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

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.

Humanized anti-hepatocyte growth factor (HGF) antibody suppresses innate irinotecan (CPT-11) resistance induced by fibroblast-derived HGF

The growth factors derived from the microenvironment create an environment conducive to tumor growth and survival. HGF deprivation using neutralizing antibody enhanced chemosensitivity in colorectal cancer cells (CRC). We determined secreted HGF in fibroblast conditioned medium (CM). Combination treatment of anti-HGF antibody and irinotecan (CPT-11) directly enhanced CPT-11 sensitivity in CRC. We generated xenograft in NOD/SCID mice inoculating HCT-116 human colorectal cancer cells subcutaneously with or without fibroblast. We found that the combination of CPT-11 and anti-HGF antibody induced marked suppression of tumor development. These results suggest that HGF produced by fibroblast induce CPT-11 resistance, and that anti-HGF antibody abrogate such resistance in vivo. fibroblast-derived HGF is important determinant of chemoresistance. Anti-HGF monoclonal antibody treatment confirmed the importance of this growth factor for chemoresistance in CRC. These results present new options toward the early diagnosis of chemoresistance and suggest novel combinations of chemotherapy and anti-HGF agents to prevent or significantly delay the onset of therapy resistance.

Chemotherapy induced diarrhea

Purpose: To provide a current review of the literature related to chemotherapy induced diarrhea (CID), including clinical assessment, recommended management guidelines and investigational pharmacological approaches for the prevention and treatment of CID.

Data sources: A search of MEDLINE, PubMed, EMBASE, Cochrane Library, International Pharmaceutical Abstracts, and Web of Science (1996—2006) databases was conducted using terms such as: chemotherapy, diarrhea, diarrhoea, and irinotecan. Appropriate references from selected articles were also used. The search engine, Google, provided further access to information.

Data extraction: The retrieved literature was reviewed to include all articles pertaining to the pathophysiology, assessment and management of CID.

Data synthesis: Diarrhea is a debilitating and potentially life-threatening side effect associated with many chemotherapeutic agents. Despite the high incidence and severity of CID, it is often under recognized and poorly managed. A multidisciplinary panel recently updated recommended practice guidelines for the assessment and management of CID. Prompt and aggressive intervention is important in order to minimize the negative consequences of CID, such as dehydration, which may cause interruptions in optimal clinical outcomes or may lead to life-threatening sequelae. Further investigation into the pathophysiology of CID may allow for more directed approaches in the prophylaxis and treatment of CID. J Oncol Pharm Practice (2007) 13: 181—198.

Dual-targeting hybrid nanoparticles for the delivery of SN38 to Her2 and CD44 overexpressed human gastric cancer

Gastric cancer (GC), particularly of the type with high expression of both human epidermal growth factor receptor 2 (Her2) and cluster determinant 44 (CD44), is one of the most malignant human tumors which causes a high mortality rate due to rapid tumor growth and metastasis. To develop effective therapeutic treatments, a dual-targeting hybrid nanoparticle (NP) system was designed and constructed to deliver the SN38 agent specifically to human solid gastric tumors bearing excessive Her2 and CD44. The hybrid NPs consist of a particle core made of the biodegradable polymer PLGA and a lipoid shell prepared by conjugating the AHNP peptides and n-hexadecylamine (HDA) to the carboxyl groups of hyaluronic acid (HA). Upon encapsulation of the SN38 agent in the NPs, the AHNP peptides and HA on the NP surface allow preferential delivery of the drug to gastric cancer cells (e.g., HGC27 cells) by targeting Her2 and CD44. Cellular uptake and in vivo biodistribution experiments verified the active targeting and prolonged in vivo circulation properties of the dual-targeting hybrid NPs, leading to enhanced accumulation of the drug in tumors. Furthermore, the anti-proliferation mechanism studies revealed that the inhibition of the growth and invasive activity of HGC27 cells was not only attributed to the enhanced cellular uptake of dual-targeting NPs, but also benefited from the suppression of CD44 and Her2 expression by HA and AHNP moieties. Finally, intravenous administration of the SN38-loaded dual-targeting hybrid NPs induced significant growth inhibition of HGC27 tumor xenografted in nude mice compared with a clinical antitumor agent, Irinotecan (CPT-11), and the other NP formulations. These results demonstrate that the designed dual-targeting hybrid NPs are promising for targeted anti-cancer drug delivery to treat human gastric tumors over-expressing Her2 and CD44.

Combining ABCG2 Inhibitors with IMMU-132, an Anti-Trop-2 Antibody Conjugate of SN-38, Overcomes Resistance to SN-38 in Breast and Gastric Cancers

Sacituzumab govitecan (IMMU-132), an SN-38-conjugated antibody-drug conjugate, is showing promising therapeutic results in a phase I/II trial of patients with advanced Trop-2-expressing, metastatic, solid cancers. As members of the ATP-binding cassette (ABC) transporters confer chemotherapy resistance by active drug efflux, which is a frequent cause of treatment failure, we explored the use of known inhibitors of ABC transporters for improving the therapeutic efficacy of IMMU-132 by overcoming SN-38 resistance. Two human tumor cell lines made resistant to SN-38, MDA-MB-231-S120 (human breast cancer) and NCI-N87-S120 (human gastric cancer), were established by continuous exposure of the parental cells to stepwise increased concentrations of SN-38 and analyzed by flow cytometry for functional activities of ABCG2 and ABCB1, immunoblotting and qRT-PCR for the expression of ABCG2 at both protein and mRNA levels, and MTS assays for the potency of SN-38 alone or in combination with a modulator of ABC transporters. MDA-MB-231-S120 and NCI-N87-S120 displayed reduced sensitivity to SN-38 in vitro, with IC50 values approximately 50-fold higher than parental MDA-MB-231 and NCI-N87 cells. The increase in drug resistance of both S120 cell populations is associated with the expression of functional ABCG2, but not ABCB1. Importantly, treatment of both S120 sublines with known ABCG2 inhibitors (fumitremorgin C, Ko143, and YHO-13351) restored toxicity of SN-38, and the combination of YHO-13351 with IMMU-132 increased the median survival of mice bearing NCI-N87-S120 xenografts. These results provide a rationale for combination therapy of IMMU-132 and inhibitors of ABC transporters, such as YHO-13351. Mol Cancer Ther; 15(8); 1910-9. ©2016 AACR.

Characteristics of anticancer drug studies registered on the Chinese Clinical Trial Registry (ChiCTR) from 2007 to 2015

OBJECTIVE

This research aims to examine the basic and methodological characteristics of anticancer drug studies registered on the Chinese Clinical Trial Registry (ChiCTR) and explores the progress of implementation of good clinical practice (GCP) and the challenges it poses for anticancer drug research in China.

METHODS

The studies from 2007 to 2015 were downloaded from the ChiCTR and those involving anticancer drugs with evaluation of the main dimensions. The numerical trend of the studies registered each year was analyzed. Chi-square tests were performed to test for significant differences between different funding sources, types of drug and study phases.

RESULTS

Six hundred and four anticancer drug studies were collected. The overall number of anticancer drug studies was increased. Significant differences could be seen in the dimensions of multicentre study (P = 0.000), participant number (P = 0.029) and randomization procedure (P = 0.005) for the three funding sources. There were significant differences in the dimensions of multicentre study (P = 0.001), participant number (P = 0.025), collecting samples from participants (P = 0.006), and randomization procedure (P = 0.009) between different kinds of drugs. There were also significant differences in the dimension of participant number (P = 0.025) and randomization procedure (P = 0.016) between different study phases.

CONCLUSION

There are problems with study registry criteria and study type classification method. Also, within the studies researched, heterogeneity exists for various dimensions. Different sources of funding, distinct types of drug and disparate phases of study lead to significant differences in certain dimensions of anticancer drug studies.

Cancer chemoresistance; biochemical and molecular aspects: a brief overview

The effectiveness of chemotherapy is one of the main challenges in cancer treatment and resistance to classic drugs and traditional treatment processes is an obstacle to this goal. Drug resistance that may be inherent or adventitious can cause poor treatment outcome and tumor relapse. In most cases, resistance to a drug can lead to resistance to many other drugs structure and function of which is not necessarily similar to the first drug. This phenomenon is the main mechanism behind failure of many of metastatic cancers. There are various molecular mechanisms involved in multidrug resistance, including change in the activity of membrane transporters (such as ABC transporters), increase of drug metabolism, change of the target enzyme (such as mutations that change thymidylate synthase and topoisomerases), promotion of DNA damage repair, and escape from drug induced apoptosis. Clinical and laboratory investigations on biomarkers involved in the response to chemotherapy have characterized the key factors behind the failure of treatments. Knowing the molecular factors involved in drug resistance may help us to develop new strategies for more promising chemotherapy and reduce the rate of relapse. In this brief review, molecular mechanisms and tumor microenvironment leading to decreased drug sensitivity, and strategies of reversing drug resistance are described.

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.

Pharmacologic resistance in colorectal cancer: a review

Colorectal cancer (CRC) persists as one of the most prevalent and deadly tumor types in both men and women worldwide. This is in spite of widespread, effective measures of preventive screening, and also major advances in treatment options. Despite advances in cytotoxic and targeted therapy, resistance to chemotherapy remains one of the greatest challenges in long-term management of incurable metastatic disease and eventually contributes to death as tumors accumulate means of evading treatment. We performed a comprehensive literature search on the data available through PubMed, Medline, Scopus, and the ASCO Annual Symposium abstracts through June 2015 for the purpose of this review. We discuss the current state of knowledge of clinically relevant mechanisms of resistance to cytotoxic and targeted therapies now in use for the treatment of CRC.

Anticancer effect of SZC017, a novel derivative of oleanolic acid, on human gastric cancer cells

Oleanolic acid (OA) and its several derivatives possess chemopreventive and chemotherapeutic functions against a series of cancer types. Many chemotherapeutic compounds are effective in improving the quality of life and prolonging the survival of patients with gastric cancer, therefore progress in the treatment of gastric cancer, especially the anticancer effects of OA derivatives must be achieved. The inhibitory effect of SZC017, a newly synthesized derivative of OA, on cell viability was determined by MTT assay. Furthermore, flow cytometry, transmission electron microscopy, and western blot analysis revealed that the inhibition of cell viability by OA was mediated by triggering the intrinsic apoptosis of gastric cancer cells, and inducing S phase arrest of SGC7901 cells. Mechanistically, SZC017 was effective against gastric cancer cells via inhibiting Akt/NF‑κB signaling and topoisomerase I and IIα proteins. Taken together, our data indicate that SZC017 may be a potential chemotherapeutic agent against gastric cancer cells.

Enzyme-Instructed Intracellular Molecular Self-Assembly to Boost Activity of Cisplatin against Drug-Resistant Ovarian Cancer Cells

Anticancer drug resistance demands innovative approaches that boost the activity of drugs against drug-resistant cancers without increasing the systemic toxicity. Here we show the use of enzyme-instructed self-assembly (EISA) to generate intracellular supramolecular assemblies that drastically boost the activity of cisplatin against drug-resistant ovarian cancer cells. We design and synthesize small peptide precursors as the substrates of carboxylesterase (CES). CES cleaves the ester bond pre-installed on the precursors to form the peptides that self-assemble in water to form nanofibers. At the optimal concentrations, the precursors themselves are innocuous to cells, but they double or triple the activity of cisplatin against the drug-resistant ovarian cancer cells. This work illustrates a simple, yet fundamental, new way to introduce non-cytotoxic components into combination therapies with cisplatin without increasing the systemic burden or side effects.

Hyaluronic acid-decorated dual responsive nanoparticles of Pluronic F127, PLGA, and chitosan for targeted co-delivery of doxorubicin and irinotecan to eliminate cancer stem-like cells

Dual responsive nanoparticles are developed for co-delivery of multiple anticancer drugs to target the drug resistance mechanisms of cancer stem-like cells (CSCs). The nanoparticles consist of four polymers approved by the Food and Drug Administration (FDA) for medical use: Poly(d,l-lactide-co-glycolide) (PLGA), Pluronic F127 (PF127), chitosan, and hyaluronic acid (HA). By combining PLGA and PF127 together, more stable and uniform-sized nanoparticles can be obtained than using PLGA or PF127 alone. The HA is used for not only actively targeting CSCs to reduce their drug resistance due to dormancy (i.e., slow metabolism), but also replacing the commonly used poly(vinyl alcohol) as a stabilizing agent to synthesize the nanoparticles using the double-emulsion approach and to allow for acidic pH-triggered drug release and thermal responsiveness. Besides minimizing drug efflux from CSCs, the nanoparticles encapsulated with doxorubicin hydrochloride (DOX, hydrophilic) and irinotecan (CPT, hydrophobic) to inhibit the activity of topoisomerases II and I, respectively, can fight against the CSC drug resistance associated with their enhanced DNA repair and anti-apoptosis. Ultimately, the two drugs-laden nanoparticles can be used to efficiently destroy the CSCs both in vitro and in vivo with up to ∼500 times of enhancement compared to the simple mixture of the two drugs.

Quantitative interactome analysis reveals a chemoresistant edgotype

Chemoresistance is a common mode of therapy failure for many cancers. Tumours develop resistance to chemotherapeutics through a variety of mechanisms, with proteins serving pivotal roles. Changes in protein conformations and interactions affect the cellular response to environmental conditions contributing to the development of new phenotypes. The ability to understand how protein interaction networks adapt to yield new function or alter phenotype is limited by the inability to determine structural and protein interaction changes on a proteomic scale. Here, chemical crosslinking and mass spectrometry were employed to quantify changes in protein structures and interactions in multidrug-resistant human carcinoma cells. Quantitative analysis of the largest crosslinking-derived, protein interaction network comprising 1,391 crosslinked peptides allows for ‘edgotype' analysis in a cell model of chemoresistance. We detect consistent changes to protein interactions and structures, including those involving cytokeratins, topoisomerase-2-alpha, and post-translationally modified histones, which correlate with a chemoresistant phenotype.

Changes in protein–protein interactions result in changes to cellular phenotype. Here the authors use crosslinking mass spectrometry to derive a quantitative protein interaction network in drug-sensitive and -resistant HeLa cells, and uncover a chemoresistant ‘edgotype'.

MicroRNAs predict and modulate responses to chemotherapy in colorectal cancer

Colorectal cancer (CRC) is the fourth leading cause of cancer-related death globally. Chemotherapy regimens consisting of 5-fluorouracil (5-FU) in combination with either oxaliplatin or irinotecan are the first-line options for treatment of metastatic CRC. However, primary or acquired resistance to these chemotherapeutics is a major clinical challenge. MicroRNAs (miRNAs) are a group of small non-coding RNAs that regulate gene expression post-transcriptionally. miRNAs play important roles in many cancer-related processes, including cell proliferation, apoptosis and invasion, and their dysregulation is implicated in colorectal tumourigenesis. Pertinent to chemotherapy, increasing evidence has revealed that miRNAs can be directly linked to chemosensitivity in CRC. In this review, we summarize current evidence concerning the role of miRNAs in prediction and modulation of cellular responses to 5-FU, oxaliplatin and irinotecan in CRC. We also discuss the possible targets and intracellular pathways involved in these processes.

Irinotecan and nedaplatin as salvage therapy for patients with advanced germ cell tumors following intensive treatment with cisplatin-based combination chemotherapies

BACKGROUND

To analyze the clinical outcomes of the irinotecan plus nedaplatin (IN) regimen in patients with advanced germ cell tumors (GCTs) refractory to cisplatin-based combination chemotherapies.

METHODS

This study included a total of 20 consecutive advanced GCT patients who were categorized into intermediate- or poor-risk GCT groups according to the International Germ Cell Consensus Classification, and were judged to show refractory or relapsed disease after bleomycin, etoposide and cisplatin and cisplatin, ifosfamide and paclitaxel therapies. All 20 patients subsequently received IN therapy (irinotecan 100 mg/m(2) on days 1 and 15; nedaplatin 100 mg/m(2) on day 1) every 4 weeks.

RESULTS

Following a median of 3 cycles of IN, 9 patients (45 %) achieved normalization of serum tumor markers. In addition, surgical resection of the residual tumors following IN was performed in 5 patients, of whom 4 were pathologically diagnosed with no viable cancer cells. At a median follow-up of 9 months, 11 patients (55 %) were alive, including 7 (35 %) with no evidence of disease, whereas the remaining 9 (45 %) died of disease progression. The median duration of overall survival after the introduction of IN to these 20 patients was 13.4 months. Severe hematological toxicities were observed in all patients, but were manageable. Although fatal treatment-related interstitial pneumonia occurred in 1 patient, other non-hematological toxicities were generally tolerable.

CONCLUSIONS

Considering the markedly unfavorable characteristics of the included patients with advanced GCT who were intensively treated with cisplatin-based combination chemotherapies, IN could be regarded as having promising therapeutic activity with an acceptable toxicity profile.

Carboxylesterase 2 as a Determinant of Response to Irinotecan and Neoadjuvant FOLFIRINOX Therapy in Pancreatic Ductal Adenocarcinoma

BACKGROUND

Serine hydrolases (SHs) are among the largest classes of enzymes in humans and play crucial role in many pathophysiological processes of cancer. We have undertaken a comprehensive proteomic analysis to assess the differential expression and cellular localization of SHs, which uncovered distinctive expression of Carboxylesterase 2 (CES2), the most efficient carboxyl esterase in activating the prodrug irinotecan into SN-38, in pancreatic ductal adenocarcinoma (PDAC). We therefore assessed the extent of heterogeneity in CES2 expression in PDAC and its potential relevance to irinotecan based therapy.

METHODS

CES2 expression in PDAC and paired nontumor tissues was evaluated by immunohistochemistry. CES2 activity was assessed by monitoring the hydrolysis of the substrate p-NPA and correlated with irinotecan IC50 values by means of Pearson's correlation. Kaplan-Meier and Cox regression analyses were applied to assess the association between overall survival and CES2 expression in patients who underwent neoadjuvant FOLFIRINOX treatment. All statistical tests were two-sided.

RESULTS

Statistically significant overexpression of CES2, both at the mRNA and protein levels, was observed in PDAC compared with paired nontumor tissue (P < .001), with 48 of 118 (40.7%) tumors exhibiting high CES2 expression. CES2 activity in 11 PDAC cell lines was inversely correlated with irinotecan IC50 values (R = -0.68, P = .02). High CES2 expression in tumor tissue was associated with longer overall survival in resectable and borderline resectable patients who underwent neoadjuvant FOLFIRINOX treatment (hazard ratio = 0.14, 95% confidence interval = 0.04 to 0.51, P = .02).

CONCLUSION

Our findings suggest that CES2 expression and activity, by mediating the intratumoral activation of irinotecan, is a contributor to FOLFIRINOX sensitivity in pancreatic cancer and CES2 assessment may define a subset of patients likely to respond to irinotecan based therapy.

Identification of Sestrin3 Involved in the In vitro Resistance of Colorectal Cancer Cells to Irinotecan

Irinotecan, an analogue of camptothecin, is frequently used as a single agent or in combination with other anticancer drugs for the treatment of colorectal cancer. However, the drug resistance of tumors is a major obstacle to successful cancer treatment. In this study, we established that cells acquire chronic resistance to irinotecan. We profiled their differential gene expression using microarray. After gene ontology (GO) and KEGG pathway analysis of the microarray data, we specifically investigated whether Sestrin3 could decrease irinotecan resistance. Our results revealed that Sestrin3 enhanced the anticancer effect of irinotecan in vitro in LoVo cells that had acquired resistance to irinotecan. Irinotecan-resistant LoVo cells showed lower reactive oxygen species (ROS) production than their irinotecan-sensitive parental cells. ROS production was increased by Sestrin3 knockdown in irinotecan-resistant LoVo cells. Our results indicate that Sestrin3 might be a good target to develop therapeutics that can help to overcome resistance to irinotecan.

Phase II trial of cetuximab plus cisplatin and irinotecan in patients with cisplatin and irinotecan-refractory metastatic esophagogastric cancer

INTRODUCTION

Cetuximab in combination with irinotecan has shown clinically significant activity in patients with irinotecan-refractory colon cancer. We evaluated the efficacy of cetuximab in combination with cisplatin and irinotecan in patients with metastatic esophagogastric cancer refractory to cisplatin and irinotecan.

PATIENTS AND METHODS

Patients with disease progression within 3 months of treatment with prior cisplatin and irinotecan received weekly cetuximab and cisplatin/irinotecan for 2 weeks, followed by a 1-week rest period. The primary endpoint was objective response rate. Secondary endpoints included progression-free and overall survival.

RESULTS

Sixteen patients were enrolled (87% with adenocarcinoma). The median prior exposure to cisplatin/irinotecan was 3.6 months. The addition of cetuximab to cisplatin and irinotecan was well tolerated and there were no unexpected toxicities. One of 16 patients treated on study experienced durable RECIST partial response lasting 10 months. The median progression-free survival was 1.4 months (range, 0.5 to 10 mo).

CONCLUSIONS

The addition of cetuximab did not overcome irinotecan resistance in patients with metastatic esophagogastric cancer. Further investigation of this strategy in esophagogastric cancer is not justified. The limited activity observed for cetuximab is consistent with other studies evaluating single-agent cetuximab.

Development of an oral nanotherapeutics using redox nanoparticles for treatment of colitis-associated colon cancer

Oral chemotherapy is the preferred treatment for colon cancer. However, this strategy faces many challenges, including instability in the gastrointestinal (GI) tract, insufficient bioavailability, low tumor targeting, and severe adverse effects. In this study, we designed a novel redox nanoparticle (RNP(O)) that is an ideal oral therapeutics for colitis-associated colon cancer treatment. RNP(O) possesses nitroxide radicals in the core, which act as reactive oxygen species (ROS) scavengers. Orally administered RNP(O) highly accumulated in colonic mucosa, and specifically internalized in cancer tissues, but less in normal tissues. Despite of long-term oral administration of RNP(O), no noticeable toxicities were observed in major organs of mice. Because RNP(O) effectively scavenged ROS, it significantly suppressed tumor growth after accumulation at tumor sites. Combination of RNP(O) with the conventional chemotherapy, irinotecan, led to remarkably improved therapeutic efficacy and effectively suppressed its adverse effects on GI tract. Therefore, RNP(O) is promising oral nanotherapeutics for cancer therapies.

Quantitative determination of irinotecan and the metabolite SN-38 by nanoflow liquid chromatography-tandem mass spectrometry in different regions of multicellular tumor spheroids

A new and simple method was developed to evaluate the distribution of therapeutics in three-dimensional multicellular tumor spheroids (MCTS) by combining serial trypsinization and nanoflow liquid chromatography-tandem mass spectrometry (nLC-MS/MS). This methodology was validated with quantitative measurements of irinotecan and its bioactive metabolite, SN-38, in distinct spatial regions of HCT 116 MCTS. Irinotecan showed a time-dependent permeability into MCTS with most of the drug accumulating in the core after 24 h of treatment. The amount of SN-38 detected was 30 times lower than that of the parent drug, and was more abundant in the outer rim and intermediate regions of MCTS where proliferating cells were present. This method can be used to investigate novel and established drugs. It enables investigation of drug penetration properties and identification of metabolites with spatial specificity in MCTS. The new approach has great value in facilitating the drug evaluation process.

Physalin B not only inhibits the ubiquitin-proteasome pathway but also induces incomplete autophagic response in human colon cancer cells in vitro

AIM

To investigate the effects of physalin B insolated from Physalis divericata on human colon cancer cells in vitro and its anticancer mechanisms.

METHODS

Human HCT116 colon cancer cell line was tested. Cell viability and apoptosis were detected, and relevant proteins were measured using Western blot analyses. Autophagosomes were observed in stable GFP-LC3 HCT116 cells. Localization of autophagosomes and lysosomes was evaluated in GFP-LC3/RFP-LAMP1-co-transfected cells. Microtubules and F-actin microfilaments were observed with confocal microscope. Mitochondrial ROS (mito-ROS) was detected with flow cytometry in the cells stained with MitoSox dye.

RESULTS

Physalin B inhibited the viability of HCT116 cells with an IC50 value of 1.35 μmol/L. Treatment of the cells with physalin B (2.5-10 μmol/L) induced apoptosis and the cleavage of PARP and caspase-3. Meanwhile, physalin B treatment induced autophagosome formation, and accumulation of LC3-II and p62, but decreased Beclin 1 protein level. Marked changes of microtubules and F-actin microfilaments were observed in physalin B-treated cells, which led to the blockage of co-localization of autophagosomes and lysosomes. Physalin B treatment dose-dependently increased the phosphorylation of p38, ERK and JNK in the cells, whereas the p38 inhibitor SB202190, ERK inhibitor U0126 or JNK inhibitor SP600125 could partially reduce physalin B-induced PARP cleavage and p62 accumulation. Moreover, physalin B treatment dose-dependently increased mito-ROS production in the cells, whereas the ROS scavenger NAC could reverse physalin B-induced effects, including incomplete autophagic response, accumulation of ubiquitinated proteins, changes of microtubules and F-actin, activation of p38, ERK and JNK, as well as cell death and apoptosis.

CONCLUSION

Physalin B induces mito-ROS, which not only inhibits the ubiquitin-proteasome pathway but also induces incomplete autophagic response in HCT116 cells in vitro.

Molecular signalling pathways in canine gliomas

In this study, we determined the expression of key signalling pathway proteins TP53, MDM2, P21, AKT, PTEN, RB1, P16, MTOR and MAPK in canine gliomas using western blotting. Protein expression was defined in three canine astrocytic glioma cell lines treated with CCNU, temozolamide or CPT-11 and was further evaluated in 22 spontaneous gliomas including high and low grade astrocytomas, high grade oligodendrogliomas and mixed oligoastrocytomas. Response to chemotherapeutic agents and cell survival were similar to that reported in human glioma cell lines. Alterations in expression of key human gliomagenesis pathway proteins were common in canine glioma tumour samples and segregated between oligodendroglial and astrocytic tumour types for some pathways. Both similarities and differences in protein expression were defined for canine gliomas compared to those reported in human tumour counterparts. The findings may inform more defined assessment of specific signalling pathways for targeted therapy of canine gliomas.

TPGS2k/PLGA nanoparticles for overcoming multidrug resistance by interfering mitochondria of human alveolar adenocarcinoma cells

In this study, we successfully synthesized d-α-tocopheryl polyethylene glycol 2000 succinate (TPGS2k) and prepared TPGS2k-modified poly(lactic-co-glycolic acid) nanoparticles (TPGS2k/PLGA NPs) loaded with 7-ethyl-10-hydroxycamptothecin (SN-38), designated TPGS2k/PLGA/SN-38 NPs. Characterization measurements showed that TPGS2k/PLGA/SN-38 NPs displayed flat and spheroidal particles with diameters of 80-104 nm. SN-38 was encapsulated in TPGS2k emulsified PLGA NPs with the entrapment efficiency and loading rates of SN-38 83.6 and 7.85%, respectively. SN-38 could release constantly from TPGS2k/PLGA/SN-38 NPs in vitro. TPGS2k/PLGA/SN-38 NPs induced significantly higher cytotoxicity on A549 cells and the multidrug resistance (MDR) cell line (A549/DDP cells and A549/Taxol cells) compared with free SN-38. Further studies on the mechanism of the NPs in increasing the death of MDR cells showed that following the SN-38 releasing into cytoplasm the remaining TPGS2k/PLGA NPs could reverse the P-gp mediated MDR via interfering with the structure and function of mitochondria and rather than directly inhibiting the enzymatic activity of P-gp ATPase. Therefore, TPGS2k/PLGA NPs can reduce the generation of ATP and the release of energy for the requisite of P-gp efflux transporters. The results indicated that TPGS2k/PLGA NPs could become the nanopharmaceutical materials with the capability to reversal MDR and improve anticancer effects of some chemotherapy drugs as P-gp substrates.

A short update on cancer chemoresistance

Chemotherapeutic interventions in cancer patients are limited by the appearance of chemoresistance. For instance, advanced lung and ovarian cancer patients relapse invariably after few cycles of platinum-based chemotherapy. Disseminated tumors are characterized by genetic instability/heterogeneity, thus containing or generating a repertoire of resistant subpopulations. At the cellular level, altered drug uptake, efflux, and metabolization, as well as modifications of drug targets, increased repair, and decreased cell death complement the limited perfusion and adverse hypoxic/acidic extracellular conditions at the tumor level in retaining cancer cell viability. Similarly, targeted therapy is rendered ineffective by mutations of the specific target protein within a few months or years of administration. Assessment of the expression profiles of resistant tumor cells revealed extensive changes in numerous pathways affecting hundreds of genes. Therefore, reversal of drug resistance will require individual profiles of drug resistance mediators and the combination of several specific drugs, targeting critical components to provide new therapeutic options.

Methylation-mediated gene silencing as biomarkers of gastric cancer: A review

Despite a decline in the overall incidence of gastric cancer (GC), the disease remains the second most common cause of cancer-related death worldwide and is thus a significant global health problem. The best means of improving the survival of GC patients is to screen for and treat early lesions. However, GC is often diagnosed at an advanced stage and is associated with a poor prognosis. Current diagnostic and therapeutic strategies have not been successful in decreasing the global burden of the disease; therefore, the identification of reliable biomarkers for an early diagnosis, predictive markers of recurrence and survival and markers of drug sensitivity and/or resistance is urgently needed. The initiation and progression of GC depends not only on genetic alterations but also epigenetic changes, such as DNA methylation and histone modification. Aberrant DNA methylation is the most well-defined epigenetic change in human cancers and is associated with inappropriate gene silencing. Therefore, an increasing number of genes methylated at the promoter region have been targeted as possible biomarkers for different purposes, including early detection, classification, the assessment of the tumor prognosis, the development of therapeutic strategies and patient follow-up. This review article summarizes the current understanding and recent evidence regarding DNA methylation markers in GC with a focus on the clinical potential of these markers.

Gene signatures of drug resistance predict patient survival in colorectal cancer

Different combinations of 5-fluorouracil (5-FU), oxaliplatin, irinotecan and other newly developed agents have been used to treat colorectal cancer. Despite the advent of new treatment regimens, the 5-year survival rate for metastatic colorectal cancer remains low (~10%). Knowing the drug sensitivity of a given tumor for a particular agent could significantly impact decision making and treatment planning. Biomarkers are proven to be successful in characterizing patients into different response groups. Using survival prediction analysis, we have identified three independent gene signatures, which are associated with sensitivity of colorectal cancer cells to 5-FU, oxaliplatin or irinotecan. On the basis of the three gene signatures, three score systems were developed to stratify patients from sensitive to resistance. These score systems exhibited robustness in stratify patients in two independent clinical studies. Patients with high scores in all three drugs exhibited the lowest survival.

Enhanced anti-colorectal cancer effects of carfilzomib combined with CPT-11 via downregulation of nuclear factor-κB in vitro and in vivo

Upregulation of nuclear factor-κB (NF-κB) in colorectal carcinoma (CRC) accelerates tumor growth, whereas, irinotecan (CPT-11)-induced NF-κB activation reduces chemosensitivity and weakens the anti-colorectal cancer function itself, while proteasome inhibitors can inhibit NF-κB and improve the effect of chemotherapy. Carfilzomib (CFZ) is a novel proteasome inhibitor that has been recently approved by the FDA and is in clinical use for the treatment of multiple myeloma, but little is known about its activity against CRC. The aim of the present study was to explore whether CFZ alone or in combination with CPT-11 is effective in CRC treatment. We evaluated the novel therapeutic ability and mechanism of action of CFZ in CRC in vitro and in vivo. SW620 cells were incubated with CFZ alone or in combination with CPT-11. Cell proliferation was assessed by WST-1 and clonogenic assays, the cytotoxic interaction was assessed with a combination index (CI). Cell cycle progression was analysed with flow cytometry. Cell apoptosis was evaluated by detecting the Annexin V/propidium iodide (PI) ratio, caspase 3 and CD95 expression, and with TUNEL staining. Cell migration and invasion was determined with a wound-healing assay and a Transwell matrix penetration assay. A CRC xenograft model was established to monitor tumor growth. EMSA was used to analyse NF-κB activation and western blot analysis was used to detect the protein levels of related signaling factors. CFZ significantly inhibited the growth of SW620 cells, and had synergistic inhibitory effects with CPT-11 on survival and colony formation; possibly by inhibition of NF-κB activation, MEK/ERK and PI3K/AKT pathway factor dephosphorylation and survivin downregulation. Co-administration of CFZ and CPT-11 induced G2/M arrest, increased p21WAF1/CIP, and decreased mutant p53 and cdc25c expression. Induction of apoptosis was accompanied by marked increases in PARP cleavage, caspase 3 activation, an increase of CD95 and p-p38, and ATF3 activation. Combination treatment lowered the invasive and migration ability of SW620 cells, reduced MMP and increased TIMP protein expression. Finally, co-administration of CFZ and CPT-11 suppressed tumor growth and increased apoptosis compared with single-agent treatment in SW620 xenograft models correlated with NF-κB downregulation. Carfilzomib alone or in combination with CPT-11 is effective against colorectal cancer through inhibition of multiple mechanisms related to NF-κB, and could be a potential novel therapy for CRC.

Cetuximab increases concentrations of irinotecan and of its active metabolite SN-38 in plasma and tumour of human colorectal carcinoma-bearing mice

In a previous study, we showed that cetuximab, a monoclonal antibody directed towards epidermal growth factor receptor, could inhibit P-glycoprotein (P-gp), an efflux protein of ATP-binding cassette family, and lead to an increased P-gp substrate intracellular concentration. Cetuximab is given with irinotecan to patients with metastasis colorectal cancer who did not respond to irinotecan-based therapy. The mechanism of this successful clinical reversion remains unknown. As irinotecan is a P-gp substrate, we tested here whether cetuximab could modify irinotecan concentration in mice. Therefore, concentrations of irinotecan and of its active metabolite SN-38 were measured by HPLC in plasma and tumour of mice bearing a human colorectal carcinoma xenograft when irinotecan is given orally alone or after a pretreatment with cetuximab. Pharmacokinetic analysis showed no significant modification of irinotecan concentrations but a significant increase (1.7-fold) in SN-38 AUCs in plasma and in tumour after a pretreatment with cetuximab. Those results suggest that cetuximab influence irinotecan distribution into tissues probably due to inhibition of P-gp. As SN-38 is 200-fold more potent than irinotecan, cetuximab could reverse irinotecan resistance by an effect on its active metabolite. Inhibiting SN-38 efflux by P-gp drug transporters in biliary system and tumour can lead to pharmacokinetic modification and a higher anticancer efficacy.

Addition of propolis to irinotecan therapy prolongs survival in ehrlich ascites tumor-bearing mice

We investigated possible synergistic action of anticancer drug Irinotecan (IRI) combined with ethanolic (EEP) and water-soluble (WSDP) derivate of propolis on Swiss albino mice injected with Ehrlich ascites tumor (EAT). For survival analysis mice were administered WSDP and EEP (100 mg/kg) daily for 3 consecutive days, beginning on 3rd day after EAT cell (1×10⁶) injection. IRI was administered at a dose of 50 mg/kg on days 1, 13, and 19. We simultaneously studied peripheral white blood cell count, cell types washed from the peritoneal cavity, functional activity of macrophages from peritoneal cavity, and the level of primary DNA damage in leukocytes, kidney, and liver cells using the alkaline comet assay. Three out of 9 mice per group survived the entire duration of the experiment (90 days) in groups treated with IRI combined with WSDP and EEP. All test components increased survival of mice by 7.53% to 231.54%. Combined treatment with IRI and/or WSDP and EEP significantly decreased percentage of tumor cells in the peritoneal cavity as compared to nontreated EAT-injected mice. All treated animals had significantly higher percentage of neutrophils in the peritoneal cavity in comparison to nontreated EAT-injected mice. We observed significantly higher value of DNA damage in leukocytes of mice treated with IRI and combination of IRI and/or WSDP and EEP as compared to nontreated EAT-injected mice, while the same treatment decreased DNA damage in kidney. Our results showed that addition of propolis to IRI treatment enhanced antitumor activity of IRI and prolongs survival in EAT-bearing mice, which definitely deserve further studies to clarify the possible mechanisms of antitumor actions of combined herb-drug treatments.

Management of two cases of recurrent anal carcinoma

Due to the low incidence of anal cancer and generally high cure rates, few second-line treatment options have been evaluated in the setting of formal clinical trials. We briefly report two cases that were both found to have wild-type K-RAS, with no epidermal growth factor receptor amplification or evidence of prior persistent human papilloma virus infection. Both cases were treated with irinotecan and cetuximab with evidence of clinical benefit in the setting of a third recurrence, as well as evidence of response to other strategies employed in their management. These cases provide support for the suggestion that treatment planning in conjunction with molecular profiling may be beneficial in such uncommon clinical settings.

ATP citrate lyase mediates resistance of colorectal cancer cells to SN38

Combination chemotherapy is standard for metastatic colorectal cancer; however, nearly all patients develop drug resistance. Understanding the mechanisms that lead to resistance to individual chemotherapeutic agents may enable identification of novel targets and more effective therapy. Irinotecan is commonly used in first- and second-line therapy for patients with metastatic colorectal cancer, with the active metabolite being SN38. Emerging evidence suggests that altered metabolism in cancer cells is fundamentally involved in the development of drug resistance. Using Oncomine and unbiased proteomic profiling, we found that ATP citrate lyase (ACLy), the first-step rate-limiting enzyme for de novo lipogenesis, was upregulated in colorectal cancer compared with its levels in normal mucosa and in chemoresistant colorectal cancer cells compared with isogenic chemo-naïve colorectal cancer cells. Overexpression of exogenous ACLy by lentivirus transduction in chemo-naïve colorectal cancer cells led to significant chemoresistance to SN38 but not to 5-fluorouracil or oxaliplatin. Knockdown of ACLy by siRNA or inhibition of its activity by a small-molecule inhibitor sensitized chemo-naïve colorectal cancer cells to SN38. Furthermore, ACLy was significantly increased in cancer cells that had acquired resistance to SN38. In contrast to chemo-naïve cells, targeting ACLy alone was not effective in resensitizing resistant cells to SN38, due to a compensatory activation of the AKT pathway triggered by ACLy suppression. Combined inhibition of AKT signaling and ACLy successfully resensitized SN38-resistant cells to SN38. We conclude that targeting ACLy may improve the therapeutic effects of irinotecan and that simultaneous targeting of ACLy and AKT may be warranted to overcome SN38 resistance.

Sorafenib overcomes irinotecan resistance in colorectal cancer by inhibiting the ABCG2 drug-efflux pump

Despite recent advances in the treatment of colorectal cancer (CRC), tumor resistance is a frequent cause of chemotherapy failure. Therefore, new treatment options are needed to improve survival of patients with irinotecan-refractory CRCs, particularly those bearing KRAS mutations that preclude the use of anti-EGFR therapies. In this study, we investigated whether sorafenib could reverse irinotecan resistance, thereby enhancing the therapeutic efficacy of routinely used irinotecan-based chemotherapy. We used both in vitro (the HCT116, SW48, SW620, and HT29 colon adenocarcinoma cell lines and four SN-38-resistant HCT-116 and SW48 clones) and in vivo models (nude mice xenografted with SN-38-resistant HCT116 cells) to test the efficacy of sorafenib alone or in combination with irinotecan or its active metabolite, SN-38. We have shown that sorafenib improved the antitumoral activity of irinotecan in vitro, in both parental and SN-38-resistant colon adenocarcinoma cell lines independently of their KRAS status, as well as in vivo, in xenografted mice. By inhibiting the drug-efflux pump ABCG2, sorafenib favors irinotecan intracellular accumulation and enhances its toxicity. Moreover, we found that sorafenib improved the efficacy of irinotecan by inhibiting the irinotecan-mediated p38 and ERK activation. In conclusion, our results show that sorafenib can suppress resistance to irinotecan and suggest that sorafenib could be used to overcome resistance to irinotecan-based chemotherapies in CRC, particularly in KRAS-mutated tumors.

Single-antibody, targeted nanoparticle delivery of camptothecin

We have developed a new method for assembling targeted nanoparticles that utilizes the complexation between targeting agents that contain boronic acids and polymer-drug conjugates that possess diols. Here, we report the first in vivo, antitumor results of a nanoparticle formed via this new assembly methodology. A nanoparticle consisting of a mucic acid polymer conjugate of camptothecin (CPT), MAP-CPT, and containing on average one Herceptin antibody is investigated in nude mice bearing HER2 overexpressing BT-474 human breast cancer tumors. Nontargeted MAP-CPT and antibody-containing MAP-CPT nanoparticles of ca. 30-40 nm diameter and slightly negative zeta potential show prolonged in vivo circulation and similar biodistributions after intravenous tail vein injections in mice. The maximum tolerated dose (MTD) of the nontargeted and Herceptin-containing MAP-CPT nanoparticles is found to be 10 and 8 mg of CPT/kg, respectively, in mice. Mice bearing BT-474 human breast tumors treated with nontargeted MAP-CPT nanoparticles at 8 mg of CPT/kg show significant tumor growth inhibition (mean tumor volume of 63 mm(3)) when compared to irinotecan at 80 mg/kg (mean tumor volume of 575 mm(3)) and CPT at 8 mg/kg (mean tumor volume of 808 mm(3)) at the end of the study. Herceptin antibody treatment at 5.9 mg/kg results in complete tumor regressions in 5 out of 8 mice, with a mean tumor volume of 60 mm(3) at the end of the study. Mice treated with MAP-CPT nanoparticles at 1 mg of CPT/kg do not show tumor inhibition. However, all mice receiving administrations of MAP-CPT nanoparticles (1 mg of CPT/kg) that contain on average a single Herceptin molecule per nanoparticle (5.9 mg of Herceptin equivalent/kg) show complete tumor regression by the end of the study. These results demonstrate that the antitumor efficacy of nanoparticles carrying anticancer drugs can be enhanced by incorporating on average a single antibody.

A three-gene signature as potential predictive biomarker for irinotecan sensitivity in gastric cancer

Objective

Personalized chemotherapy based on molecular biomarkers can maximize anticancer efficiency. We aim to investigate predictive biomarkers capable of predicting response to irinotecan-based treatment in gastric cancer.

Methods

We examined gene expression of APTX, BRCA1, ERCC1, ISG15, Topo1 and methylation of SULF2 in formalin-fixed paraffin-embedded gastric cancer tissues from 175 patients and evaluated the association between gene expression levels or methylation status and in vitro sensitivity to irinotecan. We used multiple linear regression analysis to develop a gene-expression model to predict irinotecan sensitivity in gastric cancer and validated this model in vitro and vivo.

Results

Gene expression levels of APTX, BRCA1 and ERCC1 were significantly lower in irinotecan-sensitive gastric cancer samples than those irinotecan-resistant samples (P < 0.001 for all genes), while ISG15 (P = 0.047) and Topo1 (P = 0.002) were significantly higher. Based on those genes, a three-gene signature were established, which was calculated as follows: Index =0.488 - 0.020× expression level of APTX + 0.015× expression level of Topo1 - 0.011 × expression level of BRCA1. The three-gene signature was significantly associated with irinotecan sensitivity (rho = 0.71, P < 0.001). The sensitivity and specificity for the prediction of irinotecan sensitivity based on the three-gene signature reached 73% and 86%, respectively. In another independent testing set, the irinotecan inhibition rates in gastric samples with sensitive-signature were much higher than those with resistant-signature (65% vs. 22%, P < 0.001). Irinotecan therapy with 20 mg/kg per week to immunodeficient mice carrying xenografts with sensitive-signature dramatically arrested the growth of tumors (P < 0.001), but had no effect on mice carrying xenografts with resistant-signature.

Conclusions

The three-gene signature established herein is a potential predictive biomarker for irinotecan sensitivity in gastric cancer.

Bugs and drugs: oncolytic virotherapy in combination with chemotherapy

Single agent therapies are rarely successful in treating cancer, particularly at metastatic or end stages, and survival rates with monotherapies alone are generally poor. The combination of multiple therapies to treat cancer has already driven significant improvements in the standard of care treatments for many types of cancers. The first combination treatments exploited for cancer therapy involved the use of several cytotoxic chemotherapy agents. Later, with the development of more targeted agents, the use of novel, less toxic drugs, in combination with the more classic cytotoxic drugs has proven advantageous for certain cancer types. Recently, the combination of oncolytic virotherapy with chemotherapy has shown that the use of these two therapies with very distinct anti-tumor mechanisms may also lead to synergistic interactions that ultimately result in increased therapeutic effects not achievable by either therapy alone. The mechanisms of synergy between oncolytic viruses (OVs) and chemotherapeutic agents are just starting to be elucidated. It is evident, however, that the success of these OV-drug combinations depends greatly on the particular OV, the drug(s) selected, and the cancer type targeted. This review summarizes the different OV-drug combinations investigated to date, including the use of second generation armed OVs, which have been studied with the specific purpose of generating synergistic interactions with particular chemotherapy agents. The known mechanisms of synergy between these OV-drug combinations are also summarized. The importance of further investigating these mechanisms of synergy will be critical in order to maximize the therapeutic efficacy of OV-drug combination therapies in the future.

Mechanisms and insights into drug resistance in cancer

Cancer drug resistance continues to be a major impediment in medical oncology. Clinically, resistance can arise prior to or as a result of cancer therapy. In this review, we discuss different mechanisms adapted by cancerous cells to resist treatment, including alteration in drug transport and metabolism, mutation and amplification of drug targets, as well as genetic rewiring which can lead to impaired apoptosis. Tumor heterogeneity may also contribute to resistance, where small subpopulations of cells may acquire or stochastically already possess some of the features enabling them to emerge under selective drug pressure. Making the problem even more challenging, some of these resistance pathways lead to multidrug resistance, generating an even more difficult clinical problem to overcome. We provide examples of these mechanisms and some insights into how understanding these processes can influence the next generation of cancer therapies.

Identification of cetrimonium bromide and irinotecan as compounds with synthetic lethality against NDRG1 deficient prostate cancer cells

The N-myc downstream regulated gene 1 (NDRG1) has been identified as a metastasis-suppressor gene in prostate cancer (PCa). Compounds targeting PCa cells deficient in NDRG1 could potentially decrease invasion/metastasis of PCa. A cell based screening strategy was employed to identify small molecules that selectively target NDRG1 deficient PCa cells. DU-145 PCa cells rendered deficient in NDRG1 expression by a lentiviral shRNA-mediated knockdown strategy were used in the primary screen. Compounds filtered from the primary screen were further validated through proliferation and clonogenic survival assays in parental and NDRG1 knockdown PCa cells. Screening of 3360 compounds revealed irinotecan and cetrimonium bromide (CTAB) as compounds that exhibited synthetic lethality against NDRG1 deficient PCa cells. A three-dimensional (3-D) invasion assay was utilized to test the ability of CTAB to inhibit invasion of DU-145 cells. CTAB was found to remarkably decrease invasion of DU-145 cells in collagen matrix. Our results suggest that CTAB and irinotecan could be further explored for their potential clinical benefit in patients with NDRG1 deficient PCa.

Panitumumab combined with irinotecan for patients with KRAS wild-type metastatic colorectal cancer refractory to standard chemotherapy: a GERCOR efficacy, tolerance, and translational molecular study

BACKGROUND

The purpose of this study was to evaluate the combination of panitumumab and irinotecan in patients with KRAS wild-type metastatic colorectal cancer refractory to standard chemotherapy (oxaliplatin, fluoropyrimidines-irinotecan and bevacizumab).

PATIENTS AND METHODS

KRAS status was first determined locally but subsequent validation of KRAS status and additional screenings (rare KRAS, NRAS, BRAF mutations and EGFR copy number) were centrally assessed. Patients received panitumumab (6 mg/kg) and irinotecan (180 mg/m²) every 2 weeks.

RESULTS

Sixty-five eligible patients were analyzed. The objective response rate (ORR) was 29.2% [95% confidence interval (95% CI) 18.2-40.3]. Median progression-free and overall survivals were 5.5 and 9.7 months, respectively. Most frequent grade 3/4 toxic effects were skin 32.3%, diarrhea 15.4% and neutropenia 12.3%. Tissue samples were available for 60 patients. For the confirmed KRAS wild-type population codon 12 or 13 mutation (n = 54), ORR was 35.2% (95% CI 22.4.1-47.9). Thirteen patients had a NRAS, a BRAF or a rare KRAS mutation, and no tumor response was observed in this subgroup when compared with 46.3% (95% CI 31.1-61.6) ORR in the subgroup of 41 patients with no identified mutation.

CONCLUSION

Panitumumab and irinotecan is an active third-line regimen in a well-defined population based on biomarkers. ClinicalTrials.gov Identifier NCT00655499.

In vivo real-time imaging of chemotherapy response on the liver metastatic tumor microenvironment using multiphoton microscopy

In vivo real-time visualization of chemotherapy response at the cellular level provides us with direct evidence of what happens on the tumor microenvironment of metastatic organs. We imaged the response of metastatic tumor cells and host stromal cells to chemotherapeutics on liver metastatic xenografts in living mice using intravital two-photon laser scanning microscopy (TPLSM). Red fluorescent protein-expressing human colorectal cancer cells (HT29) was inoculated to the spleen of green fluorescent protein-expressing nude mice. 5-Fluorouracil or irinotecan was intraperitoneally administered after the formation of macroscopic liver metastases. Intravital TPLSM was performed at multiple time-points for time-series imaging of liver metastatic xenografts in the same mice. Under the 1st TPLSM, HT29 cells were visualized in hepatic sinusoids at the single cell level. Liver metastatic nodules consisting of viable cancer cells and surrounding stroma with tumor vessels were visualized under the 2nd TPLSM. After chemotherapy, tumor cell fragmentation, condensation, swelling and intracellular vacuoles were observed under the 3rd TPLSM. There was no obvious morphological difference in tumor response between these chemotherapeutics. Time-series intravital TPLSM imaging on the metastatic tumor xenografts may be useful for screening and evaluating new chemotherapeutics with less interindividual variability.