ALEXANDRE FERREIRA RAMOS
Projetos de Pesquisa
Unidades Organizacionais
SIN-86, EACH - Docente
LIM/24 - Laboratório de Oncologia Experimental, Hospital das Clínicas, Faculdade de Medicina - Líder
LIM/26 - Laboratório de Pesquisa em Cirurgia Experimental, Hospital das Clínicas, Faculdade de Medicina
LIM/24 - Laboratório de Oncologia Experimental, Hospital das Clínicas, Faculdade de Medicina - Líder
LIM/26 - Laboratório de Pesquisa em Cirurgia Experimental, Hospital das Clínicas, Faculdade de Medicina
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Resultados de Busca
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conferenceObject Stochastic model of contact inhibition and the proliferation of melanoma in situ.(2018) MORAIS, Mauro Cesar C.; STUHL, Izabella; SABINO, Alan U.; LAUTENSCHLAGER, Willian W.; QUEIROGA, Alexandre S.; TORTELLI JR., Tharcisio C.; CHAMMAS, Roger; SUHOV, Yuri; RAMOS, Alexandre F.- Stochastic model of contact inhibition and the proliferation of melanoma in situ(2017) MORAIS, Mauro Cesar Cafundo; STUHL, Izabella; SABINO, Alan U.; LAUTENSCHLAGER, Willian W.; QUEIROGA, Alexandre S.; TORTELLI JR., Tharcisio Citrangulo; CHAMMAS, Roger; SUHOV, Yuri; RAMOS, Alexandre F.Contact inhibition is a central feature orchestrating cell proliferation in culture experiments; its loss is associated with malignant transformation and tumorigenesis. We performed a co-culture experiment with human metastatic melanoma cell line (SKMEL-147) and immortalized keratinocyte cells (HaCaT). After 8 days a spatial pattern was detected, characterized by the formation of clusters of melanoma cells surrounded by keratinocytes constraining their proliferation. In addition, we observed that the proportion of melanoma cells within the total population has increased. To explain our results we propose a spatial stochastic model (following a philosophy of the Widom-Rowlinson model from Statistical Physics and Molecular Chemistry) which considers cell proliferation, death, migration, and cell-to-cell interaction through contact inhibition. Our numerical simulations demonstrate that loss of contact inhibition is a sufficient mechanism, appropriate for an explanation of the increase in the proportion of tumor cells and generation of spatial patterns established in the conducted experiments.
- G(D3) ganglioside-enriched extracellular vesicles stimulate melanocyte migration(2019) OTAKE, Andreia Hanada; SAITO, Renata de Freitas; DUARTE, Ana Paula Marques; RAMOS, Alexandre Ferreira; CHAMMAS, RogerMelanomas often accumulate gangliosides, sialic acid-containing glycosphingolipids found in the outer leaflet of plasma membranes, as disialoganglioside G(D3) and its derivatives. Here, we have transfected the G(D3) synthase gene (ST8Sia I) in a normal melanocyte cell line in order to evaluate changes in the biological behavior of non-transformed cells. G(D3) -synthase expressing cells converted G(M3) into G(D3) and accumulated both G(D3) and its acetylated form, 9-O-acetyl-G(D3). Melanocytes were rendered more migratory on laminin-1 surfaces. Cell migration studies using the different transfectants, either treated or not with the glucosylceramide synthase inhibitor D-1-threo-1-phenyl-2-palmitoylamino-3-pyrrolidino-l-propanol (PPPP), allowed us to show that while G(M3) is a negative regulator of melanocyte migration, G(D3) increases it. We showed that gangliosides were shed to the matrix by migrating cells and that GD3 synthase transfected cells shed extracellular vesicles (EVs) enriched in G(D3). EVs enriched in G(D3) stimulated cell migration of G(D3) negative cells, as observed in time lapse microscopy studies. Otherwise, EVs shed by G(M3) (+ve)G(D3)(-ve) cells impaired migration and diminished cell velocity in cells overexpressing G(D3). The balance of antimigratory G(M3) and promigratory G(D3) gangliosides in melanocytes could be altered not only by the overexpression of enzymes such as ST8Sia I, but also by the horizontal transfer of ganglioside enriched extracellular vesicles. This study highlights that extracellular vesicles transfer biological information also through their membrane components, which include a variety of glycosphingolipids remodeled in disease states such as cancer.
conferenceObject GD3 ganglioside-enriched extracellular vesicles stimulate melanocyte migration(2018) OTAKE, Andreia H.; DUARTE, Ana Paula M.; SAITO, Renata de Freitas; RAMOS, Alexandre F.; CHAMMAS, Roger