Upregulation of inhibitory signaling receptor programmed death marker-1 (PD-1) in disease evolution from cutaneous lymphoid dyscrasias to mycosis fungoides and Sezary's syndrome.

BACKGROUND

Negative immunoregulatory checkpoints impede effective immune responses to tumor and reduce the action of anticancer agents. One such example is programmed death marker-1 (PD-1), an inhibitory signaling receptor expressed on activated and regulatory T-cells. PD-1 expression was reported in a few reports, but the expression profile of PD-1 and mycosis fungoides (MF) remains largely to be characterized.

DESIGN

In this study, skin biopsies from 42 prelymphomatous T-cell dyscrasias (CLD), 9 Sezary's syndrome (SS), 103 MF, and 20 CD30+ lymphoproliferative diseases (LPD) were examined for PD-1 expression using immunohistochemistry.

RESULTS

PD-1 staining was observed amidst many neoplastic T-cells in 6/9(66.7%) and 62/103 (60.2%) cases of SS and MF respectively, while only 6/42 (14.3%) cases of CLD and 0/20 (0%) cases of CD30+ LPD (P<0.001). Three cases are from same patients representing different stages of disease evolution from CLD to MF and SS with a corresponding enrichment of PD-1 positivity. In all cases there was variable staining of PD-1 amidst macrophages. There was no correlation with disease progression among MF cases. Twenty cases of CD30+ LPD did not show any PD-1 positivity.

CONCLUSION

PD-1 seems to correlate with disease progression in epitheliotropic T cell dyscrasias ranging from minimal staining in prelymphomatous dyscrasias to significant staining in MF, likely reflecting the effects of PD-1 on inhibiting tumor surveillance regulatory T cell populations. PD-1 was consistently expressed in MF while it was consistently negative in primary CD30+ LPD, suggesting the possibility of using PD-1 as a means of distinguishing CD30+ MF from primary cutaneous ALCL.