吉野 正

It has been reported that Epstein-Barr virus (EBV) resides in resting B cells in vivo. However, an ideal in vitro system for studying EBV latent infection in vivo has not yet been established. In this study, a mantle cell lymphoma line, SP53, was successfully infected with a recombinant EBV containing a neomycin-resistant gene. The EBV-carrying SP53 cells were obtained by selection using G418. They expressed EBER-1, EBNAs, and LMP1; this expression pattern of the EBV genes was similar to that in a lymphoblastoid cell line (LCL). However, proliferation assay showed that the EBV-carrying SP53 cells have a doubling time of 73 h, compared with 57 h of SP53 cells. Transplantation of 10(8) SP53 cells to nude mice formed tumors in 4 of 10 mice inoculated, but the EBV-carrying SP53 cells did not. Unexpectedly, EBV infection reduced the proliferation and tumorigenicity of SP53 cells. However, the EBV-carrying SP53 cells showed higher resistance to apoptosis induced by serum starvation than did the SP53 cells. The inhibition of proliferation and the resistance to apoptosis induced in SP53 cells by EBV infection indicate that this cell line might to some extent provide a model of in vivo EBV reservoir cells.

A cell line of human lung large cell carcinoma (LCC) was established directly from the metastatic skin tumor tissue. The clinical course of the patient who carried this carcinoma was peculiar; generalized lymphadenopathy, histologically resembling Hodgkin's disease, was found as the first clinical symptom. The lung tumor was not discovered until the time of autopsy. This cell line (KaMi) grew adherent to culture vessels with the population doubling time of 20.6h, formed colonies in soft agars with efficiency of 22.6%, and formed tumors in athymic nude mice. The authenticity of KaMi was confirmed by chromosomal analysis and isoenzyme patterns. KaMi cells bore a strong resemblance to the original tumor cells which were composed of small spindle cells, large polygonal cells, and multinucleated giant cells. Immunohistochemically, KaMi cells showed a weak tendency to differentiate to squamous cells, and these immunohistochemical reactivities were almost compatible to those of the original tumor cells, but ultrastructurally, KaMi cells were more immature than the original ones. Treatment with several reagents could not augment a differentiation of KaMi cells. Cytokeratin profiles showed a tendency of squamous cell differentiation. KaMi cells may aid in elucidating the pathogenesis and biology of LCC and its relationship to other lung tumors.

Southern blot hybridization was used to detect the rearrangement and amplification of five proto-oncogenes (bcl-2, bcl-1, c-myc, c-myb and c-Ha-ras) and one tumor suppressor gene (RB-1) in 55 Japanese patients with non-Hodgkin's lymphoma; 16 with T-cell lymphomas and 39 with B-cell lymphomas (7 follicular and 32 diffuse lymphomas). Genetic abnormalities of the proto-oncogenes were detected in 7 of the 55 (13%). Genetic abnormalities of bcl-2 plus other genes were detected in 5 of 7 cases of follicular lymphoma (71%), rearrangements of bcl-2 and c-myc, rearrangement of bcl-2 and amplification of c-myb. Genetic abnormalities were observed in only three cases of diffuse lymphoma. In each of 3 cases of B-cell lymphoma, one of the genes, blc-2 mbr, bcl-2 mcr and c-myc, was rearranged respectively. The incidence of genetic abnormalities in diffuse lymphomas (6.3%) was lower than that in follicular lymphomas. None of diffuse lymphomas had double oncogene abnormality. No abnormalities were found in RB-1, bcl-1, and Ha-ras. These findings suggest that follicular lymphomas are associated with some abnormalities of oncogenes not restricted to bcl-2 that facilitate growth which may be associated with their clinical features.