Proteasome Inhibition as a Cancer Type-Specific Off-Target Effect of Everolimus in Cancer Cells

---

Anna S. Vorobeva¹, Elizaveta M. Kazakova¹, Leyla A. Garibova¹, Daria D. Emekeeva¹, Tomiris T. Kusainova¹, Ivan I. Fedorov¹, Andrey A. Shelepchikov², Alexey V. Tretyakov², Anton O. Chugunov^3,4, Mikhail V. Gorshkov¹, and Irina A. Tarasova^1,a*

¹Talrose Institute for Energy Problems of Chemical Physics, Semenov Federal Research Center for Chemical Physics, Russian Academy of Sciences, 119334 Moscow, Russia

²Russian State Center for Animal Feed and Drug Standardization and Quality, 123022 Moscow, Russia

³Shemyakin–Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 117997 Moscow, Russia

⁴Scientific Research Institute for Systems Biology and Medicine, 117246 Moscow, Russia

^* To whom correspondence should be addressed.

Received: September 22, 2025; Revised: December 3, 2025; Accepted: January 20, 2026

---

Everolimus, an mTORC1 inhibitor, may also affect proteasome activity in a manner similar to bortezomib, necessitating further investigation. In this study, we employed ultrafast expression proteomics in combination with cell viability and proteasome activity assays to identify potential secondary targets of everolimus and to obtain a more comprehensive understanding of its mechanism of action across the proteomes of multiple cancer cell lines. The results were compared with those obtained for bortezomib and lonidamine, which were used as positive and negative controls for proteasome inhibition, respectively. Our findings reveal that everolimus inhibits 20S proteasome in lung (A549) and colon (HCT116) cancer cells, while having no detectable effect in breast cancer cells (MCF-7). An in silico model of everolimus interaction with 20S proteasome was built suggesting an allosteric mechanism of inhibition.

---

KEY WORDS: proteasome inhibitors, ultrafast proteomics, bortezomib, everolimus, protein expression

DOI: 10.1134/S0006297925603284

Publisher’s Note. Pleiades Publishing remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

---