Maspin Expression in Prostate Tumor Cells Averts Stemness and Stratifies Drug Sensitivity

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.

N6-methyladenine-mediated aberrant activation of the lncRNA SOX2OT-GLI1 loop promotes non-small-cell lung cancer stemness

Despite the advent of precision medicine and immunotherapy, mortality due to lung cancer remains high. The sonic hedgehog (SHH) cascade and its key terminal factor, glioma-associated oncogene homolog 1 (GLI1), play a pivotal role in the stemness and drug resistance of lung cancer. Here, we investigated the molecular mechanism of non-canonical aberrant GLI1 upregulation. The SHH cascade was upregulated in stem spheres and chemo-resistant lung cancer cells and was accountable for drug resistance against multiple chemotherapy regimens. GLI1 and the long non-coding RNA SOX2OT were positively regulated, and the GLI1-SOX2OT loop mediated the proliferation of parental and stem-like lung cancer cells. Further mechanistic investigation revealed that SOX2OT facilitated METTL3/14/IGF2BP2-mediated m6A modification and stabilization of the GLI1 mRNA. Additionally, SOX2OT upregulated METTL3/14/IGF2BP2 by sponging miR-186-5p. Functional analysis corroborated that GLI1 acted as a downstream target of METTL3/14/IGF2BP2, and GLI1 silencing could block the oncogenicity of lung cancer stem-like cells. Pharmacological inhibition of the loop remarkably inhibited the oncogenesis of lung cancer cells in vivo. Compared with paired adjacent normal tissues, lung cancer specimens exhibited consistently upregulated GLI1/SOX2OT/METTL3/14/IGF2BP2. The m6A-modified GLI1-SOX2OT loop may serve as a potential therapeutic target and prognostic predictor for lung cancer therapy and diagnosis in the clinic.

Integrating the tumor-suppressive activity of Maspin with p53 in retuning the epithelial homeostasis: A working hypothesis and applicable prospects

Epithelial malignant transformation and tumorous development were believed to be closely associated with the loss of its microenvironment integrity and homeostasis. The tumor-suppressive molecules Maspin and p53 were demonstrated to play a crucial role in body epithelial and immune homeostasis. Downregulation of Maspin and mutation of p53 were frequently associated with malignant transformation and poor prognosis in various human cancers. In this review, we focused on summarizing the progress of the molecular network of Maspin in studying epithelial tumorous development and its response to clinic treatment and try to clarify the underlying antitumor mechanism. Notably, Maspin expression was reported to be transcriptionally activated by p53, and the transcriptional activity of p53 was demonstrated to be enhanced by its acetylation through inhibition of HDAC1. As an endogenous inhibitor of HDAC1, Maspin possibly potentiates the transcriptional activity of p53 by acetylating the p53 protein. Hereby, it could form a “self-propelling” antitumor mechanism. Thus, we summarized that, upon stimulation of cellular stress and by integrating with p53, the aroused Maspin played the epigenetic surveillant role to prevent the epithelial digressional process and retune the epithelial homeostasis, which is involved in activating host immune surveillance, regulating the inflammatory factors, and fine-tuning its associated cell signaling pathways. Consequentially, in a normal physiological condition, activation of the above “self-propelling” antitumor mechanism of Maspin and p53 could reduce cellular stress (e.g., chronic infection/inflammation, oxidative stress, transformation) effectively and achieve cancer prevention. Meanwhile, designing a strategy of mimicking Maspin’s epigenetic regulation activity with integrating p53 tumor-suppressive activity could enhance the chemotherapy efficacy theoretically in a pathological condition of cancer.

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.

Bacterial Lipopolysaccharide Augmented Malignant Transformation and Promoted the Stemness in Prostate Cancer Epithelial Cells

Purpose

To study bacterial lipopolysaccharide (LPS)-induced cancer stem-like transformation and to investigate the inhibitory effect of Trichostatin A (TSA) on the malignant transformation through targeting p-Stat3 signaling.

Methods

2D, 3D, and serum-free suspension culture system were used to study LPS-induced malignant transformation in series malignant grade of prostate cancer (PCa) epithelial cells. Flow cytometry assay and RT-PCR were utilized to evaluate the CD44⁺CD133⁺ stem cell population, the expression of inflammatory cytokines and series tumor stemness biomarkers. Meanwhile, Western blot was used to analyze the alteration of cell signaling associated-molecules by treatment with TSA, an original antifungal antibiotic and a panel inhibitor of histone deacetylase.

Results

Our study found that LPS promoted the migration, invasion and stem-like tumoroshpere forming in multiple PCa cell lines including DU145, PC3, 22RV1, LNCaP. LPS also enriched CD44⁺CD133⁺ stem cell population and increased the expression of series tumor stemness biomarkers (e.g., CD44, CD133, SOX-2, α-intergrin, Nestin, etc.). TSA was found to prevent tumor cell migration, invasion and tumorosphere forming in DU145 and PC3 cells with increasing tumor suppressive Maspin and reducing both phosphorylation of Stat3 (p-Stat3) and pro-oncogene c-Myc expression in LPS-treated DU145 cells. Furthermore, blocking Stat3 signaling pathway by treatment with TSA and/or small molecule compound Stattic of an p-Stat3 inhibitor effectively abrogated LPS-induced tumorosphere forming with decrease of IL-6, IL-8 and stemness biomarkers CD44, SOX-2 expression.

Conclusion

Our data demonstrated that the inflammatory agent of bacterial LPS augmented malignant transformation and promoted the cancerous stemness in PCa epithelial cells. TSA could prevent, at least in part, the LPS-induced malignant transformation by targeting p-Stat3/c-Myc signaling pathway and reducing inflammatory IL-6, IL-8. In addition, the assay of LPS-induced tumorosphere forming could serve as a simple and an easy handling method for targeting cancer stem cells drug screening in vitro in clinical practice.

Salinomycin as a potent anticancer stem cell agent: State of the art and future directions

Cancer stem cells (CSCs) are a small subpopulation of cells within a tumor that can both self‐renew and differentiate into other cell types forming the heterogeneous tumor bulk. Since CSCs are involved in all aspects of cancer development, including tumor initiation, cell proliferation, metastatic dissemination, therapy resistance, and recurrence, they have emerged as attractive targets for cancer treatment and management. Salinomycin, a widely used antibiotic in poultry farming, was identified by the Weinberg group as a potent anti‐CSC agent in 2009. As a polyether ionophore, salinomycin exerts broad‐spectrum activities, including the important anti‐CSC function. Studies on the mechanism of action of salinomycin against cancer have been continuously and rapidly published since then. Thus, it is imperative for us to update its literature of recent research findings in this area. We here summarize the notable work reported on salinomycin's anticancer activities, intracellular binding target(s), effects on tumor microenvironment, safety, derivatives, and tumor‐specific drug delivery; after that we also discuss the translational potential of salinomycin toward clinical application based on current multifaceted understandings.

The Unsupervised Feature Selection Algorithms Based on Standard Deviation and Cosine Similarity for Genomic Data Analysis

To tackle the challenges in genomic data analysis caused by their tens of thousands of dimensions while having a small number of examples and unbalanced examples between classes, the technique of unsupervised feature selection based on standard deviation and cosine similarity is proposed in this paper. We refer to this idea as SCFS (Standard deviation and Cosine similarity based Feature Selection). It defines the discernibility and independence of a feature to value its distinguishable capability between classes and its redundancy to other features, respectively. A 2-dimensional space is constructed using discernibility as x-axis and independence as y-axis to represent all features where the upper right corner features have both comparatively high discernibility and independence. The importance of a feature is defined as the product of its discernibility and its independence (i.e., the area of the rectangular enclosed by the feature’s coordinate lines and axes). The upper right corner features are by far the most important, comprising the optimal feature subset. Based on different definitions of independence using cosine similarity, there are three feature selection algorithms derived from SCFS. These are SCEFS (Standard deviation and Exponent Cosine similarity based Feature Selection), SCRFS (Standard deviation and Reciprocal Cosine similarity based Feature Selection) and SCAFS (Standard deviation and Anti-Cosine similarity based Feature Selection), respectively. The KNN and SVM classifiers are built based on the optimal feature subsets detected by these feature selection algorithms, respectively. The experimental results on 18 genomic datasets of cancers demonstrate that the proposed unsupervised feature selection algorithms SCEFS, SCRFS and SCAFS can detect the stable biomarkers with strong classification capability. This shows that the idea proposed in this paper is powerful. The functional analysis of these biomarkers show that the occurrence of the cancer is closely related to the biomarker gene regulation level. This fact will benefit cancer pathology research, drug development, early diagnosis, treatment and prevention.

Maspin suppresses cell invasion and migration in gastric cancer through inhibiting EMT and angiogenesis via ITGB1/FAK pathway

This study aims to investigate how Maspin affects the EMT and angiogenesis of gastric cancer (GC) cells via ITGB1/FAK pathway. Immunohistochemistry was used to evaluate the expressions of Maspin, ITGB1, FAK, E-cadherin, Vimentin, D2-40, and CD34 in GC and adjacent normal tissues from 160 patients. Then, the human GC cells with different degree of differentiation were transfected with Maspin CRISPR activation plasmid, ITGB1 siRNA and/or Maspin siRNA, followed by the following experiments, including qRT-PCR, western blotting, tube formation assay, Transwell assay and wound healing. GC tumor tissues manifested decreased Maspin with the activated ITGB1/FAK pathway. In tumor tissues, Maspin was negatively correlated with the expressions of ITGB1 and FAK, as well as Lauren's classification, differentiation degree, and TNM stage. Besides, Maspin was negatively related with lymphatic vessel density (LVD) and microvessel density (MVD), Vimentin and VEGF, but was positive correlated with E-cadherin. Maspin expression decreased, but ITGB1 and p-FAK expressions increased gradually in MKN-28 (well differentiated), SGC-7901 (moderate differentiated), and MKN-45 (poorly differentiated). Maspin CRISPR and ITGB1 siRNA increased E-cadherin with the decreased Vimentin, VEGF and bFGF, and the reductions of tube length. In comparison with the ITGB1 siRNA group, cells in the Maspin siRNA + ITGB1 siRNA group presented the more evident EMT and angiogenesis. Furthermore, ITGB1 siRNA reduced the malignancies of GC cells, which could be restored by Maspin siRNA. Maspin was downregulated in GC tissues, which could inhibit the EMT and angiogenesis by blocking the ITGB1/FAK pathway, thereby decreasing cell invasion and migration of GC.

Tackling tumor heterogeneity and phenotypic plasticity in cancer precision medicine: our experience and a literature review

The predominant cause of cancer mortality is metastasis. The major impediment to cancer cure is the intrinsic or acquired resistance to currently available therapies. Cancer is heterogeneous at the genetic, epigenetic, and metabolic levels. And, while a molecular-targeted drug may be pathway-precise, it can still fail to achieve wholesome cancer-precise toxicity. In the current review, we discuss the strategic differences between targeting the strengths of cancer cells in phenotypic plasticity and heterogeneity and targeting shared vulnerabilities of cancer cells such as the compromised integrity of membranous organelles. To better recapitulate subpopulations of cancer cells in different phenotypic and functional states, we developed a schematic combination of 2-dimensional culture (2D), 3-dimmensional culture in collagen I (3D), and mammosphere culture for stem cells (mammosphere), designated as Scheme 2D/3D/mammosphere. We investigated how the tumor suppressor maspin may limit carcinoma cell plasticity and affect their context-dependent response to drugs of different mechanisms including docetaxel, histone deacetylase (HDAC) inhibitor MS-275, and ionophore antibiotic salinomycin. We showed that tumor cell phenotypic plasticity is not an exclusive attribute to cancer stem cells. Nonetheless, three subpopulations of prostate cancer cells, enriched through Scheme 2D/3D/mammosphere, show qualitatively different drug responses. Interestingly, salinomycin was the only drug that effectively killed all three cancer cell subpopulations, irrespective of their capacity of stemness. Further, Scheme 2D/3D/mammosphere may be a useful model to accelerate the screening for curative cancer drugs while avoiding costly characterization of compounds that may have only selective toxicity to some, but not all, cancer cell subpopulations.

Maspin differential expression patterns as a potential marker for targeted screening of esophageal adenocarcinoma/gastroesophageal junction adenocarcinoma

AIM

Barrett's esophagus (BE) is a predisposing factor of esophageal adenocarcinoma/gastroesophageal junction adenocarcinoma (ECA/GEJ Aca). BE patients are stratified and subsequently monitored according to the risk of malignant progression by the combination of endoscopy and biopsy. This study is to evaluate the maspin expression patterns as early diagnostic markers of malignancy in BE patients.

MATERIALS AND METHODS

Immunohistochemistry (IHC) staining was performed on 62 archival core biopsies from 35 patients, including BE without dysplasia (intestinal metaplasia, IM), BE with low grade dysplasia, BE with high grade dysplasia, carcinoma in situ, and well to poorly differentiated ECA/GEJ Aca (PD-ECA/GEJ Aca). The intensity and the subcellular distribution of immunoreactivity were evaluated microscopically. Statistical analysis was performed using the χ2 and Fisher exact tests.

RESULTS

The level of epithelial-specific tumor suppressor maspin protein inversely correlated with the progression from IM to PD-ECA/GEJ Aca. Lesions of each pathological grade could be divided into subtypes that exhibited distinct maspin subcellular distribution patterns, including nuclear only (Nuc), combined nuclear and cytoplasmic (Nuc+Cyt), cytoplasmic only (Cyt) and overall negligible (Neg). The Cyt subtype, which was minor in both IM and dysplasia (approximately 10%), was predominant in ECA/GEJ Aca as early as well-differentiated lesions (more than 50%: p = 0.0092). In comparison, nuclear staining of the tumor suppressor TP53 was heterogeneous in dysplasia, and did not correlate with the differentiation grades of ECA/GEJ Aca.

CONCLUSION

The Cyt subtype of maspin expression pattern in core biopsies of BE patients may serve as a molecular marker for early diagnosis of ECA/GEJ Aca.

Targeting AXL overcomes resistance to docetaxel therapy in advanced prostate cancer

Resistance to docetaxel is a major clinical problem in advanced prostate cancer. The overexpression of AXL receptor tyrosine kinase (AXL) has been correlated with chemotherapeutic drug resistance. However, the role of AXL expression in docetaxel resistance in prostate cancer is yet unclear. In this study, we demonstrate that AXL is overexpressed and activated independent of Gas6 in docetaxel-resistant prostate cancer cells (PC3-DR and DU145-DR). Moreover, we show that forced overexpression of AXL in PC3 and DU145 cells is sufficient to induce resistance to docetaxel in these cell lines. Notably, genetic or pharmacologic inhibition of AXL in the resistant models suppressed cell proliferation, migration, invasion, and tumor growth, and these effects were significantly augmented when AXL inhibition was combined with docetaxel treatment. Mechanistically, we found that AXL inhibition led to reversion of the epithelial-mesenchymal transition (EMT) phenotype and decreased the expression of ATP-binding cassette B1 (ABCB1). Overall, our results identify AXL as an important mediator of docetaxel resistance in prostate cancer. We propose that AXL-targeted therapy, in combination with docetaxel, has the potential to improve the response to docetaxel therapy and reduce resistance induced by prolonged docetaxel therapy in prostate cancer.

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.

Inhibiting autophagy overcomes docetaxel resistance in castration-resistant prostate cancer cells

Background

This study investigates the docetaxel-resistant mechanism and explores the effect of tea polyphenols (TP) on autophagy and its related mechanism in human castration-resistant prostate cancer (CRPC) cell lines PC3 and DU145.

Methods

Immunofluorescence assay and annexin V-FITC/PI double staining flow cytometry were used to analyze the apoptosis and autophagy of PC3 and DU145 cells. The expression of autophagy-related proteins was detected by western bolt.

Results

Docetaxel could induce autophagy and apoptosis, together with the expression increase in p-JNK, p-Bcl-2 and Beclin1. The level of autophagy was remarkably decreased, but apoptosis was increased after combining with TP. In addition, the expression of p-mTOR was increased after combining with TP.

Conclusion

Docetaxel induces protective autophagy in CRPC cells by JNK pathway activation and then Bcl-2 phosphorylation and Beclin1 dissociation. TP activates mTOR pathway, which ultimately inhibits docetaxel-induced autophagy and improves therapeutic efficacy of docetaxel in CRPC cells.

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.

An Essential Role of Maspin in Embryogenesis and Tumor Suppression

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

Tumor suppressor maspin as a modulator of host immune response to cancer

Despite the promising clinical outcome, the primary challenge of the curative cancer immunotherapy is to overcome the dichotomy of the immune response: tumor-evoked immunostimulatory versus tumor-induced immunosuppressive. The goal needs to be two-fold, to re-establish sustainable antitumor-cancer immunity and to eliminate immunosuppression. The successful elimination of cancer cells by immunosurveillance requires the antigenic presentation of the tumor cells or tumor-associated antigens and the expression of immunostimulatory cytokines and chemokines by cancer and immune cells. Tumors are heterogeneous and as such, some of the tumor cells are thought to have stem cell characteristics that enable them to suppress or desensitize the host immunity due to acquired epigenetic changes. A central mechanism underlying tumor epigenetic instability is the increased histone deacetylase (HDAC)-mediated repression of HDAC-target genes regulating homeostasis and differentiation. It was noted that pharmacological HDAC inhibitors are not effective in eliminating tumor cells partly because they may induce immunosuppression. We have shown that epithelial-specific tumor suppressor maspin, an ovalbumin-like non-inhibitory serine protease inhibitor, reprograms tumor cells toward better differentiated phenotypes by inhibiting HDAC1. Recently, we uncovered a novel function of maspin in directing host immunity towards tumor elimination. In this review, we discuss the maspin and maspin/HDAC1 interplay in tumor biology and immunology. We propose that maspin based therapies may eradicate cancer.