Irinotecan In Colorectal Cancer Research Articles

The effective combination therapies with irinotecan for colorectal cancer.

Colorectal cancer is the third most common type of cancer worldwide and has become one of the major human disease burdens. In clinical practice, the treatment of colorectal cancer has been closely related to the use of irinotecan. Irinotecan combines with many other anticancer drugs and has a broader range of drug combinations. Combination therapy is one of the most important means of improving anti-tumor efficacy and overcoming drug resistance. Reasonable combination therapy can lead to better patient treatment options, and inappropriate combination therapy will increase patient risk. For the colorectal therapeutic field, the significance of combination therapy is to improve the efficacy, reduce the adverse effects, and improve the ease of treatment. Therefore, we explored the clinical advantages of its combination therapy based on mechanism or metabolism and reviewed the rationale basis and its limitations in conducting exploratory clinical trials on irinotecan combination therapy, including the results of clinical trials on the combination potentiation of cytotoxic drugs, targeted agents, and herbal medicine. We hope that these can evoke more efforts to conduct irinotecan in the laboratory for further studies and evaluations, as well as the possibility of more in-depth development in future clinical trials.

Delivery of Anticancer Drugs Using Microbubble-Assisted Ultrasound in a 3D Spheroid Model.

Tumor spheroids are promising three-dimensional (3D) in vitro tumor models for the evaluation of drug delivery methods. The design of noninvasive and targeted drug methods is required to improve the intratumoral bioavailability of chemotherapeutic drugs and reduce their adverse off-target effects. Among such methods, microbubble-assisted ultrasound (MB-assisted US) is an innovative modality for noninvasive targeted drug delivery. The aim of the present study is to evaluate the efficacy of this US modality for the delivery of bleomycin, doxorubicin, and irinotecan in colorectal cancer (CRC) spheroids. MB-assisted US permeabilized the CRC spheroids to propidium iodide, which was used as a drug model without affecting their growth and viability. Histological analysis and electron microscopy revealed that MB-assisted US affected only the peripheral layer of the CRC spheroids. The acoustically mediated bleomycin delivery induced a significant decrease in CRC spheroid growth in comparison to spheroids treated with bleomycin alone. However, this US modality did not improve the therapeutic efficacy of doxorubicin and irinotecan on CRC spheroids. In conclusion, this study demonstrates that tumor spheroids are a relevant approach to evaluate the efficacy of MB-assisted US for the delivery of chemotherapeutics.

Translational Pharmacokinetic/Pharmacodynamic Modeling and Simulation of Oxaliplatin and Irinotecan in Colorectal Cancer.

Despite the recent advances in this field, there are limited methods for translating organoid-based study results to clinical response. The goal of this study was to develop a pharmacokinetic/pharmacodynamic (PK/PD) model to facilitate the translation, using oxaliplatin and irinotecan treatments with colorectal cancer (CRC) as examples. The PK models were developed using qualified oxaliplatin and irinotecan PK data from the literature. The PD models were developed based on antitumor efficacy data of SN-38 and oxaliplatin evaluated in vitro using tumor organoids. To predict the clinical response, translational scaling of the models was established by incorporating predicted ultrafiltration platinum in plasma or SN-38 in tumors to PD models as the driver of efficacy. The final PK/PD model can predict PK profiles and responses following treatments with oxaliplatin or irinotecan. After generation of virtual patient cohorts, this model simulated their tumor shrinkages following treatments, which were used in analyzing the efficacies of the two treatments. Consistent with the published clinical trials, the model simulation suggested similar patient responses following the treatments of oxaliplatin and irinotecan with regards to the probabilities of progression-free survival (HR = 1.05, 95%CI [0.97;1.15]) and the objective response rate (OR = 1.15, 95%CI [1.00;1.32]). This proposed translational PK/PD modeling approach provides a significant tool for predicting clinical responses of different agents, which may help decision-making in drug development and guide clinical trial design.

The efficacy and side effects of rigosertib combined with chemotherapy in KRAS mutant colorectal cancer mice

Objective: To investigate the effect of rigosertib (RGS) combined with classic chemotherapy drugs including 5-fluorouracil, oxaliplatin, and irinotecan in colorectal cancer. Methods: Explore the synergy effects of RGS and 5-fluorouracil (5-FU), oxaliplatin (OXA), and irinotecan (IRI) on colorectal cancer by subcutaneously transplanted tumor models of mice. The mice were randomly divided into control group, RGS group, 5-FU group, OXA group, IRI group, 5-FU+ RGS group, OXA+ RGS group and IRI+ RGS group. The synergy effects of RGS and OXA on KRAS mutant colorectal cancer cell lines in vitro was detected by CCK-8. Ki-67 immunohistochemistry and TdT-mediated dUTP nick-end labeling (TUNEL) staining were performed on the mouse tumor tissue sections, and the extracted tumor tissue was analyzed by western blot. The blood samples of mice after chemotherapy and RGS treatment were collected, blood routine and liver and kidney function analysis were conducted, and H&E staining on liver sections was performed to observe the side effects of chemotherapy and RGS. Results: The subcutaneously transplanted tumor models were established successfully in all groups. 55 days after administration, the fold change of tumor size of OXA+ RGS group was 37.019±8.634, which is significantly smaller than 77.571±15.387 of RGS group (P=0.029) and 92.500±13.279 of OXA group (P=0.008). Immunohistochemical staining showed that the Ki-67 index of tumor tissue in control group, OXA group, RGS group and OXA+ RGS group were (100.0±16.8)%, (35.6±11.3)%, (54.5±18.1)% and (15.4±3.9)%, respectively. The Ki-67 index of OXA+ RGS group was significantly lower than that in control group (P=0.014), but there was no significant difference compared to OXA group and RGS group (OXA: P=0.549; RGS: P=0.218). TUNEL fluorescence staining showed that the apoptotic level of OXA+ RGS group was 3.878±0.547, which was significantly higher than 1.515±0.442 of OXA group (P=0.005) and 1.966±0.261 of RGS group (P=0.008). Western blot showed that the expressions of apoptosis related proteins such as cleaved-PARP, cleaved-caspase 3 and cleaved-caspase 8 in the tumor tissues of mice in the OXA+ RGS group were higher than those in control group, OXA group and RGS group. After the mice received RGS combined with chemotherapy drugs, there was no significant effect on liver and kidney function indexes, but the combined use of oxaliplatin and RGS significantly reduced the white blood cells [(0.385±0.215)×10(9)/L vs (5.598±0.605)×10(9)/L, P<0.001] and hemoglobin[(56.000±24.000)g/L vs (153.333±2.231)g/L, P=0.001] of the mice. RGS, chemotherapy combined with RGS and chemotherapy alone did not significantly increase the damage to liver cells. Conclusions: The combination of RGS and oxaliplatin has a stronger anti-tumor effect on KRAS mutant colorectal cancer. RGS single agent will not cause significant bone marrow suppression and hepatorenal injury in mice, but its side effects may increase correspondingly after combined with chemotherapy.

Establishment and Characterization of an Irinotecan-Resistant Human Colon Cancer Cell Line.

Colorectal cancer (CRC) is a leading cause of cancer-related deaths worldwide. Irinotecan is widely used as a chemotherapeutic drug to treat CRC. However, the mechanisms of acquired resistance to irinotecan in CRC remain inconclusive. In the present study, we established a novel irinotecan-resistant human colon cell line to investigate the underlying mechanism(s) of irinotecan resistance, particularly the overexpression of ABC transporters. The irinotecan-resistant S1-IR20 cell line was established by exposing irinotecan to human S1 colon cancer cells. MTT cytotoxicity assay was carried out to determine the drug resistance profile of S1-IR20 cells. The drug-resistant cells showed about 47-fold resistance to irinotecan and cross-resistance to ABCG2 substrates in comparison with S1 cells. By Western blot analysis, S1-IR20 cells showed significant increase of ABCG2, but not ABCB1 or ABCC1 in protein expression level as compared to that of parental S1 cells. The immunofluorescence assay showed that the overexpressed ABCG2 transporter is localized on the cell membrane of S1-IR20 cells, suggesting an active efflux function of the ABCG2 transporter. This finding was further confirmed by reversal studies that inhibiting efflux function of ABCG2 was able to completely abolish drug resistance to irinotecan as well as other ABCG2 substrates in S1-IR20 cells. In conclusion, our work established an in vitro model of irinotecan resistance in CRC and suggested ABCG2 overexpression as one of the underlying mechanisms of acquired resistance to irinotecan. This novel resistant cell line may enable future studies to overcome drug resistance in vitro and improve CRC treatment in vivo.

483P The autophagy-depended PXR regulation in colorectal cancer

Colorectal cancer (CRC) is one of the most frequently diagnosed malignancies worldwide. Although chemotherapy represents an effective anti-tumour therapeutic approach for CRC, drug treatment efficacy is often limited due to the development of resistant cancer cells. Several studies associate the pregnane X receptor (PXR) and autophagy with resistance to chemotherapeutic drugs. This study aims to investigate the relationship between mtKRAS- dependent autophagy and PXR expression after treatment with irinotecan in CRC.

Comparison of Capox and Folfox with or Without Irinotecan in Colorectal Cancer

Comparison of Capox and Folfox with or Without Irinotecan in Colorectal Cancer

Abstract 1188: Sodium phenylbutyrate has an antineoplastic effect and enhances the cytotoxicity of 5-fluorouracil and irinotecan in colorectal cancer cell lines

Abstract Colorectal cancer is the third most common cancer in the world and it is the second leading cause of cancer-related deaths in the United States. About 25% of colorectal cancer cases present with metastases at time of diagnosis and 50% of patients who undergo surgery will ultimately develop metastatic disease. Consequently, adjuvant chemotherapy is required in many cases and it aims to prevent tumor progression and metastasis. Resistance to chemotherapy is the biggest obstacle in the treatment path of advanced colorectal cancer. Thus, highlighting the urgent need for the identification of new therapeutic agents that can enhance the cytotoxicity of the currently approved anticancer drugs. Sodium phenylbutyrate (NaPB), a salt of a short chain fatty acid that is used for treatment of urea cycle disorders, is under investigation for its antineoplastic potential. NaPB acts as a histone deacetylase inhibitor and it has been shown to be associated with reduced ER stress and enhanced JNK signaling pathway. This indicates that NaPB may enhance the cytotoxicity of the currently approved agents for colorectal cancer including oxaliplatin, 5-fluorouracil, and irinotecan. The aims of this study were to identify the antineoplastic potential of NaPB in colorectal cell lines, and to identify its effect on the cytotoxicity of oxaliplatin, 5-fluorouracil, and irinotecan. MTT proliferation assay showed that NaPB possessed a concentration dependent killing effect against HCT-116 and HT-29 colorectal cancer cell line (IC50 values were 5 and 10 mM respectively). Moreover, at clinically achievable and nontoxic concentration (2.5 mM), NaPB showed a synergistic effect in HCT-116 on 5-fluorouracil (R=14.176, p=0.006), on irinotecan (R=53.86, p=0.0117), and on oxaliplatin (R=20, p=0.004), but resulted in extensive cytotoxicity when used at 5 mM and 10 mM. In HT-29 cells, NaPB at concentrations 5 mM and 10 mM, showed a synergistic effect on 5-fluorouracil (R=5.5, p&amp;lt;0.001; and R=125, p&amp;lt;0.001 respectively), on irinotecan (R=5.7, p=0.016; and R=21.3, p=0.018 respectively), and on oxaliplatin (R=2.4, p=0.003; and R=3, p=0.002 respectively). The addition of NaPB at concentration of 20 mM to the previous drugs resulted in profound cytotoxic effect toward HT-29 cells. As a conclusion, NaPB is a promising new adjuvant antineoplastic agent that can be used to enhance the cytotoxicity of 5-fluorouracil, irinotecan, and oxaliplatin in colorectal cancer. Citation Format: Maha Al-Keilani, Ruba Darweesh. Sodium phenylbutyrate has an antineoplastic effect and enhances the cytotoxicity of 5-fluorouracil and irinotecan in colorectal cancer cell lines [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1188. doi:10.1158/1538-7445.AM2017-1188

Highlights of This Issue

Metabolomics captures the interactions between genetic alterations, enzymatic activity, and metabolic reactions. Here, comparative mass spectrometry-based metabolomics was performed using matched frozen and fixed isogenic prostate cancer cells and clinical specimens. A sufficient number of metabolites were retained in formalin-fixed, paraffin-embedded (FFPE) tissue to allow unsupervised hierarchical clustering of cell populations. This metabolomic profiling approach creates the opportunity, for research and diagnostic purposes, to interrogate annotated tumor banks retrospectively and link metabolomics with clinicopathologic endpoints. Combined, metabolic profiling to discover and validate metabolism-based diagnostic, prognostic or predictive biomarkers in archival diagnostic tissue adds a new, powerful technology for precision medicine.A critical aspect of metastatic epithelial ovarian cancer (EOC) is tumor cell dormancy, rendering these cells resistant to chemotherapeutics. Employing a systematic approach to analyze the role of negative growth factors, MacDonald and colleagues demonstrate that disruption of the DP, RB family, E2F, and MuvB complex (DREAM) results in death of EOC cells. Specifically, loss of the DREAM assembly factor Dyrk1A, or the DREAM component p130, impairs repression of DREAM target genes, leads to continued DNA synthesis, and is coincident with increased cell death. Importantly, chemical inhibition of Dyrk1A synergizes with conventional chemotherapies to kill EOC cells under dormant conditions.The basis of resistance or sensitivity to irinotecan in colorectal cancer has still not been clearly established. Strategies to identify susceptible patients and targetable pathways to reverse resistance are urgently needed. Cabal-Hierro and O’Dwyer highlight a role for RIP1 kinase in SN38 sensitivity by mediating cell death/DNA damage signaling in colon adenocarcinoma model systems through the TNF/TNFR pathway. Downregulation of RIP1 protects from SN-38 in vitro and in vivo, suggesting that RIP1 has potential as a biomarker. Activation of TNF/TNFR signaling potentiates SN38 activity in a RIP1-dependent manner; thus, suggesting a re-evaluation of TNF-based interventions to enhance treatment efficacy.Early metastasis and therapeutic resistance are huge setbacks to patients diagnosed with pancreatic ductal adenocarcinoma (PDAC). Here, Smigiel and colleagues report a unique function of the tumor microenvironment (TME) cytokine oncostatin M (OSM) in inducing epithelial-mesenchymal transition (EMT) and cancer stem cell (CSC) properties in pancreatic cancer cells. Elevated levels of OSM in PDAC induce EMT transcription factors ZEB1 and Snail, and induce CD44+ CSC that are more migratory, tumorigenic, highly metastatic and resistant to gemcitabine. As such, targeting OSM or OSM-signaling in PDAC is a potential therapeutic strategy to prevent de novo acquisition of CSC properties such as drug resistance and metastasis.

Statistical analysis of episensitization using transition probability functions and PFS2 for “ROCKET”, a two stage phase II study of RRx-001, a multi-epigenetic agent, investigating resensitization to irinotecan in colorectal cancer.

TPS775 Background: The development of resistance to chemotherapies in cancer leads to disease progression resulting in impaired survival. RRx-001, a ROS-mediated DNMT and HDAC inhibitor, may resensitize patients to previously effective, now refractory therapies, improving survival. A randomized two-stage Phase 2 trial of RRx-001 vs regorafenib (ROCKET) is underway to assess the impact of resensitization to irinotecan on overall survival in irinotecan refractory tumors. Transition Probability Functions (TPF) using Markov Chains have previously been used in clinical trials and provide a powerful tool for resensitization analysis. Methods: Patients with metastatic colorectal cancer who previously responded, then progressed on irinotecan-based therapies, with or without bevacizumab, cetuximab or panitumumab and an ECOG PS 0-1 are randomized to receive RRx-001 1x/week or regorafenib until progression or unacceptable toxicity in Stage 1. Patients then advance to Stage 2 to receive irinotecan-based therapies. This trial is designed to detect an increase in median OS of 3 mo., corresponding to a 33% reduction in risk of death. The primary endpoint, overall survival (OS), employs a two-sided log-rank test to compare treatment groups. The hazard ratio and its 95% CI are derived from the Cox proportional hazards model. Kaplan-Meier survival curve estimates are graphically depicted by treatment group. Secondary endpoints include PFS, PFS2 and Transition Probability Functions to address the resensitization hypothesis, KRAS or p53 status dependence. The analysis of PFS2, defined as time to progression (or death) from randomization to progression in Stage 2 (post Irinotecan therapy) is a key secondary endpoint and its analysis uses the standard two-sided log-rank test. TPF estimates will be derived from the Markov Chain transition probability matrix. The study should provide compelling evidence in support of the ability to return to previously beneficial chemotherapy treatment. Recruitment is ongoing. Clinical trial information: NCT02096354.

Abstract A15: Humanized anti-hepatocyte growth factor (HGF) antibody, suppresses innate irinotecan resistance induced by fibroblast-derived HGF in colon cancer cells

Abstract Background and Purpose: Preclinical and clinical findings indicate that multiple tumor micro-environmental factors, including growth factors, protect solid tumors from therapeutic interventions. Experimental evidence has clarified some of the resistance mechanisms, which have led to the development of innovative approaches to treat cancer. Irinotecan is a semi-synthetic derivative of camptothecin, originally isolated from the Chinese/Tibetan ornamental tree Camptothecaacuminata. It is a key component of the first- and second-line treatment regimens for metastatic colorectal cancer (CRC). Study of irinotecan has demonstrated that its efficacy to treat cancer is superior to that of the best supportive care. However, de novo or acquired clinical resistance to camptothecins still exists expecting new target. The hepatocyte growth factor (HGF)/c-Met signaling system is known to be implicated in the development and progression of CRC, but the relationship between the expressions of HGF or c-MET and clinicopathologic feature remains controversial. We hypothesized that HGF from cancer-associated fibroblast (CAF) is related to innate irinotecan resistance. Therefore, HGF deprivation using neutralizing antibody is promising strategy to overcome irinotecan resistance induced by HGF in CRC. Results: We postulated that innate drug resistance might be caused at least in part by factors secreted by the tumor stromal cells. We measured the levels of mRNA and secreted protein of HGF by real-time PCR and ELISA in fibroblast and CRC cell lines. The mRNA level of HGF was significantly higher in fibroblast than CRC cell lines. Also, secreted HGF was not detected in conditioned media (CM) from CRC cell, but was detected in CM from fibroblast. Fibroblast-conditioned media rescued CRC from irinotecan, indicating that the rescue was due to a factor secreted by the fibroblasts. We determined whether fibroblast derived HGF increases irinotecan resistance through MET-dependent pathway. Fibroblast-derived conditioned media led to activation of MET receptors in CRC. The siHGF transfection abrogated such MET activation. To test whether HGF directly contributes to the effect on enhancing irinotecan resistance in CRC, anti-HGF antibodies were added to the CM to neutralize the HGF activity. We found that anti-HGF antibodies suppressed irinotecan resistance. Taken together, our findings suggest that the fibroblast derived HGF may play a general role in cancer cell survival and targeting HGF may represent a novel strategy for the treatment of CRC. To examine the possible induction of irinotecan resistance by fibroblast derived HGF and the efficacy of combined treatment with humanized anti-HGF antibody and irinotecan in vivo, we generated xenograft in NOD/SCID mice inoculating HCT-116 human colon cancer cells subcutaneously with or without fibroblast. We found that the combination of irinotecan and humanized anti-HGF antibody induced marked suppression of tumor development. These results suggest that HGF produced by fibroblast induces irinotecan resistance, and that humanized anti-HGF antibody abrogates such resistance in vivo. Conclusion: We identified HGF as an important determinant of resistance against irinotecan in CRC. Humanized anti-HGF antibody overcomes irinotecan resistance. These results demonstrate new options toward the early diagnosis of chemoresistance and suggest novel chemotherapy combining with anti-HGF antibody to prevent or significantly delay the onset of therapy resistance. These observations open new avenues toward the diagnosis of chemoresistance tumors and therapies targeting HGF over-expressing cancers. Citation Format: Jong Kyu Woo, Ju-Hee Kang, Keumju Shin, Seong-Won Song, Jung Ju Kim, Sang-Jin Lee, Seung Hyun Oh. Humanized anti-hepatocyte growth factor (HGF) antibody, suppresses innate irinotecan resistance induced by fibroblast-derived HGF in colon cancer cells. [abstract]. In: Proceedings of the AACR Special Conference: Tumor Immunology and Immunotherapy: A New Chapter; December 1-4, 2014; Orlando, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2015;3(10 Suppl):Abstract nr A15.

Abstract CT119: Early results from a phase II study of RRx-001, a novel, triple epigenetic inhibitor, showing resensitization to irinotecan in colorectal cancer

Abstract Background: Resistance acquisition to standard therapy in advanced colon cancer leads to poor patient survival. Epigenetic therapies can potentially reverse the chemoresistant phenotype. RRx-001, a novel ROS-mediated epigenetic modifier may resensitize to irinotecan-based therapies and increase overall survival compared to standard third-line regorafenib. Methods: The phase II ROCKET study evaluates a sequential rechallenge to irinotecan-based therapies after RRx-001 or regorafenib. Patients with an ECOG PS 0-1 with irinotecan-refractory metastatic colorectal cancer who progressed on oxaliplatin-, and irinotecan-based regimens with or without bevacizumab, cetuximab or panitumumab are randomized 2:1 to receive RRx-001 16.5 mg/m2 IV 1x/week or regorafenib 160 mg orally 21 of 28 days until progression or unacceptable toxicity followed by treatment with refractory irinotecan-based therapies. The primary end point is overall survival with secondary endpoints to investigate resensitization. The study is planned to accrue approx. 190 patients and recruitment is ongoing. Study Status and Results: To date, 23 patients have been randomized with 10 patients evaluable for resensitization. Post RRx-001 patients demonstrated marked decreases in CEA in all 6 patients as compared to 4 patients receiving regorafenib who were too systemically unwell to proceed to subsequent treatment. Conclusions: Early results in this study suggest that resensitization to irinotecan-based therapies mediated by RRx-001, a systemically non-toxic novel epigenetic inhibitor, may be a general effect. These early results are intriguing and may predict for increased overall survival, adding an additional regimen after disease progression. The trial is continuing. Citation Format: Tony Reid, George Fisher, Corey Carter, Cheryl Cho-Phan, Pamela Kunz, Bryan Oronsky, Gary R. Fanger, Scott Caroen, Christopher Parker, Jan Scicinski. Early results from a phase II study of RRx-001, a novel, triple epigenetic inhibitor, showing resensitization to irinotecan in colorectal cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr CT119. doi:10.1158/1538-7445.AM2015-CT119

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.

Oncolytic vaccinia virus synergizes with irinotecan in colorectal cancer

Metastatic colorectal cancer (CRC) is complex clinical challenge for which there are limited treatment options. Chemotherapy with or without surgery provides moderate improvements in overall survival and quality of life; nevertheless the 5-year survival remains below 30%. Oncolytic vaccinia virus (VV) shows strong anti-tumour activity in models of CRC, however transient delays in disease progression are insufficient to lead to long-term survival. Here we examined the efficacy of VV with oxaliplatin or SN-38 (active metabolite of irinotecan) in CRC cell lines in vitro and VV with irinotecan in an orthotopic model of metastatic CRC. Synergistic improvements in in vitro cell killing were observed in multiple cell lines. Combination therapy was well tolerated in tumour-bearing mice and the median survival was significantly increased relative to monotherapy despite a drug-dependent decrease in the mean tumour titer. Increased apoptosis following in vitro and in vivo combination therapy was observed. In vitro cell cycle analysis showed increases in S-phase cells following infection occurred in both infected and uninfected cell populations. This corresponded to a 4-fold greater increase in apoptosis in the uninfected compared to infected cells following combination therapy. Combination treatment strategies are among the best options for patients with advanced cancers. VV is currently under clinical investigation in patients with CRC and the data presented here suggest that its combination with irinotecan may provide benefit to a subset of CRC patients. Further, investigation of this combination is necessary to determine the tumour characteristics responsible for mediating synergy.

CCR 20th Anniversary commentary: in search of cetuximab's first indication-combination therapy with irinotecan in colorectal cancer.

The research article by Prewett and colleagues, published in the May 1, 2002, issue of Clinical Cancer Research, provided important translational data that extended earlier preclinical and clinical studies with the human-murine chimeric anti-EGFR monoclonal antibody C225. Subsequent clinical trials with C225 led to the demonstration of its efficacy in combination with irinotecan and regulatory approval for the treatment of metastatic colorectal cancer.

O3.8 - Early Results: “ROCKET” a phase II Study of RRx-001, a novel triple epigenetic inhibitor, Resensitization to Irinotecan in Colorectal Cancer

ABSTRACT Background: RRx-001 is a novel broad-spectrum anticancer agent that triply inhibits DNA methyltransferases (DNA MTases), Histone Deacetylases (HDAC), and Lysine Demethylases. In the first-in-human, Phase I trial, 5/5 patients who progressed on RRx-001 treatment were resensitized to previously refractory irinotecan therapy, hinting at a generalized resensitization effect. A randomized open-label multi-part, multi-center phase II trial of RRx-001 versus regorafenib (ROCKET) is underway to explore the resensitization and/or ‘episensitization’ potential in irinotecan refractory tumors and its impact on overall survival. Methods: Patients with irinotecan-refractory metastatic colorectal cancer with an ECOG PS 0–1 who progressed on oxaliplatin-, and irinotecan-based regimens with or without bevacizumab, cetuximab or panitumumab are randomized 2:1 to receive RRx-001 16.5 mg/m2 IV 1x/week or regorafenib 160 mg orally 21 of 28 days until progression or unacceptable toxicity followed by treatment with refractory irinotecan-based therapies. Results: To date, 23 patients have been randomized with 10 patients evaluable for resensitization. Post RRx-001 patients demonstrated marked decreases in CEA in all 6 patients as compared to 4 patients receiving regorafenib who were too systemically unwell to proceed to subsequent treatment. Progression free survival (ongoing) for RRx-001 + irinotecan is 5.9 months compared 0.92 months on Regorafenib + irinotecan. Combined Disease Control Rate (SD + PR) for the combination of RRx-001 and reintroduction of Irinotecan based therapy is currently 100%, whereas no patients to date randomized to the regorafenib arm have been able to start irinotecan based therapy secondary to decreasing performance status. Conclusions: Early results in the ROCKET study suggest that RRx-001-mediated resensitization to previously refractory therapies may have a generalized effect, independent of KRAS or p53 status. These early results are intriguing and may be a major advancement in epigenetic therapy. RRx-001 is a novel pan-epigenetic inhibitor that may potentially offer improved QOL and overall survival over currently approved therapy in the chemotherapy refractory colorectal cancer.

Time course of safety and efficacy of aflibercept in combination with FOLFIRI in patients with metastatic colorectal cancer who progressed on previous oxaliplatin-based therapy

BackgroundPatients with metastatic colorectal cancer (mCRC) previously-treated with oxaliplatin benefit significantly from the addition of aflibercept to FOLFIRI in relation to overall survival, progression-free survival and response rate. Patients and methodsThe results for efficacy and safety over the time course of the VEGF Trap (aflibercept) with irinotecan in colorectal cancer after failure of oxaliplatin regimen trial were analysed based on data from 1226 patients randomised to receive FOLFIRI plus either aflibercept (n=612) or placebo (n=614). Hazard ratios (HR) by 6-month time period were estimated using a piecewise Cox proportional hazard model. Severity of adverse events (AEs) was graded using National Cancer Institute Common Terminology Criteria, version 3.0. ResultsThe estimated probabilities of survival were 38.5% versus 30.9% at 18months, 28.0% versus 18.7% at 24months and 22.3% versus 12.0% at 30months, for the aflibercept- and placebo-treated arms, respectively. The proportional improvement in the HR over time was consistent with the survival probability results; survival at 24months was improved by 50% and almost doubled at 30months. The majority of worst-grade AEs occurred within the first four cycles of treatment and in a small percent of treatment cycles and were mostly reversible. Common chemotherapy- and anti-vascular epithelial growth factor (VEGF)-associated AEs occurred rarely and in a small proportion of cycles with the majority being of single occurrence. ConclusionsThe addition of aflibercept to FOLFIRI showed a continued and persistent improvement in overall survival over time in patients with mCRC. Although grade 3–4 AEs were more frequent in the aflibercept arm, they occurred in early treatment cycles and decreased sharply following initial presentation.

Abstract 1155: Promoter CpG island hypermethylation of Decoy Receptor 1 (DCR1) is associated with poor response to irinotecan in colorectal cancer.

Abstract Background Heterogeneity in the biology of colorectal cancer (CRC) is associated with variable responses to standard chemotherapy. We aimed to identify DNA hypermethylated genes as predictive biomarkers for irinotecan treatment of patients with metastatic CRC. Material and Methods The presence of DNA methylation for a selected panel of 22 genes was assessed by methylation specific PCR (MSP) on primary tumors of 185 patients with metastatic CRC treated with first-line capecitabine (CAP, n=90) or a combination of capecitabine and irinotecan (CAPIRI, n=95) in the phase III CAIRO trial. Methylation status of each gene was correlated to progression free survival (PFS) by treatment regimen. Genes for which methylation status associated with response to irinotecan, were validated in 166 patients treated with first-line CAP (n=78) or CAPIRI (n=88). Results Decoy Receptor 1 (DCR1) was identified as a novel hypermethylated gene in CRC. In CAPIRI treated patients, DCR1 methylation was correlated to a shorter PFS compared to patients with unmethylated DCR1 (hazard ratio [HR]=0.4 (95%CI =0.3-0.7), p = 0.0009). In patients with methylated DCR1 PFS did not improve with CAPIRI treatment, compared to treatment with CAP (discovery set: HR=0.8 (95%CI=0.5-1.3, p=0.4); validation set: HR=1.1 (95%CI 0.7-1.7, p=0.6)), in contrast to patients with unmethylated DCR1 (discovery set: HR=2.5 (95%CI 1.7-3.3, p=0.00004); validation set: HR=1.7 (95%CI 1.1-2.0, p=0.004)). Conclusion CRC patients with methylated DCR1 did not benefit from adding irinotecan to capecitabine therapy, indicating that DCR1 methylation status may guide selecting metastatic CRC patients for irinotecan-based therapy. Citation Format: Linda JW Bosch, Geert Trooskens, Petur Snaebjornsson, Josien C. Haan, Lorraine Pelosof, Miriam Koopman, Jolien Tol, Joost Louwagie, Luc Dehaspe, Bauke Ylstra, Henk Verheul, Manon van Engeland, Iris D. Nagtegaal, James G. Herman, Cornelis JA Punt, Wim van Criekinge, Beatriz Carvalho, Gerrit A. Meijer. Promoter CpG island hypermethylation of Decoy Receptor 1 (DCR1) is associated with poor response to irinotecan in colorectal cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1155. doi:10.1158/1538-7445.AM2013-1155

Utilization of Quantitative In Vivo Pharmacology Approaches to Assess Combination Effects of Everolimus and Irinotecan in Mouse Xenograft Models of Colorectal Cancer

PurposeThe PI3K/AKT/mTOR pathway is frequently dysregulated in cancers and inhibition of mTOR has demonstrated the ability to modulate pro-survival pathways. As such, we sought to determine the ability of the mTOR inhibitor everolimus to potentiate the antitumor effects of irinotecan in colorectal cancer (CRC).Experimental DesignThe combinatorial effects of everolimus and irinotecan were evaluated in vitro and in vivo in CRC cell lines harboring commonly found mutations in PIK3CA, KRAS and/or BRAF. Pharmacokinetically-directed dosing protocols of everolimus and irinotecan were established and used to assess the in vivo antitumor effects of the agents. At the end of treatment, 3–6 tumors per treatment arm were harvested for biomarker analysis by NMR metabolomics.ResultsEverolimus and irinotecan/SN38 demonstrated synergistic anti-proliferative effects in multiple CRC cell lines in vitro. Combination effects of everolimus and irinotecan were determined in CRC xenograft models using clinically-relevant dosing protocols. Everolimus demonstrated significant tumor growth inhibition alone and when combined with irinotecan in HT29 and HCT116 tumor xenografts. Metabolomic analysis showed that HT29 tumors were more metabolically responsive than HCT116 tumors. Everolimus caused a decrease in glycolysis in both tumor types whilst irinotecan treatment resulted in a profound accumulation of lipids in HT29 tumors indicating a cytotoxic effect.ConclusionsQuantitative analysis of tumor growth and metabolomic data showed that the combination of everolimus and irinotecan was more beneficial in the BRAF/PIK3CA mutant HT29 tumor xenografts, which had an additive effect, than the KRAS/PIK3CA mutant HCT116 tumor xenografts, which had a less than additive effect.

ALDH+ tumor-initiating cells exhibiting gain in NOTCH1 gene copy number have enhanced regrowth sensitivity to a γ-secretase inhibitor and irinotecan in colorectal cancer

The Notch signaling pathway has been shown to be upregulated in colorectal cancer (CRC) and important for the self-renewal of cancer stem cells. In this study, we evaluated the efficacy of PF-03084014, a γ-secretase inhibitor, in combination with irinotecan to identify the effects of treatment on tumor recurrence and the tumor-initiating population in our CRC preclinical explant model. The combination of PF-03084014 and irinotecan had the greatest effect at reducing tumor growth on four CRC tumors when compared with treatment with PF-03084014 or irinotecan alone. The combination significantly reduced tumor recurrence in two CRC explants (CRC001 and CRC036) after treatment was discontinued. Both of these tumors exhibited elevated baseline levels of Notch pathway activation as well as an increase in NOTCH1 gene copy number when compared with the two CRC explants (CRC026 and CRC027) where tumors reappeared quickly after termination of treatment. Isolation and injection of aldehyde dehydrogenase (ALDH+ and ALDH−) cells in an in vivo explant model demonstrated that the ALDH+ cell population were tumorigenic. Evaluation of the ALDH+ cells after 28 days of treatment showed that the combination reduced the ALDH+ population in the tumors that did not regrow. Furthermore, ALDH+ cells from CRC001 and CRC027 were injected in vivo and treated immediately for 28 days. Two months after treatment, tumors were evident in the combination treatment group for CRC027 but not for CRC036. These results indicate the combination of PF-03084014 and irinotecan may be effective in reducing tumor recurrence in CRC patients whose tumors exhibit elevated levels of the Notch pathway.