Targeting the tumor cell-intrinsic ITGB2 axis inhibits melanoma progression.

BACKGROUND: ITGB2 is a critical integrin mediator of immune cell activation and trafficking. Its expression has been claimed as exclusive to hematopoietic cells. Consequently, the significance of cancer cell-intrinsic ITGB2 in solid tumor progression and therapy has not been rigorously evaluated. METHODS: We leveraged single-cell and bulk RNA sequencing, real-time quantitative PCR, multiplex immunofluorescence, flow cytometry, immunoblotting, and intercellular adhesion molecule (ICAM)-1-dependent adhesion and proliferation assays to uncover melanoma cell-intrinsic ITGB2 functional expression, association with clinical tumor progression, activation, protumorigenic signaling, adhesive and proliferative functions utilizing patient melanoma biospecimens, established human and murine melanoma lines. In vivo tumorigenicity studies in immunocompromised NOD/SCID interleukin-2 receptor γ chain null (NSG), immunocompetent wildtype, and Icam1 knockout (KO) C57BL/6 mice were performed to dissect melanoma-ITGB2 downstream pathway activity and functions in tumor growth and metastasis. The cancer cell-intrinsic ITGB2 axis was targeted using CRISPR/Cas9-based Itgb2 KO, blocking ITGB2 antibodies, ITGB2-activating CD44 crosslinking, and pharmacologic inhibition of ITGB2-dependent Wnt signaling using LGK974, zamaporvint, and FDA-approved pyrvinium pamoate repurposed for cancer therapy. RESULTS: This work demonstrates nonhematopoietic expression and protumorigenic functions of ITGB2 intrinsic to melanoma cells. Tumor cell-ITGB2 mediated adhesion to ICAM-1, promoted cancer progression in preclinical melanoma models, was enriched in clinical metastatic versus primary melanomas or benign nevi, and predicted sentinel lymph node metastasis in patients with primary disease. Consistently, inhibition of melanoma cell-intrinsic ITGB2 using blocking antibodies or Itgb2 gene KO potently suppressed ICAM-1-mediated melanoma cell adhesion, tumor growth, and metastatic dissemination. Melanoma cell-ITGB2:ICAM-1 interaction activated downstream Wnt signaling, the pharmacologic inhibition of which suppressed melanoma-ITGB2-mediated tumorigenesis. CONCLUSIONS: This work overturns the longstanding paradigm that ITGB2 is restricted to leukocytes by discovering a tumor cell-intrinsic ITGB2:ICAM-1:Wnt protumorigenic axis as a bona fide cancer therapeutic target in melanoma.