b1-integrin binding and lysosome targeting aptamer homes to triple-negative breast cancer in mice

Targeted therapies for triple-negative breast cancer have increased the number of available treatment options for patients. However, an optimal treatment strategy is still an unmet medical need due to the lack of targetable biomarkers and tumour heterogeneity. Aptamers have high selectivity and specificity towards target proteins. Lower molecular weight, increased stability, less immunogenicity, and rapid tissue uptake make aptamers an attractive alternative to antibodies. Attempts to develop aptamer therapeutics have shown difficulties translating in vitro results to in vivo. Aptamer GreenB1 exhibits selectivity to triple-negative MDA-MB-231 human breast cancer cell line in vitro compared to estrogen, progesterone, and glucocorticoid receptor-expressing MCF-7 human breast cancer cell line. The aptamer is rapidly internalised into cells and trafficked to lysosomes. Here, we identify 1-integrin as the target protein for GreenB1 using proximity labelling and mass spectrometry proteomics. GreenB1 homes preferentially to the tumour in the 4T1 triple-negative breast cancer mice model in vivo.