Preclinical studies demonstrated that complement promotes tumor growth. Therefore, we sought to determine the best target for complement-based therapy among common human malignancies. High expression of 11 complement genes was linked to unfavorable prognosis in renal cell carcinoma. Complement protein expression or deposition was observed mainly in stroma, leukocytes, and tumor vasculature, corresponding to a role of complement in regulating the tumor microenvironment. Complement abundance in tumors correlated with a high nuclear grade. Complement genes clustered within an aggressive inflammatory subtype of renal cancer characterized by poor prognosis, markers of T cell dysfunction, and alternatively activated macrophages. Plasma levels of complement proteins correlated with response to immune checkpoint inhibitors. Corroborating human data, complement deficiencies and blockade reduced tumor growth by enhancing antitumor immunity and seemingly reducing angiogenesis in a mouse model of kidney cancer resistant to PD-1 blockade. Overall, this study implicates complement in the immune landscape of renal cell carcinoma, and notwithstanding cohort size and preclinical model limitations, the data suggest that tumors resistant to immune checkpoint inhibitors might be suitable targets for complement-based therapy.

The link of the complement system to angiogenesis has remained circumstantial and speculative for several years. Perhaps the most clinically relevant example of possible involvement of complement in pathological neovascularization is age-related macular degeneration. Recent studies, however, provide more direct and experimental evidence that indeed the complement system regulates physiological and pathological angiogenesis in models of wound healing, retinal regeneration, age-related macular degeneration, and cancer. Interestingly, complement-dependent mechanisms involved in angiogenesis are very much context dependent, including anti- and proangiogenic functions. Here, we discuss these new developments that place complement among other important regulators of homeostatic and pathological angiogenesis, and we provide the perspective on how these newly discovered complement functions can be targeted for therapy.

Colorectal cancer is a leading cause of cancer-related deaths worldwide. The current standard of care for patients may involve surgery, chemotherapy, and immune checkpoint inhibitors, but these approaches typically fail to secure durable responses against late-stage disease. Regorafenib (REG) is an FDA-approved tyrosine kinase inhibitor with immunomodulating properties for patients with colorectal cancer who progress on standard care, but 5-year relative survival rates for individuals dosed with the drug as a monotherapy are poor. We hypothesize that REG may be more appropriately leveraged alongside immunotherapeutic agents that specifically stimulate T-cell infiltration and activation within the tumor microenvironment (TME). We engineered a PD-L1/CD3 bispecific antibody (bsAb) that simultaneously binds PD-L1–expressing colorectal cancer cells and stimulates activated T cells in order to investigate combination strategies with REG in preclinical models of colorectal cancer. Combined REG + bsAb therapy safely initiated and sustained inhibition against MC38 and CT26 progression in vivo, and these effects correlated to improved CD8+ T-cell infiltration and activity within a type 1–prone TME. Additionally, cytotoxic CD8+ T cells from REG + bsAb–sensitized mice exhibited heightened tumor cell reactivity compared with animals treated with either agent alone. Therefore, the immunomodulatory benefits of REG can be effectively paired with a bsAb that anchors to colorectal cancer cells, diminishes immunosuppression (through PD-L1 blockade), and activates/sustains antigen-specific CD8+ T cells within the TME. Our newly described REG + bsAb regimen led to improved antitumor outcomes preclinically and may represent a promising future approach for patients with colorectal cancer.

Pulmonary lymphangioleiomyomatosis (LAM) is a metastatic sarcoma, but the mechanisms of LAM metastasis are unknown. Extracellular vesicles (EVs) regulate cancer metastasis; however, their roles in LAM have not yet been thoroughly investigated. Here, we report the discovery of distinct LAM-EV subtypes derived from primary tumor or metastasizing LAM cells that promote LAM metastasis through ITGα6/β1-c-Src-FAK signaling, triggered by the shuttling of ATP synthesis to cell pseudopodia or the activation of integrin adhesion complex, respectively. This signaling leads to increased LAM cell migration, invasiveness, and stemness and regulates metastable (hybrid) phenotypes that are all pivotal for metastasis. Mouse models corroborate in vitro data by demonstrating a significant increase in lung metastatic burden upon exposure to EVs through distinct mechanisms involving either lung resident fibroblasts or metalloproteinases' activation that are EV subtype dependent. The clinical relevance of these findings is underscored by increased EV biogenesis in LAM patients and the enrichment of these EV cargo with lung-tropic integrins and metalloproteinases. These findings establish EVs as a novel therapeutic target in LAM, warranting future clinical studies.

Supplementary Table 1 annotates sequences for the bsAb VH/VL.

Supplementary Figure 9 confirms abscopal tumor effects after local REG/bsAb treatment.