The isolation and identification of apolipoprotein C-I in hormone-refractory prostate cancer using surface-enhanced laser desorption/ionization time-of-flight mass spectrometry

Androgens play a central role in prostate cancer pathogenesis, and hence most of the patients respond to androgen deprivation therapies. However, patients tend to relapse with aggressive prostate cancer, which has been termed as hormone refractory. To identify the proteins that mediate progression to the hormone-refractory state, we used protein-chip technology for mass profiling of patients＇ sera. This study included 16 patients with metastatic hormone-refractory prostate cancer who were initially treated with androgen deprivation therapy. Serum samples were collected from each patient at five time points： point A, pre-treatment; point B, at the nadir of the prostate- specific antigen （PSA） level; point C, PSA failure; point D, the early hormone-refractory phase; and point E, the late hormone-refractory phase. Using surface-enhanced laser desorption/ionization time-of-flight mass spectrometry, we performed protein mass profiling of the patients＇ sera and identified a 6 640-Da peak that increased with disease progression. Target proteins were partially purified, and by amino acid sequencing the peak was identified as a fragment of apolipoprotein C-I （ApoC-I）. Serum ApoC-I protein levels increased with disease progression. On immunohistochemical analysis, the ApoC-i protein was found localized to the cytoplasm of the hormone-refractory cancer cells. In this study, we showed an increase in serum ApoC-I protein levels in prostate cancer patients during their progression to the hormone-refractory state, which suggests that ApoC-I protein is related to progression of prostate cancer. However, as the exact role of ApoC-I in prostate cancer pathogenesis is unclear, further research is required.

Non-transmissible Sendai virus vector encoding c-myc suppressor FBP-interacting repressor for cancer therapy

AIM:To investigate a novel therapeutic strategy to target and suppress c-myc in human cancers using far up stream element(FUSE)-binding protein-interacting repressor(FIR).METHODS:Endogenous c-Myc suppression and apoptosis induction by a transient FIR-expressing vector was examined in vivo via a HA-tagged FIR(HA-FIR)expression vector.A fusion gene-deficient,non-transmissible,Sendai virus(SeV)vector encoding FIR cDNA,SeV/dF/FIR,was prepared.SeV/dF/FIR was examined for its gene transduction efficiency,viral dose dependency of antitumor effect and apoptosis induction in HeLa(cervical squamous cell carcinoma)cells and SW480(colon adenocarcinoma)cells.Antitumor efficacy in a mouse xenograft model was also examined.The molecular mechanism of the anti-tumor effect and c-Myc suppression by SeV/dF/FIR was examined using Spliceostatin A(SSA),a SAP155 inhibitor,or SAP155siRNA which induce c-Myc by increasing FIR△exon2 in HeLa cells.RESULTS:FIR was found to repress c-myc transcription and in turn the overexpression of FIR drove apoptosis through c-myc suppression.Thus,FIR expressing vectors are potentially applicable for cancer therapy.FIR is alternatively spliced by SAP155 in cancer cells lacking the transcriptional repression domain within exon 2(FIR△exon2),counteracting FIR for c-Myc protein expression.Furthermore,FIR forms a complex with SAP155 and inhibits mutual well-established functions.Thus,both the valuable effects and side effects of exogenous FIR stimuli should be tested for future clinical application.SeV/dF/FIR,a cytoplasmic RNA virus,was successfully prepared and showed highly efficient gene transduction in in vivo experiments.Furthermore,in nude mouse tumor xenograft models,SeV/dF/FIR displayed high antitumor efficiency against human cancer cells.SeV/dF/FIR suppressed SSA-activated c-Myc.SAP155 siRNA,potentially produces FIR△exon2,and led to c-Myc overexpression with phosphorylation at Ser62.HA-FIR suppressed endogenous c-Myc expression and induced apoptosis in HeLa and SW480 cells.A c-myc transcriptional suppressor FIR expressing SeV/dF/FIR showed high gene transduction efficiency with significant antitumor effects and apoptosis induction in HeLa and SW480 cells.CONCLUSION:SeV/dF/FIR showed strong tumor growth suppression with no significant side effects in an animal xenograft model,thus SeV/dF/FIR is potentially applicable for future clinical cancer treatment.

Cell-free synthesis of stable isotope-labeled internal standards for targeted quantitative proteomics

High-sensitivity mass spectrometry approaches using selected reaction monitoring(SRM)or multiple reaction monitoring(MRM)methods are powerful tools for targeted quantitative proteomics-based investigation of dynamics in specific biological systems.Both high-sensitivity detection of lowabundance proteins and their quantification using this technique employ stable isotope-labeled peptide internal standards.Currently,there are various ways for preparing standards,including chemical peptide synthesis,cellular protein expression,and cell-free protein or peptide synthesis.Cell-free protein synthesis(CFPS)or in vitro translation(IVT)systems in particular provide high-throughput and low-cost preparation methods,and various cell types and reconstituted forms are now commercially available.Herein,we review the use of such systems for precise and reliable protein quantification.