In:
Molecular Cancer Therapeutics, American Association for Cancer Research (AACR), Vol. 8, No. 12_Supplement ( 2009-12-10), p. A41-A41
Abstract:
Introduction: Pharmacodynamic (PD) measurements in patient tissues following administration of cancer drugs may be used to determine a drug's activity and calculate dosing schedules. Biomarker selection for these tests must evaluate the most pertinent proteins in the pathway, but must also take into account biomarker stability in the tissue being tested. Constitutive expression of the PI3K pathway occurs with a high frequency in a variety of human malignancies. We sought to determine whether improper handling of tumor tissue can lead to inaccurate analysis of PI3K-AKT pathway activation when using immunohistochemistry (IHC). Methods: 23 human cancer xenograft tumors were grown in nude mice (n=3/line) and allowed to stay at room temperature for fixed lengths of time to simulate handling of human specimens following surgery. Uniform sized tissue fragments (600–1000 mg) were kept in PBS for 0, 15, 30 and 120 minutes following resection prior to fixation in formalin and paraffin embedding. Four of these tumor lines were also frozen and analyzed by Western blot. IHC was preformed utilizing two pAKT antibodies and one pP70S6K (pS6) antibody. Following IHC, staining intensity was quantified using the Aperio image analysis system. Results: Significant decrease in signal (p & lt;.05) was seen as soon as fifteen minutes of ischemia with both pS6 and pAKT antibodies by IHC in some samples. In nearly all of the samples that had detectable levels of pAKT or pS6 at time zero, this was gone by 120 minutes. There was also considerable discordance between pS6 and pAKT staining in the control samples bringing into question pS6 as a relevant pAKT surrogate biomarker. Conclusion: Significant care should be taken in the interpretation of phospho-specific antibodies since results are strongly dependent on the time of ischemia. Broader analysis of pre-analytic biomarkers not dependent on tissue ischemia may be utilized as surrogate for pathway activation. Citation Information: Mol Cancer Ther 2009;8(12 Suppl):A41.
Type of Medium:
Online Resource
ISSN:
1535-7163
,
1538-8514
DOI:
10.1158/1535-7163.TARG-09-A41
Language:
English
Publisher:
American Association for Cancer Research (AACR)
Publication Date:
2009
detail.hit.zdb_id:
2062135-8
SSG:
12
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