Figure 2

Discrepancy between PRDM1α mRNA and protein expression in extranodal NK/T-cell lymphoma, nasal type (EN-NK/T-NT). (A) The relative levels of PRDM1α mRNA by qRT-PCR and the corresponding PRDM1 protein by immunohistochemistry (IHC) were analysed in 16 EN-NK/T-NT cases, one plasma cell myeloma, and one tonsil case. Case #1 is plasma cell myeloma. Case #2 is tonsil, and cases #3 to #18 are 16 EN-NK/T-NT cases. Levels of PRDM1α mRNA in the tonsil and EN-NK/T-NT cases were estimated relative to that in plasma cell myeloma (arbitrarily set as 100%), which showed strong expression of PRDM1 protein. The data of PRDM1α mRNA by qRT-PCR are presented as mean ± SE of 3 independent experiments. Expression of PRDM1 protein in formalin-fixed paraffin-embedded sections of EN-NK/T-NT specimens, plasma cell myeloma, and one tonsil case was determined by immunostaining and assessed by the percentage of PRDM1 positive cells. Of 16 EN-NK/T-NT cases, 9 cases (#3, 6, 7, 8, 10, 11, 14, 15, and 16) showed high level of PRDM1α mRNA relative to plasma cell myeloma by qRT-PCR but low or absent percentage of PRDM1 protein positive tumor cells by IHC. (B) PRDM1α mRNA was determined by qRT-PCR in NK/T-cell lymphoma cell lines YT, NK92, and NKL, and the human chronic myelogenous leukaemia cell line K562 (mean ± SE of 3 independent experiments). The level of PRDM1α transcript was assessed relative to that in YT cells (arbitrarily considered as 100%). PRDM1α mRNA levels in NK92, NKL, and K562 cells were 15.0%, 73.0%, and 40.1% of those in YT cells, respectively. (C) The expression of PRDM1α protein was detected in cell lines by western blot. The density of PRDM1α in YT cells was set as 100%, and the levels in NK92, NKL, and K562 cells were calculated as 5.0%, 6.0%, and 9.3% of YT cells, respectively.