Cellular FLICE-inhibitory protein regulates chemotherapy-induced apoptosis in breast cancer cells

Combination treatment regimens that include topoisomerase-II-targeted drugs, such as doxorubicin, are widely used in the treatment of breast cancer. Previously, we demonstrated that IFN-� and doxorubicin co-treatment synergistically induced apoptosis in MDA435 breast cancer cells in a STAT1-dependent manner. In this study, we found that this synergy was caspase 8-dependent. In addition, we found that IFN-γ down-regulated the expression of the caspase 8 inhibitor c-FLIP. Furthermore, IFN-� down-regulated c-FLIP in a manner that was dependent on the transcription factors STAT1 and IRF1. However, IFN-� had no effect on c-FLIP mRNA levels, indicating that c-FLIP was down-regulated at a post-transcriptional level following IFN-� treatment. Characterisation of the functional significance of c-FLIP modulation by siRNA gene silencing and stable over-expression studies, revealed it to be a key regulator of IFN-γ- and doxorubicin-induced apoptosis in MDA435 cells. Analysis of a panel of breast cancer cell lines indicated that c-FLIP was an important general determinant of doxorubicin- and IFN-�-induced apoptosis in breast cancer cells. Furthermore, c-FLIP gene silencing sensitised MDA435 cells to other chemotherapies, including etoposide, mitoxantrone and SN-38. These results suggest that c-FLIP plays a pivotal role in modulating drug-induced apoptosis in breast cancer cells.

Cortactin underpins CD44-promoted invasion and adhesion of breast cancer cells to bone marrow endothelial cells

Using a validated tetracycline (tet)-regulated MCF7-founder (MCF7F) expression system to modulate expression of CD44 standard form (CD44s), we report the functional importance of CD44s and that of a novel transcriptional target of hyaluronan (HA)/CD44s signaling, EMS1/cortactin, in underpinning breast cancer metastasis. In functional experiments, tet-regulated induction of CD44s potentiated the migration and invasion of MCF7F cells through HA-supplemented Matrigel. EMS1/cortactin was identified by expression profiling as a novel transcriptional target of HA/CD44 signaling, an association validated by quantitative PCR and immunoblotting experiments in a range of breast cancer cell lines. The mechanistic basis underpinning CD44-promoted transcription of EMS1/cortactin was shown to be dependent upon a NFB mechanism, since pharmacological inhibition of IKinase-2 or suppression of p65 Rel A expression attenuated CD44-induced increases in cortactin mRNA transcript levels. Overexpression of a c-myc tagged murine cortactin construct in the weakly invasive, CD44-deficient MCF7F and T47D cells potentiated their invasion. Furthermore, the functional importance of cortactin to CD44s-promoted metastasis was demonstrated by selective suppression of cortactin in CD44-expressing MCF7F-B5 and MDA-MB-231 breast cancer cells using RNAi, which was shown to result in attenuated CD44-promoted invasion and CD44-promoted adhesion to bone marrow endothelial cells (BMECs).

BRCA1, a potential biomarker in the treatment of breast cancer

To date, estrogen receptor, progestogen receptor, and HER2/neu represent molecular biomarkers currently used in routine clinical practice to aid treatment decisions. Over the last few years, a large body of preclinical and retrospective clinical data has accumulated that suggests that BRCA1 mutation functions as a novel predictive marker of response to chemotherapy. This article reviews the role of BRCA1 as a predictive marker of chemotherapy response in breast cancer and examines the link between BRCA1 deficiency and the basal-like phenotype. Search strategy. Data for this article were identified through MEDLINE and PubMed searches for published reports using the terms BRCA1, breast cancer, basal-like, chemotherapy, prognosis, and predictive markers. In some cases, due to the restriction of space, readers are referred to review articles to allow further reading. Only articles published in English were included.