Saponin-based adjuvants (SBAs) are being used in animal and human (cancer) vaccines, as they induce protective cellular immunity. Their adjuvant potency is a factor of inflammasome activation and enhanced antigen cross-presentation by dendritic cells (DCs), but how antigen cross-presentation is induced is not clear. Here we show that SBAs uniquely induce intracellular lipid bodies (LBs) in the CD11b+ DC subset in vitro and in vivo. Using genetic and pharmacological interference in models for vaccination and in situ tumour ablation, we demonstrate that LB induction is causally related to the saponin-dependent increase in cross-presentation and T-cell activation. These findings link adjuvant activity to LB formation, aid the application of SBAs as a cancer vaccine component, and will stimulate development of new adjuvants enhancing T-cell-mediated immunity.
Multidrug resistance (MDR) is often related to expression of P‐glycoprotein (Pgp) or Multidrug Resistance Protein (MRP). Pgp‐mediated MDR can be evaluated by determining cellular retention of fluorescent substrates by flow cytometry. This study determined if agents used to evaluate Pgp function also can be used to evaluate MRP function. Cellular retention of doxorubicin (Dox), Rhodamine‐123 (Rh‐123), and 3,3′‐diethyloxacarbocyanine iodide (DiOC2(3)) were studied in MRP‐expressing cell lines (HL60/Adr and HT1080/DR4), whereas a Pgp expressing cell line (A2780/Dx5) served as a positive control. Overexpression of Pgp correlated inversely with retention of Dox, Rh‐123, and DiOC2(3); however, under identical experimental conditions (1 h reincubation in drug‐free medium), no retention difference of the three agents was detected between parental and MRP‐expressing resistant cells. Upon extending the reincubation time to 4 h, an efflux of Rh‐123 and Dox in the resistant lines became apparent and even more pronounced after 24 h; however, still no efflux was detectable for DiOC2(3). Incubation of the cells with a modulator of MDR, PAK‐104P, negated the observed drug efflux in Pgp and MRP expressing cells, which correlated with increased sensitivity of the MDR lines to doxorubicin. Thus both Dox and Rh‐123 can be used to evaluate MRP‐function, but DiOC2(3) can not. © 1996 Wiley‐Liss, Inc.
Mantle cell lymphoma (MCL) is an aggressive non-Hodgkin lymphoma subtype arising from naïve B cells. Although novel therapeutics have improved patient prognosis, drug resistance remains a key problem. Here, we show that the SRC-family tyrosine kinase hematopoietic cell kinase (HCK), which is primarily expressed in the hematopoietic lineage but not in mature B cells, is aberrantly expressed in MCL, and that high expression of HCK is associated with inferior prognosis of MCL patients. HCK expression is controlled by the toll-like receptor (TLR) adaptor protein MYD88 and can be enhanced by TLR agonists in MCL cell lines and primary MCL. In line with this, primary MCL with high HCK expression are enriched for a TLR-signaling pathway gene set. Silencing of HCK expression results in cell cycle arrest and apoptosis. Furthermore, HCK controls integrin-mediated adhesion of MCL cells to extracellular matrix and stromal cells. Taken together, our data indicate that TLR/MYD88-controlled aberrant expression of HCK plays a critical role in MCL proliferation and survival as well as in retention of the malignant cells in the growth- and survival-supporting lymphoid organ microenvironment, thereby contributing to lymphomagenesis. These novel insights provide a strong rationale for therapeutic targeting of HCK in MCL.
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