Mammosphere formation in breast carcinoma cell lines depends upon expression of E-cadherin.

Tumors are heterogeneous at the cellular level where the ability to maintain tumor growth resides in discrete cell populations. Floating sphere-forming assays are broadly used to test stem cell activity in tissues, tumors and cell lines. Spheroids are originated from a small population of cells with stem cell features able to grow in suspension culture and behaving as tumorigenic in mice. We tested the ability of eleven common breast cancer cell lines representing the major breast cancer subtypes to grow as mammospheres, measuring the ability to maintain cell viability upon serial non-adherent passage. Only MCF7, T47D, BT474, MDA-MB-436 and JIMT1 were successfully propagated as long-term mammosphere cultures, measured as the increase in the number of viable cells upon serial non-adherent passages. Other cell lines tested (SKBR3, MDA-MB-231, MDA-MB-468 and MDA-MB-435) formed cell clumps that can be disaggregated mechanically, but cell viability drops dramatically on their second passage. HCC1937 and HCC1569 cells formed typical mammospheres, although they could not be propagated as long-term mammosphere cultures. All the sphere forming lines but MDA-MB-436 express E-cadherin on their surface. Knock down of E-cadherin expression in MCF-7 cells abrogated its ability to grow as mammospheres, while re-expression of E-cadherin in SKBR3 cells allow them to form mammospheres. Therefore, the mammosphere assay is suitable to reveal stem like features in breast cancer cell lines that express E-cadherin.

Células madre tumorales: una diana terapéutica en el cáncer de mama / Cancer stem cells: a therapeutic target in breast cancer

En los últimos años se ha identificado un pequeño número de células en los tumores con características de células madre que se han observado en distintos tipos de tumor, incluido el cáncer de mama. Estas células, las células madre tumorales, resultan de gran interés, ya que se les atribuye la capacidad de originar, mantener y expandir los tumores, así como de dar lugar a las metástasis y recidivas. Por otro lado, estas células han demostrado ser más resistentes a tratamientos convencionales utilizados en oncología, como la quimioterapia o la radioterapia; por tanto, suponen un candidato claro para la generación de recidivas. La caracterización molecular de estas células se ha convertido en uno de los campos más activos en la investigación oncológica, ya que los tratamientos dirigidos contra estas células podrían dar lugar a una eliminación completa del tumor y, por lo tanto, a la curación de la enfermedad (AU)

In recent years, a small population of cells with stem cell properties, and named cancer stem cells (CSC), has been identified in a wide variety of tumours, including breast cancer. The increasing interest in CSCs resides in the ability of this cell population to originate, maintain and expand the tumour, thus being responsible for tumour initiation, metastasis and relapses. As these cells have shown to be more resistant to conventional cancer treatments, such as chemotherapy or radiotherapy, it has been suggested that they may be responsible for relapses. The molecular characterization of these cells is one of the most active research areas in oncology, as targeting this cell population may become necessary for a complete elimination of the tumour and possibly a definitive cure of the disease (AU)

Xenografts in zebrafish embryos as a rapid functional assay for breast cancer stem-like cell identification.

The cancer stem cell is defined by its capacity to self-renew, the potential to differentiate into all cells of the tumor and the ability to proliferate and drive the expansion of the tumor. Thus, targeting these cells may provide novel anti-cancer treatment strategies. Breast cancer stem cells have been isolated according to surface marker expression, ability to efflux fluorescent dyes, increased activity of aldehyde dehydrogenase or the capacity to form spheres in non-adherent culture conditions. In order to test novel drugs directed towards modulating self-renewal of cancer stem cells, rapid, easy and inexpensive assays must be developed. Using 2 days-post-fertilization (dpf) zebrafish embryos as transplant recipients, we show that cells grown in mammospheres from breast carcinoma cell lines migrate to the tail of the embryo and form masses with a significantly higher frequency than parental monolayer populations. When stem-like self-renewal was targeted in the parental population by the use of the dietary supplement curcumin, cell migration and mass formation were reduced, indicating that these effects were associated with stem-like cell content. This is a proof of principle report that proposes a rapid and inexpensive assay to target in vivo cancer stem-like cells, which may be used to unravel basic cancer stem cell biology and for drug screening.