Aberrant methylation of SPARC in human lung cancers

Cell-type-specific alternative polyadenylation promotes oncogenic gene expression in non-small cell lung cancer progression

Disrupted alternative polyadenylation (APA) is frequently involved in tumorigenesis and cancer progression by regulating the gene expression of oncogenes and tumor suppressors. However, limited knowledge of tumor-type- and cell-type-specific APA events may lead to novel APA events and their functions being overlooked. Here, we compared APA events across different cell types in non-small cell lung cancer (NSCLC) and normal tissues and identified functionally related APA events in NSCLC. We found several cell-specific 3'-UTR alterations that regulate gene expression changes showed prognostic value in NSCLC. We further investigated the function of APA-mediated 3'-UTR shortening through loss of microRNA (miRNA)-binding sites, and we identified and experimentally validated several oncogene-miRNA-tumor suppressor axes. According to our analyses, we found SPARC as an APA-regulated oncogene in cancer-associated fibroblasts in NSCLC. Knockdown of SPARC attenuates lung cancer cell invasion and metastasis. Moreover, we found high SPARC expression associated with resistance to several drugs except cisplatin. NSCLC patients with high SPARC expression could benefit more compared to low-SPARC-expression patients with cisplatin treatment. Overall, our comprehensive analysis of cell-specific APA events shed light on the regulatory mechanism of cell-specific oncogenes and provided opportunities for combination of APA-regulated therapeutic target and cell-specific therapy development.

Modeling extracellular matrix through histo-molecular gradient in NSCLC for clinical decisions

Lung cancer still represents a global health problem, being the main type of tumor responsible for cancer deaths. In this context, the tumor microenvironment, and the extracellular matrix (ECM) pose as extremely relevant. Thus, this study aimed to explore the prognostic value of epithelial-to-mesenchymal transition (EMT), Wnt signaling, and ECM proteins expression in patients with non-small-cell lung carcinoma (NSCLC) with clinical stages I-IIIA. For that, we used 120 tissue sections from patients and evaluated the immunohistochemical, immunofluorescence, and transmission electron microscopy (TEM) to each of these markers. We also used in silico analysis to validate our data. We found a strong expression of E-cadherin and β-catenin, which reflects the differential ECM invasion process. Therefore, we also noticed a strong expression of chondroitin sulfate (CS) and collagens III and V. This suggests that, after EMT, the basal membrane (BM) enhanced the motility of invasive cells. EMT proteins were directly associated with WNT5A, and collagens III and V, which suggests that the WNT pathway drives them. On the other hand, heparan sulfate (HS) was associated with WNT3A and SPARC, while WNT1 was associated with CS. Interestingly, the association between WNT1 and Col IV suggested negative feedback of WNT1 along the BM. In our cohort, WNT3A, WNT5A, heparan sulfate and SPARC played an important role in the Cox regression model, influencing the overall survival (OS) of patients, be it directly or indirectly, with the SPARC expression stratifying the OS into two groups: 97 months for high expression; and 65 for low expression. In conclusion, the present study identified a set of proteins that may play a significant role in predicting the prognosis of NSCLC patients with clinical stages I-IIIA.

Molecular approaches to equine sarcoids

Sarcoids are the most commonly diagnosed skin tumours in equines. Bovine papillomaviruses (BPVs) are the primary causative agent of sarcoids. There has been intensive research to discover the molecular mechanisms that may contribute to the aetiopathogenesis of this disease and tumour suppressors and proto-oncogenes known to play a role in human neoplastic conditions have been investigated in equine sarcoids. Current approaches include the identification of gene expression profiles, characterising sarcoid and normal skin tissues, and an assessment of epigenetic alterations such as microRNA differential expression and DNA methylation status. This review focuses on selected groups of genes that contribute to the molecular mechanisms of sarcoid formation. These genes have the potential to complement current clinical examinations of equine sarcoid disease in diagnosis, prognosis, therapeutic response and screening.

SPARC-p53: The double agents of cancer

Cancer is a complex disease with high incidence and mortality rates. The important role played by the tumor microenvironment in regulating oncogenesis, tumor growth, and metastasis is by now well accepted in the scientific community. SPARC is known to participate in tumor-stromal interactions and impact cancer growth in ambiguous ways, which either enhance or suppress cancer aggressiveness, in a context-dependent manner. p53 transcription factor, a well-established tumor suppressor, has been reported to promote tumor growth in certain situations, such as hypoxia, thus displaying a duality in its action. Although both proteins are being tested in clinical trials, the synergistic relation between them is yet to be explored in clinical practice. In this review, we address the controversial roles of SPARC and p53 as double agents in cancer, briefly summarizing the interaction found between these two molecules and its importance in cancer.

Decorin gene upregulation mediated by an adeno-associated virus vector increases intratumoral uptake of nab-paclitaxel in neuroblastoma via inhibition of stabilin-1

The availability of effective medication for the treatment of refractory or recurrent neuroblastoma remains limited. This study sought to investigate the effects of increased decorin (DCN) expression on the intratumoral uptake of nab-paclitaxel as a potential novel approach to NB. Correlation between the clinical characteristics of neuroblastoma and the expression of DCN, secreted protein acidic and rich in cysteine (SPARC) and stabilin-1 was evaluated. The anticancer effect of recombinant adeno-associated virus-DCN (rAAV-DCN) was assessed in vivo and in vitro. And the effect of rAAV-DCN on the intratumoral uptake of paclitaxel was also studied in neuroblastoma-grafted nude mice. Overall, 12.5%, 17.7%, and 71.9% of the tumors stained positive for DCN, SPARC and stabilin-1 respectively and correlated to age, stage and N-MYC status in 96 children and adolescents with neuroblastoma. Transfected neuroblastoma cells stably expressed DCN, with in vivo and in vitro studies demonstrating rAAV-DCN sensitized the anticancer effect of nab-paclitaxel. Systemic rAAV-DCN in neuroblastoma-grafted nude mice inhibited stabilin-1, up-regulated SPARC, and increased the intratumoral uptake of paclitaxel. Macrophage depletion or anti-stabilin-1 monoclonal antibody increased the intratumoral uptake of nab-paclitaxel and its anticancer effects to a degree comparable to that achieved by systemic rAAV-DCN. The systemic administration of rAAV-DCN up-regulates DCN in neuroblastoma and accelerates the intratumoral uptake of nab-paclitaxel by inhibiting stabilin-1 mediated SPARC degradation.

A phase I trial of azacitidine and nanoparticle albumin bound paclitaxel in patients with advanced or metastatic solid tumors

Background

Secreted protein acidic and rich in cysteine (SPARC), an albumin-binding protein, is downregulated by hypermethylation in many cancers. Hypomethylating agents such as azacitidine can upregulate SPARC in tumors, which may enhance the accumulation of albumin-bound drugs at tumor site. The objectives of this phase I trial was to determine the safety and maximum tolerated dose and to assess any clinical activity of the combination of azacytidine and weekly nanoparticle-albumin-bound (nab®) paclitaxel.

Methods

Patients received escalating azacytidine doses daily for 5 days, followed by nab-paclitaxel at the standard 100mg/m2 weekly dose for 3 weeks in 4-week cycles. Dose-limiting toxicities (DLTs) were monitored during the first cycle. Serum was obtained at baseline, during and after treatment for correlative study.

Results

All sixteen total patients enrolled were evaluable for toxicity, while 13 patients were evaluable for response. Two of five patients treated with 100mg/m2 of azacytidine had DLT of prolonged grade 4 neutropenia. Therefore, the MTD of azacitidine in this regimen is 75 mg/m². Three additional patients were treated with no grade 4 toxicity in cycle 1. Clinical activity included 1 complete response (CR) in refractory DLBCL, 2 CR in ovarian cancer, 4 partial responses (PR) in ovarian and endometrial cancer, 4 stable diseases (SD) in lung, sarcoma and pancreatic cancer, 1 unconfirmed PR in breast cancer, and 1 progression of disease in CLL/SLL.

Conclusions

Priming with azacitidine 75 mg/m² daily for 5 days, followed by weekly nab-paclitaxel 100 mg/m² weekly was well tolerated and results in dramatic responses pre-treated cancer patients.

Complete response to azacitidine priming and nab-paclitaxel in non-Hodgkin lymphoma resistant to biochemotherapy

The standard of care for first-line therapy in diffuse large B-cell lymphoma (DLBCL) is the rituximab, cyclophosphamide, doxorubicin, vincristine and prednisone (R-CHOP) regimen. For patients who fail to respond, have an incomplete response or relapse, numerous effective options exists besides salvage cisplatin-based regimen and autologous stem cell therapy. Even with this approach, the outcome remains very poor for this group of patients. The present case illustrates a 55-year-old woman diagnosed with DLBCL, who experienced an early incomplete response, later progression during treatment with the R-CHOP regimen. The patient received salvage therapy with rituximab, cisplatin and gemcitabine, again with an incomplete response. The patient declined consideration for stem cell therapy. Her disease progressed and she enrolled in the present phase I trial using azacitadine priming and nanoalbumin-bound (nab)-paclitaxel. After three cycles, follow-up positron emission tomography/computed tomography revealed a complete response for the first time since her initial diagnosis and the patient has remained disease-free for >6 years. Azacitadine and nab-paclitaxel combination appeared to be an effective regimen for the treatment of this patient with refractory DLBCL.

SPARC Promotes Cell Invasion In Vivo by Decreasing Type IV Collagen Levels in the Basement Membrane

Overexpression of SPARC, a collagen-binding glycoprotein, is strongly associated with tumor invasion through extracellular matrix in many aggressive cancers. SPARC regulates numerous cellular processes including integrin-mediated cell adhesion, cell signaling pathways, and extracellular matrix assembly; however, the mechanism by which SPARC promotes cell invasion in vivo remains unclear. A main obstacle in understanding SPARC function has been the difficulty of visualizing and experimentally examining the dynamic interactions between invasive cells, extracellular matrix and SPARC in native tissue environments. Using the model of anchor cell invasion through the basement membrane (BM) extracellular matrix in Caenorhabditis elegans, we find that SPARC overexpression is highly pro-invasive and rescues BM transmigration in mutants with defects in diverse aspects of invasion, including cell polarity, invadopodia formation, and matrix metalloproteinase expression. By examining BM assembly, we find that overexpression of SPARC specifically decreases levels of BM type IV collagen, a crucial structural BM component. Reduction of type IV collagen mimicked SPARC overexpression and was sufficient to promote invasion. Tissue-specific overexpression and photobleaching experiments revealed that SPARC acts extracellularly to inhibit collagen incorporation into BM. By reducing endogenous SPARC, we also found that SPARC functions normally to traffic collagen from its site of synthesis to tissues that do not express collagen. We propose that a surplus of SPARC disrupts extracellular collagen trafficking and reduces BM collagen incorporation, thus weakening the BM barrier and dramatically enhancing its ability to be breached by invasive cells.

Epigenetics of lung cancer

Lung cancer is the leading cause of cancer-related mortality in the United States. Epigenetic alterations, including DNA methylation, histone modifications, and noncoding RNA expression, have been reported widely in the literature to play a major role in the genesis of lung cancer. The goal of this review is to summarize the common epigenetic changes associated with lung cancer to give some clarity to its etiology, and to provide an overview of the potential translational applications of these changes, including applications for early detection, diagnosis, prognostication, and therapeutics.

Role of SPARC in bone remodeling and cancer-related bone metastasis

There is a growing socioeconomic recognition that clinical bone diseases such as bone infections, bone tumors and osteoporotic bone loss mainly associated with ageing, are major issues in today's society. SPARC (secreted protein, acidic and rich in cysteine), a matricellular glycoprotein, may be a promising therapeutic target for preventing or treating bone-related diseases. In fact, SPARC is associated with tissue remodeling, repair, development, cell turnover, bone mineralization and may also participate in growth and progression of tumors, namely cancer-related bone metastasis. Yet, the function of SPARC in such biological processes is poorly understood and controversial. The main objective of this work is to review the current knowledge related to the activity of SPARC in bone remodeling, tumorigenesis, and bone metastasis. Progress in understanding SPARC biology may provide novel strategies for bone regeneration and the development of anti-angiogenic, anti-proliferative, or counter-adhesive treatments specifically against bone metastasis.

Revisiting the matricellular concept

The concept of a matricellular protein was first proposed by Paul Bornstein in the mid-1990s to account for the non-lethal phenotypes of mice with inactivated genes encoding thrombospondin-1, tenascin-C, or SPARC. It was also recognized that these extracellular matrix proteins were primarily counter or de-adhesive. This review reappraises the matricellular concept after nearly two decades of continuous investigation. The expanded matricellular family as well as the diverse and often unexpected functions, cellular location, and interacting partners/receptors of matricellular proteins are considered. Development of therapeutic strategies that target matricellular proteins are discussed in the context of pathology and regenerative medicine.

Molecular mechanisms underlying the divergent roles of SPARC in human carcinogenesis

Communication between the cell and its surrounding environment, consisting of proteinaceous (non-living material) and extracellular matrix (ECM), is important for biophysiological and chemical signaling. This signaling results in a range of cellular activities, including cell division, adhesion, differentiation, invasion, migration and angiogenesis. The ECM non-structural secretory glycoprotein called secreted protein, acidic and rich in cysteine (SPARC), plays a significant role in altering cancer cell activity and the tumor's microenvironment (TME). However, the role of SPARC in cancer research has been the subject of controversy. This review mainly focuses on recent advances in understanding the contradictory nature of SPARC in relation to ECM assembly, cancer cell proliferation, adhesion, migration, apoptosis and tumor growth.

DNA methylation: its role in lung carcinogenesis and therapeutic implications

A new era in the treatment of malignant diseases has been observed through the use of biologic agents targeting growth factor receptors, signaling pathways, gene mutations and others. The results have been impressive in some diseases and modest in others. The discovery of new targets has expanded our knowledge of different mechanisms in tumorigenesis. One of these mechanisms has been DNA methylation, which is an important gene transcription regulator. Although the role of methylation in lung carcinogenesis is not well understood, there is an enormous quantity of evolving data suggesting its critical role in lung cancer. In this review, the authors will discuss methylation in lung carcinogenesis and its possible clinical implications.

First line treatment of advanced non-small-cell lung cancer - specific focus on albumin bound paclitaxel

Lung cancer is the leading cause of cancer mortality worldwide in both men and women. Non-small-cell lung cancer (NSCLC) is the most common type of lung cancer, accounting for more than 80% of cases. Paclitaxel has a broad spectrum of activity against various malignancies, including NSCLC. Paclitaxel is poorly soluble in water and thus, until recently, its commercially available preparations contained a non-ionic solvent Cremophor EL®. Cremophor EL® improves the solubility of paclitaxel and allows its intravenous administration. However, certain side-effects associated with paclitaxel, such as hypersensitivity reactions, myelosuppression, and peripheral neuropathy, are known to be worsened by Cremophor®. Nanoparticle albumin-bound paclitaxel ([nab-paclitaxel] ABRAXANE® ABI-007) is a new generation formulation of paclitaxel that obviates the need for Cremophor®, resulting in a safer and faster infusion without requiring the use of premedications to avoid hypersensitivity. Albumin-binding receptor-mediated delivery and lack of sequestering Cremophor® micelles allow higher intratumoral concentration of pharmacologically active paclitaxel. Multiple clinical trials have demonstrated a superior tolerability profile of nab-paclitaxel in comparison to solvent-bound paclitaxel (sb-paclitaxel). A recent Phase III trial compared the effects of weekly nab-paclitaxel in combination with carboplatin versus sb-paclitaxel in combination with carboplatin given every 3 weeks for first line treatment of NSCLC. This trial highlights the weekly nab-paclitaxel combination as an alternate treatment option for NSCLC, with higher response rate in squamous cell NSCLC and longer survival in elderly patients. This review will focus on the properties of nab-paclitaxel and its use in the first line treatment of NSCLC.

[Correlation of KLF4 and SPARC expression with the clinical characteristics of non-small cell lung cancer]

背景与目的

已有研究证实KLF4基因（Krüppel-like factor 4）和富含半胱氨酸的酸性分泌蛋白（secreted protein acidic and rich in cysteine, SPARC）与肿瘤的发生发展密切相关。本研究旨在检测KLF4和SPARC蛋白在非小细胞肺癌（non-small cell lung cancer, NSCLC）中的表达，并结合临床病理特征来探讨KLF4和SPARC的临床意义及相关性。

方法

应用免疫组织化学方法检测89例NSCLC组织及正常肺组织中KLF4和SPARC的表达。

结果

KLF4在癌旁正常肺组织阳性表达率为88.8%，NSCLC组织为42.7%（P < 0.05）；有、无淋巴结转移者的KLF4阳性表达率分别为31.3%和56.1%（P < 0.05）；KLF4的表达与肿瘤临床分期有关（P < 0.05），随着临床分期等级的增加，KLF4表达呈现递减趋势。SPARC在NSCLC组织的阳性表达率为70.8%，癌旁正常肺组织为7.9%（P < 0.05）；低、高分化癌的SPARC阳性表达率无统计学差异（P > 0.05）；有、无淋巴结转移者的SPARC阳性表达率分别为81.3%和58.5%（P < 0.05）；其表达与肿瘤的临床分期相关（P < 0.05）。KLF4和SPARC的表达均与患者的性别、年龄和肿瘤大小无关（P > 0.05）。SPARC和KLF4在NSCLC中的表达呈负相关（r=-0.245, P < 0.05）。

结论

KLF4低表达及SPARC的过表达与NSCLC的发生及其生物学行为密切相关，可能作为NSCLC诊断及分期预后的指标。

Progress in understanding role of SPARC protein in gastric cancer

SPARC is a cysteine-rich secretory protein that is highly conservative and shares >70% amino acid sequence homology across all kinds of living organisms. The single-copy gene encoding the SPARC protein is located on human chromosome 5q31.3-q32, consists of 10 exons, and has a full length of 25 900 bp. SPARC protein is mainly expressed in tissue repair-related fibroblasts and endothelial cells, and high expression of SPARC protein has been noted in some aggressive malignant tumors. The incidence and mortality of gastric cancer are high in China, and the high mortality is closely related with tumor invasion and metastasis. SPARC protein is abnormally expressed in gastric carcinoma, and there is still controversy over the role of SPARC in gastric carcinoma. In this paper we review recent progress in understanding the role of SPARC protein in gastric cancer.

Engineering mouse models with myelodysplastic syndrome human candidate genes; how relevant are they?

Myelodysplastic syndromes represent particularly challenging hematologic malignancies that arise from a large spectrum of genetic events resulting in a disease characterized by a range of different presentations and outcomes. Despite efforts to classify and identify the key genetic events, little improvement has been made in therapies that will increase patient survival. Animal models represent powerful tools to model and study human diseases and are useful pre-clinical platforms. In addition to enforced expression of candidate oncogenes, gene inactivation has allowed the consequences of the genetic effects of human myelodysplastic syndrome to be studied in mice. This review aims to examine the animal models expressing myelodysplastic syndrome-associated genes that are currently available and to highlight the most appropriate model to phenocopy myelodysplastic syndrome disease and its risk of transformation to acute myelogenous leukemia.

Aberrant methylation of SPARC in human hepatocellular carcinoma and its clinical implication

AIM: To investigate the methylation status of secreted protein acidic and rich in cysteine (SPARC) in human hepatocellular carcinoma (HCC) and evaluate its clinical implication.

METHODS: The methylation status of SPARC was analyzed in one HCC cell line (SMMC-7721) and 60 pairs of HCC and corresponding nontumorous tissues by methylation-specific polymerase chain reaction and bisulfite sequencing. The expression of SPARC mRNA and protein were examined by reverse transcription polymerase chain reaction and immunohistochemistry, respectively. The correlations between the methylation status and the gene expression, the clinicopathological parameters, as well as the prognosis after surgery were analyzed.

RESULTS: In the SMMC-7721 cell line, the loss of SPARC expression was correlated with the aberrant methylation and could be reactivated by the demethylating agent 5-aza-2’-deoxycytidine. Methylation frequency of SPARC in HCC was significantly higher than that in the corresponding nontumorous tissues (45/60 vs 7/60, P < 0.001), and it was correlated with the pathological classification (P = 0.019). The downregulation of the SPARC mRNA expression in HCC was correlated with the SPARC methylation (P = 0.040). The patients with methylated SPARC had a poorer overall survival than those without methylated SPARC (28.0 mo vs 41.0 mo, P = 0.043).

CONCLUSION: Aberrant methylation is an important mechanism for SPARC inactivation in HCC and SPARC methylation may be a promising biomarker for the diagnosis and prognosis of HCC.

Shortening of 3’UTRs correlates with poor prognosis in breast and lung cancer. PLoS One. 2012;7:e31129. [PMID: 22347440 PMCID: PMC3275581 DOI: 10.1371/journal.pone.0031129]

A major part of the post-transcriptional regulation of gene expression is affected by trans-acting elements, such as microRNAs, binding the 3' untraslated region (UTR) of their target mRNAs. Proliferating cells partly escape this type of negative regulation by expressing shorter 3' UTRs, depleted of microRNA binding sites, compared to non-proliferating cells. Using large-scale gene expression datasets, we show that a similar phenomenon takes place in breast and lung cancer: tumors expressing shorter 3' UTRs tend to be more aggressive and to result in shorter patient survival. Moreover, we show that a gene expression signature based only on the expression ratio of alternative 3' UTRs is a strong predictor of survival in both tumors. Genes undergoing 3'UTR shortening in aggressive tumors of the two tissues significantly overlap, and several of them are known to be involved in tumor progression. However the pattern of 3' UTR shortening in aggressive tumors in vivo is clearly distinct from analogous patterns involved in proliferation and transformation.

Aberrant DNA methylation of tumor-related genes in oral rinse: a noninvasive method for detection of oral squamous cell carcinoma

BACKGROUND

The early detection of oral squamous cell carcinoma (OSCC) is important, and a screening test with high sensitivity and specificity is urgently needed. Therefore, in this study, the authors investigated the methylation status of tumor-related genes with the objective of establishing a noninvasive method for the detection of OSCC.

METHODS

Oral rinse samples were obtained from 34 patients with OSCC and from 24 healthy individuals (controls). The methylation status of 13 genes was determined by using methylation-specific polymerase chain reaction analysis and was quantified using a microchip electrophoresis system. Promoter methylation in each participant was screened by receiver operating characteristic analysis, and the utility of each gene's methylation status, alone and in combination with other genes, was evaluated as a tool for oral cancer detection.

RESULTS

Eight of the 13 genes had significantly higher levels of DNA methylation in samples from patients with OSCC than in controls. The genes E-cadherin (ECAD), transmembrane protein with epidermal growth factor-like and 2 follistatin-like domains 2 (TMEFF2), retinoic acid receptor beta (RARβ), and O-6 methylguanine DNA methyltransferase (MGMT) had high sensitivity (>75%) and specificity for the detection of oral cancer. OSCC was detected with 100% sensitivity and 87.5% specificity using a combination of ECAD, TMEFF2, RARβ, and MGMT and with 97.1% sensitivity and 91.7% specificity using a combination of ECAD, TMEFF2, and MGMT.

CONCLUSIONS

The aberrant methylation of a combination of marker genes present in oral rinse samples was used to detect OSCC with >90% sensitivity and specificity. The detection of methylated marker genes from oral rinse samples has great potential for the noninvasive detection of OSCC.

Methylation of the APAF-1 and DAPK-1 promoter region correlates with progression of renal cell carcinoma in North Indian population

Aberrant promoter hypermethylation of cancer associated genes occur frequently during carcinogenesis and may serve as a cancer biomarker. The aim of this study was to investigate the occurrence and relevance of promoter methylation of the tumor suppressor DAPK-1, APAF-1 () and SPARC in relation to different pathological stages and histological grades of tumor progression that might act as possible independent prognostic factor in the susceptibility towards renal cell carcinoma (RCC) in North Indian population. Three tumor suppressor gene promoters namely APAF-1, DAPK-1 and SPARC were assessed by methylation-specific PCR (MS-PCR) in 196 primarily resected renal cell tumors paired with the corresponding normal tissue samples. After genomic DNA isolation and sodium bisulfite modification, methylation levels were determined and correlated with standard clinicopathological parameters, pathological stage and Fuhrman nuclear grade of RCC. Significant differences in methylation frequency among the four subtypes of renal tumors were found for APAF-1 (p < 0.001), DAPK-1 (p < 0.001) and SPARC (p = 0.182), when compared with the corresponding normal tissue. Male subjects showed stronger association of methylation frequency of all the three genes with RCC than the female subjects. Additionally, higher frequency of APAF-1, DAPK-1 and SPARC promoter methylation were directly correlated with higher tumor stage (p (trend) < 0.001). Higher frequency of promoter methylation of APAF-1 and SPARC were also associated with higher nuclear grade (p < 0.001 and p = 0.036, respectively). This gene panel might contribute to a more optimal diagnostic coverage and information, improving preoperative assessment and therapeutic decision-making in patients harboring suspicious renal masses.

Genetic and epigenetic changes in lung carcinoma and their clinical implications

Lung cancer is the leading cause of cancer deaths worldwide. Recent advance in targeted therapy for lung cancer patients with epidermal growth factor receptor (EGFR) mutations has demonstrated a promising development toward personalized therapy for lung cancer patients. The development of lung cancer is a complex process, involving a series of genetic and epigenetic changes. Tobacco smoke is the predominant etiologic risk factor for lung cancer. However, some lung cancers, especially adenocarcinomas, arise in patients who have never smoked, suggesting the importance of host genetic/epigenetic susceptibility in the occurrence and development of lung cancer. Understanding of these genetic and epigenetic changes will further aid in the biomarker-driven personalized therapy for lung cancer patients. In this review, we summarize the genetic and epigenetic alterations observed in lung cancers, including chromosomal loss of heterozygosity, tumor-suppressor gene mutation, gene methylation, histone modification, and microRNA expression changes. Clinical and preclinical studies have implied specific genetic/epigenetic changes for clinical application in lung cancer patients. However, more efforts are required in validation of the identified molecular markers in lung cancer patients for early detections, assessment for treatment response, and survival predictions.

Aberrant methylation of secreted protein, acidic and rich in cysteine in human laryngeal and hypopharyngeal carcinoma

Secreted protein, acidic and rich in cysteine (SPARC) has been found to be involved in various stages of tumor progression such as migration, invasion, extracellular matrix deposition and angiogenesis. To obtain an insight into the role of SPARC in the progression of laryngeal and hypopharyngeal carcinoma, we investigated SPARC transcription levels and promoter methylation in carcinoma cell lines and primary tumors. Reverse transcription-PCR showed that SPARC was silenced in laryngeal and hypopharyngeal carcinoma cell lines, in which aberrant promoter methylation was detected. Hypermethylation of SPARC was detected in 56.1% (23/41) of laryngeal carcinoma and 70.0% (7/10) of hypopharyngeal carcinoma biopsies, but only in 11.1% (1/9) of normal epithelial specimens by a methylation-specific PCR assay. Bisulphite genomic sequencing indicated that CpG sites in the SPARC promoter were heavily methylated in cell lines and primary tumors. Moreover, pharmacological demethylation treatment rescued SPARC expression with 5-aza-2'-deoxycytidine (5-aza-dC) in the laryngeal carcinoma cell lines. SPARC promoter hypermethylation was significantly correlated with lymph node metastasis (p<0.01). Our findings suggest that hypermethylation of SPARC is a frequent and tumor-specific event in laryngeal and hypopharyngeal carcinomas and may serve as a biomolecular marker for diagnosis and prognosis.

Anti-cancer role of SPARC, an inhibitor of adipogenesis. Cancer Treat Rev. 2011;37:559-566. [PMID: 21237573 DOI: 10.1016/j.ctrv.2010.12.001]

SPARC (a secreted protein acidic and rich in cysteine) has a reputation for being potent anti-cancer and anti-obesity molecule. It is one of the first known matricellular protein that modulates interactions between cells and extracellular matrix (ECM) and is associated with the 'balance' of white adipose tissue (WAT) as well as lipogenesis and lipolysis during adipogenesis. Adipogenesis is an indication for the development of obesity and has been related to a wide variety of cancers including breast cancer, endometrial cancer, esophageal cancer, etc. Adipogenesis mainly involves ECM remodeling, changes in cell-ECM interactions, and cytoskeletal rearrangement. SPARC can also prevent hypertrophy of adipocytes and hyperplasia of adipocyte progenitors. In addition to SPARC's inhibitory role in adipogenesis, it has also been known to be involved in cell cycle, cell proliferation, cell invasion, adhesion, migration, angiogenesis and apoptosis. Molecular cancer biology and clinical biochemistry have significantly enhanced our understanding of the mechanisms that motivate the anti-cancer and anti-obesity action of SPARC. Recent studies elucidating the signaling pathways that are activated by SPARC can help develop the beneficial aspects of SPARC for cancer therapy and obesity prevention. This review focuses on the anti-cancer role of SPARC as it pertains to obesity.

SPARC gene expression is repressed in human urothelial cells (UROtsa) exposed to or malignantly transformed by cadmium or arsenite

SPARC belongs to a class of extracellular matrix-associated proteins that have counteradhesive properties. The ability of SPARC to modulate cell-cell and cell-matrix interactions provides a strong rationale for studies designed to determine its expression in cancer. The objective of this study was to determine if SPARC expression was altered in cadmium (Cd(2+)) and arsenite (As(3+)) induced bladder cancer and if these alterations were present in archival specimens of human bladder cancer. The expression of SPARC was determined in human parental UROtsa cells, their Cd(2+) and As(3+) transformed counterparts and derived tumors, and in archival specimens of human bladder cancer using a combination of real time reverse transcriptase polymerase chain reaction, Western blotting, immunofluorescence localization and immunohistochemical staining. It was demonstrated that SPARC expression was down-regulated in Cd(2+) and As(3+) transformed UROtsa cells. In addition, the malignant epithelial component of tumors derived from these cell lines were also down-regulated for SPARC expression, but the stromal cells recruited to these tumors was highly reactive for SPARC. This finding was shown to translate to specimens of human bladder cancer where tumor cells were SPARC negative, but stromal cells were positive. Acute exposure of UROtsa cells to both cadmium and arsenite reduced the expression of SPARC through a mechanism that did not involve changes in DNA methylation or histone acetylation. These studies suggest that environmental exposure to As(3+) or Cd(2+) can alter cell-cell and cell-matrix interactions in normal urothelial cells through a reduction in the expression of SPARC. The SPARC associated loss of cell-cell and cell-matrix contacts may participate in the multi-step process of bladder carcinogenesis.

Matricellular proteins: from homeostasis to inflammation, cancer, and metastasis

The family of matricellular proteins comprises molecules with disparate biology. The main characteristic of matricellular proteins is to be expressed during tissue renewal and repair in order to "normalize" the tissue. Tumors are wound that do not heal, and tumor growth and metastasis can be viewed as a consequence of aberrant homeostasis, during which matricellular proteins are often upregulated. In the tumor microenvironment, they can be produced by both tumor cells and surrounding stromal cells, such as fibroblasts and macrophages. In this context, matricellular proteins can exert several functions that actively contribute to tumor progression. They may (a) regulate cellular adhesion and migration and extracellular matrix deposition, (b) control tumor infiltration by macrophages or other leukocytes, (c) affect tumor angiogenesis, (d) regulate TGFbeta and other growth factor receptor signals, (e) directly stimulate integrin receptors to transduce pro-survival or pro-migratory signals, and (f) regulate the wnt/beta-catenin pathways. Most of these functions contribute to settle a chronic low inflammatory state, whose involvement in tissue transformation and tumor progression is now established.

Demethylating Agents in the Treatment of Cancer. Pharmaceuticals (Basel). 2010;3:2022-2044. [PMID: 27713340 PMCID: PMC4036667 DOI: 10.3390/ph3072022]

Gene silencing resulting from aberrant DNA methylation can lead to tumorigenesis. Therefore, drugs that inhibit or interfere with DNA methylation have been used to reactivate and induce silenced gene re-expression in malignancies. Two demethylating agents, azacitidine and decitabine, are approved for the treatment of myelodysplastic syndromes (MDS) by the U.S. Food and Drug Administration (FDA), and are now considered the standard of care in MDS. In this review, we discuss clinical data, including clinical benefits and toxicities, which led to the approval of azacitidine and decitabine. We also summarize findings from clinical trials that used these two demethylating agents in the treatment of solid tumors. Lastly, we discuss some limitations in the use of azacitidine and decitabine in cancer therapy.

Relationship and prognostic significance of SPARC and VEGF protein expression in colon cancer

Background

SPARC (secreted protein, acidic and rich in cysteine) is closely related with the progress, invasion and metastasis of malignant tumor and angiogenesis.

Methods

Using human colon adenocarcinoma tissues (hereinafter referred to as colon cancer) and their corresponding non-diseased colon from 114 patients' biopsies, the expression of SPARC and vascular endothelial growth factor (VEGF) were investigated by immunohistochemistry staining to assessment the relationship between SPARC and VEGF, as well as their prognostic significance in patients. Evaluation of VEGF expression level with the same tissues was used to establish the antigenic profiles, and the marker of CD34 staining was used as an indicator of microvessel density (MVD).

Results

SPARC expression was mainly in the stromal cells surrounding the colon cancer, and was significant difference in those tissues with the lymph node metastasis and differentiation degree of tumor. Expression of SPARC was significantly correlated with the expression of VEGF and MVD in colon cancer tissues. Patients with low or absence expressing SPARC had significantly worse overall survival and disease-free survival in a Single Factor Analysis; Cox Regression Analysis, SPARC emerged as an overall survival and disease-free survival independent prognostic factor for colon cancer.

Conclusion

The low expression or absence of stromal SPARC was an independent prognostic factor for poor prognosis of colon cancer. SPARC maybe involved in the regulation of anti-angiogenesis by which it may serve as a novel target for colon cancer treatment as well as a novel distinctive marker.

Epigenetic alterations differ in phenotypically distinct human neuroblastoma cell lines

BACKGROUND

Epigenetic aberrations and a CpG island methylator phenotype have been shown to be associated with poor outcomes in children with neuroblastoma (NB). Seven cancer related genes (THBS-1, CASP8, HIN-1, TIG-1, BLU, SPARC, and HIC-1) that have been shown to have epigenetic changes in adult cancers and play important roles in the regulation of angiogenesis, tumor growth, and apoptosis were analyzed to investigate the role epigenetic alterations play in determining NB phenotype.

METHODS

Two NB cell lines (tumorigenic LA1-55n and non-tumorigenic LA1-5s) that differ in their ability to form colonies in soft agar and tumors in nude mice were used. Quantitative RNA expression analyses were performed on seven genes in LA1-5s, LA1-55n and 5-Aza-dC treated LA1-55n NB cell lines. The methylation status around THBS-1, HIN-1, TIG-1 and CASP8 promoters was examined using methylation specific PCR. Chromatin immunoprecipitation assay was used to examine histone modifications along the THBS-1 promoter. Luciferase assay was used to determine THBS-1 promoter activity. Cell proliferation assay was used to examine the effect of 5-Aza-dC on NB cell growth. The soft agar assay was used to determine the tumorigenicity.

RESULTS

Promoter methylation values for THBS-1, HIN-1, TIG-1, and CASP8 were higher in LA1-55n cells compared to LA1-5s cells. Consistent with the promoter methylation status, lower levels of gene expression were detected in the LA1-55n cells. Histone marks associated with repressive chromatin states (H3K9Me3, H3K27Me3, and H3K4Me3) were identified in the THBS-1 promoter region in the LA1-55n cells, but not the LA1-5s cells. In contrast, the three histone codes associated with an active chromatin state (acetyl H3, acetyl H4, and H3K4Me3) were present in the THBS-1 promoter region in LA1-5s cells, but not the LA1-55n cells, suggesting that an accessible chromatin structure is important for THBS-1 expression. We also show that 5-Aza-dC treatment of LA1-55n cells alters the DNA methylation status and the histone code in the THBS-1 promoter modifies cell morphology, and inhibits their ability to form colonies in soft agar.

CONCLUSION

Our results suggest that epigenetic aberrations contribute to NB phenotype, and that tumorigenic properties can be inhibited by reversing the epigenetic changes with 5-Aza-dC.

Anti-angiogenic SPARC peptides inhibit progression of neuroblastoma tumors

Background

New, more effective strategies are needed to treat highly aggressive neuroblastoma. Our laboratory has previously shown that full-length Secreted Protein Acidic and Rich in Cysteine (SPARC) and a SPARC peptide corresponding to the follistatin domain of the protein (FS-E) potently block angiogenesis and inhibit the growth of neuroblastoma tumors in preclinical models. Peptide FS-E is structurally complex and difficult to produce, limiting its potential as a therapeutic in the clinic.

Results

In this study, we synthesized two smaller and structurally more simple SPARC peptides, FSEN and FSEC, that respectively correspond to the N-and C-terminal loops of peptide FS-E. We show that both peptides FSEN and FSEC have anti-angiogenic activity in vitro and in vivo, although FSEC is more potent. Peptide FSEC also significantly inhibited the growth of neuroblastoma xenografts. Histologic examination demonstrated characteristic features of tumor angiogenesis with structurally abnormal, tortuous blood vessels in control neuroblastoma xenografts. In contrast, the blood vessels observed in tumors, treated with SPARC peptides, were thin walled and structurally more normal. Using a novel method to quantitatively assess blood vessel abnormality we demonstrated that both SPARC peptides induced changes in blood vessel architecture that are consistent with blood vessel normalization.

Conclusion

Our results demonstrate that SPARC peptide FSEC has potent anti-angiogenic and anti-tumorigenic effects in neuroblastoma. Its simple structure and ease of production indicate that it may have clinical utility in the treatment of high-risk neuroblastoma and other types of pediatric and adult cancers, which depend on angiogenesis.

KLF4 inhibition of lung cancer cell invasion by suppression of SPARC expression

Krüppel-Like Factor 4 (KLF4) functions as a tumor suppressor in some cancers, but its molecular mechanism is not clear. Our recent study also showed that the expression of KLF4 is dramatically reduced in primary lung cancer tissues. To investigate the possible role of KLF4 in lung cancer, we stably transfected KLF4 into cells from lung cancer cell lines H322 and A549 to determine the cells' invasion ability. Our results showed that ectopic expression of KLF4 extensively suppressed lung cancer cell invasion in Matrigel. This effect was independent of KLF4-mediated p21 up-regulation because ectopic expression of p21 had minimal effect on cell invasion. Our analysis of the expression of 12 genes associated with cell invasion in parental, vector-transfected, and KLF4-transfected cells showed that ectopic expression of KLF4 resulted in extensively repressed expression of secreted protein acidic and rich in cysteine (SPARC), an extracellular matrix protein that plays a role in tumor development and metastasis. Knockdown of SPARC expression in H322 and A549 cells led to suppression of cell invasion, comparable to that observed in KLF4-transfected cells. Moreover, retrovirus-mediated restoration of SPARC expression in KLF4-transfected cells abrogated KLF4-induced anti-invasion activity. Together, our results indicate that KLF4 inhibits lung cancer cell invasion by suppressing SPARC gene expression.

Methylation of the SPARC gene promoter and its clinical implication in pancreatic cancer

Background

The secreted protein acidic and rich in cysteine (SPARC) plays a pivotal role in regulating cell-matrix interactions and tumor angiogenesis, proliferation, and migration. Detection of SPARC gene methylation may be useful as a tumorigenesis marker for early detection of pancreatic cancer.

Methods

Methylation of the SPARC gene transcriptional regulation region (TRR) was detected using bisulfite-specific (BSP) PCR-based sequencing analysis in 40 cases of pancreatic cancer and the adjacent normal tissues, 6 chronic pancreatitis tissues, and 6 normal pancreatic tissues. BSP cloning-based sequencing analysis was also performed in selected cases. Clinicopathological data from the cancer patients were collected and analyzed.

Results

Analysis of SPARC gene TRR methylation showed two hypermethylation wave peak regions: CpG Region 1 (CpG site 1-7) and CpG Region 2 (CpG site 8-12). Pancreatic tissues have shown methylation in both regions with gradual increases from normal, chronic pancreatitis, and adjacent normal tissues to cancerous tissues. However, Methylation of CpG Region 2 was more sensitive than CpG Region 1 in pancreatic tumorigenesis. Furthermore, the methylation level of CpG Region 2 was associated with increased tumor size and exposure to the risk factors (tobacco smoke and alcohol consumption) for developing pancreatic cancer.

Conclusion

Methylation of the SPARC gene, specifically CpG Region 2, may be an early event during pancreatic tumorigenesis and should be further evaluated as a tumorigenesis marker for early detection of pancreatic cancer.

Gene expression analysis identifies over-expression of CXCL1, SPARC, SPP1, and SULF1 in gastric cancer

To elucidate gene expression signatures associated with gastric carcinogenesis, we performed a genome-wide expression analysis of 46 Finnish and 20 Japanese gastric tissues. Comparative analysis between Finnish and Japanese datasets identified 58 common genes that were differentially expressed between cancerous and non-neoplastic gastric tissues. Twenty-six of these genes were up-regulated in cancer and 32 down-regulated. Of these genes, 64% were also differentially expressed in another unrelated publicly available dataset. The expression levels of four of the up-regulated genes, CXCL1, SPARC, SPP1 and SULF, were further analyzed in 82 gastric tissues using quantitative real-time RT-PCR. This analysis validated the results from the microarray analysis as the expression of these four genes was significantly higher in the cancerous tissue compared with the normal tissue (fold change 3.4-8.9). Over-expression of CXCL1 also positively correlated with improved survival. To conclude, irrespective of the microarray platform or patient population, a common gastric cancer gene expression signature of 58 genes, including CXCL1, SPARC, SPP1, and SULF, was identified. These genes represent potential biomarkers for gastric cancer.

Lack of host SPARC enhances vascular function and tumor spread in an orthotopic murine model of pancreatic carcinoma

Utilizing subcutaneous tumor models, we previously validated SPARC (secreted protein acidic and rich in cysteine) as a key component of the stromal response, where it regulated tumor size, angiogenesis and extracellular matrix deposition. In the present study, we demonstrate that pancreatic tumors grown orthotopically in Sparc-null (Sparc(-/-)) mice are more metastatic than tumors grown in wild-type (Sparc(+/+)) littermates. Tumors grown in Sparc(-/-) mice display reduced deposition of fibrillar collagens I and III, basement membrane collagen IV and the collagen-associated proteoglycan decorin. In addition, microvessel density and pericyte recruitment are reduced in tumors grown in the absence of host SPARC. However, tumors from Sparc(-/-) mice display increased permeability and perfusion, and a subsequent decrease in hypoxia. Finally, we found that tumors grown in the absence of host SPARC exhibit an increase in alternatively activated macrophages. These results suggest that increased tumor burden in the absence of host SPARC is a consequence of reduced collagen deposition, a disrupted vascular basement membrane, enhanced vascular function and an immune-tolerant, pro-metastatic microenvironment.

Molecular characterization of chronic obstructive pulmonary disease-related non-small cell lung cancer through aberrant methylation and alterations of EGFR signaling

BACKGROUND

The aim of this study was to evaluate the molecular influence of chronic obstructive pulmonary diseases (COPD) on the pathogenesis of non-small cell lung cancer (NSCLC).

MATERIALS AND METHODS

The methylation profiles of 12 genes, and the epidermal growth factor receptor (EGFR) and KRAS mutations were determined for samples from 229 NSCLC patients. In addition, protein expression of EGFR and HER2 in 116 NSCLCs was analyzed based on the presence or absence of COPD.

RESULTS

IL-12Rbeta2 and Wif-1 methylation and HER2 overexpression were more frequent events in the COPD group. Eighty nonmalignant lung tissues had no correlation with any molecular changes between the COPD and the non-COPD group. EGFR mutation was significantly higher in the non-COPD group, while EGFR expression was inversely correlated with %FEV1.0. In the COPD group, unmethylated SPARC and sFRP-2 genes or a negative CpG island methylator phenotype (CIMP) was a negative prognostic factor, while methylation of p16(INK4A) and WNT antagonist genes was a negative prognostic factor in the non-COPD group.

CONCLUSIONS

Novel characteristics of COPD-related NSCLC were identified by examination of methylation profiles and alterations of EGFR signaling. In consideration of the high sensitivity to smoking in patients with COPD, NSCLC with COPD might be a distinct population of smoke-related NSCLC, the genetic profile of which is quite different from non-COPD NSCLC.

SPARC: a matricellular regulator of tumorigenesis

Although many clinical studies have found a correlation of SPARC expression with malignant progression and patient survival, the mechanisms for SPARC function in tumorigenesis and metastasis remain elusive. The activity of SPARC is context- and cell-type-dependent, which is highlighted by the fact that SPARC has shown seemingly contradictory effects on tumor progression in both clinical correlative studies and in animal models. The capacity of SPARC to dictate tumorigenic phenotype has been attributed to its effects on the bioavailability and signaling of integrins and growth factors/chemokines. These molecular pathways contribute to many physiological events affecting malignant progression, including extracellular matrix remodeling, angiogenesis, immune modulation and metastasis. Given that SPARC is credited with such varied activities, this review presents a comprehensive account of the divergent effects of SPARC in human cancers and mouse models, as well as a description of the potential mechanisms by which SPARC mediates these effects. We aim to provide insight into how a matricellular protein such as SPARC might generate paradoxical, yet relevant, tumor outcomes in order to unify an apparently incongruent collection of scientific literature.

The role of SPARC in the TRAMP model of prostate carcinogenesis and progression

SPARC (Secreted Protein Acidic and Rich in Cysteine), is a matricellular glycoprotein that is produced by tumor and/or neighboring stroma. In human prostate cancer, SPARC immunoreactivity is highest in metastatic lesions but distinct contributions of tumoral and stromal SPARC to tumorigenesis and progression are unclear. To determine the role of SPARC in primary prostate tumorigenesis, we crossed SPARC-null (SP(-/-)) with TRAMP (Transgenic Adenocarcinoma of Mouse Prostate) mice. TRAMP(+)/SP(-/-) mice exhibited accelerated cancer development and progression. Compared to their TRAMP(+)/SP(-/-) counterparts, TRAMP(+)/SP(+/+) tumors had fewer proliferating cells, and decreased cyclins A and D1 with increased p21(Cip) and p27(Kip). Similar effects on proliferation and cell-cycle regulators were observed in human prostate cancer cell lines, transiently transfected with pSPARC. TRAMP(+)/SP(-/-) tumors exhibited decreased stromal collagen, enhanced matrix metalloproteinase activity and increased vascular endothelial growth factor, proinflammatory cytokines. To determine the contribution of stromal SPARC, we evaluated subcutaneous tumor growth of TRAMP cell lines in syngeneic SP(+/+) and SP(-/-) mice. Enhanced growth, decreased stromal collagen and increased proteolysis were noted in SP(-/-) mice. Our findings demonstrate that both tumor and stromal SPARC are limiting for primary prostate tumorigenesis and progression, through effects on the cell cycle and the creation of a less favorable tumor microenvironment.

Aberrant promoter methylation of SPARC in ovarian cancer

Epigenetic silencing of tumor suppressor genes is a new focus of investigation in the generation and proliferation of carcinomas. Secreted protein acidic and rich in cysteine (SPARC) is reportedly detrimental to the growth of ovarian cancer cells and has been shown to be epigenetically silenced in several cancers. We hypothesized that SPARC is downregulated in ovarian cancer through aberrant promoter hypermethylation. To that end, we analyzed SPARC expression in ovarian cancer cell lines and investigated the methylation status of the Sparc promoter using methylation-specific polymerase chain reaction. Our results show that SPARC mRNA expression is decreased in three (33%) and absent in four (44%) of the nine ovarian cancer cell lines studied, which correlated with hypermethylation of the Sparc promoter. Treatment with the demethylating agent 5-aza-2'-deoxycytidine rescued SPARC mRNA and protein expression. Addition of exogenous SPARC, as well as ectopic expression by an adenoviral vector, resulted in decreased proliferation of ovarian cancer cell lines. Investigation of primary tumors revealed that the Sparc promoter is methylated in 68% of primary ovarian tumors and that the levels of SPARC protein decrease as the disease progresses from low to high grade. Lastly, de novo methylation of Sparc promoter was shown to be mediated by DNA methyltransferase 3a. These results implicate Sparc promoter methylation as an important factor in the genesis and survival of ovarian carcinomas and provide new insights into the potential use of SPARC as a novel biomarker and/or treatment modality for this disease.

Inflammation-dependent expression of SPARC during development of chronic pancreatitis in WBN/Kob rats and a microarray gene expression analysis

The pathophysiology of human chronic pancreatitis is not well understood and difficult to follow on a molecular basis. Therefore, we used a rat model [Wistar-Bonn/Kobori (WBN/Kob)] that exhibits spontaneous chronic inflammation and fibrosis in the pancreas. Using microarrays we compared gene expression patterns in the pancreas during development of inflammation and fibrosis of WBN/Kob rats with age-matched healthy Wistar rats. The extracellular matrix protein SPARC (secreted protein, acidic, and rich in cysteines) and other transcripts of inflammatory genes were quantified by real-time PCR, and some were localized by immunohistochemistry. When pancreatic inflammation becomes obvious at the age of 16 wk, several hundred genes are increased between 3- and 50-fold in WBN/Kob rats compared with healthy Wistar rats. Proteins produced by acinar cells and characteristic for inflammation, e.g., pancreatitis-associated protein, are highly upregulated. Other proteins, derived from infiltrating inflammatory cells and from activated stellate cells (fibrosis) such as collagens and fibronectins are also significantly upregulated. SPARC was localized to acinar cells where it increased in the vicinity of inflammatory foci. However, acinar expression of SPARC was lost during destruction of acinar cells. In human pancreatic specimens with chronic pancreatitis, SPARC exhibited a similar expression profile. During chronic inflammation and fibrosis in the WBN/Kob rat, inflammatory genes, growth factors, and structural genes exhibit a high increase of expression. A temporal profile including pre- and postinflammatory phases indicates a concurrent activation of inflammatory and fibrotic changes. Inflammation dependent expression of SPARC appears to be lost during acinar-to-duct metaplasia both in rat and human pancreas.

Improved effectiveness of nanoparticle albumin-bound (nab) paclitaxel versus polysorbate-based docetaxel in multiple xenografts as a function of HER2 and SPARC status

Nanoparticle albumin-bound (nab)-paclitaxel (Abraxane) is an albumin-bound 130-nm particle form of paclitaxel that demonstrated higher efficacy and was well tolerated compared with solvent-based paclitaxel (Taxol) and docetaxel (Taxotere) in clinical trials for metastatic breast cancer. Nab-paclitaxel enhances tumor targeting through gp60 and caveolae-mediated endothelial transcytosis and the association with the albumin-binding protein SPARC (secreted protein, acidic and rich in cysteine) in the tumor microenvironment. The overexpression of human epidermal growth factor receptor-2 (HER2) in breast cancer has been shown to correlate with resistance to paclitaxel. To evaluate the importance of HER2 and SPARC status in determining the relative efficacy of nab-paclitaxel compared with polysorbate-based docetaxel, nude mice bearing six different human tumor xenografts were treated with nab-paclitaxel (MX-1: 15 mg/kg, once a week for 3 weeks; LX-1, MDA-MB-231/HER2+, PC3, and HT29: 50 and 120 mg/kg, every 4 days three times ; MDA-MB-231: 120 and 180 mg/kg, every 4 days three times) and polysorbate-based docetaxel (15 mg/kg). HER2 and SPARC status were analyzed by RT-PCR and immunohistochemical staining. MDA-MB-231 and MX-1 breast and LX-1 lung cancers were HER2 negative and low in SPARC expression. Nab-paclitaxel at submaximum-tolerated dosage was significantly more effective than polysorbate-based docetaxel at its maximum-tolerated dosage in these three HER2-negative tumors. The HER2-positive tumors had variable SPARC expression, with MDA-MB-231/HER2+ <PC3 <HT29. In these HER2-positive tumors, nab-paclitaxel was equal to or better than polysorbate-based docetaxel in tumors with medium to high SPARC levels (PC3 and HT29), but not in MDA-MB-231/HER2+ tumors with low SPARC expression. These results demonstrated that the relative efficacy of nab-paclitaxel was significantly higher compared with polysorbate-based docetaxel in HER2-negative tumors (three of three) and in HER2-positive tumors with high levels of SPARC. HER2 and SPARC expression may be useful biomarkers in determining antitumor effectiveness for taxanes.

Macrophage-derived SPARC bridges tumor cell-extracellular matrix interactions toward metastasis

Other than genetic imprinting and epithelial to mesenchymal transition, cancer cells need interaction with the nearby stroma toward metastasis. Secreted protein acidic and rich in cysteine (SPARC) is a matricellular protein known to regulate extracellular matrix (ECM) deposition and cell-ECM interaction. Gene expression profiles associate SPARC to malignant progression. Using reciprocal bone marrow chimeras between SPARC knockout and wild-type mice, we show that SPARC produced by inflammatory cells is necessary for spontaneous, but not experimental, i.v. metastasis. Macrophage-derived SPARC induces cancer cell migration and enhances their migration to other ECM proteins at least through alpha(v)beta(5) integrin. Indeed, RNA interference knockdown of beta(5) integrin expression reduces cell migration in vitro and metastasis in vivo. Together these results show that macrophage-derived SPARC takes part in metastasis, acting at the step of integrin-mediated migration of invasive cells.

SPARC in cancer biology: its role in cancer progression and potential for therapy. Drug Resist Updat. 2008;11:231-246. [PMID: 18849185 DOI: 10.1016/j.drup.2008.08.005]

The ability to effectively target a tumor to achieve complete regression and cure is the ultimate goal that drives our need to better understand tumor biology. Recently, SPARC has generated considerable interest as a multi-faceted protein that belongs to a family of matricellular proteins. It functions not only to modulate cell-cell and cell-matrix interactions, but its de-adhesive and growth inhibitory properties in non-transformed cells have led to studies to assess its role in cancer. Its divergent actions reflect the complexity of this protein, because in certain types of cancers, such as melanomas and gliomas, SPARC is associated with a highly aggressive tumor phenotype, while in others, mainly ovarian, neuroblastomas and colorectal cancers, SPARC may function as a tumor suppressor. Recent studies have also demonstrated a role for SPARC in sensitizing therapy-resistant cancers. Here, the role of SPARC in cancer progression and its potential application in cancer therapy is discussed.

SPARC ameliorates ovarian cancer-associated inflammation

We have recently identified that the role of secreted protein acidic and rich in cysteine (SPARC) in amelioration of peritoneal ovarian carcinomatosis is mediated, at least in part, through mesothelial cell/lysophosphatidic acid-induced inflammatory response in ovarian cancer cells. The aim of this study was to elucidate the molecular mechanisms of the interactions between tumor cells and the cellular components of the ovarian cancer peritoneal microenvironment, specifically, mesothelial cells and macrophages. We found that SPARC not only significantly reduced macrophage chemoattractant protein-1 production and its macrophage chemotactic effect, but also attenuated the response of ovarian cancer cells to the mitogenic and proinvasive effects of macrophage chemo-attractant protein-1 and decreased macrophage-induced cancer cell invasiveness. Overexpression of SPARC in ovarian cancer cells significantly attenuated macrophage- and mesothelial cell-induced production and activity of interleukin-6, prostanoids (prostaglandins E2 and 8-isoprostanes) as well as matrix metalloproteinases and urokinase plasminogen activator. Moreover, the effects of SPARC overexpression in ovarian cancer cells were mediated, in part, through inhibition of nuclear factor-kappaB promoter activation. These results indicate, for the first time, that the effects of tumor SPARC as a negative regulator of ovarian cancer are mediated through decreased recruitment of macrophages and downregulation of the associated inflammation.

The nonsteroidal anti-inflammatory drug NS398 reactivates SPARC expression via promoter demethylation to attenuate invasiveness of lung cancer cells

Nonsteroidal anti-inflammatory drugs (NSAIDs) have been shown to exhibit potent anticancer effects in vitro and in vivo. One of the mechanisms by which NSAIDs suppress tumorigenesis is inhibition of angiogenesis and metastasis. In this study, we used a microarray system to study the change of expression profile of metastasis-related genes regulated by NS398, a NSAID and a cyclooxygenase-2 (COX-2) inhibitor. We found that several negative regulators of cell invasion, including secreted protein acidic and rich in cysteine (SPARC), thrombospondin 1 (TSP-1), thrombospondin 3 (TSP-3), and tissue inhibitors of matrix metalloproteinase-2 (TIMP-2) are upregulated by NS398. In addition, we demonstrated that upregulation of SPARC expression by NS398 in human lung cancer cells is mediated by promoter demethylation and associated with a decrease in DNA methyltransferase (DNMT) expression. This is the first report to show that NS398 can inhibit the expression of DNMT1 and 3b. Functional assay indicated that SPARC is a critical mediator for NS398 to inhibit cell invasion. Our results provide new insights for the understanding of the anticancer actions of NSAIDs.

SPARC promoter hypermethylation in colorectal cancers can be reversed by 5-Aza-2'deoxycytidine to increase SPARC expression and improve therapy response. Br J Cancer. 2008;98:1810-1819. [PMID: 18458674 PMCID: PMC2410109 DOI: 10.1038/sj.bjc.6604377]

Poor clinical outcomes in cancer can often be attributed to inadequate response to chemotherapy. Strategies to overcome either primary or acquired chemoresistance may ultimately impact on patients' survival favourably. We previously showed that lower levels of SPARC were associated with therapy-refractory colorectal cancers (CRC), and that upregulating its expression enhances chemo-sensitivity resulting in greater tumour regression in vivo. Here, we examined aberrant hypermethylation of the SPARC promoter as a potential mechanism for repressing SPARC in CRCs and whether restoration of its expression with a demethylating agent 5-Aza-2′deoxycytidine (5-Aza) could enhance chemosensitivity. Initially, the methylation status of the SPARC promoter from primary human CRCs were assessed following isolation of genomic DNA from laser capture microdissected specimens by direct DNA sequencing. MIP101, RKO, HCT 116, and HT-29 CRC cell lines were also used to evaluate the effect of 5-Aza on: SPARC promoter methylation, SPARC expression, the interaction between DNMT1 and the SPARC promoter (ChIP assay), cell viability, apoptosis, and cell proliferation. Our results revealed global hypermethylation of the SPARC promoter in CRCs, and identified specific CpG sites that were consistently methylated in CRCs but not in normal colon. We also demonstrate that SPARC repression in CRC cell lines could be reversed following exposure to 5-Aza, which resulted in increased SPARC expression, leading to a significant reduction in cell viability (by an additional 39% in RKO cells) and greater apoptosis (an additional 18% in RKO cells), when combined with 5-FU in vitro (in comparison to 5-FU alone). Our exciting findings suggest potential diagnostic markers of CRCs based on specific methylated CpG sites. Moreover, the results reveal the therapeutic utility of employing demethylating agents to improve response through augmentation of SPARC expression.