BCL2L15 is a pro-apoptotic member of the BCL2 family that functions as a regulator of programmed cell death. Located in the cytosol and nucleus 1, BCL2L15 mediates apoptosis through protein-protein interactions characteristic of BCL2 family members 2. In cancer biology, BCL2L15 exhibits tumor-suppressive properties. In colorectal cancer, BCL2L15 is selectively expressed in cells responsive to 5-Fluorouracil therapy, and its downregulation correlates with increased drug resistance 3. In retinoblastoma, KLF16 transcriptionally represses BCL2L15 expression by binding its promoter, promoting cell proliferation and migration while suppressing apoptosis 1. BCL2L15 expression inversely correlates with cancer aggressiveness and predicts improved survival outcomes 3. In diffuse large B-cell lymphoma, BCL2L15 serves as a pro-apoptotic signature component; elevated BCL2 signature scores incorporating BCL2L15 associate with poor prognosis independent of standard prognostic factors 2. Beyond cancer, BCL2L15 dysregulation appears relevant to respiratory diseases—upregulated in microplastic-exposed asthmatic epithelial cells 4 and COVID-19-associated pulmonary fibrosis 5—and adverse pregnancy outcomes 6. These findings establish BCL2L15 as a pro-apoptotic factor with significant implications for cancer prognosis and therapeutic resistance.