The 'SPARC' of life: Analysis of the role of osteonectin/SPARC in pancreatic cancer (Review)

Emerging Role of Non-collagenous Bone Proteins as Osteokines in Extraosseous Tissues

Bone is a unique tissue, composed of various types of cells embedded in a calcified extracellular matrix (ECM), whose dynamic structure consists of organic and inorganic compounds produced by bone cells. The main inorganic component is represented by hydroxyapatite, whilst the organic ECM is primarily made up of type I collagen and non-collagenous proteins. These proteins play an important role in bone homeostasis, calcium regulation, and maintenance of the hematopoietic niche. Recent advances in bone biology have highlighted the importance of specific bone proteins, named "osteokines", possessing endocrine functions and exerting effects on nonosseous tissues. Accordingly, osteokines have been found to act as growth factors, cell receptors, and adhesion molecules, thus modifying the view of bone from a static tissue fulfilling mobility to an endocrine organ itself. Since bone is involved in a paracrine and endocrine cross-talk with other tissues, a better understanding of bone secretome and the systemic roles of osteokines is expected to provide benefits in multiple topics: such as identification of novel biomarkers and the development of new therapeutic strategies. The present review discusses in detail the known osseous and extraosseous effects of these proteins and the possible respective clinical and therapeutic significance.

SPOCK2 gene expression is downregulated in pancreatic ductal adenocarcinoma cells and correlates with prognosis of patients with pancreatic cancer

OBJECTIVES

Pancreatic ductal adenocarcinoma (PDAC) represents a widespread form of malignant pancreatic neoplasms and a leading oncologic cause of death in Europe and the USA. Despite advances in understanding its molecular biology, the 5-year survival rate remains low at 10%. The extracellular matrix in PDAC contains proteins, including SPOCK2, which are essential for tumorigenicity and drug resistance. The present study aims to explore the possible role of SPOCK2 in the pathogenesis of PDAC.

MATERIALS AND METHODS

Expression of SPOCK2 was evaluated in 7 PDAC cell lines and 1 normal pancreatic cell line using quantitative RT-PCR. Demethylation of the gene was carried out using 5-aza-2'-deoxycytidine (5-aza-dC) treatment with subsequent validation Western Blot analysis. In vitro downregulation of SPOCK2 gene was performed using siRNA transfection. MTT and transwell assays were employed to evaluate the impact of the SPOK2 demethylation on the proliferation and migration of PDAC cells. KM Plotter was applied to analyze a correlation between SPOCK2 mRNA expression and the survival of PDAC patients.

RESULTS

In contrast to the normal pancreatic cell line, SPOCK2 expression was significantly downregulated in PDAC cell lines. Treatment with 5-aza-dC, led to increase in SPOCK2 expression in the cell lines tested. Importantly, compared with control cells, transfected with SPOCK2 siRNA cells exhibited increased growth rates and more migration ability. Finally, we demonstrated that a high SPOCK2 expression level correlated with longer overall survival of patients with PDAC.

CONCLUSION

The expression of SPOCK2 is downregulated in PDAC as a result of hypermethylation of its corresponding gene. SPOCK2 expression as well as the demethylation of its gene could be a potential marker for PDAC.

SPARC expression in tumor microenvironment induces partial epithelial-to-mesenchymal transition of esophageal adenocarcinoma cells via cooperating with TGF-β signaling

Secreted protein, acidic and rich in cysteine (SPARC) has been characterized as an oncoprotein in esophageal squamous cell carcinoma (ESCC), but its involvement in the pathological development of esophageal adenocarcinoma (ESAD) remains poorly understood. In this study, we aimed to explore the sources of SPARC in the tumor microenvironment (TME) and its functional role in ESAD. Bioinformatic analysis was conducted using data from The Cancer Genome Atlas (TCGA)-esophageal cancer (ESCA) and Genotype-Tissue Expression (GTEx). ESAD tumor cell line OE33 and OE19 cells were used as in vitro cell models. Results showed that SPARC upregulation was associated with unfavorable disease-specific survival (DSS) in ESAD. ESAD tumor cells (OE33 and OE19) had no detectable SPARC protein expression. In contrast, IHC staining in ESAD tumor tissues suggested that peritumoral stromal cells (tumor-associated fibroblasts and macrophages) were the dominant SPARC source in TME. Exogenous SPARC induced partial epithelial-to-mesenchymal transition of ESAD cells, reflected by reduced CDH1 and elevated ZEB1/VIM expression at both mRNA and protein levels. Besides, exogenous SPARC enhanced tumor cell invasion. When TGFBR2 expression was inhibited, the activation of TGF-β signaling induced by exogenous SPARC was impaired. However, the activating effects were rescued by overexpressing mutant TGFBR2 resistant to the shRNA sequence. Copresence of exogenous SPARC and TGF-β1 induced higher expression of mesenchymal markers and enhanced the invading capability of ESAD cells than TGF-β1 alone. In conclusion, this study suggests a potential cross-talk between ESAD tumor stromal cells and cancer cells via a SPARC-TGF-β1 paracrine network.

The multifaceted role of Matricellular Proteins in health and cancer, as biomarkers and therapeutic targets

The extracellular matrix (ECM) is composed of a mesh of proteins, proteoglycans, growth factors, and other secretory components. It constitutes the tumor microenvironment along with the endothelial cells, cancer-associated fibroblasts, adipocytes, and immune cells. The proteins of ECM can be functionally classified as adhesive proteins and matricellular proteins (MCP). In the tumor milieu, the ECM plays a major role in tumorigenesis and therapeutic resistance. The current review encompasses thrombospondins, osteonectin, osteopontin, tenascin C, periostin, the CCN family, laminin, biglycan, decorin, mimecan, and galectins. The matrix metalloproteinases (MMPs) are also discussed as they are an integral part of the ECM with versatile functions in the tumor stroma. In this review, the role of these proteins in tumor initiation, growth, invasion and metastasis have been highlighted, with emphasis on their contribution to tumor therapeutic resistance. Further, their potential as biomarkers and therapeutic targets based on existing evidence are discussed. Owing to the recent advancements in protein targeting, the possibility of agents to modulate MCPs in cancer as therapeutic options are discussed.

Clinical Significance of Circulating Tumor Cell Induced Epithelial-Mesenchymal Transition in Patients with Metastatic Colorectal Cancer by Single-Cell RNA-Sequencing

BACKGROUND

Circulating tumor cells (CTCs) are a prognostic marker in patients with metastatic colorectal cancer (mCRC). However, little is known about the characterization of CTCs in mCRC at the single-cell level using RNA sequencing. The purpose of this study was to validate the capability to detect and isolate single CTCs for single-cell RNA sequencing (scRNA-seq) and to identify clinical significance at a single CTC level.

METHODS

Single CTCs from 27 mCRC patients were collected by CTC-FIND, which is comprised of filter separation and immunomagnetic depletion to collect ultra-pure CTC samples. To address tumor heterogeneity, CTCs were collected without relying on any traditional CTC markers, such as epithelial and mesenchymal cell antigens, and were undertaken by scRNA-seq using SMART-Seq v4.

RESULTS

We identified 59 single CTCs which were classified into four groups by epithelial, epithelial-mesenchymal transition (EMT) and stem cell-related gene expression. Patients receiving second or later-line treatment who had EMT gene expressing CTCs had a significantly shorter PFS and OS.

CONCLUSIONS

Exploiting CTC-FIND with SMART-Seq v4 showed that scRNA-seq of CTCs may shed new insight into tumor heterogeneity of mCRC and that the presence of CTCs expressing EMT-related genes at the single-cell level could have prognostic value in mCRC patients.

Biomarkers in the diagnosis of pancreatic cancer: Are we closer to finding the golden ticket?

Pancreatic cancer (PC) is a leading cause of cancer related mortality on a global scale. The disease itself is associated with a dismal prognosis, partly due to its silent nature resulting in patients presenting with advanced disease at the time of diagnosis. To combat this, there has been an explosion in the last decade of potential candidate biomarkers in the research setting in the hope that a diagnostic biomarker may provide a glimmer of hope in what is otherwise quite a substantial clinical dilemma. Currently, serum carbohydrate antigen 19-9 is utilized in the diagnostic work-up of patients diagnosed with PC however this biomarker lacks the sensitivity and specificity associated with a gold-standard marker. In the search for a biomarker that is both sensitive and specific for the diagnosis of PC, there has been a paradigm shift towards a focus on liquid biopsy and the use of diagnostic panels which has subsequently proved to have efficacy in the diagnosis of PC. Currently, promising developments in the field of early detection on PC using diagnostic biomarkers include the detection of microRNA (miRNA) in serum and circulating tumour cells. Both these modalities, although in their infancy and yet to be widely accepted into routine clinical practice, possess merit in the early detection of PC. We reviewed over 300 biomarkers with the aim to provide an in-depth summary of the current state-of-play regarding diagnostic biomarkers in PC (serum, urinary, salivary, faecal, pancreatic juice and biliary fluid).

Targeting the Stroma in the Management of Pancreatic Cancer

Pancreatic cancer (PC) presents extremely aggressive tumours and is associated with poor survival. This is attributed to the unique features of the tumour microenvironment (TME), which is known to create a dense stromal formation and poorly immunogenic condition. In particular, the TME of PC, including the stromal cells and extracellular matrix, plays an essential role in the progression and chemoresistance of PC. Consequently, several promising agents that target key components of the stroma have already been developed and are currently in multiple stages of clinical trials. Therefore, the authors review the latest available evidence on novel stroma-targeting approaches, highlighting the potential impact of the stroma as a key component of the TME in PC.

Pan-Cancer Analyses Reveal Prognostic Value of Osteomimicry Across 20 Solid Cancer Types

Background

Osteomimicry of cancer cells had been widely reported in prostate cancer and breast cancer. However, the prognostic value of osteomimicry in various cancer types remained unclear. We hypothesized that osteomimicry would result in remodeling of the tumor microenvironment and was eligible to predict patient prognosis.

Methods

A comprehensive transcriptomic analysis of the osteomimicry, which was characterized by mRNA expression of SPARC, SPP1, and BGLAP, across 20 solid tumors (7564 patients) using RNA-seq data from The Cancer Genome Atlas (TCGA) was conducted. Samples of each cancer type were classified into subgroups (high vs. low) based on median value of osteomimetic markers, the associations of these markers with clinical outcomes, immune cell infiltration and immune checkpoints expression were explored.

Results

Each osteomimetic marker harbored prognostic value in the pan-cancer analyses [SPARC: hazard ratio (HR) = 1.10, p = 0.028; SPP1: HR = 1.25, p < 0.001; BGLAP: HR = 1.13, p = 0.005]. Patients with high expression of all the three genes also had significantly unfavorable survival (HR = 1.61, p < 0.0001) compared with those of low expression. Correlation analyses demonstrated that osteomimicry was closely related to tumor purity, dendritic cells (DC) infiltration and expression of immune checkpoints.

Conclusion

Osteomimicry had prognostic value in various cancer types and the underlying mechanism might correlate to the trapping and dysfunction of DCs in the tumor microenvironment, revealing the potential of osteomimicry as a target of immunotherapy.

Macrophage-derived SPARC Attenuates M2-mediated Pro-tumour Phenotypes

Since the theory of seed and soil was put forward, people have increasingly recognized that the tumour microenvironment is an important regulator of tumour progression and therapeutic response. Among them, M2-type macrophages (M2, as the major macrophage subtype in the tumour foci) have important promoting effects on various biological behaviours. Secreted protein acidic and rich in cysteine (SPARC) is an important anti-tumour component in the microenvironment of gastric cancer. This study shows that macrophages are an important source of the SPARC and that SPARC overexpression in M2 can reduce M2-mediated promoting proliferation, migration and anti-apoptotic effects in gastric cancer. Additionally, the AKT/mTOR signalling pathways may participate in the malignant process.

YAP1-mediated pancreatic stellate cell activation inhibits pancreatic cancer cell proliferation

Pancreatic stellate cells (PSCs) are activated in pancreatic ductal adenocarcinoma (PDAC) and are responsible for dense desmoplastic stroma. Yes-associated protein 1 (YAP1) can induce cancer-associated fibroblast activation in liver and breast tumors, but its effect on PSCs is unknown. In the present study, we determined that YAP1 was highly expressed in the nuclei of PDAC-derived activated PSCs. RNAi-mediated or pharmacological inhibition of YAP1 led to PSC deactivation. In addition, YAP1 stimulated the expression of secreted protein acidic and cysteine rich (SPARC) in PSCs, which was inhibited by RUNX1. SPARC secreted from PSCs inhibited pancreatic cancer cell (PCC) proliferation. High expression of nuclear YAP1 in tumor stroma was significantly correlated with SPARC expression and fibrosis degree in human PDAC tissues. Our study revealed a critical role for YAP1 in the regulation of PSC activation and paracrine signaling. Our findings provide insights into a novel rationale for targeting YAP1 to reprogram the PDAC microenvironment.

Low expression of SPARC in gastric cancer-associated fibroblasts leads to stemness transformation and 5-fluorouracil resistance in gastric cancer

Background

The aim of the present study was to clarify the correlations between SPARC expression in gastric cancer-associated fibroblasts (GCAFs) and the prognosis of patients with gastric cancer and to elucidate the role of GCAF-derived SPARC in stemness transformation and 5-fluorouracil resistance in gastric cancer.

Methods

One hundred ninety-two patients were enrolled in the present study. SPARC expression levels were evaluated by immunohistochemical staining. Primary GCAFs were obtained and cultured from cancer patients for in vitro study, and a lentivirus infection method was employed to knock down SPARC expression in GCAFs. The stemness phenotype and 5-fluorouracil (5-FU) response of gastric cancer cells were assessed via a 3D co-culture model. The apoptotic status and stemness alterations were monitored by flow cytometry and western blotting. Additionally, label-free quantification proteomics was used to identify the differentially expressed proteins and potential pathways in gastric cancer cells treated with GCAF-derived SPARC.

Results

Low expression of GCAF-derived SPARC was associated with decreased differentiation and reduced 5-year overall survival and was an independent predictive factor for prognosis in gastric cancer. The 3D tumour growth and 5-FU resistance abilities of gastric cancer cells were elevated after treatment with GCAFs with SPARC knockdown relative to these abilities in negative control cells. Additionally, suppressing SPARC expression in GCAFs facilitated the phenotypic alteration of gastric cancer cells towards CD44⁺/CD24⁻ cancer stem cell (CSC)-like cells. Quantification proteomics analysis revealed that the differentially expressed proteins in gastric cancer cells were mainly involved in the AKT/mTOR and MEK/ERK signalling pathways.

Conclusions

SPARC expression in GCAFs is a useful prognostic factor in patients with gastric cancer. Low expression of GCAF-derived SPARC can lead to CSC transformation and 5-FU resistance. Additionally, the AKT/mTOR and MEK/ERK signalling pathways may participate in the malignant process.

Electronic supplementary material

The online version of this article (10.1186/s12935-019-0844-8) contains supplementary material, which is available to authorized users.

Ping-Pong-Tumor and Host in Pancreatic Cancer Progression

Metastasis is the main cause of high pancreatic cancer (PaCa) mortality and trials dampening PaCa mortality rates are not satisfying. Tumor progression is driven by the crosstalk between tumor cells, predominantly cancer-initiating cells (CIC), and surrounding cells and tissues as well as distant organs, where tumor-derived extracellular vesicles (TEX) are of major importance. A strong stroma reaction, recruitment of immunosuppressive leukocytes, perineural invasion, and early spread toward the peritoneal cavity, liver, and lung are shared with several epithelial cell-derived cancer, but are most prominent in PaCa. Here, we report on the state of knowledge on the PaCIC markers Tspan8, alpha6beta4, CD44v6, CXCR4, LRP5/6, LRG5, claudin7, EpCAM, and CD133, which all, but at different steps, are engaged in the metastatic cascade, frequently via PaCIC-TEX. This includes the contribution of PaCIC markers to TEX biogenesis, targeting, and uptake. We then discuss PaCa-selective features, where feedback loops between stromal elements and tumor cells, including distorted transcription, signal transduction, and metabolic shifts, establish vicious circles. For the latter particularly pancreatic stellate cells (PSC) are responsible, furnishing PaCa to cope with poor angiogenesis-promoted hypoxia by metabolic shifts and direct nutrient transfer via vesicles. Furthermore, nerves including Schwann cells deliver a large range of tumor cell attracting factors and Schwann cells additionally support PaCa cell survival by signaling receptor binding. PSC, tumor-associated macrophages, and components of the dysplastic stroma contribute to perineural invasion with signaling pathway activation including the cholinergic system. Last, PaCa aggressiveness is strongly assisted by the immune system. Although rich in immune cells, only immunosuppressive cells and factors are recovered in proximity to tumor cells and hamper effector immune cells entering the tumor stroma. Besides a paucity of immunostimulatory factors and receptors, immunosuppressive cytokines, myeloid-derived suppressor cells, regulatory T-cells, and M2 macrophages as well as PSC actively inhibit effector cell activation. This accounts for NK cells of the non-adaptive and cytotoxic T-cells of the adaptive immune system. We anticipate further deciphering the molecular background of these recently unraveled intermingled phenomena may turn most lethal PaCa into a curatively treatable disease.

The impact of SPARC expression on the survival of pancreatic ductal adenocarcinoma patients after curative resection

Background: The predictive roles of secreted protein acidic and rich in cysteine (SPARC) in pancreatic ductal adenocarcinoma (PDAC) patients after curative resection have not been clarified. We investigated the correlations between the SPARC expression and the postoperative prognosis. Methods: We retrospectively analyzed the clinical data from consecutive patients who underwent curative resection for pancreatic cancer in our institution from 2005 to 2014. Stromal SPARC expression was analyzed by immunohistochemistry on tumor tissue microarrays (TMAs) from the patients. Results: A total of 179 patients were enrolled to this study. The median follow-up period of the present study was 62.1 months. Seventy patients had positive SPARC expression (39.1%). There were no significant differences between the positive SPARC-positive group and the SPARC-negative group. In the survival analysis, there was a significant difference between the SPARC-positive and SPARC-negative groups in the 5-year overall survival (OS) rates after surgery, which were 8.1% and 19.8%, respectively (p=0.0316). A univariate analysis showed that the SPARC expression, size of tumor, lymph node metastasis, and residual tumor were possible prognostic factors. A multivariate analysis showed that the SPARC expression (hazard ratio [HR]: 1.44, 95% confidence interval [CI]: 1.017-2.051), lymph node metastasis (HR: 2.019, 95% CI: 1.318-3.091), and residual tumor (HR: 1.648, 95% CI: 1.132-2.401) were independent prognostic factors. Conclusions: The stromal SPARC expression in resectable pancreatic cancer patients might be useful as a prognostic marker.

Biomarkers and pathways of chemoresistance and chemosensitivity for personalized treatment of pancreatic adenocarcinoma

Pancreatic carcinoma is usually diagnosed late when treatment options are limited and is considered a chemo-resistant malignancy. However, early stage, good performance status and specific patient subgroup are thought to have a more favorable prognosis. Search for novel molecular biomarkers, which could predict treatment resistance, represents a major opportunity, but also a challenge in further research. This review summarizes most aspects of individualized therapy of pancreatic cancer including promising biomarkers, BRCA-deficient pancreatic cancer and its etiology. It may be estimated that nearly a third of metastatic pancreatic ductal adenocarcinoma patients could benefit from treatment other than gold standard chemotherapy. Thus, other aspects of an individualized approach concerning the main factors for the choice of the best therapy for individual pancreatic cancer patient (surgery and chemotherapy), as well as the future directions (target therapy and immunotherapy), are also addressed.

Shattering the castle walls: Anti-stromal therapy for pancreatic cancer

Despite the availability of potent chemotherapy regimens, such as 5-fluorouracil, folinic acid, irinotecan, and oxaliplatin (FOLFIRINOX) and nab-paclitaxel plus gemcitabine, treatment outcomes in metastatic pancreatic cancer (PC) remain unsatisfactory. The presence of an abundant fibrous stroma in PC is considered a crucial factor for its unfavorable condition. Apparently, stroma acts as a physical barrier to restrict intratumoral cytotoxic drug penetration and creates a hypoxic environment that reduces the efficacy of radiotherapy. In addition, stroma plays a vital supportive role in the development and progression of PC, which has prompted researchers to assess the potential benefits of agents targeting several cellular (e.g., stellate cells) and acellular (e.g., hyaluronan) elements of the stroma. This study aims to briefly review the primary structural properties of PC stroma and its interaction with cancer cells and summarize the current status of anti-stromal therapies in the management of metastatic PC.

Correlation between secreted protein acidic and rich in cysteine protein expression and the prognosis of postoperative patients exhibiting esophageal squamous cell carcinoma

The aim of the present study was to investigate the association between the expression level of secreted protein acidic and rich in cysteine (SPARC) and the prognosis of postoperative patients with esophageal squamous cell carcinoma (ESCC). The expression level of SPARC was detected in the 89 ESCC tissue cases and 100 healthy esophageal mucosa cases, which served as the controls. Immunohistochemistry and reverse transcription‑polymerase chain reaction (RT‑PCR) were employed to evaluate the SPARC expression in cases with ESCC. RT‑PCR demonstrated that the positive rates of SPARC mRNA expression in ESCC were 71.91% (64/89). The positive rates of normal esophageal mucosa mRNA expression were 15.00% (15/100), which were significantly lower than that in the ESCC tissue samples. The difference was statistically significant (P<0.001). Immunohistochemical staining indicated that the positive expression rate of SPARC protein in the ESCC tissue samples was significantly higher than that in the esophageal mucosa tissue samples (65.17 vs. 8.00%; P<0.001). The expression of SPARC protein was negatively correlated with lymph node metastasis (P<0.05), which was not associated with the pathologic gross morphology, tumor differentiation degree or other clinical features. The survival of patients with ESCC was not associated with the expression level of SPARC protein (P>0.05), but was associated with the tumor location (P<0.05), differentiation (P<0.001) and staging (P<0.05). Thus, SPARC mRNA and protein were highly expressed in ESCC, and negatively correlated with lymph node metastasis, which was not associated with postoperative survival of ESCC patients. Thus, detection of SPARC mRNA and protein expression levels may facilitate early diagnosis and prognosis assessment of ESCC.

Biochemical and genetic predictors of overall survival in patients with metastatic pancreatic cancer treated with capecitabine and nab-paclitaxel

Pancreatic cancer is a dismal disease with a mortality rate almost similar to its incidence rate. To date, there are neither validated predictive nor prognostic biomarkers for this lethal disease. Thus, the aim of the present study was to retrospectively investigate the capability of biochemical parameters and molecular profiles to predict survival of patients with metastatic pancreatic ductal adenocarcinoma (mPDAC) who participated in a phase II clinical trial to test the safety and efficacy of the combination treatment of capecitabine plus nab-paclitaxel. Herein, we investigated the association of 18 biochemical parameters obtained from routine diagnosis and the clinical outcome of the 30 patients enrolled in the clinical trial. Furthermore, we analysed formalin-fixed paraffin-embedded (FFPE) tumour tissue to identify molecular biomarkers via RNA seq and the Illumina TruSeq Amplicon Cancer panel which covers 48 hotspot genes. Our analysis identified SERPINB7 as a novel transcript and a DNA mutation signature that might predict a poor outcome of disease. Moreover, we identified the bilirubin basal level as an independent predictive factor for overall survival in our study cohort.

Smoc2 potentiates proliferation of hepatocellular carcinoma cells via promotion of cell cycle progression

AIM

To determine the influence of Smoc2 on hepatocellular carcinoma (HCC) cell proliferation and to find a possible new therapeutic target for preventing HCC progression.

METHODS

We detected expression of Smoc2 in HCC tissues and corresponding non-tumor liver (CNL) tissues using PCR, western blot, and immunohistochemistry methods. Subsequently, we down-regulated and up-regulated Smoc2 expression using siRNA and lentivirus transfection assay, respectively. Then, we identified the effect of Smoc2 on cell proliferation and cell cycle using CCK-8 and flow cytometry, respectively. The common cell growth signaling influenced by Smoc2 was detected by western blot assay.

RESULTS

The expression of Smoc2 was significantly higher in HCC tissues compared with CNL tissues. Overexpression of Smoc2 promoted HCC cell proliferation and cell cycle progression. Down-regulation of Smoc2 led to inhibition of cell proliferation and cell cycle progression. Smoc2 had positive effect on ERK and AKT signaling.

CONCLUSION

Smoc2 promotes the proliferation of HCC cells through accelerating cell cycle progression and might act as an anti-cancer therapeutic target in the future.