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Initially correlated with hematopoietic precursors, the surface expression of CD133 was also found in epithelial and nonepithelial cells from adult tissues in which it has been associated with a number of biological events. CD133 is expressed in solid tumors as well, including breast cancer, in which most of the studies have been focused on its use as a surface marker for the detection of cells with stem-like properties (i.e., cancer stem cells (CSCs)). Differently with other solid tumors, very limited and in part controversial are the information about the significance of CD133 in breast cancer, the most common malignancy among women in industrialized countries. In this review, we summarize the latest findings about the implication of CD133 in breast tumors, highlighting its role in tumor cells with a triple negative phenotype in which it directly regulates the expression of proteins involved in metastasis and drug resistance. We provide updates about the prognostic role of CD133, underlining its value as an indicator of increased malignancy of both noninvasive and invasive breast tumor cells. The molecular mechanisms at the basis of the regulation of CD133 levels in breast tumors have also been reviewed, highlighting experimental strategies capable to restrain its level that could be taken into account to reduce malignancy and/or to prevent the progression of breast tumors. [ABSTRACT FROM AUTHOR]

Clusterin (CLU) is a chaperone‐like protein with multiple functions. sCLU is frequently upregulated in prostate tumor cells after chemo‐ or radiotherapy and after surgical or pharmacological castration. Moreover, CLU has been documented to modulate the cellular homolog of murine thymoma virus akt8 oncogene (AKT) activity. Here, we investigated how CLU overexpression influences phosphatidylinositol 3′‐kinase (PI3K)/AKT signaling in human normal and cancer epithelial prostate cells. Human prostate cells stably transfected with CLU were broadly profiled by reverse phase protein array (RPPA), with particular emphasis on the PI3K/AKT pathway. The effect of CLU overexpression on normal and cancer cell motility was also tested. Our results clearly indicate that CLU overexpression enhances phosphorylation of AKT restricted to isoform 2. Mechanistically, this can be explained by the finding that the phosphatase PH domain leucine‐rich repeat‐containing protein phosphatase 1 (PHLPP1), known to dephosphorylate AKT2 at S474, is markedly downregulated by CLU, whereas miR‐190, a negative regulator of PHLPP1, is upregulated. Moreover, we found that phosphatase and tensin homolog (PTEN) was heavily phosphorylated at the inhibitory site S380, contributing to the hyperactivation of AKT signaling. By keeping AKT2 phosphorylation high, CLU dramatically enhances the migratory behavior of prostate epithelial cell lines with different migratory and invasive phenotypes, namely prostate normal epithelial 1A (PNT1A) and prostatic carcinoma 3 (PC3) cells. Altogether, our results unravel for the first time a circuit by which CLU can switch a low migration phenotype toward a high migration phenotype, through miR‐190‐dependent downmodulation of PHLPP1 expression and, in turn, stabilization of AKT2 phosphorylation. In human prostate cells, clusterin (CLU) overexpression was found to enhance the phosphorylation of AKT restricted to isoform 2. Mechanistically, this was explained by the finding that the phosphatase PHLPP1, known to dephosphorylate AKT2 at S474, is markedly downregulated by CLU, whereas miR‐190, a negative regulator of PHLPP1, is upregulated. Moreover, we found that PTEN was heavily phosphorylated at the inhibitory site S380, contributing to the hyperactivation of AKT signaling. Remarkably, we also demonstrated that by keeping AKT2 phosphorylation high, CLU dramatically enhances the migratory behavior of prostate epithelial cell lines with different migratory and invasive phenotype, namely PNT1A and PC3 cells. [ABSTRACT FROM AUTHOR]

Background: The malignant potential of triple negative breast cancer (TNBC) is also dependent on a sub-population of cells with a stem-like phenotype. Among the cancer stem cell markers, CD133 and EpCAM strongly correlate with breast tumor aggressiveness, suggesting that simultaneous targeting of the two surface antigens may be beneficial in treatment of TNBC. Since in TNBC-derived cells we demonstrated that PLC-β2 induces the conversion of CD133high to CD133low cells, here we explored its possible role in down-modulating the expression of both CD133 and EpCAM and, ultimately, in reducing the number of TNBC cells with a stem-like phenotype.Methods: A magnetic step-by-step cell isolation with antibodies directed against CD133 and/or EpCAM was performed on the TNBC-derived MDA-MB-231 cell line. In the same cell model, PLC-β2 was over-expressed or down-modulated and cell proliferation and invasion capability were evaluated by Real-time cell assays. The surface expression of CD133, EpCAM and CD44 in the different experimental conditions were measured by multi-color flow cytometry immunophenotyping.Results: A CD133+/EpCAM+ sub-population with high proliferation rate and invasion capability is present in the MDA-MB-231 cell line. Over-expression of PLC-β2 in CD133+/EpCAM+ cells reduced the surface expression of both CD133 and EpCAM, as well as proliferation and invasion capability of this cellular subset. On the other hand, the up-modulation of PLC-β2 in the whole MDA-MB-231 cell population reduced the number of cells with a CD44+/CD133+/EpCAM+ stem-like phenotype.Conclusions: Since selective targeting of the cells with the highest aggressive potential may have a great clinical importance for TNBC, the up-modulation of PLC-β2, reducing the number of cells with a stem-like phenotype, may be a promising goal for novel therapies aimed to prevent the progression of aggressive breast tumors. [ABSTRACT FROM AUTHOR]

Background Beyond its possible correlation with stemness of tumor cells, CD133/prominin1 is considered an important marker in breast cancer, since it correlates with tumor size, metastasis and clinical stage of triple-negative breast cancers (TNBC), to date the highest risk breast neoplasia. Methods To study the correlation between the levels of CD133 expression and the biology of breastderived cells, CD133low and CD133high cell subpopulations isolated from triple negative MDA-MB-231 cells were compared in terms of malignant properties and protein expression. Results High expression of CD133 characterizes cells with larger adhesion area, lower proliferation rate and reduced migration speed, indicative of a less undifferentiated phenotype. Conversely, when compared with CD133low cells, CD133high cells show higher invasive capability and increased expression of proteins involved in metastasis and drug-resistance of breast tumors. Among the signalling proteins examined, PLC-β2 expression inversely correlates with the levels of CD133 and has a role in inducing the CD133high cells to CD133low cells conversion, suggesting that, in TNBC cells, the de-regulation of this PLC isoform is responsible of the switch from an early to a mature tumoral phenotype also by reducing the expression of CD133. Conclusions Since CD133 plays a role in determining the invasiveness of CD133high cells, it may constitute an attractive target to reduce the metastatic potential of TNBC. In addition, our data showing that the forced up-regulation of PLC-β2 counteracts the invasiveness of CD133- positive MDA-MB-231 cells might contribute to identify unexplored key steps responsible for the TNBC high malignancy, to be considered for potential therapeutic strategies. [ABSTRACT FROM AUTHOR]

Vav1 is a critical signal transducer for both the development and function of normal hematopoietic cells, in which it regulates the acquisition of maturation-related properties, including adhesion, motility, and phagocytosis. Vav1 is also important for the agonist-induced maturation of acute promyelocytic leukemia (APL)-derived promyelocytes, in which it promotes the acquisition of a mature phenotype by playing multiple functions at both cytoplasmic and nuclear levels. We investigated the possible role of Vav1 in the differentiation of leukemic precursors to monocytes/macrophages. Tumoral promyelocytes in which Vav1 was negatively modulated were induced to differentiate into monocytes/macrophages with phorbol-12-myristate-13-acetate (PMA) and monitored for their maturation-related properties. We found that Vav1 was crucial for the phenotypical differentiation of tumoral myeloid precursors to monocytes/macrophages, in terms of CD11b expression, adhesion capability and cell morphology. Confocal analysis revealed that Vav1 may synergize with actin in modulating nuclear morphology of PMA-treated adherent cells. Our data indicate that, in tumoral promyelocytes, Vav1 is a component of lineage-specific transduction machineries that can be recruited by various differentiating agents. Since Vav1 plays a central role in the completion of the differentiation program of leukemic promyelocytes along diverse hematopoietic lineages, it can be considered a common target for developing new therapeutic strategies for the various subtypes of myeloid leukemias. [ABSTRACT FROM AUTHOR]

Reduced oxygen availability plays a crucial role in malignancy of solid tumors,including breast cancer. Even if the presence of hypoxic areas is common in all breast lesions, no data clearly correlate low oxygenation with the acquisition of malignant features by non-invasive cells, particularly by cells from ductal carcinoma in situ (DCIS), the most frequently diagnosed tumor in women in industrialized countries [1]. We demonstrated that 96 hours of culture under moderate hypoxia is sufficient to induce in DCIS-derived cells motility and epithelial-to-mesenchymal transition (EMT) and to enlarge the number of cells expressing the stem cell marker CD133, indicative of their increased malignant potential. Administration of all-trans retinoic acid (ATRA), a well-known anti-leukemic drug with an anti-tumor role in invasive breast tumor cells [2], supports the epithelial phenotype of DCIS-derived cells cultured under hypoxia and reduces the number of CD133 positive cells, abrogating almost completely the effects of poor oxygenation. In DCIS-derived cells, as in leukemic cells, ATRA up-regulates the β2 isoform of PIPLC (PLC-β2), ectopically expressed in invasive breast tumors in which counteracts the effects of hypoxia on both EMT and CD133 levels [3]. This suggests that the mechanisms triggered by ATRA in non-invasive breast tumor cells cultured under hypoxia may, at least in part, depend on PLC-β2 activity. Overall, we assigned to hypoxia a role in increasing the malignant potential of DCIS-derived cells and identified in ATRA, currently used in treating acute promyelocytic leukemia (APL), an agonist potentially useful in preventing malignant progression of non-invasive breast lesions with hypoxic areas. [ABSTRACT FROM AUTHOR]

Abstract: Erythroid differentiation of human erythroleukemia cell line K562 induced by erythropoietin is a complex process that involves modifications at nuclear level, including nuclear translocation of phosphatidyl-inositol 3-kinase. In this work we show that erythropoietin stimulation of K562 cells can induce nuclear translocation of active Akt, a downstream molecule of the phosphatidyl-inositol 3-kinase signaling pathway. Akt shows a peak of activity in whole cell homogenates at earlier stage when compared to the nucleus, which shows a peak delayed of 10min. Akt increases its intranuclear amount and activity rapidly and transiently in response to EPO. Almost all Akt kinase that translocates to the nucleus shows a marked phosphorylation on serine 473. Nuclear enzyme translocation is blocked by the phosphatidyl-inositol 3-kinase inhibitor Ly294002 or Wortmannin. The specific Akt pharmacological inhibitor VI, VII and VIII that act as blocking enzyme activation inhibited translocation as well, whereas Akt inhibitor IX, that inhibits Akt activity, did not block Akt nuclear translocation. When cells were treated by means of siRNA sequences or with the Akt inhibitors the differentiation process was arrested, thus showing the requirement of the nuclear translocation of the active enzyme to differentiate. These findings strongly suggest that the intranuclear translocation of active Akt kinase represents an important step in the signaling pathway that mediates erythropoietin-induced erythroid differentiation. [Copyright &y& Elsevier]

In this study, we have evaluated the “in vitro” modulatory activity of a series of pyrazolotriazolopyrimidine derivatives (PTP-d) in sensitizing malignant melanoma cells to the chemotherapic drugs: taxol and vindesine. To that end, we have described the impact of chemotherapeutic agents on the cell cycle and on the induction of apoptosis when used alone or in combination with PTP-d. We have demonstrated that four PTP-d reduced chemotherapic drugs ec50 doses of the G2/M accumulation with an average of 1.7-fold for taxol and 9.5-fold for vindesine when challenged on A375 human melanoma cell line. This sensitization activity was also confirmed by analyzing the apoptosis degree induced by the chemotherapic drugs. Interestingly, PTP-d had no effects on the response to cytotoxic agents by skin-derived human keratinocyte cells, NCTC 2544. Therefore, we have investigated the signaling pathway sustaining the sensitizing effect of PTP-d, providing functional evidence that active compounds are able to inhibit multidrug resistance-associated ATP-binding cassette drug transporter. These results suggested that PTP-d hold great promise for the treatment of multidrug resistance in cancers, leading to potential new therapies for melanoma. [Copyright &y& Elsevier]