Maspin is an intracellular serpin that partitions into secretory vesicles and is present at the cell surface

Etiopathogenesis of Psoriasis: Integration of Proposed Theories

Psoriasis is a chronic inflammatory disease characterized by squamous and erythematous plaques on the skin and the involvement of the immune system. Global prevalence for psoriasis has been reported around 1-3% with a higher incidence in adults and similar proportions between men and women. The risk factors associated with psoriasis are both extrinsic and intrinsic, out of which a polygenic predisposition is a highlight out of the latter. Psoriasis etiology is not yet fully described, but several hypothesis have been proposed: 1) the autoimmunity hypothesis is based on the over-expression of antimicrobial peptides such as LL-37, the proteins ADAMTSL5, K17, and hsp27, or lipids synthesized by the PLA2G4D enzyme, all of which may serve as autoantigens to promote the differentiation of autoreactive lymphocytes T and unleash a chronic inflammatory response; 2) dysbiosis of skin microbiota hypothesis in psoriasis has gained relevance due to the observations of a loss of diversity and the participation of pathogenic bacteria such as Streptococcus spp. or Staphylococcus spp. the fungi Malassezia spp. or Candida spp. and the virus HPV, HCV, or HIV in psoriatic plaques; 3) the oxidative stress hypothesis, the most recent one, describes that the cell injury and the release of proinflammatory mediators and antimicrobial peptides that leads to activate of the Th1/Th17 axis observed in psoriasis is caused by a higher release of reactive oxygen species and the imbalance between oxidant and antioxidant mechanisms. This review aims to describe the mechanisms involved in the three hypotheses on the etiopathogeneses of psoriasis.

P176S Mutation Rewires Electrostatic Interactions That Alter Maspin Functionality

Maspin is known to regress tumors by inhibiting angiogenesis; however, its roles have been reported to be context- and sequence-dependent. Various proteins and cofactors bind to maspin, possibly explaining its conflicting roles. Moreover, polymorphic forms of maspin have also been linked to tumor regression and survival; for instance, maspin with Ser at 176 (maspin-S176) promotes tumors, while maspin with Pro at 176 (maspin-P176) has opposing roles in cancer pathogenesis. With the help of long molecular dynamics simulations, a possible link between polymorphic forms and tumor progression has been established. First, maspin is dynamically stable with either amino acid at the 176 position. Second, differential contacts have been observed among various regions; third, these contacts have significantly altered the electrostatic energetics of various residues; finally, these altered electrostatics of maspin-S176 and maspin-P176 rewire the polar contacts that abolished the allosteric control of the protein. By combining these factors, the altered electrostatics substantially affect the localization and preference of maspin-binding partners, thus culminating in a different maspin-protein(cofactor)-interaction landscape that may have been manifested in previous conflicting reports. Here, the underlying reason has been highlighted and discussed, which may be helpful for better therapeutic manipulation.

Neural EGFL like 2 expressed in myoepithelial cells and suppressed breast cancer cell migration

Breast tissue has a branching structure that contains double-layered cells, consisting primarily of luminal epithelial cells inside and myoepithelial cells outside. Ductal carcinoma in situ (DCIS) still has myoepithelial cells surrounding the cancer cells. However, myoepithelial cells disappear in invasive ductal carcinoma. In this study, we detected expression of neural EGFL like (NELL) 2 and one of its receptors, roundabout guidance receptor (ROBO) 3, in myoepithelial and luminal epithelial cells (respectively) in normal breast tissue. NELL2 also was expressed in myoepithelial cells surrounding the non-cancerous intraductal proliferative lesions and DCIS. However, the expression level and proportion of NELL2-positive cells in DCIS were lower than those in normal and non-cancerous intraductal proliferative lesions. ROBO3 expression was decreased in invasive ductal carcinoma compared to that in normal and non-cancerous intraductal proliferative lesions. An evaluation of NELL2's function in breast cancer cell lines demonstrated that full-length NELL2 suppressed cell adhesion and migration in vitro. In contrast, the N-terminal domain of NELL2 increased cell adhesion in the early phase and migration in vitro in some breast cancer cells. These results suggested that full-length NELL2 protein, when expressed in myoepithelial cells, might serve as an inhibitor of breast cancer cell migration.

Identification of a putative nuclear localization signal in the tumor suppressor maspin sheds light on its nuclear import regulation

The tumor suppressor activity of maspin (mammary serine protease inhibitor) has been associated with its nuclear localization. In this study we explore the regulation of maspin nuclear translocation. An in vitro nuclear import assay suggested that maspin can passively enter the nucleus. However, in silico analysis identified a putative maspin nuclear localization signal (NLS), which was able to mediate the nuclear translocation of a chimeric protein containing this NLS fused to five green fluorescent protein molecules in tandem (5GFP). Dominant‐negative Ran‐GTPase mutants RanQ69L or RanT24N suppressed this process. Unexpectedly, the full‐length maspin fused to 5GFP failed to enter the nucleus. As maspin's putative NLS is partially hidden in its three‐dimensional structure, we suggest that maspin nuclear transport could be conformationally regulated. Our results suggest that maspin nuclear translocation involves both passive and active mechanisms.

Potential of Protein-based Anti-metastatic Therapy with Serpins and Inter α-Trypsin Inhibitors

In this review we summarize the principles of anti-metastatic therapy with selected serpin family proteins, such as pigment epithelial-derived factor (PEDF) and maspin, as well as inter α-trypsin inhibitor (IαIs) light chains (bikunin) and heavy chains (ITIHs). Case-by-case, antimetastatic activity may be dependent or independent of the protease-inhibitory activity of the corresponding proteins. We discuss the incidence of target deregulation in different tumor entities, mechanisms of deregulation, context-dependent functional issues as well as in vitro and in vivo target validation studies with transfected tumor cells or recombinant protein as anti-metastatic agents. Finally, we comment on possible clinical evaluation of these proteins in adjuvant therapy.

A clinical-pathogenetic approach on associated anomalies and chromosomal defects supports novel candidate critical regions and genes for gastroschisis

BACKGROUND

Gastroschisis has been assumed to have a low rate of syndromic and primary malformations. We aimed to systematically review and explore the frequency and type of malformations/chromosomal syndromes and to identify significant biological/genetic roles in gastroschisis.

METHODS

Population-based, gastroschisis-associated anomalies/chromosomal defects published 1950-2018 (PubMed/MEDLINE) were independently searched by two reviewers. Associated anomalies/chromosomal defects and selected clinical characteristics were subdivided and pooled by race, system/region, isolated, and associated cases (descriptive analysis and chi-square test were performed). Critical regions/genes from representative chromosomal syndromes including an enrichment analysis using Gene Ontology Consortium/Panther Classification System databases were explored. Fisher's exact test with False Discovery Rate multiple test correction was performed.

RESULTS

Sixty-eight articles and 18525 cases as a base were identified (prevalence of 17.9 and 3% for associated anomalies/chromosomal defects, respectively). There were 3596 associated anomalies, prevailing those cardiovascular (23.3%) and digestive (20.3%). Co-occurring anomalies were associated with male, female, American Indian, Caucasian, prenatally diagnosed, chromosomal defects, and mortality (P < 0.00001). Gene clusters on 21q22.11 and 21q22.3 (KRTAP), 18q21.33 (SERPINB), 18q22.1 (CDH7, CDH19), 13q12.3 (FLT1), 13q22.1 (KLF5), 13q22.3 (EDNRB), and 13q34 (COL4A1, COL4A2, F7, F10) were significantly related to biological processes: blood pressure regulation and/or vessel integrity, angiogenesis, coagulation, cell-cell and/or cell-matrix adhesion, dermis integrity, and wound healing (P < 0.05).

CONCLUSIONS

Our findings suggest that gastroschisis may result from the interaction of several chromosomal regions in an additive manner as a pool of candidate genes were identified from critical regions supporting a role for vascular disruption, thrombosis, and mesodermal deficiency in the pathogenesis of gastroschisis.

The secretion and biological function of tumor suppressor maspin as an exosome cargo protein

Maspin is an epithelial-specific tumor suppressor shown to exert its biological effects as an intracellular, cell membrane-associated, and secreted free molecule. A recent study suggests that upon DNA-damaging g-irradiation, tumor cells can secrete maspin as an exosome-associated protein. To date, the biological significance of exosomal secretion of maspin is unknown. The current study aims at addressing whether maspin is spontaneously secreted as an exosomal protein to regulate tumor/stromal interactions. We prepared exosomes along with cell extracts and vesicle-depleted conditioned media (VDCM) from normal epithelial (CRL2221, MCF-10A and BEAS-2B) and cancer (LNCaP, PC3 and SUM149) cell lines. Atomic force microscopy and dynamic light scattering analysis revealed similar size distribution patterns and surface zeta potentials between the normal cells-derived and tumor cells-derived exosomes. Electron microscopy revealed that maspin was encapsulated by the exosomal membrane as a cargo protein. While western blotting revealed that the level of exosomal maspin from tumor cell lines was disproportionally lower relative to the levels of corresponding intracellular and VDCM maspin, as compared to that from normal cell lines, maspin knockdown in MCF-10A cells led to maspin-devoid exosomes, which exhibited significantly reduced suppressive effects on the chemotaxis activity of recipient NIH3T3 fibroblast cells. These data are the first to demonstrate the potential of maspin delivered by exosomes to block tumor-induced stromal response, and support the clinical application of exosomal maspin in cancer diagnosis and treatment.

Maspin expression and subcellular localization in invasive ductal carcinoma of the breast: Prognostic significance and relation to microvessel density

Maspin (Mammary serine protease inhibitor) is a tumor suppressor serine. Its clinical significance and role in breast carcinoma are contradictory and inconclusive. Researches demonstrated that the function of maspin differs according to its subcellular localization. This study was conducted to investigate the expression of maspin in invasive ductal carcinoma (IDC) of the breast with special emphasis on its subcellular localization and to evaluate its prognostic role in relation to clinicopathological parameters and microvessel density (MVD) of the tumor. The expression of maspin was evaluated immunohistochemically in 45 IDC cases. The positive rate of maspin expression was 73.3%. Maspin positivity was significantly related to higher tumor grade (p value = 0.041), nodal metastasis (p value = 0.044), perineural invasion (p value = 0.047), and high CD34+MVD (p value = 0.002). Nuclear maspin was detected in 36.6% whereas cytoplasmic maspin was detected in 63.4% of maspin positive cases. A significant inverse relationship was observed between nuclear maspin and high tumor grade (p value = 0.016), and nodal metastasis (p value = 0.047). These results suggest that maspin expression has a prognostic role in breast cancer. Maspin expression is related to increased angiogenesis. Subcellular localization of maspin can strongly affect cancer prognosis. Cytoplasmic maspin relates to poor prognostic parameters whereas nuclear maspin relates to good prognostic ones.

The Opportunity of Precision Medicine for Breast Cancer With Context-Sensitive Tumor Suppressor Maspin

To improve the precision of molecular diagnosis and to develop and guide targeted therapies of breast cancer, it is essential to determine the mechanisms that underlie the specific tumor phenotypes. To this end, the application of a snapshot of gene expression profile for breast cancer diagnosis and prognosis is fundamentally challenged since the tissue-based data are derived from heterogonous cell types and are not likely to reflect the dynamics of context-dependent tumor progression and drug sensitivity. The intricate network of epithelial differentiation program can be concertedly controlled by tumor suppressor maspin, a homologue of clade B serine protease inhibitors (serpin), through its multifaceted molecular interactions in multiple subcellular localizations. Unlike most other serpins that are expressed in multiple cell types, maspin is epithelial specific and has distinct roles in luminal and myoepithelial cells. Endogenously expressed maspin has been found in the nucleus and cytoplasm, and detected on the surface of cell membrane. It is also secreted free and as an exosomal cargo protein. Research in the field has led to the identification of the maspin targets and maspin-associated molecules, as well as the structural determinants of its suppressive functions. The current review discusses the possibility for maspin to serve as a cell type-specific and context-sensitive marker to improve the precision of breast cancer diagnosis and prognosis. These advancements further suggest a new window of opportunity for designing novel maspin-based chemotherapeutic agents with improved anti-cancer potency. J. Cell. Biochem. 118: 1639-1647, 2017. © 2017 Wiley Periodicals, Inc.

Identification of novel peptide motifs in the serpin maspin that affect vascular smooth muscle cell function

Maspin is a non-inhibitory member of the serpin family that affects cell behaviours related to migration and survival. We have previously shown that peptides of the isolated G α-helix (G-helix) domain of maspin show bioactivity. Migration, invasion, adhesion and proliferation of vascular smooth muscle cells (VSMC) are important processes that contribute to the build-up of atherosclerotic plaques. Here we report the use of functional assays of these behaviours to investigate whether other maspin-derived peptides impact directly on VSMC; focusing on potential anti-atherogenic properties. We designed 18 new peptides from the structural moieties of maspin above ten amino acid residues in length and considered them beside the existing G-helix peptides. Of the novel peptides screened those with the sequences of maspin strand 4 and 5 of beta sheet B (S4B and S5B) reduced VSMC migration, invasion and proliferation, as well as increasing cell adhesion. A longer peptide combining these consecutive sequences showed a potentiation of responses, and a 7-mer contained all essential elements for functionality. This is the first time that these parts of maspin have been highlighted as having key roles affecting cell function. We present evidence for a mechanism whereby S4B and S5B act through ERK1/2 and AMP-activated protein kinase (AMPK) to influence VSMC responses.

EGFR Signaling Regulates Maspin/SerpinB5 Phosphorylation and Nuclear Localization in Mammary Epithelial Cells

Maspin (SerpinB5) is a non-inhibitory serpin (serine protease inhibitor) with very diverse biological activities including regulation of cell adhesion, migration, death, control of gene expression and oxidative stress response. Initially described as a tumor and metastasis suppressor, clinical data brought controversies to the field, as some studies reported no correlation between SerpinB5 expression and prognosis value. These data underscore the importance of understanding SerpinB5 function in a normal physiological context and the molecular mechanism involved. Several SerpinB5 phosphoforms have been detected in different cell lines, but the signaling pathways involved and the biological significance of this post-translational modification in vivo remains to be explored. In this study we investigated SerpinB5 expression, subcellular localization and phosphorylation in different stages of the mouse mammary gland development and the signaling pathway involved. Here we show that SerpinB5 is first detected in late pregnancy, reaches its highest levels in lactation and remains at constant levels during post-lactational regression (involution). Using high resolution isoelectric focusing followed but immunoblot, we found at least 8 different phosphoforms of SerpinB5 during lactation, which decreases steadily at the onset of involution. In order to investigate the signaling pathway involved in SerpinB5 phosphorylation, we took advantage of the non-transformed MCF-10A model system, as we have previously observed SerpinB5 phosphorylation in these cells. We detected basal levels of SerpinB5 phosphorylation in serum- and growth factor-starved cells, which is due to amphiregulin autocrine activity on MCF-10A cells. EGF and TGF alpha, two other EGFR ligands, promote important SerpinB5 phosphorylation. Interestingly, EGF treatment is followed by SerpinB5 nuclear accumulation. Altogether, these data indicate that SerpinB5 expression and phosphorylation are developmentally regulated. In vitro analyses indicate that SerpinB5 phosphorylation is regulated by EGFR ligands, but EGF appears to be the only able to induce SerpinB5 nuclear localization.

Expression and localization of maspin in cervical cancer and its role in tumor progression and lymphangiogenesis

Objectives

Cervical cancer is the most common malignant tumor in female reproductive tract and primarily metastasizes through the lymphatic system that will affect prognosis of patients. Maspin, a member of the serine protease inhibitors (serpins) super family, has recently been indicated as a tumor suppressor in many cancers. In this study, we investigated the clinical significance of maspin expression, especially the subcellular location of maspin and its functional role in progression and lymphangiogenesis, in cervical squamous cell carcinoma.

Methods

Labelled streptavidin biotin method (LSAB) was used to determine cytoplasmic and nuclear maspin expressions, respectively, in 13 cases of normal cervix, 15 cases of cervical intraepithelial neoplasia grade 3 (CIN3), 62 cases of squamous cell carcinoma (SCC) of the uterine cervix, and 13 cases of pelvic lymphatic nodes which were all positive lymphatic nodes in our selected cancer cases. LSAB is also used to detect podoplanin which is used for counting density of lymphatic microvessels (LMVD). The clinical significance of subcellular maspin expression and the relationship between maspin expression and LMVD in cervical cancer are analyzed.

Results

Both cytoplasmic and nuclear maspin expressions in SCC were significantly weaker than those of normal cervix and CIN3. Nuclear maspin expression showed a peak in CIN3 and then dropped in SCC. Declined maspin expression was correlated with later clinical stage, increased LMVD, and lymphatic metastasis.

Conclusions

Our results suggest that subcellular location of maspin expression is a potential predictive factor in tumor progression and in patients’ prognosis of cervical cancer, and maspin plays a suppression role in lymphangiogenesis and metastasis.

Serpins, immunity and autoimmunity: old molecules, new functions

Serine protease inhibitors (serpins) are evolutionary old, structurally conserved molecules which encompass nearly all branches of life. More than 1,000 serpins were characterized to date which are subdivided into 16 subgroups (A-P) according to their common ancestry; among them, 37 are found in humans. Serpins were termed after their capability to inhibit serine proteases, but mounting evidence suggests that they may achieve a greater deal of functions, ranging from embryological growth to synaptic plasticity, development of both myeloid and lymphoid immune cells, and modulation of apoptosis. Serpins are mainly extracellular molecules, although some of them (namely, ov-serpins or clade B serpins) mostly act inside the cells, being either ubiquitously or tissue-specifically expressed. Among newly characterized serpin functions, regulation of cellular proliferation through apoptosis modulation and proteasome disturbance seems to play a major role. Accordingly, several serpins were found to be hyperexpressed in tumor cells. Indeed, apoptosis dysregulation is likely to be a cornerstone in both tumorigenesis and autoimmunity, since uncontrolled cellular viability results in tumor proliferation, while inefficient disposal of apoptotic debris may favor the rescue of autoreactive immune cells. Such a process was widely documented in systemic lupus erythematosus (SLE). Interestingly, alterations in the expression of some serpins, e.g., the ov-serpin SERPINB3, are being unraveled in patients affected with SLE and other autoimmune disorders, suggesting that a failure in serpin function might affect immune homeostasis and self-tolerance, thereby contributing to autoimmunity. Here, we provide an overview of serpin origin, function, and dysfunction, focusing on human serpins and ov-serpins, with a hub on SERPINB3.

Maspin expression and melanoma progression: a matter of sub-cellular localization

Maspin, a member of the serpin family of protease inhibitors, is involved in key processes of cancer progression. Its biological activity seems to be cancer and compartment specific, with the protein acting either as a suppressor or as a tumor promoter in different cancer types. Characterization of maspin expression and its sub-cellular localization in melanoma is missing, hence, we aim to investigate its possible association with melanoma prognostic factors and disease progression. Nuclear and cytoplasmic maspin expression were evaluated on 60 nevi, 152 primary lesions, and 106 melanoma metastases using tissue microarrays and immunohistochemistry. The association between maspin immunoreactivity and patient's clinic-pathological features was evaluated. Multivariate logistic models and survival analyses were performed for maspin expression in primary melanomas. Nuclear maspin was detected in 8% nevi, 49% primary melanomas, and 28% metastases, whereas cytoplasmic maspin in 12% nevi, 18% primary lesions, and 9% metastases. In univariate analysis, nuclear maspin expression in primary melanomas was significantly associated with melanoma prognostic factors (nodular histotype, tumor thickness, mitotic rate, and ulceration) and disease stage, whereas cytoplasmic maspin was observed at higher frequency in thin superficial spreading melanomas, without mitosis. In multivariate analysis, nuclear maspin remained significantly associated with risk of developing a tumor prone to disease progression and, accordingly, with significantly shorter disease-free and overall survival. In this study, maspin was expressed at highest frequency in primary lesions and when expressed in the nuclei, was significantly associated with poor prognostic markers, melanoma recurrence, and worse survival. The present study suggests a tumor-suppressive effect of cytoplasmic maspin and a tumor-promoting effect of nuclear maspin, which open the discussion on its potential use in cancer therapy.

Nuclear location of tumor suppressor protein maspin inhibits proliferation of breast cancer cells without affecting proliferation of normal epithelial cells

Background

Maspin, which is classified as a tumor suppressor protein, is downregulated in many types of cancer. Several studies have suggested potential anti-proliferative activity of maspin as well as sensitizing activity of maspin for therapeutic cytotoxic agents in breast cancer tissue culture and animal models. All of the experimental data gathered so far have been based on studies with maspin localized cytoplasmically, while maspin in breast cancer tumor cells may be located in the cytoplasm, nucleus or both. In this study, the effect of maspin cytoplasmic and nuclear location and expression level on breast cancer proliferation and patient survival was studied.

Methods

Tissue sections from 166 patients with invasive ductal breast cancer were stained by immunohistochemistry for maspin and Ki-67 protein. The localization and expression level of maspin were correlated with estimated patient overall survival and percent of Ki-67-positive cells. In further studies, we created constructs for transient transfection of maspin into breast cancer cells with targeted cytoplasmic and nuclear location. We analyzed the effect of maspin location in normal epithelial cell line MCF10A and three breast cancer cell lines - MCF-7, MDA-MB-231 and SKBR-3 - by immunofluorescence and proliferation assay.

Results

We observed a strong positive correlation between moderate and high nuclear maspin level and survival of patients. Moreover, a statistically significant negative relationship was observed between nuclear maspin and Ki-67 expression in patients with invasive ductal breast cancer. Spearman’s correlation analysis showed a negative correlation between level of maspin localized in nucleus and percentage of Ki-67 positive cells. No such differences were observed in cells with cytoplasmic maspin. We found a strong correlation between nuclear maspin and loss of Ki-67 protein in breast cancer cell lines, while there was no effect in normal epithelial cells from breast. The anti-proliferative effect of nuclear maspin on breast cancer cells was statistically significant in comparison to cytoplasmic maspin.

Conclusions

Our results suggest that nuclear maspin localization may be a prognostic factor in breast cancer and may have a strong therapeutic potential in gene therapy. Moreover, these data provide a new insight into the role of cytoplasmic and nuclear fractions of maspin in breast cancer.

Maspin influences response to doxorubicin by changing the tumor microenvironment organization

Altered degradation and deposition of extracellular matrix are hallmarks of tumor progression and response to therapy. From a microarray supervised analysis on a dataset of chemotherapy-treated breast carcinoma patients, maspin, a member of the serpin protease inhibitor family, has been the foremost variable identified in non-responsive versus responsive tumors. Accordingly, in a series of 52 human breast carcinomas, we detected high maspin expression in tumors that progressed under doxorubicin (DXR)-based chemotherapy. Our analysis of the role of maspin in response to chemotherapy in human MCF7 and MDAMB231 breast and SKOV3 ovarian carcinoma cells transfected to overexpress maspin and injected into mice showed that maspin overexpression led to DXR resistance through the maspin-induced collagen-enriched microenvironment and that an anti-maspin neutralizing monoclonal antibody reversed the collagen-dependent DXR resistance. Impaired diffusion and decreased DXR activity were also found in tumors derived from Matrigel-embedded cells, where abundant collagen fibers characterize the tumor matrix. Conversely, liposome-based DXR reached maspin-overexpressing tumor cells despite the abundant extracellular matrix and was more efficient in reducing tumor growth. Our results identify maspin-induced accumulation of collagen fibers as a cause of disease progression under DXR chemotherapy for breast cancer. Use of a more hydrophilic DXR formulation or of a maspin inhibitor in combination with chemotherapy holds the promise of more consistent responses to maspin-overexpressing tumors and dense-matrix tumors in general.

Serpin B5 is a CEA-interacting biomarker for colorectal cancer

Serpin B5 is a candidate tumour suppressor, but its oncogenic activity has also been reported. Its function may be affected by protein interactions. The aim of this study was to assess the relationship between serpin B5 and carcinoembryonic antigen (CEA) expression in colorectal cancer (CRC). We also analysed the clinicopathological significance of serpin B5 expression in patients with CRC. Downregulation of serpin B5 was identified in a CEA-suppressed LoVo cell line using two-dimensional gel electrophoresis (2-DE) and matrix-associated laser desorption ionisation-mass spectrometry (MALDI-MS). The specific interaction and co-localisation of serpin B5 with CEA were confirmed by co-immunoprecipitation and confocal microscopy. Western blot analysis and ELISAs revealed significant positive correlations between levels of serpin B5 and CEA in human colon cancer cell lines and in the blood of patients with CRC. Tissue expression of serpin B5 in 377 patients with CRC was significantly associated with serum CEA, histological grade, stage, lymph node metastasis, lymphatic and perineural invasion, and infiltrative border. Strong expression of serpin B5 was also associated with a reduced DFS (p = 0.001) and OS (p = 0.017). Together, these findings describe a relationship between serpin B5 and CEA expression in CRC. Strong expression of serpin B5 was associated with a worse prognosis in patients with CRC and its expression may correlate with CEA levels in CRC.

Maspin: molecular mechanisms and therapeutic implications

Maspin, a non-inhibitory member of the serine protease inhibitor superfamily, has been characterized as a tumor suppressor gene in multiple cancer types. Among the established anti-tumor effects of Maspin are the inhibition of cancer cell invasion, attachment to extracellular matrices, increased sensitivity to apoptosis, and inhibition of angiogenesis. However, while significant experimental data support the role of Maspin as a tumor suppressor, clinical data regarding the prognostic implications of Maspin expression have led to conflicting results. This highlights the need for a better understanding of the context dependencies of Maspin in normal biology and how these are perturbed in the context of cancer. In this review, we outline the regulation and roles of Maspin in normal and developmental biology while discussing novel evidence and emerging theories related to its functions in cancer. We provide insight into the immense therapeutic potential of Maspin and the challenges related to its successful clinical translation.

Role of maspin in cancer

Maspin (mammary serine protease inhibitor), is a member of the serine protease inhibitor/non-inhibitor superfamily. Its expression is down-regulated in breast, prostate, gastric and melanoma cancers but over-expressed in pancreatic, gallbladder, colorectal, and thyroid cancers suggesting that maspin may play different activities in different cell types. However, maspin expression seems to be correlated with better prognosis in prostate, bladder, lung, gastric, colorectal, head and neck, thyroid and melanoma cancer. In breast and ovarian cancer maspin significance is associated with its subcellular localization: nucleus maspin expression correlates with a good prognosis, whilst in pancreatic cancer it predicts a poor prognosis. Since tumor metastasis requires the detachment and invasion of tumor cells through the basement membrane and stroma, a selectively increased adhesion by the presence of maspin may contribute to the inhibition of tumor metastasis. Furthermore the different position of maspin inside the cell or its epigenetic modifications may explain the different behavior of the expression of maspin between tumors. The expression of maspin might be useful as a prognostic and possibly predictive factor for patients with particular types of cancer and data can guide physicians in selecting therapy. Its expression in circulating tumor cells especially in breast cancer, could be also useful in clinical practice along with other factors, such as age, comorbidities, blood examinations in order to select the best therapy to be carried out. Focusing on the malignancies in which maspin showed a positive prognostic value, therapeutic approaches studied so far aimed to re-activate a dormant tumor suppressor gene by designed transcription factors, to hit the system that inhibits the expression of maspin, to identify natural substances that can determine the activation and the expression of maspin or possible “molecules binds” to introduce maspin in cancer cell and gene therapy capable of up-regulating the maspin in an attempt to reduce primarily the risk of metastasis.

Further studies in these directions are necessary to better define the therapeutic implication of maspin.

Effect of progesterone receptor status on maspin synthesis via nitric oxide production in neutrophils in human breast cancer

BACKGROUND

Although progesterone receptor (PR) status, similarly to estrogen receptor status, is of prognostic importance in breast cancer, the involvement of the PR in breast cancer remains obscure. Studies were conducted to determine the function of the PR in neutrophils in the nitric oxide-induced synthesis of maspin, an anti-breast-cancer protein produced in nonmalignant mammary cells and in neutrophils in the circulation.

METHODS

PR status was determined by immunohistochemistry. Maspin synthesis was determined by in-vitro translation of messenger RNA and quantified by enzyme-linked immunosorbent assay. Nitric oxide was determined by the methemoglobin method.

RESULTS

It was found that PR status in neutrophils was identical with that in malignant breast tissues. A Scatchard plot for progesterone binding to normal and PR-positive (PR+) neutrophils revealed that whereas normal neutrophils had 11.5 × 10(10) PR sites/cell with K d = 47.619 nM, PR+ neutrophils had 6.6 × 10(10) PR sites/cell with K d = 47.619 nM. The progesterone negative (PR-) neutrophils failed to bind to progesterone. Incubation of normal and PR+ neutrophils with 25 nM progesterone produced 1.317 μM NO and 2.329 nM maspin; the PR+ neutrophils produced 0.72 μM NO and 1.138 nM maspin. The PR- neutrophils failed to produce any NO or maspin in the presence of progesterone. Inhibition of progesterone-induced NO synthesis led to complete inhibition of maspin synthesis in all neutrophils.

CONCLUSION

These results suggest that estrogen and progesterone complement each other in NO-induced maspin synthesis, and do not necessarily antagonize in the synthesis of the anti-breast-cancer protein.

Cathepsin E, maspin, Plk1, and survivin are promising prognostic protein markers for progression in non-muscle invasive bladder cancer

Bladder cancer is a common cancer with particularly high recurrence after transurethral resection. In this study, we investigated the prognostic value of the protein expression of cathepsin E, maspin, polo-like kinase 1 (Plk1), and survivin in patients with stage Ta and T1 urothelial carcinomas. Transcripts from the four genes encoding these proteins were previously included in gene expression signatures for outcome prediction for Ta/T1 bladder cancer. We used three different tissue microarrays with 693 non-muscle invasive urothelial carcinomas from Danish, Swedish, and Spanish patient cohorts with long-term follow-up. Protein expression was measured by immunohistochemistry, and antibody specificity was validated by Western blotting. In the Danish patient cohort, we found the expression of cathepsin E, maspin, Plk1, and survivin to be significantly associated with progression to stage T2 to T4 bladder cancer (for each marker: log-rank test; P < 0.001). Multivariate Cox regression analysis identified cathepsin E (P < 0.001), Plk1 (P = 0.021), maspin (P = 0.001), and survivin (P = 0.001) as independent prognostic markers. Furthermore, maspin, survivin, and cathepsin E expression significantly subgrouped patients already stratified by European Organization for Research and Treatment of Cancer risk scores. Finally, we successfully validated the results in tumors from 410 patients from both Sweden and Spain. We conclude that all four protein markers may have prognostic value in non-muscle invasive bladder cancer for guiding optimal treatment of patients. Additional prospective studies are needed for further validation of the clinical relevance of this marker panel.

Maspin expression in epithelial skin tumours: an immunohistochemical study

BACKGROUND

Maspin is a member of the serpin family of protease inhibitors and is thought to inhibit carcinoma invasion, metastasis, angiogenesis and induce apoptosis.

AIM

The aim of this work is to investigate maspin expression in cutaneous basal and squamous cell carcinomas by means of immunohistochemistry.

MATERIALS AND METHODS

This study was carried out on 43 patients, 25 basal cell carcinoma (BCC) and 18 squamous cell carcinoma (SCC) together with ten apparently healthy volunteers as a control group.

RESULTS

There was a significant difference between the malignant and control groups regarding maspin expression since all control cases showed maspin expression compared to 60.5% (26/43) positivity in malignant cases. Maspin positive expression tended to be of higher percentage in SCC (77.8%) compared to BCC (48%) (P = 0.06) and the strong intensity of maspin was also significantly in favour of SCC compared to BCC (P = 0.02). The staining of both the cytoplasm and nuclei was seen in 27.7% of SCC and 12% of BCC and was significantly in favour of older age group (P = 0.02) and the adenoid variant (P = 0.04) of the latter.

CONCLUSIONS

Maspin is associated with terminal squamous differentiation. Nuclear staining of maspin is seen in both BCC and SCC with a suggested tumour suppressor role in BCC.

Maspin, the molecular bridge between the plasminogen activator system and beta1 integrin that facilitates cell adhesion

Maspin is a non-inhibitory serine protease inhibitor (serpin) that influences many cellular functions including adhesion, migration, and invasion. The underlying molecular mechanisms that facilitate these actions are still being elucidated. In this study we determined the mechanism by which maspin mediates increased MCF10A cell adhesion. Utilizing competition peptides and mutation analyses, we discovered two unique regions (amino acid residues 190-202 and 260-275) involved in facilitating the increased adhesion function of maspin. In addition, we demonstrate that the urokinase-type plasminogen activator (uPA)/uPA receptor (uPAR) complex is required for the localization and adhesion function of maspin. Finally, we showed that maspin, uPAR, and β1 integrin co-immunoprecipitate, suggesting a novel maspin-uPA-uPAR-β1 integrin mega-complex that regulates mammary epithelial cell adhesion.

Identification of phosphorylation sites on extracellular corneal epithelial cell maspin

Maspin, a 42-kDa non-classical serine protease inhibitor (serpin), is expressed by epithelial cells of various tissues including the cornea. The protein localizes to the nucleus and cytosol, and is present in the extracellular space. While extracellular maspin regulates corneal stromal fibroblast adhesion and inhibits angiogenesis during wound healing in the cornea, the molecular mechanism of its extracellular functions is unclear. We hypothesized that identifying post-translational modifications of maspin, such as phosphorylation, may help decipher its mode of action. The focus of this study was on the identification of phosphorylation sites on extracellular maspin, since the extracellular form of the molecule is implicated in several functions. Multi-stage fragmentation MS was used to identify sites of phosphorylation on extracellular corneal epithelial cell maspin. A total of eight serine and threonine phosphorylation sites (Thr50, Ser97, Thr118, Thr157, Ser240, Ser298, Thr310 and Ser316) were identified on the extracellular forms of the molecule. Phosphorylation of tyrosine residues was not detected on extracellular maspin from corneal epithelial cell, in contrast to breast epithelial cells. This study provides the basis for further investigation into the functional role of phosphorylation of corneal epithelial maspin.

Metastasis suppressors in human benign prostate, intraepithelial neoplasia, and invasive cancer: their prospects as therapeutic agents

Despite advances in diagnosis and treatment of prostate cancer, development of metastases remains a major clinical challenge. Research efforts are dedicated to overcome this problem by understanding the molecular basis of the transition from benign cells to prostatic intraepithelial neoplasia (PIN), localized carcinoma, and metastatic cancer. Identification of proteins that inhibit dissemination of cancer cells will provide new perspectives to define novel therapeutics. Development of antimetastatic drugs that trigger or mimic the effect of metastasis suppressors represents new therapeutic approaches to improve patient survival. This review focuses on different biochemical and cellular functions of metastasis suppressors known to play a role in prostate carcinogenesis and progression. Ten putative metastasis suppressors implicated in prostate cancer are discussed. CD44s is decreased in both PIN and cancer; Drg-1, E-cadherin, KAI-1, RKIP, and SSeCKS show similar expression between benign epithelia and PIN, but are downregulated in invasive cancer; whereas, maspin, MKK4, Nm23 and PTEN are upregulated in PIN and downregulated in cancer. Moreover, the potential role of microRNA in prostate cancer progression, the understanding of the cellular distribution and localization of metastasis suppressors, their mechanism of action, their effect on prostate invasion and metastasis, and their potential use as therapeutics are addressed.

Investigating maspin in breast cancer progression using mouse models

Clade B serpin family of proteins regulate a variety of cellular functions including cell adhesion and motility. One key member of the clade B serpin family is maspin (SERPINB5). Maspin is classified as a type II tumor suppressor that regulates cell adhesion and invasion. It is expressed in normal mammary epithelial cells but is reduced in benign breast tumors and absent in invasive breast carcinomas. Although maspin regulates cell apoptosis, cell adhesion, migration, and invasion in breast cancer cell culture systems, mouse models are necessary to verify this in vivo. In this chapter, we review the development of transgenic and syngeneic mouse models to study the role of maspin in mammary tumorigenesis and in normal mammary development.

Possible involvement of maspin in tooth development

Maspin is a 42 kDa serine protease inhibitor that possesses tumor suppressive and anti-angiogenic activities. Despite of a huge amount of data concerning the expression pattern of maspin in various tissues and its relevance to the biological properties of a variety of human cancer cells, little is known on the maspin expression in skeletal and tooth tissues. Recently, we reported that maspin may play an important role in extracellular matrix formation in bone by enhancing the accumulation of latent TGF-β in the extracellular matrix. This study was performed to elucidate the possible role of maspin in tooth development. First, an immunohistochemical analysis for human tooth germs at the late bell stage showed the expression of maspin by active ameloblasts and odontoblasts that were forming enamel and dentin, respectively. During rat tooth development, maspin expression was observed for the first time in inner and outer enamel epithelial cells and dental papilla cells at early bell stage. The neutralizing anti-maspin antibody inhibited the proper dental tissue formation in organ cultures of mandibular first molars obtained from 21-day-old rat embryos. In addition, the proliferation of HAT-7 cells, a rat odontogenic epithelial cell line, and human dental papilla cells were suppressed in a dose-dependent manner with anti-maspin antibody. Moreover, RT-PCR analysis showed that the expression of mRNA for tooth-related genes including dentin matrix protein 1, dentin sialophosphoprotein and osteopontin in human dental papilla cells was inhibited when treated with anti-maspin antibody. These findings suggest that maspin expressed in ameloblasts and odontoblasts plays an important physiological role in tooth development through the regulation of matrix formation in dental tissues.

The diagnostic utility of maspin in the distinction between malignant mesothelioma and pulmonary adenocarcinoma

Immunohistochemistry is frequently employed to differentiate between malignant mesothelioma (MM) and pulmonary adenocarcinoma (AC) infiltrating the pleura, but there is uncertainty as to which antibodies are most useful. The present study investigated the presence of the serine protease, maspin, in epithelioid MMs and evaluated the diagnostic utility of maspin for the differential diagnosis between epithelioid MM and pulmonary AC with pleural involvement. The results showed more frequent maspin immunostaining among AC cases compared with MM cases. Maspin positivity was significantly higher among AC cases with respect to both the extent and intensity of staining. A significant difference also existed between the two tumour types with respect to the overall maspin score. Despite these findings, the sensitivity and specificity of maspin positivity to detect AC were only 59% and 73%, respectively, indicating that detection of maspin is of no value for the differential diagnosis of AC and MM.

Maspin regulates endothelial cell adhesion and migration through an integrin signaling pathway

Maspin has been identified as a potent angiogenesis inhibitor. However, the molecular mechanism responsible for its anti-angiogenic property is unclear. In this study, we examined the effect of maspin on endothelial cell (EC) adhesion and migration in a cell culture system. We found that maspin was expressed in blood vessels ECs and human umbilical vein endothelial cells (HUVECs). Maspin significantly enhanced HUVEC cell adhesion to various matrix proteins. This effect was dependent on the activation of integrin β(1), which subsequently led to distribution pattern changes of vinculin and F-actin. These results indicated that maspin affects cell adhesion and cytoskeleton reorganization through an integrin signal transduction pathway. Analysis of HUVECs following maspin treatment revealed increased integrin-linked kinase activities and phosphorylated FAK levels, consistent with increased cell adhesion. Interestingly, when HUVECs were induced to migrate by migration stimulatory factor bFGF, active Rac1 and cdc42 small GTPase levels were decreased dramatically at 30 min following maspin treatment. Using phosphorylated FAK at Tyr(397) as an indicator of focal adhesion disassembly, maspin-treated HUVECs had elevated FAK phosphorylation compared with the mock treated control. The results were a reduction in focal adhesion disassembly and the retardation in EC migration. This study uncovers a mechanism by which maspin exerts its effect on EC adhesion and migration through an integrin signal transduction pathway.

Clinicopathological correlates and prognostic significance of maspin expression in 450 patients after potentially curative resection of node-positive colonic cancer

AIMS

The tumour suppressor maspin has been investigated for its association with conventional histopathological features in colorectal cancer and for its potential as an independent predictor of survival and response to adjuvant chemotherapy. The aim of this study was to examine associations between maspin expression, other histopathology and survival in a large consecutive series of patients after potentially curative resection of node-positive colonic adenocarcinoma.

METHODS AND RESULTS

Nuclear and cytoplasmic maspin expression in both superficial and deep parts of the tumour were assessed retrospectively by tissue microarray and immunohistochemistry in specimens from 450 patients whose other histopathology had been recorded in a prospective hospital registry of large bowel cancer resections from 1971 to 2001 with a minimum follow-up of 5 years. Among 13 clinicopathological features examined, the only associations that persisted across all four maspin assessments were stronger expression in right- than in left-sided tumours (P=0.001-0.011) and stronger expression in high-grade tumours (P<0.001-0.007). There was no significant association between intensity of maspin expression and overall survival.

CONCLUSIONS

In this large and thoroughly documented series of patients with clinicopathological stage C colonic tumour, maspin expression was correlated with few other conventional histopathology variables and was not a significant prognostic factor.

Ezrin, maspin, peroxiredoxin 2, and heat shock protein 27: potential targets of a streptococcal-induced autoimmune response in psoriasis

Psoriasis is an HLA-Cw6-associated T cell-mediated autoimmune disease of the skin that is often triggered by streptococcal angina. To identify keratinocyte proteins, which may become psoriatic autoantigens as the result of an immune response against streptococci, rabbits were immunized with heat-killed Streptococcus pyogenes. Streptococcal immunization induced Ab formation against various human keratinocyte proteins. Sera from psoriasis patients reacted against several of these proteins as well. Common serologic reactivities of rabbits and patients included the proteins ezrin, maspin, peroxiredoxin 2 (PRDX2), heat shock protein (hsp)27, and keratin 6. When used for stimulation of blood lymphocytes, ezrin, maspin, PRDX2, and hsp27 induced increased T cell activation in psoriasis patients, which was particularly evident for HLA-Cw6(+) individuals. Ag-specific T cell lines generated with these proteins consisted predominantly of CD8(+) T cells and used TCR beta-chain rearrangements, which were highly homologous to those expanded within the corresponding skin lesion. Several immunodominant epitopes on the different proteins could be defined according to sequence alignments with the whole genome of S. pyogenes. Our data indicate that maspin, ezrin, PRDX2, hsp27, and potentially keratin 6 could act as autoantigens of a streptococcal-induced autoimmune response and represent targets of the exaggerated T cell response in psoriasis. Additionally, ezrin and hsp27 might constitute antigenic links between psoriasis and inflammatory bowel disease, uveitis, or arteriosclerosis, which are clinically associated.

Maspin expression in gastrointestinal stromal tumors

Background

To investigate the role of maspin expression in the progression of gastrointestinal stromal tumors, and its value as a prognostic indicator.

Methods

In the study 54 patients with GIST diagnosis were included in Uludag University of Faculty of Medicine, Department of Pathology between 1997-2007. The expression of maspin in 54 cases of gastrointestinal stromal tumor was detected by immunohistochemistry and compared with the clinicopathologic tumor parameters.

Results

The positive expression rates for maspin in the GISTs were 66,6% (36 of 54 cases). Maspin overexpression was detected in 9 of 29 high risk tumors (31%) and was significantly higher in very low/low (78.6%) and intermediate-risk tumors (63.6%) than high-risk tumors.

Conclusions

Maspin expression might be an important factor in tumor progression and patient prognosis in GIST. In the future, larger series may be studied to examine the prognostic significance of maspin in GISTs and, of course, maspin expression may be studied in different mesenchymal tumors.

Binding of extracellular maspin to beta1 integrins inhibits vascular smooth muscle cell migration

Maspin is a serpin that has multiple effects on cell behavior, including inhibition of migration. How maspin mediates these diverse effects remains unclear, as it is devoid of protease inhibitory activity. We have previously shown that maspin rapidly inhibits the migration of vascular smooth muscle cells (VSMC), suggesting the involvement of direct interactions with cell surface proteins. Here, using immunofluorescence microscopy, we demonstrate that maspin binds specifically to the surface of VSMC in the dedifferentiated, but not the differentiated, phenotype. Ligand blotting of VSMC lysates revealed the presence of several maspin-binding proteins, with a protein of 150 kDa differentially expressed between the two VSMC phenotypes. Western blotting suggested that this protein was the beta1 integrin subunit, and subsequently both alpha3beta1 and alpha5beta1, but not alphavbeta3, were shown to associate with maspin by coimmunoprecipitation. Specific binding of these integrins was also observed using maspin-affinity chromatography, using HT1080 cell lysates. Direct binding of maspin to alpha5beta1 was confirmed using a recombinant alpha5beta1-Fc fusion protein. Using conformation-dependent anti-beta1 antibodies, maspin binding to VSMC was found to lead to a decrease in the activation status of the integrin. The functional involvement of alpha5beta1 in mediating the effect of maspin was established by the inhibition of migration of CHO cells overexpressing human alpha5 integrin, but not those lacking alpha5 expression. Our observations suggest that maspin engages in specific interactions with a limited number of integrins on VSMC, leading to their inactivation, and that these interactions are responsible for the effects of maspin in the pericellular environment.

IFN-gamma regulation of vacuolar pH, cathepsin D processing and autophagy in mammary epithelial cells

In this study we examined the ability of interferon-gamma (IFN-gamma) to regulate mammary epithelial cell growth and gene expression, with particular emphasis on two genes: Maspin (a member of serine protease inhibitor superfamily), and the lysosomal aspartyl endopeptidase cathepsin D (CatD). The protein products of these genes are critically involved in regulation of multitude of biological functions in different stages of mammary tissue development and remodeling. In addition, the expression of Maspin is down-regulated in primary breast cancer and is lost in metastatic disease, while CatD is excessively produced and aberrantly secreted by breast cancer cells. We report that IFN-gamma receptors are expressed in mammary epithelial cells, and receptor engagement by IFN-gamma transduces the IFN-gamma signal via Stat-1 resulting in decreased vacuolar pH. This change in vacuolar pH alters CatD protein processing and secretion concurrent with increased Maspin secretion. In addition, IFN-gamma exerts a suppressive effect on cell growth and proliferation, and induces morphological changes in mammary epithelial cells. Our studies also reveal that breast cancer cells, which are devoid of Maspin, are refractory to IFN-gamma with respect to changes in vacuolar pH and CatD. However, Maspin transfection of breast cancer cells partially sensitizes the cells to IFN-gamma's effect, thus providing new therapeutic implications.

Haploinsufficiency of the maspin tumor suppressor gene leads to hyperplastic lesions in prostate

Maspin is a key tumor suppressor gene in prostate and breast cancers with diverse biological functions. However, how maspin regulates prostate tumor progression is not fully understood. In this study, we have used maspin heterozygous knockout mice to determine the effect of maspin haploinsufficiency on prostate development and tumor progression. We report that loss of one copy of maspin gene in Mp(+/-) heterozygous knockout mice leads to the development of prostate hyperplastic lesions, and this effect was mediated through decreased level of cyclin-dependent kinase inhibitors p21 and p27. Prostate hyperplastic lesions in Mp(+/-) mice also induced stromal reaction, which occurred in both aged prostate tissues and in neonatal prostates during early ductal morphogenesis. We showed that maspin was also expressed in prostate smooth muscle cells (PSMC), and recombinant maspin increased PSMC cell adhesion but inhibited cell proliferation. We also observed a defective interaction between epithelial cells and basement membrane in the prostate of Mp(+/-) mice, which was accompanied with a changed pattern of matrix deposition and a loss of epithelial cell polarity. Therefore, we have identified a novel property of maspin, which involves the control of the proliferation in prostate epithelial and smooth muscle cells. This is the first report that a partial loss of maspin caused an early developmental defect of the prostate and prostate hyperplastic lesions in mouse.

Maspin overexpression correlates with increased expression of vascular endothelial growth factors A, C, and D in human ovarian carcinoma

The vascular endothelial growth factor (VEGF) family, including VEGFA, VEGFC, and VEGFD, plays an essential role in the angiogenesis of both pathologic and nonpathologic conditions. Maspin belongs to the serpin superfamily and has been identified as a tumor suppressor because it inhibits motility, invasion, and angiogenesis. Few studies have compared maspin with VEGF in ovarian carcinoma. Therefore, we investigated the expression and correlation of maspin, VEGFA, VEGFC, and VEGFD with the tumorigenesis of the ovary and clinicopathologic variables. Using immunohistochemistry, we examined maspin, VEGFA, VEGFC, and VEGFD expression in 60 ovarian carcinoma tissues (35 serous papillary carcinomas, 18 endometrioid carcinomas, and 7 primary ovarian mucinous carcinomas). Staining of cells was scored as +2 if more than 50% of the cells were positive, as +1 if less than 50% of the cells were positive, and as negative if none of the cells stained positive. Overexpression of maspin, VEGFC, and VEGFD was significantly associated with high tumor grade (P<.001, P=.004, P<.001, respectively), clinical stage (P=.002, .01, and .001, respectively), the presence of ascites (P<.001, P=.03, and P=.001, respectively), and the presence of metastatic lymph nodes (P=.002, P<.001, and P<.001, respectively). Maspin was correlated with VEGFA (P=.01), VEGFC (P<.001), and VEGFD (P<.001). The VEGFA score was positively correlated with high tumor grade (P=.04), lymphovascular space invasion (LVSI) (P<.001), International Federation of Gynecology and Obstetrics (FIGO) stage (P=.009), maspin, VEGFC (P=.003), and VEGFD (P=.003), but it was not correlated with the presence of ascites and metastatic lymph nodes. Maspin, VEGFC, and VEGFD are expressed in ovarian tumors with a poor prognostic parameters, and seem to play a role in ovarian cancer angiogenesis, progression, and lymph node metastases. Our results indicate that in contrast to most other carcinomas, maspin expression is directly associated with the biological aggressiveness of ovarian carcinoma. These results may offer new insights regarding the role of maspin in ovarian cancer and might also affect the diagnosis and treatment strategies.

Maspin and p53 protein expression in gastric adenocarcinoma and its clinical applications

OBJECTIVES

To investigate the role of maspin and p53 expression in the progression of gastric cancer, and its value as a prognostic indicator.

MATERIALS AND METHODS

The expression of maspin and p53 in 152 cases of gastric cancer was detected by immunohistochemistry and compared with the clinicopathologic tumor parameters. The relationship between maspin and p53 expression was also analyzed in the gastric cancers.

RESULTS

The positive expression rates for maspin and p53 in the cancers were 71.7% (109 of 152 cases) and 56.6% (86 of 152 cases), respectively. Two patterns of immunostaining for maspin were seen in the maspin-positive gastric cancer cases: cytoplasm-only staining (67.0%, 73 of 109 cases) and staining of both cytoplasm and nucleus (33.0%, 36 of 109 cases). Maspin expression showed a negative association with histologic grade, depth of invasion, metastasis, and TNM stage (all P<0.05). p53 expression showed an association with node metastasis, and TNM stage (both P<0.05). Maspin expression was negatively correlated with p53 expression (P<0.001, r=-0.291). In univariate log-rank analysis, loss of maspin expression, histologic grade, distant metastasis, and TNM stage were associated with patient survival. Interestingly, patients with nuclear and cytoplasmic maspin expression survived longer than those with only cytoplasmic expression. However, in multivariate analysis TNM stage and regional node metastasis were the only independent prognostic factors.

CONCLUSIONS

Maspin expression might be an important factor in tumor progression and patient prognosis, but is not an independent prognostic factor. Maspin expression is inversely correlated with mutant p53 expression in gastric cancer, which suggests that maspin expression is regulated by the p53 pathway.

Maspin and Mutant p53 expression in malignant melanoma and carcinoma: use of tissue microarray

Maspin (mammary serine protease inhibitor), a member of the serpin family, has been shown to inhibit angiogenesis, tumor invasion, and metastasis. Previous studies suggest a p53-dependent regulatory pathway of maspin protein expression. Its loss correlates with progression of disease in both breast and prostate cancer. We studied the in vivo correlation of maspin expression with p53 mutation in malignant melanoma (MM) with and without use of tissue microarray (TMA). Seventy-seven MMs were immunostained on individual slides for maspin and p53 expression. Results were validated in 1 slide for each marker on a TMA system (TARP-2) with 498 tissue cores (0.6-mm diameter) from MM, other tumors, and normal tissue. The relationship between maspin and p53 in MM and carcinomas of other sites (breast, ovary, colon, lung, and prostate) was delineated using Pearson chi analysis. The inverse relationship between maspin and p53 expression predicted by hypothesized p53 regulation of maspin transcription, or any other correlation between these 2 markers, is not demonstrated in MM cases, using either classic individual slide (P=0.20) or TMA (P=0.85) methods when cutoffs for both markers are set at 10% or greater of cells staining. Even when cutoffs are altered with respect to either intensity or percentage of cells staining, no relationship is demonstrated between these markers, with either TMA or the conventional slide method. TMA immunostaining also showed no such relationship in carcinomas of the various other sites sampled-including breast and prostate, where previous studies have suggested a linkage. Despite published experimental evidence linking these 2 markers, this study failed to demonstrate correlation between maspin loss and p53 expression in MM using both individual slides and TMA, or in TMA of other carcinomas. Use of TMA is a quick, easy, and inexpensive method of immunohistochemical analysis of large numbers of cases, both to validate results obtained from individual slides and to assess specificity in a variety of neoplasms. However, heterogeneity and minimal tumor may lead to variable results.

Maspin is involved in bone matrix maturation by enhancing the accumulation of latent TGF-beta

Maspin, a serine protease inhibitor, is expressed by formative osteoblasts. The repression of maspin expression in osteoblastic cells decreased the level of latent TGF-beta in the extracellular matrix, whereas the overexpression of maspin increased latent TGF-beta. These findings suggest that maspin plays an important role in bone matrix formation, particularly in the accumulation of latent TGF-beta.

INTRODUCTION

Maspin is a serine protease inhibitor that exhibits tumor suppressive and anti-angiogenic activities. This study was performed to elucidate a possible role for maspin in bone formation.

MATERIALS AND METHODS

We performed immunohistochemical analysis of the expression of maspin during endochondral ossification. We evaluated the expression of maspin mRNA and protein in ROS 17/2.8 cells and primary rat osteoblastic cells by RT-PCR, immunocytochemistry, and Western blot analysis. We also examined the accumulation of TGF-beta in the extracellular matrix of cultured ROS 17/2.8 cells after transfection with vectors expressing either maspin or maspin antisense.

RESULTS

We observed expression of maspin by active osteoblasts in vivo. Rat osteoblastic cells also expressed maspin mRNA and protein in vitro. Moreover, the accumulation of latent TGF-beta in the extracellular matrix significantly decreased in cultures exposed to an anti-maspin antibody and when cells were transfected with a maspin antisense-expressing vector. In contrast, accumulation of latent TGF-beta in the extracellular matrix increased after transfection of cells with a vector expressing maspin.

CONCLUSIONS

These findings suggest that maspin expressed in active osteoblasts plays an important physiological role during maturation of the bone matrix, and in particular, during the process of accumulation of latent TGF-beta in the extracellular matrix.

Elucidating the function of secreted maspin: inhibiting cathepsin D-mediated matrix degradation

Cellular interaction with the extracellular milieu plays a significant role in normal biological and pathologic processes. Excessive degradation of basement membrane matrix by proteolytic enzymes is a hallmark of tumor invasion and metastasis, and aspartyl proteinase cathepsin D is implicated as a major contributor to this process. Maspin, a non-inhibitory serpin, plays an important role in mammary gland development and remodeling. Expression of Maspin is decreased in primary tumors and lost in metastatic lesions. Maspin is mostly cytoplasmic and is partially secreted; however, the fate and function of secreted Maspin has remained mostly unexplored. We hypothesized that secreted Maspin is incorporated into the matrix deposited by normal mammary epithelial cells and thus could play a critical role in cathepsin D-mediated matrix degradation and remodeling of mammary tissue. In the absence of Maspin, as is the case with most cancer cells, matrix degradation proceeds unrestricted, thus facilitating the progression to metastasis. To test this, we employed an in vitro model where gels containing both types I and IV collagen were preconditioned with normal mammary epithelial cells to allow the incorporation of secreted Maspin. This conditioned matrix was used to examine cathepsin D-mediated collagen degradation by human breast cancer cell lines. Our results indicate that secretion of Maspin and its deposition into the extracellular milieu play an important role in matrix degradation. In this capacity, Maspin could potentially regulate mammary tissue remodeling occurring under normal and pathologic conditions. In addition, these findings could have a potential effect on future therapeutic intervention strategies for breast cancer.

Loss of maspin expression contributes to a more invasive potential in malignant melanoma

Deregulation of protease expression and activity is known to play an important role in tumour progression of malignant melanoma. The serpin maspin, a tumour suppressor in breast and prostate cancer was described as an inhibitor of cell migration and inducer of cell adhesion between the basement membrane and extracellular matrix resulting in inhibition of tumour metastasis. In contrast, overexpression of maspin is correlated with poor prognosis in other cancers. However, little is known about expression, regulation and function of maspin in malignant melanoma. In this study, we found loss of maspin expression in malignant melanoma cells compared with normal human epidermal melanocytes, which was analysed by quantitative real-time PCR, Western blot analysis, immunohistochemistry and microarray. For functional studies, melanoma cell clones stably transfected with a maspin expression vector were tested for changes in proliferation, migration and invasion. Although we could not see differences in proliferation and migration, we detected strongly reduced invasive capacity in the melanoma cell clones in which maspin is re-expressed compared with control. Reduced invasive potential was also detected in three different melanoma cell lines transiently transfected with a maspin expression vector. Furthermore, exogenously added maspin alone was sufficient to reduce invasion in MelIm significantly, indicating that maspin directly inhibits invasion on the cell surface. In summary, we believe that maspin is a tumour suppressor in malignant melanoma.

Pharmacoproteomics study of cetuximab in nasopharyngeal carcinoma

Epidermal growth factor receptor (EGFR) is usually overexpressed in nasopharyngeal carcinoma (NPC). Our recent in vitro study has demonstrated that cetuximab (an antibody drug against EGFR) inhibits the growth of NPC cell lines, HK1 and HONE-1. The present study investigates the effect of cetuximab on protein expressions of NPC cell lines. NPC cells were cultured in the absence or presence of cetuximab at the IC50 concentrations (3 nM for HK1 and 0.3 nM for HONE-1) for 48 h, and total cell lysates were extracted. The cell lysates were then subjected to two-dimensional polyacrylamide gel electrophoresis (2D PAGE), and the 2D gel images were compared to discover the protein changes caused by cetuximab treatment. The common differentially expressed proteins in NPC cell lines were identified by peptide mass fingerprinting. We found that heat shock protein gp96 was down-regulated, while alpha-enolase, tumor suppressor protein maspin, and p97 valosin containing protein were up-regulated after cetuximab treatment. Reverse-transcription polymerase chain reaction (RT-PCR) analysis confirmed that the changes in protein levels of gp96, maspin, and p97 coincided with mRNA levels, indicating that these proteins were regulated at transcriptional levels. Up-regulation of gp96 has been observed in various cancers and reported to have tumor protective effects. P97 is a multifunctional AAA (ATPase associated with a variety of activities) protein and is involved in numerous cellular activities including membrane transport, protein folding, protein degradation, and cell division. Maspin has been shown to increase apoptosis, and block the growth, invasion, and metastatic properties of many tumors. The comparative tumor suppression effects of cetuximab and maspin suggest that cetuximab might exert its antitumor effects partly by up-regulation of maspin expression. The study also indicates that proteomic analysis is a promising approach to elucidate the functional mechanisms of anticancer drugs. Pharmacoproteomic study may also help to identify clinical responders for drug treatment and provide insight for new drug development.

Maspin controls mammary tumor cell migration through inhibiting Rac1 and Cdc42, but not the RhoA GTPase

Rac1 and Cdc42 are members of the Rho family of small GTPases that play essential roles in diverse cellular functions, including cell migration. The activities of these Rho family proteins are controlled by growth factor receptor activation and cell-ECM interactions. Here, we show that maspin, a well-documented tumor suppressor gene, also controls cell motility through inhibiting Rac1/Cdc42 activity. Using the GST-PAK and GST-Rho binding protein pull-down assays for GTP-bound Rac1, Cdc42, and RhoA, we showed that treatment of MDA-MB-231 tumor cells with recombinant maspin for a short time period significantly inhibited the activity of Rac1 and Cdc42, but not RhoA. The reactive site loop (RSL) within maspin protein is the functional domain involved in the inhibition. Maspin mutants with the RSL deleted or a point mutation in the RSL region lost their inhibitory activity. We further examined the ability of maspin to inhibit Rac1- and Cdc42-mediated signaling pathways and transcription factors. Treatment of MDA-MB-231 cells with maspin led to the inhibition of JNK kinase activity as assayed by immuno-kinase assays. In addition, the AP-1 transcription activity downstream of JNK kinase pathway was also reduced. Together, we have identified Rac1 and Cdc42 as the downstream targets that mediate the inhibition of mammary tumor cell migration by maspin.