Nuclear calcium signaling: a cell within a cell

Calcium (Ca2+) is a versatile second messenger that regulates a wide range of cellular functions. Although it is not established how a single second messenger coordinates diverse effects within a cell, there is increasing evidence that the spatial patterns of Ca2+ signals may determine their specificity. Ca2+ signaling patterns can vary in different regions of the cell and Ca2+ signals in nuclear and cytoplasmic compartments have been reported to occur independently. No general paradigm has been established yet to explain whether, how, or when Ca2+ signals are initiated within the nucleus or their function. Here we highlight that receptor tyrosine kinases rapidly translocate to the nucleus. Ca2+ signals that are induced by growth factors result from phosphatidylinositol 4,5-bisphosphate hydrolysis and inositol 1,4,5-trisphosphate formation within the nucleus rather than within the cytoplasm. This novel signaling mechanism may be responsible for growth factor effects on cell proliferation.

In vitro response of the human breast cancer cell line MDAMB-231 and human peripheral blood mononuclear cells exposed to 60Co at single fraction

Radiotherapy using gamma rays is a common modality of breast cancer treatment. The aim of this research is to investigate the biological response of the human breast cancer cell line MDAMB-231 and human peripheral blood mononuclear cells (PBMC) exposed in vitro to 60 Co irradiation at a single fraction of 10 Gy, 25 Gy and 50 Gy doses at 136,4 cGy.min-1 rate. Cells were irradiated at room temperature by the Theratron 80 radiotherapy system. Biological response was evaluated through cellular viability using MTT assay and nucleus damages visualized by Propidium Iodide assay and electrophoresis agarose gel after gamma irradiation. Nucleus damages induced by 60Co irradiation were compared to damage caused by cell exposure to 10 percent methanol. The 50 Gy dose of irradiation did not stimulate nuclus damages at the same level as that affected by 10 percent methanol induction in the MDAMB-231. Further studies are necessary to understand these mechanisms in the MDAMB-231 human breast carcinoma cell line.

Radioterapia utilizando radiação gama é uma modalidade comum no tratamento do câncer de mama. A proposta deste estudo é investigar a resposta biológica in vitro da linhagem celular MDAMB-231 de câncer de mama humano e células do sangue periférico humano (PBMC) expostas à irradiação pelo Co60 em frações simples de 10Gy, 25Gy e 50Gy e 136,4cGy min-1 rate. As células foram irradiadas a temperatura ambiente usando o equipamento de radioterapia Theratron 80 radiotherapy system. A resposta biológica, após irradiação gama, foi avaliada através do ensaio do MTT para viabilidade celular e o do ensaio com Iodeto de Propídio para visualização do dano nuclear, além da eletroforese em gel de agarose. Os danos nucleares induzidos pelo Co60 foram comparados aos danos causados pela exposição das células à solução de metanol a 10 por cento. Nós observamos que a dose de 50Gy não estimulou a mesma quantidade de danos nucleares que a solução de metanol a 10 por cento nas células MDAMB-231. Maiores estudos são necessários para a compreensão destes mecanismos nas células de câncer de mama humano MDAMB-231.