoptosis in macrophages, because inhibition of apoptosis by caspase-3 inhibitor z-DEVD-fmk significantly diminished the loss of GATA6(+) LPMs. As GATA6 is a transcription factor that controls expression of multiple genes regulating peritoneal B-1 cell development and translocation, elimination of GATA6(+) LPMs led to a great reduction in B-1 cells in the peritoneal cavity after CPT-11 treatment. These results indicated that CPT-11-induced apoptosis contributed to the elimination of peritoneal resident macrophages, which might in turn impair the function of peritoneal B-1 cells in maintaining intestinal homeostasis. Our findings may at least partly explain why CPT-11 treatment in cancer patients induces diarrhea and enteritis, which may provide a novel avenue to prevent such side effects.

ABCG2 expression in colorectal adenocarcinomas may predict resistance to irinotecan

Irinotecan is a key drug for patients with advanced and recurrent colorectal carcinoma. However, the efficacy of irinotecan is not sufficient; partly, as there is no useful marker to predict chemosensitivity to the drug. The aim of the present study was to evaluate whether the expression levels of adenosine triphosphate-binding cassette sub-family G (WHITE) member 2 (Junior blood group) (ABCG2) in primary colorectal tumors predict chemoresistance to irinotecan. Using the resected primary tumor specimens of 189 patients with colorectal cancer, the association between the immunohistochemical expression of ABCG2 protein and the results of the collagen gel droplet embedded culture drug sensitivity test, performed to evaluate the chemosensitivity to SN-38 (an active metabolite of irinotecan), was investigated. Among the 189 patients, 17 received irinotecan-based chemotherapy, and their responses and progression-free survival (PFS) were analyzed. The tumors of patients with increased ABCG2 expression accounted for 60% of the tumors examined, and were significantly more resistant to SN-38, compared with patients with low ABCG2 expression (P<0.001). In a multivariate logistic regression analysis, increased expression of ABCG2 protein was an independent and significant predictor of resistance to SN-38, increasing the risk of resistance by 12-fold. Increased expression of ABCG2 and a low sensitivity to SN-38 was significantly associated with resistance to irinotecan-based chemotherapy (P=0.01 and 0.028, respectively). The median PFS of patients with increased expression of ABCG2 was significantly shorter, compared with patients with low expression levels of ABCG2 (104 vs. 242 days; P=0.047). The increased immunohistochemical expression of ABCG2 in primary tumors may be a useful predictive biomarker of resistance to irinotecan-based chemotherapy for patients with recurrent or metastatic colorectal cancer.