• Overcoming endocrine resistance in breast cancer: are signal transduction inhibitors the answer?

      Bedard, Philippe L; Freedman, Orit C; Howell, Anthony; Clemons, Mark; Division of Medical Oncology, Princess Margaret Hospital, Toronto, ON, Canada. (2008-04)
      Endocrine therapy is probably the most important systemic therapy for hormone receptor positive breast cancer. Hormonal manipulation was the first targeted treatment employed in breast cancer therapy even before the role of the estrogen (ER) and progesterone receptors (PR) had been elucidated. Unfortunately, a substantial proportion of patients, despite being ER and/or PR positive, are either primarily resistant to hormone therapies or will develop hormone resistance during the course of their disease. Signaling through complex growth factor receptor pathways, which activate the ER are emerging as important causes of endocrine resistance. Targeted therapies, such as signal transduction inhibitors (STIs), are being explored as agents to be able to potentially overcome this crosstalk and thus, resistance to hormone treatment. This article reviews the biology of the ER, the proposed mechanisms of endocrine resistance, and ongoing clinical trials with STIs in combination with hormonal manipulation as a means to overcome endocrine resistance.
    • Regulation of breast cancer stem cell activity by signaling through the Notch4 receptor.

      Harrison, Hannah; Farnie, Gillian; Howell, Sacha J; Rock, Rebecca E; Stylianou, Spyros; Brennan, Keith; Bundred, Nigel J; Clarke, Robert B; Breast Biology Group, School of Cancer, Enabling Sciences and Technology, Paterson Institute for Cancer Research, University of Manchester, Manchester Academic Health Sciences Centre, The Christie NHS Foundation Trust; Department of Medical Oncology, The Christie NHS Foundation Trust, Manchester M20 4BX, United Kingdom. (2010-01-15)
      Notch receptor signaling pathways play an important role not only in normal breast development but also in breast cancer development and progression. We assessed the role of Notch receptors in stem cell activity in breast cancer cell lines and nine primary human tumor samples. Stem cells were enriched by selection of anoikis-resistant cells or cells expressing the membrane phenotype ESA(+)/CD44(+)/CD24(low). Using these breast cancer stem cell populations, we compared the activation status of Notch receptors with the status in luminally differentiated cells, and we evaluated the consequences of pathway inhibition in vitro and in vivo. We found that Notch4 signaling activity was 8-fold higher in stem cell-enriched cell populations compared with differentiated cells, whereas Notch1 signaling activity was 4-fold lower in the stem cell-enriched cell populations. Pharmacologic or genetic inhibition of Notch1 or Notch4 reduced stem cell activity in vitro and reduced tumor formation in vivo, but Notch4 inhibition produced a more robust effect with a complete inhibition of tumor initiation observed. Our findings suggest that Notch4-targeted therapies will be more effective than targeting Notch1 in suppressing breast cancer recurrence, as it is initiated by breast cancer stem cells.
    • Systemic therapy for metastatic malignant melanoma--from deeply disappointing to bright future?

      Lorigan, Paul C; Eisen, Tim; Hauschild, Axel; CRUK Department of Medical Oncology, Christie Hospital NHS Trust, Wilmslow Road, Manchester, UK. paul.lorigan@manchester.ac.uk (2008-05)
      The last decade has seen a considerable improvement in the understanding of the biology of melanoma. Advances have come in the understanding of the importance of critical oncogenes and tumour suppressor genes, epigenetic phenomena, signalling pathways, drug resistance mechanisms, the pivotal role of the local immune system, and the importance of cell-cell and cell-matrix interactions. Many of these pathways and interactions include potentially 'drugable' targets. These developments have allowed the identification and/or design of a range of new, targeted therapies. Evaluation of these new drugs has brought a whole new series of challenges. These include identification of appropriate pre-clinical models, overcoming the redundancy in-built in complex biological systems, identification of appropriate molecular and clinical endpoints to show that the drug is hitting the target, how to combine treatments, and new toxicities. For the first time, there is the possibility of personalized treatment for melanoma patients, based on individual host and tumour characteristics. This paper discusses the range of new drugs and targets have been identified, the outcome of clinical trials, and the directions for future advances.