Proteome profiling of enzalutamide-resistant cell lines and serum analysis identified
ALCAM as marker of resistance in castration-resistant prostate cancer
Enzalutamide (ENZA) is a frequently used therapy in metastatic castration-resistant
prostate cancer (mCRPC). Baseline or acquired resistance to ENZA have been observed,
but the molecular mechanisms of resistance are poorly understood. We aimed to identify
proteins involved in ENZA resistance and to find therapy-predictive serum markers.
We performed comparative proteome analyses on ENZA-sensitive parental (LAPC4, DuCaP)
and -resistant prostate cancer cell lines (LAPC4-ENZA, DuCaP-ENZA) using liquid chromatography
tandem mass spectrometry (LC-MS/MS). The top 4 most promising candidate markers were
selected using bioinformatic approaches. Serum concentrations of selected markers
(ALCAM, AGR2, NDRG1, IDH1) were measured in pre-treatment samples of 72 ENZA-treated
mCRPC patients using ELISA. In addition, ALCAM serum levels were measured in 101 Abiraterone
(ABI) and 100 Docetaxel (DOC)-treated mCRPC patients' baseline samples. Results were
correlated with clinical and follow-up data. The functional role of ALCAM in ENZA
resistance was assessed in vitro using siRNA. Our proteome analyses revealed 731 significantly
differentially abundant proteins between ENZA-sensitive and -resistant cells and our
filtering methods identified 4 biomarker candidates. Serum analyses of these proteins
revealed only ALCAM to be associated with poor patient survival. Furthermore, higher
baseline ALCAM levels were associated with poor survival in ABI- but not in DOC-treated
patients. In LAPC4-ENZA resistant cells, ALCAM silencing by siRNA knockdown resulted
in significantly enhanced ENZA sensitivity. Our analyses revealed that ALCAM serum
levels may help to identify ENZA- and ABI-resistant patients and may thereby help
to optimize future clinical decision-making. Our functional analyses suggest the possible
involvement of ALCAM in ENZA resistance. This article is protected by copyright. All
rights reserved.