Breast cancer heterogeneity: evaluation of clonality in primary and metastatic lesions

c-erbB-2 and c-Met expression relates to cholangiocarcinogenesis and progression of intrahepatic cholangiocarcinoma

AIMS

The c-erbB-2 and c-Met proto-oncogenes are important for tumour invasiveness and metastasis in many types of malignant tumours. Previous studies have indicated that these proteins are associated with carcinogenesis in intrahepatic cholangiocarcinoma. In this study, we examined c-erbB-2 and c-Met expression by immunohistochemistry in hepatolithiasis, intrahepatic cholangiocarcinoma and metastatic lymph node, in order to clarify whether these proteins play a role in carcinogenesis and tumour metastasis in intrahepatic cholangiocarcinoma.

METHODS AND RESULTS

In hepatolithiasis, the staining for c-erbB-2 was positive in 14 of the 23 (61%) cases, while staining for c-Met was positive in eight of the 23 (35%) cases. In intrahepatic cholangiocarcinoma, staining for c-erbB-2 was positive in 45 of the 81 (55%) cases, while staining for c-Met was positive in 28 (35%) cases. The positivity of c-Met staining in intrahepatic cholangiocarcinoma was significantly higher in the differentiated type of cholangiocarcinoma than in the undifferentiated type. In addition, c-Met-positive staining had an inverted correlation with tumour size, the presence of perineural invasion and the presence of lymph node metastasis. c-Met staining had a significantly higher positivity in cases at an early stage of intrahepatic cholangiocarcinoma. In contrast, the positivity of c-erbB-2 staining in intrahepatic cholangiocarcinoma was significantly higher in cases with lymph node metastasis than in cases without. In metastatic lymph nodes, the staining for c-erbB-2 was positive in 20 of the 25 (80%) cases, while staining for c-Met was positive in six of the 25 (24%) cases. There was no difference in survival between c-erbB-2-positive and negative patients. However, the patients with c-Met-positive tumours had a significantly longer survival than those with c-Met-negative tumours in the medium survival term. The multivariate analysis showed the presence of lymph node metastasis, lymphatic permeation and histological differentiation to be independent prognostic factors.

CONCLUSION

These results indicate that increased c-Met expression participates in cholangiocarcinogenesis and in the early developmental stages of intrahepatic cholangiocarcinoma, while increased c-erbB-2 expression contributes to the development of cholangiocarcinogenesis into an advanced stage associated with tumour metastasis.

Amplification of Her-2/neu gene in Her-2/neu-overexpressing and -nonexpressing breast carcinomas and their synchronous benign, premalignant, and metastatic lesions detected by FISH in archival material

Amplification of Her-2/neu in breast carcinoma is associated with poor prognosis, short disease-free interval, and short survival time in both node-negative and -positive patients. Little is known about the starting point of amplification of Her-2/neu and how it progresses from benign to malignant breast lesions. We attempted to address these questions by evaluating amplification of Her-2/neu in benign, premalignant, and malignant lesions using fluorescence in situ hybridization (FISH). Twenty-six patients with Her-2/neu-overexpressing invasive ductal carcinomas (as judged by strong immunoreactivity with Her-2/neu antibody) and coexisting lesions of ductal hyperplasia (DH), atypical ductal hyperplasia (ADH), ductal carcinoma in situ (DCIS) in the vicinity of the invasive tumor (as judged by review of the hematoxylin and eosin-stained sections), as well as metastatic carcinoma in axillary lymph nodes (mets) were selected for this study. In the primary carcinomas, a close relationship was present between overexpression as detected by immunohistochemistry (IHC) and amplification as demonstrated by FISH (85% concordance). Among these patients, amplification of Her-2/neu in ADH was demonstrated in 7 of 13 cases with ADH, and in DCIS, in 21 of 22 cases with DCIS. There was no amplification in DH or normal ductal epithelium. Significantly, in all 12 patients with synchronous positive axillary lymph nodes, there was concordant amplification of Her-2/neu in the primary and metastatic carcinoma. Amplification was consistent in multifocal metastases, despite morphological heterogeneity in some patients. Amplification ratios increased from ADH to DCIS to invasive carcinoma (P <.01, ADH versus DCIS; P <.05, DCIS versus invasive cancer), but there was no difference in amplification ratios between primary cancers and synchronous axillary metastases (P >.05). We also evaluated Her-2/neu amplification in 21 patients without Her-2/neu overexpression in their primary carcinomas (as judged by absent immunoreactivity with Her-2/neu antibody). Three showed amplification in both primary and metastatic lesions, with a low amplification ratio (approximately 2). One patient had amplification in the primary tumor but not in an axillary metastasis. Two patients exhibited slight amplification in the metastatic carcinoma (ratios 1.6 and 2), but not in their primary cancers. This FISH study indicates that amplification of Her-2/neu can emerge de novo in any stage of the disease process, from ADH to metastatic lesions, but most often appears first in ADH or DCIS. The degree of Her-2/neu amplification increases with progression to invasive carcinoma, there being no further increase in synchronous metastasis. Our data suggest that amplification of Her-2/neu appears to be mainly involved in initiation of breast oncogenesis and that its role in progression of breast cancers is uncertain.

Cytogenetic clues to breast carcinogenesis

The somatic mutation theory of cancer maintains that tumorigenesis is driven by genetic alterations, many of which are visible cytogenetically. We have examined breast cancer by chromosome banding analysis after short-term culturing of tumor cells and here review our findings in 322 karyotypically abnormal samples obtained since 1992 from 256 patients. The screening capabilities of this technique enabled us to identify several cytogenetic subgroups of breast cancer, to study the intratumor heterogeneity of breast carcinomas, and to compare primary tumors with their metastases. Using chromosome abnormalities as clonality markers, we could determine on an individual basis when multiple, ipsilateral or bilateral breast, tumors were independent de novo carcinomas and when they resulted from the spreading of a single malignant clone within one breast or from one breast to the other. The distribution of chromosomal breakpoints and genomic gains and losses is clearly nonrandom in breast cancer, something that can guide further investigations using molecular methods. Based on the total dataset, we propose a multipathway model of mammary carcinogenesis that takes into consideration the genetic heterogeneity revealed by the karyotypic findings and review the karyotypic-pathologic correlations and the possible clinical applications of the cytogenetic knowledge.

Tissue microarrays for rapid linking of molecular changes to clinical endpoints

Advances in genomics and proteomics are dramatically increasing the need to evaluate large numbers of molecular targets for their diagnostic, predictive or prognostic value in clinical oncology. Conventional molecular pathology techniques are often tedious, time-consuming, and require a lot of tissue, thereby limiting both the number of tissues and the number of targets that can be evaluated. Here, we demonstrate the power of our recently described tissue microarray (TMA) technology in analyzing prognostic markers in a series of 553 breast carcinomas. Four independent TMAs were constructed by acquiring 0.6 mm biopsies from one central and from three peripheral regions of each of the formalin-fixed paraffin embedded tumors. Immunostaining of TMA sections and conventional "large" sections were performed for two well- established prognostic markers, estrogen receptor (ER) and progesterone receptor (PR), as well as for p53, another frequently examined protein for which the data on prognostic utility in breast cancer are less unequivocal. Compared with conventional large section analysis, a single sample from each tumor identified about 95% of the information for ER, 75 to 81% for PR, and 70 to 74% for p53. However, all 12 TMA analyses (three antibodies on four different arrays) yielded as significant or more significant associations with tumor-specific survival than large section analyses (p < 0.0015 for each of the 12 comparisons). A single sample from each tumor was sufficient to identify associations between molecular alterations and clinical outcome. It is concluded that, contrary to expectations, tissue heterogeneity did not negatively influence the predictive power of the TMA results. TMA technology will be of substantial value in rapidly translating genomic and proteomics information to clinical applications.

Molecular markers of metastasis in squamous carcinomas

The prognosis for patients with squamous carcinomas of the head and neck region is strongly influenced by the presence or absence of cervical lymph node metastases. Biological markers that indicated a high risk of metastasis would have a major role in determining the optimal therapeutic strategy for these patients. This editorial discusses recent studies of molecular and genetic markers of squamous carcinomas in relation to metastatic potential and highlights some of the issues that limit current progress in this field of study.

Allelotype analysis of flow-sorted breast cancer cells demonstrates genetically related diploid and aneuploid subpopulations in primary tumors and lymph node metastases

Flow cytometric DNA content measurements have demonstrated extensive DNA ploidy heterogeneity in primary breast carcinomas. However, little is known at the molecular level about the clonal relationship between these tumor cell subpopulations, or about the molecular genetic changes associated with aneuploidization. We have used flow cytometric cell sorting to dissect some of this complexity by isolating clonal subpopulations in breast carcinomas for comparative molecular genetic analysis. Clonal subpopulations were isolated from 12 primary breast carcinomas and 5 lymph node metastases from 4 cases based on DNA content and cytokeratin 8/18 labeling. DNA from these clones was screened for allelic imbalances with 92 polymorphic microsatellite markers mapped to 39 different chromosome arms. Diploid and aneuploid populations were concurrently present in 11 out of 12 primary tumors. The DNA ploidy status of primary tumors was identical to that of the related lymph node metastases. Allelic imbalance was present in 10 out of 11 diploid clones (mean, 3.4 +/- 4.2). All allelic imbalances observed in the diploid clones recurred in the cognate aneuploid clones, but were, in the latter, accompanied by additional allelic imbalances at other loci and/or chromosome arms (mean, 10.9 +/- 5.8). In only two of the four metastatic cases did the allelotypes of metastatic clones show small differences relative to their cognate primary tumors. The primary diploid tumor clone recurred in all lymph node metastases. This study indicates that the majority of allelic imbalances in breast carcinomas are established during generation of DNA ploidy diversity. Recurrence of the allelic imbalances in diploid clones in the aneuploid clones suggests linear tumor progression, whereas the simultaneous presence of early diploid and advanced aneuploid clones in both primary and metastatic tumor sites suggests that acquisition of metastatic propensity can be an early event in the genetic progression of breast cancer.

The clonal origin and clonal evolution of epithelial tumours

While the origin of tumours, whether from one cell or many, has been a source of fascination for experimental oncologists for some time, in recent years there has been a veritable explosion of information about the clonal architecture of tumours and their antecedents, stimulated, in the main, by the ready accessibility of new molecular techniques. While most of these new results have apparently confirmed the monoclonal origin of human epithelial (and other) tumours, there are a significant number of studies in which this conclusion just cannot be made. Moreover, analysis of many articles show that the potential impact of such considerations as patch size and clonal evolution on determinations of clonality have largely been ignored, with the result that a number of these studies are confounded. However, the clonal architecture of preneoplastic lesions provide some interesting insights --many lesions which might have been hitherto regarded as hyperplasias are apparently clonal in derivation. If this is indeed true, it calls into some question our hopeful corollary that a monoclonal origin presages a neoplastic habitus. Finally, it is clear, for many reasons, that methods of analysis which involve the disaggregation of tissues, albeit microdissected, are far from ideal and we should be putting more effort into techniques where the clonal architecture of normal tissues, preneoplastic and preinvasive lesions and their derivative tumours can be directly visualized in situ.

Malignant cell detection by fluorescence in situ hybridization (FISH) in effusions from patients with carcinoma

Cytological diagnosis of malignant cells in effusions is hampered by difficulties in the differentiation from reactive mesothelial cells. Because interphase cytogenetics by fluorescence in situ hybridization (FISH) might complement cytological evaluation, we determined the power of tumor cell detection using FISH and cytology in 201 effusions from patients with advanced cancer. Furthermore, 9 primary breast tumors were FISH-karyotyped, and chromosomal aberrations were compared with those of corresponding metastatic effusion cells. By using centromeric probes representing chromosomes 7, 8, 11, 12, 17, and 18, a rate of malignancy-associated aneusomy combined for the 6 chromosomes was detected in an overall of 44.8% of effusion specimens (range, 31.8% to 39.3% for the individual chromosome), comparable to cytology (43.3%). The combination of just 2 FISH probes (namely, representing chromosome pairs 8/11 and 8/17) was almost equally efficient in the identification of aneusomy. Approximately one fourth of the cytologically negative effusions were FISH positive and vice versa. From the initially FISH-negative effusions, 18.9% could be subsequently classified positive with dual-color FISH by visualization of intranuclear chromosomal complexity in rare aneuploid cells. Thus, "overall FISH analysis," including dual-color evaluation, identified tumor cells in significantly more effusions (55.2%, P = .001) than conventional cytology, implying greater sensitivity. Finally, our finding that numerical aberration patterns in primary breast tumors and corresponding metastatic effusions are comparable indicates that FISH examination of primary tumors will indicate the centromeric probe(s) best suited for an efficient search for metastasis in the individual case.

Selection, establishment and characterization of cell lines derived from a chemically-induced rat mammary heterogeneous tumor, by flow cytometry, transmission electron microscopy, and immunohistochemistry

In order to isolate, characterize, and establish culture cell lines with different diagnostic and prognostic significance, derived from multiclonal neoplasms, a ductal infiltrating mammary tumor was induced in rats by 7,12-dimethylbenz[a]anthracene. Clones with different DNA/protein content, being the DI of 1.16, 1.30, and 1.60, respectively, were observed in the primary tumor. Biparametric flow cytometry suggested that the clone at 1.30 is made up of two subpopulations with different protein and slightly different DNA contents. The culture, after a few passages, exhibited the presence of aneuploid cells and the absence of diploid components, demonstrating that only tumor cells survived. The limiting dilution method gave rise to four lines with DI of 1.16, 1.25, 1.30, and 1.50; a mean chromosome number of 45, 46, 47, and 88, respectively; and different morphological and ultrastructural features. These characteristics were stable during the experimental procedure, that is, for about 20 passages. Conversely, the detection of cytoskeletal proteins indicated that the tumor epithelial cells underwent early dedifferentiation into sarcoma-like cells showing markers of stromal cell type and thus exhibiting phenotypic instability in vitro, a feature reported in many advanced human breast cancers in vivo. In conclusion, this cellular model represents the in vivo situation and appears suitable for in vitro studies of tumor cell characteristics and might be used to predict clinical behavior.

The cellular basis of tumor progression

Variability in disease presentation and course is a hallmark of cancer. Variability is seen among similarly diagnosed cancers in different patients or animal hosts and in the same cancer at different periods of time. This latter type of variability, termed "tumor progression," was defined by Foulds in a series of six rules that describe the independent behavior of individual cancers and the independent evolution of different cancer characteristics. Tumor progression is believed to result from variability among subpopulations of tumor cells within individual cancers and from selection of these subpopulations by conditions within the cancer environment, such that different subpopulations come to prominence over the course of cancer development and growth. Interactions among subpopulations, however, modulate tumor behavior as well as tumor evolution. The leading hypothesis for the origin of tumor subpopulations is the genetic instability of cancer cells. There are a number of possible mechanisms of genetic instability, some internal to cancer cells (mutation, amplification, mutator phenotypes, DNA repair deficiencies) and some present in the tumor microenvironment (endogenous mutagens). There are also potential epigenetic mechanisms of variability, including alterations in gene regulation, differentiation, adaptation, and cell fusion. Regardless of mechanism, the heterogeneity of tumor subpopulations poses a number of challenges to the practice of cancer research, including the design of reproducible and meaningful experiments. Tumor heterogeneity also has significant consequences for the clinical assessment of tumor prognosis and the development of effective treatment regimens.

Heterogeneity of DNA ploidy pattern in carcinoma of the gallbladder: primary and metastatic sites

There are few detailed reports on the heterogeneity of the nuclear DNA ploidy pattern in carcinoma of the gallbladder. We studied twelve autopsied cases who died of extended gallbladder carcinoma. Multiple samples were taken from the primary site (Pri), from direct invasion of the liver (Hinf), from hematogenous metastasis to the liver (H), from lymphatic metastasis (LN) and from peritoneal dissemination (P). The DNA ploidy pattern was investigated by image cytometry. Heterogeneity of the DNA ploidy pattern in Pri, Hinf, H, LN and P was found in 7/11, 2/10, 5/10, 2/6 and 3/6 cases, respectively. Aneuploidy was more frequently found in Hinf than at the Pri. The DNA index of Hinf was significantly higher than that of Pri. Several stemlines, with different quantities of DNA, were found in Pri. Most of these stemlines were also observed in other sites. These facts may suggest that polyclonal cancer cells rather than one cancer cell or monoclonal cancer cells of a Pri metastasize or infiltrate, and that various polyclonal cancer cells proliferate to different degrees under different circumstances.

Intratumoral heterogeneity in primary breast carcinoma: study of concurrent parameters

BACKGROUND AND OBJECTIVE

Intratumoral heterogeneity for prognostic factors (ploidy, proliferation, hormone receptor positivity) has been demonstrated in primary breast carcinoma by both flow cytometric and image analysis methods. Previously, heterogeneity in tumors had been demonstrated for only singular parameters. Our objective, using maps of tumors in which discrete regions can be analyzed simultaneously for DNA index (DI) and proliferative activity, was to demonstrate heterogeneity with respect to two parameters and to determine whether any interparametric relationships existed.

METHODS

We analyzed 25 cases of archived, paraffin-embedded breast carcinoma (ductal) for Feulgen stain DNA analysis and MIB-1 immunohistochemistry using the CAS 200 Image Cytometer. For each tumor, four discrete regions were analyzed including tumor-host tissue interface sectors.

RESULTS

Of 25 cases, 19 (76%) were homogeneously diploid or near-diploid aneuploid, and 6 (24%) were heterogeneous. Within the heterogeneous group, all cases had at least one diploid and one or more aneuploid populations from separate discrete regions. Five of six DI heterogeneous tumors displayed diploid values for the overall measurements of the respective tumors, based on analysis of 200 or more nuclei. Eight of 25 cases (32%) showed significant measurable variation for MIB-1 proliferative activity in various sectors of tumor. All the MIB-1 heterogeneous tumors, with one exception, were homogeneously diploid.

CONCLUSIONS

These findings demonstrate that (1) heterogeneity is present with respect to DI and proliferative activity in breast carcinoma and is relatively common, (2) tumors homogeneous for one parameter may be heterogeneous for another, and (3) heterogeneity for proliferative activity is more common in homogeneously diploid tumors than in heterogeneous/aneuploid tumors.

Progression of human breast cancers to the metastatic state is linked to hydroxyl radical-induced DNA damage

Hydroxyl radical damage in metastatic tumor DNA was elucidated in women with breast cancer, and a comparison was made with nonmetastatic tumor DNA. The damage was identified by using statistical models of modified base and Fourier transform-infrared spectral data. The modified base models revealed a greater than 2-fold increase in hydroxyl radical damage in the metastatic tumor DNA compared with the nonmetastatic tumor DNA. The metastatic tumor DNA also exhibited substantially greater base diversity than the nonmetastatic DNA, and a progression of radical-induced base damage was found to be associated with the growth of metastatic tumors. A three-dimensional plot of principal components from factor analysis, derived from infrared spectral data, also showed that the metastatic tumor DNA was substantially more diverse than the tightly grouped nonmetastatic tumor DNA. These cohesive, independently derived findings suggest that the hydroxyl radical generates DNA phenotypes with various metastatic potentials that likely contribute to the diverse physiological properties and heterogeneity characteristic of metastatic cell populations.