Graduation Date

Fall 12-19-2025

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Programs

Biochemistry & Molecular Biology

First Advisor

Mohd Wasim Nasser

Abstract

Small-cell lung cancer (SCLC) is an aggressive malignancy that is generally considered an immune desert. The therapeutic impact of immune checkpoint inhibitors in SCLC is modest and confined to a small population of patients. The immune checkpoint protein B7-H3 (also known as CD276) is highly expressed in SCLC; however, its functional contribution to SCLC remains unexplored. Here, to dissect tumor-intrinsic and immunomodulatory functions of B7-H3, we generated a novel genetically engineered mouse (GEM) model Rb1fl/fl; Trp53fl/fl; LSL-MycT58A; Cd276fl/fl (RPMC). Cd276 deletion significantly impaired primary tumor growth, metastatic dissemination, and reprogrammed the SCLC tumor microenvironment by increasing CD8+ T-cell infiltration and decreasing immunosuppressive myeloid populations. Loss of B7-H3 also improved responsiveness to combination therapy (cisplatin and anti-PD-L1) by modulating the anti-tumor immune response. Mechanistically, B7-H3 regulates NFIB through a CXCL11-CXCR7 feed-forward loop. To further evaluate translational implications, we tested a B7-H3 targeted antibody-drug conjugate m276-SL-PBD, which abrogated SCLC in the GEM model. Collectively, our findings establish B7-H3 as a key regulator of SCLC progression, metastatic competence, and immune escape, and highlight B7-H3-directed therapies as promising strategies for this recalcitrant disease.

Comments

2025 Copyright, the authors

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