Silencing NOB1 enhances doxorubicin antitumor activity of the papillary thyroid carcinoma in vitro and in vivo.

Doxorubicin (DOX), a broad‑spectrum anthra-cyclin, is in wide clinical use for the treatment and prevention of thyroid cancer. However, the effectiveness of the treatment remains limited due to inherent tumor resistance to DOX. Results of a previous study demonstrated that downregulation of NIN1/RPN12 binding protein 1 homolog (NOB1) expression via adenovirus expression vector carrying NOB1 siRNA (Ad/sh-NOB1) induced cancer apoptosis and increased the radiosensitivity of papillary thyroid carcinoma (PTC) cells. However, whether knockout NOB1 can decrease DOX resistance remains unclear. Therefore, in the present study, the effect of Ad/sh-NOB1 infection, independently or in combination with DOX, was determined in a PTC cell line to identify more effective therapeutics against PTC cancer. Furthermore, tumor growth ability in nude mice was determined to identify the combination treatment effect in tumorigenesis in vivo. The results showed that Ad/sh-NOB1 combined with DOX treatment in PTC cells significantly suppressed proliferation, colony formation, migration and invasion, and induced cell apoptosis and arrest in the G0/G1 stage as compared to Ad/sh-NOB1 or DOX monotherapy. We also found that this combination suppressed the tumor growth of a nude mouse model as compared to Ad/sh-NOB1 or DOX monotherapy. In addition, Ad/sh-NOB1 combined with DOX treatment significantly increased activation of the p38 MAPK pathway, which may contribute to inhibition of PTC cell growth and decreased DOX resistance. Taken together, the experimental results indicate that Ad/sh-NOB1 combined with DOX treatment is a potential drug candidate for the treatment of papillary thyroid carcinoma.