Conventional and plasmacytoid dendritic cell (cDC and pDC) subsets, both capable of priming anti-tumor T-cell responses, were monitored in the blood of 16 patients with Locally Advanced Breast Cancer (LABC). Between 1999 and 2002 these patients were treated in the VU University medical center in Amsterdam, as part of a randomized multi-center phase III trial, comparing six 3-week courses of neo-adjuvant doxorubicin and cyclophosphamide (AC) with a split course administration of 3 neo- and 3 adjuvant cycles, combined with systemic doses of either GM-CSF (n=10) or G-CSF (n=6). Pre-treatment frequencies of CD1c/BDCA1+ cDC (MDC1) and of the CD16+M-DC8+ monocytoid (M-DC8) subsets were significantly decreased as compared to frequencies observed in 13 age-matched healthy women (MDC1: 0.21±0.16% vs 0.38±0.17%, p=0.004; M-DC8: 0.24±0.14% vs 0.45±0.22%, p=0.05), while no differences were observed for the BDCA3+ cDC (MDC2) and the BDCA2+ pDC subsets. No differences for the studied subset rates were observed over follow-up between the 6-cycle neo-adjuvant and split-course chemotherapy regimens. Whereas the frequencies of the cDC subsets MDC1 and MDC2 increased upon treatment with either GM- (2- to 3-fold) or G-CSF (3- to 5-fold), pDC rates only increased in G-CSF-administered patients (3-fold), all p<0.05. CD14+ monocytes also increased significantly over treatment with both growth factors, while only minor increases in CD14+HLA-DR- Myeloid Suppressor Cells (MSC) were observed that did not reach significance. No changes in maturation state were observed over treatment for any of the studied subsets, based on CD40, CD86, or HLA-DR levels.Pre- and post-treatment plasma samples were analyzed for the suppressive cytokines IL-6, IL-10 and vascular endothelial growth factor (VEGF). Only VEGF levels were significantly higher in pre-treatment sera as compared to sera from age-matched healthy women (103.6±144.7 vs 17.8±42.0 pg/ml, p=0.03). Of note, in 4 out of 5 G-CSF-treated patients, decreasing VEGF levels coincided with rising MDC1 pre- and post-treatment, suggestive of a causal relationship. In contrast, this was observed in only 1 out of 6 GM-CSF-administered patients. High (i.e. above median) pre-treatment frequencies of MDC1, M-DC8 and monocytes, but not of MDC2 or pDC, were associated with prolonged over-all survival, although patient numbers were too small for these associations to reach significance (p=0.14, p=0.09, and p=0.07 for MDC1, M-DC8, and monocytes, respectively). Interestingly, whereas the G-CSF-administered patients showed more prominent increases in peripheral blood DC frequencies, prolonged disease free (p=0.052) and over-all survival (p=0.15) was rather observed for the GM-CSF-administered patients. Additional analyses suggest that this may be due to increased numbers of mature DC in the tumor-draining lymph nodes of the GM-CSF-treated patients.

Citation Information: In: Proc Am Assoc Cancer Res; 2009 Apr 18-22; Denver, CO. Philadelphia (PA): AACR; 2009. Abstract nr 3574.

100th AACR Annual Meeting-- Apr 18-22, 2009; Denver, CO