AUTHOR=O’Connell Emer , Reynolds Ian S. , Lindner Andreas U. , Salvucci Manuela , O’Grady Tony , Bacon Orna , Cho Sanghee , McDonough Elizabeth , Longley Daniel , Ginty Fiona , McNamara Deborah A. , Burke John P. , Prehn Jochen H. M. 

TITLE=Apoptotic and Necroptotic Mediators are Differentially Expressed in Mucinous and Non-Mucinous Colorectal Cancer

JOURNAL=Frontiers in Oncology

VOLUME=Volume 12 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/oncology/articles/10.3389/fonc.2022.815001

DOI=10.3389/fonc.2022.815001

ISSN=2234-943X

ABSTRACT=Background
Mucinous colorectal cancer (CRC) represents 10% of all CRC and is associated with chemotherapy resistance. Apoptosis and necroptosis pathways remain poorly understood in the mucinous subtype. 
Methods
Protein levels were analysed in SW1463 (mucinous rectal), SW837 (non-mucinous rectal), LS174T (mucinous colon) and HCT116 (non-mucinous colon) cell lines by western blot. Cell death was analysed by flow cytometry. RNA gene expression data were extracted from TCGA. Protein levels in mucinous and non-mucinous tumors were measured by multiplexed immunofluorescence.
Results 
Western blot of cell lines identified alterations in apoptosis proteins in mucinous CRC, most prominently downregulation of Bcl-xL protein levels (p=0.029) which was also observed at the mRNA level in patients by analysis of TCGA gene expression data (p<0.001). Bcl-xL reduction was accompanied by high basal levels of apoptosis in mucinous cell lines and in resected mucinous rectal tumors. Treatment with 5-FU did not significantly elevate cell death in mucinous cells, while non-mucinous cells showed robust cell death responses. However, 5-FU-induced phosphorylation of MLKL in mucinous cancer cells, suggestive of a switch to necroptotic cell death signaling. 
Conclusion
Distinctions between mucinous and non-mucinous CRC extend to cell death signaling with differential expression of mediators of the mitochondrial apoptosis and necroptosis pathways.