PYCR1 regulates TRAIL‑resistance in non‑small cell lung cancer cells by regulating the redistribution of death receptors.

Although recombinant human TNF-related apoptosis-inducing ligand (TRAIL) protein exhibits antitumor activity in a number of lung and liver cancer cells and tumor-bearing animals, TRAIL resistance has substantially restricted its clinical application. Pyrroline-5-carboxylate reductase 1 (PYCR1) is a key enzyme in the regulation of proline synthesis. PYCR1 is highly expressed in various types of malignant tumor, in which it has been implicated in 5-fluorouracil resistance. However, the possible relationship between PYCR1 and TRAIL resistance remains unclear. In the present study, both reverse transcription-quantitative PCR and western blotting were performed. The results indicated that H1299 cells had higher PYCR1 expression levels and were less sensitive to TRAIL compared with the TRAIL-sensitive cell line, H460. PYCR1 knockdown in H1299 cells increased TRAIL sensitivity, increased the localization of death receptors (DRs) on the cell surface and activated Caspase-3/8. By contrast, overexpression of PYCR1 in H1299 cells decreased TRAIL sensitivity, reduced the distribution of DRs on the cell surface and suppressed the activation of Caspase-3/8. Taken together, these results suggested that PYCR1 promoted TRAIL resistance in the non-small cell lung cancer cell line, H1299, by preventing redistribution of DRs to the plasma membrane. This in turn inhibited TRAIL-mediated cell apoptosis by reducing the activation of Caspase-3/8.