Breast cancer stem cells are defined as cancer cells with self-renewal capacity. These cells represent a small subpopulation endowed with the ability to form new tumours when injected in nude mice. Markers of differentiation have been used to identify these cancer cells. In the case of breast cancer, CD44+/CD24- select a population with stem cell properties. The fact that these cells have self-renewal ability has suggested that this population could be responsible for new tumour formation and cancer relapse. These cells have been shown to be more resistant to chemotherapy and radiotherapy than normal cancer cells. The identification of the molecular druggable alterations responsible for the initiation and maintenance of cancer stem cells is an important goal. In this article we will review all these points with special emphasis on the possible role of new drugs designed to interact with molecular pathways of cancer stem cells.
We report on two patients, successfully treated by the combination therapy of gemcitabine and 24-h intravenous infusion of cisplatin, who were initially diagnosed with node-positive advanced urothelial cancer. Each patient had a very good clinical response and underwent curative radical surgery after gemcitabine/cisplatin chemotherapy. A microscopically detailed examination of surgically obtained specimens showed the complete disappearance of malignant cells in the two cases. As a pilot study, we have used the regimen of gemcitabine plus 24-h continuous infusion of cisplatin, instead of bolus injection, for the treatment of 20 patients with node-positive or metastatic urothelial cancer. The clinical response rate in this regimen was 75% (complete response 7/20; 35%, partial response 8/20; 40%). The median overall survival was 665 days. As for the adverse effects, the incidences of severe neutropenia and thrombocytopenia (grade 3-4) were 20% and 15%, which might be less toxic than conventional gemcitabine plus cisplatin therapy. The 24-h infusion of cisplatin combined with gemcitabine can be highly recommended as neoadjuvant chemotherapy for locally advanced urothelial cancer.
We studied potential changes in the subventricular zone (SVZ) stem cell niche of the senescence-accelerated mouse prone-8 (SAM-P8) aging model. Bromodeoxyuridine (BrdU) assays with longtime survival revealed a lower number of label-retaining stem cells in the SAM-P8 SVZ compared with the SAM-Resistant 1 (SAM-R1) control strain. We also found that in SAM-P8 niche signaling is attenuated and the stem cell pool is less responsive to the self-renewal niche factor pigmented epithelium-derived factor (PEDF). Protein analysis demonstrated stable amounts of the PEDF ligand in the SAM-P8 SVZ niche; however, SAM-P8 stem cells present a significant expression decrease of patatin-like phospholipase domain containing 2, a receptor for PEDF (PNPLA2-PEDF) receptor, but not of laminin receptor (LR), a receptor for PEDF (LR-PEDF) receptor. We observed changes in self-renewal related genes (hairy and enhancer of split 1 (Hes1), hairy and enhancer of split 1 (Hes5), Sox2] and report that although these genes are down-regulated in SAM-P8, differentiation genes (Pax6) are up-regulated and neurogenesis is increased. Finally, sheltering mammalian telomere complexes might be also involved given a down-regulation of telomeric repeat binding factor 1 (Terf1) expression was observed in SAM-P8 at young age periods. Differences between these 2 models, SAM-P8 and SAM-R1 controls, have been previously detected at more advanced ages. We now describe alterations in the PEDF signaling pathway and stem cell self-renewal at a very young age, which could be involved in the premature senescence observed in the SAM-P8 model.
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