RESUMEN
Plants delicately regulate endogenous auxin levels through the coordination of transport, biosynthesis, and inactivation, which is crucial for growth and development. While it is well-established that the actin cytoskeleton can regulate auxin levels by affecting polar transport, its potential role in auxin biosynthesis has remained largely unexplored. Using LC-MS/MS-based methods combined with fluorescent auxin marker detection, we observed a significant increase in root auxin levels upon deletion of the actin bundling proteins AtFIM4 and AtFIM5. Fluorescent observation, immunoblotting analysis, and biochemical approaches revealed that AtFIM4 and AtFIM5 affect the protein abundance of the key auxin synthesis enzyme YUC8 in roots. AtFIM4 and AtFIM5 regulate the auxin synthesis enzyme YUC8 at the protein level, with its degradation mediated by the 26S proteasome. This regulation modulates auxin synthesis and endogenous auxin levels in roots, consequently impacting root development. Based on these findings, we propose a molecular pathway centered on the 'actin cytoskeleton-26S proteasome-YUC8-auxin' axis that controls auxin levels. Our findings shed light on a new pathway through which plants regulate auxin synthesis. Moreover, this study illuminates a newfound role of the actin cytoskeleton in regulating plant growth and development, particularly through its involvement in maintaining protein homeostasis via the 26S proteasome.
RESUMEN
BACKGROUND: Patients with Eastern Cooperative Oncology Group performance status (ECOG PS) 2 probably cannot tolerate chemotherapy or other antitumor therapies. Some studies have reported that immunotherapy combined with antiangiogenic therapy is well-tolerated and shows good antitumor activity. However, the efficacy of this combination as a later-line therapy in patients with ECOG PS 2 is unclear. This study evaluated the effectiveness and safety of this combination strategy as third- or further-line therapy in stage IV non-small cell lung cancer (NSCLC) patients with ECOG PS 2. METHODS: In this retrospective study, patients treated with camrelizumab plus antiangiogenic therapy (bevacizumab, anlotinib, or recombinant human endostatin) were included. Objective response rate (ORR), disease control rate (DCR), progression-free survival (PFS), overall survival (OS), quality of life (QOL) assessed by ECOG PS, and safety were analyzed. RESULTS: Between January 10, 2019, and February 28, 2024, a total of 59 patients were included. The ORR was 35.6% (21/59) and the DCR was 86.4%. With a median follow-up of 10.5 months (range: 0.7-23.7), the median PFS was 5.5 months (95% confidence interval [CI]: 3.8-7.3) and the median OS was 10.5 months (95% CI: 11.2-13.6). QOL was improved (≥1 reduction in ECOG PS) in 39 patients (66.1%). The most common Grade 3-4 treatment-related adverse events were hepatic dysfunction (6 [10%]), hypertension (5 [8%]), and hypothyroidism (3 [5%]). There were no treatment-related deaths. CONCLUSIONS: Third- or further-line immunotherapy combined with antiangiogenic therapy is well-tolerated and shows good antitumor activity in stage IV NSCLC patients with ECOG PS 2. Future large-scale prospective studies are required to confirm the clinical benefits of this combination therapy.