Tuesday, August 9, 2016

PD-1 expression on tumor-infiltrating T cells does not correlate with antigen-specific response

Patients selection [stratification] and then monitoring for immunotherapy effectiveness is part of precision medicine. In humans, especially, when determination of cancer neo-antigens is not always feasible, clinical diagnostic tests are focused on surrogate markers to tell whether patient has a tumor antigen-specific immune response. More recently, PD-1 has become one of such surrogate markers. However it is not clear whether expression of PD-1 could truly correlate with T cell antigen-specific response.

For example, they showed that OT-I CD8 T cells would express PD-1 irrespective whether tumor expresses or not specific OVA antigen. In contrast, Nur77 (part of TCR signaling) expression correlated with tumor neo-antigen expression. 

This study indicate that diagnostic tests measuring PD-1 expression on tumor-infiltrating T cells may over-estimate tumor antigen-specific immune response and lead to unpredictable outcomes during antibody immunotherapy.

David Usharauli

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