OCEL1 (occludin/ELL domain containing 1) is a negative regulator of NF-κB signaling that plays a critical role in controlling inflammatory responses to bacterial infection. Under basal conditions, OCEL1 binds the NEMO protein and suppresses TRAF6-mediated K63-linked polyubiquitination, thereby inhibiting NF-κB signaling 1. During bacterial infection, bacterial peptidyl-prolyl isomerases recognize a palindromic proline-rich element (PPE) in OCEL1's amino terminus, promoting its degradation and thereby releasing NF-κB suppression to enable appropriate inflammatory responses 1. Mice expressing OCEL1 with a mutated PPE showed dampened inflammation and increased susceptibility to Pseudomonas aeruginosa, establishing OCEL1's infection-sensing function as essential for host defense 1. Beyond immunity, OCEL1 expression correlates with disease prognosis in human malignancies: low OCEL1 expression is significantly associated with poor prognosis in non-small cell lung cancer, including lymph node metastasis and higher TNM stage 2. OCEL1 also appears relevant to chemotherapy response, as it was identified in a four-gene signature predicting paclitaxel sensitivity in HER2-negative breast cancer 3. These findings suggest OCEL1 functions as both an infection sensor and a prognostic biomarker across distinct pathological contexts.