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Dendritic cells (DCs) within the tumor microenvironment (TME) have an insufficient capacity to activate T cells through antigen presentation. Furthermore, the programmed cell-death ligand 1 (PD-L1), abundantly expressed on tumor-associated DCs, binds the programmed cell-death 1 (PD-1)-positive T cells and suppresses their immune function. The binding of PD-L1 to CD80 (B7.1) on the same DC via cis-interactions further prevents T cell costimulation through CD28. Here, we present a strategy to simultaneously promote antigen cross-presentation and block the inhibitory interactions of PD-L1 on DCs to amplify T cell-mediated antitumor responses within the TME. Mesoporous silica nanoparticles (MSNPs) were loaded with clotrimazole (CLT) to boost MHC II-mediated antigen presentation by DCs, surface-modified with mannose to target CD206 on DCs, and then decorated with PD-L1 binding peptide (PDL1bp) to block PD-L1-mediated interactions. PDL1bp was cleaved from the mannosylated and CLT-loaded MSNPs (MSNP-MaN/CLT) under conditions simulating the TME and tethered to PD-L1 to reverse CD80 sequestration on DC2.4 cells. The blocking of PD-L1 by PDL1bp-decorated NPs (MSNP-MaN-PDL1bp) increased the cellular interactions between DC2.4 and EL4 T cells and the amount of IL-2 secretion. The MSNP-MaN/CLT were taken up rapidly by DC2.4 cells, promoted MHC II presentation of hen egg lysozyme (HEL), and increased IL-2 production from HEL antigen-primed 3A9 T cells, which was further enhanced by PDL1bp. In vivo investigation revealed that administration of the CLT-loaded and PDL1bp-functionalized MSNPs remarkably inhibited subcutaneous B16-F10 melanoma tumor growth when compared with anti-PD-L1 therapy. MSNP-MaN-PDL1bp/CLT treatment upregulated the levels of effector molecules such as granzyme B and proinflammatory cytokines (IFNγ and INFα) in the tumor tissue, indicating antitumoral T cell responses. This strategy of utilizing nanoparticles to trigger DC activation while promoting T cell stimulation can be used to amplify the antitumor T cell responses and represents a promising alternative to anti-PD-L1 immunotherapy.

One of the greatest challenges in cancer therapy is to control metastatic spread, seeding, and growth of tumors in distant organs. Recently, we reported on the design of a novel “drug-free” therapeutic copolymer bearing the antimigratory A5G27 peptide, designated P-(A5G27)-FITC, that shows excellent specificity to cancer cells overexpressing CD44v3 and CD44v6 and inhibits cancer cell migration and invasion. We demonstrated that P-(A5G27)-FITC accumulated preferentially in subcutaneous (sc) implanted 4T1 tumors following parenteral administration. Moreover, we showed that pretreatment of mice with P-(A5G27)-FITC prior to 4T1 cell inoculation inhibited colonization of circulating 4T1 cells in the lungs. In this study, we designed a new polymer-peptide-drug conjugate to inhibit vigorously growing primary tumors and control invasive behavior of cancer cells. To this end, the antimitotic drug (paclitaxel, PTX) was conjugated to P-(A5G27)-FITC. The targeted polymer–drug conjugate (P-(A5G27)-PTX) was significantly more toxic toward CD44-overexpressing cancer cells than the nontargeted copolymer. In vivo, a single iv injection of P-(A5G27)-PTX prolonged the survival of C57BL/6 mice with established B16-F10 lung metastases. When injected intraperitoneally into BALB/c mice implanted sc with 4T1 tumors, P-(A5G27)-PTX significantly decreased the rate of primary tumor growth, increased the median survival of mice, and reduced the number of 4T1 metastases in the lungs when compared to nontargeted copolymer. Most interestingly, the CD44-targeted “drug-free” copolymer P-(A5G27) (without PTX) significantly inhibited the rate of tumor growth and further prolonged the median survival time of mice to the same extent as the PTX-containing formulations (P-(A5G27)-PTX or free PTX). Overall, this study highlights the therapeutic potential of the HPMA copolymer–A5G27 conjugates (“drug-free” and PTX-bearing copolymers) to control the metastatic spread of cancer.

Progress was made towards a reliable in vitrosystem for mycorrhizing Cistus incanusseedlings with Tuber melanosporum. A rich growth medium favored extensive growth of mycorrhized Ri-transformed roots (MTR) but inhibited mycelial outgrowth into the medium. A minimal medium, on the other hand, inhibited MTR growth but supported considerable mycelial outgrowth into the medium. While the presence of a C.␣incanuspropagule clearly enhanced mycelial growth into the minimal medium, a highly significant factor appeared to be the use of MTR inoculant, which supported mycorrhizal development to the Hartig net stage. The advantages of MTR for in vitromycorrhization of host plant seedlings are discussed.Progress was made towards a reliable in vitrosystem for mycorrhizing Cistus incanusseedlings with Tuber melanosporum. A rich growth medium favored extensive growth of mycorrhized Ri-transformed roots (MTR) but inhibited mycelial outgrowth into the medium. A minimal medium, on the other hand, inhibited MTR growth but supported considerable mycelial outgrowth into the medium. While the presence of a C.␣incanuspropagule clearly enhanced mycelial growth into the minimal medium, a highly significant factor appeared to be the use of MTR inoculant, which supported mycorrhizal development to the Hartig net stage. The advantages of MTR for in vitromycorrhization of host plant seedlings are discussed.