Abstract P3-05-09: Interlaboratory variability of Ki67 labeling index in breast cancer tissue microarrays

Objective: Assessment of tumor proliferation using the Ki67 labeling index (Ki67-LI) is increasingly recommended for prognostication and adjuvant chemotherapy decisions in breast cancer. Our aim was to investigate interlaboratory variance of Ki67-LI results using TMA and centralised assessment to exclude preanalytic influences and postanalytic variance, respectively.

Methods: Nine pathology laboratories (8 German and 1 Dutch) performed Ki67 staining of a TMA slide according to their routine in house protocol (including internal and external quality assurance). 40 samples per lab were centrally analyzed. The Ki67-LI was calculated after counting first all tumor cells and subsequently all Ki67 positive tumor cells of each sample regardless of staining intensity. For each tissue sample we evaluated the range of Ki67-LIs between different labs. Further 20 labs of the German Breast Screening Pathology Initiative will participate in 2013.

Results: The range of Ki67-LIs between the labs was: 1-5% in 4 (10%), 6-10% in 6 (15%), 11-15% in 7 (17,5%), 16-20% in 2 (5%), 21-25% in 7 (17%), 26-30% in 4 (10%), 31-35% in 1 (1%), 36-40% in 4 (10%), 41-45% in 2 (5%), 46-50 in 0 (0%) and >50% in 3 samples (7%), respectively. Thus, in 35% of results of the 9 labs (26 of the 40 TMA specimens) the Ki67-LI differed by more than 25%. The analysis of variance (ANOVA) came out with F = 4.24 which is much larger than the critical F value of 1.97 for these study results (p = 7.74902E-05). This means that the observed interlaboratory variance of 4.24 is systematic and not due to sampling error. The respective standard deviation is 33.4%.

Conclusion: In a setting strictly standardised in terms of preanalytic influences by using TMA and postanalytic variance by centralised quantification, Ki67-LI seems to be heavily influenced by laboratory-specific analytic variables. Taking this into consideration, there may be a risk of prognostic or predictive misclassification in some breast cancer patients in daily practice.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P3-05-09.

Abstract P6-01-08: Keratin 5/14+ Progenitor Cell Concept of Breast Epithelium: Revisited

Background: The role of keratin (K) 5/14+ progenitor cells as precursor cells of the breast epithelium has been demonstrated both in culture and in situ. This cell model opens a new field in which distinct cell subtypes can be evaluated in terms of their functional state and describes how these cells may give rise to either benign or malignant tumors. Material and Methods: In this study, we used modern triple immunofluorescent labeling experiments to visualize directly different cell types and their functional status applying, as a reference, antibodies to basal (K5/14) and glandular (K8/18) keratins and a myoepithelial marker in combination with antibodies to ER-alpha, Ki67, BCL2 and c-kit in normal resting breast epithelium and in 30 cases of ductal neoplasia of low grade pathway and 8 cases of epithelial hyperplasia. Different cell types were quantitatively assayed. Immunolabeling results were supported with quantitative real time PCR.

Results: Basal and glandular keratins in the normal luminal breast epithelium were found to be expressed in highly specific sequential pattern from K5/14+progenitor cells to K8/18+ glandular cells. ER alpha, Ki67, c-kit and BCL2 were found differentially expressed in various subtypes of the breast epithelium, ER-alpha was expressed only in a subset of glandular cells thus subdividing the glandular lineage into ER-alphapositive and negative subcategories. The highest Ki67-proliferation was found in phenotypically glandular cells which are ER-alpha negative. BCL2 was characteristically co-expressed in glandular cells, whereas c-kit was detected mainly in earlier glandular cells. Benign epithelial hyperplasia showed a striking similarity to normal luminal breast epithelium. In terms of functional differentiation these cells disclosed the same ER-alpha, BCL2 and c-kit expression as that observed in normal epithelium. In contrast to UDH, all types of low-grade in-situ neoplasia of ductal type are characterized by expression of only glandular keratins 8/18. The tumour cells co-expressed ER-alpha, BCL2 and Ki67. On the other hand, c-Kit was not expressed in these lesions.

Discussion: From our data, it is evident that basal (K5/14) and glandular keratins (K8/18) are expressed in highly specific hierarchical patterns related to stage of glandular differentiation. This phenotypic hierarchy of cells is furthermore bound to a differential expression of ER, Ki67, c-kit and BCL2 in a very specific manner. Usual ductal hyperplasia disclosed a striking similarity to the resting glandular epithelium. In contrast, all types of low grade intraepithelial neoplasia not only retain the keratin patterns of their (normal) glandular counterpart but show the same functional differentiation with a positive expression of ER and BcL2 and lack of c-kit. This similarity indicates that these lesions may derive from more differentiated glandular cells of the lobular breast epithelium. The data presented here confirm that the K5/14+ progenitor cell concept provides important insight into the functional nature of normal breast epithelium and in proliferative diseases.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P6-01-08.

[Diagnostics of microcalcifications from minimally invasive biopsies in mammography screening: results from the prevalence phase]

BACKGROUND

In mammography screening programmes carried out according to European guidelines, minimally invasive biopsies (MIB) are performed on up to 3% of participants. The aim of this study was to analyse the spectrum of histopathological findings including B categories in MIBs with microcalcifications compared to MIBs without microcalcifications.

MATERIAL AND METHODS

Prospectively collected histological findings of MIBs taken during the period July 2006 to June 2007 were analysed using the Breast Screening Pathology Database of the Reference Centre in Münster.

RESULTS

Of the 4,326 MIBs investigated, 2,161 were benign (B1-B3) whereas 2,165 were malignant (B4-B5) resulting in an overall malignancy rate of 50.04%. Of the MIBs 1,809 contained microcalcifications and 2,517 did not. Cases with microcalcifications showed a different distribution of B categories: B2 was found in 44.5% versus 24.2%, B3 in 18.2% versus 5.5% and the malignancy rate of cases with microcalcifications was 36.8% versus 59.5%. Of all cases of ductal carcinoma in situ (DCIS) detected in the screening programme, 83.35% were diagnosed in MIBs containing microcalcifications.

CONCLUSIONS

MIBs containing microcalcifications showed a different spectrum of diagnoses, especially higher rates of B3 lesions. Even though MIBs without microcalcifications showed a higher overall malignancy rate, most cases of DCIS were diagnosed in MIB containing microcalcifications.

[Mapping of a deletion interval on 8p21-22 in prostate cancer by gene dosage PCR]

Various microsatellite and CGH studies in prostate cancer identify deletions on the short arm of chromosome 8 especially at band 8p21-22 searching for unknown putative tumor suppressor genes. By means of microsatellite markers several candidate genes were detected which may play different roles in early prostate cancer progression. We established a quantitative gene dosage PCR based on the real time PCR method serving the purpose of genomic fine mapping. Therefore we used 10 Assays-on Demand (ABI) for the detection of deletions located between and nearby the microsatellite markers D8S258 and NEFL spanning a genomic region of approximate 7 mbp. Comparative immunohistochemical analysis from tissue micro arrays (TMA) of 1122 independent cases followed. We were able to detect three clearly separated deletion intervals on 8p21-22. One on LZTS1, second on NEFL and third a deletion hot spot on LOXL2, which was affected in 72% of all investigated cases. Our comparative immunohistochemical TMA based studies demonstrate that LOXL2 is nearly lost in most prostate cancer tissues. LOXL2 catalyze the crosslinking of collagen and elastin in the extracellular matrix and it has been assumed that it is involved in tumor suppression and cell adhesion. LOXL2 is frequently expressed in proliferating tissues and shows a high expression in benign prostate tissue too. In prostate cancer the expression is positive correlated with the MIB1-score.

Whole genome expression analysis for biologic rational pathway modeling: application in cancer prognosis and therapy prediction

Using semi-quantitative microarray technology, almost every one of the approximately 30 000 human genes can be analyzed simultaneously with a low rate of false-positives, a high specificity, and a high quantification accuracy. This is supported by data from comparative studies of microarrays and reverse-transcription PCR for established cancer genes including those for epidermal growth factor receptor (EGFR), human epidermal growth factor receptor-2 (HER2/ERBB2), estrogen receptor (ESR1), progesterone receptor (PGR), urokinase-type plasminogen activator (PLAU), and plasminogen activator inhibitor-1 (SERPINE1). As such, semi-quantitative expression data provide an almost completely comprehensive background of biological knowledge that can be applied to cancer diagnostics. In clinical terms, expression profiling may be able to provide significant information regarding (i) the identification of high-risk patients requiring aggressive chemotherapy; (ii) the pathway control of therapy predictive parameters (e.g. ESR1 and HER2); (iii) the discovery of targets for biologically rational therapeutics (e.g. capecitabine and trastuzumab); (iv) additional support for decisions about switching therapy; (v) target discovery; and (vi) the prediction of the course of new therapies in clinical trials. In conclusion, whole genome expression analysis might be able to determine important genes related to cancer progression and adjuvant chemotherapy resistance, especially in the context of new approaches involving primary systemic chemotherapy. In this review, we will survey the current progress in whole genome expression analyses for cancer prognosis and prediction. Special emphasis is given to the approach of combining biostatistical analysis of expression data with knowledge of biochemical and genetic pathways.

[Bootstrapping algorithm approach reveals inherent regulatory pattern in 550 invasive breast cancer cases: CK5/6/CK14 and CK8/18/CK19 builds an antagonistic set]

All the preliminary observations on a lot of marker sets defining different stages in the tumor development are building a framework of work hypothesis which can be verified in characterising large pools of histological uniform rated paraffin probes. We developed a bootstrapping algorithm based on correlation measures to uncover regulatory patterns of immunohistochemical characterized tissue arrays with 550 invasive breast cancer cases. The algorithm is implemented in 'S' a computer language used to model mathematical solutions. Focussing on the Cytokeratins versus a set of prominent markers in breast cancer differentiation it will be obvious that markers which are known to appear in early (progenitor) forms conform to CK5/6 and CK14 while others associated with late stages conform to CK8/18 and CK19. Markers examined are among others EGFR, EMA, erb-B2, Vimentin, p53, ER and PR. The developed approach is an elegant and complete procedure to reveal the real regulatory patterns which are enclosed in a certain experimental design. The statistical significance of the results calculated by our algorithm is generally high and in the presented experimental design smaller than 0.6 * 10E-6.

Deciphering a subgroup of breast carcinomas with putative progression of grade during carcinogenesis revealed by comparative genomic hybridisation (CGH) and immunohistochemistry

Distinct parallel cytogenetic pathways in breast carcinogenesis could be identified in recent years. Nevertheless, it remained unclear as to which tumours may have progressed in grade or which patterns of cytogenetic alteration may define the switch from an in situ towards an invasive lesion. In order to gain more detailed insights into cytogenetic mechanisms of the pathogenesis of breast cancer, the chromosomal imbalances of 206 invasive breast cancer cases were characterised by means of comparative genomic hybridisation (CGH). CGH data were subjected to hierarchical cluster analysis and the results were further compared with immunohistochemical findings on tissue arrays from the same breast cancer cases. The combined analysis of immunohistochemical and cytogenetic data provided evidence that carcinomas with gains of 7p, and to a lesser extent losses of 9q and gains of 5p, are a distinct subgroup within the spectrum of ductal invasive grade 3 breast carcinomas. These aberrations were associated with a high degree of cytogenetic instability (16.6 alterations per case on average), 16q-losses in over 70% of these cases, strong oestrogen receptor expression and absence of strong expression of p53, c-erbB2 and Ck 5. These characteristics provide strong support for the hypothesis that these tumours may develop through stages of well- and perhaps intermediately differentiated breast cancers. Our results therefore underline the existence of several parallel and also stepwise progression pathways towards breast cancer.

Molecular cytogenetic investigations of synchronous bilateral breast cancer

BACKGROUND

Bilaterality in breast cancer is a rare event and together with an early onset of disease points towards inheritance of the disease. However, most cases seem to occur sporadically, either in a synchronous or metachronous manner.

METHODS

Thirty two invasive carcinomas and one in situ carcinoma from 16 patients with synchronous, bilateral breast cancer were investigated by means of comparative genomic hybridisation (CGH) and polymerase chain reaction based multiplex microsatellite analysis. The results were analysed conventionally and were also subjected to a biomathematical cluster analysis.

RESULTS

On average, bilateral breast cancer cases showed a low number of genetic alterations, a low frequency of genetic amplifications, and a high rate of chromosomal 16q losses. A distinct, characteristic genetic alteration associated with bilateral breast disease could not be found. Although two tumour pairs appeared to be related using biomathematical processing for microsatellite analysis, this result was reproduced by CGH data processing in one patient only.

CONCLUSIONS

Most synchronous, bilateral breast cancer cases seem to represent independent tumours rather than metastatic events. Nevertheless, the possibility of a specific susceptibility remains.

Demystified...tissue microarray technology

Several "high throughput methods" have been introduced into research and routine laboratories during the past decade. Providing a new approach to the analysis of genomic alterations and RNA or protein expression patterns, these new techniques generate a plethora of new data in a relatively short time, and promise to deliver clues to the diagnosis and treatment of human cancer. Along with these revolutionary developments, new tools for the interpretation of these large sets of data became necessary and are now widely available. Tissue microarray (TMA) technology is one of these new tools. It is based on the idea of applying miniaturisation and a high throughput approach to the analysis of intact tissues. The potential and the scientific value of TMAs in modern research have been demonstrated in a logarithmically increasing number of studies. The spectrum for additional applications is widening rapidly, and comprises quality control in histotechnology, longterm tissue banking, and the continuing education of pathologists. This review covers the basic technical aspects of TMA production and discusses the current and potential future applications of TMA technology.

Telepathology network: conceptual groundwork and evaluation

Telepathology uses telecommunication technology to transmit microscopic images for diagnostic or teaching purposes. Basic requirements for a telepathology system are described. Usage scenarios for a telepathology network are presented including applications in intraoperative frozen section diagnosis, scientific collaboration and computer based training. Results of an evaluation of 4 currently available telepathology systems are presented.

Generation of type VIII collagen-specific antibodies

We generated a specific polyclonal antibody against the alpha 1 chain of type VIII collagen. The antibody detects type VIII collagen and is definitely free of crossreactivities with the closely related type X collagen. The antibody was generated against a dodecamer peptide chosen to satisfy the following requirements: (a) maximal homology between collagen type VIII molecules from different species; (b) maximal antigenicity as predicted by algorithms from Emini et al. (J. Virol. (1985) 55, 836). Hoop and Woods (Proc. Natl. Acad. Sci. USA (1981) 78, 3824), and Karplus and Schulz (Naturwissenschaften (1985) 72, 212); and (c) maximal specificity, i.e. absence of this sequence in all other proteins known so far. All three requirements were satisfied for a sequence fragment of 12 amino acids (100-111) in the alpha 1(VIII) NC2 domain. This peptide was produced synthetically. Polyclonal antibodies were raised in rabbits and affinity purified on a peptide column. The antibody was tested in a quantitative EIA, immunoblots and in immunocytochemistry and found to be well-suited for all three types of application. The antibody did not crossreact with type X collagen and other extracellular matrix molecules in the EIA. In immunoblots of affinity-purified extracts of the Descemet membrane, a major source of type VIII collagen, the antibody detected several known forms of type VIII collagen. In immunocytochemistry the antibody stained endothelial and astrocytoma cells in monolayer cultures, and cells and extracellular matrix in cryosections of the human Ewing sarcoma, arterial vessels and chicken embryonic heart, whereas the chicken tibiotarsus remained negative. This distribution of immunoreactivity corresponds to the distribution of type VIII but not that of type X collagen. In conclusion this antibody may serve as a highly specific and sensitive tool for investigating the appearance and regulation of type VIII collagen.

The primary structure of a triple-helical domain of collagen type VIII from bovine Descemet's membrane

We have isolated and sequenced a fragment of 469 amino acid residues from bovine type VIII collagen. The sequence was composed of a series of Gly-X-Y repeats which was interrupted 8 times by short imperfections. The number and relative location of these interruptions were similar to those of chicken alpha 1(X) and rabbit alpha 1(VIII) chain triple-helical domains. Comparison to published N-terminal sequences to two triple-helical fragments of bovine type VIII collagen and to the cDNA derived sequence of the rabbit alpha 1(VIII) chain showed that this fragment was the triple-helical domain of a second type VIII collagen chain which we designate alpha 2(VIII).

Characteristics and in vivo occurrence of type VIII collagen

Type VIII collagen was isolated from bovine Descemet's membranes by pepsin treatment and salt fractionation, as described by Kapoor et al. [(1986) Biochemistry 25, 3930-3937]. Contaminating type IV collagen was removed by ion-exchange chromatography. Purified type VIII collagen consisted of two different polypeptide chains and, compared to the fiber forming collagens, showed a higher thermal stability. Corresponding fractions isolated from pepsinized human Ewing's sarcoma and fetal calf aorta reacted immunologically with a protein of similar molecular mass. After extraction of Descemet's membranes with guanidine hydrochloride, a peptide of about 60 kDa was obtained. This seems to be the tissue form of type VIII collagen.