[Show abstract][Hide abstract] ABSTRACT: Non-invasive quantitative imaging biomarkers are essential for the evaluation of novel targeted therapeutics. Before deployment in clinical trials, such imaging biomarkers require qualification, typically through pre-clinical identification of imaging-pathology correlates.
First, in investigating imaging biomarkers of invasion, the response of orthotopic murine PC3 prostate xenografts to the Src inhibitor saracatinib was assessed using susceptibility contrast MRI. Second, the longitudinal response of chemically induced rat mammary adenocarcinomas to the VEGFR2 inhibitor vandetanib was monitored by intrinsic susceptibility MRI, to identify the time window of transient vascular normalisation.
No significant differences in fractional blood volume (%), vessel calibre (μm), native T(1) (ms) or apparent water diffusion coefficient were determined, despite reduced expression of activated Fak and paxillin in the saracatinib cohort. Treatment with vandetanib elicited a 60% antitumour response (P<0.01), 80% inhibition in vessel density (P<0.05) and reduction in hypoxia (P<0.05). There was, however, no significant change in tumour baseline R(2)* (s(-1)) or carbogen-induced ΔR(2)* with treatment.
Reporting negative imaging biomarker responses is important, to avoid the risk of clinical trials using the same biomarkers being undertaken with a false expectation of success, and the abandonment of promising new therapeutics based on a false-negative imaging biomarker response being mistaken for a true-negative.
British Journal of Cancer 05/2012; 106(12):1960-6. · 5.08 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: AZD0530, an orally available Src inhibitor, demonstrated potent antimigratory and anti-invasive effects in vitro, and inhibited metastasis in a murine model of bladder cancer. Antiproliferative activity of AZD0530 in vitro varied between cell lines (IC(50) 0.2 ->10μM). AZD0530 inhibited tumor growth in 4/10 xenograft models tested and dynamically inhibited in vivo phosphorylation of Src substrates paxillin and FAK in both growth-inhibition-resistant and -sensitive xenografts. The activity of AZD0530 in NBT-II bladder cancer cells in vitro was consistent with inhibition of cell migration and stabilization of cell-cell adhesion. These data suggest a dominant anti-invasive pharmacology for AZD0530 that may limit tumor progression in a range of cancers. AZD0530 is currently in Phase II clinical trials.
[Show abstract][Hide abstract] ABSTRACT: Early clinical trials of anticancer agents may be enriched by robust biomarkers of activity. Surrogate measures used in trials of cytotoxic agents, such as tumor size regression, may not be informative when investigating targeted agents that act principally to inhibit invasion or proliferation. This study aimed to determine the validity of invasion-related biomarkers of activity for AZD0530, a potent Src inhibitor currently in clinical development. Focal adhesion kinase (FAK) and paxillin are downstream phosphorylation substrates of Src and mediate tumor cell adhesion and invasiveness. These were therefore selected as biologically relevant markers of Src inhibition. Early breast cancer was chosen as a model as multiple samples can be collected during standard treatment and there is an intervening period in which experimental intervention can be applied. Tumor tissue was collected from diagnostic core biopsies and subsequent surgical tumor excision samples in 29 women with early breast cancer attending a single center. Protein levels were assessed quantitatively by Luminex and qualitatively by immunohistochemistry. AZD0530 inhibited tumor growth in a manner independent of dose and inhibited phosphorylation of FAK and paxillin in a dose-dependent manner in a Calu-6 xenograft model. In the clinical study, agreement of within-visit and also of between-visit measurements was high and the estimated number of patients required to detect a drug effect would be low enough to allow use of these markers as endpoints in future dose selection studies.
Breast Cancer Research and Treatment 05/2008; 114(2):211-21. · 4.47 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Demonstration of pharmacodynamic activity of new, targeted cancer drugs in tumour tissue is potentially important in guiding early drug development. However, delays between tumour sampling and sample fixation may result in variability of pharmacodynamic biomarkers. The aim of this study, was to assess the impact of delays in fixation on biomarkers of Src kinase activity. A total of 20 patients with locally advanced breast cancer and 5 with early bladder cancer had multiple tissue samples taken which were fixed at documented time points up to 60 min after biopsy. These were examined to determine if the amount of Paxillin, phospho-Paxillin, phospho-focal adhesion kinase (FAK) and total phospho-Tyrosine changed over time, using a quantitative lysate immunoassay. In breast cancer, there was an increase in the amount of phospho-Paxillin (60% per h; P = 0.019) up to 60 min after biopsy. The amount of total Paxillin decreased (28% per h; P = 0.034) over the same time course. In early bladder cancer, no changes were noted in any endpoints up to 45 min. Standardisation of the time taken between biopsy and fixation may be critical, particularly in studies using phosphorylated protein biomarkers.
Cancer Chemotherapy and Pharmacology 02/2008; 61(1):23-32. · 2.57 Impact Factor