Relationship between the amounts of EBV‐DNA and ebna per cell, clonability and tumorigenicity in two EBV‐negative lymphoma lines and their EBV‐converted sublines

Abstract

The effect of EBV-conversion of two EBV-negative lymphoma lines (Ramos and BJAB) on agarose clonability and tumorigenicity in nude mice was explored. The cloning frequency was increased in all 9 sublines investigated, between 1.1 and 4.9 times compared to the original "parental" lines. Tumorigenicity was increased in one out of 2 BJAB-derived, EBV-positive lines and in 3 of 6 Ramos-derived lines, while it was decreased in 3 others. A strong positive correlation between the number of genomes/cell and the amount of EBNA/cell was detected, and in 7 of 9 converted lines the cloning frequency also correlated to the number of EBV genomes. On the other hand, no relation was established between the number of EBV-genomes/cell, the amount of EBNA/cell and tumorigenicity.

Overexpression of an activated REL mutant enhances the transformed state of the human B-lymphoma BJAB cell line and alters its gene expression profile

“…Second, BJAB cells have a GCB mRNA profile (Ngo et al ., 2006), which is correlated with a better clinical outcome in DLBCL patients (Rosenwald et al ., 2002; Shipp et al ., 2002), suggesting that BJAB cells are not as “transformed” as some other human B-cell lines. Third, in soft agar and tumor-forming assays similar to those we have conducted here, BJAB cells have been shown to be susceptible to oncogenic effects of other factors, including the Epstein-Barr virus (EBV) LMP1 protein (Enberg et al ., 1983; Wennborg et al ., 1987), EBV small RNAs (Yamamoto et al ., 2000) and the AP12-MALT1 fusion protein from MALT lymphomas (Ho et al, 2005). Interestingly, LMP1 and AP12-MALT1 are both inducers of NF-κB (Hammarskjold et al , 1992; Lucas et al ., 2007) and both can increase the resistance of BJAB cells to inducers of apoptosis (Stoffel et al ., 2004; Ho et al ., 2005; Lucas et al ., 2007).…”

Reversion of tumorigenicity and decreased agarose clonability after EBV conversion of an igh/myc translocation‐carrying be line

“…Later infection with EBV would add an additional proliferation stimulus (Lenoir and Bornkamm, 1987). This is supported by the finding that EBV conversion of an EBV-negative but weakly malignant B-cell lymphoma line, BJAB, increased its agarose clonability and tumorigenicity (Ernberg et al, 1983). EBVnegative and -positive BLs that carry the myclIg translocation have similar tumorigenic potentials, as a rule (Gurtsevitch et al, 1988).…”

“…The BLs in group I resemble freshly explanted BL cells, whereas group-I11 BLs are closest to the LCL phenotype. The assumption that the phenotypic drift of the BLEf lines is due to the presence of the virus was confirmed by the induction of analogous phenotypic changes in some BLE-lines by EBV conversion in vitro (Klein et al, 1983~;Rowe et al, 1986;.…”

Differential cytotoxicity of tumour promoter TPA for EBV‐negative human lymphoma cell lines and their EBV‐converted sublines

“…EBV-converted BJAB and Ramos sublines have been shown to differ from the original EBVnegative lines by several properties, such as decreased dependence on medium renewal and serum concentration Klein, 1976, 1977), growth in agarose (Steinitz and Klein, 1977;Montagnier and Gruest, 1979;Ernberg et al, 1983) The ability of lymphoma cells to undergo changes in their transformation as well as differentiation stage upon conversion by EBV led us to investigate the effect of a tumour promoter in this system. Tumour promoters have been shown to enhance in vitro transformation by chemicals and viruses and to either trigger or inhibit cell differentiation (Sivak, 1979).…”