# NPRL2 is required for proliferation of oncogenic Ras-transformed bronchial epithelial cells

## TL;DR

NPRL2 is essential for the growth of lung cells transformed by oncogenic Ras, and its depletion causes cell stress and reduced survival.

## Contribution

This study identifies NPRL2 as a critical factor for the proliferation of Ras-transformed bronchial epithelial cells.

## Key findings

- NPRL2 depletion activates mTORC1 signaling and inhibits autophagy in transformed bronchial cells.
- NPRL2 depletion increases DNA damage and apoptosis markers, leading to cell cycle arrest and mitotic catastrophe.
- NPRL2 depletion suppresses cytoprotective pathways like HSF1 and NRF2 in Ras-transformed cells.

## Abstract

Nitrogen permease regulator-like 2 (NPRL2/TUSC4) is known to exert both tumor-suppressing and oncogenic effects in different types of cancers, suggesting that its actions are context dependent. Here, we delineated the molecular and functional effects of NPRL2 in malignantly transformed bronchial epithelial cells. To do so, we depleted NPRL2 in oncogenic HRas-transduced and malignantly transformed human bronchial epithelial (BEAS2B), Ras-AI-T2 cells. Intriguingly, depletion of NPRL2 in these cells induced activation of mTORC1 downstream signaling, inhibited autophagy, and impaired Ras-AI-T2 cell proliferation both in vitro and in vivo. These results suggest that NPRL2 is required for oncogenic HRas-induced cell transformation. Depletion of NPRL2 increased levels of the DNA damage marker γH2AX, the cell cycle inhibitors p21 and p27, and the apoptosis marker cleaved-PARP. These NPRL2-depleted cells first accumulated at G1 and G2, and later exhibited signs of mitotic catastrophe, which implied that NPRL2 depletion may be detrimental to oncogenic HRas-transformed cells. Additionally, NPRL2 depletion reduced heat shock factor 1/heat shock element- and NRF2/antioxidant response element-directed luciferase reporter activities in Ras-AI-T2 cells, indicating that NPRL2 depletion led to the suppression of two key cytoprotective processes in oncogenic HRas-transformed cells. Overall, our data suggest that oncogenic HRas-transduced and malignantly transformed cells may depend on NPRL2 for survival and proliferation, and depletion of NPRL2 also induces a stressed state in these cells.