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

Quantitative assessment of human serum transferrin receptor in breast cancer patients pre- and post-chemotherapy using peptide immunoaffinity enrichment coupled with targeted proteomics

BACKGROUND

sTfR, a soluble form of transferrin receptor in serum, has been suggested as an indicator of bone marrow failure in breast cancer patients receiving chemotherapy. However, intensive chemotherapy could also cause a reduction of sTfR to a level below the LOQ of most assays.

METHODS

An advanced liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based targeted proteomics assay coupled with peptide immunoaffinity enrichment (SISCAPA) was developed and validated for monitoring sTfR.

RESULTS

Tryptic peptide 681VEYHFLSPYVSPK693 was selected as a surrogate analyte for quantification. High-abundant proteins were first removed from serum, followed by SISCAPA that was effective in surrogate peptide enrichment and sensitivity enhancement. The resulting LOQ can achieve 100ng/ml (~10-fold increase). Then, sTfR levels in breast cancer patients pre- and post-chemotherapy, and healthy volunteers were accurately quantified as 1.77±0.53μg/ml, 0.98±0.26μg/ml and 1.66±0.50μg/ml, respectively, using a standard addition method. While there was no evidence for a difference between patients and healthy volunteers, differential levels of sTfR pre- and post-chemotherapy were obtained. Comparison between SISCAPA-targeted proteomics and ELISA indicated that the former approach provided a lower value of sTfR.

CONCLUSIONS

SISCAPA-targeted proteomics may allow the quantification of low-abundant proteins in a more accurate manner.

Can circulating M30 and M65 levels be beneficial markers in the diagnosis and management of patients with complete hydatidiform mole?

OBJECTIVE

The objective of this study is to evaluate the prognostic value of M30 and M65 levels as markers of apoptotic activity and maternal serum oxidative stress in patients with complete hydatidiform mole (CHM).

METHODS

In total, 68 pregnant women were included in the study. The study group included 34 pregnant with CHM, while 34 healthy pregnant were employed as a control group. Venous blood samples were drawn to assess the maternal serum oxidative stress and M30-M65 levels. In addition, a second blood sample was drawn from patients with CHM on day 8 after dilatation evacuation.

RESULTS

Maternal serum oxidative stress and M30-M65 levels were found to be significantly higher in patients with CHM as compared with the control group. It was found that serum β-subunit of human chorionic gonadotropin (β-hCG) level had a significant positive correlation with M30-M65 levels in patients with CHM. In addition, serum M65 level was found to be as effective as β-hCG in the identification of the patients with CHM.

CONCLUSION

Our results indicated that oxidative stress and apoptosis may play significant roles in CHM development. In addition, it seems that serum M30-M65 levels can presumably be an ancillary laboratory test to β-hCG in the diagnosis and follow-up of the patients with CHM.

Optimisation of an immunohistochemistry method for the determination of androgen receptor expression levels in circulating tumour cells

BACKGROUND

AZD3514 inhibits and down regulates the androgen receptor (AR) and has undergone clinical trials in prostate cancer. To provide proof-of-mechanism (POM) in patients, an immunohistochemistry (IHC) method for determination of AR in circulating tumour cells (CTC) was developed and validated.

METHODS

After an assessment of specificity validation focused on intra- and inter-operator reproducibility utilising a novel modification of incurred sample reanalysis (ISR). β-Content γ-confidence tolerance intervals (BCTI) and Cohen's Kappa (κ) were employed in statistical analysis of results.

RESULTS

In a first set of IHC reproducibility experiments, almost perfect agreement was recorded (κ=0.94) when two different operators scored CTC as overall positive or negative for AR. However, BCTI analysis identified a specific bias in scoring staining intensity, where one operator favoured moderate over strong assignments, whereas the reverse was the case with the second operator. After a period of additional training involving deployment of a panel of standardised images, a second set of validation experiments were conducted. These showed correction of the inter-operator bias by BCTI with κ for scoring intensity increasing from 0.59 to 0.81, indicative of almost perfect agreement.

CONCLUSIONS

By application of BCTI to the validation of IHC, operator bias and therefore poor reproducibility can be identified, characterised and corrected to achieve a level of error normally associated with a quantitative biomarker assay, such as an ELISA. The methodological approach described herein can be applied to any generic IHC technique.

Method validation of circulating tumour cell enumeration at low cell counts

Background

Circulating tumour cells (CTC) are receiving increasing attention as prognostic, predictive and pharmacodynamic biomarkers in cancer patients. However, their clinical significance can be dependent on an accurate determination of CTC around cut-off values at low cell counts (<10 cells/7.5 ml). Consequently, we have conducted method validation of the CellSearch™ system focusing on clinical samples containing CTC in the cut-off region.

Methods

Analytical accuracy was first assessed employing quality controls (QC) and spiked healthy volunteer blood specimens. Results were analysed by β-expectation tolerance intervals (BETI). Inter-operator error (6 different readers) was then characterised in 38 different patient samples, 68% of which had ≤5 CTC and data were analysed by β-content γ-confidence tolerance intervals (BCTI).

Results

Results from QCs and spiked blood confirmed a 3-4-fold higher degree of imprecision at the low (48 cells, BETI = + 0.288/-0.345, β = 95%) compared to the high QC (987 cells, BETI = +0.065/-0.140, β = 95%). However, when data for individual analysts were interrogated characteristic systematic errors were detected. In the analysis of patient samples again individual analysts introduced a highly specific error into the interpretation of CTC images, which correlated to the level of training and experience. When readers were selected based on BETI and BCTI results, the high level of between-operator error (up to 170%) observed at CTC of ≤ 5 was reduced to < 30%.

Conclusions

Inter-operator variability in enumeration of CTC at low cell counts can be considerable, but is also potentially avoidable by following simple guidance steps.

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.