LITAF suppresses breast cancer and paclitaxel resistance by ubiquitinating and degrading PCMT1 to inhibit COX-2-dependent arachidonic acid metabolism

Na Yang¹Jingying Cao²Feng Jiang¹Renxian Cao³Yiqi Liu^4*

• ¹The First Affiliated Hospital, Gynecology &Obstetrics and Reproductive Medical Center, Hengyang Medical School, University of South China, Hengyang, China
• ²The Third Xiangya Hospital of Central South University, Changsha, China
• ³The First Affiliated Hospital, Hengyang Medical School, University of South China, Hengyang, China
• ⁴The First Affiliated Hospital, Gynecology &Obstetrics and Reproductive Medical Center Hengyang Medical School, University of South China, Hengyang, China

Background: Paclitaxel (PTX) is a first-line chemotherapeutic agent extensively employed in the management of breast cancer (BC); however, the emergence of drug resistance frequently results in unsatisfactory clinical outcomes and poor prognosis. This study aimed to investigate the pathogenic mechanisms that drive PTX resistance in BC. Methods: Tumor and matched adjacent normal tissues were collected from 30 BC patients treated with PTX. Untargeted metabolomics was performed to analyze the metabolic differences. The expression of lipopolysaccharide-induced tumor necrosis factor-alpha factor (LITAF), protein L-isoaspartyl (D-aspartyl) methyltransferase (PCMT1), and cyclooxygenase-2 (COX-2) was assessed using RT-qPCR, immunoblotting, and immunohistochemistry (IHC). Cell proliferation was determined via CCK-8 and colony formation assays, cell apoptosis by flow cytometry, and enzyme-linked immunosorbent assay (ELISA) was used to measure arachidonic acid (AA) and prostaglandin E2 levels. The interaction between LITAF and PCMT1, as well as the ubiquitination level of PCMT1, was investigated using co-immunoprecipitation (Co-IP). In vivo, nude mice were used to explore the effect of LITAF on tumor response to PTX treatment. Results: PCMT1 and COX-2 were upregulated in BC tissues, particularly in PTX-resistant patients, whereas LITAF expression was downregulated. In BC tissues, LITAF expression was negatively correlated with PCMT1 levels, while PCMT1 expression showed a positive correlation with COX-2 levels. PCMT1 knockdown attenuated COX-2-mediated AA metabolism, suppressed BC cell proliferation, and increased the sensitivity of BC cells to PTX. LITAF interacted with PCMT1 and promoted ubiquitination-mediated degradation of PCMT1, thereby inhibiting COX-2-mediated AA metabolism, reducing the proliferation of PTX-resistant BC cells, and enhancing the sensitivity of BC cells to PTX in vivo. Conclusion: LITAF regulates the ubiquitination-mediated degradation of PCMT1 to inhibit COX-2-dependent AA metabolism, thereby enhancing the sensitivity of BC cells to PTX and providing a potential therapeutic strategy to overcome PTX resistance in BC.