CXCR4 and head and neck squamous cell carcinoma: In addition, and according to the potent cytotoxicity (low nanomolar IC50) observed in vitro, repeated intravenous administration of each nanotoxin in a subcutaneous CXCR4+ HNSCC mouse model, induced a potent blockade of tumor growth, flattening the growth curves, especially for the T22-DITOX-H6 nanotoxin, in the absence of systemic toxicity or adverse effects.