Secreted Protein Acidic And Rich In Cysteine Research Articles

Secreted Protein Acidic and Rich in Cysteine (SPARC) to Manage Coronavirus Disease-2019 (COVID-19) Pandemic and the Post-COVID-19 Health Crisis

Coronavirus disease-2019 (COVID-19) has had and will have impacts on public health and health system expenses. Indeed, not only it has led to high numbers of confirmed COVID-19 cases and hospitalizations, but its consequences will remain even after the end of the COVID-19 crisis. Therefore, therapeutic options are required to both tackle the COVID-19 crisis and manage its consequences during the post COVID-19 era. Secreted protein acidic and rich in cysteine (SPARC) is a biomolecule that is associated with various properties and functions that situate it as a candidate which may be used to prevent, treat and manage COVID-19 as well as the post-COVID-19-era health problems. This paper highlights how SPARC could be of such therapeutic use.

Reverse-QTY code design of active human serum albumin self-assembled amphiphilic nanoparticles for effective anti-tumor drug doxorubicin release in mice

Human serum albumin (HSA) is a highly water-soluble protein with 67% alpha-helix content and three distinct domains (I, II, and III). HSA offers a great promise in drug delivery with enhanced permeability and retention effect. But it is hindered by protein denaturation during drug entrapment or conjugation that result in distinct cellular transport pathways and reduction of biological activities. Here we report using a protein design approach named reverse-QTY (rQTY) code to convert specific hydrophilic alpha-helices to hydrophobic to alpha-helices. The designed HSA undergo self-assembly of well-ordered nanoparticles with highly biological actives. The hydrophilic amino acids, asparagine (N), glutamine (Q), threonine (T), and tyrosine (Y) in the helical B-subdomains of HSA were systematically replaced by hydrophobic leucine (L), valine (V), and phenylalanine (F). HSArQTY nanoparticles exhibited efficient cellular internalization through the cell membrane albumin binding protein GP60, or SPARC (secreted protein, acidic and rich in cysteine)-mediated pathways. The designed HSArQTY variants displayed superior biological activities including: i) encapsulation of drug doxorubicin, ii) receptor-mediated cellular transport, iii) tumor cell targeting, and iv) antitumor efficiency compare to denatured HSA nanoparticles. HSArQTY nanoparticles provided superior tumor targeting and antitumor therapeutic effects compared to the albumin nanoparticles fabricated by antisolvent precipitation method. We believe that the rQTY code is a robust platform for specific hydrophobic modification of functional hydrophilic proteins with clear-defined binding interfaces.

TGF-β1 upregulates secreted protein acidic and rich in cysteine expression in human granulosa-lutein cells: a potential mechanism for the pathogenesis of ovarian hyperstimulation syndrome

BackgroundOvarian hyperstimulation syndrome (OHSS) is a serious complication during in vitro fertilization (IVF) treatment. The upregulation of ovarian transforming growth factor-beta 1 (TGF-β1) is involved in the development of OHSS. The secreted protein acidic and rich in cysteine (SPARC) is a secreted multifunctional matricellular glycoprotein. Although the regulatory effects of TGF-β1 on SPARC expression have been reported, whether TGF-β1 regulates SPARC expression in the human ovary remains unknown. In addition, the role of SPARC in the pathogenesis of OHSS is unclear.MethodsA steroidogenic human ovarian granulosa-like tumor cell line, KGN, and primary culture of human granulosa-lutein (hGL) cells obtained from patients undergoing IVF treatment were used as experimental models. OHSS was induced in rats, and ovaries were collected. Follicular fluid samples were collected from 39 OHSS and 35 non-OHSS patients during oocyte retrieval. The underlying molecular mechanisms mediating the effect of TGF-β1 on SPARC expression were explored by a series of in vitro experiments.ResultsTGF-β1 upregulated SPARC expression in both KGN and hGL cells. The stimulatory effect of TGF-β1 on SPARC expression was mediated by SMAD3 but not SMAD2. The transcription factors, Snail and Slug, were induced in response to the TGF-β1 treatment. However, only Slug was required for the TGF-β1-induced SPARC expression. Conversely, we found that the knockdown of SPARC decreased Slug expression. Our results also revealed that SPARC was upregulated in the OHSS rat ovaries and in the follicular fluid of OHSS patients. Knockdown of SPARC attenuated the TGF-β1-stimulated expression of vascular endothelial growth factor (VEGF) and aromatase, two markers of OHSS. Moreover, the knockdown of SPARC reduced TGF-β1 signaling by downregulating SMAD4 expression.ConclusionsBy illustrating the potential physiological and pathological roles of TGF-β1 in the regulation of SPARC in hGL cells, our results may serve to improve current strategies used to treat clinical infertility and OHSS.66JbE8YWJdrsTB-WmCj_-wVideo

Diosgenin restores memory function via SPARC-driven axonal growth from the hippocampus to the PFC in Alzheimer's disease model mice.

Central nervous system axons have minimal capacity to regenerate in adult brains, hindering memory recovery in Alzheimer's disease (AD). Although recent studies have shown that damaged axons sprouted in adult and AD mouse brains, long-distance axonal re-innervation to their targets has not been achieved. We selectively visualized axon-growing neurons in the neural circuit for memory formation, from the hippocampus to the prefrontal cortex, and showed that damaged axons successfully extended to their native projecting area in mouse models of AD (5XFAD) by administration of an axonal regenerative agent, diosgenin. In vivo transcriptome analysis detected the expression profile of axon-growing neurons directly isolated from the hippocampus of 5XFAD mice. Secreted protein acidic and rich in cysteine (SPARC) was the most expressed gene in axon-growing neurons. Neuron-specific overexpression of SPARC via adeno-associated virus serotype 9 delivery in the hippocampus recovered memory deficits and axonal projection to the prefrontal cortex in 5XFAD mice. DREADDs (Designer receptors exclusively activated by designer drugs) analyses revealed that SPARC overexpression-induced axonal growth in the 5XFAD mouse brain directly contributes to memory recovery. Elevated levels of SPARC on axonal membranes interact with extracellular rail-like collagen type I to promote axonal remodeling along their original tracings in primary cultured hippocampal neurons. These findings suggest that SPARC-driven axonal growth in the brain may be a promising therapeutic strategy for AD and other neurodegenerative diseases.

Clinicopathological and prognostic significance of SPARC expression in gastric cancer: A meta‑analysis and bioinformatics analysis.

Secreted protein acidic and rich in cysteine (SPARC) is a member of the extracellular matrix glycoprotein family that binds to calcium ions. It may bind to a variety of proteins in the extracellular matrix and also compete with cell membrane surface receptors for growth. In the present study, the relationship between SPARC expression in gastric cancer tissues and the clinicopathological characteristics and prognosis of patients with gastric cancer were systematically evaluated. A meta-analysis and bioinformatics analysis were performed using the PubMed, Chinese National Knowledge Infrastructure, Kaplan-Meier (KM)-plotter, The Cancer Genome Atlas (TCGA), Gene Expression Profiling Interactive Analysis (GEPIA), University of ALabama at Birmingham CANcer (UALCAN), Human Protein Atlas (HPA) and Timer databases. SPARC was mainly expressed in tumor mesenchymal cells. The meta-analysis indicated that SPARC expression was higher in gastric cancer tissues than in normal tissues. SPARC was associated with the degree of differentiation and distant metastasis. K-M plotter results indicated that high SPARC expression was negatively associated with overall survival, post-progression survival and progression-free survival rates of patients. According to the Oncomine, GEPIA, UALCAN and HPA databases, SPARC mRNA and protein expression was upregulated in gastric cancer vs. normal tissues and was negatively associated with poor patient prognosis. In the TCGA database, univariate analysis indicated that lymph node metastasis and distant metastasis were associated with the prognosis of patients with gastric cancer. Cox multifactorial analysis suggested that high SPARC expression, age and distant metastasis were important factors affecting the survival time of patients with gastric cancer. Analysis with the Timer database indicated that SPARC was closely associated with the proportion of 7 immune-cell infiltrates in gastric cancer. These findings indicated that high expression of SPARC may be a potential marker of tumorigenesis and metastasis in patients with gastric cancer.

Abstract 2101: Cancer-associated fibroblast activation predicts progression, metastasis, and prognosis of cutaneous squamous cell carcinoma

Abstract Purpose: Cutaneous squamous cell carcinoma (cSCC) is the most common metastatic skin cancer and the metastatic disease is associated with poor prognosis. At present, no established biomarkers are available for predicting the metastasis risk and prognosis of patients with cSCC. Cancer-associated fibroblasts (CAFs) promote the progression of cancer, but their role in cSCC is largely unknown. Here, we have examined the potential of CAF markers in the assessment of metastasis risk and prognosis of primary cSCC. Experimental Design: We utilized multiplexed fluorescence immunohistochemistry for profiling of CAF landscape in metastatic and non-metastatic primary human cSCCs, the actual metastases, and in premalignant and benign epidermal lesions. Quantitative high-resolution image analysis was performed with two separate panels of antibodies for CAF markers and the results were correlated with clinical and histopathological parameters including disease-specific mortality. Results: Increased stromal expression of fibroblast activation protein (FAP), α-smooth muscle actin, and secreted protein acidic and rich in cysteine (SPARC) were associated with progression of premalignant epidermal lesions to invasive cSCC. Furthermore, elevation of FAP and platelet-derived growth factor receptor-β (PDGFRβ) expression was associated with the risk of metastasis of primary cSCCs. High expression of PDGFRβ and periostin correlated with poor prognosis. Furthermore, a multi-marker defined CAF subset, PDGFRα-/PDGFRβ+/FAP+, was associated with invasion and metastasis and independently predicted poor disease-specific survival. Conclusions: These results show, that fibroblast activation evolves during the progression of cSCC. High PDGFRβ expression alone and multimarker combination PDGFRα-/PDGFRβ+/FAP+ are potential biomarkers for the progression of primary cSCC to metastatic stage, and for poor prognosis. Citation Format: Jaakko S. Knuutila, Pilvi Riihilä, Liisa Nissinen, Roosa Kallionpää, Teijo Pellinen, Veli-Matti Kähäri. Cancer-associated fibroblast activation predicts progression, metastasis, and prognosis of cutaneous squamous cell carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2101.

Abstract 6249: Low Bcl-2 is a robust biomarker of sensitivity to nab-paclitaxel in Ewing sarcoma

Abstract Nanoparticle albumin-bound paclitaxel (nab-paclitaxel) shows potent preclinical anticancer activity in pediatric solid tumors such as Ewing sarcoma, rhabdomyosarcoma and neuroblastoma, but responses in clinical trials have been modest. In this work, we aimed to discover a rational biomarker-based approach to select the right candidate patients for this treatment. We assessed the efficacy of nab-paclitaxel in 27 patient-derived xenografts (PDX), including 14 Ewing sarcomas, five rhabdomyosarcomas and several other pediatric solid tumors. Response rate (partial or complete response) was remarkable in rhabdomyosarcomas (four of five) and Ewing sarcomas (four of 14). We addressed several predictive factors of response to nab-paclitaxel such as the expression of the secreted protein acidic and rich in cysteine (SPARC), chromosomal stability of cancer cells and expression of antiapoptotic members of the B-cell lymphoma-2 (Bcl-2) family of proteins such as Bcl-2, Bcl-xL, Bcl-W and Mcl-1. Protein (immunoblotting) and gene expression of SPARC correlated positively, while immunoblotting and immunohistochemistry expression of Bcl-2 correlated negatively with the efficacy of nab-paclitaxel in Ewing sarcoma PDX. The negative correlation of Bcl-2 immunoblotting signal and activity was especially robust (r = 0.8352; P = 0.0007; Pearson correlation). Consequently, we evaluated pharmacological strategies to inhibit Bcl-2 during nab-paclitaxel treatment. We observed that the Bcl-2 inhibitor venetoclax improved the activity of nab-paclitaxel in highly resistant Bcl-2-expressing Ewing sarcoma PDX. Overall, our results suggest that low Bcl-2 expression could be used to select patients with Ewing sarcoma sensitive to nab-paclitaxel, and Bcl-2 inhibitors could improve the activity of this drug in Bcl-2-expressing Ewing sarcoma. Citation Format: Guillem Pascual-Pasto, Claudia Resa-Pares, Angel M. Carcaboso. Low Bcl-2 is a robust biomarker of sensitivity to nab-paclitaxel in Ewing sarcoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6249.

Hsa_circ_0017842 acts as a competing endogenous RNA to enhance the malignancy of gastric cancer.

Circular RNAs (circRNAs) have been shown to act as competing endogenous RNAs (ceRNAs) participating in the progression of gastric cancer (GC). Our study aimed to investigate whether hsa_circ_0017842 can affect the malignancy of GC in a ceRNA manner. Gene expression microarrays from GEO DataSets database, quantitative real-time polymerase chain reaction (qPCR) and western blotting were used to identify the expression levels of hsa_circ_0017842, miR-1294, and secreted protein, acidic and rich in cysteine (SPARC) in GC. The function of hsa_circ_0017842/miR-1294/SPARC axis in GC cells was confirmed using gainand loss-of-function assays. In addition, luciferase and RNA pulldown assays were performed to demonstrate the ceRNA mechanism of hsa_circ_0017842 involving miR-1294 and SPARC. The upregulation of hsa_circ_0017842 and SPARC, and downregulation of miR-1294 were observed in GC. Upregulating hsa_circ_0017842 in GC cells led to an increase in their proliferation, migration and invasion, and hsa_circ_0017842 knockdown showed the opposite effects on GC cells. Moreover, hsa_circ_0017842 was shown to be a sponge for miR-1294, thereby regulating SPARC expression. Due to the targeting relationship among hsa_circ_0017842, miR-1294 and SPARC, SPARC knockdown could relieve the effect of hsa_circ_0017842 overexpression on GC cells. Overall, this study confirmed that hsa_circ_0017842 acted as a ceRNA to promote the malignancy of GC cells through regulating the miR-1294/SPARC axis. Our findings might help better elucidate the molecular mechanism of GC tumorigenesis, and as a result improve the overall survival of GC patients.

Secreted Protein Acidic and Rich in Cysteine (SPARC)—Mediated Exercise Effects: Illustrative Molecular Pathways against Various Diseases

The strong benefits of exercise, in addition to the development of both the therapeutic applications of physical activity and molecular biology tools, means that it has become very important to explore the underlying molecular patterns linking exercise and its induced phenotypic changes. Within this context, secreted protein acidic and rich in cysteine (SPARC) has been characterized as an exercise-induced protein that would mediate and induce some important effects of exercise. Herein, we suggest some underlying pathways to explain such SPARC-induced exercise-like effects. Such mechanistic mapping would not only allow us to understand the molecular processes of exercise and SPARC effects but would also highlight the potential to develop novel molecular therapies. These therapies would be based on mimicking the exercise benefits via either introducing SPARC or pharmacologically targeting the SPARC-related pathways to produce exercise-like effects. This is of a particular importance for those who do not have the ability to perform the required physical activity due to disabilities or diseases. The main objective of this work is to highlight selected potential therapeutic applications deriving from SPARC properties that have been reported in various publications.

Plasma SPARC Elevation in Delayed Cerebral Ischemia After Aneurysmal Subarachnoid Hemorrhage.

Matricellular proteins have been implicated in pathologies after subarachnoid hemorrhage (SAH). To find a new therapeutic molecular target, the present study aimed to clarify the relationships between serially measured plasma levels of a matricellular protein, secreted protein acidic and rich in cysteine (SPARC), and delayed cerebral ischemia (DCI) in 117 consecutive aneurysmal SAH patients with admission World Federation of Neurological Surgeons (WFNS) grades I-III. DCI developed in 25 patients with higher incidences of past history of hypertension and dyslipidemia, preoperative WFNS grade III, modified Fisher grade 4, spinal drainage, and angiographic vasospasm. Plasma SPARC levels were increased after SAH, and significantly higher in patients with than without DCI at days 7-9, and in patients with VASOGRADE-Yellow compared with VASOGRADE-Green at days 1-3 and 7-9. However, there were no relationships between plasma SPARC levels and angiographic vasospasm. Receiver-operating characteristic curves differentiating DCI from no DCI determined the cut-off value of plasma SPARC ≥ 82.1ng/ml at days 7 - 9 (sensitivity, 0.800; specificity, 0.533; and area under the curve, 0.708), which was found to be an independent determinant of DCI development in multivariate analyses. This is the first study to show that SPARC is upregulated in peripheral blood after SAH, and that SPARC may be involved in the development of DCI without angiographic vasospasm in a clinical setting.

Albumin-binding photosensitizer capable of targeting glioma via the SPARC pathway

BackgroundMalignant glioma is among the most lethal and frequently occurring brain tumors, and the average survival period is 15 months. Existing chemotherapy has low tolerance and low blood-brain barrier (BBB) permeability; therefore, the required drug dose cannot be accurately delivered to the tumor site, resulting in an insufficient drug effect.MethodsHerein, we demonstrate a precision photodynamic tumor therapy using a photosensitizer (ZnPcS) capable of binding to albumin in situ, which can increase the permeability of the BBB and accurately target glioma. Albumin-binding ZnPcS was designed to pass through the BBB and bind to secreted protein acidic and rich in cysteine (SPARC), which is abundant in the glioma plasma membrane.ResultsWhen the upper part of a mouse brain was irradiated using a laser (0.2 W cm− 2) after transplantation of glioma and injection of ZnPcS, tumor growth was inhibited by approximately 83.6%, and the 50% survival rate of the treatment group increased by 14 days compared to the control group. In glioma with knockout SPARC, the amount of ZnPcS entering the glioma was reduced by 63.1%, indicating that it can target glioma through the SPARC pathway.ConclusionThis study showed that the use of albumin-binding photosensitizers is promising for the treatment of malignant gliomas.Graphical

Data-Independent Acquisition Mass Spectrometry of EPS-Urine Coupled to Machine Learning: A Predictive Model for Prostate Cancer.

Prostate cancer (PCa) is annually the most frequently diagnosed cancer in the male population. To date, the diagnostic path for PCa detection includes the dosage of serum prostate-specific antigen (PSA) and the digital rectal exam (DRE). However, PSA-based screening has insufficient specificity and sensitivity; besides, it cannot discriminate between the aggressive and indolent types of PCa. For this reason, the improvement of new clinical approaches and the discovery of new biomarkers are necessary. In this work, expressed prostatic secretion (EPS)-urine samples from PCa patients and benign prostatic hyperplasia (BPH) patients were analyzed with the aim of detecting differentially expressed proteins between the two analyzed groups. To map the urinary proteome, EPS-urine samples were analyzed by data-independent acquisition (DIA), a high-sensitivity method particularly suitable for detecting proteins at low abundance. Overall, in our analysis, 2615 proteins were identified in 133 EPS-urine specimens obtaining the highest proteomic coverage for this type of sample; of these 2615 proteins, 1670 were consistently identified across the entire data set. The matrix containing the quantified proteins in each patient was integrated with clinical parameters such as the PSA level and gland size, and the complete matrix was analyzed by machine learning algorithms (by exploiting 90% of samples for training/testing using a 10-fold cross-validation approach, and 10% of samples for validation). The best predictive model was based on the following components: semaphorin-7A (sema7A), secreted protein acidic and rich in cysteine (SPARC), FT ratio, and prostate gland size. The classifier could predict disease conditions (BPH, PCa) correctly in 83% of samples in the validation set. Data are available via ProteomeXchange with the identifier PXD035942.

Albumin-Based Silibinin Nanocrystals Targeting Activated Hepatic Stellate Cells for Liver Fibrosis Therapy

Activated hepatic stellate cells (aHSCs) are critical during the development and progression of liver fibrosis. Once liver fibrosis occurs, aHSCs highly express secreted protein, acidic and rich in cysteine (SPARC), a typical albumin-binding protein. We designed a nano platform, silibinin albumin nanocrystals (SLB-HSA NCs), to target aHSCs for liver fibrosis therapy. The prepared SLB-HSA NCs showed uniform particle size distribution of approximately 60 nm with PDI < 0.15 and high loading efficiency up to 49.4%. Albumin coated on the surface of nanocrystals was demonstrated to increase cellular uptake by aHSCs through SPARC-mediated endocytosis. In addition, SLB-HSA NCs significantly improved the bioavailability compared with free SLB in pharmacokinetic study. Following tail-vein injection, SLB-HSA NCs were massively accumulated in the fibrotic liver and exhibited enhanced antifibrotic effects in hepatic fibrosis mice. Overall, our findings prove the great potential of SLB-HSA NCs in the targeted treatment of liver fibrosis.

Abstract B006: Investigating the role of soluble metabolites in primary high grade serous ovarian cancer

Abstract Ovarian cancer is the fifth leading cause of cancer death in women. High grade serous ovarian cancer (HGSOC), the most common and lethal histotype, can originate from fallopian tube epithelial (FTE) cells. Research has not historically focused on the metabolites involved in the migration of transformed FTE cells from the fallopian tube to the ovary. Co-culture of murine FTE and ovaries enabled identification of several significantly upregulated soluble metabolites via imaging mass spectrometry (IMS), including norepinephrine (NE). Therefore, we set out to determine the effect of norepinephrine on FTE and ovarian cancer cell lines. Clinical data analysis revealed that human HGSOC cell lines express the β-adrenergic receptor through which norepinephrine signals, called ADRβ2, and HGSOC patients with increased ADRβ2 expression have worse survival outcomes (p&amp;lt;0.05), suggesting that signaling through ADRβ2 plays a role in HGSOC. When we examined phenotypic changes following NE treatment (10 µM), tumorigenic MOE PTENshRNA p53 cells showed increased invasion in a Boyden chamber (N≥3, p&amp;lt;0.05). Interestingly, in terms of mechanistic pathways, NE enhanced pSRC expression in MOE PTENshRNA p53 cells, which has been linked to invasion in the literature (N≥3, p&amp;lt;0.05). NE treatment also increased N-Cad and C-Myc expression, but did not cause any phenotypic changes, in OVCAR4 cells (N≥3, p&amp;lt;0.05). These data suggest that NE drives alterations in protein expression, which, depending on the cell line, may also induce oncogenic phenotypic changes. Given the above data, we also sought to understand the factors that drive ovarian NE release. Conditioned media from cultured MOE PTENshRNA cells was found to induce ovarian NE release. Further, we determined that only the protein fraction of this conditioned media (3-50kDa) was responsible for NE induction. Therefore, we conducted comparative proteomic analysis using non-tumorigenic tubal cells, MOE SCRshRNA, identifying a uniquely abundant protein potentially responsible for the NE release: SPARC (secreted protein acidic and rich in cysteine). Using our IMS/co-culture paradigm, we have seen that knockdown of SPARC in MOE PTENshRNA cells decreases levels of ovarian-derived NE and that overexpressing SPARC in MOE WT cells increases levels of ovarian-derived NE. To date, this work has identified two key molecules, NE and SPARC, involved in primary metastasis of HGSOC from fallopian tube to ovary. Future studies will focus on effects of blocking NE signaling in vivo and broadening our understanding of the role of SPARC in this signaling pathway. We are also studying effects of the other soluble metabolites identified in the initial IMS studies on ovarian cancer progression, including progesterone and testosterone. Ultimately, we hope that our integration of mass spectrometry techniques with phenotypic and mechanistic readouts will elucidate the signals involved in early ovarian cancer progression to enable more effective therapeutic targets for HGSOC. Citation Format: Tova M. Bergsten, Sarah Levy, Hannah Lusk, Laura Sanchez, Joanna E. Burdette. Investigating the role of soluble metabolites in primary high grade serous ovarian cancer [abstract]. In: Proceedings of the AACR Special Conference: Cancer Metastasis; 2022 Nov 14-17; Portland, OR. Philadelphia (PA): AACR; Cancer Res 2022;83(2 Suppl_2):Abstract nr B006.

SPARC is a decoy counterpart for c‑Fos and is associated with osteoblastic differentiation of bone marrow stromal cells by inhibiting adipogenesis.

Secreted protein acidic and rich in cysteine (SPARC), also called basement‑membrane protein 40 or osteonectin, is a matricellular protein that is abundant not only in bone tissue as a non‑collagenous protein but is also ubiquitously expressed in non‑calcified tissue. SPARC is located intracellularly and disruption of the Sparc gene has been reported to reduce bone formation and increase fat tissue; however, the mechanism by which SPARC inhibits adipogenesis remains unclear. The present study evaluated the intracellular function of SPARC in adipogenesis using the bone marrow stromal cell line ST2. When ST2 cells with low SPARC production were cloned, intrinsic activator protein‑1 (AP‑1) activity was markedly higher, mineralized nodule formation was significantly lower and lipid accumulation was significantly increased compared with in the parental ST2 cells. Forced expression of secreted SPARC with the signal peptide‑coding sequences of wild‑type Sparc or preprotrypsin in SPARC‑low ST2 cells significantly reduced AP‑1 transcription activity; however, these reductions were not observed in the absence of signal peptide sequences. Recombinant SPARC, produced using Brevibacillusbrevis, specifically bound to c‑Fos but not c‑Jun and inhibited the binding of c‑Fos/c‑Jun to a TPA‑response element sequence. These data suggested that SPARC was incorporated into the cells from the extracellular spaces and serves an intracellular role as a decoy counterpart for c‑Fos, as well as being associated with osteoblastogenesis through the inhibition of adipogenesis. These findings may provide new insights into regenerative medicine.

Imaging of Indocyanine Green-Human Serum Albumin (ICG-HSA) Complex in Secreted Protein Acidic and Rich in Cysteine (SPARC)-Expressing Glioblastoma.

Glioblastoma is the most common and fatal primary glioma and has a severe prognosis. It is a challenge for neurosurgeons to remove brain tumor tissues completely by resection. Meanwhile, fluorescence-guided surgery (FGS) is a technique used in glioma surgery to enhance the visualization of tumor edges to clarify the extent of tumor resection. Indocyanine green (ICG) is the only FDA-approved NIR fluorescent agent. It non-covalently binds to human serum albumin (HSA). Secreted protein acidic and rich in cysteine (SPARC) is an extracellular glycoprotein expressed in gliomas and binds to albumin, suggesting that it plays an important role in tumor uptake of the ICG-HSA complex. Here we demonstrate the binding properties of HSA or SPARC to ICG using surface plasmon resonance and saturation binding assay. According to in vitro and in vivo studies, the results showed that the uptake of ICG-HSA complex was higher in SPARC-expressing glioblastoma cell line and tumor region compared with the uptake of free ICG. Here, we visualized the SPARC-dependent uptake of ICG and ICG-HSA complex in U87MG. Our results demonstrated that the ICG-HSA complex is likely to be used as an efficient imaging agent targeting SPARC-expressing tumors, especially glioblastoma.

Low Bcl-2 is a robust biomarker of sensitivity to nab-paclitaxel in Ewing sarcoma

Nanoparticle albumin-bound paclitaxel (nab-paclitaxel) shows potent preclinical anticancer activity in pediatric solid tumors such as Ewing sarcoma, rhabdomyosarcoma and neuroblastoma, but responses in clinical trials have been modest. In this work, we aimed to discover a rational biomarker-based approach to select the right candidate patients for this treatment. We assessed the efficacy of nab-paclitaxel in 27 patient-derived xenografts (PDX), including 14 Ewing sarcomas, five rhabdomyosarcomas and several other pediatric solid tumors. Response rate (partial or complete response) was remarkable in rhabdomyosarcomas (four of five) and Ewing sarcomas (four of 14). We addressed several predictive factors of response to nab-paclitaxel such as the expression of the secreted protein acidic and rich in cysteine (SPARC), chromosomal stability of cancer cells and expression of antiapoptotic members of the B-cell lymphoma-2 (Bcl-2) family of proteins such as Bcl-2, Bcl-xL, Bcl-W and Mcl-1. Protein (immunoblotting) and gene expression of SPARC correlated positively, while immunoblotting and immunohistochemistry expression of Bcl-2 correlated negatively with the efficacy of nab-paclitaxel in Ewing sarcoma PDX. The negative correlation of Bcl-2 immunoblotting signal and activity was especially robust (r = 0.8352; P = 0.0007; Pearson correlation). Consequently, we evaluated pharmacological strategies to inhibit Bcl-2 during nab-paclitaxel treatment. We observed that the Bcl-2 inhibitor venetoclax improved the activity of nab-paclitaxel in highly resistant Bcl-2-expressing Ewing sarcoma PDX. Overall, our results suggest that low Bcl-2 expression could be used to select patients with Ewing sarcoma sensitive to nab-paclitaxel, and Bcl-2 inhibitors could improve the activity of this drug in Bcl-2-expressing Ewing sarcoma.

PS-BPB01-1: SPARC IS INDUCED AT THE EARLY STAGE OF VASCULAR ENDOTHELIAL DYSFUNCTION TO COMPENSATE INFLAMMATION IN DOCA-SALT HYPERTENSIVE RATS

Objective: Extracellular matrix (ECM) regulates various cellular functions as well as provides structural support. SPARC (secreted protein acidic and rich in cysteine) is one of the ECM components, which participates in various cellular functions, especially during morphogenesis and tissue remodeling. We have reported that 1) SPARC, which increases in accordance with renal injury, causes collagen deposition through ADAMTS1 (a disintegrin and metalloproteinase with thrombospondin type 1 motif) production, and 2) renin-angiotensin system is placed in the upstream of SPARC overexpression in the hypertensive rat kidney. The present study investigated the roles for SPARC in vascular endothelial cell dysfunction and inflammation in the setting of hypertension. Design and method: Rats were treated with deoxycorticosterone acetate (DOCA) and 1% salt water for 0, 1, 2 or 3 weeks. Blood pressure was measured by tail-cuff methods, and thoracic aorta was isolated to examine acetylcholine-induced vasodilatory response, macrophage infiltration by immunohistochemistry, and protein expression of SPARC and ADAMTS1 by Western blotting. In the separate experiment, angiotensin II (10–7mol/L, 6hr) or SPARC recombinant protein (100nmol/L, 24hr) was treated to cultured rat aortic endothelial cells (RAECs) with/without siRNA targeting SPARC and ADAMTS1. MCP-1 and LOX-1 mRNA levels were measured by real-time RT-PCR. Result: DOCA-salt caused time-dependent increases in systolic blood pressure, impairment of endothelium-dependent vasodilation, and macrophage infiltration into the adventitial area of the aorta. The expression of SPARC in the DOCA-salt rat aorta was enhanced at week1 and week2 compared to week0. ADAMTS1 expression tended to increase from week1 and showed significant increases at week3. In RAECs, SPARC and ADAMTS1 gene knockdown aggravated angiotensin II-induced overexpression of LOX-1 and MCP-1 mRNA, indicating anti-inflammatory effects of SPARC. On the other hand, SPARC recombinant protein treatment induced the upregulation of LOX-1 and MCP-1. Conclusions: SPARC may be induced at the early stage of vascular injury to compensate inflammation under the existence of angiotensin II. We need further investigation into the diverse effects of SPARC and the relationship between SPARC and ADAMTS1.

Serum CRP interacts with SPARC and regulate immune response in severe cases of COVID-19 infection.

Serum C-reactive protein (CRP) has been found elevated during COVID-19 infection, and associated with systematic inflammation as well as a poor clinical outcome. However, how did CRP participated in the COVID-19 pathogenesis remains poorly understood. Here, we report that serum C-reactive protein (CRP) levels are correlated with megakaryocyte marker genes and could regulate immune response through interaction with megakaryocytes. Molecular dynamics simulation through ColabFold showed a reliable interaction between monomeric form of CRP (mCRP) and the secreted protein acidic and rich in cysteine (SPARC). The interaction does not affect the physiological activities of SPARC while would be disturbed by pentamerization of CRP. Interplay between SPARC and mCRP results in a more intense immune response which may led to poor prognosis. This study highlights the complex interplay between inflammatory markers, megakaryocytes, and immune regulation in COVID-19 and sheds light on potential therapeutic targets.

Chronic spinal cord compression associated with intervertebral disc degeneration in SPARC-null mice.

Chronic spinal cord compression (CSCC) is induced by disc herniation and other reasons, leading to movement and sensation dysfunction, with a serious impact on quality of life. Spontaneous disc herniation rarely occurs in rodents, and therefore establishing a chronic spinal cord compression (CSCC) animal model is of crucial importance to explore the pathogenesis and treatment of CSCC. The absence of secreted protein, acidic, and rich in cysteine (SPARC) leads to spontaneous intervertebral disc degeneration in mice, which resembles human disc degeneration. In this study, we evaluated whether SPARC-null mice may serve as an animal model for CSCC. We performed rod rotation test, pain threshold test, gait analysis, and Basso Mouse Scale score. Our results showed that the motor function of SPARC-null mice was weakened, and magnetic resonance images revealed compression at different spinal cord levels, particularly in the lumbar segments. Immunofluorescence staining and western blot assay showed that the absence of SPARC induced apoptosis of neurons and oligodendrocytes, activation of microglia/macrophages with M1/M2 phenotype and astrocytes with A1/A2 phenotype; it also activated the expression of the NOD-like receptor protein 3 inflammasome and inhibited brain-derived neurotrophic factor/tyrosine kinase B signaling pathway. Notably, these findings are characteristics of CSCC. Therefore, we propose that SPARC-null mice may be an animal model for studying CSCC caused by disc herniation.