EGFR and squamous cell carcinoma: To determine whether PEG engagerEGFR can specifically deliver PEGylated nanoparticles into EGFR-positive cancer cells, we investigated cancer cell lines with different expression levels of EGFR, including MCF7 EGFR-negative non-TNBC breast adenocarcinoma cells, MDA-MB-468 EGFR-positive TNBC cells and A431 EGFR-positive epidermoid carcinoma cells.