The effects of gemcitabine and capecitabine combination chemotherapy and of low-dose adjuvant GM-CSF on the levels of myeloid-derived suppressor cells in patients with advanced pancreatic cancer

Abstract

In pre-clinical models, the only two chemotherapy drugs which have been demonstrated to directly reduce the number of myeloid-derived suppressor cells (MDSCs) are gemcitabine and 5-fluorouracil. Here we analyze the dynamics of MDSCs, phenotyped as Lin-DR-CD11b+, in patients with advanced pancreatic cancer receiving the combination of gemcitabine and capecitabine, a 5-FU pro-drug. We found no evidence that gemcitabine and capecitabine directly reduce MDSC% in patients. Gemcitabine and capecitabine reduced MDSCs in 42% of patients (n = 19) and MDSC% fell in only 3/9 patients with above-median baseline MDSCs. In 5/8 patients with minimal tumour volume change on treatment, the MDSC% went up: increases in MDSC% in these patients appeared to correlate with sustained cancer-related inflammatory cytokine upregulation. In a separate cohort of 21 patients treated with gemcitabine and capecitabine together with concurrently administered GV1001 vaccine with adjuvant GM-CSF, the MDSC% fell in 18/21 patients and there was a significant difference in the trajectory of MDSCs between those receiving GV1001 and GM-CSF in combination with chemotherapy and those receiving chemotherapy alone. Thus, there was no evidence that the addition of low-dose adjuvant GM-CSF increased Lin-DR-CD11b+ MDSC in patients receiving combination chemoimmunotherapy. 9/21 patients developed an immune response to GV1001 and the MDSCs fell in 8 of these 9 patients, 6 of whom had above-median pre-vaccination MDSC levels. A high pre-vaccination MDSC% does not preclude the development of immunity to a tumour-associated antigen.

Fig. 1

No significant differences in the level of pro-inflammatory cytokines in patients with high MDSCs compared with those with low MDSCs. Peripheral blood mononuclear cells from 33 pancreatic cancer patients obtained pre-treatment (at baseline) were immunostained for HLA-DR-APC-Cy7, Lin1(CD3,14,16,19,20,56)-FITC and CD11b-PECy7 and with ViViD to discriminate live and dead cells. Following immunostaining, cells were analyzed using a MACSQuant flow cytometer with MACSQuantify software. In addition, serum cytokines TNFα, MCP-1, IL-1b, IL-6 and VEGF were determined using the Bio Rad Bio Plex 27 Pro Cytokine, Chemokine and Growth Factor assay using the Bio Rad Bio Plex Instrument. Baseline MDSCs dichotomized at median (1.85) plotted with baseline IL-6, IL-1b, VEGF, TNFα and MCP-1 (pg/ml). P value generated for Mann–Whitney test shows no significant differences

Fig. 2

The trajectory of MDSC levels in patients receiving GemCap chemotherapy alone (arm 2) and GemCap chemotherapy concomitantly with GV1001 vaccination and low-dose adjuvant GM-CSF (arm 3). PBMCs were obtained pre- and post-treatment and immunostained for HLA-DR-APC-Cy7, Lin1(CD3,14,16,19,20,56)-FITC and CD11b-PECy7 as well as ViViD to discriminate live and dead cells. Following immunostaining cells were analyzed using a MACSQuant flow cytometer with MACSQuantify software. The graph depicts the log percentage change in Lin-DR-CD11b+ MDSCs from baseline in patients during treatment with gemcitabine and capecitabine. Blue denotes patients with progressive disease on treatment, black stable disease and green partial response by RECISTv1.1