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3. The Ability to Generate Senescent Progeny as a Mechanism Underlying Breast Cancer Cell Heterogeneity

Author

Mumcuoglu, Mine, primary, Bagislar, Sevgi, additional, Yuzugullu, Haluk, additional, Alotaibi, Hani, additional, Senturk, Serif, additional, Telkoparan, Pelin, additional, Gur-Dedeoglu, Bala, additional, Cingoz, Burcu, additional, Bozkurt, Betul, additional, Tazebay, Uygar H., additional, Yulug, Isik G., additional, Akcali, K. Can, additional, and Ozturk, Mehmet, additional

Published
2010
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4. Ras Protein Ailesi: Hücresel İşlevi, Moleküler Kontrolü, Onkogenezdeki Rolü.

Author

Telkoparan, Pelin and Tazebay, Uygar H.

Subjects
*PROTEINS, *BIOMOLECULES, *G proteins, *MEMBRANE proteins, *RAS proteins
Abstract

Small GTPases belonging to Ras family of proteins have key roles in regulating nearly every aspect of cell biology, such as cell division, cellular differentiation, vesicular transport and localization of cargo proteins, cell morphology, and gene expression. Depending on the extra- cellular signals, Ras family members oscillate between GTP-bound (active) and GDP-bound (inactive) conformations, and in the active form they interact with downstream effector molecules, leading to conformational changes in those effectors. As a result, extracellular signals trigger cellular responses, by means of initiation of a phosphorylation cascade. Functional cycles of Ras family of proteins include interactions with GTPase Activating Proteins (GAPs), and with Guanine Nucleotide Exchange Factors (GEFs) that regulate these small GTPases. GAP proteins activate intrinsic GTP hydrolysis activities of these small G-proteins, and convert active Ras-GTP to inactive Ras-GTP. On the other hand, GEF proteins interact with inactivated Ras-GDP molecules, and convert those inactivated molecules back to activated Ras-GTP, by triggering dissociation of GDP, and reassociation of Ras with GTP which is found at higher concentrations as compared to GDP in the cell cytoplasm. It is well known that mutations in Ras that block these molecules in GTP-bound forms by impairing GTP hydrolysis activity could trigger an uncontrolled and aberrant cellular proliferation. This type of mutations in Ras genes causing uncontrolled activation of the protein, are found in approximately 30% of human cancers overall, and they indicate the significance of mutations in genes encoding Ras family members in cellular proliferation related to de novo oncogenesis in human. [ABSTRACT FROM AUTHOR]

Published
2011

5. The ability to generate senescent progeny as a mechanism underlying breast cancer cell heterogeneity

Author

Hani Alotaibi, Betül Bozkurt, Bala Gur-Dedeoglu, Mehmet Ozturk, Mine Mumcuoglu, Isik G. Yulug, Pelin Telkoparan, Uygar H. Tazebay, Burcu Cingoz, Sevgi Bagislar, Haluk Yuzugullu, K. Can Akcali, Serif Senturk, Mumcuoğlu, Mine, Bağışlar, Sevgi, Yüzügüllü, Haluk, Alotaibi, Hani, Şentürk, Şerif, Telkoparan, Pelin, Gür-Dedeoğlu, Bala, Cingöz, Burcu, Tazebay, Uygar H., Yuluğ, Işık G., Akçalı, Kamil Can, and Öztürk, Mehmet

Subjects
CD24 antigen, Pathology, medicine.medical_specialty, Cellular differentiation, Cell, Blotting, Western, Cell Biology/Cell Growth and Division, Estrogen receptor, lcsh:Medicine, Breast Neoplasms, Biology, Cyclin dependent kinase inhibitor 1, Cell Line, Tumor, Receptors, medicine, Cluster Analysis, Humans, Progenitor cell, skin and connective tissue diseases, lcsh:Science, Hermes antigen, Multidisciplinary, CD24, CD44, lcsh:R, Myoepithelial cell, Cell Biology/Cellular Death and Stress Responses, Immunohistochemistry, Tamoxifen, medicine.anatomical_structure, Receptors, Estrogen, Cell culture, Oncology/Breast Cancer, Cancer research, biology.protein, Female, lcsh:Q, Research Article
Abstract

BACKGROUND: Breast cancer is a remarkably heterogeneous disease. Luminal, basal-like, "normal-like", and ERBB2+ subgroups were identified and were shown to have different prognoses. The mechanisms underlying this heterogeneity are poorly understood. In our study, we explored the role of cellular differentiation and senescence as a potential cause of heterogeneity. METHODOLOGY/PRINCIPAL FINDINGS: A panel of breast cancer cell lines, isogenic clones, and breast tumors were used. Based on their ability to generate senescent progeny under low-density clonogenic conditions, we classified breast cancer cell lines as senescent cell progenitor (SCP) and immortal cell progenitor (ICP) subtypes. All SCP cell lines expressed estrogen receptor (ER). Loss of ER expression combined with the accumulation of p21(Cip1) correlated with senescence in these cell lines. p21(Cip1) knockdown, estrogen-mediated ER activation or ectopic ER overexpression protected cells against senescence. In contrast, tamoxifen triggered a robust senescence response. As ER expression has been linked to luminal differentiation, we compared the differentiation status of SCP and ICP cell lines using stem/progenitor, luminal, and myoepithelial markers. The SCP cells produced CD24+ or ER+ luminal-like and ASMA+ myoepithelial-like progeny, in addition to CD44+ stem/progenitor-like cells. In contrast, ICP cell lines acted as differentiation-defective stem/progenitor cells. Some ICP cell lines generated only CD44+/CD24-/ER-/ASMA- progenitor/stem-like cells, and others also produced CD24+/ER- luminal-like, but not ASMA+ myoepithelial-like cells. Furthermore, gene expression profiles clustered SCP cell lines with luminal A and "normal-like" tumors, and ICP cell lines with luminal B and basal-like tumors. The ICP cells displayed higher tumorigenicity in immunodeficient mice. CONCLUSIONS/SIGNIFICANCE: Luminal A and "normal-like" breast cancer cell lines were able to generate luminal-like and myoepithelial-like progeny undergoing senescence arrest. In contrast, luminal B/basal-like cell lines acted as stem/progenitor cells with defective differentiation capacities. Our findings suggest that the malignancy of breast tumors is directly correlated with stem/progenitor phenotypes and poor differentiation potential.

Published
2010

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