Molecular characterization of intraductal breast carcinomas

Prostate-tumor-inducing gene-1 analysis in human prostate cancer cells and tissue in relation to Mycoplasma infection

The potential role of PTI-1, in the natural story of prostate adenocarcinoma remains to be fully determined. PTI-1 expression was evaluated in human prostate cancer cell lines and in paraffin-embedded archive tissues. PTI-1 expression was found in Mycoplasma infected but not in non-infected cells. The lack of PTI-1 expression was also confirmed in fixed and paraffin-embedded human cancer prostate biopsies. The overall data indicate that, in prostate tumor cell lines, PTI-1 presence parallels Mycoplasma infection suggesting that PTI-1 might not necessarily play a major role in the onset of prostate tumorigenesis.

Cyclin E expression is correlated with tumor progression and predicts a poor prognosis in patients with ovarian carcinoma

BACKGROUND

Cyclins, cyclin dependent kinases (cdks), and their inhibitors act in combination to regulate progression through the cell cycle and often are dysregulated in carcinoma. The authors hypothesized that cyclin E plays an important role in ovarian carcinogenesis and that its overexpression may be an indicator of a poor prognosis.

METHODS

Immunohistochemical analysis of cyclin E expression was performed by image analysis in normal ovaries, cystadenomas, tumors of low malignant potential, and 405 primary ovarian carcinomas by using tissue microarray technology.

RESULTS

Overexpression of cyclin E was found in 63.2% of the samples and was associated with clear cell, poorly differentiated, and serous carcinoma (P < or = .001), high-grade tumors (P < or = .001), late-stage disease (P = .002), age older than 60 years at the time of diagnosis (P = .04), and suboptimal cytoreduction (P = .001). A high percentage of cyclin E-expressing cells was associated with a poor outcome in univariate and in multivariate analyses. In addition, cyclin E levels also reduced survival in the late-stage disease group and in patients who underwent suboptimal debulking.

CONCLUSIONS

Cyclin E was identified as an independent prognostic factor in patients with ovarian carcinoma. The accumulation of cyclin E protein may be a late event in tumorigenesis and may contribute to disease progression in these patients.

Effect of a farnesyl transferase inhibitor (R115777) on ductal carcinoma in situ of the breast in a human xenograft model and on breast and ovarian cancer cell growth in vitro and in vivo

Introduction

The ras pathway is essential for cell growth and proliferation. The effects of R115777, a farnesyl transferase inhibitor, were investigated in cancer cell lines expressing varying levels of growth factor receptors and with differing ras status. Effects on tumour xenografts and human ductal carcinoma in situ (DCIS) of the breast in a xenograft mouse model were also tested.

Method

In vitro, the concentrations required to reduce cell numbers by 50% (50% inhibitory concentration) were established (MDA-MB231, MCF-7, MCF-7/HER2-18, BT-474, SK-BR3 and SKOV3). Human DCIS was implanted in nude mice or, in separate experiments, cultured cells were injected (MDA-MB231, MCF-7/HER2-18, SKOV3) and allowed to form tumours. Proliferation and apoptosis were determined by immunohistochemistry in xenografts and cell tumours.

Results

The 50% inhibitory concentrations varied a hundred-fold, from 39 nmol/l (± 26 nmol/l) for SKBR3 to 5.9 μmol/l(± 0.8 μmol/l) for MDA-MB231. In MCF-7/HER2-18 and SKOV3 cells the levels of tumour growth inhibition were approximately 85% and 40%, respectively. There was a significant decrease in the cell turnover index (CTI; proliferation/apoptosis). In MDA-MB 231 with activated k-ras no inhibition was observed. In treated DCIS xenografts proliferation decreased and apoptosis increased. The CTI ratio between the start and 1 and 2 weeks of treatment were 1.99 and 1.50, respectively, for controls and 0.85 (P = 0.005) and 0.75 (P = 0.08) for treated xenografts.

Conclusion

Treatment with the farnesyl transferase inhibitor reduced cell growth in vitro and cell tumour growth in vivo. In DCIS treatment resulted in a reduced CTI. R115777 is a promising treatment for breast cancer but the relation between effect and growth factor receptor and ras status has to be established.

Expression of cyclin-dependent kinases and CDC25a phosphatase is related with recurrences and survival in women with peri- and post-menopausal breast cancer

Progression through the mammalian cell cycle is regulated by cyclin-cyclin-dependent kinase (CDKs) complexes that are activated throughout the cell cycle. Alteration in cell cycle control could lead to proliferation and tumourogenesis. This study was designed to analyse, at messenger RNA (mRNA) level, cyclins and CDKs involved in the retinoblastoma pathway, as well as cell division cycle 25a phosphatase (CDC25a), which activates some of the CDKs that were analysed. The aim of the study was to determine the possible prognostic relevance of these molecules in 73 women with peri- and post-menopausal breast cancer. Cyclins A, D1 and E; CDKs 2, 4 and 6 and phosphatase CDC25a expression status were analysed in primary tumours at mRNA level, by reverse transcriptase polymerase chain reaction analysis in paraffin-embedded primary breast cancers. High expression levels of CDK2, CDK4 and CDC25a were related to tumour recurrence. Over-expression of CDK2 and CDC25a was also associated with reduced overall survival; moreover, the CDK2 expression level was able to define a short-living cohort of patients with tumour-positive lymph nodes. CDK2, CDK4 and CDC25a can be used as reliable biomarkers to predict prognosis in women with peri- and post-menopausal breast cancer.

Biological variables and prognosis of DCIS

Based on current knowledge, biological factors that have been investigated in ductal carcinoma in situ (DCIS) include histology of these lesions, the impact of margin status on local recurrence, and several genetic alterations. Optimal integration of these factors in guiding optimal therapy is of great importance, since the incidence of DCIS is rising as a result of population-based mammographic screening. Mastectomy will almost always cure patients with DCIS but represents overtreatment for many. Less extensive treatment options should combine an optimal cosmetic result with the same safety for outcome of disease as mastectomy. To guide such optimal treatment, histological classification is not sufficient and additional biological factors are being investigated for their ability to predict outcome for individual patients with DCIS. In this review, the histological classification of DCIS is described and in addition the emerging knowledge on genetic alterations is summarised. For clinical management of DCIS patients, genetic or other biological factors should be identified that can predict the risk of progression of DCIS to invasive breast cancer and distant metastases. At present, insufficient knowledge on prognostic and predictive factors in DCIS is available. Research in this area is hampered by the difficulties in obtaining DCIS tumour tissue, as the tumour cells grow in the lumen of pre-existing ducts and lobules. As the recurrence rates are relatively low and the most relevant clinical endpoint, distant metastases, is indeed very rare, large numbers of patients (hundreds to a few thousand) need to be studied. Integration of translational studies into clinical trials aimed at optimising the treatment of DCIS are required to achieve this goal.

Expression of cyclins A, E and topoisomerase II alpha correlates with centrosome amplification and genomic instability and influences the reliability of cytometric S-phase determination

BACKGROUND

The progression of normal cells through the cell cycle is meticulously regulated by checkpoints guaranteeing the exact replication of the genome during S-phase and its equal division at mitosis. A prerequisite for this achievement is synchronized DNA-replication and centrosome duplication. In this context the expression of cyclins A and E has been shown to play a principal role.

RESULTS

Our results demonstrated a correlation between centrosome amplification, cell cycle fidelity and the level of mRNA and protein expression of cyclins A and E during the part of the cell cycle defined as G1-phase by means of DNA content based histogram analysis. It is shown that the normal diploid breast cell line HTB-125, the genomically relatively stable aneuploid breast cancer cell line MCF-7, and the genomically unstable aneuploid breast cancer cell line MDA-231 differ remarkably concerning both mRNA and protein expression of the two cyclins during G1-phase. In MDA-231 cells the expression of e.g. cyclin A mRNA was found to be ten times higher than in MCF-7 cells and about 500 times higher than in HTB-125 cells. Topoisomerase II alpha showed high mRNA expression in MDA compared to MCF-7 cells, but the difference in protein expression was small. Furthermore, we measured centrosome aberrations in 8.4% of the MDA-231 cells, and in only 1.3% of the more stable aneuploid cell line MCF-7. MDA cells showed 27% more incorporation of BrdU than reflected by S-phase determination with flow cytometric DNA content analysis, whereas these values were found to be of the same size in both HTB-125 and MCF-7 cells.

CONCLUSIONS

Our data indicate that the breast cancer cell lines MCF-7 and MDA-231, although both DNA-aneuploid, differ significantly regarding the degree of cell cycle disturbance and centrosome aberrations, which partly could explain the different genomic stability of the two cell lines. The results also question the reliability of cytometric DNA content based S-phase determination in genomically unstable tumor cell populations.

Cyclin E immunoexpression in breast ductal carcinoma: pathologic correlations and prognostic implications

Abnormalities of the cell cycle are present in all neoplasms. Cyclin E, which regulates the G1/S phase transition of the cell cycle, plays an important role in many different cancers. To further investigate the role of cyclin E in invasive breast ductal carcinomas in South African women, representative sections from 157 mastectomy and axillary clearance specimens were stained with the cyclin E antibody. The results were compared with known clinicopathologic prognostic factors, namely lymph node metastases, size, estrogen receptor status, and histologic grade. Positive (nuclear) cyclin E immunostaining strongly correlates with negative estrogen receptor status and high grade. These correlations may account for the observation that although cyclin E staining is associated with poor prognosis in univariate analysis, no prognostic significance remains after multivariate analysis.

Gene amplifications detected by fluorescence in situ hybridization in pure intraductal breast carcinomas: relation to morphology, cell proliferation and expression of breast cancer-related genes

Investigation of early breast carcinogenesis is limited by the difficulty in obtaining cell cultures or adequate fresh frozen material and by the fact that available data from in situ techniques are interpreted in terms of various classification systems. Our studies in a series of pure ductal carcinomas in situ (DCIS) were conducted in accordance with the recommendations of the international Consensus Conference (Hum. Pathol., 28, 122-125, 1997) relative to processing, determination of lesion extent, and histological stratification primarily on nuclear grade (NG). A multifactorial study performed in 15 low- and 16 high-NG DCIS (68% detected by mammography) included the following: (1) morphological analysis of NG, necrosis, and architectural pattern; (2) detection of numerical genomic abnormalities at ERBB2, MYC, CCND1, Xq1.2 and 20q13 loci by fluorescence in situ hybridization on interphase nuclei; and (3) immunohistochemical determination of cell proliferation, p53 accumulation, hormonal receptors and bcl-2 expression on serial sections of formalin-fixed, paraffin-embedded specimens. High NG, comedo/solid pattern and necrosis were significantly associated with amplification at one or more loci, the number of amplified loci, amplification at the ERBB2 locus, absence of bcl-2 and hormonal receptor expression and high cell proliferation (p < 0.05). High NG and comedo/solid pattern were significantly associated with MYC amplification and p53 accumulation, and necrosis with CCND1 amplification (the only gene amplification detected in low NG DCIS). These data provide additional information on the early steps of breast carcinogenesis, in accordance with currently recognized criteria of histological classification.

Balance of cell proliferation and apoptosis in breast carcinogenesis

We determined the mitotic and apoptotic index through the spectrum of pre-invasive ductal breast lesions to invasive carcinoma in search of disturbances in the proliferation/cell death balance in breast carcinogenesis. Seventy-two pure pre-invasive ductal breast lesions (without invasive carcinoma) and 103 invasive breast carcinomas were used. The numbers of mitotic and apoptotic cells were microscopically counted in hematoxylin and eosin stained sections (MI and AI, respectively), and the ratio of the values of MI and AI was calculated for each individual case (M/A index). A distinction was made between well differentiated and poorly differentiated breast lesions, based on histological type and nuclear grade, to arrive at two plausible progression models for breast carcinogenesis. For the well differentiated breast lesions, the MI was rather equal for hyperplasias and well differentiated DCIS, but increased 6-fold from DCIS to well differentiated invasive carcinoma. The AI remained in the same range, resulting in a 4-fold increase of the M/A index. For the poorly differentiated breast lesions, a significant increase in MI and AI was found from hyperplasia to poorly differentiated DCIS. From DCIS to poorly differentiated invasive carcinoma, the MI increased significantly and the AI decreased 2-fold (n.s.), resulting in a 2.5-fold significant increase of the M/A index. In conclusion, the net increase of the number of cells in the transition from well differentiated pre-invasive to well differentiated invasive carcinoma is accompanied by an increase of cell proliferation rather than decrease in apoptosis, suggesting that in these lesions, proliferation related mechanisms are most important in carcinogenesis and progression. In contrast, in poorly differentiated breast lesions, decreased apoptosis seems to be also important in carcinogenesis and progression. At present, we are gathering patients with invasive breast cancer who had a previous biopsy with a pre-invasive lesion to obtain further more direct evidence for this hypothesis.

Cyclin E in human cancers

Regulators of the cell cycle such as cyclin E play an important part in neoplasia. The cyclin E protein forms a partnership with a specific protein kinase. This complex phosphorylates key substrates to initiate DNA synthesis. Cyclin-dependent kinase inhibitors (CKIs) are able to suppress the activity of cyclin E. Various substances (including proteins produced by oncogenic viruses) affect cyclin E directly or indirectly through an interaction with CKIs. These interactions are important in elucidating the mechanisms of neoplasia. They may also provide prognostic information in a wide range of common cancers. Cyclin E may even be a target for treatment of cancers in the future.

Cyclins and breast cancer

Cyclins are regulatory subunits for cyclin dependent kinases in the coordination of the cell cycle. Cyclins can also serve non-cell cycle functions, such as the transactivation of estrogen receptor by cyclin D. Evidence for the participation of the G1 cyclins D and E in breast cancer is summarized, including transgenic and knockout mice, transfections, and expression patterns in cohort studies. Overexpression of cyclin D has been reported in ductal carcinoma in situ (DCIS), and similar overexpression of cyclin E is suggested. Strategies to reduce cyclin expression are discussed as potential prevention efforts.

Comparative genomic hybridization of ductal carcinoma in situ of the breast-evidence of multiple genetic pathways

There is strong evidence that ductal carcinoma in situ (DCIS) represents a precursor lesion of invasive breast cancer. In order to analyse specific chromosomal alterations of DCIS, 38 paraffin-embedded specimens of DCIS and six associated invasive carcinomas were examined by means of comparative genomic hybridization (CGH). Losses of 16q material were seen almost exclusively in well- and intermediately-differentiated DCIS. These two subgroups differed in the average number of genetic imbalances, 2.5 and 5.5 respectively. Additionally, a higher frequency of gains of 1q and losses of 11q material was seen in intermediately-differentiated in contrast to well-differentiated DCIS. Poorly-differentiated DCIS displayed a higher frequency of amplifications (17q12, 11q13) and a higher average rate of genetic imbalances (7.1). Analysis of adjacent invasive breast carcinoma revealed a genetic pattern almost identical to the one seen in the DCIS counterpart. These data characterize DCIS as a genetically far-advanced, heterogeneous lesion and as a direct precursor of invasive breast cancer.