Differential Ca2+ responses and store operated Ca2+ entry in primary cells from human brain tumors

Abstract

Brain tumors comprise a large series of tumor cancer from benign to highly malignant gliomas and metastases from primary tumors outside the brain. Intracellular Ca2+ homeostasis is involved in a large series of cell functions including cell proliferation, migration, and cell death. Store-operated Ca2+ entry (SOCE), the most important Ca2+ entry pathway in non-excitable cells, is involved in cell proliferation and migration and enhanced in tumor cells from breast cancer, colon cancer and cell lines derived from glioblastoma but there are almost no studies in human primary glioblastoma cells or other brain tumors. We have developed a single procedure to obtain primary cells from a large series (n = 49) of human brain tumors including schwannomas, meningiomas, oligodendrogliomas, astrocytomas, glioblastomas and brain metastases from ovary, breast and lung. Cells were characterized by immunofluorescence and subjected to Ca2+ imaging to investigate resting intracellular Ca2+ levels, Ca2+ responses to physiological agonists as well as voltage-operated Ca2+ entry and SOCE. We found significant differences in resting intracellular Ca2+ and Ca2+ responses to plasma membrane depolarization and ATP among the different tumor cells. Only malignant tumor cells, displayed Ca2+ responses to ATP. SOCE is significantly increased in malignant gliomas whereas voltage-gated Ca2+ entry is decreased. In addition, SOCE is significantly larger in high grade gliomas than in low grade gliomas suggesting that SOCE increases with glioma progression. These data may provide new insights on the role of intracellular Ca2+ and purinergic signalling in brain tumors.