Yi Yang, Baijun Cheng, Xinghao Ai, Yi Zhao, Yongfeng Yu, Yunhua Xu, Xiangyun Ye, Hong Jian, Zhen Zhou, Zhiwei Chen,  Meilin Liao, Shun Lu, Yang Yi

Department of Oncology, Chest Hospital affiliated to Shanghai Jiaotong University

Objective:Rapid growth of tumor cells needs to consume large amounts of oxygen and glucose, due to lack of blood supply within the tumor, cells live in an environment that lack of oxygen and nutrients. This environment results in endoplasmic reticulum (ER) stress and activates the UPR (unfolded protein response). More and more evidence suggest UPR provides a growth signal pathway required for tumor growth. However, the relationship between XBP1, one transcription factor in UPR, and the expression of LOX remains unclear. The role of XBP1-LOX axis in ER stress-induced growth of tumor cells is still unknown. In the present study, we investigated the relationship between XBP1 and the expression of LOX. Method: Quantitive RT-PCR analysis was used to determine the relative expression levels of XBP1 and LOX. Cell viability was measured by the MTT assay. The wells in 48-well plates were coated with growth factor reduced BD Matrigel (BD Biosciences #356231) and allowed to polymerize. Luciferase reporter assay was performed to detect the relationship of XBP1 and LOX. Result: We found that ER stress induces high expression of XBP1, one transcription factor in UPR, in both 2D culture and 3D culture; but only promotes growth of lung adenocarcinoma cells in in vitro 3D culture other than 2D culture. In 3D culture, we further showed that knockdown XBP1 expression can block Tm/Tg-induced cell growth. LOX genes may be key downstream effector of XBP1. Knockdown LOX expression can partially block XBP1-induced cell growth. Then we showed XBP1 suppressed by RNAi can reduce the expression of LOX. Conclusion: For the first time, it is being shown that XBP1 can regulate the expression of LOX to promote cell growth.

Key Words: 3D culture  XBP1-LOX  lung adenocarcinoma