Conditioned medium mimicking the tumor microenvironment augments chemotherapeutic resistance via ataxia‑telangiectasia mutated and nuclear factor‑κB pathways in gastric cancer cells.

The tumor microenvironment affects the processes involved in the development of gastric cancer and contributes to multidrug resistance (MDR). Although the metabolism of gastric cancer cells is known to be associated with the development of the tumor microenvironment, the exact role of metabolism in microenvironment‑induced MDR formation remains unclear. In the present study, conditioned medium (CM) formed through the metabolism of SGC‑7901 gastric carcinoma cells was used to mimic the tumor microenvironment. The effects of CM on drug resistance were evaluated in gastric carcinoma cells. The results revealed that CM was not only able to upregulate the expression levels of ATP‑binding cassette subfamily G member 2 (ABCG2) and MDR‑associated protein 2 (MRP2), but also upregulated the expression of certain anti‑apoptotic proteins in SGC‑7901 cells. In addition, CM activated the ataxia‑telangiectasia mutated (ATM) and NF‑κB pathways, while CM‑induced ABCG2, MRP2 and anti‑apoptotic protein upregulation was impaired by ATM and NF‑κB inhibitors. The results of the present study indicated that CM augmented chemotherapeutic resistance by activating the ATM and NF‑κB pathways in gastric cancer cells, and that these pathways may be potential therapeutic targets for cases of chemotherapeutic resistance in gastric cancer.