Purpose: To explore the role of HOTTIP in the development of esophageal cancer and the drug resistance.
Methods: Serum level of HOTTIP in esophageal cancer patients was detected by RT-PCR. After treatment with different concentrations of Adriamycin (ADM) in Eca109 cells for 24 h, IC50 was measured by MTT assay. Subsequently, Eca109 cells were treated with 0, 0.2, 0.4 or 0.8 μg/ml ADM, respectively, followed by extraction of extracellular vesicles (EVs). HOTTIP level in EVs was detected. In addition, Eca109 cells were pre-treated with EVs for 48 h, and different concentrations of ADM for another 24 h. IC50, cell cycle determination and relative levels of HOTTIP and ABCG2 were examined. Pearson correlation test was conducted to assess the correlation between levels of HOTTIP and ABCG2.
Results: Serum level of HOTTIP was higher in esophageal cancer patients. IC50 in ADM-treated Eca109 cells for 24 h was 0.43±0.02 μg/ml. EVs1-4 were respectively isolated from Eca109 cells treated with 0, 0.2, 0.4 or 0.8 μg/ml ADM for 24 h, respectively. HOTTIP remained the highest level in EVs4 than the other three groups. Notably, IC50 was much higher in Eca109 cells incubated with EVs4 than those treated with EVs1-3. EVs4 intervention in Eca109 cells for 48 h markedly increased the proliferation index (PI), and relative levels of HOTTIP and ABCG2 than the other three groups. HOTTIP displayed a positive correlation with ABCG2 in Eca109 cells.
Conclusions: HOTTIP is highly expressed in serum of esophageal cancer patients. EVs-containing HOTTIP regulates drug resistance in esophageal cancer by positively activating ABCG2.