Maspin is not required for embryonic development or tumour suppression

Risk signature identification and NPRL2 affects sunitinib sensitivity in clear cell renal cell carcinoma

Tumor suppressor genes (TSGs) play a crucial role in tumorigenesis and drug resistance. We analyzed the subtypes of clear cell renal cell carcinoma (ccRCC) mediated by 8 genes contained in the 3p21.3 tumor suppressor gene cluster and their effects on TME cell infiltration based on the TCGA database. The risk score model was established by principal component analysis. The hub gene NPRL2 was selected by protein-protein interactions (PPI) analysis. The effect of NPRL2 on sunitinib sensitivity of ccRCC was verified by using CCK-8, colony formation assay, wound healing assay, transwell assay and xenograft tumor model. Changes in protein expression were detected by Western blotting. We found that 8 TSGs were all differentially expressed in ccRCC samples, which could divide ccRCC into two subtypes. The constructed risk score model could predict the prognosis and drug sensitivity of ccRCC patients, and was an independent prognostic factor for ccRCC. Over-expression of NPRL2 promoted apoptosis, inhibited EMT, decreased the phosphorylation of the PI3K/AKT/mTOR signaling pathway to inhibit its activity, and promoted the sensitivity of sunitinib to ccRCC cells. Collectively, our findings increased the understanding of TSGs in ccRCC, suggesting that NPRL2 as a TSG could enhance sunitinib sensitivity to ccRCC cells.

Widespread discrepancy in Nnt genotypes and genetic backgrounds complicates granzyme A and other knockout mouse studies

Granzyme A (GZMA) is a serine protease secreted by cytotoxic lymphocytes, with Gzma-/- mouse studies having informed our understanding of GZMA's physiological function. We show herein that Gzma-/- mice have a mixed C57BL/6J and C57BL/6N genetic background and retain the full-length nicotinamide nucleotide transhydrogenase (Nnt) gene, whereas Nnt is truncated in C57BL/6J mice. Chikungunya viral arthritis was substantially ameliorated in Gzma-/- mice; however, the presence of Nnt and the C57BL/6N background, rather than loss of GZMA expression, was responsible for this phenotype. A new CRISPR active site mutant C57BL/6J GzmaS211A mouse provided the first insights into GZMA's bioactivity free of background issues, with circulating proteolytically active GZMA promoting immune-stimulating and pro-inflammatory signatures. Remarkably, k-mer mining of the Sequence Read Archive illustrated that ≈27% of Run Accessions and ≈38% of BioProjects listing C57BL/6J as the mouse strain had Nnt sequencing reads inconsistent with a C57BL/6J genetic background. Nnt and C57BL/6N background issues have clearly complicated our understanding of GZMA and may similarly have influenced studies across a broad range of fields.

The roles of MASPIN expression and subcellular localization in non-small cell lung cancer

Accumulating studies have confirmed that mammary serine protease inhibitor (MASPIN) plays an essential role in non-small cell lung cancer (NSCLC). However, results are still controversial or inconsistent. In the present study, we attempted to identify the clinical significance of MASPIN and its potential molecular roles in NSCLC. The correlation of MASPIN with prognosis and clinicopathological characteristics was assessed by meta-analysis. Additionally, the potential molecular mechanisms of MASPIN in NSCLC was also investigated through several online databases. A total of 2220 NSCLC patients from 12 high quality studies were included and the results indicated that up-regulated MASPIN nucleus and cytoplasm expression was associated with poor overall survival (OS) (hazard ratio (HR) = 1.43, 95% confidence interval (CI) = 1.01–2.04, P<0.05), elevated MASPIN cytoplasm expression was associated with poor OS (HR = 1.45, 95% CI = 1.01–2.07, P<0.05), disease-free survival (DFS) (HR = 1.95, 95% CI = 1.31–2.88, P=0.001), and disease-specific survival (DSS) (HR = 2.17, 95% CI = 1.18–3.99, P=0.013). MASPIN both nucleus and cytoplasm location were associated with clinicopathological characteristics. Bioinformatics analysis validated the above results and suggested that human serpin family B member 5 (SERPINB5) hypomethylated levels were negatively correlated with its mRNA expression. Bioinformatics analysis also revealed the 85 most frequently altered neighboring genes of SERPINB5, and gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis revealed 20 GO terms and 3 KEGG pathways with statistical significance. MASPIN had a statistically negative correlation with NSCLC prognosis, functioning as an oncoprotein by hypomethylation and influencing specific pathways involving the 85 genes identified herein. MASPIN might be a promising prognostic signature in NSCLC.

Serine protease inhibitors and human wellbeing interplay: new insights for old friends

Serine Protease Inhibitors (Serpins) control tightly regulated physiological processes and their dysfunction is associated to various diseases. Thus, increasing interest is given to these proteins as new therapeutic targets. Several studies provided functional and structural data about human serpins. By comparison, only little knowledge regarding bacterial serpins exists. Through the emergence of metagenomic studies, many bacterial serpins were identified from numerous ecological niches including the human gut microbiota. The origin, distribution and function of these proteins remain to be established. In this report, we shed light on the key role of human and bacterial serpins in health and disease. Moreover, we analyze their function, phylogeny and ecological distribution. This review highlights the potential use of bacterial serpins to set out new therapeutic approaches.

SerpinB2 inhibits migration and promotes a resolution phase signature in large peritoneal macrophages

SerpinB2 (plasminogen activator inhibitor type 2) has been called the “undecided serpin” with no clear consensus on its physiological role, although it is well described as an inhibitor of urokinase plasminogen activator (uPA). In macrophages, pro-inflammatory stimuli usually induce SerpinB2; however, expression is constitutive in Gata6+ large peritoneal macrophages (LPM). Interrogation of expression data from human macrophages treated with a range of stimuli using a new bioinformatics tool, CEMiTool, suggested that SerpinB2 is most tightly co- and counter-regulated with genes associated with cell movement. Using LPM from SerpinB2^−/− and SerpinB2^R380A (active site mutant) mice, we show that migration on Matrigel was faster than for their wild-type controls. Confocal microscopy illustrated that SerpinB2 and F-actin staining overlapped in focal adhesions and lamellipodia. Genes associated with migration and extracellular matrix interactions were also identified by RNA-Seq analysis of migrating RPM from wild-type and SerpinB2^R380A mice. Subsequent gene set enrichment analyses (GSEA) suggested SerpinB2 counter-regulates many Gata6-regulated genes associated with migration. These data argue that the role of SerpinB2 in macrophages is inhibition of uPA-mediated plasmin generation during cell migration. GSEA also suggested that SerpinB2 expression (likely via ensuing modulation of uPA-receptor/integrin signaling) promotes the adoption of a resolution phase signature.

Synthetically controlling dendrimer flexibility improves delivery of large plasmid DNA

Tools for editing the genome and epigenome have revolutionised the field of molecular biology and represent a new frontier in targeted therapeutic intervention. Although efficiencies and specificities of genome editing technologies have improved with the development of TALEs and CRISPR platforms, intracellular delivery of these larger constructs still remains a challenge using existing delivery agents. Viral vectors, including lentiviruses and adeno-associated viruses, as well as some non-viral strategies, such as cationic polymers and liposomes, are limited by packaging capacity, poor delivery, toxicity, and immunogenicity. We report a highly controlled synthetic strategy to engineer a flexible dendritic polymer using click chemistry to overcome the aforementioned delivery challenges associated with genome engineering technologies. Using a systematic approach, we demonstrate that high transfection efficiencies and packaging capacity can be achieved using this non-viral delivery methodology to deliver zinc fingers, TALEs and CRISPR/dCas9 platforms.

IKKα inibition by a glucosamine derivative enhances Maspin expression in osteosarcoma cell line

Chronic inflammation has been associated to cancer development by the alteration of several inflammatory pathways, such as Nuclear Factor-κB pathway. In particular, IκB kinase α (IKKα), one of two catalytic subunit of IKK complex, has been described to be associated to cancer progression and metastasis in a number of cancers. The molecular mechanism by which IKKα affects cancer progression is not yet completely clarified, anyway an association between IKKα and the expression of Maspin (Mammary Serine Protease Inhibitor or SerpinB5), a tumor suppressor protein, has been described. IKKα shuttles between cytoplasm and nucleus, and when is localized into the nuclei, IKKα regulates the expression of several genes, among them Maspin gene, whose expression is repressed by high amount of nuclear IKKα. Considering that high levels of Maspin have been associated with reduced metastatic progression, it could be hypothesized that the repression of IKKα nuclear translocation could be associated with the repression of metastatic phenotype. The present study is aimed to explore the ability of a glucosamine derivative, 2-(N-Carbobenzyloxy)l-phenylalanylamido-2-deoxy-β-d-glucose (NCPA), synthesized in our laboratory, to stimulate the production of Maspin in an osteosarcoma cell line, 143B. Immunofluorescence and Western blotting experiments showed that NCPA is able to inhibit IKKα nuclear translocation, and to stimulate Maspin production. Moreover, in association with stimulation of Maspin production we found the decrease of β1 Integrin expression, the down-regulation of metalloproteases MMP-9 and MMP-13 production and cell migration inhibition. Taking in account that β1 Integrin and MMP-9 and -13 have been correlated with the invasiveness of osteosarcoma, considering that NCPA affects the invasiveness of 143B cell line, we suggest that this molecule could affect the osteosarcoma metastatic ability.

An Essential Role of Maspin in Embryogenesis and Tumor Suppression

Maspin (SerpinB5) is an epithelial-specific tumor suppressor gene product that displays context-dependent cellular functions. Maspin-deficient mouse models created to date have not definitively established maspin functions critical for cancer suppression. In this study, we generated a mouse strain in which exon 4 of the Maspin gene was deleted, confirming its essential role in development but also enabling a breeding scheme to bypass embryonic lethality. Phenotypic characterization of this viable strain established that maspin deficiency was associated with a reduction in maximum body weight and a variety of context-dependent epithelial abnormalities. Specifically, maspin-deficient mice exhibited pulmonary adenocarcinoma, myoepithelial hyperplasia of the mammary gland, hyperplasia of luminal cells of dorsolateral and anterior prostate, and atrophy of luminal cells of ventral prostate and stratum spinosum of epidermis. These cancer phenotypes were accompanied by increased inflammatory stroma. These mice also displayed the autoimmune disorder alopecia aerate. Overall, our findings defined context-specific tumor suppressor roles for maspin in a clinically relevant model to study maspin functions in cancer and other pathologies. Cancer Res; 77(4); 886-96. ©2017 AACR.

Mice Lacking Brinp2 or Brinp3, or Both, Exhibit Behaviors Consistent with Neurodevelopmental Disorders

Background:Brinps 1–3, and Astrotactins (Astn) 1 and 2, are members of the Membrane Attack Complex/Perforin (MACPF) superfamily that are predominantly expressed in the mammalian brain during development. Genetic variation at the human BRINP2/ASTN1 and BRINP1/ASTN2 loci has been implicated in neurodevelopmental disorders. We, and others, have previously shown that Brinp1^−/− mice exhibit behavior reminiscent of autism spectrum disorder (ASD) and attention deficit hyperactivity disorder (ADHD).

Method: We created Brinp2^−/− mice and Brinp3^−/− mice via the Cre-mediated LoxP system to investigate the effect of gene deletion on anatomy and behavior. Additionally, Brinp2^−/−Brinp3^−/− double knock-out mice were generated by interbreeding Brinp2^−/− and Brinp3^−/− mice. Genomic validation was carried out for each knock-out line, followed by histological, weight and behavioral examination. Brinp1^−/−Brinp2^−/−Brinp3^−/− triple knock-out mice were also generated by crossing Brinp2/3 double knock-out mice with previously generated Brinp1^−/− mice, and examined by weight and histological analysis.

Results:Brinp2^−/− and Brinp3^−/− mice differ in their behavior: Brinp2^−/− mice are hyperactive, whereas Brinp3^−/− mice exhibit marked changes in anxiety-response on the elevated plus maze. Brinp3^−/− mice also show evidence of altered sociability. Both Brinp2^−/− and Brinp3^−/− mice have normal short-term memory, olfactory responses, pre-pulse inhibition, and motor learning. The double knock-out mice show behaviors of Brinp2^−/− and Brinp3^−/− mice, without evidence of new or exacerbated phenotypes.

Conclusion:Brinp3 is important in moderation of anxiety, with potential relevance to anxiety disorders. Brinp2 dysfunction resulting in hyperactivity may be relevant to the association of ADHD with chromosome locus 1q25.2. Brinp2^−/− and Brinp3^−/− genes do not compensate in the mammalian brain and likely have distinct molecular or cell-type specific functions.

Egg serpins: The chicken and/or the egg dilemma

Twenty-seven serpins belonging to clade A, B, C, D, E, F, G, H and I serpins are currently referenced in chicken genome databases. Phylogenetic analysis of chicken serpins revealed that ovalbumin (Serpinb14) and its paralogs ovalbumin-related protein Y (Serpinb14b) and ovalbumin-related protein X (Serpinb14c) are found in bird species. These clade B serpins are specifically expressed in reproductive tissues and exported in the egg where they constitute major protein components. These data suggest that these three paralogs have probably appeared in birds to face new environments and ensure the extra-uterine development of an embryo in a shell egg. Twelve other serpins have been identified in the newly produced egg, some of them having a specific distribution in the respective egg structures (eggshell, egg white, vitelline membrane and egg yolk). The physiological role of these egg serpins remain largely unexplored, but there is increasing evidence in literature or by homologies with their mammalian counterparts, that some of them participate in cell proliferation, tissue remodeling and/or angiogenesis associated with folliculogenesis and development of extraembryonic structures, eggshell biomineralization, egg defense and nutrition of the embryo. A better knowledge of the phylogenetic evolution of these 15 serpins in other oviparous species, on their egg distribution, on their regulation during embryonic development (activation/degradation/transfer) and on their functional specificity, is needed to better appreciate their role and their bird-specificity. These review shed light on the multiple possibilities that offer the avian egg model to study the role of serpins in reproduction and developmental biology.

SERPINB5 Promoter Hypomethylation Differentiates Pancreatic Ductal Adenocarcinoma From Pancreatitis

OBJECTIVES

The diagnosis of pancreatic ductal adenocarcinoma (PDAC) is challenging in the setting of pancreatitis. We investigated SERPINB5 for its impact on PDAC tumor biology and its use as a diagnostic marker for PDAC in the setting of pancreatitis.

METHODS

Patient samples from PDAC primary tumors, PDAC lymph node metastases, and pancreatitis were investigated for SERPINB5 promoter methylation by methylation-specific polymerase chain reaction (PCR). Six PDAC cell lines were investigated in vitro and in vivo using an orthotopic mouse model to generate primary tumors and metastases. SERPINB5 mRNA expression, protein expression, and promoter methylation were determined by quantitative reverse transcriptase-PCR, methylation-specific PCR, and Western Blot.

RESULTS

In patient samples, detection of an unmethylated SERPINB5 promoter differentiated pancreatitis from PDAC with a sensitivity of 57% and a specificity of 95% (P < 0.001). SERPINB5 was not deregulated in primary tumors versus metastases, but primary tumors without SERPINB5 protein expression had significantly reduced viability (P = 0.02).

CONCLUSIONS

SERPINB5 seems to assume an oncogenic role in PDAC. In clinical samples, detection of unmethylated SERPINB5 was a specific marker for PDAC even in the context of pancreatitis and may provide the basis for a liquid biopsy option to detect PDAC.

Effects of Noninhibitory Serpin Maspin on the Actin Cytoskeleton: A Quantitative Image Modeling Approach

Recent developments in quantitative image analysis allow us to interrogate confocal microscopy images to answer biological questions. Clumped and layered cell nuclei and cytoplasm in confocal images challenges the ability to identify subcellular compartments. To date, there is no perfect image analysis method to identify cytoskeletal changes in confocal images. Here, we present a multidisciplinary study where an image analysis model was developed to allow quantitative measurements of changes in the cytoskeleton of cells with different maspin exposure. Maspin, a noninhibitory serpin influences cell migration, adhesion, invasion, proliferation, and apoptosis in ways that are consistent with its identification as a tumor metastasis suppressor. Using different cell types, we tested the hypothesis that reduction in cell migration by maspin would be reflected in the architecture of the actin cytoskeleton. A hybrid marker-controlled watershed segmentation technique was used to segment the nuclei, cytoplasm, and ruffling regions before measuring cytoskeletal changes. This was informed by immunohistochemical staining of cells transfected stably or transiently with maspin proteins, or with added bioactive peptides or protein. Image analysis results showed that the effects of maspin were mirrored by effects on cell architecture, in a way that could be described quantitatively.

Brinp1(-/-) mice exhibit autism-like behaviour, altered memory, hyperactivity and increased parvalbumin-positive cortical interneuron density

BACKGROUND

BMP/RA-inducible neural-specific protein 1 (Brinp1) is highly conserved in vertebrates, and continuously expressed in the neocortex, hippocampus, olfactory bulb and cerebellum from mid-embryonic development through to adulthood.

METHODS

Brinp1 knock-out (Brinp1(-/-)) mice were generated by Cre-recombinase-mediated removal of the third exon of Brinp1. Knock-out mice were characterised by behavioural phenotyping, immunohistochemistry and expression analysis of the developing and adult brain.

RESULTS

Absence of Brinp1 during development results in a behavioural phenotype resembling autism spectrum disorder (ASD), in which knock-out mice show reduced sociability and changes in vocalisation capacity. In addition, Brinp1(-/-) mice exhibit hyper-locomotor activity, have impaired short-term memory, and exhibit poor reproductive success. Brinp1(-/-) mice show increased density of parvalbumin-expressing interneurons in the adult mouse brain. Brinp1(-/-) mice do not show signs of altered neural precursor proliferation or increased apoptosis during late embryonic brain development. The expression of the related neuronal migration genes Astn1 and Astn2 is increased in the brains of Brinp1(-/-) mice, suggesting that they may ameliorate the effects of Brinp1 loss.

CONCLUSIONS

Brinp1 plays an important role in normal brain development and function by influencing neuronal distribution within the cortex. The increased cortical PV-positive interneuron density and altered behaviour of Brinp1(-/-) mice resemble features of a subset of human neurological disorders; namely autism spectrum disorder (ASD) and the hyperactivity aspect of attention deficit hyperactivity disorder (ADHD).

The role of cullin 5-containing ubiquitin ligases

The suppressor of cytokine signaling (SOCS) box consists of the BC box and the cullin 5 (Cul5) box, which interact with Elongin BC and Cul5, respectively. SOCS box-containing proteins have ubiquitin ligase activity mediated by the formation of a complex with the scaffold protein Cul5 and the RING domain protein Rbx2, and are thereby members of the cullin RING ligase superfamily. Cul5-type ubiquitin ligases have a variety of substrates that are targeted for polyubiquitination and proteasomal degradation. Here, we review the current knowledge on the identification of Cul5 and the regulation of its expression, as well as the signaling pathways regulated by Cul5 and how viruses highjack the Cul5 system to overcome antiviral responses.

Re-expression of Selected Epigenetically Silenced Candidate Tumor Suppressor Genes in Cervical Cancer by TET2-directed Demethylation

DNA hypermethylation is extensively explored as therapeutic target for gene expression modulation in cancer. Here, we re-activated hypermethylated candidate tumor suppressor genes (TSGs) (C13ORF18, CCNA1, TFPI2, and Maspin) by TET2-induced demethylation in cervical cancer cell lines. To redirect TET2 to hypermethylated TSGs, we engineered zinc finger proteins (ZFPs), which were first fused to the transcriptional activator VP64 to validate effective gene re-expression and confirm TSG function. ChIP-Seq not only revealed enriched binding of ZFPs to their intended sequence, but also considerable off-target binding, especially at promoter regions. Nevertheless, results obtained by targeted re-expression using ZFP-VP64 constructs were in line with cDNA overexpression; both revealed strong growth inhibition for C13ORF18 and TFPI2, but not for CCNA1 and Maspin. To explore effectivity of locus-targeted demethylation, ZFP-TET2 fusions were constructed which efficiently demethylated genes with subsequent gene re-activation. Moreover, targeting TET2 to TFPI2 and C13ORF18, but not CCNA1, significantly decreased cell growth, viability, and colony formation in cervical cancer cells compared to a catalytically inactive mutant of TET2. These data underline that effective re-activation of hypermethylated genes can be achieved through targeted DNA demethylation by TET2, which can assist in realizing sustained re-expression of genes of interest.

The role of serpins in tumor cell migration

Tumor cells are characterized by uncontrolled cell growth at a primary site that is caused by genetic alterations. Tumor cells that metastasize from their primary site to distant locations are commonly referred to as malignant. Cell migration is a critical step in this process. The ability of tumor cells to migrate and invade is partly controlled by proteolytic enzymes. These enzymes are secreted by either the tumor cells themselves or adjacent cells. They represent all classes of proteases, including serine and cysteine proteases. Serine proteases, in particular urokinase plasminogen activator (uPA), initiate a proteolytic cascade that culminates in degrading components of the extracellular matrix (ECM). Some serine proteases are controlled by a superfamily of proteins known as serpins. This minireview provides an overview of serpins that are vital in regulating tumor cell migration and progressing cancer.

An in silico model to demonstrate the effects of Maspin on cancer cell dynamics

Most cancer treatments efficacy depends on tumor metastasis suppression, where tumor suppressor genes play an important role. Maspin (Mammary Serine Protease Inhibitor), an non-inhibitory serpin has been reported as a potential tumor suppressor to influence cell migration, adhesion, proliferation and apoptosis in in vitro and in vivo experiments in last two decades. Lack of computational investigations hinders its ability to go through clinical trials. Previously, we reported first computational model for maspin effects on tumor growth using artificial neural network and cellular automata paradigm with in vitro data support. This paper extends the previous in silico model by encompassing how maspin influences cell migration and the cell-extracellular matrix interaction in subcellular level. A feedforward neural network was used to define each cell behavior (proliferation, quiescence, apoptosis) which followed a cell-cycle algorithm to show the microenvironment impacts over tumor growth. Furthermore, the model concentrates how the in silico experiments results can further confirm the fact that maspin reduces cell migration using specific in vitro data verification method. The data collected from in vitro and in silico experiments formulates an unsupervised learning problem which can be solved by using different clustering algorithms. A density based clustering technique was developed to measure the similarity between two datasets based on the number of links between instances. Our proposed clustering algorithm first finds the nearest neighbors of each instance, and then redefines the similarity between pairs of instances in terms of how many nearest neighbors share the two instances. The number of links between two instances is defined as the number of common neighbors they have. The results showed significant resemblances with in vitro experimental data. The results also offer a new insight into the dynamics of maspin and establish as a metastasis suppressor gene for further molecular research.

Prognostic value of tumor suppressors in osteosarcoma before and after neoadjuvant chemotherapy

Background

Primary bone cancers are among the deadliest cancer types in adolescents, with osteosarcomas being the most prevalent form. Osteosarcomas are commonly treated with multi-drug neoadjuvant chemotherapy and therapy success as well as patient survival is affected by the presence of tumor suppressors. In order to assess the prognostic value of tumor-suppressive biomarkers, primary osteosarcoma tissues were analyzed prior to and after neoadjuvant chemotherapy.

Methods

We constructed a tissue microarray from high grade osteosarcoma samples, consisting of 48 chemotherapy naïve biopsies (BXs) and 47 tumor resections (RXs) after neoadjuvant chemotherapy. We performed immunohistochemical stainings of P53, P16, maspin, PTEN, BMI1 and Ki67, characterized the subcellular localization and related staining outcome with chemotherapy response and overall survival. Binary logistic regression analysis was used to analyze chemotherapy response and Kaplan-Meier-analysis as well as the Cox proportional hazards model was applied for analysis of patient survival.

Results

No significant associations between biomarker expression in BXs and patient survival or chemotherapy response were detected. In univariate analysis, positive immunohistochemistry of P53 (P = 0.008) and P16 (P16; P = 0.033) in RXs was significantly associated with poor survival prognosis. In addition, presence of P16 in RXs was associated with poor survival in multivariate regression analysis (P = 0.003; HR = 0.067) while absence of P16 was associated with good chemotherapy response (P = 0.004; OR = 74.076). Presence of PTEN on tumor RXs was significantly associated with an improved survival prognosis (P = 0.022).

Conclusions

Positive immunohistochemistry (IHC) of P16 and P53 in RXs was indicative for poor overall patient survival whereas positive IHC of PTEN was prognostic for good overall patient survival. In addition, we found that P16 might be a marker of osteosarcoma chemotherapy resistance. Therefore, our study supports the use of tumor RXs to assess the prognostic value of biomarkers.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1397-4) contains supplementary material, which is available to authorized users.

Internalization by multiple endocytic pathways and lysosomal processing impact maspin-based therapeutics

Patients with metastatic disease face high rates of mortality with a paucity of therapeutic options. Protein-based therapeutics provide advantages over traditional chemotherapy through increased specificity, decreased immune impairment, and more direct means of delivery. However, development is often hindered because of insufficient knowledge about protein processing by cells when exogenously applied. This study focuses on recombinant Maspin (rMaspin), a serine protease inhibitor (SERPINB5), which alters invasive properties when directly applied to cancer cells. Previous evidence suggests differences in the effects of rMaspin treatment when compared with endogenous reexpression, with little explanation for these discrepancies. A leading hypothesis is that exogenously applied rMaspin is subject to different regulatory and/or processing mechanisms in cancer cells when compared with endogenous expression. Therefore, a more detailed understanding of the mechanisms of internalization and subcellular trafficking of rMaspin is needed to guide future translational development. We describe the molecular trafficking of rMaspin in cytoplasmic vesicles of the endosomal/lysosomal pathway and characterize its uptake by multiple endocytic mechanisms. Time-lapse laser scanning confocal microscopy shows the uptake, in real time, of dye-labeled rMaspin in cancer cells. This study indicates that cellular processing of rMaspin plays a key role by affecting its biologic activity and highlights the need for new approaches aimed at increasing the availability of rMaspin when used to treat cancer.

IMPLICATIONS

Novel characterization of internalization and subcellular trafficking of rMaspin provides new insights for future therapeutic development.