Decreased calcium dependence of lymphoblastoid cell lines compared with Burkitt lymphoma cell lines

The extracellular calcium level required for proliferation was compared in B lymphoid cell lines from various sources by determining the calcium concentration at which long-term proliferation was inhibited by 50% (CaPD50). Fourteen Burkitt lymphoma (BL) lines had a mean CaPD50 of 44 +/- 28 microM whereas 45 lymphoblastoid cell lines (LCLs) obtained by in vitro transformation of B lymphocytes with Epstein-Barr virus (EBV) had a mean CaPD50 of 3.6 +/- 1.8 microM. This difference applied also to autologous BL lines and LCLs established from the same patient. The decreased calcium requirement of virally-transformed compared with tumour-derived cell lines therefore appears to be a universal phenomenon in mammalian cells. Within the BL group, no correlation was found between the calcium requirement for proliferation and presence or absence of the EBV genome. Arrest of BL lines and LCLs occurred in the G1 phase of the cell cycle and was readily reversed by addition of calcium to the medium. One anomalous LCL was found which showed a high CaPD50 (43 +/- 6 microM) and accumulated in both G1 and G2. These results, in combination with a previous study of EBV transformation in vitro, indicate that the calcium dependence of B lymphocytes generally decreases in the following order: normal cells greater than BL cells = early stage transformation greater than LCL. The 2 transformed phenotypes thus distinguished in human lymphoid cells may offer unique opportunities for defining the status and expression of EBV in vitro and in vivo.