Acidosis-Induced Changes in Proteome Patterns of the Prostate Cancer-Derived Tumor Cell Line AT‑1

Under
various pathological conditions, such as inflammation, ischemia
and in solid tumors, physiological parameters (local oxygen tension
or extracellular pH) show distinct tissue abnormalities (hypoxia and
acidosis). For tumors, the prevailing microenvironment exerts a strong
influence on the phenotype with respect to proliferation, invasion,
and metastasis formation and therefore influences prognosis. In this
study, we investigate the impact of extracellular metabolic acidosis
(pH 7.4 versus 6.6) on the proteome patterns of a prostate cancer-derived
tumor cell type (AT-1) using isobaric labeling and LC–MS/MS
analysis. In total, 2710 proteins were identified and quantified across
four biological replicates, of which seven were significantly affected
with changes >50% and used for validation. Glucose transporter
1 and
farnesyl pyrophosphatase were found to be down-regulated after 48
h of acidic treatment, and metallothionein 2A was reduced after 24
h and returned to control values after 48 h. After 24 and 48 h at
pH 6.6, glutathione S transferase A3 and NAD­(P)H dehydrogenase 1,
cellular retinoic acid-binding protein 2, and Na-bicarbonate transporter
3 levels were found to be increased. The changes in protein levels
were confirmed by transcriptome and functional analyses. In addition
to the experimental in-depth investigation of proteins with changes
>50%, functional profiling (statistical enrichment analysis) including
proteins with changes >20% revealed that acidosis upregulates GSH
metabolic processes, citric acid cycle, and respiratory electron transport.
Metabolism of lipids and cholesterol biosynthesis were downregulated.
Our data comprise the first comprehensive report on acidosis-induced
changes in proteome patterns of a tumor cell line.