Tissue-type plasminogen activator is a target of the tumor suppressor gene maspin

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.

The vulnerable primed cancer stem cells in disguise: demystifying the role of Maspin

Epithelial-specific Maspin is widely known as a tumor suppressor. However, while the level of maspin expression is inversely correlated with tumor grade and stage, emerging clinical evidence shows a correlation between seemingly better differentiated tumor cells that express Maspin in both the nucleus and the cytoplasm, (n + c)Maspin, with a poor prognosis of many types of cancer. Biological studies demonstrate that Maspin plays an essential role in stem cell differentiation. In light of the recently established characterization of primed stem cells (P-SCs) in development, we propose, for the first time, that cancer stem cells (CSCs) also need to undergo priming (P-CSCs) before their transition to various progeny phenotypes. We envisage major differences in the steady state kinetics between P-SCs and P-CSCs. We further propose that P-CSCs of carcinoma are both marked and regulated by (n + c)Maspin. The concept of P-CSCs helps explain the apparent dichotomous relationships of (n + c)Maspin expression with cancer diagnosis and prognosis, and is supported by the evidence from mechanistic studies. We believe that the potential utility of (n + c)Maspin as a molecular marker of P-CSCs may significantly accelerate the advancement in our understanding of the genesis of tumor phenotypic plasticity in response to changes of tumor microenvironments (TME) or drug treatments. The vulnerabilities of the cellular state of (n + c)Maspin-expressing P-CSCs are also discussed as the rationale for future development of P-CSC-targeted chemotherapeutic and immunotherapeutic strategies.

SerpinB10, a Serine Protease Inhibitor, Is Implicated in UV-Induced Cellular Response

UV-induced DNA damage response and repair are extensively studied processes, as any malfunction in these pathways contributes to the activation of tumorigenesis. Although several proteins involved in these cellular mechanisms have been described, the entire repair cascade has remained unexplored. To identify new players in UV-induced repair, we performed a microarray screen, in which we found SerpinB10 (SPB10, Bomapin) as one of the most dramatically upregulated genes following UV irradiation. Here, we demonstrated that an increased mRNA level of SPB10 is a general cellular response following UV irradiation regardless of the cell type. We showed that although SPB10 is implicated in the UV-induced cellular response, it has no indispensable function in cell survival upon UV irradiation. Nonetheless, we revealed that SPB10 might be involved in delaying the duration of DNA repair in interphase and also in S-phase cells. Additionally, we also highlighted the interaction between SPB10 and H3. Based on our results, it seems that SPB10 protein is implicated in UV-induced stress as a “quality control protein”, presumably by slowing down the repair process.

SerpinB2 is involved in cellular response upon UV irradiation

Ultraviolet light induced pyrimidine dimer is a helix distortion DNA damage type, which recruits repair complexes. However, proteins of these complexes that take part in both DNA damage recognition and repair have been well-described, the regulation of the downstream steps of nucleotide excision repair (NER) have not been clearly clarified yet. In a high-throughput screen, we identified SerpinB2 (SPB2) as one of the most dramatically upregulated gene in keratinocytes following UV irradiation. We found that both the mRNA and the protein levels of SPB2 were increased upon UV irradiation in various cell lines. Additionally, UV damage induced translocation of SPB2 from the cytoplasm to the nucleus as well as the damage induced foci formation of it. Here we show that SPB2 co-localizes with XPB involved in the NER pathway at UV-induced repair foci. Finally, we demonstrated that UV irradiation promoted the association of SPB2 with ubiquitylated proteins. In basal cell carcinoma tumour cells, we identified changes in the subcellular localization of SPB2. Based on our results, we conclude that SPB2 protein has a novel role in UV-induced NER pathway, since it regulates the removal of the repair complex from the damaged site leading to cancerous malformation.

Development of primary human pancreatic cancer organoids, matched stromal and immune cells and 3D tumor microenvironment models

Background

Patient-derived tumor models are the new standard for pre-clinical drug testing and biomarker discovery. However, the emerging technology of primary pancreatic cancer organoids has not yet been broadly implemented in research, and complex organotypic models using organoids in co-culture with stromal and immune cellular components of the tumor have yet to be established. In this study, our objective was to develop and characterize pancreatic cancer organoids and multi-cell type organotypic co-culture models to demonstrate their applicability to the study of pancreatic cancer.

Methods

We employed organoid culture methods and flow cytometric, cytologic, immunofluorescent and immunohistochemical methods to develop and characterize patient-derived pancreatic cancer organoids and multi-cell type organotypic co-culture models of the tumor microenvironment.

Results

We describe the culture and characterization of human pancreatic cancer organoids from resection, ascites and rapid autopsy sources and the derivation of adherent tumor cell monocultures and tumor-associated fibroblasts from these sources. Primary human organoids displayed tumor-like cellular morphology, tissue architecture and polarity in contrast to cell line spheroids, which formed homogenous, non-lumen forming spheres. Importantly, we demonstrate the construction of complex organotypic models of tumor, stromal and immune components of the tumor microenvironment. Activation of myofibroblast-like cancer associated fibroblasts and tumor-dependent lymphocyte infiltration were observed in these models.

Conclusions

These studies provide the first report of novel and disease-relevant 3D in-vitro models representing pancreatic tumor, stromal and immune components using primary organoid co-cultures representative of the tumor-microenvironment. These models promise to facilitate the study of tumor-stroma and tumor-immune interaction and may be valuable for the assessment of immunotherapeutics such as checkpoint inhibitors in the context of T-cell infiltration.

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.

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.

Decreased Immunoreactive Maspin Expression in Intermediate Thickness and Thick Primary Melanoma Lesions

Maspin is a member of the serpin family of protease inhibitors. It is a 42 kDa cytoplasmic protein that is reported to have tumour suppressor activity. The loss of maspin gene expression is correlated with increased invasiveness and the risk of metastases in breast cancer. We studied maspin expression in primary melanoma lesions obtained from 76 patients. Immunostaining of 5 μm sections for maspin expression was obtained using the citrate antigen retrieval method. The extent of immunostaining was scored by recording the proportion of immunoreactive cells and the intensity of immunostaining. Our results demonstrated that maspin expression was down-regulated in intermediate thickness and thick melanoma lesions compared with thin lesions. These results suggest that loss of maspin expression might play a role in melanoma progression, invasion and metastatic dissemination. Further studies are needed to clarify the clinicopathological significance of maspin expression in melanoma.

p53 regulates cytoskeleton remodeling to suppress tumor progression

Cancer cells possess unique characteristics such as invasiveness, the ability to undergo epithelial-mesenchymal transition, and an inherent stemness. Cell morphology is altered during these processes and this is highly dependent on actin cytoskeleton remodeling. Regulation of the actin cytoskeleton is, therefore, important for determination of cell fate. Mutations within the TP53 (tumor suppressor p53) gene leading to loss or gain of function (GOF) of the protein are often observed in aggressive cancer cells. Here, we highlight the roles of p53 and its GOF mutants in cancer cell invasion from the perspective of the actin cytoskeleton; in particular its reorganization and regulation by cell adhesion molecules such as integrins and cadherins. We emphasize the multiple functions of p53 in the regulation of actin cytoskeleton remodeling in response to the extracellular microenvironment, and oncogene activation. Such an approach provides a new perspective in the consideration of novel targets for anti-cancer therapy.

Loss of heterozygosity in mammary serine protease inhibitor (maspin) and p53 at chromosome 17 and 18 in oral cavity squamous cell carcinoma

BACKGROUND

The purpose of this study was to evaluate the loss of heterozygosity (LOH) in chromosomes 17p13 (p53 gene) and in 18q21 (mammary serine protease inhibitor [maspin] gene), and the expression of both genes in tissues, in patients with oral cavity squamous cell carcinoma (SCC).

METHODS

Thirty patients with oral cavity SCC have been evaluated for the presence of LOH in chromosomes 17p13 and 18q21, and the expression of p53 and maspin in tissues. Clinicopathological features and survival in these patients were also analyzed.

RESULTS

LOH in 17p13 was more frequently identified in patients with lymph node metastasis and/or high TNM classification. LOH in 18q21 was more frequently identified in high primary T classification patients. Increased expression rate of p53 and/or decreased maspin expression rate were significantly higher in oral cavity SCC than normal tissues.

CONCLUSION

LOH on chromosome 17, 18, the expression of p53, and maspin are related to the carcinogenesis of oral cavity SCC. Relationships with clinicopathological factors in oral cavity SCC were also revealed. © 2014 Wiley Periodicals, Inc. Head Neck 37: 1239-1245, 2015.

Identification of an intrinsic determinant critical for maspin subcellular localization and function

Maspin, a multifaceted tumor suppressor, belongs to the serine protease inhibitor superfamily, but only inhibits serine protease-like enzymes such as histone deacetylase 1 (HDAC1). Maspin is specifically expressed in epithelial cells and it is differentially regulated during tumor progression. A new emerging consensus suggests that a shift in maspin subcellular localization from the nucleus to the cytoplasm stratifies with poor cancer prognosis. In the current study, we employed a rational mutagenesis approach and showed that maspin reactive center loop (RCL) and its neighboring sequence are critical for maspin stability. Further, when expressed in multiple tumor cell lines, single point mutation of Aspartate(346) (D(346)) to Glutamate (E(346)), maspin(D346E), was predominantly nuclear, whereas wild type maspin (maspin(WT)) was both cytoplasmic and nuclear. Evidence from cellular fractionation followed by immunological and proteomic protein identification, combined with the evidence from fluorescent imaging of endogenous proteins, fluorescent protein fusion constructs, as well as bimolecular fluorescence complementation (BiFC) showed that the increased nuclear enrichment of maspin(D346E) was, at least in part, due to its increased affinity to HDAC1. Maspin(D346E) was also more potent than maspin(WT) as an HDAC inhibitor. Taken together, our evidence demonstrates that D(346) is a critical cis-element in maspin sequence that determines the molecular context and subcellular localization of maspin. A mechanistic model derived from our evidence suggests a new window of opportunity for the development of maspin-based biologically competent HDAC inhibitors for cancer treatment.

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.

Elevated maspin expression is associated with better overall survival in esophageal squamous cell carcinoma (ESCC)

Tumor suppressor maspin is a differentially regulated gene in the progression of many types of cancer. While the biological function of maspin in blocking tumor invasion and metastasis is consistent with the loss of maspin expression at the late stage of tumor progression, the differential expression and the biological significance of maspin in early stage of tumor progression appear to be complex and remain to be elucidated. In the current study, we examined the expression of maspin in 84 esophageal squamous cell carcinoma (ESCC) cases (stages I–III) and 55 non-tumor adjacent esophageal tissue specimens by immunohistochemical (IHC) staining. The correlation of maspin with clinicopathological parameters was analyzed. Compared to normal esophageal squamous tissue where 80% (47/55) of the cases expressed maspin at a low to moderate level, all ESCC specimens (100% (84/84)) were positive for maspin expression at a moderate to high level. ESCC with low or moderate maspin expression had significantly shorter postoperative survival rates compared to those that had high maspin expression (p<0.001). Since the correlation of maspin with ESCC histology and the correlation of maspin with ESCC prognosis seem to be at odds, we further investigated the biological function of maspin in ESCC using the established ESCC cell lines. The expression of maspin in five human esophageal squamous cancer cell lines (T12, E450, KYSE150, EC109, and KYSE510) was examined by the Western blot. ESCC cell line KYSE510 that did not express maspin and was stably transfected by maspin cDNA or an empty vector. The resulting transfected cells were characterized in vitro. Maspin expression significantly inhibited cell proliferation, motility and matrigel invasion. Taken together, our data suggest that the transient up-regulation of maspin in the early development of ESCC may be a defense mechanism against further transition towards more malignant phenotypes, ultimately slowing down ESCC tumor progression.

Prognostic value of nuclear maspin expression for adjuvant 5-fluorouracil-based chemotherapy in advanced gastric cancer

To assess the prognostic and predictive value of maspin expression for the clinical response to 5-fluorouracil (5-FU)-based chemotherapy in advanced gastric cancer (GC) patients, the expression of maspin in primary tumors from 127 patients with advanced GC was examined using immunohistochemistry. Of the 127 patients, 74 were treated with surgery alone and 53 received additional adjuvant 5-FU-based chemotherapy. Nuclear and cytoplasmic maspin expression was observed in 46.5 (59/127) and 68.5% (87/127) of patients, respectively. Nuclear maspin immunoreactivity was significantly associated with larger tumor size (p=0.036), the depth of tumor invasion (p=0.02) and lymph node metastasis (p=0.002). Cytoplasmic maspin immunoreactivity was associated with tumor cell differentiation but not with the other clinicopathological variables. Nuclear maspin immunoreactivity had a significant association with overall survival (OS). Among the nuclear maspin-expressing patients, those who were treated with 5-FU-based adjuvant chemotherapy showed significantly longer OS than those without chemotherapy (p=0.0004). In conclusion, nuclear maspin expression is associated with adverse clinical outcomes in patients with advanced GC. Patients with positive nuclear maspin expression may be more responsive to adjuvant 5-FU chemotherapy.

Maspin reprograms the gene expression profile of prostate carcinoma cells for differentiation

Maspin is an epithelial-specific tumor suppressor gene. Previous data suggest that maspin expression may redirect poorly differentiated tumor cells to better differentiated phenotypes. Further, maspin is the first and only endogenous polypeptide inhibitor of histone deacetylase 1 (HDAC1) identified thus far. In the current study, to address what central program of tumor cell redifferentiation is regulated by maspin and how tumor microenvironments further define the effects of maspin, we conducted a systematic and extensive comparison of prostate tumor cells grown in 2-dimensional culture, in 3-dimensional collagen I culture, and as in vivo bone tumors. We showed that maspin was sufficient to drive prostate tumor cells through a spectrum of temporally and spatially polarized cellular processes of redifferentiation, a reversal of epithelial-to-mesenchymal transition (EMT). Genes commonly regulated by maspin were a small subset of HDAC target genes that are closely associated with epithelial differentiation and TGFβ signaling. These results suggest that a specific endogenous HDAC inhibitor may regulate one functionally related subset of HDAC target genes, although additional maspin-induced changes of gene expression may result from tumor interaction with its specific microenvironments. Currently, EMT is recognized as a critical step in tumor progression. To this end, our current study uncovered a link between maspin and a specific mechanism of prostate epithelial differentiation that can reverse EMT.

Maspin and MCM2 immunoprofiling in salivary gland carcinomas

BACKGROUND

The pathogenesis of salivary gland carcinomas is very complex and prognostic markers are difficult to find in these carcinomas of which the different subtypes have varying malignant potential. The study was conducted to examine the cellular distribution of maspin and MCM2 in salivary gland carcinomas and their value to predict lymph node metastasis.

MATERIALS AND METHODS

Fifty three paraffin blocks of different lesions (15 muco-epidermoid carcinoma, 14 adenoid cystic carcinoma, 3 epi-myoepithelial carcinoma, 5 salivary duct carcinoma, 5 malignant pleomorphic adenoma, 6 polymorphous low grade adenocarcinoma and 5 acinic cell carcinoma) were prepared for immunohistochemical staining with maspin and MCM2 antibodies. ANOVA and Pearson correlation tests were used for the statistical analysis of the results.

RESULTS

All salivary gland carcinomas express maspin and MCM2 with variable cellular localization. There was a significant difference in the expression of each antibody between mucoepidermoid carcinoma, adenoid cystic carcinoma and polymorphous low grade adenocarcinoma. No association was found between examined markers and lymph node metastasis.

CONCLUSIONS

Salivary gland carcinomas express maspin and MCM2 with variable levels and cellular localization, consisting important markers of biological behavior in these tumors. The level of MCM2 expression can be used in the differential diagnosis of adenoid cystic carcinoma and polymorphous low grade adenocarcinoma. Further study with large sample size is recommended to assess their value in prediction of lymph node metastasis.

The emerging role of the thrombin receptor (PAR-1) in melanoma metastasis--a possible therapeutic target

Melanoma remains as the deadliest form of skin cancer with limited and inefficient treatment options available for patients with metastatic disease. Within the last decade, the thrombin receptor, Protease Activated Receptor-1, has been described as an essential gene involved in the progression of human melanoma. PAR-1 is known to activate adhesive, invasive and angiogenic factors to promote melanoma metastasis. It is overexpressed not only in metastatic melanoma cell lines but is also highly expressed in metastatic lesions as compared to primary nevi and normal skin. Recently, PAR-1 has been described to regulate the gap junction protein Connexin 43 and the tumor suppressor gene Maspin to promote the metastatic melanoma phenotype. Herein, we review the role of PAR-1 in the progression of melanoma as well as utilizing PAR-1-regulated genes as potential therapeutic targets for melanoma treatment.

Tissue-type plasminogen activator-mediated plasminogen activation and contact activation, implications in and beyond haemostasis

Due to its discovery as initiator of fibrinolysis and its well-studied activation by fibrin, tissue-type plasminogen activator (tPA) and the fibrinolytic system are generally associated with the dissolution of blood clots. However, it has been demonstrated over the years that (i) tPA can be activated by multiple proteins, (ii) plasmin has many substrates other than fibrin and (iii) tPA and plasmin have biological functions independent of fibrin and distinct from their role in blood clot lysis. We here review the data with respect to the activation of tPA by fibrin and its multiple other cofactors, in relation to tPA's role in pathophysiology, notably fibrinolysis and amyloidosis, with emphasis on Alzheimer's disease. We demonstrate a common structural element, termed cross-β structure, in misfolded proteins that is causal to tPA activation. The implications for protein misfolding diseases that are known to be associated with the deposition of amyloid and for diseases for which this has not (yet) been established are discussed.

Androgen action during prostate carcinogenesis

Androgens are critical for normal prostate development and function, as well as prostate cancer initiation and progression. Androgens function mainly by regulating target gene expression through the androgen receptor (AR). Many studies have shown that androgen-AR signaling exerts actions on key events during prostate carcinogenesis. In this review, androgen action in distinct aspects of prostate carcinogenesis, including (i) cell proliferation, (ii) cell apoptosis, and (iii) prostate cancer metastasis will be discussed.

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.

Maspin expression in renal cell carcinoma and its correlation with clinicopathologic parameters

OBJECTIVES

To investigate the relationship between maspin expression and prognostic parameters in renal cell carcinoma (RCC) with relevance to vascular endothelial growth factor (VEGF) expression and microvessel density.

METHODS

One-hundred twenty-four patients with RCC of varying histologic types who underwent radical or partial nephrectomy were studied. The mean age of the patients was 59.4 years (range, 28-84). Maspin, VEGF, and microvessel density were studied by the universal avidin-biotin complex peroxidase method. Sections of 5-μm thickness were taken from paraffin blocks for immunohistochemical study. Cytoplasmic and/or nuclear staining were scored for maspin as negative and positive for all tumor cells.

RESULTS

Cytoplasmic maspin expression was positive in 51 (41.1%) patients. Nuclear maspin expression was not seen in any of the materials. Maspin expression decreased as tumor size increased (P = .036) without any specific relation to tumor subtypes (P = .583), and decreased as the pathologic stages increased without reaching statistical significance (P = .053). There were no correlations between maspin positivity and either VEGF expression or microvessel density.

CONCLUSIONS

In RCC, maspin expression is reduced with increased tumor size. Studies with larger series may be contributory in defining the role of maspin expression in RCC. Moreover, regulation of maspin expression genes appears to have the potential to lead to new treatment approaches.

Aberrant maspin expression is involved in early carcinogenesis of gallbladder cancer

Mammary serine protease inhibitor (maspin, SERPIN-B5) is expressed in normal human mammary epithelial cells and is known to be down-regulated during cancer progression. Aberrant maspin expression has been reported in a number of cancers, including pancreatic and ovarian cancer. Recently, we identified several genes that may be tumor markers for gallbladder (GB) cancer using a DNA microarray method. There are no published data regarding maspin expression in GB cancer. The aims of this study were to determine maspin expression in normal mucosa, adenoma, dysplasia and carcinoma of GB, and to compare the pattern of maspin expression in early and advanced GB cancers. One hundred one patients with primary GB cancer who underwent resection between March 1999 and May 2008 were included. Twenty-five adenomas and 10 normal GB specimens were also included. We performed tissue microarray construction and immunohistochemical staining to evaluate maspin expression. The immunostaining results were estimated semiquantitatively by one pathologist. The positive rate of maspin expression was 59.4% (60/101) in GB cancer, whereas no maspin was expressed in adenomas and normal mucosa of GB. In case of positive maspin expression, it was gradually increased from dysplasia to carcinoma. No significant difference in the positive rate of maspin expression between early and advanced cancer was detected (49% versus 60%; P = 0.731). This result suggests that maspin expression may be involved in dysplasia-carcinoma sequence and the early steps of GB carcinogenesis.

G-helix of maspin mediates effects on cell migration and adhesion

Maspin is a member of the serine protease inhibitor (serpin) superfamily that lacks protease inhibitory ability, although displaying tumor metastasis-suppressing activity resulting from its influence on cell migration, invasion, proliferation, apoptosis, and adhesion. The molecular mechanisms of these actions of maspin are as yet undefined. Here, we sought to identify critical functional motifs by the expression of maspin with point mutations at sites potentially involved in protein-protein interactions: the G α-helix (G-helix), an internal salt bridge or the P1 position of the reactive center loop. Our findings indicate that only mutations in the G-helix attenuated inhibition of cell migration by maspin and that this structural element is also involved in the effect of maspin on cell adhesion. The action of maspin on cell migration could be mimicked by a 15-mer G-helix peptide, indicating that the G-helix is both essential and sufficient for this effect. In addition, we provide evidence that the effects of the G-helix of maspin are dependent on β1 integrins. These data reveal that the major extracellular functions associated with the tumor suppressive action of maspin likely involve interactions in which the G-helix plays a key role.

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.

Interaction of testisin with maspin and its impact on invasion and cell death resistance of cervical cancer cells

Previous studies have shown that testisin promotes malignant transformation in cancer cells. To define the mechanism of testisin-induced carcinogenesis, we performed yeast two-hybrid analysis and identified maspin, a tumor suppressor protein, as a testisin-interacting molecule. The direct interaction and cytoplasmic co-localization of testisin with maspin was confirmed by immunoprecipitation and confocal analysis, respectively. In cervical cancer cells, maspin modulated cell death and invasion; however, these effects were inhibited by testisin in parallel experiments. Of interest, the doxorubicin resistance was dramatically reduced by testisin knockdown (P=0.016). Moreover, testisin was found to be over-expressed in cervical cancer samples as compared to matched normal cervical tissues. Thus, we postulate that testisin may promote carcinogenesis by inhibiting tumor suppressor activity of maspin.

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.

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.

Mtbp haploinsufficiency in mice increases tumor metastasis

Mdm2 inhibits the function of the p53 tumor suppressor. Mdm2 is overexpressed in many tumors with wild-type p53 suggesting an alternate mechanism of loss of p53 activity in tumors. An Mdm2-binding protein (MTBP) was identified using a yeast two-hybrid screen. In tissue culture, MTBP inhibits Mdm2 self-ubiquitination, leading to stabilization of Mdm2 and increased degradation of p53. To address the role of MTBP in the regulation of the p53 pathway in vivo, we deleted the Mtbp gene in mice. Homozygous disruption of Mtbp resulted in early embryonic lethality, which was not rescued by loss of p53. Mtbp+/- mice were not tumor prone. When mice were sensitized for tumor development by p53 heterozygosity, we found that the Mtbp+/-p53+/- mice developed significantly more metastatic tumors (18.2%) as compared to p53+/- mice (2.6%). Results of in vitro migration and invasion assays support the in vivo findings. Downmodulation of Mtbp in osteosarcoma cells derived from p53+/- mice resulted in increased invasiveness, and overexpression of Mtbp in Mtbp+/-p53+/- osteosarcoma cells inhibited invasiveness. These results suggest that MTBP is a metastasis suppressor. These results advance our understanding of the cellular roles of MTBP and raise the possibility that MTBP is a novel therapeutic target for metastasis.

Maspin Binds to Urokinase-type and Tissue-type Plasminogen Activator through Exosite-Exosite Interactions

Maspin is a member of the serpin family with a reactive center loop that is incompatible with proteinase inhibition by the serpin conformational change mechanism. Despite this there are reports that maspin might regulate uPA-dependent processes in vivo. Using exogenous and endogenous fluorescence, we demonstrate here that maspin can bind uPA and tPA in both single-chain and double-chain forms, with K(d) values between 300 and 600 nM. Binding is at an exosite on maspin close to, but outside of, the reactive center loop and is therefore insensitive to mutation of Arg(340) within the reactive center loop. The binding site on tPA does not involve the proteinase active site, with the result that maspin can bind to S195A tPA that is already complexed to plasminogen activator inhibitor-1. The ability of maspin to bind these proteinases without involvement of the reactive center loop leaves the latter free to engage in additional, as yet unidentified, maspin-protein interactions that may serve to regulate the properties of the exosite-bound proteinase. This may help to reconcile apparently conflicting studies that demonstrate the importance of the reactive center loop in certain maspin functions, despite the inability of maspin to directly inhibit tPA or uPA catalytic activity in in vitro assays through engagement between its reactive center loop and the active site of the proteinase.

A role of novel serpin maspin in tumor progression: the divergence revealed through efforts to converge

Maspin, a 42 kDa protein, belongs to the serine protease inhibitor (serpin) superfamily and is more closely related to the ovalbumin-like serpin subfamily (ov-serpins). More than a decade after the discovery of the maspin gene, our pursuit of the molecular mechanisms of maspin revealed a significant divergence of maspin from other serpins. This review article summarizes recent advances in the identification of maspin-binding proteins and the potential underlying molecular mechanisms of maspin in tumor progression. Specifically, the molecular interactions of maspin with the cell surface-associated pro-urokinase-type plasminogen activator (pro-uPA) and intracellular histone deacetylase 1 (HDAC1) are highlighted. Our new evidence suggests a new paradigm that maspin acts as a serpin-like molecule to inhibit serine protease-like targets. From an evolution point of view, the uniquely important function of maspin in development and tumor progression is likely due to its ancestral sequence code, and accordingly, its novel "meta"-serpin structure. It is reasonable to hypothesize that the conservation of a serine protease-like catalytic center in many molecules requires the co-existence of endogenous antagonists. The unique inhibitory interaction of maspin with both HDAC1 and pro-uPA might not be substituted by other serpins that have evolved to acquire higher target specificities. Thus, tumor suppressive maspin offers a unique therapeutic opportunity.

Maspin Expression and Its Clinical Significance in Non-Small Cell Lung Cancer

BACKGROUND

Maspin is a member of the serpin (serine protease inhibitor) superfamily, and its exact function in the development and progression of malignant tumors remains controversial, though some experimental studies have revealed potential tumor-suppressor activities. In addition, there have been only a few clinical studies on maspin expression in malignant tumors including non-small cell lung cancer (NSCLC). The purpose of this study was to assess maspin expression and its clinical significance in NSCLC.

METHODS

A total of 210 consecutive patients with completely resected pathological (p-) stage I-IIIA NSCLC were retrospectively reviewed. Maspin expression along with intratumoral microvessel density, proliferative activity, and p53 status were evaluated immunohistochemically. The incidence of apoptotic cell death was also evaluated.

RESULTS

The incidence of strong maspin expression was significantly higher in lung squamous cell carcinoma (56/76, 73.7%; P < .001) than in other histological types. The incidence of aberrant expression of p53 was significantly higher in maspin-strong than in maspin-weak tumors (56.2% and 35.8%, respectively; P = .005). There was no difference in prognosis according to maspin status for all patients. However, for squamous cell carcinoma patients, univariate analysis showed that enhanced maspin expression was a significant factor in predicting a favorable prognosis (5-year survival rates, 70.1% for maspin-strong tumors and 41.5% for maspin-weak tumors; P = .014), which was confirmed in a multivariate analysis (hazard ratio = .475, 95% confidence interval .241-.936; P = .032).

CONCLUSIONS

Enhanced maspin expression was a significant and independent factor in predicting a favorable prognosis in lung squamous cell carcinoma.

Endogenous Inhibition of Histone Deacetylase 1 by Tumor-Suppressive Maspin

Maspin, a noninhibitory serine protease inhibitor, exerts multifaceted tumor-suppressive effects. Maspin expression is associated with better differentiated phenotypes, better cancer prognosis, and better drug sensitivity. Consistently, maspin also correlates with increased expression of Bax and p21WAF1/CIP1. Interestingly, histone deacetylase 1 (HDAC1), a major HDAC responsible for histone deacetylation, was shown to interact with maspin in a yeast two-hybrid screening. In this study, we confirmed the maspin/HDAC1 interaction in human prostate tissues, in prostate cancer cell lines, and with purified maspin. We produced several lines of evidence that support an inhibitory effect of maspin on HDAC1 through direct molecular interaction, which was detected in both the nucleus and the cytoplasm. Both endogenously expressed maspin and purified maspin inhibited HDAC1. In contrast, small interfering RNA (siRNA) silencing of maspin in PC3 cells increased HDAC activity. Accordingly, maspin-transfected DU145 cells exhibited increased expression of HDAC1 target genes Bax, cytokeratin 18 (CK18), and p21(WAF1/CIP1), whereas maspin siRNA decreased CK18 expression in PC3 cells. The maspin effect on HDAC1 correlated with an increased sensitivity to cytotoxic HDAC inhibitor M344. Interestingly, glutathione S-transferase (GST, another maspin partner) was detected in the maspin/HDAC1 complex. Furthermore, a COOH-terminally truncated maspin mutant, which bound to HDAC1 but not GST, did not increase histone acetylation. Although HDACs, especially the highly expressed HDAC1, are promising therapeutic targets in cancer intervention, our data raise a novel hypothesis that the endogenous inhibitory effect of maspin on HDAC1 is coupled with glutathione-based protein modification, and provide new leads toward future developments of specific HDAC1-targeting strategies.

Aberrant maspin expression in human endometrial cancer

Maspin, a mammary serine protease inhibitor, was originally reported as a tumor suppressor gene in breast cancer. The purpose of the present study was to examine maspin expression and evaluate its clinicopathological significance in endometrial cancer. We examined maspin expression immunohistochemically in 41 cases with endometrioid adenocarcinoma. DNA methylation status at the maspin promoter region was determined by the methylation-specific polymerase chain reaction method. Aberrant maspin expression was observed in 27 (66%) of 41 endometrioid adenocarcinomas but not in normal endometrial glands. Maspin immunoreactivity of the tumor cells varied in incidence and density among tumors. Positive staining was correlated significantly with the presence of squamous differentiation (presence vs absence = 11/11 [100%] vs 16/30 [53%], P < 0.05), and nuclear subcellular localization of maspin protein was also significantly associated with squamous differentiation (nuclear positive vs nuclear negative = 6/11 [54%] vs 2/30 [6.7%], P < 0.05). An inverse correlation between their immunoreactivity and methylation status was observed (P < 0.01). Three of the four cell lines established from endometrioid adenocarcinomas overexpressed maspin mRNA and its protein product. In a maspin-negative cell line, maspin expression was induced by treatment with 5-aza-2'-deoxycytidine, a DNA demethylating agent. There was no significant correlation between maspin expression and any clinicopathlogical data. These findings suggest that maspin induced by DNA demethylation at the promoter region may contribute to squamous differentiation of tumor cells in endometrioid adenocarcinomas.

Targeting maspin in endothelial cells to induce cell apoptosis

The diseases of cancer remain as some of the leading causes of death in the industrialised world, although there are a multitude of technologies being used in the field of medical oncology to combat these diseases and scientific research continues to make discoveries to improve patient outcomes. Some of this research has focused on the maspin gene and protein. Maspin is predicted to be a unique serpin with tumour suppressor activity. Recent studies have explored the use of maspin as a therapeutic agent against cancer. In one study, maspin was found to inhibit cancer growth and metastasis in a breast cancer mouse model through a maspin DNA-liposome therapy. A separate study showed the ability of maspin to induce apoptosis in tumour-specific endothelial cells. Taken together, these studies demonstrate the potential use of maspin as a viable anticancer therapeutic agent.

Maspin and tumor metastasis

For most cancer cell types, the acquisition of metastatic activity leads to clinically incurable disease. Improvements in surgery and radiotherapy, and the development of new chemotherapeutic agents or their use in new combinations, have, so far, only incrementally improved patient survival. Despite the obvious importance of metastasis, the process remains incompletely characterized at the molecular and biochemical levels. Tumor metastasis is a complex process and requires multiple cellular functions over time. From cellular invasion, extravasation from the primary tumor, intravasation to the secondary organs, to successful colonization, tumor cells utilize many cellular or biochemical mechanisms to complete the metastatic spread. During the process of metastasis, there are consistent changes in gene expression. Studies of genes that are reduced or silenced have yielded surprising insights into in vivo mechanisms of regulating tumor metastasis. This review describes a tumor suppressor gene, Maspin, which is often silenced in cancer cells and exhibits suppressing activity against tumor growth and metastasis. Maspin has been shown to be involved in processes that are important to both tumor growth and metastasis such as cell invasion, angiogenesis, and more recently apoptosis. Hence, many efforts have been devoted to deciphering the molecular mechanism of maspin. While some insights have come from the protease inhibitory effect of maspin, more perceptive results on how maspin may function in suppressing tumor metastasis have come from studies of gene manipulation, protein interactions and global protein profiling.

Maspin expression in carcinoma ex pleomorphic adenoma

AIMS

To investigate the presence and distribution of the protein maspin in carcinoma ex pleomorphic adenoma (CXPA).

METHODS

Maspin expression was studied by means of immunohistochemistry in 16 cases of CXPA, using the labelled polymer method.

RESULTS

According to the extent of invasion, the tumours were subdivided into: intracapsular (five cases), minimally invasive (four cases), and invasive (seven cases). Twelve patients had carcinoma with only epithelial differentiation, whereas four had a malignant myoepithelial component. Non-luminal cells in the duct-like structures of the remnant pleomorphic adenoma were strongly positive for maspin, whereas only a few luminal cells were immunopositive. A few positive cells were seen in the frequent hypocellular and hyalinised areas. Maspin was abundantly expressed, mainly in non-luminal cells, in transitional areas of CXPA with only epithelial differentiation. In frankly carcinomatous areas there was a gradual decrease in maspin expression. Almost all cells were maspin positive in CXPA with a myoepithelial component. When present, luminal cells were in general negative for maspin.

CONCLUSIONS

When only epithelial cells undergo malignant transformation, maspin expression is gradually lost. In cases with a myoepithelial component, maspin expression is high, and this might be related to the tumour suppressor activity attributed to this cell.

Protein expression profiling identifies maspin and stathmin as potential biomarkers of adenoid cystic carcinoma of the salivary glands

Adenoid cystic carcinoma (ACC) is one of the most common malignant tumors of the salivary glands. It tends to grow slowly but is associated with a poor prognosis compared to other malignant salivary gland tumors. To identify specific markers of ACC, we examined protein expression profiling in ACC xenograft and normal salivary glands (NSG) using fluorescent 2-dimensional differential in-gel electrophoresis (2-D-DIGE), an emerging technique for comparative proteomics, that improves the reproducibility and reliability of differential protein expression analysis between the samples. To identify the proteins, matrix-assisted laser desorption/ionization time-of-flight peptide mass fingerprinting was carried out. Using these strategies, we detected 4 upregulated proteins and 5 downregulated proteins in ACC xenograft. Maspin and stathmin were selected for further analyses. Western blotting and immunohistochemical staining showed a higher expression of these proteins in ACC xenograft and clinical ACC tissue compared to NSG. Furthermore, Expression of these proteins was correlated with the histologic grading of ACC (n = 10). Therefore, our data indicate that maspin and stathmin may be not only useful biomarkers of ACC but also markers of biologic behavior in this tumor.

Maspin gene expression is a significant prognostic factor in resected non-small cell lung cancer (NSCLC). Maspin in NSCLC

Maspin is a member of the serpin (serine protease inhibitor) superfamily, and some experimental studies revealed a potential tumor suppressor activity of maspin. To reveal clinical significance of maspin status in non-small cell lung cancer (NSCLC), we quantitatively evaluated maspin gene expression in lung primary tumors cut from a total of 55 resected NSCLC patients. Maspin expression in squamous cell carcinoma (Sq) was significantly higher than that in adenocarcinoma (Ad, p=0.011). Five-year overall survival rates of maspin-high and maspin-low patients were 67.7 and 41.4%, respectively, demonstrating a significant favorable prognosis of maspin-high patients (log-rank, p=0.042). A multivariate analysis confirmed that high maspin expression was an independent and significant factor to predict a favorable overall survival (p=0.031). These results suggested that maspin expression was significantly increased in Sq than in Ad, and that increased maspin expression was a significant factor to predict a favorable prognosis in resected NSCLC.

Tumor suppressive maspin and epithelial homeostasis

Maspin is a 42-kDa novel serine protease inhibitor (serpin) with multifaceted tumor suppressive activities. To date, the consensus that maspin expression predicts a better prognosis still largely holds for breast, prostate, colon, and oral squamous cancers. Interestingly, however, more detailed analyses revealed a biphasic expression pattern of maspin in early steps of tumorigenicity and re-expression of maspin in dormant cancer metastatic revertants. These data suggest a sensitivity of maspin expression to changes of epithelial microenvironments, and a role of maspin in epithelial homeostasis. Experimental evidence consistently showed that maspin suppresses tumor growth, invasion and metastasis, induces tumor redifferentiation, and enhances tumor cell sensitivity to apoptosis. Maspin protein isolated from biological sources is a monomer, which is present as a secreted, a cytoplasmic, a nuclear, as well as a cell surface-associated protein. Nuclear maspin is associated with better prognoses of cancer. It is further noted that extracellular maspin is sufficient to block tumor induced extracellular matrix degradation, tumor cell motility and invasion, whereas intracellular maspin is responsible for the increased cellular sensitivity to apoptosis. Despite these exciting developments, the mechanistic studies of maspin have proven challenging primarily due to the lack of a prototype molecular model. Although the maspin sequence has overall homologies with other members in the serpin superfamily, it does not behave like a typical serpin, that is, non-inhibitory toward active serine proteases in solution. This novel feature is in line with the X-ray crystallographic evidence. Several recent studies dedicated to finding the maspin partners support a paradigm shift. The current review is intended to summarize these recent findings and discuss a new perspective of maspin in epithelial homeostasis.

Role of squamous cell carcinoma antigen 1 expression in the invasive potential of head and neck squamous cell carcinoma

BACKGROUND

Serine proteases have important roles in tumor invasion and metastasis, and their inhibitors, serine protease inhibitors (serpins), are attractive targets for therapeutic strategies. On chromosome 18q21, there is a cluster of serpins: maspin, headpin, and squamous cell carcinoma antigen 1 (SCCA1)/SCCA2. Others and we have reported that the expression of these serpins is down regulated in head and neck squamous cell carcinoma (HNSCC) cells compared with normal squamous epithelial cells. In this study, we hypothesized that expression of SCCA1 is biologically disadvantageous to HNSCC cells.

METHODS

HNSCC cell lines were transfected with a mammalian expression vector with SCCA1 cDNA. In vitro proliferation, migration, or invasive potential (matrigel assay) of the transfectants were assayed. In addition, the in vivo growth and invasion was analyzed using the floor-of-mouth model of nude mice.

RESULTS

SCCA1 expression did not alter the in vitro growth rate of established HNSCC cells. However, SCCA1 expression significantly inhibited the in vitro invasion in matrigel assays. Furthermore, the in vivo growth and invasion in nude mice was also inhibited by SCCA1 expression.

CONCLUSIONS

Overexpression of SCCA1 in a HNSCC cell line inhibited its invasive potential. Loss of expression of the serpin SCCA1 may play a role in the malignant progression of HNSCC.

ECM degrading proteases and tissue remodelling in the mammary gland

Matrix degradation and tissue remodelling directed by matrix-degrading proteases are activated in physiological situations such as wound healing and involution of the prostate, ovaries and uterus. Recently, other activities, in addition to the cleavage of matrix proteins, have been attributed to matrix proteases including the release of growth factors from the extracellular matrix and roles in the maturation of adipocytes. This review describes extracellular proteases, including MMPs, plasminogen and cathepsins involved in the tissue remodelling processes that occur in the breast during pubertal mammary development and the mammary cycle of pregnancy, lactation and weaning. It particularly focuses on development and weaning, termed mammary gland involution, when the majority of remodelling occurs. It also brings together recent findings on the exciting new functions of matrix-degrading proteases.

Expression of maspin is associated with the intestinal type of gastric adenocarcinoma

PURPOSE

Maspin is known as a tumor suppressor gene, but its significance has been questioned in various human cancers. The aim of this study was to investigate the expression pattern of Maspin in human gastric adenocarcinomas and its possible correlation with clinicopathological findings.

MATERIALS AND METHODS

The expression of Maspin mRNA was measured by nested RT-PCR using 60 frozen adenocarcinomas of the stomach and 31 noncancerous tissues from the proximal resection margin. Immunohistochemical study for Maspin protein expression was carried out using 62 paraffin-embedded tissues, composed of both cancer and noncancerous tissues.

RESULTS

Maspin mRNA expression was detected in 80.0% (48 of 60) of the gastric adenocarcinomas, but in only 22.6% (7 of 31) of the normal gastric mucosa (p<0.001). The positive rate of Maspin protein expression was higher in the adenocarcinomas than the normal tissues (62.9% vs. 27.4%, p<0.05). In addition, the intestinal type of tumors showed significantly higher expression levels compared to the diffuse type of tumors (81.5% vs. 48.6%, p<0.05).

CONCLUSION

Our results suggest that Maspin is frequently expressed in human gastric cancers, and its expression might be associated with tumorigenesis of the intestinal type of gastric cancer.

Prognostic significance of the tumor suppressor gene maspin in non-small cell lung cancer

BACKGROUND

Maspin is a serpin protease inhibitor, which is known to suppress tumor progression in breast cancer and to be regulated by wild-type p53. This study was performed to elucidate the biologic significance of maspin expression in non-small cell lung cancer.

METHODS

To investigate whether maspin is involved in progression, clinicopathologic features, and prognosis of non-small cell lung cancer, we performed an immunohistochemical study using antimaspin antibody and identified the presence of maspin messenger ribonucleic acid in cancerous and noncancerous tissues by reverse transcription-polymerase chain reaction analysis. In addition, we evaluated p53 expression immunohistochemically on the serial sections.

RESULTS

Most adenocarcinoma and squamous cell carcinoma showed cytoplasmic staining pattern. The cytoplasmic positive rate was 77.8% (42 of 54 specimens) for the stage III group, and 36.2% (21 of 58 specimens) for the stage I group (p < 0.0001). Three-year survival rates after operation were 30.8% for the maspin-positive group and 71.1% for the maspin-negative group (p = 0.007). In multivariate analysis, immunohistochemical maspin expression in patients with non-small cell lung cancer was an independent prognostic factor for overall survival. No correlation between maspin and p53 expression in cancer cells could be observed. There was an average fourfold increase in maspin messenger ribonucleic acid levels in cancerous tissues compared with those of noncancerous tissues, and stage III cases exhibited significantly higher maspin messenger ribonucleic acid levels than stage I cases (p = 0.003).

CONCLUSIONS

The results of this study suggest that overexpression of maspin in cytoplasm may be a useful marker of tumor progression and unfavorable prognosis for overall survival in some patients with non-small cell lung cancer. Furthermore, maspin expression in cytoplasm appears to be unaffected by p53.

Maspin expression in CIN 3, microinvasive squamous cell carcinoma, and invasive squamous cell carcinoma of the uterine cervix

Maspin is a serine protease inhibitor with tumor suppression activity. It is expressed in normal breast and prostate tissue but is downregulated or absent in breast and prostate tumors. Recent reports have shown that decreased expression is associated with a greater propensity for metastasis in oral squamous cell carcinomas. We know that some high-grade cervical intraepithelial neoplasia progress to invasive carcinomas while others either persist at the same degree of atypia or regress. The pattern of maspin expression in cervical intraepithelial neoplasia-grade 3, microinvasive squamous carcinomas and overtly invasive squamous cell carcinomas of the uterine cervix was studied to determine the relationship between the extent of maspin expression and the progression of cervical intraepithelial neoplasia to squamous cell carcinoma. In total, 36 cases were evaluated: 18 cases of cervical intraepithelial neoplasia-grade 3, seven cases of microinvasive squamous cell carcinoma and 11 cases of invasive squamous cell carcinoma. A monoclonal antibody was used on paraffin-embedded tissues. Immunoreactivity was scored semiquantitatively using a scale of 0-3. The sums of the scores of the different groups were compared using the Mann-Whitney U-test. A significant decrease in maspin scores was noted between cervical intraepithelial neoplasia-grade 3 vs invasive squamous cell carcinoma (P<0.005), microinvasive squamous cell carcinoma vs invasive squamous cell carcinoma (P<0.05), and cervical intraepithelial neoplasia-grade 3 vs tumor emboli (P<0.005). Although not statistically significant, scores of cervical intraepithelial neoplasia-grade 3 associated with invasive squamous cell carcinoma were lower compared to that cervical intraepithelial neoplasia-grade 3 without invasive squamous cell carcinoma. These findings suggest that maspin likely plays a role in disease progression from in situ to invasive carcinoma. Virtual absence of maspin immunopositivity in tumor emboli indicates that maspin may also play a role in metastasis.

Maspin alters the carcinoma proteome

Maspin, a member of the serine protease inhibitor (serpin) family, is a tumor suppressor in breast and prostate cancer. To address molecular mechanisms underlying maspin's activity, we restored its expression in invasive carcinoma cells and analyzed the resulting changes by shotgun proteomics. Using a mass spectrometry-based multidimensional proteomic method, we observed changes to the expression of approximately 27% of the detectable proteome. In particular, we noted changes to the expression of proteins that regulate cytoskeletal architecture, cell death, and protein turnover. In each case, changes in protein expression were accompanied by measurable changes in tumor cell phenotype. Thus, maspin-expressing cells exhibit a more prominent actin cytoskeleton, a reduced invasive capacity, an increased rate of spontaneous apoptosis, and an altered proteasome function. These observations reveal for the first time the far reaching effects of maspin on multiple protein networks and a new hypothesis of maspin function based on the regulation of proteasome function.

Exploring alternative transcript structure in the human genome using blocks and InterPro

Understanding how alternative splicing affects gene function is an important challenge facing modern-day molecular biology. Using homology-based, protein sequence analysis methods, it should be possible to investigate how transcript diversity impacts protein function. To test this, high-quality exon-intron structures were deduced for over 8000 human genes, including over 1300 (17 percent) that produce multiple transcript variants. A data mining technique (DiffMotif) was developed to identify genes in which transcript variation coincides with changes in conserved motifs between variants. Applying this method, we found that 30 percent of the multi-variant genes in our test set exhibited a differential profile of conserved InterPro and/or BLOCKS motifs across different mRNA variants. To investigate these, a visualization tool (ProtAnnot) that displays amino acid motifs in the context of genomic sequence was developed. Using this tool, genes revealed by the DiffMotif method were analyzed, and when possible, hypotheses regarding the potential role of alternative transcript structure in modulating gene function were developed. Examples of these, including: MEOX1, a homeobox-containing protein; AIRE, involved in auto-immune disease; PLAT, tissue type plasminogen activator; and CD79b, a component of the B-cell receptor complex, are presented. These results demonstrate that amino acid motif databases like BLOCKS and InterPro are useful tools for investigating how alternative transcript structure affects gene function.