Publicação
Is ARPC5 required for maintaining the equilibrium between Cancer Stem Cells and non-Stem Cancer Cells?
| Resumo: | Nowadays, breast cancer is still a predominant cause of death in women despite all the available therapies. The malignancy, aggressiveness, and recurrence of breast cancer are believed to be caused by the presence of a specific tumorigenic cell subpopulation, termed Cancer Stem Cell (CSC) or tumor-initiating cell population. The cells of this cell population have been isolated from diverse breast tumors and from established breast cancer cell lines. They exist as a minority population within tumors and are defined by their ability to self-renew under non-differentiation conditions, to resist standard chemotherapeutic drugs and radiotherapy, to differentiate into non-stem cancer cells (NSCCs) and to recapitulate the tumor of origin both morphologically and phenotypically upon injection in immune-deficient mice. Conversely, NSCCs can convert into CSCs under certain conditions, indicating that CSCs and NSCCs do not exist in static states but instead are highly plastic, being able to interconvert between states. However, the origin of cells with stemness properties, as well as their relationships to NSCCs, is poorly understood. CSCs and NSCCs exhibit distinct cell shape, mechanic, adhesion and mobility properties. All these processes are underlined by the actin cytoskeleton, which organizes into distinct actin filaments (F-actin) subtypes to perform these different functions. Consistent with a role for the actin cytoskeleton in promoting CSCs properties, reducing actin-myosin contractility strongly confers cancer stemness features. F-actin assembly, disassembly, and organization into distinct subtypes are controlled by a plethora of actin-binding proteins (ABPs). Among these ABPs, ARPC5 and ARPC5L, both encode for the ARPC5 subunit of the Arp2/3 complex. This complex is composed of seven subunits, which catalyzes the polymerization of new "daughter" actin filaments from the side of an existing filament, forming branched actin networks. Strikingly, ARPC5 and ARPC5L appear to have antagonistic effects on F-actin assembly. Using the MCF10A cell line with conditional activation of the Src oncoprotein (MCF10A-ER-Src), which recapitulates the multistep development of breast cancer, the Actin Dynamic´s lab observed that ARPC5L re-localizes to F-actin-rich structures that bridge cells between each other. The assembly of these bridges is concomitant with the differentiation of a pool of CSCs. In this work, I analyzed the composition and dynamical assembly of F-actin bridges during the transformation of the MCF10A-ER-Src cells and tested the hypothesis that the F-actin bridges, assembled by ARPC5 affect the acquisition of CSC properties. My results show that F-actin bridges assemble between 12 and 24 hours after Src induction and contain both ARPC5 isoforms – ARPC5 and ARPC5L. Furthermore, my results show that F-actin bridges also contain tropomyosin 1.6/1.7, which could indicate a role for F-actin bridges in regulating CSCs since Tpm 1.7 recruits fascin that is critical for CSC pool maintenance. Lastly, knocking down ARPC5 appears to decrease the mammosphere forming efficiency of cells with conditional Src activation, suggesting that ARPC5 could promote the acquisition of CSC properties. Altogether, my data suggest that ARPC5 has an important function in tumorigenesis, although further studies are needed. |
|---|---|
| Autores principais: | Gomes, Maria Clara Barreto Carromeu |
| Assunto: | Cancro da mama F-actina Células cancerígenas estaminais Transformação celular ARPC5 ARPC5L Teses de mestrado - 2018 |
| Ano: | 2018 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade de Lisboa |
| Idioma: | inglês |
| Origem: | Repositório da Universidade de Lisboa |
| Resumo: | Nowadays, breast cancer is still a predominant cause of death in women despite all the available therapies. The malignancy, aggressiveness, and recurrence of breast cancer are believed to be caused by the presence of a specific tumorigenic cell subpopulation, termed Cancer Stem Cell (CSC) or tumor-initiating cell population. The cells of this cell population have been isolated from diverse breast tumors and from established breast cancer cell lines. They exist as a minority population within tumors and are defined by their ability to self-renew under non-differentiation conditions, to resist standard chemotherapeutic drugs and radiotherapy, to differentiate into non-stem cancer cells (NSCCs) and to recapitulate the tumor of origin both morphologically and phenotypically upon injection in immune-deficient mice. Conversely, NSCCs can convert into CSCs under certain conditions, indicating that CSCs and NSCCs do not exist in static states but instead are highly plastic, being able to interconvert between states. However, the origin of cells with stemness properties, as well as their relationships to NSCCs, is poorly understood. CSCs and NSCCs exhibit distinct cell shape, mechanic, adhesion and mobility properties. All these processes are underlined by the actin cytoskeleton, which organizes into distinct actin filaments (F-actin) subtypes to perform these different functions. Consistent with a role for the actin cytoskeleton in promoting CSCs properties, reducing actin-myosin contractility strongly confers cancer stemness features. F-actin assembly, disassembly, and organization into distinct subtypes are controlled by a plethora of actin-binding proteins (ABPs). Among these ABPs, ARPC5 and ARPC5L, both encode for the ARPC5 subunit of the Arp2/3 complex. This complex is composed of seven subunits, which catalyzes the polymerization of new "daughter" actin filaments from the side of an existing filament, forming branched actin networks. Strikingly, ARPC5 and ARPC5L appear to have antagonistic effects on F-actin assembly. Using the MCF10A cell line with conditional activation of the Src oncoprotein (MCF10A-ER-Src), which recapitulates the multistep development of breast cancer, the Actin Dynamic´s lab observed that ARPC5L re-localizes to F-actin-rich structures that bridge cells between each other. The assembly of these bridges is concomitant with the differentiation of a pool of CSCs. In this work, I analyzed the composition and dynamical assembly of F-actin bridges during the transformation of the MCF10A-ER-Src cells and tested the hypothesis that the F-actin bridges, assembled by ARPC5 affect the acquisition of CSC properties. My results show that F-actin bridges assemble between 12 and 24 hours after Src induction and contain both ARPC5 isoforms – ARPC5 and ARPC5L. Furthermore, my results show that F-actin bridges also contain tropomyosin 1.6/1.7, which could indicate a role for F-actin bridges in regulating CSCs since Tpm 1.7 recruits fascin that is critical for CSC pool maintenance. Lastly, knocking down ARPC5 appears to decrease the mammosphere forming efficiency of cells with conditional Src activation, suggesting that ARPC5 could promote the acquisition of CSC properties. Altogether, my data suggest that ARPC5 has an important function in tumorigenesis, although further studies are needed. |
|---|