Photothermal therapy with AuNRs and EGFRmAb-AuNRs inhibits subcutaneous transplantable hypopharyngeal tumors in nude mice.

The present study aimed to investigate the effects of photothermal therapy with gold nanorods (AuNRs) or epidermal growth factor receptor monoclonal antibody‑conjugated AuNRs (EGFRmAb‑AuNRs) on hypopharyngeal carcinoma (HC) in nude mice. In addition, the associated signaling pathways were explored. Briefly, a subcutaneous transplantable hypopharyngeal tumor model was established in nude mice injected with FaDu human HC cells. A total of 70 nude mice were randomly divided into seven groups, each of which received a different treatment. Mice were treated with AuNRs, locally or through intravenous injection, whereas EGFRmAb or EGFRmAb‑AuNRs were only administered locally. Near infrared spectroscopy (NIR) was also applied for plasmonic photothermal therapy (PPTT). The growth curve and the inhibitory rate for tumor growth were used to evaluate the effects of each treatment. Flow cytometry and the terminal‑deoxynucleotidyl transferase dUTP nick end labeling assay were adopted to detect apoptosis of cells in the transplanted tumors. Reverse transcription‑quantitative polymerase chain reaction and western blotting were used to determine the mRNA and protein expression levels of target genes, respectively. Local treatment with AuNRs + NIR or EGFRmAb significantly inhibited tumor growth, and EGFRmAb conjugation further increased the inhibitory effects. Furthermore, there was a significant increase in apoptosis of tumor cells in the AuNRs + NIR, EGFRmAb and EGFRmAb‑AuNRs + NIR groups; treatment with EGFRmAb‑AuNRs + NIR induced the highest apoptotic effect. Mechanistic studies indicated that EGFRmAb‑AuNRs + NIR may inhibit tumors through the AKT serine/threonine kinase (Akt) and DNA damage signaling pathways. In the AKT pathway, the mRNA and protein expression levels of phosphatase and tensin homolog were increased, whereas the expression levels of Akt and glycogen synthase kinase 3β were decreased. In the DNA damage signaling pathway, the mRNA and protein expression levels of ATR serine/threonine kinase, checkpoint kinase 1 and p53 were enhanced, whereas phosphorylated‑p53 protein expression was reduced. The present findings indicated that AuNRs + NIR inhibited HC tumor growth, and conjugating EGFRmAb to AuNRs further enhanced the inhibitory effects. EGFRmAb conjugation may increase the antitumor effects of AuNRs‑induced PPTT by downregulating the phosphatidylinositol‑3‑kinase/Akt pathway and upregulating the DNA damage pathway. These findings may provide novel insights into tumor‑targeting PPTT in vivo.