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Updated: Apr 23, 2026
A Simple and Efficient Method for Testing Immunomodulatory Agents for Generation of Tolerogenic Dendritic Cells from Human CD14+ Monocytes
Published on: April 11, 2025
Novel N-amidinopiperidine-based proteasome inhibitor preserves dendritic cell functionality and rescues their
Urban Švajger1, Martina Gobec, Aleš Obreza
1Blood Transfusion Centre of Slovenia, Šlajmerjeva 6, 1000, Ljubljana, Slovenia, svajgerurban@yahoo.com.
Abstract:
The tumor microenvironment represents a burden that hampers the proper activation of immune cells, including the dendritic cells (DCs). It is, therefore, desired that the important characteristics of a given anticancer drug candidate be seen as consisting not solely of its antitumor properties, but that it also lacks potential side effects that could additionally constrain the development and function of immune cells associated with tumor immunity. We have previously identified compounds with a N-amidinopiperidine scaffold that selectively induce apoptosis in Burkitt's lymphoma cells through proteasome inhibition. Here, we demonstrate that SPI-15 affected neither the viability of DCs nor their differentiation. In addition, the compound had no significant effect on their cytokine secretion or allostimulatory capacity. Moreover, DC functionality in the context of tumor microenvironment was also unaffected, as demonstrated by experiments performed on DCs differentiated in Ramos-conditioned media in the presence or absence of SPI-15. The cytokine profile and functional assays revealed that SPI-15 rescues DC differentiation from the immunosuppressive environment produced by Ramos cells; this was seen by their reacquired ability to induce IFN-γ-secretion from naïve CD4(+)CD45RA(+) T cells and the consequently induced Th1-effector differentiation. Herein, we present novel characteristics of an N-amidinopiperidine-based protease inhibitor whose anticancer properties are not associated with the immunosuppression of DCs. We propose future studies toward the design of structurally similar compounds with the aim of developing potent anticancer drugs with minimal negative effects on crucial factors involved in tumor immunity.
Insights
This study shows SPI-15, a proteasome inhibitor, does not harm dendritic cell (DC) function. It even rescues DC differentiation in immunosuppressive environments, supporting its potential as an anticancer drug with minimal immune side effects.
Area of Science:
- Immunology
- Pharmacology
- Cancer Research
Background:
- The tumor microenvironment often impairs immune cell function, hindering effective anti-cancer immunity.
- Anticancer drug candidates should possess antitumor properties without compromising immune cell development or function.
- Previous research identified N-amidinopiperidine compounds that induce apoptosis in lymphoma cells via proteasome inhibition.
Purpose of the Study:
- To evaluate the impact of SPI-15, a novel N-amidinopiperidine-based protease inhibitor, on dendritic cell (DC) viability, differentiation, and function.
- To assess whether SPI-15 exhibits immunosuppressive effects on DCs, particularly within a tumor microenvironment context.
- To investigate SPI-15's potential to counteract the immunosuppressive effects of tumor-associated cells on DC function.
Main Methods:
- Assessing DC viability, differentiation, cytokine secretion, and allostimulatory capacity in the presence of SPI-15.
- Conducting experiments using DCs differentiated in Ramos-conditioned media (simulating a tumor microenvironment) with and without SPI-15.
- Analyzing cytokine profiles and functional assays to evaluate T-cell activation and differentiation (e.g., Th1 response).
Main Results:
- SPI-15 did not affect DC viability, differentiation, cytokine secretion, or allostimulatory capacity.
- DC function remained unaffected when differentiated in a tumor-conditioned (Ramos) environment with SPI-15.
- SPI-15 demonstrated a rescuing effect on DC differentiation in an immunosuppressive environment, restoring their ability to induce IFN-γ secretion and Th1 differentiation.
Conclusions:
- SPI-15, an N-amidinopiperidine-based protease inhibitor, possesses anticancer properties without causing immunosuppression of dendritic cells.
- The compound effectively counteracts the immunosuppressive effects of the tumor microenvironment on DC function.
- SPI-15 represents a promising lead for developing novel anticancer drugs with improved immunomodulatory profiles and reduced side effects on tumor immunity.
