The NCCN Task Force on Estrogen Receptor and Progesterone Receptor Testing in Breast Cancer by Immunohistochemistry was convened to critically evaluate the extent to which the presence of the estrogen receptor (ER) and progesterone receptor (PgR) biomarkers in breast cancer serve as prognostic and predictive factors in the adjuvant and metastatic settings, and the ability of immunohistochemical (IHC) detection of ER and PgR to provide an accurate assessment of the expression of these biomarkers in breast cancer tumor tissue. The task force is a multidisciplinary panel of 13 experts in breast cancer who are affiliated with NCCN member institutions and represent the disciplines of pathology, medical oncology, radiation oncology, surgical oncology, and biostatistics. The main overall conclusions of the task force are ER is a strong predictor of response to endocrine therapy; ER status of all samples of invasive breast cancer or ductal carcinoma in situ (DCIS) should be evaluated by IHC; IHC measurements of PgR, although not as important clinically as ER, can provide useful information and should also be performed on all samples of invasive breast cancer or DCIS; IHC is the main testing strategy for evaluating ER and PgR in breast cancer and priority should be given to improve the quality of IHC testing methodologies; all laboratories performing IHC assays of ER and PgR should undertake formal validation studies to show both technical and clinical validation of the assay in use; and all laboratories performing IHC assays of hormone receptors in breast cancer should follow additional quality control and assurance measures as outlined in the upcoming guidelines from the American Society of Clinical Oncology and College of American Pathologists.

The NCCN HER2 Testing in Breast Cancer Task Force was convened to critically evaluate the ability of the level of HER2 expression or gene amplification in breast cancer tumors to serve as a prognostic and a predictive factor in the metastatic and adjuvant settings, to assess the reliability of the methods of measuring HER2 expression or gene amplification in the laboratory, and to make recommendations regarding the interpretation of test results. The Task Force is a multidisciplinary panel of 24 experts in breast cancer representing the disciplines of medical oncology, pathology, radiation oncology, surgical oncology, epidemiology, and patient advocacy. Invited members included members of the NCCN Breast Cancer Panel and other needed experts selected solely by the NCCN. During a 2-day meeting, individual task force members provided didactic presentations critically evaluating important aspects of HER2 biology and epidemiology: HER2 as a prognostic and predictive factor; results from clinical trials in which trastuzumab was used as a targeted therapy against HER2 in the adjuvant and metastatic settings; the available testing methodologies for HER2, including sensitivity, specificity, and ability to provide prognostic and predictive information; and the principles on which HER2 testing should be based. Each task force member was charged with identifying evidence relevant to their specific expertise and presentation. Following the presentations, an evidence-based consensus approach was used to formulate recommendations relating to the pathologic and clinical application of the evidence to breast cancer patient evaluation and care. In areas of controversy, this process extended beyond the meeting to achieve consensus. The Task Force concluded that accurate assignment of the HER2 status of invasive breast cancer is essential to clinical decision making in the treatment of breast cancer in both adjuvant and metastatic settings. Formal validation and concordance testing should be performed and reported by laboratories performing HER2 testing for clinical purposes. If appropriate quality control/ assurance procedures are in place, either immunohistochemistry (IHC) or fluorescence in situ hybridization (FISH) methods may be used. A tumor with an IHC score of 0 or1+, an average HER2 gene/chromosome 17 ratio of less than 1.8, or an average number of HER2 gene copies/cell of 4 or less as determined by FISH is considered to be HER2 negative. A tumor with an IHC score of 3+, an average HER2 gene/chromosome 17 ratio of greater than 2.2 by FISH, or an average number of HER2 gene copies/cell of 6 or greater is considered HER2 positive. A tumor with an IHC score of 2+ should be further tested using FISH, with HER2 status determined by the FISH result. Tumor samples with an average HER2 gene/chromosome ratio of 1.8 to 2.2 or average number of HER2 gene copies/cell in the range of greater than 4 to less than 6 are considered to be borderline, and strategies to assign the HER2 status of such samples are proposed. (JNCCN 2006;4(Suppl 3):S1–S22)

Proton NMR spectroscopy at 500 and 361 MHz has been used to characterize the noncovalent or electrostatic complexes of yeast cytochrome c peroxidase (CcP) with horse, tuna, yeast isozyme-1, and yeast isozyme-2 ferricytochromes c and the covalently cross-linked complexes of cytochrome c peroxidase with horse and yeast isozyme-1 ferricytochromes c. Under the conditions employed in this work, the stoichiometry of the predominant complex formed in solution (which totaled greater than 90% of complex formed) was found to be 1:1 in all cases. These studies have elucidated significant differences in the proton NMR absorption spectra and the one-dimensional nuclear Overhauser effect difference spectra of the complexes, depending on the specific species of ferricytochrome c incorporated. In particular, the results indicate that the noncovalent complexes formed between CcP and physiological redox partners (yeast isozyme-1 or yeast isozyme-2 ferricytochromes c) are distinctly different from the noncovalent complexes formed between CcP and ferricytochromes c from horse and tuna. Parallel chemical cross-linking studies carried out using mixtures of cytochrome c peroxidase with horse ferricytochrome c, and cytochrome c peroxidase with yeast isozyme-1 ferricytochrome c further emphasize such cytochrome c-dependent differences, with only the covalently cross-linked complex of physiological redox partners (cytochrome c peroxidase/yeast isozyme-1) displaying NMR spectra characteristic of a heterogeneous mixture of different 1:1 complexes. Finally, one-dimensional nuclear Overhauser effect experiments have proven valuable in selectively and efficiently probing the protein-protein interface in these complexes, including the environment around the cytochrome c heme 3-methyl group and Phe-82.

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The kinetics of reduction of free flavin semiquinones of the individual components of 1:1 covalent and electrostatic complexes of yeast ferric and ferryl cytochrome c peroxidase and ferric horse cytochrome c have been studied. Covalent cross-linking between the peroxidase and cytochrome c at low ionic strength results in a complex that has kinetic properties both similar to and different from those of the electrostatic complex. Whereas the cytochrome c heme exposure to exogenous reductants is similar in both complexes, the apparent electrostatic environment near the cytochrome c heme edge is markedly different. In the electrostatic complex, a net positive charge is present, whereas in the covalent complex, an essentially neutral electrostatic charge is found. Intracomplex electron transfer within the two complexes is also different. For the covalent complex, electron transfer from ferrous cytochrome c to the ferryl peroxidase has a rate constant of 1560 s-1, which is invariant with respect to changes in the ionic strength. The rate constant for intracomplex electron transfer within the electrostatic complex is highly ionic strength dependent. At mu = 8 mM a value of 750 s-1 has been obtained [Hazzard, J. T., Poulos, T. L., & Tollin, G. (1987) Biochemistry 26, 2836-2848], whereas at mu = 30 mM the value is 3300 s-1. This ionic strength dependency for the electrostatic complex has been interpreted in terms of the rearrangement of the two proteins comprising the complex to a more favorable orientation for electron transfer. In the case of the covalent complex, such reorientation is apparently impeded.(ABSTRACT TRUNCATED AT 250 WORDS)