Isolation of single cells permits analysis of DNA or RNA from individual cells among heterogeneous populations. This technique is particularly useful in the study of classical Hodgkin's lymphoma (cHL) due to the scarcity of H/RS tumor cells among large numbers of reactive leukocytes. In a previous study, we found a high frequency of dual LMP-1 variant (concurrent presence of deleted and nondeleted variants) in cHL from whole-tissue sections. For the present study, we applied a single-cell isolation technique to determine the LMP-1 oncogene variant in EBV-associated H/RS cells. Five cases of EBV-infected cHL, containing nondeleted (n=1), deleted (n=1) and dual infection (n=3) based on whole-tissue section analysis, were selected for study. Paraffin-embedded tissue sections were stained with antibody to LMP-1 and positively stained H/RS cells isolated using a semiautomated micromanipulator. Each isolated single cell was subjected to PCR for amplification of the LMP-1 gene flanking the 30 bp deletion region and Xho1 restriction site. Cases with either nondeleted variant or the deleted variant showed similar LMP-1 variant expression in isolated single H/RS cells. However, 1 of the 3 cases with dual variants showed only the deleted variant in H/RS cells. The other 2 cases showed mixed patterns of deleted, nondeleted and dual LMP-1 variants in isolated single H/RS cells. All cases showed loss of the Xho1 restriction site, with the exception of the case with nondeleted LMP-1. Results of single-H/RS cell analysis of the Xho1 restriction site concur with those of whole-tissue section amplification. A mixed pattern of LMP-1 variants was observed in isolated H/RS cells, and it is speculated that this is due to the accumulation of mutation and deletion events.
AIMS: To examine the expression of the Bcl-2 family of proteins (Bcl-2, Bcl-x, Bcl-xL and Bax) in classical Hodgkin's lymphoma (cHL) and to correlate the expression of these proteins with proliferation, apoptosis and the presence of Epstein-Barr virus (EBV).
METHODS AND RESULTS: Expression of the Bcl-2 family of proteins was detected by immunohistochemistry, proliferation was determined by Ki67 labelling and apoptosis by TUNEL in-situ hybridization. EBV was detected by Epstein-Barr virus early RNA (EBER) in-situ hybridization. Expression of Bcl-2, Bcl-x, Bcl-xL and Bax was detected in the Hodgkin/Reed-Sternberg (H/RS) cells in 43.7% (27/62), 87.5% (56/64), 67.2% (41/61) and 74.6% (47/63) of the cHL cases, respectively. EBER was detected in 53% (35/66) of the cases, whereas Ki67 was observed in 86.7% (52/60) of the cases. Apoptotic H/RS cells were observed infrequently, and only 43.2% (11/26) of the cases showed an apoptotic index of > or = 10% in the H/RS cells. A statistically significant inverse relationship was observed between the expression of Bcl-2 and the presence of EBV (P = 0.003). Bcl-xL showed an inverse correlation with apoptosis in the H/RS cells (P = 0.004).
CONCLUSIONS: The higher Bcl-xL expression (67.2%) compared with Bcl-2 expression (43.5%) observed in cHL as well as the statistically significant inverse relationship between Bcl-xL and apoptosis suggests that Bcl-xL plays an important role in the survival of H/RS cells. Expression of Bax may be neutralized by other anti-apoptotic members of the family such as Bcl-2 and/or Bcl-xL.