Modulation of regulatory dendritic cell polarization in cancer by paclitaxel.

Abstract

e21001 Background: Tumors are dynamic organs, in which active processes of cell differentiation affect disease course by regulating the composition of cells at the tumor site. we hypothesize that regDC form the premalignant niche in the lung to support lung cancer development and sustain lung cancer growth and progression. Furthermore, we evaluated if paclitaxel affected regDC and paclitaxel in noncytotoxic concentrations prevents polarization of cDC into regDC.Methods: Bone marrow-derived cDC were treated with tumor conditioned media from 3LL lung cancer cell lines for 48 h, washed, depleted of GR1+ cells and added to ConA-stimulated syngeneic T cells. 3LL-induced regDC were isolated by cell sorting from the in vitro generated cultures or from lungs harvested from 3LL-bearing mice. Analysis of immunosuppressive DC revealed them as CD11clowCD11bhigh CD80lowCD86lowMHC-IIlowPDCA1negGR1neg cells. For the in vivo evaluation of the potential protumorigenic properties of regDC, sorted CD11clowCD11bhigh (regDC) and CD11chighCD11blow/neg (cDC) subsets were injected (5x105cells i.p.) into mice together with 1/15 of the minimum tumorigenic dose of 3LL tumor cells (2x104cells, i.v.). As expected, no tumor nodules were detected in lungs in mice treated with saline or cDC (0/6 mice).However, >30% of mice injected with regDC developed lung tumors, suggesting that regDC exhibit a potent protumorigenic activity in vivo. Next, we asked if paclitaxel could alter regDC formation in vivo. Paclitaxel was administered in 3LL lung metastasis bearing mice. Lymphoid and non-lymphoid tissues were harvested 3 weeks later and analyzed for regDC subsets by flow cytometry.Results: The addition of tumor conditioned converts immunostimulatory cDC into regDC that can suppress proliferation of T cells. Paclitaxel in ultra low noncytotoxic concentrations in vitro could prevent tumor-induced polarization of conventional cDC into regDC. Furthermore, administration of paclitaxel prevented formation of regDC in the lung and significantly inhibited formation of metastases .Conclusions: These data suggest that paclitaxel in ultra low nontoxic doses is able to module the tumor immunoenvironment and support the anti-cancer efficacy of cancer vaccine.