TY  - EJOU
AU  - Barbosa, Gabriela R. 
AU  - Col, Luciana S. B. Dal 
AU  - Bighetto, Caroline C. 
AU  - Godoy, Maria Carolina X. de 
AU  - Campioni, Marina D. B. P. 
AU  - Sadi, Marcus V. 
AU  - Gambero, Alessandra 
AU  - Reis, Leonardo O. 

TI  - BCG Induces PD-1 Upregulation on Circulating CD8<sup>+</sup> T Cells and IL-6 and IL-8 Secretion <i>In Vitro</i>
T2  - Oncology Research

PY  - 
VL  - 
IS  - 
SN  - 1555-3906

AB  - <b>Backgrounds:</b> Bacillus Calmette-Guérin (BCG) remains the most effective adjuvant therapy for non-muscle-invasive bladder cancer (NMIBC); however, the immunological underpinnings of its efficacy remain incompletely understood. This study aims to elucidate the dual immunomodulatory roles of BCG by integrating systemic and tumor-intrinsic analyses, through determining the systemic effects of BCG instillation on immune checkpoint expression and direct inflammatory response in a previously established <i>in vitro</i> tumor model. <b>Methods:</b> We investigated systemic and tumor-intrinsic immune responses to BCG. Flow cytometry was used to evaluate immune checkpoint expression on circulating lymphocyte subsets in NMIBC patients (n = 7) at various stages of BCG therapy. In parallel, an <i>in vitro</i> model of PD-L1 modulation using breast cancer cell lines (MDA-MB-231 and MCF-7) was stimulated with BCG and TLR agonists, and the secretion of IL-6 and IL-8 was assessed using an ELISA. <b>Results:</b> Peripheral immune profiling revealed stable lymphocyte frequencies, but a significant increase in PD-1 expression on CD8<sup>+</sup> T cells following BCG exposure (<i>p</i> = 0.0068), with no significant modulation in CTLA-4 levels. <i>In vitro</i>, MDA-MB-231 cells exhibited robust IL-6 secretion upon high-dose BCG stimulation (<i>p</i> = 0.0277), whereas MCF-7 cells showed increased IL-8 release (<i>p</i> < 0.0001). Other TLR agonists had limited effects. <b>Conclusions:</b> BCG induces dual immunomodulation, characterized by PD-1 upregulation in systemic CD8<sup>+</sup> T cells and the release of pro-inflammatory cytokines from epithelial tumor cells. These findings support the potential of combining BCG with immune checkpoint inhibitors and underscore IL-6 and IL-8 as candidate biomarkers of tumor-intrinsic responsiveness.
KW  - BCG immunotherapy; breast cancer; Toll-like receptors agonists; bladder cancer

DO  - 10.32604/or.2026.075738