An Immunohistochemical Study of PRAME Expression in Non-hodgkin’s Lymphoma

Aim: Preferentially expressed antigen of melanoma (PRAME) is a cancer-testis antigen with very low/no expression in normal tissues. PRAME is an important target for tumor immunotherapy. Prognostic and in some tumors predictive importance of this expression have been shown in some solid tumors. The aim of this study is to detect the prognostic and/or predictive value of PRAME expression in non-Hodgkin’s lymphomas (NHL).

Study Design: Retrospective clinico-pathological study.

Methodology: PRAME expression was determined by immunohistochemistry (IHC) in 62 cases with NHL. However statistical analysis was performed in 54 cases [33 with diffuse large B cell lymphoma (DLBCL) and 21 with indolent lymphoma (IL)] due to the low number of the other subtypes.

Results: PRAME expression was detected in 20 of the total 62 cases (32.3%). Nine of 33 cases with DLBCL, 7 of 21 cases with IL, 4 of 6 cases with T-NHL and both of the 2 cases of mantle cell lymphoma (MCL). Clinical variables including gender, stage, age, extranodal involvement and response to chemotherapy were not different in PRAME (+) and PRAME (-) cases. However PRAME (+) cases had longer PFS and OS than the PRAME (-) cases, however, no significant difference was found between groups in total. Furthermore, lymphoma subtype data indicated that while PRAME positivity was significantly associated with longer OS in cases with IL (p=0.049) but not in DLBCL cases (p=0.881). Multivariate Cox regression analysis showed that while response to chemotherapy was an independent risk factor, PRAME and NHL subtype were found not to be significant independent risk factors associated with the OS rate.

Conclusion: PRAME expression was found in one third of the cases with NHL and there was no difference in PRAME expression in indolent lymphomas and DLBCL. Although we did not find the prognostic importance of PRAME with NHL overall, lymphoma subtype data indicated that PRAME positivity was associated with OS. This may be due to the relatively low number of the cases and also lack of comparison with RT-PCR which is the most frequently used method in detection of PRAME expression.