Inhibition of Proteasome LMP2 Activity Suppresses Chil3 Expression in Mouse Colon Adenocarcinoma Tissue and Restrains Tumor Growth
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Updated: Jan 18, 2026
In Vivo Inhibition of MicroRNA to Decrease Tumor Growth in Mice
Published on: August 23, 2019
Tatiana M Astakhova1, Nikita S Karpov1, Nataliya O Dashenkova1
1Koltzov Institute of Developmental Biology, Russian Academy of Sciences, Moscow, 119334, Russia.
Objectives:
Proteasomes, multi-subunit proteases, are key actors of cellular protein catabolism and a number of regulatory processes. The detection of subtle proteasome functioning in tumors may contribute to our understanding of the mechanisms of cancer development. The current study aimed to identify the role of low molecular mass protein 2 (LMP2), a proteasome immune subunit, in the development of mouse colon 26 (C26) adenocarcinoma.
Methods:
The functions of the LMP2 subunit in tumor development in Balb/c mice were studied using its irreversible inhibitor KZR-504. LMP2 activity was detected by the hydrolysis of the fluorogenic substrate Ac-Pro-Ala-Leu-AMC. Western blotting and Quantitative Reverse Transcription Polymerase Chain Reaction (qRT-PCR) were used. We applied fluorescent tests for cell proliferation and apoptosis. M2 macrophages were obtained by polarization of mouse bone marrow-derived macrophages using the corresponding cytokines.
Results:
KZR-504 showed high specificity only for the LMP2 subunit and had no negative effect on C26 cells in culture. However, KZR-504 suppressed the formation of tumor conglomerates (by 74%, p < 0.001) after C26 cell transplantation in vivo, inhibited the expression of chitinase-3-like protein 3 (Chil3) gene (by 90%, p < 0.001), a key marker of immunosuppressive M2 macrophages, in the tumor microenvironment, and reduced the tumor weight compared to the control (by 48%, p < 0.01). KZR-504 also suppressed the expression of Chil3 (by 68%, p < 0.05) and arginase-1 (Arg1) (by 90%, p < 0.001), another marker gene, in M2 macrophages and violated M0-M2 macrophage polarization in culture.
Conclusion:
We discovered earlier unknown functions of the proteasome LMP2 subunit to facilitate the formation of tumor conglomerates and maintain Chil3 and Arg1 expression in immunosuppressive M2 macrophages. Our work demonstrates that the proteasome LMP2 subunit can be a target for antitumor treatment.
Insights
The proteasome LMP2 subunit promotes tumor growth by aiding conglomerate formation and supporting immunosuppressive M2 macrophages. Inhibiting LMP2 offers a potential new strategy for colon cancer treatment.
Area of Science:
- Cellular Biology
- Cancer Research
- Immunology
Background:
- Proteasomes are crucial for protein breakdown and cellular regulation.
- Understanding proteasome function in tumors is key to cancer development research.
- The role of the proteasome immune subunit LMP2 in colon adenocarcinoma is investigated.
Purpose of the Study:
- To elucidate the function of the LMP2 subunit in the development of mouse colon 26 (C26) adenocarcinoma.
- To evaluate the therapeutic potential of targeting the LMP2 subunit.
Main Methods:
- Utilized KZR-504, an irreversible inhibitor specific to LMP2.
- Assessed LMP2 activity via fluorogenic substrate hydrolysis.
- Employed Western blotting, qRT-PCR, and fluorescent assays for proliferation and apoptosis.
- Induced M2 macrophage polarization from bone marrow-derived macrophages.
Main Results:
- KZR-504 selectively inhibited LMP2 without affecting C26 cells in vitro.
- In vivo, KZR-504 suppressed tumor conglomerate formation (74%) and reduced tumor weight (48%).
- KZR-504 significantly inhibited key M2 macrophage markers (Chil3 by 90%, Arg1 by 90%) and disrupted M0-M2 polarization.
Conclusions:
- The proteasome LMP2 subunit plays a previously unrecognized role in facilitating tumor conglomerate formation.
- LMP2 is essential for maintaining the expression of immunosuppressive markers (Chil3, Arg1) in M2 macrophages.
- Targeting the proteasome LMP2 subunit presents a promising avenue for novel antitumor therapies.
