PACE4 regulates apoptosis in human prostate cancer cells via endoplasmic reticulum stress and mitochondrial signaling pathways

PCSK6 and Survival in Idiopathic Pulmonary Fibrosis

Rationale: Idiopathic pulmonary fibrosis (IPF) is a devastating disease characterized by limited treatment options and high mortality. A better understanding of the molecular drivers of IPF progression is needed. Objectives: To identify and validate molecular determinants of IPF survival. Methods: A staged genome-wide association study was performed using paired genomic and survival data. Stage I cases were drawn from centers across the United States and Europe and stage II cases from Vanderbilt University. Cox proportional hazards regression was used to identify gene variants associated with differential transplantation-free survival (TFS). Stage I variants with nominal significance (P < 5 × 10-5) were advanced for stage II testing and meta-analyzed to identify those reaching genome-wide significance (P < 5 × 10-8). Downstream analyses were performed for genes and proteins associated with variants reaching genome-wide significance. Measurements and Main Results: After quality controls, 1,481 stage I cases and 397 stage II cases were included in the analysis. After filtering, 9,075,629 variants were tested in stage I, with 158 meeting advancement criteria. Four variants associated with TFS with consistent effect direction were identified in stage II, including one in an intron of PCSK6 (proprotein convertase subtilisin/kexin type 6) reaching genome-wide significance (hazard ratio, 4.11 [95% confidence interval, 2.54-6.67]; P = 9.45 × 10-9). PCSK6 protein was highly expressed in IPF lung parenchyma. PCSK6 lung staining intensity, peripheral blood gene expression, and plasma concentration were associated with reduced TFS. Conclusions: We identified four novel variants associated with IPF survival, including one in PCSK6 that reached genome-wide significance. Downstream analyses suggested that PCSK6 protein plays a potentially important role in IPF progression.

Proprotein Convertase Subtilisin/Kexin 6 in Cardiovascular Biology and Disease

Proprotein convertase subtilisin/kexin 6 (PCSK6) is a secreted serine protease expressed in most major organs, where it cleaves a wide range of growth factors, signaling molecules, peptide hormones, proteolytic enzymes, and adhesion proteins. Studies in Pcsk6-deficient mice have demonstrated the importance of Pcsk6 in embryonic development, body axis specification, ovarian function, and extracellular matrix remodeling in articular cartilage. In the cardiovascular system, PCSK6 acts as a key modulator in heart formation, lipoprotein metabolism, body fluid homeostasis, cardiac repair, and vascular remodeling. To date, dysregulated PCSK6 expression or function has been implicated in major cardiovascular diseases, including atrial septal defects, hypertension, atherosclerosis, myocardial infarction, and cardiac aging. In this review, we describe biochemical characteristics and posttranslational modifications of PCSK6. Moreover, we discuss the role of PCSK6 and related molecular mechanisms in cardiovascular biology and disease.

Pcsk6 Deficiency Promotes Cardiomyocyte Senescence by Modulating Ddit3-Mediated ER Stress

Cardiac aging is a critical determinant of cardiac dysfunction, which contributes to cardiovascular disease in the elderly. Proprotein convertase subtilisin/kexin 6 (PCSK6) is a proteolytic enzyme important for the maintenance of cardiac function and vascular homeostasis. To date, the involvement of PCSK6 in cardiac aging remains unknown. Here we report that PCSK6 expression decreased in the hearts of aged mice, where high levels cyclin dependent kinase inhibitor 2A (P16) and cyclin dependent kinase inhibitor 1A (P21) (senescence markers) were observed. Moreover, PCSK6 protein expression was significantly reduced in senescent rat embryonic cardiomyocytes (H9c2) induced by D-galactose. Pcsk6 knockdown in H9c2 cells increased P16 and P21 expression levels and senescence-associated beta-galactosidase activity. Pcsk6 knockdown also impaired cardiomyocyte function, as indicated by increased advanced glycation end products, reactive oxygen species level, and apoptosis. Overexpression of PCSK6 blunted the senescence phenotype and cellular dysfunction. Furthermore, RNA sequencing analysis in Pcsk6-knockdown H9c2 cells identified the up-regulated DNA-damage inducible transcript 3 (Ddit3) gene involved in endoplasmic reticulum (ER) protein processing. Additionally, DDIT3 protein levels were remarkably increased in aged mouse hearts. In the presence of tunicamycin, an ER stress inducer, DDIT3 expression increased in Pcsk6-deficient H9c2 cells but reduced in PCSK6-overexpressing cells. In conclusion, our findings indicate that PCSK6 modulates cardiomyocyte senescence possibly via DDIT3-mediated ER stress.

PACE4 Expression is a Novel Independent Prognostic Factor in Nasopharyngeal Carcinoma

Background

Paired basic amino acid-cleaving enzyme 4 (PACE4) belongs to the family of proprotein convertase and is essential for tumor progression, whereas its role in cancer remains controversial and little is known about its role in nasopharyngeal carcinoma (NPC). The aim of this study was to examine if the expression of PACE4 is a prognostic biomarker for patients with NPC.

Methods

Immunofluorescence (IF) and immunohistochemistry (IHC) were used to analyze PACE4 expression in NPC cell line CNE1 and 172 clinicopathologically characterized NPC tissues. The data were analyzed by Chi-square test, Kaplan–Meier plots, and Cox proportional hazards regression model.

Results

IF and IHC staining results showed that PACE4 was mainly located in the cytoplasm of NPC cell line (CNE1) and NPC tissues. Expression of PACE4 was observed in 46/172 (26.7%) of NPC tissues. Further analysis showed that expression of PACE4 was positively associated with late N stage, distant metastasis, and late clinical stage (P<0.05). High expression of PACE4 predicted shorter 5-year overall survival of patients with NPC, especially for the patients in advanced stage (32.7% vs 77.3%, P<0.001). Furthermore, multivariate analysis showed that PACE4 expression may serve as a potential prognostic factor for NPC.

Conclusion

Our results suggest that PACE4 may play a crucial role in tumor progression and may serve as a valuable prognostic biomarker for patients with NPC.

A functional polymorphism in the paired basic amino acid-cleaving enzyme 4 gene confers osteoarthritis risk in a population of Eastern China

Paired basic amino acid-cleaving enzyme 4 (PACE4), a proprotein convertase, is involved in the activation of aggrecanases (ADAMTS-4 and ADAMTS-5) in osteoarthritic and cytokine-stimulated cartilage. Activated aggrecanases cause aggrecan degradation and thus, contribute to osteoarthritis (OA). In this study, we investigated the association between PACE4 gene polymorphisms and OA risk. One single-nucleotide polymorphism (rs4965833) in the PACE4 gene was genotyped in 432 OA patients and 523 healthy controls using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Quantitative reverse transcription PCR (qRT-PCR) was used to determine the relative expression of PACE4 in blood samples from 90 OA patients (30 for each genotype). The relative expression level of PACE4 mRNA was higher in the GG genotype as compared to the AA/AG group. Moreover, the PACE4 rs4965833 polymorphism was associated with increased risk of OA, especially among individuals aged ≥55 years and with a body mass index ≥25. There was no significant association between the PACE4 rs4965833 polymorphism and clinical parameters of OA patients, such as erythrocyte sedimentation rate, C-reactive protein, Visual Analog Scale for pain and Lequesne’s index. In conclusion, the rs4965833 polymorphism in the 3’-UTR of PACE4 is associated with OA susceptibility.

Investigating isoquinoline derivatives for inhibition of inhibitor of apoptosis proteins for ovarian cancer treatment

Objective

To discover novel isoquinoline derivatives for inhibition of inhibitor of apoptosis proteins (IAP) for the treatment of ovarian cancer.

Methods

We first synthesized 533 isoquinoline derivatives, and screened them using CCK-8 to measure their antiproliferative activity. These compounds were further tested by Hoechst staining and flow cytometric analysis to assess proapoptotic activity. The in vivo antitumor efficacy and safety of the screened compounds were evaluated on the xenograft mouse model. Ki-67 staining and TUNEL assay were used to evaluate proliferation and apoptosis in the resected tumors, respectively. Western blot and polymerase chain reaction (PCR) were conducted to evaluate the levels of proliferating cell nuclear antigen (PCNA), caspase-3, PARP, and IAP in resected tumors.

Results

Compound B01002 and C26001 displayed antiproliferative and proapoptotic activity on SKOV3 ovarian cancer with an IC50 of 7.65 and 11.68 µg/mL, respectively. Both compounds inhibited tumor growth in a xenografted mouse model with good safety profiles, and tumor growth inhibition (TGI) of B01002 and C26001 was 99.53% and 84.23%, respectively. Resected tumors showed that both compounds inhibited tumor cell proliferation and induced apoptosis in vivo. Caspase-3 and PARP were activated, whereas IAP proteins were downregulated at the protein level.

Conclusion

Compound B01002 and C26001 could inhibit ovarian tumor growth and promote tumor apoptosis, partly by downregulating the IAPs, and, thus, might be promising candidates for treatment of ovarian cancer.

Prostate cancer and the unfolded protein response

The endoplasmic reticulum (ER) is an essential organelle that contributes to several key cellular functions, including lipogenesis, gluconeogenesis, calcium storage, and organelle biogenesis. The ER also serves as the major site for protein folding and trafficking, especially in specialized secretory cells. Accumulation of misfolded proteins and failure of ER adaptive capacity activates the unfolded protein response (UPR) which has been implicated in several chronic diseases, including cancer. A number of recent studies have implicated UPR in prostate cancer (PCa) and greatly expanded our understanding of this key stress signaling pathway and its regulation in PCa. Here we summarize these developments and discuss their potential therapeutic implications.