RAD23B Promotes The Occurrence And Development Of Lung Cancer By Reducing Polyunsaturated Fatty Acid Levels Through PTPLAD

Lung cancer is one of the most common malignancies.Every year,there are nearly 2.2 million new cases of lung cancer are diagnosed worldwide and 1.76 million lung cancer-related deaths occur.Searching and determing specific molecular targets can provide more strategies for the diagnosis,treatment and prognosis of lung cancer through mechanistic exploration of lung cancer development.We found that RAD23B expression in lung cancer cells was generally higher than normal lung epithelial cells.Functional analysis confirmed that RAD23B could significantly improve the viability and proliferation of lung cancer cells in vitro and promote the tumorigenesis and development of lung cancer in vivo.Furthermore,LC-MS/MS was used to detect the expression profile of proteins after RAD23B overexpression in lung cancer cells,and a total of 1886 proteins were identified,among which 403 proteins showed significant differences.Bioinformatics analysis showed that part of the differentially expressed proteins were enriched in fatty acid metabolism related pathways.Forty kinds of medium and long chain fatty acids were then quantitatively detected by GC-MS,of which,the level of eleven medium and long chain fatty acids were found negatively correlated with RAD23B,including seven polyunsaturated fatty acids(PUFA),such as arachidonic acid(AA)and adrenic acid(AdA).Furthermore,RAD23B reduced lipid peroxidation and increased lung cancer cell resistance to ferroptosis by decreasing AA and AdA,In order to explore the molecular mechanism of RAD23B affecting PUFA and ferroptosis in lung cancer cells,the potential interacting proteins of RAD23B were enriched by immunoprecipitation and identified by LC-MS/MS,a total of 632 potential interacting proteins were identified.Interaction of RAD23B with PTPLAD1,a protein involving the synthesis of PUFA,was confirmed by co-immunoprecipitation.Moreover,RAD23B negatively regulated PTPLAD1 protein level,but had no effect on HADC(PTPLAD1 encoding gene)mRNA level.Further analysis on the molecular mechanism of RAD23B regulating PTPLAD1 showed that RAD23B increased PTPLAD1 binding to proteasome subunit PSMD6 and accelerated PTPLAD1 degradation without affecting PTPLAD1 ubiquitination level.When knocking down the expression of PTPLAD1,the levels of AdA were decreased in lung cancer cell.Supplemented with AdA and in PTPLAD1 overexpression lung cancer cells enhanced lipid peroxidation and resistance to ferroptosis,and AdA in PTPLAD1 silent lung cancer cells increased lipid peroxidation and decreased resistance to ferroptosis in lung cancer cells.Meanwhile,Overexpression of PTPLAD1 on the basis of overexpression of RAD23B can improve the lipid peroxidation level of lung cancer cells and reduce the resistance of RAD23B to ferroptosis of lung cancer cells.In conclusion,this study found that RAD23B reduced the levels of PUFA through negative regulation of PTPLAD1 and inhibited the lipid peroxidation level of lung cancer cells,thus improving the resistance to ferroptosis and promoting the viability of lung cancer cells and development of lung cancer.