Tumor-related immunity in prostate cancer patients treated with human recombinant granulocyte monocyte-colony...

Granulocyte monocyte-colony stimulating factor (GM-CSF) supports the survival, expansion, and differentiation of lymphoid and myeloid derived dendritic cells (DCs). We hypothesized that systemic therapy with GM-CSF in prostate cancer patients could augment prostate cancer-related immunity and induce clinical response.

Eligible patients were randomly assigned to receive either 125 or 250 microg/m(2) GM-CSF subcutaneously three times a week until clinical progression. Prostate-specific antigen (PSA) T cell precursor frequencies were determined by a flow cytometric method.

We were able to show, for the first time, a statistically significant correlation between pre-treatment PSA level and PSA-specific CD4(+) T cell precursors and a trend between pre-treatment PSA level and PSA-specific CD8(+) T cell precursors (P<0.0001 and P=0.059, respectively).

These results suggest that existent immunity to PSA in prostate cancer patients may be a promising target for future immunotherapeutic approaches to prostate cancer.