Do lipid nanoparticles promote cancer metastasis in animal models, and what does the evidence show about mechanisms like neutrophil extracellular traps (NETs)?

The short version: the retrieved evidence does not test whether lipid nanoparticles promote cancer metastasis, and it contains no study of neutrophil extracellular traps (NETs) in relation to LNPs at all.

The evidence you asked for does not exist in these records. Every study that mentions LNPs and cancer is testing the LNP as a treatment delivery system, not asking whether the LNP itself drives metastasis. One 2021 study of bovine milk extracellular vesicles (not LNPs) found that oral administration accelerated metastasis in several mouse models while shrinking the primary tumor [6]. That is a different particle class, but it shows that a lipid-based nanocarrier can have opposite effects on primary tumor and metastasis depending on context. No study here examined whether an LNP alone, without a therapeutic payload, alters metastatic spread.

On NETs specifically, the retrieval contains three reviews and one experimental paper that establish NETs as a well-documented promoter of metastasis [1, 2, 3]. NETs trap circulating tumor cells, remodel the extracellular matrix, shield tumor cells from immune attack, and awaken dormant cells [1, 2]. One study showed that chemotherapy-induced NETs drive chemoresistance in ovarian cancer, and blocking NETs reversed it [5]. Another showed that surgical stress increases NET formation and accelerates liver metastases [4]. But none of these studies involve LNPs as the trigger. The question of whether LNPs themselves induce NETosis, and whether that NETosis then promotes metastasis, is simply not addressed in any record here.

The closest you get is the colloidal chemistry frame. LNPs are foreign particles injected into the bloodstream. The body's innate immune system, including neutrophils, responds to particulate matter. Neutrophils can release NETs in response to a wide range of stimuli: pathogens, crystals, cytokines, hypoxia, and physical stress [1, 2]. An LNP is a synthetic lipid particle with a surface charge and size that could plausibly trigger neutrophil activation. But plausible mechanism is not evidence. No study in this retrieval tested that mechanism.

My call: the evidence does not answer whether LNPs promote metastasis through NETs or any other pathway. The mechanism is plausible but unstudied in these records. Confidence: not clear.