Nuclear localization of maspin is essential for its inhibition of tumor growth and metastasis

Opposing Functions of Maspin Are Regulated by Its Subcellular Localization in Lung Squamous Cell Carcinoma Cells

Mammary serine protease inhibitor (maspin) is a tumor suppressor protein downregulated during carcinogenesis and cancer progression; cytoplasmic-only maspin expression is an independent, unfavorable prognostic indicator in patients with lung squamous cell carcinoma (LUSC). We hypothesized that the cytoplasmic-only localization of maspin has tumor-promoting functions in LUSC. The subcellular localization of maspin and the invasive capability of LUSC cell lines were investigated using RNA sequencing (RNA-seq), Western blotting, and siRNA transfection. Maspin mRNA and protein expression were suppressed in LK-2 and RERF-LC-AI cells. Cell invasion significantly increased in response to siRNA-mediated maspin knockdown in KNS-62 cells expressing both nuclear and cytoplasmic maspin. In LK-2 cells, both nuclear and cytoplasmic maspin were re-expressed, and cell invasion and migration were significantly decreased. In contrast, re-expressed maspin in RERF-LC-AI cells was detected only in the cytoplasm (cytMaspin), and cell invasion and migration were significantly promoted. RNA-seq and downstream analyses revealed that increased cytMaspin expression downregulated the genes associated with cell adhesion and activated PYK2 and SRC, which play important roles in cancer progression. Our study demonstrates a novel biological function of cytMaspin in enhancing the invasive capabilities of LUSC cells. Understanding cytoplasm-to-nuclear maspin translocation dysregulation may develop novel therapeutic approaches to improve the prognosis of patients with LUSC.

Prognostic value of Maspin protein level in patients with triple negative breast cancer

The search for prognostic markers in breast cancer has bumped into a typical feature of these tumors, intra and intertumoral heterogeneity. Changes in the expression profile, localization of these proteins or shedding to the surrounding stroma can be useful in the search for new markers. In this context, classification by molecular subtypes can bring perspectives for both diagnosis and screening for appropriate treatments. However, the Triple Negative (TN) subtype, which is already the one with the worst prognosis, lacks appropriate and consistent molecular markers. In this work, we analyzed 346 human breast cancer samples in tissue microarrays (TMA) from cases diagnosed with invasive breast carcinoma to assess the expression and localization pattern of Maspin and their correlation with clinical parameters. To complement our findings, we also used TCGA data to analyze the mRNA levels of these respective genes. Our data suggests that the TN subtype demonstrates a higher level of cytoplasmic Maspin compared to the other subtypes. Maspin transcript levels follow the same trend. However, TN patients with lower Maspin expression tend to have worse overall survival and free-survival metastasis rates. Finally, we used Maspin expression data to verify possible relationships with the clinicopathological information of our cohort. Our univariate analyses indicate that Maspin is related to the expression of estrogen receptor (ER) and progesterone receptor (PR). Furthermore, Maspin expression levels also showed correlation with Scarff-Bloom-Richardson (SBR) parameter, and stromal Maspin showed a relationship with lymph node involvement. Our data is not consistently robust enough to categorize Maspin as a prognostic marker. However, it does indicate a change in the expression profile within the TN subtype.

Selinexor assists vorinostat in inhibiting HDAC activity via promoting the accumulation of maspin in the nucleus of oral tongue squamous cell carcinoma cells

Oral tongue squamous cell carcinoma (OTSCC) is the most common oral cancer with a low overall survival rate, necessitating effective treatments. This study reports the anti-OTSCC effect of vorinostat and selinexor. OTSCC cell lines SCC-4 and SCC-25 were cultured to determine the effects of vorinostat and/or selinexor on cell survival, invasion, migration, and apoptosis. The transplanted tumor model of SCC-25 in nude mice was established to observe the therapeutic effects of vorinostat and/or selinexor. Western blotting was used to determine protein expressions in tumor cells. The results showed that histone deacetylase 1 (HDAC1) and exportin 1 (XPO1) were highly expressed, while nuclear maspin was expressed at a low rate in SCC-4 and SCC-25 compared to the normal tongue tissue. In vitro, both vorinostat and selinexor effectively inhibited cell viability, invasion, and migration, promoted cell apoptosis, down-regulated HDAC1, Matrix Metalloproteinase 2 (MMP2), and B cell leukemia/lymphoma 2 (Bcl-2), and up-regulated nuclear maspin and cleaved caspase 3. In vivo, both vorinostat and selinexor inhibited the growth of SCC-25-bearing tumors, down-regulated the expression of Ki67, HDAC1, MMP2, and Bcl-2, and promoted the expression of nuclear maspin and cleaved caspase 3. The combination of these two drugs exhibited synergistic effects both in vivo and in vitro. Our evidence shows that vorinostat combined with selinexor is an effective treatment for OTSCC. The mechanism may be that selinexor promotes the accumulation of maspin in the nucleus, an endogenous HDAC1 inhibitory protein to inhibit the HDAC1 activity of vorinostat and exert a synergistic anti-OTSCC effect.

Clinical Significance of Subcellular Localization of Maspin in Breast Carcinoma: An Immunohistochemical Study Using Two Different Antibodies

Background

Maspin is known to be a tumor suppressor protein: however, its prognostic value in patients with breast cancer remains controversial. The key influential factors contributing to this complexity may be the differences in antibodies used, as well as the positive criteria and sample size. To date, no study has investigated the prognostic significance of maspin expression by using two different antibodies in the same cohort. We aimed to clarify whether differences in antibodies could influence on the prognostic value of maspin in breast cancer patients.

Methods

Immunohistochemical analyses using an anti-maspin antibody (clone G167-70) were performed on 164 resected specimens of invasive carcinoma of no special type (NOS). The correlation with clinicopathological factors was compared to previous results using clone EAW24, with longer follow-up duration.

Results

The subcellular localization of maspin expression was as follows: cytoplasmic-only staining, 3 cases (1.8%), pancellular staining, 43 cases (26.2%); and no staining, 118 cases (72.0%). No nuclear-only staining was observed. There was no significant correlation between clinicopathological characteristics and the pancellualr expression of maspin. The pancellular expression group showed a significantly longer disease-free survival (DFS) than the other groups (P = 0.046). When clone EAW24 was used, the cytoplasmic-only staining group showed significantly shorter DFS than the pancellular staining group (P = 0.003).

Conclusion

Clone EAW24 may be superior to clone G167-70 in selecting breast carcinoma with an aggressive phenotype, while clone G167-70 may be superior to clone EAW24 in selecting non-aggressive breast carcinoma.

Modulating gene expression in breast cancer via DNA secondary structure and the CRISPR toolbox

Breast cancer is the most commonly diagnosed malignancy in women, and while the survival prognosis of patients with early-stage, non-metastatic disease is ∼75%, recurrence poses a significant risk and advanced and/or metastatic breast cancer is incurable. A distinctive feature of advanced breast cancer is an unstable genome and altered gene expression patterns that result in disease heterogeneity. Transcription factors represent a unique therapeutic opportunity in breast cancer, since they are known regulators of gene expression, including gene expression involved in differentiation and cell death, which are themselves often mutated or dysregulated in cancer. While transcription factors have traditionally been viewed as 'undruggable', progress has been made in the development of small-molecule therapeutics to target relevant protein-protein, protein-DNA and enzymatic active sites, with varying levels of success. However, non-traditional approaches such as epigenetic editing, transcriptional control via CRISPR/dCas9 systems, and gene regulation through non-canonical nucleic acid secondary structures represent new directions yet to be fully explored. Here, we discuss these new approaches and current limitations in light of new therapeutic opportunities for breast cancers.

PI3K-AKT, JAK2-STAT3 pathways and cell-cell contact regulate maspin subcellular localization

Background

Maspin (SERPINB5) is a potential tumor suppressor gene with pleiotropic biological activities, including regulation of cell proliferation, death, adhesion, migration and gene expression. Several studies indicate that nuclear localization is essential for maspin tumor suppression activity. We have previously shown that the EGFR activation leads to maspin nuclear localization in MCF-10A cells. The present study investigated which EGFR downstream signaling molecules are involved in maspin nuclear localization and explored a possible role of cell–cell contact in this process.

Methods

MCF-10A cells were treated with pharmacological inhibitors against EGFR downstream pathways followed by EGF treatment. Maspin subcellular localization was determined by immunofluorescence. Proteomic and interactome analyses were conducted to identify maspin-binding proteins in EGF-treated cells only. To investigate the role of cell–cell contact these cells were either treated with chelating agents or plated on different cell densities. Maspin and E-cadherin subcellular localization was determined by immunofluorescence.

Results

We found that PI3K-Akt and JAK2-STAT3, but not MAP kinase pathway, regulate EGF-induced maspin nuclear accumulation in MCF-10A cells. We observed that maspin is predominantly nuclear in sparse cell culture, but it is redistributed to the cytoplasm in confluent cells even in the presence of EGF. Proteomic and interactome results suggest a role of maspin on post-transcriptional and translation regulation, protein folding and cell–cell adhesion.

Conclusions

Maspin nuclear accumulation is determined by an interplay between EGFR (via PI3K-Akt and JAK2-STAT3 pathways) and cell–cell contact.

Role of cytoplasmic localization of maspin in promoting cell invasion in breast cancer with aggressive phenotype

Mammary serine protease inhibitor (maspin) is a tumor suppressor gene that is downregulated during carcinogenesis and breast cancer progression. While the nuclear localization of maspin is essential for tumor suppression, we previously reported that the cytoplasmic localization of maspin was significantly correlated with poor prognosis in breast cancer patients. To understand the mechanisms that underlie oncogenic role of cytoplasmic maspin, we studied its biological function in breast cancer cell lines. Subcellular localization of maspin in MDA-MB-231 breast cancer cells was mainly detected in the cytoplasm, whereas in MCF10A mammary epithelial cells, maspin was present in both cytoplasm and nucleus. In MDA-MB-231 cells, maspin overexpression promoted cell proliferation and cell invasion, whereas maspin downregulation resulted in the opposite effect. Further, we observed that SRGN protein levels were increased in MDA-MB-231 cells stably overexpressing maspin. Finally, maspin overexpression in MDA-MB-231 cells resulted in the N-cadherin and epithelial mesenchymal transition (EMT)-related transcription factors upregulation, and TGFβ signaling pathway activation. These results suggested that cytoplasmic maspin enhances the invasive and metastatic potential in breast cancer cells with aggressive phenotype by inducing EMT via SRGN/TGFβ axis. This study demonstrated a novel biological function of cytoplasmic maspin in progression of breast cancer cells with an aggressive phenotype.

The nuclear export protein XPO1 - from biology to targeted therapy

Exportin 1 (XPO1), also known as chromosome region maintenance protein 1, plays a crucial role in maintaining cellular homeostasis via the regulated export of a range of cargoes, including proteins and several classes of RNAs, from the nucleus to the cytoplasm. Dysregulation of this protein plays a pivotal role in the development of various solid and haematological malignancies. Furthermore, XPO1 is associated with resistance to several standard-of-care therapies, including chemotherapies and targeted therapies, making it an attractive target of novel cancer therapies. Over the years, a number of selective inhibitors of nuclear export have been developed. However, only selinexor has been clinically validated. The novel mechanism of action of XPO1 inhibitors implies a different toxicity profile to that of other agents and has proved challenging in certain settings. Nonetheless, data from clinical trials have led to the approval of the XPO1 inhibitor selinexor (plus dexamethasone) as a fifth-line therapy for patients with multiple myeloma and as a monotherapy for patients with relapsed and/or refractory diffuse large B cell lymphoma. In this Review, we summarize the progress and challenges in the development of nuclear export inhibitors and discuss the potential of emerging combination therapies and biomarkers of response.

Zinc oxide nanoparticles enhance expression of maspin in human breast cancer cells

Toxic and apoptotic impacts of zinc oxide nanoparticle (ZNP) on different cancer cells have been reported. Maspin (a mammary serine protease inhibitor) as a tumor suppressor gene can inhibit tumor growth and metastasis. The expression of maspin is modulated by p53, Bcl-2 family genes, and estrogen receptor α (ER-α). This study aimed to assess the ZNP effects on maspin expression in MCF-7 cells (a breast cancer cell). Experimental groups (ZNP5, ZNP10, and ZNP20) received 5, 10, and 20 μM/mL ZNP for 48 h, respectively. 17-β-estradiol (E2) was used to evaluate the role of ER-α in the anticancer impact of ZNP. Cell viability, Annexin V, migration assay, gene expression, and western blotting methods were applied to evaluate ZNP effects on the MCF-7 cells. ZNP at the concentrations of 10 and 20 μM/mL could significantly decrease the viability and migration rate, and significantly increase apoptosis percentage in the MCF-7 cells. ZNP significantly enhanced mRNA expression and protein level of maspin in MCF-7 cells in a concentration-dependent way. ZNP concentration-dependently elevated mRNA expression and protein level of p53 and Bax while reduced the expression of Bcl-2 and ER-α. E2 promoted cancer cell growth by enhancing survival and migration rates. E2 treatment reduced mRNA expression and protein level of maspin and p53, and elevated Bcl-2 expression. ZNP considerably changed these events induced by E2 in the MCF-7 cells. It is concluded that the maspin overexpression is one of the toxic mechanisms of the ZNP on the ER-α-positive breast cancer cells, and can suppress the migration of these cells.

Prognostic role of maspin expression in patients with cervical dysplasia and cervical cancer

AIM

Mammary serine protease inhibitor (maspin) acts as a tumor suppressor through the inhibition of cancer cell invasion and metastasis. Paradoxically, maspin levels are increased in some types of malignant cells. The aim of this study was to investigate the maspin expression in cervical dysplasia and cervical cancer, and to analyze its' relation with survival.

METHODS

Maspin expression was detected by immunohistochemistry using labeled streptavidin biotin method to determine cytoplasmic and nuclear maspin expressions in cervical intraepithelial neoplasia grade 1 (CIN1), cervical intraepithelial neoplasia grade 2 (CIN2), cervical intraepithelial neoplasia grade 3 (CIN3) and cervical cancer.

RESULTS

A total of 89 patients with CIN (29 cases of CIN1, 30 cases of CIN2 and 30 cases of CIN3), and 27 patients with cervical cancer were included to the study. 7.8% of the patients with CIN had maspin staining positivity. On the other hand maspin staining was positive in 20 of 27 patients (74.1%) with cervical carcinoma (P = 0.001). Of these patients 20 (100%) had cytoplasmic, and 8 (40%) had nuclear maspin staining positivity. Cytoplasmic maspin immunoreactive scores were found to be significantly higher in carcinoma group when compared to the patients with CIN1/3 (respectively; P = 0.01, P = 0.02). No difference was noted for nuclear maspin expression. Significant overall survival advantage was detected for patients with nuclear maspin staining (P = 0.03).

CONCLUSION

The current study shows that nuclear maspin expression is related with better overall survival in cervical cancer. Maspin staining can be a useful diagnostic marker to discriminate cervical intraepithelial neoplasia from cervical carcinoma.

TRIM21-SERPINB5 aids GMPS repression to protect nasopharyngeal carcinoma cells from radiation-induced apoptosis

Background

The main strategy against nasopharyngeal carcinoma (NPC) is radiotherapy. However, radioresistance mediated recurrence is a leading clinical bottleneck in NPC. Revealing the mechanism of NPC radioresistance will help improve the therapeutic effect.

Methods

In this study, the role of TRIM21 (tripartite motif–containing 21) in NPC receiving ionizing radiation was firstly examined both in vivo and in vitro. Mass spectrometry analysis was performed to identify the downstream targets of TRIM21. NPC cells with TRIM21 or SERPINB5 (serpin family B member 5) overexpression or knockout were used to determine the epistatic relationship among SERPINB5, GMPS (guanine monophosphate synthase) and TRIM21. Flow cytometry, co-immunoprecipitation, western blot and immunofluorescence were employed to strengthen the results. Finally, immunohistochemistry using 4 radiosensitive and 8 radioresistent NPC patient samples was perform to examine the association between SERPINB5 or GMPS expression and patient radio-sensitivity.

Results

As an E3 ligase, TRIM21 was highly expressed in NPC. After ionizing radiation, TRIM21 repressed TP53 expression by mediating GMPS ubiquitination and degradation. Overexpression of TRIM21 protected NPC cells from radiation mediated cell apoptosis in vitro and in vivo. Further analysis revealed that TRIM21 mediated GMPS repression was dependent on SERPINB5, and SERPINB5 served as an adaptor which prevented GMPS from entering into the nucleus and introduced TRIM21 for GMPS ubiquitination. Moreover, the in vitro and in vivo results validated the finding that SERPINB5 promoted NPC cell radioresistance, and the radioresistant patients had higher SERPINB5 expression.

Conclusions

Overall, our data showed that TRIM21–SERPINB5-mediated GMPS degradation facilitated TP53 repression, which promoted the radioresistance of NPC cells. This novel working model related to TP53 suppression provided new insight into NPC radioresistence clinically.

Gene Expression Comparison Between the Primary Tumor and its Lymph Node Metastasis in Head and Neck Squamous Cell Carcinoma: A Pilot Study

BACKGROUND/AIM

In metastatic head and neck squamous cell carcinoma (HNSCC) the metastatic tumor does not always keep the same gene expression profile as the parental tumor, which may influence the course of the disease. The aim of this study was to compare the expression of genes implicated in HNSCC carcinogenesis between the primary tumor and the corresponding lymph node metastasis.

MATERIALS AND METHODS

Eighteen HNSCC, their corresponding node metastases and non-neoplastic tissues were studied by RT-qPCR for the expression of EGFR, VEGF, claudin7, maspin, survivin and SCCA. The levels of expression were correlated with histological characteristics and patients' prognosis.

RESULTS

All genes except for survivin displayed different expression in node metastasis compared to the primary tumor. The expression of EGFR, survivin, maspin, and claudin7 in node metastasis and SSCA in the primary tumor affected the prognosis. SCCA expression is associated with the expression of claudin7 and maspin. P16-positive tumors expressed low levels of VEGF and SCCA, while keratinizing tumors over-expressed VEGF.

CONCLUSION

Differential gene expression levels in node metastases compared to the primary tumor is linked to the prognosis of HNSCC patients. The histological/immunohisto-chemical characteristics of the tumor are associated with these genes expression changes.

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.

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 roles of maspin expression in gastric cancer: a meta- and bioinformatics analysis

Maspin is a mammary serine protease inhibitor that is encoded by human SERPINB5 gene, and inhibits invasion and metastasis of cancer cells as a tumor suppressor. We performed a systematic meta- and bioinformatics analysis through multiple online databases up to Feb 10, 2017. We found down-regulated maspin expression in gastric cancer, compared with normal mucosa and dysplasia (p < 0.05). Maspin expression was negatively correlated with depth of invasion, TNM staging and dedifferentiation of gastric cancer (p < 0.05). Nuclear maspin expression was higher in intestinal- than diffuse-type carcinoma (p < 0.05). An inverse association between maspin expression and unfavorable overall survival was found in patients with gastric cancer (p < 0.005). According to bioinformatics databases, SERPINB5 mRNA expression was higher in gastric cancer than normal tissues (p < 0.05), and negatively correlated with depth of invasion, TNM staging and dedifferentiation of gastric cancer (p < 0.05). According to KM plotter, we found that a higher SERPINB5 expression was positively correlated with overall and progression-free survival rates of all cancer patients, even stratified by aggressive parameters (p < 0.05). These findings indicated that maspin expression might be employed as a potential marker to indicate gastric carcinogenesis, subsequent progression, and even prognosis.

Upregulation of maspin expression in human cervical carcinoma cells by transforming growth factor β1 through the convergence of Smad and non-Smad signaling pathways

Mammary serine protease inhibitor (maspin), encoded by the serpin family B member 5 gene, serves as a tumor suppressor through the inhibition of cancer cell invasion and metastasis. Paradoxically, maspin levels are upregulated in a number of types of malignant cells. Therefore, the regulation of maspin expression may depend on the genetic or epigenetic background and the specific microenvironment of carcinoma cells. In the present study, it was demonstrated that transforming growth factor β1 (TGF-β1) induced maspin expression at the transcript and protein levels in the human cervical carcinoma HeLa and human oral squamous carcinoma HSC4 cell lines. The inhibition of the mothers against decapentaplegic homolog (Smad)-dependent pathway by a Smad3-specific inhibitor suppressed maspin induction by TGF-β1 in HeLa cells. Inhibition of the non-Smad pathway by pretreatment with the mitogen-activated protein kinase kinase 1/2 (MEK1/2) inhibitor U0126, or the p38 mitogen-activated protein kinase (p38 MAPK) inhibitor SB202190, attenuated the effect of TGF-β1 on maspin upregulation, whereas pretreatment with pyrrolidine dithiocarbamate (a nuclear factor κB inhibitor), wortmannin (a phosphoinositide 3-kinase inhibitor) or SP600125 (a c-Jun N-terminal kinase inhibitor) did not. Notably, none of these inhibitors eliminated the TGF-β1-induced phosphorylation of Smad2. In addition, mutations at p53-binding sites in the maspin promoter suppressed TGF-β1-induced maspin expression, indicating the necessity of intact p53-binding sites on the maspin promoter. In summary, the induction of maspin expression in HeLa cells requires the convergence of TGF-β1-induced Smad and non-Smad signaling pathways, in which the latter acts via the intermediate signaling molecules MEK1/2 and p38 MAPK.

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.

Compound speckle model detects anti-angiogenic tumor response in preclinical nonlinear contrast-enhanced ultrasonography

PURPOSE

This paper proposes a method for analyzing the first-order speckle statistics of nonlinear contrast-enhanced ultrasound images from tumors.

METHODS

Contrast signal intensity is modeled as a compound distribution of exponential probability density functions with a gamma weighting function. The gamma probability weighting function serves as an approximation for log-normally distributed flow velocities in a vascular network. The model was applied to sub-harmonic bolus-injection images acquired from a mouse breast cancer xenograft model treated with murine version bevacizumab.

RESULTS

The area under curve produced using the compound statistical model could more accurately discriminate anti-VEGF-treated tumors from untreated tumors than conventional contrast-enhanced ultrasound image processing. This result was validated with gold standard histological measures of microvascular density. Fractal vessel geometry was estimated using the gamma weighting function and tested against micro-CT perfusion casting. Treated tumors had a significantly lower vascular fractal dimension than control tumors. Vascular complexity estimated using the ultrasound compound statistical model performed similarly to micro-CT fractal dimension for discriminating treated from control tumors.

CONCLUSION

The proposed technique can quantify tumor perfusion and provide an index of vascular complexity, making it a potentially useful addition for clinical detection of vascular normalization in anti-angiogenic trials.

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

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

Improved Linear Contrast-Enhanced Ultrasound Imaging via Analysis of First-Order Speckle Statistics

The linear subtraction methods commonly used for preclinical contrast-enhanced imaging are susceptible to registration errors and motion artifacts that lead to reduced contrast-to-tissue ratios. To address this limitation, a new approach to linear contrast-enhanced ultrasound (CEUS) is proposed based on the analysis of the temporal dynamics of the speckle statistics during wash-in of a bolus injection of microbubbles. In the proposed method, the speckle signal is approximated as a mixture of temporally varying random processes, representing the microbubble signal, superimposed onto spatially heterogeneous tissue backscatter in multiple subvolumes within the region of interest. A wash-in curve is constructed by plotting the effective degrees of freedom (EDoFs) of the histogram of the speckle signal as a function of time. The proposed method is, therefore, named the EDoF method. The EDoF parameter is proportional to the shape parameter of the Nakagami distribution. Images acquired at 18 MHz from a murine mammary fat pad breast cancer xenograft model were processed using gold-standard nonlinear amplitude modulation, conventional linear subtraction, and the proposed statistical method. The EDoF method shows promise for improving the robustness of linear CEUS based on reduced frame-to-frame variability compared with the conventional linear subtraction time-intensity curves. Wash-in curve parameters estimated using the EDoF method also demonstrate higher correlation to nonlinear CEUS than the conventional linear method. The conceptual basis of the statistical method implies that EDoF wash-in curves may carry information about vascular complexity that could provide valuable new imaging biomarkers for cancer research.

Quantification of cancer cell extravasation in vivo

Cancer cell 'invasiveness' is one of the main driving forces in cancer metastasis, and assays that quantify this key attribute of cancer cells are crucial in cancer metastasis research. The research goal of many laboratories is to elucidate the signaling pathways and effectors that are responsible for cancer cell invasion, but many of these experiments rely on in vitro methods that do not specifically simulate individual steps of the metastatic cascade. Cancer cell extravasation is arguably the most important example of invasion in the metastatic cascade, whereby a single cancer cell undergoes transendothelial migration, forming invasive processes known as invadopodia to mediate translocation of the tumor cell from the vessel lumen into tissue in vivo. We have developed a rapid, reproducible and economical technique to evaluate cancer cell invasiveness by quantifying in vivo rates of cancer cell extravasation in the chorioallantoic membrane (CAM) of chicken embryos. This technique enables the investigator to perform well-powered loss-of-function studies of cancer cell extravasation within 24 h, and it can be used to identify and validate drugs with potential antimetastatic effects that specifically target cancer cell extravasation. A key advantage of this technique over similar assays is that intravascular cancer cells within the capillary bed of the CAM are clearly distinct from extravasated cells, which makes cancer cell extravasation easy to detect. An intermediate level of experience in injections of the chorioallantoic membrane of avian embryos and cell culture techniques is required to carry out the protocol.

Maspin is not required for embryonic development or tumour suppression

Maspin (SERPINB5) is accepted as an important tumour suppressor lost in many cancers. Consistent with a critical role in development or differentiation maspin knockout mice die during early embryogenesis, yet clinical data conflict on the prognostic utility of maspin expression. Here to reconcile these findings we made conditional knockout mice. Surprisingly, maspin knockout embryos develop into overtly normal animals. Contrary to original reports, maspin re-expression does not inhibit tumour growth or metastasis in vivo, or influence cell migration, invasion or survival in vitro. Bioinformatic analyses reveal that maspin is not commonly under-expressed in cancer, and that perturbation of genes near maspin may in fact explain poor survival in certain patient cohorts with low maspin expression.

A role for the serpin maspin has been described in both development and cancer. In this study, the authors demonstrate that maspin knockout mice develop normally and that maspin does not function as a tumour suppressor, suggesting that another gene at the maspin locus may be responsible for this activity.

Cytoplasmic expression of maspin predicts unfavourable prognosis in patients with squamous cell carcinoma of the lung

AIMS

Maspin is known to be a tumour suppressor protein, and its prognostic significance in patients with several types of cancer, including lung squamous cell carcinoma (SCC), has been reported. However, its prognostic impact on lung SCC has been controversial. We explored the prognostic value of maspin expression with particular reference to its subcellular localization in patients with lung SCC.

METHODS AND RESULTS

Paraffin-embedded tissue samples from 101 curatively resected patients with lung SCC were analysed immunohistochemically using an antibody for maspin. Maspin positivity was defined as strong expression in only the cytoplasm and observed in 25 patients (24.6%). It correlated significantly with the presence of lymph node metastasis (P = 0.006) and higher pathological stage (P = 0.003). The patients were followed-up for 2-119 months (median: 50 months), and the maspin-positive group had shorter disease-free survival (DFS) and disease-specific survival (DSS) by log-rank test (P = 0.002, P = 0.016, respectively). Multivariate analysis revealed that the status of maspin was the only independent prognostic factor for DFS and DSS (P = 0.017, P = 0.047, respectively).

CONCLUSIONS

Cytoplasmic expression of maspin could be an independent unfavourable prognostic indicator in patients with lung SCC.

Cytoplasmic maspin expression is a predictor of poor prognosis in patients with lung adenocarcinoma measuring <3 cm

AIMS

Maspin is known to be a tumour suppressor protein, and few studies focused upon its prognostic significance in patients with small-size lung adenocarcinoma have been reported; however, its clinical significance remains controversial. We explored the prognostic value of maspin with particular reference to its subcellular localization in patients with resected lung adenocarcinoma measuring <3 cm.

METHODS AND RESULTS

Immunohistochemical analyses were performed on resected 110 specimens of lung adenocarcinoma measuring <3 cm. Maspin positivity was defined as strong expression in only the cytoplasm and was observed in 27 patients (24.5%). It correlated significantly with the presence of lymph node metastasis (P = 0.009) and micropapillary component (P < 0.001). The patients were followed-up for 6-88 months (median: 71 months), and the maspin-positive group had shorter disease-free survival (DFS) and overall survival (OS) by log-rank test (P < 0.001, P < 0.001, respectively). Using Cox's multivariate analysis, the status of maspin was an independent prognostic factor for DFS and OS (P = 0.004, P = 0.022, respectively), as well as lymph node metastasis.

CONCLUSIONS

Cytoplasmic maspin expression could be an independent poor prognostic indicator of patients with lung adenocarcinoma measuring <3 cm.

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.

Cytoplasmic maspin expression predicts poor prognosis of patients with soft tissue sarcomas

BACKGROUND

Maspin is a 42 kDa protein known to act as a tumor suppressor. Although its function has not been fully elucidated, numerous reports have investigated the prognostic impact of maspin in patients with several types of cancer. However, there have been no reports on the association between maspin expression and the prognosis of patients with soft tissue sarcomas (STS). The aim of this study was thus to explore the association of maspin expression with the prognosis of patients with STS.

METHODS

One-hundred and eight paraffin-embedded STS tissue samples were immunohistochemically analyzed using antibodies for maspin and Ki-67 antigen. The patients were followed up for 1 to 300 months (median: 33 months) and the prognostic value was evaluated by log-rank test and Cox's regression hazard model.

RESULTS

Cytoplasmic maspin expression was observed in 48.1% of specimens, and was significantly correlated with a higher FNCLCC grade (P = 0.002) and the presence of distant metastases (P = 0.001), and those with cytoplasmic maspin expression had both shorter disease-free survival (DFS) and overall survival (OS) by log-rank test (P <0.001, P = 0.001, respectively). By Cox's multivariate analysis, the presence of distant metastases was the only prognostic factor for DFS and OS.

CONCLUSIONS

This is the first report to reveal an association between maspin expression and the prognosis of patients with STS. Although further studies with a larger series of patients and a longer follow-up period will be needed, cytoplasmic maspin expression could be an indicator of unfavorable prognosis in patients with STS.

VIRTUAL SLIDES

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/13000_2014_205.

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

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

IMPLICATIONS

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

Invadopodia are required for cancer cell extravasation and are a therapeutic target for metastasis

Tumor cell extravasation is a key step during cancer metastasis, yet the precise mechanisms that regulate this dynamic process are unclear. We utilized a high-resolution time-lapse intravital imaging approach to visualize the dynamics of cancer cell extravasation in vivo. During intravascular migration, cancer cells form protrusive structures identified as invadopodia by their enrichment of MT1-MMP, cortactin, Tks4, and importantly Tks5, which localizes exclusively to invadopodia. Cancer cells extend invadopodia through the endothelium into the extravascular stroma prior to their extravasation at endothelial junctions. Genetic or pharmacological inhibition of invadopodia initiation (cortactin), maturation (Tks5), or function (Tks4) resulted in an abrogation of cancer cell extravasation and metastatic colony formation in an experimental mouse lung metastasis model. This provides direct evidence of a functional role for invadopodia during cancer cell extravasation and distant metastasis and reveals an opportunity for therapeutic intervention in this clinically important process.

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.

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.

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.

Mitochondrial proteomics of nasopharyngeal carcinoma metastasis

Background

Mitochondrial proteomic alterations of nasopharyngeal carcinoma metastasis remain unknown. Our purpose is to screen mitochondrial proteins for the elucidation of the molecular mechanisms of nasopharyngeal carcinoma metastasis and the discovery of metastasis-related biomarkers.

Methods

Mitochondria were isolated from nasopharyngeal carcinoma metastatic (5-8F) and nonmetastatic (6-10B) cell lines, respectively. After characterization of isolated mitochondria, mitochondrial differentially expressed proteins (DEPs) were quantified by two-dimensional difference in-gel electrophoresis (2D-DIGE), and identified by peptide mass fingerprint (PMF) and tandem mass spectrometry (MS/MS). A functional enrichment analysis and a protein-protein interaction sub-network analysis for DEPs were carried out with bioinformatics. Furthermore, siRNAs transient transfections were used to suppress expressions of some up-regulated DEPs in metastatic cells (5-8F), followed by Transwell Migration assay.

Results

Sixteen mitochondrial DEPs including PRDX3 and SOD2 were identified. Those 5-8F cells with suppression of PRDX3 showed an increased mobility potential. The functional enrichment analyses of DEPs discovered five significant biological processes including cellular response to reactive oxygen species, hydrogen peroxide metabolic process, regulation of mitochondrial membrane potential, cell redox homeostasis and oxidation reduction, and five significant molecular functions including oxidoreductase activity, caspase inhibitor activity, peroxiredoxin activity, porin activity and antioxidant activity. A protein-protein interaction sub-network of DEPs was generated with literature data. Ten mitochondrial DEPs including PRDX3, PRDX6, SOD2, ECH1, SERPINB5, COX5A, PDIA5, EIF5A, IDH3B, and PSMC4 were rationalized in the tumor-stroma co-evolution model that mitochondrial oxidative stress directly contributes to tumor metastasis.

Conclusions

Sixteen mitochondrial DEPs were identified with mass spectrometry and ten of them were rationalized in the tumor-stroma co-evolution model. Those 5-8F cells with suppression of PRDX3 showed an increased mobility potential. These data suggest that those mitochondrial DEPs are potential biomarkers for NPC metastasis, and their dysregulation would play important roles in mitochondria oxidative stress-mediated NPC metastatic process.

Targeting serous epithelial ovarian cancer with designer zinc finger transcription factors

Ovarian cancer is the leading cause of death among gynecological malignancies. It is detected at late stages when the disease is spread through the abdominal cavity in a condition known as peritoneal carcinomatosis. Thus, there is an urgent need to develop novel therapeutic interventions to target advanced stages of ovarian cancer. Mammary serine protease inhibitor (Maspin) represents an important metastasis suppressor initially identified in breast cancer. Herein we have generated a sequence-specific zinc finger artificial transcription factor (ATF) to up-regulate the Maspin promoter in aggressive ovarian cancer cell lines and to interrogate the therapeutic potential of Maspin in ovarian cancer. We found that although Maspin was expressed in some primary ovarian tumors, the promoter was epigenetically silenced in cell lines derived from ascites. Transduction of the ATF in MOVCAR 5009 cells derived from ascitic cultures of a TgMISIIR-TAg mouse model of ovarian cancer resulted in tumor cell growth inhibition, impaired cell invasion, and severe disruption of actin cytoskeleton. Systemic delivery of lipid-protamine-RNA nanoparticles encapsulating a chemically modified ATF mRNA resulted in inhibition of ovarian cancer cell growth in nude mice accompanied with Maspin re-expression in the treated tumors. Gene expression microarrays of ATF-transduced cells revealed an exceptional specificity for the Maspin promoter. These analyses identified novel targets co-regulated with Maspin in human short-term cultures derived from ascites, such as TSPAN12, that could mediate the anti-metastatic phenotype of the ATF. Our work outlined the first targeted, non-viral delivery of ATFs into tumors with potential clinical applications for metastatic ovarian cancers.

Loss of pannexin 1 attenuates melanoma progression by reversion to a melanocytic phenotype

Pannexin 1 (Panx1) is a channel-forming glycoprotein expressed in different cell types of mammalian skin. We examined the role of Panx1 in melanoma tumorigenesis and metastasis since qPCR and Western blots revealed that mouse melanocytes exhibited low levels of Panx1 while increased Panx1 expression was correlated with tumor cell aggressiveness in the isogenic melanoma cell lines (B16-F0, -F10, and -BL6). Panx1 shRNA knockdown (Panx1-KD) generated stable BL6 cell lines, with reduced dye uptake, that showed a marked increase in melanocyte-like cell characteristics including higher melanin production, decreased cell migration and enhanced formation of cellular projections. Western blotting and proteomic analyses using 2D-gel/mass spectroscopy identified vimentin and β-catenin as two of the markers of malignant melanoma that were down-regulated in Panx1-KD cells. Xenograft Panx1-KD cells grown within the chorioallantoic membrane of avian embryos developed tumors that were significantly smaller than controls. Mouse-Alu qPCR of the excised avian embryonic organs revealed that tumor metastasis to the liver was significantly reduced upon Panx1 knockdown. These data suggest that while Panx1 is present in skin melanocytes it is up-regulated during melanoma tumor progression, and tumorigenesis can be inhibited by the knockdown of Panx1 raising the possibility that Panx1 may be a viable target for the treatment of melanoma.

Tyrosine phosphorylation plays a role in increasing maspin protein levels and its cytoplasmic accumulation

Maspin is a tumor suppressor with many biological activities, multiple ligands and different subcellular localizations. Its underlying molecular mechanism remains elusive. We hypothesized that phosphorylation might regulate maspin localization and function. Using two-dimensional gel electrophoresis with different focusing power followed by Western blot we identified four different maspin forms with the same molecular weight (42 kDa), but different isoelectric points. Three of these forms were sensitive to acidic phosphatase treatment, suggesting that they are phosphorylated. Sodium peroxidovanadate treatment, a protein-tyrosine phosphatase inhibitor, resulted in a rapid increase in maspin protein levels and cytoplasmic accumulation. These data show that there are three different maspin tyrosine phosphoforms. Inhibition of tyrosine phosphatases increased maspin protein levels and leads to its cytoplasmic accumulation.

An emerging role for the nuclear localization of maspin in the suppression of tumor progression and metastasis

Maspin, a member of the serpin family of serine protease inhibitors, was originally identified as a tumor suppressor that is expressed in normal mammary epithelial cells but is reduced or absent in breast carcinomas. Early enthusiasm for maspin as a biomarker for disease progression has been tempered by clinical data that associates maspin with favourable outcomes in some studies and poor prognosis in others. Here, we review all of the published clinical studies for maspin in breast and ovarian cancers and propose that the apparent discordance between clinical reports is a consequence of differential cellular distribution of maspin. Indeed, it was thought that an extracellular pool of maspin possessed tumor suppressor activity, acting by inhibiting migration and increasing cell adhesion. Recent evidence from our group and others indicates, however, that the nuclear localization of maspin in cancer cells is necessary for its tumor suppressor activity. We provide additional data here to demonstrate that nuclear-localized maspin binds to chromatin and is required to effectively prevent cells from metastasizing. Our knowledge of other serpins that localize to the nucleus should help to inform future studies of nuclear maspin. Elucidation of the molecular mechanisms regulating the localization and activities of maspin should pave the way for the development of improved diagnostics and therapies for cancer.

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.

Suppression of breast tumor growth and metastasis by an engineered transcription factor

Maspin is a tumor and metastasis suppressor playing an essential role as gatekeeper of tumor progression. It is highly expressed in epithelial cells but is silenced in the onset of metastatic disease by epigenetic mechanisms. Reprogramming of Maspin epigenetic silencing offers a therapeutic potential to lock metastatic progression. Herein we have investigated the ability of the Artificial Transcription Factor 126 (ATF-126) designed to upregulate the Maspin promoter to inhibit tumor progression in pre-established breast tumors in immunodeficient mice. ATF-126 was transduced in the aggressive, mesenchymal-like and triple negative breast cancer line, MDA-MB-231. Induction of ATF expression in vivo by Doxycycline resulted in 50% reduction in tumor growth and totally abolished tumor cell colonization. Genome-wide transcriptional profiles of ATF-induced cells revealed a gene signature that was found over-represented in estrogen receptor positive (ER+) "Normal-like" intrinsic subtype of breast cancer and in poorly aggressive, ER+ luminal A breast cancer cell lines. The comparison transcriptional profiles of ATF-126 and Maspin cDNA defined an overlapping 19-gene signature, comprising novel targets downstream the Maspin signaling cascade. Our data suggest that Maspin up-regulates downstream tumor and metastasis suppressor genes that are silenced in breast cancers, and are normally expressed in the neural system, including CARNS1, SLC8A2 and DACT3. In addition, ATF-126 and Maspin cDNA induction led to the re-activation of tumor suppressive miRNAs also expressed in neural cells, such as miR-1 and miR-34, and to the down-regulation of potential oncogenic miRNAs, such as miR-10b, miR-124, and miR-363. As expected from its over-representation in ER+ tumors, the ATF-126-gene signature predicted favorable prognosis for breast cancer patients. Our results describe for the first time an ATF able to reduce tumor growth and metastatic colonization by epigenetic reactivation of a dormant, normal-like, and more differentiated gene program.