Gastric cancer (GC) is one of the leading types of cancer in terms of mortality cases worldwide. Doxorubicin (Dox), a common chemotherapy drug, is frequently used to treat GC; however, acquired resistance to Dox hinders the chemotherapeutic outcome and causes shorter survival in GC patients. Several Dox‑resistant GC cell lines, including SGC7901, SNU‑1 and SNU‑5 were generated to investigate the mechanism of Dox resistance in GC. Various methods were used to test the response of Dox‑resistant GC cells and parental cells, including flow cytometry, Cell Counting kit‑8 assay, reverse transcription polymerase chain reaction and western blot analysis. In the present study, various Dox‑resistant cells presented reduced apoptosis and cell cycle arrest in response to Dox treatment. Western blot results revealed that cyclin D1 was upregulated in Dox‑resistant cells, whereas inhibition or depletion of cyclin D1 re‑sensitized the resistant cells to Dox treatment, which indicated that the induction of cyclin D1 expression was a result of the Dox resistance in GC cells. Furthermore, it was observed that a transcription activated form of p73 (TAp73), is the upstream modulator of cyclin D1, manipulating the cyclin D1 transcription with the assistance of activator protein 1 (AP‑1). Overall, the present study data provided a rational strategy to overcome the Dox resistance in GC treatment by inhibiting cyclin D1 expression.

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