Method validation and preliminary qualification of pharmacodynamic biomarkers employed to evaluate the clinical efficacy of an antisense compound (AEG35156) targeted to the X-linked inhibitor of apoptosis protein XIAP

Autophagy alleviates amiodarone-induced hepatotoxicity

Amiodarone is a widely used antiarrhythmic drug that can cause the development of steatohepatitis as well as liver fibrosis and cirrhosis. The molecular mechanisms of amiodarone-mediated liver injury remain largely unknown. We therefore analyzed amiodarone-mediated hepatocellular injury in patients with chronic heart failure, in primary hepatocytes and HepG2 cells. We found that amiodarone-treated patients with chronic heart failure revealed significantly higher serum levels of caspase-cleaved keratin-18, an apoptosis biomarker, compared to healthy individuals or patients not receiving amiodarone. Furthermore, amiodarone treatment of hepatocytes resulted in apoptosis associated with lipid accumulation and ER-stress induction. Liver cell steatosis was accompanied by enhanced de novo lipogenesis which, after reaching peak levels, declined together with decreased activation of ER stress. The decline of amiodarone-mediated lipotoxicity was associated with protective autophagy induction. In contrast, in hepatocytes treated with the autophagy inhibitor chloroquine as well as in autophagy gene (ATG5 or ATG7)-deficient hepatocytes, amiodarone-triggered toxicity was increased. In conclusion, we demonstrate that amiodarone induces lipid accumulation associated with ER stress and apoptosis in hepatocytes, which is mirrored by increased keratin-18 fragment serum levels in amiodarone-treated patients. Autophagy reduces amiodarone-mediated lipotoxicity and could provide a therapeutic strategy for protection from drug-induced liver injury.

Plasma Tie2 is a tumor vascular response biomarker for VEGF inhibitors in metastatic colorectal cancer

Oncological use of anti-angiogenic VEGF inhibitors has been limited by the lack of informative biomarkers. Previously we reported circulating Tie2 as a vascular response biomarker for bevacizumab-treated ovarian cancer patients. Using advanced MRI and circulating biomarkers we have extended these findings in metastatic colorectal cancer (n = 70). Bevacizumab (10 mg/kg) was administered to elicit a biomarker response, followed by FOLFOX6-bevacizumab until disease progression. Bevacizumab induced a correlation between Tie2 and the tumor vascular imaging biomarker, Ktrans (R:-0.21 to 0.47) implying that Tie2 originated from the tumor vasculature. Tie2 trajectories were independently associated with pre-treatment tumor vascular characteristics, tumor response, progression free survival (HR for progression = 3.01, p = 0.00014; median PFS 248 vs. 348 days p = 0.0008) and the modeling of progressive disease (p < 0.0001), suggesting that Tie2 should be monitored clinically to optimize VEGF inhibitor use. A vascular response is defined as a 30% reduction in Tie2; vascular progression as a 40% increase in Tie2 above the nadir. Tie2 is the first, validated, tumor vascular response biomarker for VEGFi.

Immunobiological effects of gemcitabine and capecitabine combination chemotherapy in advanced pancreatic ductal adenocarcinoma

BACKGROUND

Preclinical studies suggest that chemotherapy may enhance the immune response against pancreatic cancer.

METHODS

The levels of granulocyte macrophage-colony-stimulating factor (GM-CSF) and interleukin-6 (IL-6) and the associated inflammatory marker C-reactive protein (CRP) were assessed in 38 patients receiving gemcitabine and capecitabine combination chemotherapy for advanced pancreatic cancer within the TeloVac trial. Apoptosis (M30) and total immune response (delayed-type hypersensitivity and/or T-cell response) were also assessed and levels of apoptosis induction correlated with immune response. The telomerase GV1001 vaccine was given either sequentially (n=18) or concomitantly (n=24) with the combination chemotherapy.

RESULTS

There were no differences between baseline and post-treatment levels of CRP (P=0.19), IL-6 (P=0.19) and GM-CSF (P=0.71). There was a positive correlation between post-chemotherapy CRP and IL-6 levels (r=0.45, P=0.005) and between CRP with carbohydrate antigen-19-9 (CA19-9) levels at baseline (r=0.45, P=0.015) and post treatment (r=0.40, P=0.015). The change in CRP and IL-6 levels was positively correlated (r=0.40, P=0.012). Hazard ratios (95% CI) for baseline CA19-9 (1.30 (1.07-1.59), P=0.009) and CRP (1.55 (1.00-2.39), P=0.049) levels were each independently predictive of survival. The M30 mean matched differences between pre- and post-chemotherapy showed evidence of apoptosis in both the sequential (P=0.058) and concurrent (P=0.0018) chemoimmunotherapy arms. Respectively, 5 of 10 and 9 of 20 patients had a positive immune response but there was no association with apoptosis.

CONCLUSIONS

Combination gemcitabine and capecitabine chemotherapy did not affect circulating levels of GM-CSF, IL-6 and CRP. Chemotherapy-induced apoptosis was not associated with the immunogenicity induced by the GV1001 vaccine in advanced pancreatic cancer.

Percentage Change in Plasma Cytokeratin 18 Is Associated with Clinical Outcomes in Patients Receiving Pemetrexed and Carboplatin for the Adenocarcinoma Subtype of NSCLC

BACKGROUND

The adenocarcinoma subtype of non-small cell lung cancer (adeno-NSCLC) is routinely treated with chemotherapy if patients do not have molecular aberrations such as epidermal growth factor receptor mutations or anaplastic lymphoma kinase rearrangements. There are currently no validated biomarkers that can predict if patients will gain clinical benefit from chemotherapy, leading to a majority of patients receiving many cycles of unnecessary chemotherapy. We hypothesized that the percentage rise in plasma caspase-cleaved cytokeratin 18 (cCK18) and total cytokeratin 18 (tCK18) assessed before and after chemotherapy correlates with the radiological response to chemotherapy.

METHODS

Plasma samples from 40 patients with stage IV adeno-NSCLC, treated with first-line chemotherapy with carboplatin (AUC5) plus pemetrexed (500 mg/m(2)), were collected prior to chemotherapy and 48 h after treatment. ELISA was used to quantify cCK18 and tCK18.

RESULTS

The male-to-female ratio was 3:1, and the median age of patients was 63 years. Patients who had a clinical benefit (complete response, partial response or stable disease) at the first radiological assessment following chemotherapy had a significantly higher percentage change in plasma tCK18 levels compared to those who had no clinical benefit, i.e. progressive disease (69.5 ± 75.1 vs. 25.3 ± 30.9%, respectively; p = 0.042). The receiver operating characteristic area was 0.712 (p = 0.039). There was an increase in the percentage change in cCK18 in patients with clinical benefit compared to those without clinical benefit but this was not statistically significant (57.6 ± 112.8 vs. 24.38 ± 45.1%, respectively; p = 0.85).

CONCLUSIONS

The percentage change in plasma tCK18 levels before and after the first cycle of pemetrexed and carboplatin chemotherapy is associated with clinical benefit. If validated in larger cohorts, this test can be used to identify patients unlikely to respond to treatment who can thus be offered alternative treatments or entry into clinical trials.

Circulating biomarkers in hepatocellular carcinoma

PURPOSE

Our aims are to determine levels of circulating cellular and protein biomarkers in hepatocellular carcinoma (HCC) patients and to analyse any relationships with clinical parameters.

METHODS

Fifty-four consenting patients were recruited. Circulating tumour cells (CTCs) were enumerated (by CellSearch) and characterised via filtration [by isolation by size of epithelial tumour cells (ISET)] with downstream immunohistochemistry (IHC). Glypican-3 (GPC3) expression in tumour biopsies and CTCs (by IHC) was compared, and levels of circulating caspase-cleaved and full-length cytokeratin 18 (CK18, measured using M30 and M65 ELISAs) were examined as a putative prognostic factor and marker of tumour burden.

RESULTS

CTCs were identified in 14 out of 50 (28%) patients by CellSearch and in 19 out of 19 (100%) patients by ISET. The presence of GPC3-positive CTCs by ISET was 100% concordant with the presence of GPC3-positive cells in the original tumour (n = 5). No statistically significant correlations were observed between CTC number and clinical characteristics, although trends were noted between CTC subtypes, Child-Pugh score and tumour node metastasis stage. Serum M30 and M65 levels (as continuous variables) significantly correlated with overall survival (OS) in a univariate analysis (p = 0.003 and p < 0.001, respectively); M65 levels remained statistically significant in a multivariate analysis (p = 0.029).

CONCLUSIONS

This is the first study to detect GPC3-positive CTCs in HCC, important for drug development with this target. The significant association of circulating CK18 with OS in HCC further exemplifies the utility of circulating biomarkers in cancer.

Targeting cell death signaling in colorectal cancer: Current strategies and future perspectives

The evasion from controlled cell death induction has been considered as one of the hallmarks of cancer cells. Defects in cell death signaling are a fundamental phenomenon in colorectal cancer. Nearly any non-invasive cancer treatment finally aims to induce cell death. However, apoptosis resistance is the major cause for insufficient therapeutic success and disease relapse in gastrointestinal oncology. Various compounds have been developed and evaluated with the aim to meet with this obstacle by triggering cell death in cancer cells. The aim of this review is to illustrate current approaches and future directions in targeting cell death signaling in colorectal cancer. The complex signaling network of apoptosis will be demonstrated and the “druggability” of targets will be identified. In detail, proteins regulating mitochondrial cell death in colorectal cancer, such as Bcl-2 and survivin, will be discussed with respect to potential therapeutic exploitation. Death receptor signaling and targeting in colorectal cancer will be outlined. Encouraging clinical trials including cell death based targeted therapies for colorectal cancer are under way and will be demonstrated. Our conceptual understanding of cell death in cancer is rapidly emerging and new types of controlled cellular death have been identified. To meet this progress in cell death research, the implication of autophagy and necroptosis for colorectal carcinogenesis and therapeutic approaches will also be depicted. The main focus of this topic highlight will be on the revelation of the complex cell death concepts in colorectal cancer and the bridging from basic research to clinical use.

Inhibitor of apoptosis proteins as targets for anticancer therapy

Cell death by apoptosis plays a critical role in regulating the subtle balance between cell death and proliferation to maintain tissue homeostasis. Accordingly, tipping the balance in either direction may cause human disease. Too little cell death may promote tumor formation and progression. In addition, killing of cancer cells by current therapies is largely due to induction of apoptosis in tumor cells. Since a hallmark of human cancers is their resistance to apoptosis, there is a demand to develop novel strategies that restore the apoptotic machinery in order to overcome cancer resistance. Inhibitor of apoptosis proteins (IAPs) block apoptosis at the core of the apoptotic machinery by inhibiting caspases. Elevated levels of IAPs are found in many human cancers and have been associated with poor prognosis. Recent insights into the role of IAPs have provided the basis for various exciting developments that aim to modulate the expression or function of IAPs in human cancers. Targeting IAPs (e.g., by antisense approaches or small-molecule inhibitors) presents a promising novel approach to either directly trigger apoptosis or to potentiate the efficacy of cytotoxic therapies in cancer cells. Thus, inhibition of IAPs such as X chromosome-linked IAP may prove to be a successful strategy to overcome apoptosis resistance of human cancers that deserves further exploitation.

A phase 1 trial of intravenous 4-(N-(S-glutathionylacetyl)amino) phenylarsenoxide (GSAO) in patients with advanced solid tumours

BACKGROUND

4-(N-(S-glutathionylacetyl)amino) phenylarsenoxide (GSAO) is a water-soluble mitochondrial toxin that binds to adenine nucleotide translocase in the inner mitochondrial membrane, thereby targeting cell proliferation. This phase 1 study investigated safety, dose-limiting toxicities (DLTs), maximum tolerated dose (MTD) and pharmacokinetics (PK) of GSAO as a daily 1-h infusion for 5 days a week for 2 weeks in every three. Pharmacodynamics of GSAO was evaluated by dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and circulating markers of angiogenesis.

METHODS

Patients with advanced solid tumours received GSAO in a dose-escalation trial according to a standard '3 + 3' design that was guided by toxicity and, for the final dose escalation, by arsenic PK data.

RESULTS

A total of 34 patients were treated with GSAO across 9 dose levels (1.3-44.0 mg/m(2)). Treatment was well tolerated with few adverse events. An additional three patients were enrolled at the 12.4 mg/m(2) dose level following a DLT of derangement of liver function tests (grade 4). At the 44.0 mg/m(2) dose level, two out of three patients had DLTs (reversible encephalopathy; paroxysmal atrial fibrillation).

CONCLUSIONS

The MTD of GSAO was 22.0 mg/m(2)/day. There was no biomarker evidence from DCE-MRI or circulating markers of angiogenesis of an anti-vascular effect of GSAO.

A high serum level of M65 is associated with tumour aggressiveness and an unfavourable prognosis for epithelial ovarian cancer

PURPOSE

This study was conducted to determine the clinical significance of serum M30 and M65 in epithelial ovarian cancer (EOC).

METHODS

A total of 56 patients with EOC and 56 healthy women were included in the study. All of the patients received platinum-based chemotherapy. Pretreatment levels of M30 and M65 were measured using the quantitative ELISA method.

RESULTS

The median M30 and M65 serum levels were significantly elevated in the EOC patients compared with the healthy controls (96.7 vs. 69.5, p = 0.028 and 436.4 versus 166.3, p < 0.001, respectively). The cut-off value of 423.4 U/L for M65 determined with ROC analysis, predicted progression with 75.1 % sensitivity and 65.6 % specificity (AUC = 0.708, p = 0.008). Patients with higher M65 levels had shorter progression-free survival (PFS) (p = 0.021). Both M30 and M65 serum levels were significantly higher for serous-type histology (p = 0.001 and p < 0.001, respectively). Increased M65 serum levels were associated with advanced disease (p = 0.005) and higher grade (p = 0.005). Moreover, M65 levels were higher for chemotherapy-resistant patients (p = 0.04). Multivariate analysis revealed that an elevated serum M65 level was the only significant independent prognostic factor (p = 0.039, HR 3.792).

CONCLUSIONS

These results indicated that serum M30 and M65 levels were significantly elevated in patients with EOC compared with healthy women. Particularly, high serum M65 levels were associated with poor prognosis and resistance to platinum-based chemotherapy.

Multi-level evidence that circulating CK18 is a biomarker of tumour burden in colorectal cancer

Background:

Circulating total cytokeratin 18 (tCK18) and/or caspase cleaved cytokeratin 18 (cCK18) (measured by M65 and M30 enzyme-linked immunosorbent assays (ELISAs), respectively) are used as pharmacodynamic (PD) biomarkers of epithelial cell death in clinical trials. Having validated these ELISAs, we assessed their utility in colorectal cancer (CRC).

Methods:

We applied the assays in several settings: 53 controls; 97 patients undergoing surgery and 74 patients with metastatic CRC undergoing chemotherapy (55 first line; 56 patients with repeated sampling through chemotherapy). Prognostic significance was evaluated using Kaplan–Meier life tables and Cox models; PD utility was assessed by analysis of repeated measures.

Results:

Median cCK18 and tCK18 levels were elevated in patients with cancer (both P=0.0001), and among cancer patients, there were increasing trends from early to advanced stages (both P_trends=0.0001). Increasing tCK18 predicted for reduced survival after surgery with curative intent (adjusted hazard ratio (HR) for doubling in concentration 1.77, 95% CI: 1.04, 3.01) and after first-line chemotherapy in metastatic disease (adjusted HR per doubling in concentration=1.78, 95% CI: 1.37, 2.30). In patients with progressive disease during chemotherapy, repeated sampling revealed profiles with high baselines and progressive upwardly increases after cycle 1.

Conclusion:

This study provides evidence for cytokeratin 18 (CK18) as a prognostic and PD biomarker in patients with CRC and supports continued deployment of circulating CK18 in biomarker-enhanced trials.

A pilot study assessing the prognostic value of CK18 and nDNA biomarkers in severe sepsis patients

BACKGROUND AND OBJECTIVES

Severe sepsis and septic shock have posed significant treatment challenges for many years. Recently, a number of circulating apoptosis biomarkers have emerged, such as full-length and caspase-cleaved cytokeratin 18 (CK18) and nucleosomal DNA (nDNA), that may be predictive of likely outcome. This non-interventional study aimed to assess the ability of enzyme-linked immunosorbent assays (ELISAs) for these biomarkers to provide clinically useful information to guide the management of sepsis.

METHODS

This study was conducted in patients admitted to the intensive care unit with severe sepsis at five US centres. Blood samples for assessment of plasma levels of full-length CK18 (measured by the M65® ELISA) and caspase-cleaved CK18 (measured by the M30-Apoptosense® ELISA) and nDNA (measured by ELISA) were collected from patients within 2 hours of consent (baseline) and on days 2, 4 and 8. Blood samples from 17 healthy volunteers acted as controls. Levels of each biomarker were presented descriptively.

RESULTS

A total of 22 patients (mean age 60 [range, 24-83] years; 50% male) were included in the study. The mean APACHE II score was 24.4 (range 7-50). One-third of patients had three organ system failures and over one-half had septic shock. Three patients died during the study. Full-length and caspase-cleaved CK18 levels decreased within 48 hours following initiation of treatment of sepsis in patients who survived, whereas increases were observed in the same timeframe in patients who died within 28 days of admission. Baseline nDNA and total soluble CK18 levels (caspase-cleaved and total intact) were significantly (p ≤ 0.05) higher in patients who required renal support than those who did not.

CONCLUSIONS

Despite the small numbers of subjects assessed in the current study, these results confirm that measurement of apoptosis biomarkers may help to provide clinically useful information to manage sepsis and expedite development of novel therapeutics. However, further investigations to fully assess their prognostic value are required.

Investigation of bendamustine HCL in a phase 2 study in women with resistant ovarian cancer

We investigated the safety and efficacy of 90 mg/m(2) bendamustine HCL, administered intravenously on days 1 and 2 every 28 days in 10 women with platinum and taxane resistant epithelial ovarian cancer. There were no objective tumor responses observed; 2 patients had stable disease. Plasma samples collected at pre-treatment and end of cycle one were analyzed for changes in circulating total cytokeratin 18 and caspase cleaved cytokeratin 18 as exploratory early biomarkers of bendamustine-induced tumor cell death. All patients had measureable levels of both total and cleaved caspase 3 cytokeratin 18, but no relationship with response was possible due to the lack of clinical benefit in treated patients. Due to the high incidence of adverse events and absence of objective responses, only ten patients were treated as predefined by the Simon Two-Stage Design in the protocol. Overall, the regimen was not well tolerated and was associated with fatigue and a greater number of gastrointestinal side effects as compared to previously reported experiences in different patient populations. However, our study subjects did experience less bone marrow suppression. The lack of tolerability could reflect the degree of tumor burden within the peritoneal cavity as well as the high number of prior regimens (median of 5) received by the patients participating in this study.

Evaluation of cell death mechanisms induced by the vascular disrupting agent OXi4503 during a phase I clinical trial

Background:

OXi4503 is a tubulin-binding vascular disrupting agent that has recently completed a Cancer Research UK-sponsored phase I trial. Preclinical studies demonstrated early drug-induced apoptosis in tumour endothelial cells at 1–3 h and secondary tumour cell necrosis between 6 and 72 h.

Methods:

To capture both possible outcomes of OXi4503 treatment on cell death, plasma samples for analysis by M30 and M65 ELISAs, which measure different circulating forms of cytokeratin 18 as biomarkers of apoptosis and necrosis, respectively, were collected from patients entered into the trial at early (4/6 h) and later time points (24 h, day 8 and day 15).

Results:

OXi4503 induced a selective dose-dependent elevation in M30 antigen levels (apoptosis) at 4/6 h and a similar elevation in M65 antigen levels at 24 h (necrosis) consistent with its preclinical cell death profile. For the purposes of investigating potential biomarker relationships to patient characteristics, the trial population was divided into three groups based on radiological and clinical response: (a) early progression, (b) progressive disease and (c) stable disease (SD)/partial response. A significant increase in antigen concentrations was measured by M65 at 24 h in the SD group compared with the two other groups (P=0.015, mean increase 30.9%).

Conclusion:

These results provide pharmacodynamic evidence of drug mechanism of action in cancer patients and highlight the M65 ELISA as a potentially useful biomarker assay of response to OXi4503.

Phase II study of single-agent navitoclax (ABT-263) and biomarker correlates in patients with relapsed small cell lung cancer

PURPOSE

Bcl-2 is a critical regulator of apoptosis that is overexpressed in the majority of small cell lung cancers (SCLC). Nativoclax (ABT-263) is a potent and selective inhibitor of Bcl-2 and Bcl-x(L). The primary objectives of this phase IIa study included safety at the recommended phase II dose and preliminary, exploratory efficacy assessment in patients with recurrent and progressive SCLC after at least one prior therapy.

EXPERIMENTAL DESIGN

Thirty-nine patients received navitoclax 325 mg daily, following an initial lead-in of 150 mg daily for 7 days. Study endpoints included safety and toxicity assessment, response rate, progression-free and overall survival (PFS and OS), as well as exploratory pharmacodynamic correlates.

RESULTS

The most common toxicity associated with navitoclax was thrombocytopenia, which reached grade III-IV in 41% of patients. Partial response was observed in one (2.6%) patient and stable disease in 9 (23%) patients. Median PFS was 1.5 months and median OS was 3.2 months. A strong association between plasma pro-gastrin-releasing peptide (pro-GRP) level and tumor Bcl-2 copy number (R = 0.93) was confirmed. Exploratory analyses revealed baseline levels of cytokeratin 19 fragment antigen 21-1, neuron-specific enolase, pro-GRP, and circulating tumor cell number as correlates of clinical benefit.

CONCLUSION

Bcl-2 targeting by navitoclax shows limited single-agent activity against advanced and recurrent SCLC. Correlative analyses suggest several putative biomarkers of clinical benefit. Preclinical models support that navitoclax may enhance sensitivity of SCLC and other solid tumors to standard cytotoxics. Future studies will focus on combination therapies.

Biomarkers of cell death applicable to early clinical trials

The development of biomarkers of cell death to reflect tumor biology and drug-induced response has garnered interest with the development of several classes of drugs aimed at decreasing the cellular threshold for apoptosis and exploiting pre-existing oncogenic stresses. These novel anticancer drugs, directly targeted to the apoptosis regulatory machinery and aimed at abrogating survival signaling pathways, are entering early clinical trials provoking the question of how to monitor their impact on cancer patients. The parallel development of drugs with predictive biomarkers and their incorporation into early clinical trials are anticipated to support the pharmacological audit trail, to speed the development and reduce the attrition rate of novel drugs whose objective is to provoke tumor cell death. Tumor biopsies are an ideal matrix to measure apoptosis, but surrogate less invasive biomarkers such as blood samples and functional imaging are less challenging to acquire clinically. Archetypal and exploratory examples illustrating the importance of biomarkers to drug development are given. This review explores the substantive challenges associated with the validation, deployment, interpretation and utility of biomarkers of cell death and reviews recent advances in their incorporation in preclinical and early clinical trial contexts.

Pharmacodynamic modelling of biomarker data in oncology

The development of pharmacodynamic (PD) biomarkers in oncology has implications for design of clinical protocols from preclinical data and for predicting clinical outcomes from early clinical data. Two classes of biomarkers have received particular attention. Phosphoproteins in biopsy samples are markers of inhibition of signalling pathways, target sites for many novel agents. Biomarkers of apoptosis in plasma can measure tumour cell killing by drugs in phase I clinical trials. The predictive power of PD biomarkers is enhanced by data modelling. With pharmacokinetic models, PD models form PK/PD models that predict the time course both of drug concentration and drug effects. If biomarkers of drug toxicity are also measured, the models can predict drug selectivity as well as efficacy. PK/PD models, in conjunction with disease models, make possible virtual clinical trials, in which multiple trial designs are assessed in silico, so the optimal trial design can be selected for experimental evaluation.

Application of the β-expectation tolerance interval to method validation of the M30 and M65 ELISA cell death biomarker assays

Method validation should focus on demonstrating that an assay is fit for its intended purpose. We have applied the β-expectation tolerance interval - a statistical approach that predicts the accuracy of assay measurements in the future - to the validation of two different cell death biomarker assays, the M30 and M65 ELISAs. A meta-analysis was conducted on a total of 57 different M30 and M65 assays run over a 2 year period. All code utilised in calculations was developed using MATLAB. The optimal fit to the calibration curve for the M30 assay was shown to be a quartic curve which yielded a β-expectation tolerance interval of +20.5% and -23.6% at β=95% over a wide range of QC standards (88-810 U/L). However, such a fit required at least 7 points to avoid problems with over fitting. A linear fit to the M65 calibration curve normally produced a tolerance interval of less than ±20%, however, marked inter-batch variations were evident. Amelioration of batch to batch variations was accomplished by fitting M65 calibration data preferably to a 4-parameter logistic function or a cubic spline. The minimum number of QC replicates and different assays required to produce reliable accuracy profiles was determined. The β-expectation tolerance interval approach has resulted in further optimisation of the M30 and M65 ELISAs as biomarker assays that should translate into greater accuracy in results generated from clinical trials samples.

Phase I study of Navitoclax (ABT-263), a novel Bcl-2 family inhibitor, in patients with small-cell lung cancer and other solid tumors

PURPOSE

Resistance to chemotherapy-induced apoptosis represents a major obstacle to cancer control. Overexpression of Bcl-2 is seen in multiple tumor types and targeting Bcl-2 may provide therapeutic benefit. A phase I study of navitoclax, a novel inhibitor of Bcl-2 family proteins, was conducted to evaluate safety, pharmacokinetics, and preliminary efficacy in patients with solid tumors.

PATIENTS AND METHODS

Patients enrolled to intermittent dosing cohorts received navitoclax on day -3, followed by dosing on days 1 to 14 of a 21-day cycle. Patients on continuous dosing received a 1-week lead-in dose of 150 mg followed by continuous daily administration. Blood samples were collected for pharmacokinetic analyses, biomarker analyses, and platelet monitoring.

RESULTS

Forty-seven patients, including 29 with small-cell lung cancer (SCLC) or pulmonary carcinoid, were enrolled between 2007 and 2008, 35 on intermittent and 12 on continuous dosing cohorts. Primary toxicities included diarrhea (40%), nausea (34%), vomiting (36%), and fatigue (34%); most were grade 1 or 2. Dose- and schedule-dependent thrombocytopenia was seen in all patients. One patient with SCLC had a confirmed partial response lasting longer than 2 years, and eight patients with SCLC or carcinoid had stable disease (one remained on study for 13 months). Pro-gastrin releasing peptide (pro-GRP) was identified as a surrogate marker of Bcl-2 amplification and changes correlated with changes in tumor volume.

CONCLUSION

Navitoclax is safe and well tolerated, with dose-dependent thrombocytopenia as the major adverse effect. Preliminary efficacy data are encouraging in SCLC. Efficacy in SCLC and the utility of pro-GRP as a marker of treatment response will be further evaluated in phase II studies.

Ubiquitin-like protein conjugation and the ubiquitin-proteasome system as drug targets

Ubiquitin is a highly conserved 76 amino-acid protein that covalently attaches to protein substrates targeted for degradation by the 26S proteasome. The coordinated effort of a series of enzymes, including an activating enzyme (E1), a conjugating enzyme (E2) and a ligase (E3), uses ATP to ultimately form an isopeptide bond between ubiquitin and a substrate.

Another class of enzymes called deubiquitylating enzymes (DUBs) deconstruct these linkages and also have an essential role in ubiquitin function. In addition, ubiquitin-like proteins (UBLs), including NEDD8, SUMO and ISG15, share a characteristic three-dimensional fold with ubiquitin but have their own dedicated enzyme cascades and distinct (although sometimes overlapping) biological functions.

The ubiquitin–proteasome system (UPS) and UBL conjugation pathways have important roles in various human diseases, including numerous types of cancer, cardiovascular disease, viral diseases and neurodegenerative disorders. The proteasome inhibitor bortezomib (Velcade; Millennium Pharmaceuticals) is the first clinically validated drug to target the UPS and is approved for the treatment of multiple myeloma. This suggests that other diseases may conceivably be targeted by modulating components of the UPS and UBL conjugation pathways using small-molecule inhibitors.

A significant hurdle to identifying drug-like inhibitors of enzyme targets within the UPS and UBL conjugation pathways is the limited understanding of the molecular mechanisms and biological consequences of UBL conjugation.

Here, we provide an overview of the enzyme classes in the UPS and UBL pathways that are potential therapeutic targets, and highlight considerations that are important for drug discovery. We also discuss the progress in the development of small-molecule inhibitors, and review developments in understanding of the role of the components of the UPS and the UBL pathways in disease and their potential for therapeutic intervention.

The ubiquitin–proteasome system (UPS) and ubiquitin-like protein (UBL) conjugation pathways are integral to cellular protein homeostasis, and their functional importance in various diseases, including cancer, cardiovascular disease and neurodegenerative disorders, is now beginning to emerge. Brownell and colleagues review developments in understanding of the role of the components of the UPS and the UBL pathways in disease and their potential for therapeutic intervention.

The ubiquitin–proteasome system (UPS) and ubiquitin-like protein (UBL) conjugation pathways are integral to cellular protein homeostasis. The growing recognition of the fundamental importance of these pathways to normal cell function and in disease has prompted an in-depth search for small-molecule inhibitors that selectively block the function of these pathways. However, our limited understanding of the molecular mechanisms and biological consequences of UBL conjugation is a significant hurdle to identifying drug-like inhibitors of enzyme targets within these pathways. Here, we highlight recent advances in understanding the role of some of these enzymes and how these new insights may be the key to developing novel therapeutics for diseases including immuno-inflammatory disorders, cancer, infectious diseases, cardiovascular disease and neurodegenerative disorders.

Serum efficacy biomarkers for oncology

Considerable interest has emerged in serum biomarkers that can be used to evaluate early effects of cancer therapeutics. Such efficacy biomarkers are expected to become valuable both for routine clinical care and for anticancer drug development. Here, we review the literature on serum efficacy biomarkers. We discuss how data using such markers can be interpreted, particularly with regard to the issue of specificity of different markers. An important question is whether biomarker response evaluation is expected to be congruent with evaluation by traditional anatomical methods. We argue that they may not be - biomarkers are expected to provide information with regard to induction of tumor cell death that will not necessarily reflect clinical outcome.

Issues on fit-for-purpose validation of a panel of ELISAs for application as biomarkers in clinical trials of anti-Angiogenic drugs

Background:

Successful introduction of new anticancer agents into the clinic is often hampered by a lack of qualified biomarkers. Studies have been conducted of 17 ELISAs representing a potential panel of pharmacodynamic/predictive biomarkers for drugs targeted to tumour vasculature.

Methods:

The fit-for-purpose approach to method validation was used. Stability studies were performed using recombinant proteins in surrogate matrices, endogenous analytes in healthy volunteer and cancer patient plasma. The impact of platelet depletion was investigated.

Results:

Method validation focused on measuring precision and showed that 15 of the 17 assays were within acceptable limits. Stability at −80°C was shown for 3 months with all recombinant proteins in surrogate matrices, whereas under the same conditions instability was observed with KGF in platelet-rich and platelet-depleted plasma, and with PDGF-BB in platelet-depleted plasma from cancer patients. For measurement of extracellular circulating analytes, platelet depletion should be conducted before freezing of plasma to prevent release of PDGF-BB, FGFb and VEGF-A. A protocol was developed to remove >90% platelets from plasma requiring centrifugation at 2000 g for 25 min.

Conclusions:

These studies highlight the need for assay validation and crucial assessment of sample handling issues before commencement of biomarker analysis in clinical trials.

Apoptosis: a clinically useful measure of antiretroviral drug toxicity?

Antiretroviral therapy (ART) has improved life expectancy with HIV infection, but long-term toxicities associated with these medications are now a major global disease burden. There is a clear need to develop useful methods for monitoring patients on antiretroviral drugs for early signs of toxicity. Assays with predictive utility -- allowing therapy to be changed before serious end organ damage occurs -- would be ideal. Attempts to develop biochemical methods of monitoring ART toxicity have concentrated on the mitochondrial toxicity of nucleoside analogue reverse transcriptase inhibitors and have not generally lead to assays with widespread clinical applications. For example, plasma lactate and peripheral blood measurements of mitochondrial DNA associate with exposure to potentially toxic nucleoside analogue reverse transcriptase inhibitors but have not reliably predicted clinical toxicity. Better assays are needed, including markers of toxicity from additional drug classes. Apoptosis may be a potential marker of ART toxicity. Increased apoptosis has been demonstrated both in vitro and in vivo in association with various antiretroviral drug classes and a range of clinical toxicities. However, quantifying apoptosis on biopsy specimens of tissue (such as adipose tissue) is impractical for patient monitoring. Novel assays have been described that can quantify apoptosis using minute tissue samples and initial results from clinical samples suggest peripheral blood may have utility in predicting ART toxicities. The limitations and potential of such techniques for monitoring patients for drug side effects will be discussed.

Circulating cytokeratin 18 fragment m65-a potential marker of malignancy in colorectal cancer patients

Soluble cytokeratin 18 fragments (M30, M65) are released from human cancer cells during cell death and hold potential as biomarkers in colorectal cancer characterized by frequent metastatic spread. A total of 62 colorectal cancer and 27 control patients were included in the study. M65 (necrosis and apoptosis) and M30 (apoptosis) were quantified preoperatively (n = 62) and postoperatively (n = 31) using specific enzyme-linked immunosorbent assays. Presence of disseminated tumor cells (DTC) in the bone marrow was assessed by staining of A45-B/B3-positive cells in aspirates. M65 was significantly elevated in patients with International Union against Cancer stage I and IIA tumors compared to controls. A subgroup (19/31) exhibited a significant (p < 0.05) decrease of M65 after tumor surgery (503.9 +/- 230.7 to 342.6 + 94.8 U/l; -32.0 +/- 16.5%), in contrast to 12 patients who revealed higher M65 levels postoperatively (386.5 +/- 128.5 to 519.1 +/- 151 U/l; +37.4 +/- 32.3%). DTC in bone marrow were found in 10% (2/19) of patients with decreasing and 50% (6/12) of the patients with increasing M65 serum concentrations after surgery (p = 0.028). In conclusion, M65 as marker is likely to be valuable to identify patients with a high incidence of systemic disease.

Mechanism-based bioanalysis and biomarkers for hepatic chemical stress

Adverse drug reactions, in particular drug-induced hepatotoxicity, represent a major challenge for clinicians and an impediment to safe drug development. Novel blood or urinary biomarkers of chemically-induced hepatic stress also hold great potential to provide information about pathways leading to cell death within tissues. The earlier pre-clinical identification of potential hepatotoxins and non-invasive diagnosis of susceptible patients, prior to overt liver disease is an important goal. Moreover, the identification, validation and qualification of biomarkers that have in vitro, in vivo and clinical transferability can assist bridging studies and accelerate the pace of drug development. Drug-induced chemical stress is a multi-factorial process, the kinetics of the interaction between the hepatotoxin and the cellular macromolecules are crucially important as different biomarkers will appear over time. The sensitivity of the bioanalytical techniques used to detect biological and chemical biomarkers underpins the usefulness of the marker in question. An integrated analysis of the biochemical, molecular and cellular events provides an understanding of biological (host) factors which ultimately determine the balance between xenobiotic detoxification, adaptation and liver injury. The aim of this review is to summarise the potential of novel mechanism-based biomarkers of hepatic stress which provide information to connect the intracellular events (drug metabolism, organelle, cell and whole organ) ultimately leading to tissue damage (apoptosis, necrosis and inflammation). These biomarkers can provide both the means to inform the pharmacologist and chemist with respect to safe drug design, and provide clinicians with valuable tools for patient monitoring.

Evaluation of circulating tumor cells and serological cell death biomarkers in small cell lung cancer patients undergoing chemotherapy

Serological cell death biomarkers and circulating tumor cells (CTCs) have potential uses as tools for pharmacodynamic blood-based assays and their subsequent application to early clinical trials. In this study, we evaluated both the expression and clinical significance of CTCs and serological cell death biomarkers in patients with small cell lung cancer. Blood samples from 88 patients were assayed using enzyme-linked immunosorbent assays for various cytokeratin 18 products (eg, M65, cell death, M30, and apoptosis) as well as nucleosomal DNA. CTCs (per 7.5 ml of blood) were quantified using Veridex CellSearch technology. Before therapeutic treatment, cell death biomarkers were elevated in patients compared with controls. CTCs were detected in 86% of patients; additionally, CD56 was detectable in CTCs, confirming their neoplastic origin. M30 levels correlated with the percentage of apoptotic CTCs. M30, M65, lactate dehydrogenase, and CTC number were prognostic for patient survival as determined by univariate analysis. Using multivariate analysis, both lactate dehydrogenase and M65 levels remained significant. CTC number fell following chemotherapy, whereas levels of serological cell death biomarkers peaked at 48 hours and fell by day 22, mirroring the tumor response. A 48-hour rise in nucleosomal DNA and M30 levels was associated with early response and severe toxicity, respectively. Our results provide a rationale to include the use of serological biomarkers and CTCs in early clinical trials of new agents for small cell lung cancer.

Targeting the ubiquitin system in cancer therapy

The ubiquitin system is a network of proteins dedicated to the ubiquitylation of cellular targets and the subsequent control of numerous cellular functions. The deregulation of components of this elaborate network leads to human pathogenesis, including the development of many types of tumour. Alterations in the ubiquitin system that occur during the initiation and progression of cancer are now being uncovered, and this knowledge is starting to be exploited for both molecular diagnostics and the development of novel strategies to combat cancer.

'Fit-for-purpose' validation of SearchLight multiplex ELISAs of angiogenesis for clinical trial use

Validated assays of circulating biomarkers of angiogenesis to predict and determine the efficacy of vascular-targeted anticancer drugs would facilitate successful drug development. Multiple biomarker candidates exist and a multiplex approach was sought to minimise the requisite patient blood volume and to aid selection of those biomarkers with greatest potential clinical utility. Validation of the SearchLight multiplex ELISA platform comprising two multiplex assays of nine potential angiogenesis biomarkers was conducted (plex 1; VEGF R1 and R2, IL-8, KGF, PlGF; plex 2; PDGFbb, HGF, FGFb and VEGF). The study focused on instrument qualification, analyte specificity within the multiplex format, assay precision and reproducibility. No evidence was found within the multiplex that signals output from one analyte impinged on another or that antibody cross-reactivity occurred. Spike recovery for 5 between-experiment repeats was within +/-15% of input values for 7 of the 9 multiplexed analytes, with a coefficient of variation (CV) of <20% for 6 of the 9 analytes. Plasma samples from 8 ovarian cancer patients (who were not receiving therapy) were assessed using the two multiplexes on this platform to explore the likely baseline variability in this disease context. This study suggests that the platform and the multiplex approach will be useful to evaluate pharmacodynamic responses to vascular targeted therapy in early clinical trials.

Biomarkers of apoptosis

Within the era of molecularly targeted anticancer agents, it has become increasingly important to provide proof of mechanism as early on as possible in the drug development cycle, especially in the clinic. Selective activation of apoptosis is often cited as one of the major goals of cancer chemotherapy. Thus, the present minireview focuses on a discussion of the pros and cons of a variety of methodological approaches to detect different components of the apoptotic cascade as potential biomarkers of programmed cell death. The bulk of the discussion centres on serological assays utilising the technique of ELISA, since here there is an obvious advantage of sampling multiple time points. Potential biomarkers of apoptosis including circulating tumour cells, cytokeratins and DNA nucleosomes are discussed at length. However, accepting that a single biomarker may not have the power to predict proof of concept and patient outcome, it is clear that in the future more emphasis will be placed on technologies that can analyse panels of biomarkers in small volumes of samples. To this end the increased throughput afforded by multiplex ELISA technologies is discussed.

Elevated serum levels of M30 and M65 in patients with locally advanced head and neck tumors

BACKGROUND

M30-Apoptosense and M65 ELISAs can detect caspase cleaved and intact forms of cytokeratin 18. As biologic marker of cell death, both assays can be useful to evaluate prognosis and chemotherapy response in the patients with breast, lung, and endometrium cancer. In the present study, we measured serum M30 and M65 levels in the patients with locally advanced head and neck tumors, and compared with healthy controls.

MATERIALS AND METHODS

A total of 40 consecutive patients with locally advanced head and neck tumors were included in this study. The sera were collected from the patients and 32 healthy controls. Median age was 51 years (range: 19-80) and squamous cell carcinoma of head and neck was major histopathologic subtype. Primary tumors were localized in larynx, nasopharynx, hypopharynx and tongue. The mean serum M30 concentration was 112.7+/-59 U/L in patients and this was significantly higher than healthy controls (mean 106.5+/-17.6 U/L) (p<0.05). Serum M65 levels were also higher in patients with head and neck tumors when compared to controls but not statistically significant (261.7+/-175 U/L vs 200.2+/-164.5 U/L, p=0.077). There was no statistically significant correlation among age, stage and localization of tumor and serum M30 and M65 levels.

CONCLUSION

According to our knowledge, this is the first study which evaluated serum M30 and M65 levels in head and neck tumors. We found increased serum levels of M30 and M65 levels in head and neck tumors. Significantly higher levels of serum M30 may have prognostic importance in this type of tumor. Larger studies are needed to evaluate its' prognostic importance.

Phase I trial of AEG35156 administered as a 7-day and 3-day continuous intravenous infusion in patients with advanced refractory cancer

PURPOSE

To establish the maximum-tolerated dose and evaluate tolerability, pharmacokinetics, pharmacodynamic effects, and antitumor activity of AEG35156, a second-generation antisense to X-linked inhibitor of apoptosis (XIAP) protein, in patients with advanced refractory malignant tumors.

PATIENTS AND METHODS

This was a first-in-man, open-label, phase I dose-escalation study. AEG35156 was administered by continuous intravenous infusion over 7 days (7DI) or 3 days (3DI) of a 21-day treatment cycle. Dose escalation started at 48 mg/m(2)/d and continued until consistent dose-limiting toxicity (DLT) was observed.

RESULTS

Thirty-eight patients were entered in seven cohorts. Grade 3 to 4 adverse events were uncommon and were predominantly abnormal laboratory values: elevated ALT, thrombocytopenia, and lymphopenia. DLTs comprised elevated hepatic enzymes, hypophosphatemia, and thrombocytopenia. The maximum-tolerated doses were defined as 125 mg/m(2)/d for the 7DI regimen and < or = 213 mg/m(2)/d for the 3DI schedule. AEG35156 area under the plasma concentration curve and peak plasma concentration increased proportionally with dose. Suppression of XIAP mRNA levels was maximal at 72 hours (mean suppression, 21%), and this coincided with a dramatic decrease in circulating tumor cells in a patient with non-Hodgkin's lymphoma. Two further patients had unconfirmed partial responses. Circulating biomarkers of cell death and apoptosis altered in association with drug infusion and toxicity.

CONCLUSION

In this first-in-man study, AEG35156 was well tolerated, with predictable toxicities, pharmacokinetic properties, and clinical evidence of antitumor activity in patients with refractory lymphoma, melanoma, and breast cancer. Phase I/II trials of AEG35156 chemotherapy combinations are ongoing in patients with pancreatic, breast, non-small-cell lung cancer, acute myeloid leukemia, lymphoma, and solid tumors for which docetaxel is indicated.

Measuring soluble forms of extracellular cytokeratin 18 identifies both apoptotic and necrotic mechanisms of cell death produced by adenoviral-mediated interferon alpha: possible use as a surrogate marker

Adenoviral transduction of human bladder cancer cells with human interferon α-2b (Ad-IFN) produces cancer specific cell death via direct and indirect mechanisms. The indirect mechanisms involve the secreted IFN produced which kill IFN protein sensitive cancer cells as well as yet unidentified bystander factors which are cytotoxic to neighboring cancer cells. The direct cell kill results from transfection and expression of Ad-IFN in the cancer cells. Since the molecular forms of cytokeratin 18 (CK18), either caspase cleaved or not, have been associated with apoptotic or necrotic cell death, respectively, we determined if increases in either or both CK18 forms could be observed following IFNα protein or Ad-IFN treatment of bladder carcinoma cells. Quantification of M30 and M65 ELISAs (assays for CK18 associated apoptotic and necrotic cell death, respectively) were used as surrogate markers of the cell death produced. In the IFN protein sensitive RT4 bladder cancer cells IFN produced primarily M30 related cell death whereas Ad-IFN treatment resulted in high levels of both M30 and M65. In contrast, conditioned medium from Ad-IFN treated cells whether from normal human urothelial cells or bladder cancer cells caused mainly increases in M30 levels when added to IFN protein resistant KU7 or UC9 bladder cancer cells, suggesting that the bystander factors present in the CM produced primarily apoptotic cell death. In addition, a significant increase in M65 levels above that observed for M30 was seen when the IFN protein resistant KU7 and UC9 cells were treated with Ad-IFN, again indicating there is additional necrotic related cell death produced by Ad-IFN as well. Normal urothelial cells showed no cytotoxicity nor increases in M30 or M65 following Ad-IFN treatment. Since intravesical Ad-IFN treatment is presently being evaluated for its efficacy in superficial bladder cancer that measurement of M30 and M65 levels in the urine at various time-points before and after Ad-IFN treatment may provide not only a biomarker of efficacy but also evidence for the different types and proportion of cell kill produced by the various mechanisms of cell kill in the tumors of individual patients.

Understanding the role of reactive metabolites in drug-induced hepatotoxicity: state of the science

Drug-induced liver injury (DILI) represents a major impediment to the development of new drugs and is a leading cause of drug withdrawal. The occurrence of hepatotoxicity has been closely associated with the formation of chemically reactive metabolites. Huge investment has focused on the screening of chemically reactive metabolites to offer a pragmatic approach to produce safer drugs and also reduce drug attrition and prevent market place withdrawal. However, questions surrounding the importance of chemically reactive metabolites still remain. Increasing evidence now exists for the multi-factorial nature of DILI, in particular the role played by the host immune system or disease state in the pathogenesis of DILI. This review aims to evaluate the current measures for the prediction and diagnosis of DILI and to highlight investigations being made to understand the multidimensional nature. Some of the steps being made to generate improved physiological systems to identify more sensitive, reflective mechanism-based biomarkers to aid the earlier identification of DILI and develop safer medicines are also discussed.

Clinical evaluation of M30 and M65 ELISA cell death assays as circulating biomarkers in a drug-sensitive tumor, testicular cancer

Circulating full-length and caspase-cleaved cytokeratin 18 (CK18) are considered biomarkers of chemotherapy-induced cell death measured using a combination of the M30 and M65 ELISAs. M30 measures caspase-cleaved CK18 produced during apoptosis and M65 measures the levels of both caspase-cleaved and intact CK18, the latter of which is released from cells undergoing necrosis. Previous studies have highlighted their potential as prognostic, predictive, and pharmacological tools in the treatment of cancer. Disseminated testicular germ cell cancer (TC) is a paradigm for a chemosensitive solid malignancy of epithelial origin and has a cure rate of 80% to 90%. We conducted M30/M65 analyses on 34 patients with TC before and during treatment with bleomycin, etoposide, and cisplatin and showed that prechemotherapy serum levels of M65 and M30 antigens are correlated with established TC tumor markers lactate dehydrogenase, alpha-fetoprotein, and beta-human chorionic gonadotropin, probably reflecting tumor load. Cumulative percentage change of M65 and M30 from baseline to end of study was highest in poor prognosis patients (P < .05). Moreover, area under the curve profiles of M65 and M30 during chemotherapy mirrored dynamic profiles for lactate dehydrogenase, alpha-fetoprotein, and beta-human chorionic gonadotropin. Consequently, M65 and M30 levels appear to reflect chemotherapy-induced changes that correlate with changes in markers routinely used in the clinic for management of patients with TC. This is the first clinical study where M65 and M30 antigen levels correlate with established prognostic markers and provides impetus for their exploration in other epithelial cancers where there is a pressing need for informative circulating biomarkers.

IAP-targeted therapies for cancer

DNA damage, chromosomal abnormalities, oncogene activation, viral infection, substrate detachment and hypoxia can all trigger apoptosis in normal cells. However, cancer cells acquire mutations that allow them to survive these threats that are part and parcel of the transformation process or that may affect the growth and dissemination of the tumor. Eventually, cancer cells accumulate further mutations that make them resistant to apoptosis mediated by standard cytotoxic chemotherapy or radiotherapy. The inhibitor of apoptosis (IAP) family members, defined by the presence of a baculovirus IAP repeat (BIR) protein domain, are key regulators of cytokinesis, apoptosis and signal transduction. Specific IAPs regulate either cell division, caspase activity or survival pathways mediated through binding to their BIR domains, and/or through their ubiquitin-ligase RING domain activity. These protein-protein interactions and post-translational modifications are the subject of intense investigations that shed light on how these proteins contribute to oncogenesis and resistance to therapy. In the past several years, we have seen multiple approaches of IAP antagonism enter the clinic, and the rewards of such strategies are about to reap benefit. Significantly, small molecule pan-IAP antagonists that mimic an endogenous inhibitor of the IAPs, called Smac, have demonstrated an unexpected ability to sensitize cancer cells to tumor necrosis factor-alpha and to promote autocrine or paracrine production of this cytokine by the tumor cell and possibly, other cells too. This review will focus on these and other developmental therapeutics that target the IAPs in cancer.

Preclinical evaluation of M30 and M65 ELISAs as biomarkers of drug induced tumor cell death and antitumor activity

M30 and M65 are ELISAs that detect different circulating forms of cytokeratin 18. Using the aurora kinase inhibitor AZD1152 and the SW620 human colon cancer xenograft, experiments were conducted to qualify preclinically both assays as serologic biomarkers of cell death. Using two different apoptotic markers, the kinetics of cell death induced by AZD1152 was first characterized in vitro in three different cell lines and shown to peak 5 to 7 days after drug addition. Treatment of non-tumor-bearing rats with AZD1152 (25 mg/kg) produced no alterations in circulating baseline values of M30 and M65 antigens. In treated, tumor-bearing animals, M30 detected a 2- to 3-fold (P < 0.05) increase in plasma antigen levels by day 5 compared with controls. This correlated to a 3-fold increase in the number of apoptotic cells detected on day 5 in SW620 xenografts using immunohistochemistry. By contrast, M65 did not detect a drug-induced increase in circulating antigen levels at day 5. However, M65 plasma levels correlated to changes in tumor growth in control animals (r(2) = 0.93; P < 0.01) and also followed the magnitude of the temporal effect of AZD1152 on tumor growth. An intermediate but active dose of AZD1152 (12.5 mg/kg) produced a less significant increase in M30 plasma levels at day 5. It was also confirmed that the plasma profiles of M30 and M65 mirrored closely those measured in whole tumor lysates. We conclude that M30 is a pharmacodynamic biomarker of AZD1152-induced apoptosis in the SW620 xenograft model, whereas M65 is a biomarker of therapeutic response.

IAPs: what's in a name?

Originally described in insect viruses, cellular proteins with Baculoviral IAP repeat (BIR) motifs have been thought to function primarily as inhibitors of apoptosis. The subsequent finding that a subset of IAPs that contain a RING domain have ubiquitin protein ligase (E3) activity implied the presence of other functions. It is now known that IAPs are involved in mitotic chromosome segregation, cellular morphogenesis, copper homeostasis, and intracellular signaling. Here, we review the current understanding of the roles of IAPs in apoptotic and nonapoptotic processes and explore the notion that the latter represents the primary physiologic activities of IAPs.

Optimisation of circulating biomarkers of cell death for routine clinical use

BACKGROUND

M30 and M65 enzyme-linked immunosorbent assays detect circulating cytokeratin 18 fragments released during caspase-dependent or total cell death, respectively, and have potential as biomarkers in epithelial cancers. While these assays have been validated, their robustness for routine clinical use is unknown.

PATIENTS AND METHODS

M30 and M65 were measured in matched serum and plasma samples from 31 lung cancer patients and 18 controls.

RESULTS

Time allowable between sample acquisition and processing is critical for assays in clinical use. A 4-h delay in processing at room temperature increased M30 (P < 0.0001), an effect minimised by incubation on ice. M30 and M65 in serum were resistant to processing variations including delays. Serum and plasma measurements correlated well although M30 but not M65 was lower in serum (P < 0.0005). Less variation between duplicate assays was observed in serum. Prolonged storage (-80 degrees C) led to increased M30 (12%, 6 months; 34%, 1 year). Sample dilution in the supplied assay diluent proved non-linear, whereas dilution in donor serum or porcine plasma restored linearity up to a ratio of 1 : 6.

CONCLUSION

We present recommendations that improve the reliability of these assays for clinical use and recommend serum as the preferred matrix with data more resistant to variations in collection.

Cytokeratin fragments in the serum: their utility for the management of oral cancer

Head and neck squamous cell carcinoma (HNSCC) is the sixth most common malignancy and is a major cause of cancer morbidity and mortality worldwide. Oral cancer is the most predominant malignancy in the Indian subcontinent due to the widespread habits of chewing tobacco and related products. Patients with oral tumours have a high risk of early locoregional relapse. Early detection of disease progression remains a challenging task mainly due to the lack of adequate early prognostic markers. CEA, SCC Ag, CA-125, serum cytokeratin (CK) fragments, Cyfra 21-1 (CK 19), TPS (CK 18), TPA (CK 8, 18, and 19) etc. are being used as serum markers for the prediction of prognosis of various malignancies. This review presents the available literature on serum CK markers in different malignancies evaluates their utility in the management of oral cancer, and identifies the lacunae which need to be addressed to develop sensitive and specific assays for early detection of recurrence, prognosis, and treatment monitoring.

The inhibitor of apoptosis proteins as therapeutic targets in cancer

Apoptosis is a cell suicide process with a major role in development and homeostasis in vertebrates and invertebrates. Inhibition of apoptosis enhances the survival of cancer cells and facilitates their escape from immune surveillance and cytotoxic therapies. Among the principal molecules contributing to this phenomenon are the inhibitor of apoptosis (IAP) proteins, a family of antiapoptotic regulators that block cell death in response to diverse stimuli through interactions with inducers and effectors of apoptosis. IAP proteins are expressed in the majority of human malignancies at elevated levels and play an active role in promoting tumor maintenance through the inhibition of cellular death and participation in signaling pathways associated with malignancies. Here, we discuss the role of IAP proteins in cancer and options for targeting IAP proteins for therapeutic intervention.

Inhibitor of apoptosis protein (IAP) profiling in experimental autoimmune encephalomyelitis (EAE) implicates increased XIAP in T lymphocytes

In multiple sclerosis (MS) and its widely accepted animal model, experimental autoimmune encephalomyelitis (EAE), the failure of autoreactive immune cells to undergo apoptosis is thought to contribute to CNS tissue damage and disease progression. Promoting apoptosis of myelin-reactive immune cells in diseases such as MS, may delay disease progression and decrease the frequency and severity of relapses. X-linked inhibitor of apoptosis (XIAP) is a potent anti-apoptotic protein that inhibits intrinsic, extrinsic, and c-Jun amino-terminal kinase mediated apoptosis and was the only member of the inhibitor of apoptosis (IAP) family upregulated in whole blood from EAE mice. Similar increases in XIAP were also observed in both peripheral and encephalitogenic T lymphocytes. Increased XIAP expression in T cells within areas of demyelination in the CNS suggests that XIAP may be enhancing cell survival and thereby contributing to disease pathology.

Biomarker method validation in anticancer drug development

Over recent years the role of biomarkers in anticancer drug development has expanded across a spectrum of applications ranging from research tool during early discovery to surrogate endpoint in the clinic. However, in Europe when biomarker measurements are performed on samples collected from subjects entered into clinical trials of new investigational agents, laboratories conducting these analyses become subject to the Clinical Trials Regulations. While these regulations are not specific in their requirements of research laboratories, quality assurance and in particular assay validation are essential. This review, therefore, focuses on a discussion of current thinking in biomarker assay validation. Five categories define the majority of biomarker assays from 'absolute quantitation' to 'categorical'. Validation must therefore take account of both the position of the biomarker in the spectrum towards clinical end point and the level of quantitation inherent in the methodology. Biomarker assay validation should be performed ideally in stages on 'a fit for purpose' basis avoiding unnecessarily dogmatic adherence to rigid guidelines but with careful monitoring of progress at the end of each stage. These principles are illustrated with two specific examples: (a) absolute quantitation of protein biomarkers by mass spectrometry and (b) the M30 and M65 ELISA assays as surrogate end points of cell death.

Cytokeratin-18 is a useful serum biomarker for early determination of response of breast carcinomas to chemotherapy

PURPOSE

With a widening arsenal of cancer therapies available, it is important to develop therapy-specific predictive markers and methods to rapidly assess treatment efficacy. We here evaluated the use of cytokeratin-18 (CK18) as a serum biomarker for monitoring chemotherapy-induced cell death in breast cancer.

EXPERIMENTAL DESIGN

Different molecular forms of CK18 (caspase cleaved and total) were assessed by specific ELISA assays. Drug-induced release of CK18 was examined from breast carcinoma cells and tissue. CK18 protein composition was examined in serum. CK18 levels were determined in serum from 61 breast cancer patients during docetaxel or cyclophosphamide/epirubicin/5-fluorouracil (CEF) therapy.

RESULTS

Caspase-cleaved CK18 molecules were released from monolayer cultures and tumor organ cultures to the extracellular compartment. CK18 was present in complexes with other cytokeratins in serum. Such CK18 protein complexes are remarkably stable, leading to favorable performance of CK18 biomarker assays for clinical investigations. Docetaxel induced increased levels of caspase-cleaved CK18 in serum from breast cancer patients, indicating apoptosis. CEF therapy led to increases predominantly in uncleaved CK18, indicating induction of necrotic cell death in many tumors. The increase in total CK18 at 24 h of the first treatment cycle correlated to the clinical response to CEF therapy (P < 0.0001).

CONCLUSIONS

Induction of necrotic cell death may explain the clinical efficacy of anthracycline-based therapy for breast carcinomas with defective apoptosis pathways. We suggest that CK18 biomarkers are useful for early prediction of the response to CEF therapy in breast cancer and may be useful biomarkers for clinical trials.

Dual roles of intermediate filaments in apoptosis

New roles have emerged recently for intermediate filaments (IFs), namely in modulating cell adhesion and growth, and providing resistance to various forms of stress and to apoptosis. In this context, we first summarize findings on the IF association with the cell response to mechanical stress and growth stimulation, in light of growth-related signaling events that are relevant to death-receptor engagement. We then address the molecular mechanisms by which IFs can provide cell resistance to apoptosis initiated by death-receptor stimulation and to necrosis triggered by excessive oxidative stress. In the same way, we examine IF involvement, along with cytolinker participation, in sequential caspase-mediated protein cleavages that are part of the overall cell death execution, particularly those that generate new functional IF protein fragments and uncover neoantigen markers. Finally, we report on the usefulness of these markers as diagnostic tools for disease-related aspects of apoptosis in humans. Clearly, the data accumulated in recent years provide new and significant insights into the multiple functions of IFs, particularly their dual roles in cell response to apoptotic insults.

Livin/melanoma inhibitor of apoptosis protein as a potential therapeutic target for the treatment of malignancy

Livin, also called melanoma inhibitor of apoptosis protein (IAP) or kidney IAP, is a member of the IAP family of caspase inhibitors that selectively binds the endogenous IAP antagonist SMAC and caspase-3, caspase-7, and caspase-9. As such, Livin inhibits apoptosis, and its overexpression renders malignant cells resistant to chemotherapy. Therefore, inhibitors of Livin could be useful adjuncts to chemotherapy in the treatment of malignancies. This review will discuss Livin as a potential therapeutic target and strategies for its inhibition, including antisense oligonucleotides, small-molecule inhibitors, and immune-mediated approaches.

Qualification of M30 and M65 ELISAs as surrogate biomarkers of cell death: long term antigen stability in cancer patient plasma

PURPOSE

M30 and M65 ELISAs are proposed as surrogate biomarkers of tumour cell death in patients and are being applied increasingly in the pharmacodynamic (PD) evaluation of anticancer drugs during clinical trials. In the absence of such data, we have studied the long-term stability of the antigens of both assays in plasma of cancer patients stored at -80 degrees C over 2 years.

RESULTS

No evidence was detected of degradation in the M65 antigen. However, in a proportion of patients significant increases in levels of M30 antigen were detected

CONCLUSION

Plasma samples for M65 analysis can be stored at -80 degrees C for 2 years; however, caution is recommended when considering long-term storage of samples for the M30 assay.