Predictive and prognostic markers in the treatment of metastatic colorectal cancer (mCRC): personalized medicine at work

Personalized reference intervals: from theory to practice

Using laboratory test results for diagnosis and monitoring requires a reliable reference to which the results can be compared. Currently, most reference data is derived from the population, and patients in this context are considered members of a population group rather than individuals. However, such reference data has limitations when used as the reference for an individual. A patient's test results preferably should be compared with their own, individualized reference intervals (RI), i.e. a personalized RI (prRI).The prRI is based on the homeostatic model and can be calculated using an individual's previous test results obtained in a steady-state situation and estimates of analytical (CV_A) and biological variation (BV). BV used to calculate the prRI can be obtained from the population (within-subject biological variation, CV_I) or an individual's own data (within-person biological variation, CV_P). Statistically, the prediction interval provides a useful tool to calculate the interval (i.e. prRI) for future observation based on previous measurements. With the development of information technology, the data of millions of patients is stored and processed in medical laboratories, allowing the implementation of personalized laboratory medicine. PrRI for each individual should be made available as part of the laboratory information system and should be continually updated as new test results become available.In this review, we summarize the limitations of population-based RI for the diagnosis and monitoring of disease, provide an outline of the prRI concept and different approaches to its determination, including statistical considerations for deriving prRI, and discuss aspects which must be further investigated prior to implementation of prRI in clinical practice.

Towards Circulating-Tumor DNA-Based Precision Medicine

In the era of precision medicine, targeted therapies have been implemented for various diseases. Genomic information guides decision-making in cancer treatment. The improvements in next-generation sequencing and polymerase chain reaction have made it possible to access the genetic information using circulating-tumor DNAs (ctDNAs). Molecular characteristics of individual tumors can be obtained by analysis of ctDNAs, thus making them excellent tools to guide decision-making during treatment. In oncology, the use of ctDNAs in clinical practice is now gaining importance. Molecular analysis of ctDNAs has potential for multiple clinical applications, including early diagnosis, prognosis of disease, prognostic and/or predictive biomarkers, and monitoring response to therapy and clonal evolution. In this paper, we highlight the applications of ctDNAs in cancer management, especially in metastatic setting, and summarize recent studies about the use of ctDNAs as predictive biomarkers for the therapeutic adaptation/response in lung cancer, breast cancer, and colorectal cancer. These studies offer the evidence to use ctDNAs as a promising approach to solve unmet clinical needs.

Predictive Values of Postoperative and Dynamic Changes of Inflammation Indexes in Survival of Patients with Resected Colorectal Cancer

The aim of the present study was to evaluate the prognostic potential of postoperative scores of inflammation indexes and the dynamic changes of scores before and after tumor resection in colorectal cancer patients. The study included 516 colorectal cancer patients with primary colorectal tumor resection. Cox regression was applied to estimate the associations of postoperative and dynamic changes of inflammation indexes with progression-free survival and overall survival. As results, we found that higher postoperative neutrophil to lymphocyte ratio (NLR), neutrophil and monocyte to lymphocyte ratio (NMLR), platelet to lymphocyte ratio (PLR) and systemic immune inflammation index (SII) were associated with shorter progression-free survival. The increased NLR, NMLR, PLR, SII and C-reaction protein (CRP) to albumin (ALB) ratio (CAR) were associated with poor progression-free survival, with HRs (95% CIs) of 1.92 (1.27-2.90), 1.46 (1.11-2.09), 2.10 (1.34-3.30), 1.81 (1.22-2.70) and 1.65 (1.03-2.67), respectively. Postoperative NMLR, SII, CAR, and their dynamic changes were also significantly correlated with overall survival, with the HRs (95% CIs) of 2.63 (1.30-3.97), 2.44 (1.43-4.17), 2.74 (1.31-5.74), 2.08 (1.21-3.60), 1.97 (1.12-3.45) and 2.55 (1.21-5.38) respectively. In conclusion, postoperative inflammation indexes and their dynamic changes, particularly for NMLR, SII and CAR are promising prognostic predictors of CRC patients.

Dysregulation of miR-126/Crk protein axis predicts poor prognosis in gastric cancer patients

BACKGROUND

miR-126 functions as a tumor suppressor in gastric cancer (GC) by negatively regulating Crk protein expression post-transcriptionally.

OBJECTIVE

The aim of this study was to investigate the associations of miR-126 and Crk protein expression levels, alone or in combination, with the clinicopathological characteristics and prognosis of GC patients.

METHODS

The expression levels of miR-126 and Crk protein in 338 GC patients were analyzed by quantitative real-time polymerase chain reaction and immunohistochemistry, respectively. The relationship of miR-126 and Crk protein expression with clinicopathologic characteristics and clinical outcome was evaluated.

RESULTS

Compared with matched adjacent non-tumor tissues, miR-126 was significantly down-regulated while Crk protein was significantly up-regulated in tumor tissues. A reduced miR-126 expression and an elevated Crk protein expression, alone or in combination, statistically correlated with aggressive clinicopathological characteristics, such as larger tumor size, deeper local invasion, more lymph node metastasis, advanced TNM stage, and poorer prognosis. Multivariate analysis showed that combined miR-126-low/Crk protein-high expression was an independent unfavorable prognostic factor of GC.

CONCLUSIONS

These results indicate for the first time that miR-126 down-regulation and Crk protein up-regulation may be synergistically associated with tumor progression in GC and may predict unfavorable prognosis of GC.

Nomogram Integrating Genomics with Clinicopathologic Features Improves Prognosis Prediction for Colorectal Cancer

The current tumor staging system is insufficient for predicting the outcomes for patients with colorectal cancer because of its phenotypic and genomic heterogeneity. Integrating gene expression signatures with clinicopathologic factors may yield a predictive accuracy exceeding that of the currently available system. Twenty-seven signatures that used gene expression data to predict colorectal cancer prognosis were identified and re-analyzed using bioinformatic methods. Next, clinically annotated colorectal cancer samples (n = 1710) with the corresponding expression profiles, that predicted a patient's probability of cancer recurrence, were pooled to evaluate their prognostic values and establish a clinicopathologic-genomic nomogram. Only 2 of the 27 signatures evaluated showed a significant association with prognosis and provided a reasonable prediction accuracy in the pooled cohort (HR, 2.46; 95% CI, 1.183-5.132, P < 0.001; AUC, 60.83; HR, 2.33; 95% CI, 1.218-4.453, P < 0.001; AUC, 71.34). By integrating the above signatures with prognostic clinicopathologic features, a clinicopathologic-genomic nomogram was cautiously constructed. The nomogram successfully stratified colorectal cancer patients into three risk groups with remarkably different DFS rates and further stratified stage II and III patients into distinct risk subgroups. Importantly, among patients receiving chemotherapy, the nomogram determined that those in the intermediate- (HR, 0.98; 95% CI, 0.255-0.679, P < 0.001) and high-risk (HR, 0.67; 95% CI, 0.469-0.957, P = 0.028) groups had favorable responses.Implications: These findings offer evidence that genomic data provide independent and complementary prognostic information, and incorporation of this information refines the prognosis of colorectal cancer. Mol Cancer Res; 16(9); 1373-84. ©2018 AACR.

Association of baseline absolute neutrophil counts and survival in patients with metastatic colorectal cancer treated with second-line antiangiogenic therapies: exploratory analyses of the RAISE trial and validation in an electronic medical record data set

BACKGROUND

In the RAISE trial, ramucirumab+leucovorin/fluorouracil/irinotecan (FOLFIRI) improved the median overall survival (mOS) of patients with previously treated metastatic colorectal cancer versus patients treated with placebo+FOLFIRI but had a higher incidence of neutropaenia, leading to more chemotherapy dose modifications and discontinuations. Thus, we conducted an exploratory post-hoc analysis of RAISE and a retrospective, observational analysis of electronic medical record (EMR) data to determine and verify the association of neutropaenia, baseline absolute neutrophil count (ANC) and survival.

METHODS

The RAISE analysis used the study safety population (n=1057). IMS Health Oncology Database (IMS EMR) was the source for the real-world data set (n=617).

RESULTS

RAISE patients with treatment-emergent neutropaenia had improved mOS compared with those without (ramucirumab arm: 16.1 vs 10.7 months, HR=0.57, p<0.0001; placebo arm: 12.7 vs 10.7 months, HR=0.76, p=0.0065). RAISE patients with low ANC versus high baseline ANC also had longer mOS (ramucirumab arm: 15.2 vs 8.9 months, HR=0.49, p<0.0001; placebo arm: 13.2 vs 7.3 months, HR=0.50, p<0.0001). The results were similar for IMS EMR low versus high baseline ANC (bevacizumab+FOLFIRI patients: 14.9 vs 7.7 months, HR=0.59, p<0.0001; FOLFIRI alone: 14.6 vs 5.4 months, HR=0.37, p<0.0001). Patients in the RAISE trial with low baseline ANC were more likely to develop neutropaenia (OR: ramucirumab arm=2.62, p<0.0001; placebo arm=2.16, p=0.0003).

CONCLUSION

Neutropaenia during treatment, and subsequent dose modifications or discontinuations, do not compromise treatment efficacy. Baseline ANC is a strong prognostic factor for survival and is associated with treatment-emergent neutropaenia in the analysed population.

TRIAL REGISTRATION NUMBER

NCT01183780, Results.

LRP1 expression in colon cancer predicts clinical outcome

LRP1 (low-density lipoprotein receptor-related protein 1), a multifunctional endocytic receptor, has recently been identified as a hub within a biomarker network for multi-cancer clinical outcome prediction. As its role in colon cancer has not yet been characterized, we here investigate the relationship between LRP1 and outcome.

MATERIALS AND METHODS

LRP1 mRNA expression was determined in colon adenocarcinoma and paired colon mucosa samples, as well as in stromal and tumor cells obtained after laser capture microdissection. Clinical potential was further investigated by immunohistochemistry in a population-based colon cancer series (n = 307). LRP1 methylation, mutation and miR-205 expression were evaluated and compared with LRP1 expression levels.

RESULTS

LRP1 mRNA levels were significantly lower in colon adenocarcinoma cells compared with colon mucosa and stromal cells obtained after laser capture microdissection. Low LRP1 immunohistochemical expression in adenocarcinomas was associated with higher age, right-sided tumor, loss of CDX2 expression, Annexin A10 expression, CIMP-H, MSI-H and BRAFV600E mutation. Low LRP1 expression correlated with poor clinical outcome, especially in stage IV patients. While LRP1 expression was downregulated by LRP1 mutation, LRP1 promoter was never methylated.

CONCLUSIONS

Loss of LRP1 expression is associated with worse colon cancer outcomes. Mechanistically, LRP1 mutation modulates LRP1 expression.

Beyond Dysplasia Grade: The Role of Biomarkers in Stratifying Risk

Gastroenterology society guidelines recommend endoscopic surveillance as a means to detect early stage cancer in Barrett's esophagus. However, the incidence of esophageal adenocarcinoma in Western countries continues to increase, suggesting that this strategy may be inadequate. Current surveillance methods rely on the endoscopist's ability to identify suspicious areas of Barrett's esophagus to biopsy, random biopsies, and on the histopathologic diagnosis of dysplasia. This review highlights the challenges of using dysplasia to stratify cancer risk and addresses the development and use of molecular biomarkers and in vivo molecular imaging to detect early neoplasia in Barrett's esophagus.

Current and future biomarkers in the treatment of colorectal cancer

Colorectal cancer (CRC) is a leading cause of cancer deaths worldwide. CRC develops as a consequence of genomic instability, characterized by various genetic and epigenetic alterations. Its molecular heterogeneity explains the large variability in patient prognosis and treatment response, emphasizing the need for development of accurate prognostic and predictive biomarkers. This article delineates the different pathways of colorectal carcinogenesis and its molecular subtype classification. With this review, we aim to provide a comprehensive overview of the current and future biomarkers guiding clinical decision-making and CRC treatment.

Genome-Wide miRNA Analysis Identifies miR-188-3p as a Novel Prognostic Marker and Molecular Factor Involved in Colorectal Carcinogenesis

Purpose: Characterization of colorectal cancer transcriptome by high-throughput techniques has enabled the discovery of several differentially expressed genes involving previously unreported miRNA abnormalities. Here, we followed a systematic approach on a global scale to identify miRNAs as clinical outcome predictors and further validated them in the clinical and experimental setting.Experimental Design: Genome-wide miRNA sequencing data of 228 colorectal cancer patients from The Cancer Genome Atlas dataset were analyzed as a screening cohort to identify miRNAs significantly associated with survival according to stringent prespecified criteria. A panel of six miRNAs was further validated for their prognostic utility in a large independent validation cohort (n = 332). In situ hybridization and functional experiments in a panel of colorectal cancer cell lines and xenografts further clarified the role of clinical relevant miRNAs.Results: Six miRNAs (miR-92b-3p, miR-188-3p, miR-221-5p, miR-331-3p, miR-425-3p, and miR-497-5p) were identified as strong predictors of survival in the screening cohort. High miR-188-3p expression proves to be an independent prognostic factor [screening cohort: HR = 4.137; 95% confidence interval (CI), 1.568-10.917; P = 0.004; validation cohort: HR = 1.538; 95% CI, 1.107-2.137; P = 0.010, respectively]. Forced miR-188-3p expression increased migratory behavior of colorectal cancer cells in vitro and metastases formation in vivo (P < 0.05). The promigratory role of miR-188-3p is mediated by direct interaction with MLLT4, a novel identified player involved in colorectal cancer cell migration.Conclusions: miR-188-3p is a novel independent prognostic factor in colorectal cancer patients, which can be partly explained by its effect on MLLT4 expression and migration of cancer cells. Clin Cancer Res; 23(5); 1323-33. ©2016 AACR.

Optimized Multiplex Detection of 7 KRAS Mutations by Taqman Allele-Specific qPCR

Establishing the KRAS mutational status of tumor samples is essential to manage patients with colorectal or lung cancer, since these mutations preclude treatment with monoclonal anti-epidermal growth factor receptor (EGFR) antibodies. We report an inexpensive, rapid multiplex allele-specific qPCR method detecting the 7 most clinically relevant KRAS somatic mutations with concomitant amplification of non-mutated KRAS in tumor cells and tissues from CRC patients. Positive samples evidenced in the multiplex assay were further subjected to individual allele-specific analysis, to define the specific mutation. Reference human cancer DNA harbouring either G12A, G12C, G12D, G12R, G12S, G12V and G13D confirmed assay specificity with ≤1% sensitivity of mutant alleles. KRAS multiplex mutation analysis usefulness was also demonstrated with formalin-fixed paraffin embedded (FFPE) from CRC biopsies.

CONCLUSION

Co-amplification of non-mutated DNA avoided false negatives from degraded samples. Moreover, this cost effective assay is compatible with mutation detection by DNA sequencing in FFPE tissues, but with a greater sensitivity when mutant DNA concentrations are limiting.

Advances in Biomarkers: Going Beyond the Carcinoembryonic Antigen

Using biologically available markers to guide treatment decisions in colorectal cancer care is becoming increasingly common, though our understanding of these biomarkers is in its infancy. In this article, we will discuss how this area is rapidly changing, review important biomarkers being used currently, and explain how the results influence clinical decision-making. We will also briefly discuss the possibility of a liquid biopsy and explore several exciting and new options.

BATON-CRC: A Phase II Randomized Trial Comparing Tivozanib Plus mFOLFOX6 with Bevacizumab Plus mFOLFOX6 in Stage IV Metastatic Colorectal Cancer

PURPOSE

Tivozanib, a selective inhibitor of VEGFR-1, -2, and -3, plus mFOLFOX6 in an advanced gastrointestinal cancer phase Ib study had encouraging antineoplastic activity and a tolerable safety profile. This randomized, open-label, phase II trial of tivozanib/mFOLFOX6 versus bevacizumab/mFOLFOX6 in patients with previously untreated metastatic colorectal cancer (mCRC) evaluated tivozanib activity versus bevacizumab.

EXPERIMENTAL DESIGN

Treatment-naïve patients received mFOLFOX6 every 2 weeks of each 28-day cycle plus either tivozanib orally 1.5 mg once daily for 21 days or bevacizumab intravenously 5 mg/kg every 2 weeks. Investigator-assessed progression-free survival (PFS) was the primary endpoint; some secondary endpoints included safety, overall survival, overall response rate (ORR), duration of response, time to treatment failure, and biomarker subgroup analyses.

RESULTS

A prespecified interim futility analysis demonstrated that the futility boundary for superiority of tivozanib/mFOLFOX6 over bevacizumab/mFOLFOX6 for PFS in the intent-to-treat population was crossed; median PFS was 9.4 versus 10.7 months [HR = 1.091; confidence interval (CI), 0.693-1.718; P = 0.706]. Tivozanib/mFOLFOX6 resulted in PFS and ORR comparable with bevacizumab/mFOLFOX6; interim analyses biomarker results revealed no significant PFS association. Post hoc final analyses demonstrated a potential difference in tivozanib-specific PFS in patients with low neuropilin-1 (NRP-1), but not in patients with high NRP-1. Tivozanib/mFOLFOX6 was tolerable and adverse events were comparable with both bevacizumab/mFOLFOX6 and previous tivozanib studies.

CONCLUSIONS

The efficacy of tivozanib/mFOLFOX6 was comparable with but not superior to bevacizumab/mFOLFOX6 in patients with previously untreated mCRC. Since data from the prespecified interim analysis did not demonstrate superiority, this resulted in discontinuation of the study. The safety and tolerability profile of tivozanib/mFOLFOX6 was consistent with other tivozanib trials. NRP-1 is a potential predictive biomarker for tivozanib activity, but these results require further validation. Clin Cancer Res; 22(20); 5058-67. ©2016 AACR.

Prospective Evaluation of Cetuximab-Mediated Antibody-Dependent Cell Cytotoxicity in Metastatic Colorectal Cancer Patients Predicts Treatment Efficacy

Cetuximab is a monoclonal antibody to the EGFR that induces antibody-dependent cell cytotoxicity (ADCC) through Fcγ receptors on immune cells. Although SNPs in genes encoding Fcγ receptors are functionally relevant to cetuximab-mediated ADCC in colorectal cancer, a direct correlation between in vitro ADCC and clinical response to cetuximab is not defined. We therefore enrolled 96 consecutive metastatic colorectal cancer (mCRC) patients at diagnosis in a study that assessed FcγR status and cetuximab-mediated ADCC. Patients carrying the FcγRIIa H alleles 131H/Hand 131H/R had significantly higher ADCC compared with patients with the 131R/R alleles (P= 0.013). Patients carrying FcγRIIIa genotypes with the V alleles 158V/V and 158V/F displayed higher ADCC compared with patients carrying the 158F/F genotype (P= 0.001). Progression-free survival of patients with an FcγRIIIa 158V allele was significantly longer compared with patients carrying 158F/F (P= 0.05), whereas no significant difference was observed for overall survival. Twenty-eight of 50 mCRC patients with wild-type KRAS received cetuximab. The average ADCC-mediated killing was 30% of assay targets for patients who experienced cetuximab complete or partial response, 21% in patients with stable disease and 9% in patients with progressive disease. To characterize basal natural killer (NK) activity, cytotoxicity was evaluated in 39 of 96 mCRC patients. Patients who responded to first-line treatment had higher NK-cell cytotoxicity. Thus, although limited to this cohort of patients, in vitro cetuximab-mediated ADCC correlated with FcγR polymorphisms and predicted cetuximab responsiveness.

The Mutant KRAS Gene Up-regulates BCL-XL Protein via STAT3 to Confer Apoptosis Resistance That Is Reversed by BIM Protein Induction and BCL-XL Antagonism

In colorectal cancers with oncogenic GTPase Kras (KRAS) mutations, inhibition of downstream MEK/ERK signaling has shown limited efficacy, in part because of failure to induce a robust apoptotic response. We studied the mechanism of apoptosis resistance in mutant KRAS cells and sought to enhance the efficacy of a KRAS-specific MEK/ERK inhibitor, GDC-0623. GDC-0623 was shown to potently up-regulate BIM expression to a greater extent versus other MEK inhibitors in isogenic KRAS HCT116 and mutant KRAS SW620 colon cancer cells. ERK silencing enhanced BIM up-regulation by GDC-0623 that was due to its loss of phosphorylation at Ser(69), confirmed by a BIM-EL phosphorylation-defective mutant (S69G) that increased protein stability and blocked BIM induction. Despite BIM and BIK induction, the isogenic KRAS mutant versus wild-type cells remained resistant to GDC-0623-induced apoptosis, in part because of up-regulation of BCL-XL. KRAS knockdown by a doxycycline-inducible shRNA attenuated BCL-XL expression. BCL-XL knockdown sensitized KRAS mutant cells to GDC-0623-mediated apoptosis, as did the BH3 mimetic ABT-263. GDC-0623 plus ABT-263 induced a synergistic apoptosis by a mechanism that includes release of BIM from its sequestration by BCL-XL. Furthermore, mutant KRAS activated p-STAT3 (Tyr(705)) in the absence of IL-6 secretion, and STAT3 knockdown reduced BCL-XL mRNA and protein expression. These data suggest that BCL-XL up-regulation by STAT3 contributes to mutant KRAS-mediated apoptosis resistance. Such resistance can be overcome by potent BIM induction and concurrent BCL-XL antagonism to enable a synergistic apoptotic response.

Analysis of circulating DNA and protein biomarkers to predict the clinical activity of regorafenib and assess prognosis in patients with metastatic colorectal cancer: a retrospective, exploratory analysis of the CORRECT trial

BACKGROUND

Tumour mutational status is an important determinant of the response of metastatic colorectal cancer to targeted treatments. However, the genotype of the tissue obtained at the time of diagnosis might not accurately represent tumour genotype after multiple lines of treatment. This retrospective exploratory analysis investigated the clinical activity of regorafenib in biomarker subgroups of the CORRECT study population defined by tumour mutational status or plasma protein levels.

METHODS

We used BEAMing technology to identify KRAS, PIK3CA, and BRAF mutations in DNA obtained from the plasma of 503 patients with metastatic colorectal cancer who enrolled in the CORRECT trial. We quantified total human genomic DNA isolated from plasma samples for 503 patients using a modified version of human long interspersed nuclear element-1 (LINE-1) quantitive real-time PCR. We also measured the concentration of 15 proteins of interest-angiopoietin 2, interleukin 6, interleukin 8, placental growth factor, soluble TIE-1, soluble VEGFR1, VEGF-A, VEGF-C, VEGF-D, VEGF-A isoform 121, bone morphogenetic protein 7, macrophage colony-stimulating factor, stromal cell-derived factor-1, tissue inhibitor of metalloproteinase 2, and von Willebrand factor-in plasma samples from 611 patients. We did correlative analyses of overall survival and progression-free survival in patient subgroups based on mutational status, circulating DNA concentration, and protein concentrations. The CORRECT trial was registered with ClinicalTrials.gov, number NCT01103323.

FINDINGS

Tumour-associated mutations were readily detected with BEAMing of plasma DNA, with KRAS mutations identified in 349 (69%) of 503 patients, PIK3CA mutations in 84 (17%) of 503 patients, and BRAF mutations in 17 (3%) of 502 patients. We did not do correlative analysis based on BRAF genotype because of the low mutational frequency detected for this gene. Some of the most prevalent individual hot-spot mutations we identified included: KRAS (KRAS G12D, 116 [28%] of 413 mutations; G12V, 72 [17%]; and G13D, 67 [16%]) and PIK3CA (PIK3CA E542K, 27 [30%] of 89 mutations; E545K, 37 [42%]; and H1047R, 12 [14%]). 41 (48%) of 86 patients who had received anti-EGFR therapy and whose archival tumour tissue DNA was KRAS wild-type in BEAMing analysis were identified as having KRAS mutations in BEAMing analysis of fresh plasma DNA. Correlative analyses suggest a clinical benefit favouring regorafenib across patient subgroups defined by KRAS and PIK3CA mutational status (progression-free survival with regorafenib vs placebo: hazard ratio [HR] 0·52, 95% CI 0·35-0·76 for KRAS wild-type; HR 0·51, 95% CI 0·40-0·65 for KRAS mutant [KRAS wild type vs mutant, pinteraction=0·74]; HR 0·50, 95% CI 0·40-0·63 for PIK3CA wild-type; HR 0·54, 95% CI 0·32-0·89 for PIK3CA mutant [PIK3CA wild-type vs mutant, pinteraction=0·85]) or circulating DNA concentration (progression-free survival with regorafenib vs placebo: HR 0·53, 95% CI 0·40-0·71, for low circulating DNA concentrations; HR 0·52, 95% CI 0·40-0·70, for high circulating DNA concentrations; low vs high circulating DNA, pinteraction=0·601). With the exception of von Willebrand factor, assessed with the median cutoff method, plasma protein concentrations were also not associated with regorafenib activity in terms of progression-free survival. In univariable analyses, the only plasma protein that was associated with overall survival was TIE-1, high concentrations of which were associated with longer overall survival compared with low TIE-1 concentrations. This association was not significant in multivariable analyses.

INTERPRETATION

BEAMing of circulating DNA could be a viable approach for non-invasive analysis of tumour genotype in real time and for the identification of potentially clinically relevant mutations that are not detected in archival tissue. Additionally, the results show that regorafenib seems to be consistently associated with a clinical benefit in a range of patient subgroups based on mutational status and protein biomarker concentrations.

FUNDING

Bayer HealthCare Pharmaceuticals.

Integrating biomarkers in colorectal cancer trials in the West and China

The discovery of biomarkers that provide information on drug efficacy is recognized as essential for successful and cost-effective treatment of cancer. However, biomarker discovery is difficult, and requires multiple independent studies to identify a target that serves as a suitable predictor of efficacy and to ensure appropriate biomarker validation. Clinical trials that are performed, sometimes sequentially, in Europe, the USA or Asia, are often similar in their design, in part owing to regulatory, marketing, or safety considerations. We believe some of these trials offer additional unique opportunities for biomarker discovery or validation. There are multiple hurdles to overcome, such as homogenous tissue acquisition and analysis, defining and aligning biomarker hypotheses across trials, and the need to adapt sample sizes and trial designs. Nevertheless, we believe that a collaborative engagement of the academic, regulatory and pharmaceutical community can go a long way in addressing these issues and producing more-rapid results in the field of personalized medicine. In this Perspectives, we describe our views on the current fragmented approach to biomarker discovery and validation in relevant trials run within our own regions-that is, Europe, China, and the USA-and hope this article serves as a base for further reflection.

Reversal of Mutant KRAS-Mediated Apoptosis Resistance by Concurrent Noxa/Bik Induction and Bcl-2/Bcl-xL Antagonism in Colon Cancer Cells

KRAS mutations are frequently detected in human colorectal cancer and contribute to de novo apoptosis resistance and ultimately therapeutic failure. To overcome KRAS-mediated apoptosis resistance, the irreversible proteasome inhibitor, carfilzomib, was evaluated and found to potently induce Noxa, which was dependent upon c-Myc, and Bik. Isogenic mutant versus wild-type KRAS carcinoma cells showed elevated Bcl-xL, confirmed by KRAS siRNA or ectopic expression. Upregulated Bcl-xL by mutant KRAS was mediated by ERK as indicated by ERK knockdown. Bcl-xL expression was regulated at the level of mRNA and protein as shown using actinomycin D and cyclohexamide, respectively. Suppression of Bcl-xL by shRNA sensitized mutant KRAS cells to carfilzomib. Concurrent Bcl-xL antagonism by the BH3 mimetic ABT-263 combined with carfilzomib synergistically enhanced apoptosis that was dependent on Bax or p53, and was attenuated by Noxa or Bik shRNA. In support of this strategy, ectopically expressed Noxa enhanced apoptosis by ABT-263. Carfilzomib-induced Noxa and Bik sequestered Mcl-1 and ABT-263 released Bik and Bak from Bcl-xL, suggesting a mechanism for drug synergy. These preclinical findings establish mutant KRAS-mediated Bcl-xL upregulation as a key mechanism of apoptosis resistance in KRAS-mutant colorectal cancer. Furthermore, antagonizing Bcl-xL enabled carfilzomib-induced Noxa and Bik to induce synergistic apoptosis that reversed KRAS-mediated resistance.

IMPLICATIONS

This novel study reveals a promising treatment strategy to overcome apoptosis resistance in KRAS-mutant colorectal cancer by concurrent upregulation of Noxa/Bik and antagonism of Bcl-xL.