Topoisomerase I expression correlates to response to neoadjuvant irinotecan-based chemoradiation in rectal cancer

Topoisomerase I activity and sensitivity to camptothecin in breast cancer-derived cells: a comparative study

Background

Camptothecin (CPT) and its derivatives are currently used as second- or third-line treatment for patients with endocrine-resistant breast cancer (BC). These drugs convert nuclear enzyme DNA topoisomerase I (TOP1) to a cell poison with the potential to damage DNA by increasing the half-life of TOP1-DNA cleavage complexes (TOP1cc), ultimately resulting in cell death. In small and non-randomized trials for BC, researchers have observed extensive variation in CPT response rates, ranging from 14 to 64%. This variability may be due to the absence of reliable selective parameters for patient stratification. BC cell lines may serve as feasible models for generation of functional criteria that may be used to predict drug sensitivity for patient stratification and, thus, lead to more appropriate applications of CPT in clinical trials. However, no study published to date has included a comparison of multiple relevant parameters and CPT response across cell lines corresponding to specific BC subtypes.

Method

We evaluated the levels and possible associations of seven parameters including the status of the TOP1 gene (i.e. amplification), TOP1 protein expression level, TOP1 activity and CPT susceptibility, activity of the tyrosyl-DNA phosphodiesterase 1 (TDP1), the cellular CPT response and the cellular growth rate across a representative panel of BC cell lines, which exemplifies three major BC subtypes: Luminal, HER2 and TNBC.

Results

In all BC cell lines analyzed (without regard to subtype classification), we observed a significant overall correlation between growth rate and CPT response. In cell lines derived from Luminal and HER2 subtypes, we observed a correlation between TOP1 gene copy number, TOP1 activity, and CPT response, although the data were too limited for statistical analyses. In cell lines representing Luminal and TNBC subtypes, we observed a direct correlation between TOP1 protein abundancy and levels of enzymatic activity. In all three subtypes (Luminal, HER2, and TNBC), TOP1 exhibits approximately the same susceptibility to CPT. Of the three subtypes examined, the TNBC-like cell lines exhibited the highest CPT sensitivity and were characterized by the fastest growth rate. This indicates that breast tumors belonging to the TNBC subtype, may benefit from treatment with CPT derivatives.

Conclusion

TOP1 activity is not a marker for CPT sensitivity in breast cancer.

Topoisomerases and cancer chemotherapy: recent advances and unanswered questions

DNA topoisomerases are enzymes that catalyze changes in the torsional and flexural strain of DNA molecules. Earlier studies implicated these enzymes in a variety of processes in both prokaryotes and eukaryotes, including DNA replication, transcription, recombination, and chromosome segregation. Studies performed over the past 3 years have provided new insight into the roles of various topoisomerases in maintaining eukaryotic chromosome structure and facilitating the decatenation of daughter chromosomes at cell division. In addition, recent studies have demonstrated that the incorporation of ribonucleotides into DNA results in trapping of topoisomerase I (TOP1)–DNA covalent complexes during aborted ribonucleotide removal. Importantly, such trapped TOP1–DNA covalent complexes, formed either during ribonucleotide removal or as a consequence of drug action, activate several repair processes, including processes involving the recently described nuclear proteases SPARTAN and GCNA-1. A variety of new TOP1 inhibitors and formulations, including antibody–drug conjugates and PEGylated complexes, exert their anticancer effects by also trapping these TOP1–DNA covalent complexes. Here we review recent developments and identify further questions raised by these new findings.

Two open-label, single arm, non-randomized phase II studies of irinotecan for the treatment of metastatic breast cancer in patients with increased copy number of the topoisomerase I gene

Background

Treatment options in metastatic breast cancer are limited. New therapies preferable with predictive biomarkers are needed. The aim of these trials was to investigate if gene copy number of the topoisomerase 1 gene was predictive of response to the topoisomerase inhibitor irinotecan.

Methods

Two open-label, single-arm phase II studies including HER2 positive and negative patients were conducted. Patients were eligible for inclusion if the primary tumor or a metastatic lesion had increased expression of the topoisomerase 1 gene defined as a TOP1 gene copy number of ≥4 or a TOP1/CEN20 ratio of ≥2. Patients were treated with irinotecan +/− trastuzumab weekly for 4 weeks following 2 weeks break, until progression or unacceptable toxicities. Evaluation scans were performed every 6 weeks. Primary endpoint was clinical benefit rate defined as the fraction of patients with stable disease for ≥4 months.

Results

The pre-planned number of 18 patients in each trial was not reached, thus no formal statistical analysis could be performed. Nine patients with HER2 negative disease and three patients with HER2 positive disease were included. Three patients obtained a partial remission and two patients had SD.

Conclusions

The trials did not include the planned number of patients. No association between gene copy number of the topoisomerase 1 gene and response to irinotecan could be proved, however a clinical benefit was found in 5/12 patients and in 2/3 patients with HER2 positive disease. This could call for further investigation of the drug in the metastatic setting, especially in HER2 positive BC.

Trial registration

Eudract registration numbers 2012–002348-26 and 2012–002347-23. Registration date August 20th 2012.

Quantification and expert evaluation of evidence for chemopredictive biomarkers to personalize cancer treatment

Predictive biomarkers have the potential to facilitate cancer precision medicine by guiding the optimal choice of therapies for patients. However, clinicians are faced with an enormous volume of often-contradictory evidence regarding the therapeutic context of chemopredictive biomarkers.

We extensively surveyed public literature to systematically review the predictive effect of 7 biomarkers claimed to predict response to various chemotherapy drugs: ERCC1-platinums, RRM1-gemcitabine, TYMS-5-fluorouracil/Capecitabine, TUBB3-taxanes, MGMT-temozolomide, TOP1-irinotecan/topotecan, and TOP2A-anthracyclines. We focused on studies that investigated changes in gene or protein expression as predictors of drug sensitivity or resistance. We considered an evidence framework that ranked studies from high level I evidence for randomized controlled trials to low level IV evidence for pre-clinical studies and patient case studies.

We found that further in-depth analysis will be required to explore methodological issues, inconsistencies between studies, and tumor specific effects present even within high evidence level studies. Some of these nuances will lend themselves to automation, others will require manual curation. However, the comprehensive cataloging and analysis of dispersed public data utilizing an evidence framework provides a high level perspective on clinical actionability of these protein biomarkers. This framework and perspective will ultimately facilitate clinical trial design as well as therapeutic decision-making for individual patients.

Prospective randomized trial of neoadjuvant chemotherapy during the 'wait period' following preoperative chemoradiotherapy for rectal cancer: results of the WAIT trial

AIM

The aim was to determine whether the addition of additional cycles of chemotherapy during the 'wait period' following neoadjuvant chemoradiotherapy for rectal cancer improves the pathological complete response (pCR) rate.

METHOD

Rectal cancer patients were randomly allocated either to a standard 10 week wait period before surgery (standard chemoradiotherapy, SCRT) or to receive three cycles of fluorouracil based chemotherapy following chemoradiotherapy during a similar 10 week wait (extended chemoradiotherapy, XCRT). The primary end-point was pCR as determined by blinded pathological assessment.

RESULTS

Forty-nine patients were randomized (SCRTn = 24, XCRTn = 25). pCR occurred in 10 patients overall but there was no significant difference in pCR between the groups (SCRTn = 6, XCRTn = 4, P = 0.49).

CONCLUSION

The addition of three cycles of 5-fluorouracil/leucovorin in a 10 week wait period after conventional chemoradiotherapy seems to result in similar pCR rates in patients with locally advanced rectal cancer based on this small randomized trial.

Predictive value of vrk 1 and 2 for rectal adenocarcinoma response to neoadjuvant chemoradiation therapy: a retrospective observational cohort study

BACKGROUND

Neoadjuvant chemoradiotherapy (NACRT) followed by surgical resection is the standard therapy for locally advanced rectal cancer. However, tumor response following NACRT varies, ranging from pathologic complete response to disease progression. We evaluated the kinases VRK1 and VRK2, which are known to play multiple roles in cellular proliferation, cell cycle regulation, and carcinogenesis, and as such are potential predictors of tumor response and may aid in identifying patients who could benefit from NACRT.

METHODS

Sixty-seven pretreatment biopsies were examined for VRK1 and VRK2 expression using tissue microarrays. VRK1 and VRK2 Histoscores were combined by linear addition, resulting in a new variable designated as "composite score", and the statistical significance of this variable was assessed by univariate and multivariate logistic regression. The Hosmer-Lemeshow goodness-of-fit test and area under the ROC curve (AUC) analysis were carried out to evaluate calibration and discrimination, respectively. A nomogram was also developed.

RESULTS

Univariate logistic regression showed that tumor size as well as composite score were statistically significant. Both variables remained significant in the multivariate analysis, obtaining an OR for tumor size of 0.65 (95 % CI, 0.45-0.94; p = 0.021) and composite score of 1.24 (95 % CI, 1.07-1.48; p = 0.005). Hosmer-Lemeshow test showed an adequate model calibration (p = 0.630) and good discrimination was also achieved, AUC 0.79 (95 % CI, 0.68-0.90).

CONCLUSIONS

This study provides novel data on the role of VRK1 and VRK2 in predicting tumor response to NACRT, and we propose a model with high predictive ability which could have a substantial impact on clinical management of locally advanced rectal cancer.

Exceptional Response to Systemic Therapy in Advanced Metastatic Gastric Cancer: A Case Report

Gastroesophageal adenocarcinomas represent one of the top five most common types of cancer worldwide. Despite significant advancement, it is still not known which first-line chemotherapy option is best matched to an individual patient. The vast advances in molecular biology have led to the discovery of many potential predictive biomarkers, such as HER-2 neu, thymidylate synthase (TS), excision repair cross-complementation group 1 (ERCC1), and topoisomerase-1 (TOPO1). These markers could allow us to select treatment based on an individual’s tumor profile, resulting in an improvement of outcome. Our report highlights two patients with metastatic gastric cancer that achieved an exceptional response with traditional therapy and provides insights into the future perspectives of molecular profile-directed chemotherapy.

DNA Topoisomerase I Gene Copy Number and mRNA Expression Assessed as Predictive Biomarkers for Adjuvant Irinotecan in Stage II/III Colon Cancer

PURPOSE

Prospective-retrospective assessment of the TOP1 gene copy number and TOP1 mRNA expression as predictive biomarkers for adjuvant irinotecan in stage II/III colon cancer.

EXPERIMENTAL DESIGN

Formalin-fixed, paraffin-embedded tissue microarrays were obtained from an adjuvant colon cancer trial (PETACC3) where patients were randomized to 5-fluorouracil/folinic acid with or without additional irinotecan. TOP1 copy number status was analyzed by fluorescence in situ hybridization (FISH) using a TOP1/CEN20 dual-probe combination. TOP1 mRNA data were available from previous analyses.

RESULTS

TOP1 FISH and follow-up data were obtained from 534 patients. TOP1 gain was identified in 27% using a single-probe enumeration strategy (≥4 TOP1 signals per cell) and in 31% when defined by a TOP1/CEN20 ratio ≥ 1.5. The effect of additional irinotecan was not dependent on TOP1 FISH status.TOP1 mRNA data were available from 580 patients with stage III disease. Benefit of irinotecan was restricted to patients characterized by TOP1 mRNA expression ≥ third quartile (RFS: HRadjusted, 0.59;P= 0.09; OS: HRadjusted, 0.44;P= 0.03). The treatment by TOP1 mRNA interaction was not statistically significant, but in exploratory multivariable fractional polynomial interaction analysis, increasing TOP1 mRNA values appeared to be associated with increasing benefit of irinotecan.

CONCLUSIONS

In contrast to the TOP1 copy number, a trend was demonstrated for a predictive property of TOP1 mRNA expression. On the basis of TOP1 mRNA, it might be possible to identify a subgroup of patients where an irinotecan doublet is a clinically relevant option in the adjuvant setting of colon cancer.

Topoisomerase-1 gene copy aberrations are frequent in patients with breast cancer

Topoisomerase-1 (Top1) targeting drugs have shown promising efficacy in patients with metastatic breast cancer (BC). However, these drugs are rather toxic calling for development and validation of predictive biomarkers to increase the therapeutic index. As these drugs are targeting the Top1 protein and since no validated anti-Top1 antibodies for immunohistochemistry have been reported, we raised the hypothesis that TOP1 gene amplifications may serve as a proxy for the Top1 protein and thereby a biomarker of response to treatment with Top1 inhibitors in BC. The aim was to determine the prevalence of TOP1 gene copy gain in BC. The prevalence of TOP1 gene copy gain was investigated by fluorescence in situ hybridization with a TOP1/CEN-20 probemix in normal breast tissue (N = 100) and in tissue from patients with metastatic BC in a discovery (N = 100) and a validation cohort (N = 205). As amplification of 20q including CEN-20 is common in BC a TOP1/CEN-2 probemix was applied to the validation cohort. More than 30% of the patients had gene copy numbers of ≥ 4 and ∼20% of the patients had TOP1/CEN-20 ratios ≥ 1.5. The CEN-2 probe did not add any information. Gain of the TOP1 gene appears to be common in BC making the gene a potential biomarker for response to treatment with Top1 inhibitors. As 20q amplification is a common finding in BC and as no other suitable reference gene has yet been identified, TOP1 copy number may be a more valid method of detecting gain than using a gene/centromere ratio.

A phase II study of weekly irinotecan in patients with locally advanced or metastatic HER2- negative breast cancer and increased copy numbers of the topoisomerase 1 (TOP1) gene: a study protocol

Background

About 20% of patients with primary breast cancer develop metastatic disease during the course of the disease. At this point the disease is considered incurable and thus treatment is aimed at palliation and life prolongation. As many patients will have received both an anthracycline and a taxane in the adjuvant setting, treatment options for metastatic breast cancer are limited. Furthermore response rates for the most commonly used drugs range from around 30% to 12% . Thus new treatment options are needed and preferably coupled to biomarkers predictive of response. Irinotecan is a topoisomerase 1 inhibitor used for decades for the treatment of colorectal cancer. Four studies have investigated the efficacy of irinotecan monotherapy in breast cancer and all have included non-biomarker selected patients. In these studies response rates for irinotecan ranged from 5%-23% and are thus comparable to response rates obtained with drugs commonly used in the metastatic setting. If a predictive biomarker could be identified for irinotecan, response rates might be even higher.

Methods/Design

This multi-centre phase II single arm trial was designed to investigate if patients with metastatic breast cancer and increased expression of the topoisomerase 1 gene have a high likelihood of obtaining a clinical benefit from treatment with irinotecan. Trial recruitment is two-staged as 19 patients are planned to participate in the first part. If less than 7 patients have clinical benefit the trial stops, if more than 7 patients have clinical benefit a total of 40 patients will be included.

Discussion

This ongoing trial is the first to prospectively test copy number of the topoisomerase I gene as a predictive biomarker of response to irinotecan.

Trial registration

EudraCT number 2012-002348-26.

Clinical and cellular roles for TDP1 and TOP1 in modulating colorectal cancer response to irinotecan

Colorectal cancer is the third most common cancer in the world. Despite surgery, up to 50% of patients relapse with incurable disease. First-line chemotherapy uses the topoisomerase 1 (TOP1) poison irinotecan, which triggers cell death by trapping TOP1 on DNA. The removal of TOP1 peptide from TOP1-DNA breaks is conducted by tyrosyl-DNA phosphodiesterase 1 (TDP1). Despite putative roles for TDP1 and TOP1 in colorectal cancer, their role in cellular and clinical responses to TOP1-targeting therapies remains unclear. Here, we show varying expression levels of TOP1 and TDP1 polypeptides in multiple colorectal cancer cell lines and in clinical colorectal cancer samples. TDP1 overexpression or TOP1 depletion is protective. Conversely, TDP1 depletion increases DNA-strand breakage and hypersensitivity to irinotecan in a TOP1-dependent manner, presenting a potential therapeutic opportunity in colorectal cancer. TDP1 protein levels correlate well with mRNA and with TDP1 catalytic activity. However, no correlation is observed between inherent TDP1 or TOP1 levels alone and irinotecan sensitivity, pointing at their limited utility as predictive biomarkers in colorectal cancer. These findings establish TDP1 as a potential therapeutic target for the treatment of colorectal cancer and question the validity of TOP1 or TDP1 on their own as predictive biomarkers for irinotecan response.

The impact of pathologic nodal status on survival following neoadjuvant chemoradiation for locally advanced rectal cancer

PURPOSE

For patients with locally advanced rectal cancer, the accuracy rates of preneoadjuvant therapy nodal staging and potential nodal downstaging make the prognostic significance of nodal status unclear. We therefore sought to review our experience in order to better understand the impact of clinical and pathologic nodal status upon patient outcomes.

METHODS

174 patients were identified as having undergone neoadjuvant chemoradiation and resection for rectal cancer. For analytic purposes, patients were grouped into four nodal categories (uN( 0)· pN( 0), uN( 0)· pN( +), uN (+) · pN( 0), and uN (+) · pN( +)). Univariate and multivariate analyses were performed.

RESULTS

104 men and 70 women of median age 60 years (29-85 years) were followed for a median of 31 months (1-121 months). Nodal staging was available for 129 patients, with a median of 8 lymph nodes (range 0-39) evaluated. Disease recurred in 3 of 41 (7%) uN   (0) ·pN (  0), 10 of 52 (20%) uN (   +)·pN (  0), 7 of 18 (41%) uN (  0)·pN (   +), and 6 of 17 (35%) uN (  +)·pN (  +) patients. Those patients having nodal downstaging (uN (  +)·pN (  0)) experienced superior overall survival (p = 0.03). Only pathologic nodal status was a significant predictor of both disease-free and overall survival in multivariate modeling. Adjuvant chemotherapy did not impact disease-free or overall survival for patients with pN0.

CONCLUSIONS

Pathologic nodal status may represent a superior predictor of survival for patients with local advanced rectal cancers. Our findings may have potential implications for the application of adjuvant therapy.

Molecular profiling in gastric cancer: examining potential targets for chemotherapy

BACKGROUND AND OBJECTIVES

Current NCCN guidelines recommend epirubicin (E), cisplatin (C), and 5-fluorouracil (F) as a first-line therapeutic approach for operable gastric adenocarcinoma (GC). Molecular profiling (MP) was used to evaluate the expression of chemotherapy targeted biomarkers associated with ECF therapy and other first-line cytotoxic regimens for GC.

METHODS

GC specimens were analyzed by immunohistochemistry (IHC) for TOP2A, TS, ERCC1, PGP, and TOPO1 expression (Caris Life Sciences, Phoenix, AZ) from 2009 to 2012.

RESULTS

A total of 230 GC specimens were analyzed. The median age of patients was 61 (IQR: 50-72) years with the majority being male (n = 139, 60%). IHC actionable targets included: 60% (n = 138) high TOP2A, 55% (n = 127) negative ERCC1, and 63% (n = 145) negative TS, indicating potential benefit from E, C, and F, respectively. Simultaneous expression analysis demonstrated only 24% (n = 55) of patients had gene expression levels that suggested uniform sensitivity to ECF. Biomarker results of 6.5% (n = 15) of patients revealed a potential complete lack of sensitivity to first-line ECF.

CONCLUSIONS

MP of GC has the potential to define patients who would derive the greatest benefit from current therapies. Prospective controlled studies are required to validate the role of biomarkers in the management of GC patients.

Pharmacodynamic and pharmacogenomic study of the nanoparticle conjugate of camptothecin CRLX101 for the treatment of cancer

CRLX101 is a nanopharmaceutical consisting of cyclodextrin-based polymer molecule and camptothecin. The CRLX101 nanoparticle is designed to concentrate and slowly release camptothecin in tumors over an extended period of time. Tumor biopsy and blood samples collected from patients with advanced solid malignancies before and after CRLX101 treatment are subjected to immunohistochemistry and pharmacogenomics. The expression of Topoisomerase-1, Ki-67, CaIX, CD31 and VEGF decreased after CRLX101 treatment. The expressions of these proteins are inversely proportional with survival duration of the patients. The Drug Metabolism Enzymes and Transporters (DMET) array shows an allele frequency in patients similar to global populations with none of the SNPs associated with toxicity. The results suggest that the observed lower toxicity is not likely to be due to different genotypes in SNPs. CRLX101 demonstrates a promising anti-tumor activity in heavily pre-treated or treatment-refractory solid tumor malignancies presumably by inhibition of proliferation and angiogenesis correlating with tumor growth inhibition. From the clinical editor: In this cancer treatment study clinical samples collected from patients were subjected to immunohistochemistry and pharmacogenomics. The expressions of key proteins that are inversely proportional with survival duration of the patients decreased after treatment with CRLX101, a camptothecin slow-release nanoparticle conjugate. This anti-tumor activity in heavily pre-treated and treatment resistant solid tumors, promises a novel therapeutic approach.

Antitumor activity of FL118, a survivin, Mcl-1, XIAP, and cIAP2 selective inhibitor, is highly dependent on its primary structure and steric configuration

We recently reported the identification and characterization of a novel small chemical molecule designated FL118. FL118 selectively inhibits multiple cancer survival and proliferation-associated antiapoptotic proteins (survivin, Mcl-1, XIAP, cIAP2) and eliminates small and large human tumor xenografts in animal models (Ling et al., PLoS One 2012, 7, e45571). Here, we report a follow-up study on the structure-activity relationship (SAR) of the hydroxyl group in the lactone ring of FL118. We found that the superior antitumor efficacy of FL118 heavily depends on its steric configuration through comparing the antitumor activity of FL118 with FL113 (the racemic mixture of FL118). Consistently, FL118 proved much more effective in inhibiting the expression of survivin, Mcl-1, and cIAP2, both in vitro and in vivo, compared to FL113. Additionally, Tet-on controlled induction of survivin or forced expression of Mcl-1 protects cancer cells from FL118-mediated growth inhibition and cell death. To further explore the SAR, we synthesized seven position 20-esterifiable FL118 and FL113 derivatives. Studies on these seven new compounds revealed that keeping a free hydroxyl group of FL118 is also important for high antitumor efficacy. Together, these studies confirm the superior anticancer activity of FL118 and narrow the window for further SAR studies to generate novel analogues based on FL118 core structure on its other potential chemical positions.

Assessment of the topoisomerase I gene copy number as a predictive biomarker of objective response to irinotecan in metastatic colorectal cancer

OBJECTIVE

DNA topoisomerase I is a putative biomarker of irinotecan efficacy with clinical associations previously demonstrated at the protein level. The purpose of the present study was to perform the first clinical investigation of the association between the DNA topoisomerase I gene (TOP1) copy number and objective response following irinotecan treatment in patients with metastatic colorectal cancer.

MATERIALS AND METHODS

Formalin-fixed, paraffin-embedded tumor samples from 78 patients, who received irinotecan monotherapy in second line, were included. TOP1 was assessed by fluorescence in situ hybridization using a technically validated dual-probe combination that hybridizes to TOP1, located at 20q12-q13.1, and to the centromere region of chromosome 20 (CEN-20). In univariate logistic regression models, the TOP1 signal count per cell and the TOP1/CEN-20 ratio were associated with objective response, which was evaluated according to RECIST v.1.1.

RESULTS

Gain of TOP1 was identified in 52.6% and 37.2% using the following cutoff values: TOP1 signal count per cell ≥3.6 and TOP1/CEN-20 ≥1.5, respectively. A borderline significant association (Odds ratio (OR): 1.62; p = 0.07) between a stepwise increase in the TOP1 signal count and objective response was demonstrated. In relation to the applied cutoff values, nonsignificant associations with objective response were identified for the TOP1 signal count (OR: 2.41; p = 0.23) and for the TOP1/CEN-20 ratio (OR: 2.05; p = 0.30).

CONCLUSIONS

Despite limitations of the study the positive associations between TOP1 and objective response suggest that further analysis in larger tumor material, preferably in a randomized setting, is highly warranted.

Biomarker-guided repurposing of chemotherapeutic drugs for cancer therapy: a novel strategy in drug development

Cancer is a leading cause of mortality worldwide and matters are only set to worsen as its incidence continues to rise. Traditional approaches to combat cancer include improved prevention, early diagnosis, optimized surgery, development of novel drugs, and honing regimens of existing anti-cancer drugs. Although discovery and development of novel and effective anti-cancer drugs is a major research area, it is well known that oncology drug development is a lengthy process, extremely costly and with high attrition rates. Furthermore, those drugs that do make it through the drug development mill are often quite expensive, laden with severe side-effects and unfortunately, to date, have only demonstrated minimal increases in overall survival. Therefore, a strong interest has emerged to identify approved non-cancer drugs that possess anti-cancer activity, thus shortcutting the development process. This research strategy is commonly known as drug repurposing or drug repositioning and provides a faster path to the clinics. We have developed and implemented a modification of the standard drug repurposing strategy that we review here; rather than investigating target-promiscuous non-cancer drugs for possible anti-cancer activity, we focus on the discovery of novel cancer indications for already approved chemotherapeutic anti-cancer drugs. Clinical implementation of this strategy is normally commenced at clinical phase II trials and includes pre-treated patients. As the response rates to any non-standard chemotherapeutic drug will be relatively low in such a patient cohort it is a pre-requisite that such testing is based on predictive biomarkers. This review describes our strategy of biomarker-guided repurposing of chemotherapeutic drugs for cancer therapy, taking the repurposing of topoisomerase I (Top1) inhibitors and Top1 as a potential predictive biomarker as case in point.

Role of topoisomerase I and thymidylate synthase expression in sporadic colorectal cancer: associations with clinicopathological and molecular features

Topoisomerase I (Topo I) and thymidylate synthase (TS) are essential enzymes for the replication, transcription and repair of DNA, and are potential biomarkers in colorectal cancer (CRC). The aim of the study was to correlate the tissue expression of Topo I and TS in sporadic CRCs with relevant pathological and molecular features and patients' outcome. Topo I and TS expression was assessed by immunostaining in 112 consecutive primary CRCs. Increased expression of Topo I was found in 36% of tumors, preferentially rectal (50%) and with not otherwise specified (NOS) histology (44%). Topo I expression was associated with 18q allelic loss (LOH), (p=0.013), microsatellite stable phenotype (p=0.002) and normal expression of mismatch proteins hMLH1 and hMSH2 (p=0.0012 and p=0.02, respectively). High TS expression was found in 60% of tumors, more frequently in distal sites (62%) and with NOS histology (66%); no association with microsatellite instability was observed. Topo I seems to be involved in the chromosomal instability pathway of sporadic CRCs. Conversely, high TS expression is unlikely to affect the clinical behavior of microsatellite unstable CRCs.

A novel small molecule FL118 that selectively inhibits survivin, Mcl-1, XIAP and cIAP2 in a p53-independent manner, shows superior antitumor activity

Drug/radiation resistance to treatment and tumor relapse are major obstacles in identifying a cure for cancer. Development of novel agents that address these challenges would therefore be of the upmost importance in the fight against cancer. In this regard, studies show that the antiapoptotic protein survivin is a central molecule involved in both hurdles. Using cancer cell-based survivin-reporter systems (US 7,569,221 B2) via high throughput screening (HTS) of compound libraries, followed by in vitro and in vivo analyses of HTS-derived hit-lead compounds, we identified a novel anticancer compound (designated FL118). FL118 shows structural similarity to irinotecan. However, while the inhibition of DNA topoisomerase 1 activity by FL118 was no better than the active form of irinotecan, SN-38 at 1 µM, FL118 effectively inhibited cancer cell growth at less than nM levels in a p53 status-independent manner. Moreover, FL118 selectively inhibited survivin promoter activity and gene expression also in a p53 status-independent manner. Although the survivin promoter-reporter system was used for the identification of FL118, our studies revealed that FL118 not only inhibits survivin expression but also selectively and independently inhibits three additional cancer-associated survival genes (Mcl-1, XIAP and cIAP2) in a p53 status-independent manner, while showing no inhibitory effects on control genes. Genetic silencing or overexpression of FL118 targets demonstrated a role for these targets in FL118's effects. Follow-up in vivo studies revealed that FL118 exhibits superior antitumor efficacy in human tumor xenograft models in comparison with irinotecan, topotecan, doxorubicin, 5-FU, gemcitabine, docetaxel, oxaliplatin, cytoxan and cisplatin, and a majority of mice treated with FL118 showed tumor regression with a weekly × 4 schedule. FL118 induced favorable body-weight-loss profiles (temporary and reversible) and was able to eliminate large tumors. Together, the molecular targeting features of FL118 plus its superior antitumor activity warrant its further development toward clinical trials.

Phase II and gene expression analysis trial of neoadjuvant capecitabine plus irinotecan followed by capecitabine-based chemoradiotherapy for locally advanced rectal cancer: Hoosier Oncology Group GI03-53

PURPOSE

We designed this study in locally advanced rectal cancer to determine the pathological response, toxicity, and disease-free survival (DFS) with induction capecitabine plus irinotecan followed by capecitabine-based chemoradiotherapy (CRT) and analyze the gene expression of enzymes involved in the metabolism of capecitabine and irinotecan for associations with response and toxicity.

METHODS

Patients with T3/T4 or node positive rectal cancer were treated with capecitabine 1,000 mg/m(2) twice daily (BID) days 1-14, and irinotecan 200 mg/m(2) on day 1 every 21 days for 2 cycles, followed by capecitabine 825 mg/m(2) BID days 1-5 per week with concurrent radiotherapy 50.4 Gy in 28 fractions. Surgical resection occurred a median of 7.4 weeks after CRT. Gene expression levels or sequencing were used to analyze carboxylesterase-converting enzymes (CES1, CES2), thymidylate synthase (TS), thymidine phosphorylase (TP), dehydropyrimidine dehydrogenase (DPD), topoisomerase I (TOPO I), and uridine-diphosphate (UDP) glucuronosyl transferase 1A1 in pre- and post-treatment tumor and normal tissue samples.

RESULTS

Twenty-two patients were enrolled, and 18 completed neoadjuvant therapy and underwent R0 resection. Two patients with UGT1A1 7/7 had grade 3 and 4 neutropenic fever and sepsis. Pathological complete response (pCR) occurred in 6 of 18 patients (33 %) and 10 (56 %) had tumor and/or nodal downstaging. The 3-year DFS was 75.5 % (95 % CI, 39.7-91.8 %). Locoregional control rate was 100 %. We observed higher TP gene expression in pCR patients, but no correlations with toxicity.

CONCLUSIONS

This neoadjuvant regimen was safe and demonstrated significant antitumor activity. High TP tumor gene expression was associated with obtaining pCR.

Topoisomerase I inhibition in colorectal cancer: biomarkers and therapeutic targets

The topoisomerase I (Top 1) poison irinotecan is an important component of the modern treatment of colorectal cancer. By stabilising Top 1-DNA complexes, irinotecan generates Top 1-linked DNA single-strand breaks that can evolve into double-strand breaks and ultimately cause cell death. However, cancer cells may overcome cell killing by releasing the stalled topoisomerase from DNA termini, thereby reducing the efficacy of Top 1 poisons in clinics. Thus, understanding the DNA repair mechanisms involved in the repair of Top 1-mediated DNA damage provides a useful tool to identify potential biomarkers that predict response to this class of chemotherapy. Furthermore, targeting these pathways could enhance the therapeutic benefits of Top 1 poisons. In this review, we describe the cellular mechanisms and consequences of targeting Top 1 activity in cells. We summarise preclinical data and discuss the potential clinical utility of small-molecule inhibitors of the key proteins.

Sex and dosing-time dependencies in irinotecan-induced circadian disruption

Circadian disruption accelerates malignant growth; thus, it should be avoided in anticancer therapy. The circadian disruptive effects of irinotecan, a topoisomerase I inhibitor, was investigated according to dosing time and sex. In previous work, irinotecan achieved best tolerability following dosing at zeitgeber time (ZT) 11 in male and ZT15 in female mice, whereas worst toxicity corresponded to treatment at ZT23 and ZT3 in male and female mice, respectively. Here, irinotecan (50 mg/kg intravenous [i.v.]) was delivered at the sex-specific optimal or worst circadian timing in male and female B6D2F1 mice. Circadian disruption was assessed with rest-activity, body temperature, plasma corticosterone, and liver mRNA expressions of clock genes Rev-erbα, Per2, and Bmal1. Baseline circadian rhythms in rest-activity, body temperature, and plasma corticosterone were more prominent in females as compared to males. Severe circadian disruption was documented for all physiology and molecular clock endpoints in female mice treated at the ZT of worst tolerability. Conversely, irinotecan administration at the ZT of best tolerability induced slight alteration of circadian physiology and clock-gene expression patterns in female mice. In male mice, irinotecan produced moderate alterations of circadian physiology and clock-gene expression patterns, irrespective of treatment ZT. However, the average expression of Rev-erbα, Per2, and Bmal1 were down-regulated 2- to 10-fold with irinotecan at the worst ZT, while being minimally or unaffected at the best ZT, irrespective of sex. Corticosterone secretion increased acutely within 2 h with a sex-specific response pattern, resulting in a ZT-dependent phase-advance or -delay in both sex. The mRNA expressions of irinotecan clock-controlled metabolism genes Ce2, Ugt1a1, and Top1 were unchanged or down-regulated according to irinotecan timing and sex. This study shows that the circadian timing system represents an important toxicity target of irinotecan in female mice, where circadian disruption persists after wrongly timed treatment. As a result, the mechanisms underling cancer chronotherapeutics are expectedly more susceptible to disruption in females as compared to males. Thus, the optimal circadian timing of chemotherapy requires precise determination according to sex, and should involve the noninvasive monitoring of circadian biomarkers.

Expression of Transketolase like gene 1 (TKTL1) predicts disease-free survival in patients with locally advanced rectal cancer receiving neoadjuvant chemoradiotherapy

Background

For patients with locally advanced rectal cancer (LARC) neoadjuvant chemoradiotherapy is recommended as standard therapy. So far, no predictive or prognostic molecular factors for patients undergoing multimodal treatment are established. Increased angiogenesis and altered tumour metabolism as adaption to hypoxic conditions in cancers play an important role in tumour progression and metastasis. Enhanced expression of Vascular-endothelial-growth-factor-receptor (VEGF-R) and Transketolase-like-1 (TKTL1) are related to hypoxic conditions in tumours. In search for potential prognostic molecular markers we investigated the expression of VEGFR-1, VEGFR-2 and TKTL1 in patients with LARC treated with neoadjuvant chemoradiotherapy and cetuximab.

Methods

Tumour and corresponding normal tissue from pre-therapeutic biopsies of 33 patients (m: 23, f: 10; median age: 61 years) with LARC treated in phase-I and II trials with neoadjuvant chemoradiotherapy (cetuximab, irinotecan, capecitabine in combination with radiotherapy) were analysed by quantitative PCR.

Results

Significantly higher expression of VEGFR-1/2 was found in tumour tissue in pre-treatment biopsies as well as in resected specimen after neoadjuvant chemoradiotherapy compared to corresponding normal tissue. High TKTL1 expression significantly correlated with disease free survival. None of the markers had influence on early response parameters such as tumour regression grading. There was no correlation of gene expression between the investigated markers.

Conclusion

High TKTL-1 expression correlates with poor prognosis in terms of 3 year disease-free survival in patients with LARC treated with intensified neoadjuvant chemoradiotherapy and may therefore serve as a molecular prognostic marker which should be further evaluated in randomised clinical trials.