Maspin expression in prostate tumor elicits host anti-tumor immunity.

The goal of the current study is to examine the biological effects of epithelial-specific tumor suppressor maspin on tumor host immune response. Accumulated evidence demonstrates an anti-tumor effect of maspin on tumor growth, invasion and metastasis. The molecular mechanism underlying these biological functions of maspin is thought to be through histone deacetylase inhibition, key to the maintenance of differentiated epithelial phenotype. Since tumor-driven stromal reactivities co-evolve in tumor progression and metastasis, it is not surprising that maspin expression in tumor cells inhibits extracellular matrix degradation, increases fibrosis and blocks hypoxia-induced angiogenesis. Using the athymic nude mouse model capable of supporting the growth and progression of xenogeneic human prostate cancer cells, we further demonstrate that maspin expression in tumor cells elicits neutrophil- and B cells-dependent host tumor immunogenicity. Specifically, mice bearing maspin-expressing tumors exhibited increased systemic and intratumoral neutrophil maturation, activation and antibody-dependent cytotoxicity, and decreased peritumoral lymphangiogenesis. These results reveal a novel biological function of maspin in directing host immunity towards tumor elimination that helps explain the significant reduction of xenograft tumor incidence in vivo and the clinical correlation of maspin with better prognosis of several types of cancer. Taken together, our data raised the possibility for novel maspin-based cancer immunotherapies.

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

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

Maspin 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 TGFß 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.

A qualitative study to understand barriers to implementation of national guidelines for prehospital termination of unsuccessful resuscitation efforts.

BACKGROUND: The American Heart Association's (AHA's) Advanced Cardiac Life Support guidelines act as the national standards for termination of resuscitation (TOR) in cases of refractory out-of-hospital cardiac arrest. However, local emergency medical services (EMS) implementation of these guidelines has been nonuniform. OBJECTIVE: To identify the operational issues within local EMS systems that may serve as barriers or facilitators to full acceptance of national guidelines for prehospital TOR in appropriate circumstances. Methods. We conducted three focus groups at the January 2008 National Association of EMS Physicians (NAEMSP) annual meeting. Snowball sampling was used to recruit 19 physicians, two EMS providers, one research director, one nurse, and one medical student attending the conference. Two reviewers analyzed the data in an iterative process to identify recurrent and unifying themes. RESULTS: We identified three distinct stakeholder groups whose current beliefs and practices may influence local implementation of TOR: EMS providers with variations in education and work culture; EMS medical directors with responsibility but little authority; and online medical control physicians who do not communicate effectively with the other groups. Our focus group participants suggested that national organizations, such as the AHA and the American College of Emergency Physicians, may serve a role in overcoming the overarching barriers of communication, standardized educational requirements, and coordination of local services. CONCLUSION: We have identified operational barriers that may impede implementation of TOR guidelines. Three influential stakeholder groups will need to work with national organizations to overcome these local barriers.

A qualitative study to identify barriers to local implementation of prehospital termination of resuscitation protocols.

BACKGROUND: Despite the existence of national American Heart Association guidelines and 2 termination-of-resuscitation (TOR) rules for ceasing efforts in refractory out-of-hospital cardiac arrest, many emergency medical services agencies in the United States have adopted their own local protocols. Public policies and local perceptions may serve as barriers or facilitators to implementing national TOR guidelines at the local level. METHODS AND RESULTS: Three focus groups, lasting 90 to 120 minutes, were conducted at the National Association of Emergency Medical Services Physicians meeting in January 2008. Snowball sampling was used to recruit participants. Two reviewers analyzed the data in an iterative process to identify recurrent and unifying themes. We identified 3 distinct groups whose current policies or perceptions may impede efforts to adopt national TOR guidelines: payers who incentivize transport; legislators who create state mandates for transport and allow only narrow use of do-not-resuscitate orders; and communities where cultural norms are perceived to impede termination of resuscitation. Our participants suggested that national organizations, such as the American Heart Association and American College of Emergency Physicians, may serve as potential facilitators in addressing these barriers by taking the lead in asking payers to change reimbursement structures; encouraging legislators to revise laws to reflect the best available medical evidence; and educating the public that rapid transport to the hospital cannot substitute for optimal provision of prehospital care. CONCLUSIONS: We have identified 3 influential groups who will need to work with national organizations to overcome current policies or prevailing perceptions that may impede implementing national TOR guidelines.