In an attempt to identify subtypes of breast cancer and pinpoint patterns of cell cycle regulatory defects associated with clinical behaviour, proliferation and other transformation associated events, a multitude of cell cycle regulatory proteins were analysed in a material of 113 primary breast cancers. Increased proliferation was observed in two different scenarios; (1) with high cyclin D1 and elevated retinoblastoma protein (pRb) phosphorylation, (cyclin D1 high tumours) or (2) with high cyclin E protein but low cyclin D1 and lack of corresponding pRb phosphorylation (cyclin E high tumours) indicative of an interrupted pRb pathway. Characteristic for cyclin E high tumours were further defects in p53, p27 and bcl-2, while c-erbB2 overexpression and c-myc amplification was found in both cyclin D1high and E high tumours. Using transfected cell lines overexpressing cyclin E, cyclin E high and D1 high tumours were mimicked and the cyclin D1 high cell line normalized the cyclin E kinase activity by an induction and redirection of p21 and p27 to the cyclin E complex whereas cyclin E high cell lines obtained increased kinase activity without redirection of inhibitors. Based on differences in genetic aberrations as well as function of the pRb node we therefore propose a model in which cyclin D1 high and cyclin E high tumours represent two alternative mechanisms to inactivate the pRb pathway and thereby achieve unrestrained growth in the tumorogenesis of breast cancer. Oncogene (2002Oncogene ( ) 21, 4680 -4690. doi:10.1038 Keywords: breast cancer; cell cycle; cyclins; cdkinhibitors; pRb pathway; proliferation IntroductionThe G1/S transition in normal cells is a thoroughly controlled checkpoint where the important decision to initiate DNA-replication or not is taken (Draetta, 1994;Weinberg, 1995). As has been obvious the last couple of years, aberrations in G1/S regulatory proteins are common in various tumours and aberrant expression of cyclin E and D1, downregulation of p16 and p27 as well as mutation of the retinoblastoma gene (Rb) has frequently been observed in several cancers and it can be hypothesized that G1/S defects might be obligatory in tumour development (Landberg and Roos, 1997;Sandhu and Slingerland, 2000).Cyclin D1 links mitogenic signals to cell cycle progression through increased phosphorylation of pRb (Lukas et al., 1996). Amplification of the encoding cyclin D1 gene, CCND1, resulting in high cyclin D1 protein content, has been observed in a significant numbers of breast cancers and together with impaired cyclin D1 protein degradation potentially cause unbalanced phosphorylation of pRb (Sherr, 1996;Russell et al., 1999). The relation between cyclin D1 and in vivo pRb phosphorylation in primary breast cancer has nevertheless not been investigated. Overexpression of cyclin D1 has been associated with ERpositivity (Michalides et al., 1996;van Diest et al., 1997), while the relation to proliferation and survival has been without consensus (Jares et al., 1997;Barnes and Gillett, 1998). Nevertheless, simila...

ID proteins have been implicated in the regulation of cell proliferation and differentiation in various cell types during normal development as well as in the formation of cancer. Our aim was to delineate the expression of ID2 by immunohistochemistry in primary breast cancer in order to detect potential associations with cell cycle regulatory proteins and/or clinicopathologic parameters. We further overexpressed ID2 in a breast cancer cell line to elaborate potential effects on proliferation and invasiveness. We observed large variations in ID2 expression in primary breast cancer, and the protein was localised to both the nucleus and cytoplasm. Interestingly, a high cytoplasmic ID2 protein level correlated with a favourable prognosis. Overexpressing ID2 in the MDA-MB-468 breast cancer cell line generated a marked cytoplasmic localisation of the protein and reduced the invasive capacity of cells. Modest enhancement of cell proliferation was further detected in ID2-overexpressing cells. In conclusion, ID2 protein expression varies substantially within primary breast tumours and high cytoplasmic levels of ID2 might reflect a less aggressive breast tumour phenotype. ' 2005 Wiley-Liss, Inc.Key words: ID2; breast cancer; proliferation; invasion The cell cycle regulatory machinery is a highly complex and delicate system that often is abrogated in cancer, and tumour cells consequently override one or more cell cycle checkpoints. One important checkpoint is the G 1 -S transition, where cells are committed to DNA replication and subsequent division. The cell cycle regulatory machinery is dependent on the activity of different CDKs and their associated cyclins, whose expression is tightly regulated over the cell cycle. Regulators of kinase activity are inhibitory proteins like p21, p27 and p16. One of the major substrates for the CDKs is pRb. Overexpression or inactivation of cell cycle regulatory proteins leads to abnormal proliferation and lack of checkpoint control. For example, inactivation of pRb has been noted in about 60% of all human cancers either by mutation and gene deletions or by deregulated phosphorylation, sequestration by oncoproteins or loss of cooperating factors.ID2 is a multipotent regulatory molecule harbouring an HLH motif. Through the HLH domain, ID proteins (ID1-ID4 in mammals) bind and sequester the DNA binding bHLH proteins known as E proteins, thereby preventing them from binding DNA alone or in complex with tissue-specifically expressed bHLH proteins. Since these latter bHLH proteins often are associated with differentiation and decreased proliferation, elevated ID protein levels often lead to maintained proliferation, whereas decreased ID protein levels are associated with differentiation.In the normal mammary epithelium, ID2 has been linked to critical steps in the development of functional mammary glands.2 The phenotype of homozygous ID2 knockout mice reveals lactation defects due to poor expansion of lobulo-alveolar tissue in the mammary glands, possibly caused by decreased proliferation of...

Cell cycle deregulation is a prerequisite in tumor development and overexpression of cyclin E, a major G 1 -S regulator, is often observed in breast cancer and is further linked to poor prognosis. By overexpressing cyclin E in a retinoblastomainactivated breast cancer cell line, we induced significant alterations in the expression of genes associated with proliferation and cell adhesion. Rearrangements of the actin cytoskeleton in addition to increased adhesive properties, decreased motility, and invasive potential in functional assays, indicated an overall abrogated mobility. Consistent in vivo findings were obtained upon investigation of 985 primary breast cancers, where cyclin E-high tumors predominantly (67%) displayed a low infiltrative, pushing growth pattern. Furthermore, medullary breast cancers, a subtype defined by its pushing, delimited growth, exhibited a remarkable frequency of cyclin E deregulation (87%) compared with other histologic subtypes (5-20%). Taken together, our results suggest the novel role of cyclin E in modeling infiltrative behavior. The consequences of cyclin E overexpression in breast cancer seems to be multiple, including effects on proliferation as well as growth patterns, a scenario that is indeed observed in the archetype of cyclin E-overexpressing medullary breast cancers. (Cancer Res 2005; 65(21): 9727-34)

Cyclin E confers a prognostic value in premenopausal breast cancer patients with tumours exhibiting an infiltrative growth pattern.Berglund, Pontus; Stighall, Maria; Jirström, Karin; Rydén, Lisa; Fernö, Mårten; Nordenskjold, Bo; Landberg, Göran Link to publication Citation for published version (APA): Berglund, P., Stighall, M., Jirström, K., Rydén, L., Fernö, M., Nordenskjold, B., & Landberg, G. (2008). Cyclin E confers a prognostic value in premenopausal breast cancer patients with tumours exhibiting an infiltrative growth pattern. Journal of Clinical Pathology, 61, 184-191. DOI: 10.1136/jcp.2007 General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal AbstractAim: This study investigates the prognostic value of cyclin E in relation to tumour growth pattern by analysing stage II primary breast cancers from premenopausal women not subjected to any further adjuvant treatment. In addition, the value of cyclin E as a predictor of tamoxifen response was analysed, by comparing untreated and treated patients with oestrogen receptor positive tumours. Methods: Breast cancer samples, assembled in tissue microarrays, were immunohistochemically stained for cyclin E and evaluated regarding the presence of nuclear staining. The overall growth characteristics of each tumour were assessed using whole tissue sections. Results: Tumours displaying a pushing margin phenotype were strongly associated with high cyclin E levels, lymph node negative disease, a high histological grade, ER negativity, and exhibited a better prognosis compared to tumours with an infiltrative growth pattern. In the total cohort of non-treated patients (N=187), cyclin E was not associated with recurrence free survival (RFS). However, when analysing the subgroup of tumours lacking a pushing growth pattern (N=141), cyclin E was significantly associated with RFS, independent of histological grade and node status. There was no significant difference in tamoxifen response with regard to different cyclin E levels. Conclusion:The prognostic value of cyclin E in premenopausal breast cancer is limited to patients with breast carcinomas exhibiting an exclusively infiltrative growth pattern. This limitation could be explained by the presence of a small but distinct subgroup of cyclin E-high breast cancers with a pushing margin phenotype and a more favourable outcome.