Comprehensive Lipidome Profiling of Isogenic Primary and Metastatic Colon Adenocarcinoma Cell Lines

A “shotgun” lipidomics strategy consisting
of sequential
functional group selective chemical modification reactions coupled
with high-resolution/accurate mass spectrometry and “targeted”
tandem mass spectrometry (MS/MS) analysis has been developed and applied
toward the comprehensive identification, characterization and quantitative
analysis of changes in relative abundances of >600 individual glycerophospholipid,
glycerolipid, sphingolipid and sterol lipids between a primary colorectal
cancer (CRC) cell line, SW480, and its isogenic lymph node metastasized
derivative, SW620. Selective chemical derivatization of glycerophosphoethanolamine
and glycerophosphoserine lipids using a “fixed charge”
sulfonium ion containing, d6-S,S′-dimethylthiobutanoylhydroxysuccinimide ester (d6-DMBNHS) reagent was used to eliminate the possibility of
isobaric mass overlap of these species with the precursor ions of
all other lipids in the crude extracts, thereby enabling their unambiguous
assignment, while subsequent selective mild acid hydrolysis of plasmenyl
(vinyl-ether) containing lipids using formic acid enabled these species
to be readily differentiated from isobaric mass plasmanyl (alkyl-ether)
containing lipids. Using this approach, statistically significant
differences in the abundances of numerous lipid species previously
identified as being associated with cancer progression or that play
known roles as mediators in a range of physiological and pathological
processes were observed between the SW480 and SW620 cells. Most notably,
these included increased plasmanylcholine and triglyceride lipid levels,
decreased plasmenylethanolamine lipids, decreased C-16 containing
sphingomyelin and ceramide lipid levels, and a dramatic increase in
the abundances of total cholesterol ester and triglyceride lipids
in the SW620 cells compared to those in the SW480 cells.