Genistein induces enhanced growth promotion in ER-positive/erbB-2-overexpressing breast cancers by ER-erbB-2 cross talk and p27/kip1 downregulation.

Genistein is a major isoflavone with known hormonal and tyrosine kinase-modulating activities. Genistein has been shown to promote the growth of estrogen receptor positive (ER+) MCF-7 cells. In ER-negative (ER-)/erbB-2-overexpressing (erbB-2+) cells, genistein has been shown to inhibit cell growth through its tyrosine kinase inhibitor activity. The effects of genistein on cell growth and tamoxifen response in ER+/erbB-2-altered breast cancers (known as luminal type B and noted in approximately 10 to 20% of breast cancers) have not been well explored. Using erbB-2-transfected ER+ MCF-7 cells, we found that genistein induced enhanced cellular proliferation and tamoxifen resistance when compared with control MCF-7 cells. These responses were accompanied by increased phosphorylation of ERalpha and ER signaling, without increase in ER protein levels. Genistein-treated MCF-7/erbB-2 cells also showed enhanced activation/phosphorylation of erbB-2, Akt and mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase. Blockade of the phosphatidylinositol 3-kinase and/or MAPK pathways abrogated genistein-induced growth promotion, suggesting that genistein effects involve both critical signaling pathways. We also found that p27/kip1 was markedly downregulated in genistein-treated MCF-7/erbB-2 cells. Overexpression of p27/kip1 attenuated genistein-mediated growth promotion. In aggregate, our data suggest that the concomitant coexpression of ER and erbB-2 makes breast cancers particularly susceptible to the growth-promoting effects of genistein across a wide range of doses. The underlying mechanisms involve enhanced ER-erbB-2 cross talk and p27/kip1 downregulation.

Bcl-2 overexpression sensitizes MCF-7 cells to genistein by multiple mechanisms.

Genistein is a soy isoflavone with anti-tumor properties. Genistein-induced apoptosis involves Bcl-2 downregulation. However, overexpression of Bcl-2 in breast cancer has been associated with better prognosis and response to hormonal therapy. To examine genistein's effect on breast cancer cells with different Bcl-2 levels, we established control (MCF-7/PV) and Bcl-2 overexpressing MCF-7 (MCF-7/Bcl-2) cell lines and characterized genistein regulated apoptosis and cell cycle progression in these cells. Our results demonstrate that overexpression of Bcl-2 rendered MCF-7 cells more sensitive, rather than resistant, to genistein. We found that genistein induces enhanced cytochrome c release and mitochondrial membrane depolarization in MCF-7/Bcl-2 cells, as compared to control. We also found that genistein increases Bcl-2 levels and Bcl-2/Bax ratio in the mitochondrial fractions of MCF-7/Bcl-2 cells, suggesting that disturbed Bcl-2/Bax distribution may cause cytochrome c release and apoptosis in these cells. Cell cycle analysis indicated that genistein induces G0/G1 arrest in MCF-7/PV cells but increases in G2/M arrest in MCF-7/Bcl-2 cells. This was accompanied by modified responses of several cell cycle regulators, such as p21 and cyclin B1. Taken together, our results indicate that genistein-Bcl-2 interaction switches Bcl-2 from an anti-apoptotic protein into a proapoptotic protein, which involves disturbed Bcl-2/Bax distribution in mitochondria, increased cytochrome c release and modified cell cycle regulation.

Quantitative alterations in nuclear structure predict prostate carcinoma distant metastasis and death in men with biochemical recurrence after radical prostatectomy.

BACKGROUND: Microscopic histologic grade has been the best predictor of prostate carcinoma (PCa) progression in men after surgical therapy. The ability to predict accurately, at the time of surgery, which patients are likely to develop metastatic PCa would enable optimization of disease management with adjuvant therapy. The authors assessed the ability of pathologic, nuclear morphometric, and chromatin parameters to predict metastatic PCa progression and/or death in 227 men with biochemical recurrence and long-term follow-up after undergoing radical prostatectomy. METHODS: Multivariate logistic regression (LR) was used to calculate quantitative nuclear grade (QNG) solutions using the variances of 60 nuclear morphometric descriptors (NMDs) of nuclear size, shape, DNA content, and chromatin organization that predicted distant metastasis and/or PCa-specific death. An LR model also was generated to predict this outcome using a combination of pathologic variables and the best QNG solution. Cox proportional hazards models were generated, and Kaplan-Meier plots were used to display three risk groups based on pathology, QNG, and a combination of these variables. RESULTS: A multivariate LR model using pathology retained lymph node (LN) status, seminal vesicle status, and prostatectomy Gleason score, yielding an area under the curve-receiver operator characteristic (AUC-ROC) of 75% with an accuracy of 59% at 90% sensitivity. The best QNG solution used the variance of 25 NMDs, yielding an AUC-ROC of 84% and an accuracy of 70% at 90% sensitivity. The combined pathology-QNG model retained LN status, prostatectomy Gleason score, and QNG, yielding an AUC-ROC of 86% with an accuracy of 76% at 90% sensitivity. The Cox proportional hazards models produced the following significant univariate and multivariate hazard ratios: QNG, 3.5 and 2.9, respectively; LN, 2.7 and 1.8, respectively; and prostatectomy Gleason score, 2.8 and 2.1, respectively. CONCLUSIONS: Alterations in the structure of tumor nuclei measured by computer-assisted image analysis were strong predictors of PCa progression and death in men with long-term follow-up who had biochemical recurrence after undergoing radical prostatectomy. QNG solutions can serve as a new supplemental biomarker for accurate prediction of PCa progression at the time of surgery.