TKIs’ effect on immune cell infiltration in bone tumors. A, Impact of TKIs on CD8 infiltration in RENCA VHL− tumors in bone evaluated by IF analysis; representative images acquired at the confocal microscope (green, GFP; blue, DAPI; yellow, CD8; red, laminin) are shown; dotted line, tumor area. Bar, 100 μm. B, Quantification of the number and distribution of CD8+ cells associated with tumor; mean ± SEM, n = 6–12/group. C, Representative images and quantification (D and E) of immune subsets infiltrating bone tumors by multiplex imaging (COMET, Lunaphore) post-TKI treatment, mean ± SEM, n = 3/group P values by one-way ANOVA with Tukey honestly significant difference post hoc test; *, P < 0.05; **, P < 0.01; ***, P < 0.0001. Inner tumor region >25 μm from the tumor edge. A, axitinib; C, cabozantinib; Inner reg, inner region; L, lenvatinib; Lam, laminin; lymph, lymphocytes; myel, myeloid; V, vehicle.
ARTICLE ABSTRACT
Clear cell renal cell carcinoma (ccRCC) is the most prevalent kidney neoplasm; bone metastasis (BM) develops in 35% to 40% of metastatic patients and results in substantial morbidity and mortality, as well as medical costs. A key feature of ccRCC is the loss of function of the von Hippel–Lindau protein, which enhances angiogenesis via vascular endothelial growth factor release. Consequently, antiangiogenic tyrosine kinase inhibitors (TKI) emerged as a treatment for ccRCC. However, limited data about their efficacy in BM is available, and no systematic comparisons have been performed. We developed mouse models of bone and lung ccRCC tumors and compared their anticancer efficacy, impact on mouse survival, and mechanisms of action, including effects on tumor cells and both immune and nonimmune (blood vessels and osteoclasts) bone stromal components. This approach elucidates the efficacy of TKIs in ccRCC bone tumors to support rational interrogation and development of therapies.
TKIs showed different efficacy in synchronous bone and lung metastases and did not eradicate tumors as single agents but induced extensive reprogramming of the BM microenvironment. This resulted in a significant decrease in neoangiogenic blood vessels, bone remodeling, and immune cell infiltration (including CD8 T cells) with altered spatial distribution.
