Proteomic Analysis of Two Metabolic Proteins with Potential to Translocate to Plasma Membrane Associated with Tumor Metastasis Development and Drug Targets

Metastasis
is the main cause for death of breast cancer patients.
However, the underlying mechanism is still poorly understood. Plasma
membrane (PM) proteins play a key role in various biological processes,
especially for cell migration. In this study, we used a set of well-characterized
mammary mouse cell lines, 67NR, 168FARN, 4T1, representing the metastatic
progression, to study the differentially expressed membrane proteins.
These proteins were analyzed by a linear ion trap tandem mass spectrometry
(LTQ-MS/MS) following cell surface biotinylation and streptavidin
purification. A total of 1667 membrane proteins were identified, out
of which 472 were characterized as differentially expressed with at
least 2-fold change and p-value < 0.01. Functional
clustering of the 472 proteins revealed that 178 of them were metabolic
proteins. Finally, we focused on two metabolic proteins, fatty acid
synthase (FASN) and NAD­(P)H steroid dehydrogenase-like protein (NSDHL),
which were validated by Western blot and immunofluorescence. We found
that FASN and NSDHL translocated to the plasma membrane from the intracellular
compartment, and their expressions increased from 67NR to 4T1. This
alteration of localization along with differential expressions might
be necessary for metastasis development. Potentially, FASN and NSDHL
could serve as drug targets in new antimetastasis therapy.