Inhibition of PC cell-derived growth factor (PCDGF, epithelin/granulin precursor) expression by antisense PCDGF cDNA transfection inhibits tumorigenicity of the human breast carcinoma cell line MDA-MB-468

Progranulinopathy: A diverse realm of disorders linked to progranulin imbalances

Progranulin (PGRN), encoded by the GRN gene in humans, was originally isolated as a secreted growth factor that implicates in a multitude of processes ranging from regulation of tumorigenesis, inflammation to neural proliferation. Compelling evidence indicating that GRN mutation can lead to various common neuronal degenerative diseases and rare lysosomal storage diseases. These findings have unveiled a critical role for PGRN as a lysosomal protein in maintaining lysosomal function. The phenotypic spectrum of PGRN imbalance has expanded to encompass a broad spectrum of diseases, including autoimmune diseases, metabolic, musculoskeletal and cardiovascular diseases. These diseases collectively referred to as Progranulinopathy- a term encompasses the wide spectrum of disorders influenced by PGRN imbalance. Unlike its known extracellular function as a growth factor-like molecule associated with multiple membrane receptors, PGRN also serves as an intracellular co-chaperone engaged in the folding and traffic of its associated proteins, particularly the lysosomal hydrolases. This chaperone activity is required for PGRN to exert its diverse functions across a broad range of diseases, encompassing both the central nervous system and peripheral systems. In this comprehensive review, we present an update of the emerging role of PGRN in Progranulinopathy, with special focus on elucidating the intricate interplay between PGRN and a diverse array of proteins at various levels, ranging from extracellular fluids and intracellular components, as well as various pathophysiological processes involved. This review seeks to offer a comprehensive grasp of PGRN's diverse functions, aiming to unveil intricate mechanisms behind Progranulinopathy and open doors for future research endeavors.

Progranulin Oncogenic Network in Solid Tumors

Progranulin is a pleiotropic growth factor with important physiological roles in embryogenesis and maintenance of adult tissue homeostasis. While-progranulin deficiency is associated with a broad range of pathological conditions affecting the brain, such as frontotemporal dementia and neuronal ceroid lipofuscinosis, progranulin upregulation characterizes many tumors, including brain tumors, multiple myeloma, leiomyosarcoma, mesothelioma and epithelial cancers such as ovarian, liver, breast, bladder, adrenal, prostate and kidney carcinomas. The increase of progranulin levels in tumors might have diagnostic and prognostic significance. In cancer, progranulin has a pro-tumorigenic role by promoting cancer cell proliferation, migration, invasiveness, anchorage-independent growth and resistance to chemotherapy. In addition, progranulin regulates the tumor microenvironment, affects the function of cancer-associated fibroblasts, and modulates tumor immune surveillance. However, the molecular mechanisms of progranulin oncogenic function are not fully elucidated. In bladder cancer, progranulin action relies on the activation of its functional signaling receptor EphA2. Notably, more recent data suggest that progranulin can also modulate a functional crosstalk between multiple receptor-tyrosine kinases, demonstrating a more complex and context-dependent role of progranulin in cancer. Here, we will review what is currently known about the function of progranulin in tumors, with a focus on its molecular mechanisms of action and regulation.

Progranulin (PGRN) as a regulator of inflammation and a critical factor in the immunopathogenesis of cardiovascular diseases

Immune dysregulation has been identified as a critical cause of the most common types of cardiovascular diseases (CVDs). Notably, the innate and adaptive immune responses under physiological conditions are typically regulated with high sensitivity to avoid the exacerbation of inflammation, but any dysregulation can probably be associated with CVDs. In this respect, progranulin (PGRN) serves as one of the main components of the regulation of inflammatory processes, which significantly contributes to the immunopathogenesis of such disorders. PGRN has been introduced among the secreted growth factors as one related to wound healing, inflammation, and human embryonic development, as well as a wide variety of autoimmune diseases. The relationship between the serum PGRN and TNF-α ratio with the spontaneous bacterial peritonitis constitute one of the independent predictors of these conditions. The full-length PGRN can thus effectively reduce the calcification of valve interstitial cells, and the granulin precursor (GRN), among the degradation products of PGRN, can be beneficial. Moreover, it was observed that, PGRN protects the heart against ischemia-reperfusion injury. Above all, PGRN also provides protection in the initial phase following myocardial ischemia-reperfusion injury. The protective impact of PGRN on this may be associated with the early activation of the PI3K/Akt signaling pathway. PGRN also acts as a protective factor in hyperhomocysteinemia, probably by down-regulating the wingless-related integration site Wnt/β-catenin signaling pathway. Many studies have further demonstrated that SARS-CoV-2 (COVID-19) has dramatically increased the risks of CVDs due to inflammation, so PGRN has drawn much more attention among scholars. Lysosomes play a pivotal role in the inflammation process, and PGRN is one of the key regulators in their functioning, which contributes to the immunomodulatory mechanism in the pathogenesis of CVDs. Therefore, investigation of PGRN actions can help find new prospects in the treatment of CVDs. This review aims to summarize the role of PGRN in the immunopathogenesis of CVD, with an emphasis on its treatment.

Economical gold recovery cycle from bio-sensing AuNPs: an application for nanowaste and COVID-19 testing kits

We report the controlled growth of biologically active compounds: gold nanoparticles (AuNPs) in various shapes, including their green synthesis, characterization, and studies of their applications towards biological, degradation and recycling. Using spectroscopic methods, studies on responsive binding mechanisms of AuNPs with biopolymers herring sperm deoxyribonucleic acid (hsDNA), bovine serum albumin (BSA), dyes degradation study, and exquisitely gold separation studies/recovery from nanowaste, COVID-19 testing kits, and pregnancy testing kits are discussed. The sensing ability of the AuNPs with biopolymers was investigated via various analytical techniques. The rate of degradation of various dyes in the presence and absence of AuNPs was studied by deploying stirring, IR, solar, and UV-Vis methods. AuNPs were found to be the most active cytotoxic agent against human breast cancer cell lines such as MCF-7 and MDAMB-468. Furthermore, an economical process for the recovery of gold traces from nanowaste, COVID-19 detection kits, and pregnancy testing kits was developed using inexpensive and eco-friendly α-cyclodextrin sugar. This method was found to be easy and safest in comparison with the universally accepted cyanidation process. In the future, small gold jewelry makers and related industries would benefit from the proposed gold-recycling process and it might contribute to their socio-economic growth. The methodologies proposed are also beneficial for trace-level forensic investigation.

Helicobacter pylori-Induced Progranulin Promotes the Progression of the Gastric Epithelial Cell Cycle by Regulating CDK4

Helicobacter pylori, a group 1 carcinogen, colonizes the stomach and affects the development of stomach diseases. Progranulin (PGRN) is an autocrine growth factor that regulates multiple cellular processes and plays a tumorigenic role in many tissues. Nevertheless, the mechanism of action of PGRN in gastric cancer caused by H. pylori infection remains unclear. Here, we investigated the role of PGRN in cell cycle progression and the cell proliferation induced by H. pylori infection. We found that the increased PGRN was positively associated with CDK4 expression in gastric cancer tissue. PGRN was upregulated by H. pylori infection, thereby promoting cell proliferation, and that enhanced level of proliferation was reduced by PGRN inhibitor. CDK4, a target gene of PGRN, is a cyclin-dependent kinase that binds to cyclin D to promote cell cycle progression, which was upregulated by H. pylori infection. We also showed that knockdown of CDK4 reduced the higher cell cycle progression caused by upregulated PGRN. Moreover, when the PI3K/Akt signaling pathway (which is promoted by PGRN) was blocked, the upregulation of CDK4 mediated by PGRN was reduced. These results reveal the potential mechanism by which PGRN plays a major role through CDK4 in the pathological mechanism of H. pylori infection.

Progranulin promotes hippocampal neurogenesis and alleviates anxiety-like behavior and cognitive impairment in adult mice subjected to cerebral ischemia

Aims

Cerebral ischemia can lead to anxiety and cognitive impairment due to the loss of hippocampal neurons. Facilitation of endogenous neurogenesis in the hippocampus is a potential therapeutic strategy for alleviating ischemia‐induced anxiety and cognitive impairment. Progranulin (PGRN), a secretory glycoprotein, has been reported to have a mitogentic effect on many cell types. However, it is not clear whether PGRN enhances hippocampal neurogenesis and promotes functional recovery.

Methods

Adult male C57BL/6 mice were subjected to permanent middle cerebral artery occlusion (pMCAO) and injected intracerebroventricularly with recombinant mouse PGRN 30 min after pMCAO. Anxiety‐like behavior was detected by the open field and the elevated plus maze tests, and spatial learning and memory abilities were evaluated by Morris water maze. Neurogenesis was examined by double labeling of BrdU and neural stem cells or neurons markers. For mechanism studies, the level of ERK1/2 and AKT phosphorylation were assessed by western blotting.

Results

Progranulin significantly alleviated anxiety‐like behavior and spatial learning and memory impairment induced by cerebral ischemia in mice. Consistent with the functional recovery, PGRN promoted neural stem cells (NSCs) proliferation and neuronal differentiation in the dentate gyrus (DG) after cerebral ischemia. PGRN upregulated the expression of phosphorylated ERK1/2 and Akt in the DG after cerebral ischemia.

Conclusions

Progranulin alleviates ischemia‐induced anxiety‐like behavior and spatial learning and memory impairment in mice, probably via stimulation of hippocampal neurogenesis mediated by activation of MAPK/ERK and PI3K/Akt pathways. PGRN might be a promising candidate for coping with ischemic stroke‐induced mood and cognitive impairment in clinic.

Progranulin: A proangiogenic factor in visceral adipose tissue in tumoral and non-tumoral visceral pathology

The connection between central obesity and the development and metastasis of various visceral tumors is largely accepted and one of the main causes seems to be the local synthesis of proangiogenic molecules. Progranulin (PRG), recently identified as an adipokine, is a novel pleiotropic growth factor acting on the proliferation and development of fast-growing epithelial cells, cancer cells, and also a proangiogenic factor whose expression is induced in activated endothelial cells. One of the molecules that seems to trigger the angiogenic activity of PRG is vascular endothelial growth factor (VEGF). Two groups of human subjects were considered and adipose tissue was processed for an immunohistochemical and morphometric study after surgery for abdominal tumoral or non-tumoral pathology. The presence of PRG in adipose pads of the omentum was analyzed and its association with VEGF, CD34 and collagen IV in tumoral and non-tumoral visceral pathology was examined. The results showed that PRG but not VEGF expression was upregulated in adipose tissue in tumoral visceral pathology. In conclusion, the involvement of the proangiogenic activity of PRG and VEGF in adipose tissue under tumor conditions may be dependent on the visceral tumor type.

Circulating Biomarkers in Breast Cancer

Breast cancer management has progressed immensely over the decades, but the disease is still a major source of morbidity and mortality worldwide. Even with enhanced imaging detection and tissue biopsy capabilities, disease can progress on an ineffective treatment before additional information is obtained through standard methods of response evaluation, including the RECIST 1.1 criteria, widely used for assessment of treatment response and benefit from therapy.⁶ Circulating biomarkers have the potential to provide valuable insight into disease progression and response to therapy, and they can serve to identify actionable mutations and tumor characteristics that can direct therapy. These biomarkers can be collected at higher frequencies than imaging or tissue sampling, potentially allowing for more informed management. This review will evaluate the roles of circulating biomarkers in breast cancer, including the serum markers Carcinoembryonic antigen CA15-3, CA27-29, HER2 ECD, and investigatory markers such as GP88; and the components of the liquid biopsy, including circulating tumor cells, cell free DNA/DNA methylation, circulating tumor DNA, and circulating microRNA.

A narrative review of multiple mechanisms of progranulin in cancer: a potential target for anti-cancer therapy

Progranulin (PGRN) is an autocrine growth factor and has important effects on regulation of cell growth, motility, tissue repair and embryonic development. Recent years, several researches found the expression of PGRN was at higher levels in a number of cancer cells and its high levels are associated with poor outcome of patients. More and more studies investigated the role of PGRN in cancer and found PGRN exerted various biological functions in cancer cells, such as promoting proliferation, inhibiting apoptosis, inducing migration and invasion of cells, accelerating angiogenesis and enhancing the effectiveness of chemoresistance and radiation. Now the effects of PGRN have been demonstrated in several cancers, including breast cancer, lung cancer, and bladder cancer. In addition, several signaling pathways and molecules are involved in the effects of PGRN on cancer cells, including Akt, mitogen-activated protein kinase (MAPK), vascular endothelial growth factor (VEGF) and cyclin D1. Therefore, PGRN is probably a significant diagnostic and prognostic biomarker for cancer and may be a potential target for anti-cancer therapy. Here, we reviewed the advancing field of PGRN in cancer as well as several signaling pathways activated by PGRN and confirmed PGRN is a key role in cancer. Moreover, future studies are still necessary to elucidate the biological functions and signaling pathways of PGRN in cancer.

GP88/PGRN Serum Levels Are Associated with Prognosis for Oral Squamous Cell Carcinoma Patients

Simple Summary

An oral squamous cell carcinoma (OSCC) is a tumor of the oral cavity that has a five-year survival rate of only around 50%. As this rate has not increased in recent decades, despite improvements in diagnosis and therapy, novel, easily accessible biomarkers for prognosis assessment are still needed. In our study, we measured the growth factor protein progranulin/GP88 in the serum of OSCC patients and demonstrated that an increased serum GP88 level is associated with a better prognosis for the OSCC patients in our study group. Furthermore, serum GP88 levels were not significantly associated with age, sex, or the tumor’s histological features, indicating that serum GP88 levels may be an independent predictor of an individual OSCC patient’s prognosis. These findings may help to improve therapy management of an OSCC in personalized medicine.

Abstract

Progranulin (PGRN)/GP88 is a growth factor that is expressed in a wide range of tumor tissues. The secreted form is involved in various biological processes including proliferation and inflammation. In several tumor types, the serum GP88 level is associated with a patient’s prognosis; however, data for oral squamous cell carcinomas (OSCCs) have not yet been reported. We measured the serum GP88 levels in 96 OSCC patients by an enzyme immunosorbent assay (EIA) and correlated these data with clinicopathological parameters and patient outcomes. The GP88 levels in the serum of OSCC patients and healthy volunteers were comparable. In OSCC patients, the levels did not correlate with age, sex, or TNM status. In a Kaplan–Meier survival analysis, a serum GP88 level < 68 ng/mL was significantly associated with worsened survival (p = 0.0005, log-rank-test) as well as in uni- and multivariate Cox regression analyses (RR = 4.6 [1.6–12.9], p = 0.004 and RR = 4.2 [1.2–12.0], p = 0.008). This effect was predominant in OSCC patients older than 60.5 years (p = 0.027), while in younger patients no significant association between serum GP88 levels and prognosis could be observed. Altogether, lower serum GP88 levels are significantly associated with a worsened outcome for an OSCC and may be an interesting candidate for risk stratification during OSCC therapy.

The converging roles of Batten disease proteins in neurodegeneration and cancer

Epidemiological studies have reported an inverse correlation between cancer and neurodegenerative disorders, and increasing evidence shows that similar genes and pathways are dysregulated in both diseases but in a contrasting manner. Given the genetic convergence of the neuronal ceroid lipofuscinoses (NCLs), a family of rare neurodegenerative disorders commonly known as Batten disease, and other neurodegenerative diseases, we sought to explore the relationship between cancer and the NCLs. In this review, we survey data from The Cancer Genome Atlas and available literature on the roles of NCL genes in different oncogenic processes to reveal links between all the NCL genes and cancer-related processes. We also discuss the potential contributions of NCL genes to cancer immunology. Based on our findings, we propose that further research on the relationship between cancer and the NCLs may help shed light on the roles of NCL genes in both diseases and possibly guide therapy development.

Tumor co-expression of progranulin and sortilin as a prognostic biomarker in breast cancer

Background

The growth factor progranulin has been implicated in numerous biological processes such as wound healing, inflammation and progressive tumorigenesis. Both progranulin and its receptor sortilin are known to be highly expressed in subgroups of breast cancer and have been associated with various clinical properties including tamoxifen resistance. Recent data further suggest that progranulin, via its receptor sortilin, drives breast cancer stem cell propagation in vitro and increases metastasis formation in an in vivo breast cancer xenograft model. In this retrospective biomarker analysis, we aimed to determine whether tumor co-expression of progranulin and sortilin has prognostic and treatment predictive values for breast cancer patients.

Methods

We explored how co-expression of progranulin and sortilin was associated with established clinical markers by analyzing a tissue microarray including 560 randomized premenopausal breast cancer patients receiving either 2 years of tamoxifen treatment or no adjuvant treatment, with a median follow-up time of 28 years. Breast cancer-specific survival was analyzed using Kaplan-Meier and Cox Proportional Hazards regression models to assess the prognostic and predictive value of progranulin and sortilin in relation to known clinical markers.

Results

Co-expression of progranulin and sortilin was observed in 20% of the breast cancer samples. In untreated patients, prognostic considerations could be detailed separately from treatment prediction and the high progranulin and sortilin expressing subgroup was significantly associated with breast cancer-specific death in multivariable analyses (HR=2.188, CI: 1.317–3.637, p=0.003) along with tumor size, high tumor grade and lymph node positivity. When comparing the untreated patients with tamoxifen treated patients in the ERα positive subgroup, co-expression of progranulin and sortilin was not linked to tamoxifen resistance.

Conclusion

Data suggest that co-expression of progranulin and its receptor sortilin is a novel prognostic biomarker combination identifying a highly malignant subgroup of breast cancer. Importantly, this subpopulation could potentially be targeted with anti-sortilin based therapies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-07854-0.

Lysosomal Dysfunction and Other Pathomechanisms in FTLD: Evidence from Progranulin Genetics and Biology

It has been more than a decade since heterozygous loss-of-function mutations in the progranulin gene (GRN) were first identified as an important genetic cause of frontotemporal lobar degeneration (FTLD). Due to the highly diverse biological functions of the progranulin (PGRN) protein, encoded by GRN, multiple possible disease mechanisms have been proposed. Early work focused on the neurotrophic properties of PGRN and its role in the inflammatory response. However, since the discovery of homozygous GRN mutations in patients with a lysosomal storage disorder, investigation into the possible roles of PGRN and its proteolytic cleavage products granulins, in lysosomal function and dysfunction, has taken center stage. In this chapter, we summarize the GRN mutational spectrum and its associated phenotypes followed by an in-depth discussion on the possible disease mechanisms implicated in FTLD-GRN. We conclude with key outstanding questions which urgently require answers to ensure safe and successful therapy development for GRN mutation carriers.

Suppression of Progranulin Expression Leads to Formation of Intranuclear TDP-43 Inclusions In Vitro: A Cell Model of Frontotemporal Lobar Degeneration

Mutations in the GRN gene coding for progranulin (PGRN) are responsible for many cases of familial frontotemporal lobar degeneration (FTLD) with TAR DNA-binding protein 43 (TDP-43)-positive inclusions (FTLD-TDP). GRN mutations create null alleles resulting in decreased progranulin protein or haploinsufficiency. FTLD-TDP with GRN mutations is characterized by lentiform neuronal intranuclear inclusions that are positive for TDP-43 in affected brain regions. In this study, by stably expressed short hairpin RNA, we established a neuroblastoma cell line with decreased PGRN level. This cell line reveals TDP-43-positive intranuclear inclusions. In addition, replacement with purified PGRN protein restores normal TDP-43 nuclear distribution. This cell model can be valuable for the study of the role of PGRN in the pathogenesis in FTLD-TDP.

Serum progranulin/tumor necrosis factor-α ratio as independent predictor of systolic blood pressure in overweight hypertensive patients: a cross-sectional study

Background

Vascular inflammation plays a key role in the progression of hypertension. Progranulin (PGRN), an anti-inflammatory growth factor, mediated inhibition of tumor necrosis factor-α (TNF-α), a pleiotropic cytokine, activity has been well-established. Despite the role of chronic low-grade inflammation in hypertension, serum levels of PGRN and PGRN/TNF-α ratio and, their association with systolic and diastolic blood pressure has not been determined in hypertensive patients till now. This study aims to find and correlate the serum levels of pro-inflammatory cytokine (TNF-α), anti-inflammatory growth factor (PGRN), and PGRN/TNF-α ratio with the blood pressure in systolic-diastolic hypertension (SDH) and isolated systolic hypertension (ISH) patients.

Results

A cross-sectional study was conducted on SDH patients (mean age, 52.95 ± 12.6 years; male/female (M/F) number = 15/10) and ISH patients (mean age, 55.80 ± 9.40 years; M/F number = 12/13) (n = 25 each). Twenty-five age and body mass index (BMI)-matched healthy subjects (mean age, 56.00 ± 8.55 years; male/female number = 11/14) were considered as control. All patients and healthy subjects were overweight (BMI, 25–30 kg/m²). Overnight fasting blood samples of subjects were taken and levels of PGRN and TNF-α were measured using ELISA diagnostic kits. PGRN and TNF-α levels were found significantly high, whereas PGRN/TNF ratio was found very low, in SDH and ISH patients as compared to healthy subjects. Reduced PGRN/TNF-α ratio and pulse pressure were found as independent predictors of SBP both in SDH and ISH patients.

Conclusions

Findings of elevated PGRN levels in response to raised TNF-α levels depict the counter regulation by PGRN to neutralize TNF-α. Findings of reduced PGRN/TNF ratio, and it being an independent predictor of SBP, ascertain the key role of imbalance in pro- and anti-inflammatory environment in hypertension. Thus, it strengthens the cross-link between the concept of immunity–adiposity–inflammation–blood pressure¸ a vicious network. Further, this cross-link of SBP and progranulin must be explored in longitudinal studies. New researches should be focused not only on impact of pro-inflammatory environment rather to find on a balance between pro- and anti-inflammatory status, so that new target sites could be explored for therapeutic management of hypertension.

Prognostic significance of serum progranulin level in de novo adult acute lymphoblastic leukemia patients

Increased expression of progranulin (PGRN) has been reported in some hematological cancers, but limited information regarding its significance in acute lymphoblastic leukemia (ALL) is available. This study involved 60 subjects (40 de novo adult ALL patients and 20 controls). Serum PGRN level was measured by enzyme-linked immunosorbent assay and was correlated with patient outcome. Serum PGRN level was significantly higher in patients than controls. Serum PGRN level did not correlate with age, total leukocytic count, hemoglobin, platelets, absolute blast count in peripheral blood, lactate dehydrogenase, percent of blasts in bone marrow, gender, comorbidities, the presence of central nervous system infiltration, ALL phenotype, cytogenetics and risk of the disease. High serum PGRN level was not associated with inferior overall survival (OS) on univariate analysis. Regarding cumulative incidence of relapse (CIR) and disease-free survival (DFS), high PGRN level was associated with poor results on univariate analysis. Moreover, it tended to be independent risk factor on multivariate analysis for CIR but was not an independent predictor of inferior DFS. Serum PGRN level is significantly elevated in de novo adult ALL patients and may be used as a predictor of increased relapse risk.

Expression of GP88 (Progranulin) Protein Is an Independent Prognostic Factor in Prostate Cancer Patients

Prostate cancer, the second most common cancer, is still a major cause of morbidity and mortality among men worldwide. The expression of the survival and proliferation factor progranulin (GP88) has not yet been comprehensively studied in PCa tumors. The aim of this study was to characterize GP88 protein expression in PCa by immunohistochemistry and to correlate the findings to the clinico-pathological data and prognosis. Immunohistochemical staining for GP88 was performed by TMA with samples from 442 PCa patients using an immunoreactive score (IRS). Altogether, 233 cases (52.7%) with negative GP88 staining (IRS < 2) and 209 cases (47.3%) with positive GP88 staining (IRS ≥ 2) were analyzed. A significant positive correlation was found for the GP88 IRS with the PSA value at prostatectomy and the cytoplasmic cytokeratin 20 IRS, whereas it was negatively associated with follow-up times. The association of GP88 staining with prognosis was further studied by survival analyses (Kaplan-Meier, univariate and multivariate Cox's regression analysis). Increased GP88 protein expression appeared as an independent prognostic factor for overall, disease-specific and relapse-free survival in all PCa patients. Interestingly, in the subgroup of younger PCa patients (≤65 years), GP88 positivity was associated with a 3.8-fold (p = 0.004), a 6.0-fold (p = 0.008) and a 3.7-fold (p = 0.003) increased risk for death, disease-specific death and occurrence of a relapse, respectively. In the PCa subgroup with negative CK20 staining, GP88 positivity was associated with a 1.8-fold (p = 0.018) and a 2.8-fold increased risk for death and disease-specific death (p = 0.028). Altogether, GP88 protein positivity appears to be an independent prognostic factor for PCa patients.

Sortilin inhibition limits secretion-induced progranulin-dependent breast cancer progression and cancer stem cell expansion

Background

Cancer progression is influenced by genetic aberrations in the cancer cell population as well as by other factors including the microenvironment present within a tumour. Direct interactions between various cell types as well as cellular signalling via secreted cytokines can drive key tumourigenic properties associated with disease progression and treatment resistance. Also, cancer stem cell functions are influenced by the microenvironment. This challenging subset of cells has been linked to malignant properties. Within a screen, using in vivo like growth conditions, we identified progranulin as a highly secreted cytokine affecting cancer stem cells in breast cancer. This cytokine is known to play a role in numerous biological and tumour-related processes including therapy resistance in a range of cancer types.

Methods

Different in vitro and in vivo relevant conditions were used to validate breast cancer stem cell expansion mediated by progranulin and its receptor sortilin. Small interfering ribonucleic acid (siRNA) and pharmacological inhibition of sortilin were used to elucidate the role of sortilin as a functional receptor during progranulin-induced breast cancer stem cell propagation, both in vitro and in vivo, using breast cancer xenograft models. In addition, single-cell gene expression profiling as well as a Sox2 reporter breast cancer cell line were used to validate the role of dedifferentiation mediated by progranulin.

Results

In various in vivo-like screening assays, progranulin was identified as a potent cancer stem cell activator, highly secreted in ERα-negative breast cancer as well as in ERα-positive breast cancer under hypoxic adaptation. Progranulin exposure caused dedifferentiation as well as increased proliferation of the cancer stem cell pool, a process that was shown to be dependent on its receptor sortilin. Subcutaneous injections of progranulin or its active domain (GRN A) induced lung metastases in breast cancer xenograft models, supporting a major role for progranulin in cancer progression. Importantly, an orally bioavailable small molecule (AF38469) targeting sortilin, blocked GRN A-induced lung metastases and prevented cancer cell infiltration of the skin.

Conclusion

The collective results suggest that sortilin targeting represents a potential novel breast cancer therapy approach inhibiting tumour progression driven by secretion and microenvironmental influences.

Electronic supplementary material

The online version of this article (10.1186/s13058-018-1060-5) contains supplementary material, which is available to authorized users.

STAT3 Interactors as Potential Therapeutic Targets for Cancer Treatment

Signal transducers and activators of transcription (STATs) mediate essential signaling pathways in different biological processes, including immune responses, hematopoiesis, and neurogenesis. Among the STAT members, STAT3 plays crucial roles in cell proliferation, survival, and differentiation. While STAT3 activation is transient in physiological conditions, STAT3 becomes persistently activated in a high percentage of solid and hematopoietic malignancies (e.g., melanoma, multiple myeloma, breast, prostate, ovarian, and colon cancers), thus contributing to malignant transformation and progression. This makes STAT3 an attractive therapeutic target for cancers. Initial strategies aimed at inhibiting STAT3 functions have focused on blocking the action of its activating kinases or sequestering its DNA binding ability. More recently, the diffusion of proteomic-based techniques, which have allowed for the identification and characterization of novel STAT3-interacting proteins able to modulate STAT3 activity via its subcellular localization, interact with upstream kinases, and recruit transcriptional machinery, has raised the possibility to target such cofactors to specifically restrain STAT3 oncogenic functions. In this article, we summarize the available data about the function of STAT3 interactors in malignant cells and discuss their role as potential therapeutic targets for cancer treatment.

hsDNA groove binding, photocatalytic activity, and in vitro breast and colon cancer cell reducing function of greener SeNPs

Selenium nanoparticles (SeNPs) have attracted great attention because of their superior optical properties and wide utilization in biological and biomedical studies. This paper reports an environmentally benign procedure of greener monodispersible SeNP synthesis using the reducing power of Trigonella foenum-graecum extract, characterization and their protective effect against unfolded (Herring sperm DNA) hsDNA. We investigated the anti-cancer activity of SeNPs against MCF-7, MDA MB 435 and COLO-205 cells. The photocatalytic activity of SeNPs was investigated for the degradation of a Sunset Yellow FCF (SYFCF) dye using ultraviolet-B light. The reduction of the Se ion to SeNPs was monitored by ultraviolet-visible spectroscopy (UV-vis). The size and morphology of the SeNPs were characterized by high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and Dynamic Light Scattering (DLS). The SeNPs were stable, and the diameter was homogeneous at around 5-12 nm. Interactions of various concentrations of SeNPs with hsDNA were systematically investigated by UV-vis, fluorescence, circular dichroism (CD), polarimetry and FTIR spectroscopy under physiological conditions. The results from fluorescence spectroscopy indicated that SeNPs quenched the fluorescence intensity of hsDNA with increasing concentrations. The modified Stern-Volmer quenching rate constant Ksv, binding constant K and binding sites n at different temperatures and the corresponding thermodynamic parameters ΔH°, ΔG° and ΔS° were calculated. Hoechst 33258 and methyl green (MG) site markers, melting experiment (Tm), viscosity measurements and sequence specificity verification by DNA bases clarified that SeNPs bind to hsDNA via a groove site. The rate of photocatalytic degradation of the SYFCF dye in the presence and absence of photocatalysts (SeNPs) was studied using UV-vis, the results showed appreciable degradation of the SYFCF dye. Our results suggested that nano Se can be used as a promising selenium species with potential application in cancer treatment. These nanoparticles were found to be the most active cytotoxic agent prepared in a new green synthesis manner, causing >50% inhibition of MCF-7, MDA MB-435 and COLO-205 cell proliferation at concentrations <10(-7) M. Hence these SeNPs could be recognized as promising materials for biomedical applications.

Progranulin modulates cholangiocarcinoma cell proliferation, apoptosis, and motility via the PI3K/pAkt pathway

Progranulin (PGRN) is a growth factor normally expressed in rapidly cycling epithelial cells for growth, differentiation, and motility. Several studies have shown the association of PGRN overexpression with the progression of numerous malignancies, including cholangiocarcinoma (CCA). However, the underlying mechanisms on how PGRN modulates CCA cell proliferation and motility is not clear. In this study, we investigated the prognostic significance of PGRN expression in human CCA tissue and the mechanisms of PGRN modulation of CCA cell proliferation and motility. We found that CCA tissues with high PGRN expression were correlated with poor prognosis and likelihood of metastasis. PGRN knockdown KKU-100 and KKU-213 cells demonstrated a reduced rate of proliferation and colony formation and decreased levels of phosphatidyl inositol-3-kinase (PI3K) and phosphorylated Akt (pAkt) proteins. Accumulation of cells at the G1 phase was observed and was accompanied by a reduction of cyclin D1 and CDK4 protein levels. Knockdown cells also induced apoptosis by increasing the Bax-to-Bcl-2 ratio. Increased cell apoptosis was confirmed by annexin V-FITC/PI staining. Moreover, suppression of PGRN reduced CCA cell migration and invasion in vitro. Investigating the biomarkers in epithelial–mesenchymal transition (EMT) revealed a decrease in the expression of vimentin, snail, and metalloproteinase-9. In conclusion, our findings imply that PGRN modulates cell proliferation by dysregulating the G1 phase, inhibiting apoptosis, and that it plays a role in the EMT affecting CCA cell motility, possibly via the PI3K/pAkt pathway.

Suppression of progranulin expression inhibits bladder cancer growth and sensitizes cancer cells to cisplatin

We have recently demonstrated a critical role for progranulin in bladder cancer. Progranulin contributes, as an autocrine growth factor, to the transformed phenotype by modulating Akt-and MAPK-driven motility, invasion and anchorage-independent growth. Progranulin also induces F-actin remodeling by interacting with the F-actin binding protein drebrin. In addition, progranulin is overexpressed in invasive bladder cancer compared to normal tissue controls, suggesting that progranulin might play a key role in driving the transition to the invasive phenotype of urothelial cancer. However, it is not established whether targeting progranulin could have therapeutic effects on bladder cancer. In this study, we stably depleted urothelial cancer cells of endogenous progranulin by shRNA approaches and determined that progranulin depletion severely inhibited the ability of tumorigenic urothelial cancer cells to migrate, invade and grow in anchorage-independency. We further demonstrate that progranulin expression is critical for tumor growth in vivo, in both xenograft and orthotopic tumor models. Notably, progranulin levels correlated with response to cisplatin treatment and were upregulated in bladder tumors. Our data indicate that progranulin may constitute a novel target for therapeutic intervention in bladder tumors. In addition, progranulin may serve as a novel biomarker for bladder cancer.

A Brief Overview of Progranulin in Health and Disease

The purpose of this brief overview of the progranulin protein is to provide a sense of the range and extent of the roles of progranulin in normal physiology and pathology. Progranulin has received attention due to its role in neurodegeneration, where mutation of a single copy of GRN, the gene encoding progranulin, results in frontotemporal dementia, whereas viral delivery of progranulin to the brains of mice exhibiting Parkinson's or Alzheimer's disease phenotypes inhibits the progression of the neurodegenerative phenotypes. Of equal importance, progranulin protects tissues against the harmful effects of poorly controlled inflammation and promotes tissue regeneration after injury at a multitude of sites throughout the body. Progranulin is overexpressed by many types of cancer and contributes to their progression. Given suitable analytical methods and model systems, progranulin offers a wealth of research possibilities.

Progranulin and its biological effects in cancer

Cancer cells have defects in regulatory mechanisms that usually control cell proliferation and homeostasis. Different cancer cells share crucial alterations in cell physiology, which lead to malignant growth. Tumorigenesis or tumor growth requires a series of events that include constant cell proliferation, promotion of metastasis and invasion, stimulation of angiogenesis, evasion of tumor suppressor factors, and avoidance of cell death pathways. All these events in tumor progression may be regulated by growth factors produced by normal or malignant cells. The growth factor progranulin has significant biological effects in different types of cancer. This protein is a regulator of tumorigenesis because it stimulates cell proliferation, migration, invasion, angiogenesis, malignant transformation, resistance to anticancer drugs, and immune evasion. This review focuses on the biological effects of progranulin in several cancer models and provides evidence that this growth factor should be considered as a potential biomarker and target in cancer treatment.

Epithelial requirement for in vitro proliferation and xenograft growth and metastasis of MDA-MB-468 human breast cancer cells: oncogenic rather than tumor-suppressive role of E-cadherin

BACKGROUND

Epithelial-to-mesenchymal transition (EMT) is associated with downregulated E-cadherin and frequently with decreased proliferation. Proliferation may be restored in secondary metastases by mesenchymal-to-epithelial transition (MET). We tested whether E-cadherin maintains epithelial proliferation in MDA-MB-468 breast cancer cells, facilitating metastatic colonization in severe combined immunodeficiency (SCID) mice.

METHODS

EMT/MET markers were assessed in xenograft tumors by immunohistochemistry. Stable E-cadherin manipulation was effected by transfection and verified by Western blotting, immunocytochemistry, and quantitative polymerase chain reaction (qPCR). Effects of E-cadherin manipulation on proliferation and chemomigration were assessed in vitro by performing sulforhodamine B assays and Transwell assays, respectively. Invasion was assessed by Matrigel outgrowth; growth in vivo was assessed in SCID mice; and EMT status was assessed by qPCR. Hypoxic response of E-cadherin knockdown cell lines was assessed by qPCR after hypoxic culture. Repeated measures analysis of variance (ANOVA), one- and two-way ANOVA with posttests, and paired Student's t tests were performed to determine significance (p < 0.05).

RESULTS

EMT occurred at the necrotic interface of MDA-MB-468 xenografts in regions of hypoxia. Extratumoral deposits (vascular and lymphatic inclusions, local and axillary nodes, and lung metastases) strongly expressed E-cadherin. MDA-MB-468 cells overexpressing E-cadherin were more proliferative and less migratory in vitro, whereas E-cadherin knockdown (short hairpin CDH1 [shCDH1]) cells were more migratory and invasive, less proliferative, and took longer to form tumors. shCDH1-MDA-MB-468 xenografts did not contain the hypoxia-induced necrotic areas observed in wild-type (WT) and shSCR-MDA-MB-468 tumors, but they did not exhibit an impaired hypoxic response in vitro. Although vimentin expression was not stimulated by E-cadherin knockdown in 2D or 3D cultures, xenografts of these cells were globally vimentin-positive rather than exhibiting regional EMT, and they expressed higher SNA1 than their in vitro counterparts. E-cadherin suppression caused a trend toward reduced lung metastasis, whereas E-cadherin overexpression resulted in the reverse trend, consistent with the increased proliferation rate and predominantly epithelial phenotype of MDA-MB-468 cells outside the primary xenograft. This was also originally observed in WT xenografts. Furthermore, we found that patients with breast cancer that expressed E-cadherin were more likely to have metastases.

CONCLUSIONS

E-cadherin expression promotes growth of primary breast tumors and conceivably the formation of metastases, supporting a role for MET in metastasis. E-cadherin needs to be reevaluated as a tumor suppressor.

The role of progranulin in arthritis

Progranulin (PGRN) is a growth factor with a unique beads-on-a-string structure that is involved in multiple pathophysiological processes, including anti-inflammation, tissue repair, wound healing, neurodegenerative diseases, and tumorigenesis. This review presents up-to-date information concerning recent studies on the role of PGRN in inflammatory arthritis and osteoarthritis, with a special focus on the involvement of the interactions and interplay between PGRN and tumor necrosis factor receptor (TNFR) family members in regulating such musculoskeletal diseases. In addition, this paper highlights the applications of atsttrin, an engineered protein comprising three TNFR-binding fragments of PGRN, as a promising intervention in treating arthritis.

Determination of GP88 (progranulin) expression in breast tumor biopsies improves the risk predictive value of the Nottingham Prognostic Index

Background

The Nottingham Prognostic Index (NPI), which combines numerical values for nodal status, tumor size and histological grade, is used in the standard of care to provide predictive value information on post-surgery survival for patients with primary breast cancer. Attempts to improve the performance of the NPI algorithm have been carried out by testing the inclusion of other biomarker expression and morphological features such as vascular invasion. In the present study, we investigated whether expression of the autocrine growth and survival factor GP88 (progranulin), known to be overexpressed in breast cancer, would improve NPI’s predictive value.

Methods

We examined by immunohistochemistry (IHC) the GP88 expression in 508 cases of estrogen receptor positive invasive ductal carcinoma with known clinical outcomes and for which NPI had been determined. GP88 IHC expression was scored by two board certified pathologists and classified into two score groups of GP88 <3+ (0, 1+, 2+) and GP88 = 3+. The correlation between GP88 scoring, NPI and disease-free (DFS) or overall survival (OS) outcomes was then examined by Kaplan-Meier analysis, Cox proportional Hazard (CPH) ratio and Pearson’s X² test.

Results

Kaplan-Meier survival graphs of cases categorized by their NPI scores (<3.4, 3.4–5.4, >5.4) and GP88 expression showed that for patients within the same NPI subgroup, patients having tumors with a high GP88 expression (GP88 IHC score of 3+) had a worse DFS than patients with tumors that had a low GP88 expression (GP88 IHC score <3+). When adjusted for NPI, high GP88 score was significantly associated with recurrence with a hazard ratio of 3.30 (95 % CI 2.12 to 5.14).

Conclusions

The data suggest that the determination of GP88 tumor expression at time of diagnosis for early stage breast cancer patients can provide additional survival information to that provided by NPI alone and thus may be useful for risk management of patients diagnosed with breast cancer.

An update of biochemical markers of hepatocellular carcinoma

The definition of a tumor marker is broad, which covers a wide spectrum of biomacromolecules synthesized in excess concentration by a wide variety of neoplastic cells. Tumor markers can be normal endogenous products that are produced at a greater rate in cancer cells or the products of newly switched on genes that remained inactive in the normal cells. These markers consist of any products of either tumor itself or the host in reaction to tumor's presence that distinguishes malignant tissues from benign and is measurable in body fluids or tissues. They increase with progressive or recurrent disease, decrease with response to treatment, and normalize with remission. Clinical applications include screening in asymptomatic individuals, confirming a suspected diagnosis, assisting in tumor classification and staging, prognosis, monitoring treatment response, surveillance for residual disease, and early detection of recurrent disease.

The Evolution of the Secreted Regulatory Protein Progranulin

Progranulin is a secreted growth factor that is active in tumorigenesis, wound repair, and inflammation. Haploinsufficiency of the human progranulin gene, GRN, causes frontotemporal dementia. Progranulins are composed of chains of cysteine-rich granulin modules. Modules may be released from progranulin by proteolysis as 6kDa granulin polypeptides. Both intact progranulin and some of the granulin polypeptides are biologically active. The granulin module occurs in certain plant proteases and progranulins are present in early diverging metazoan clades such as the sponges, indicating their ancient evolutionary origin. There is only one Grn gene in mammalian genomes. More gene-rich Grn families occur in teleost fish with between 3 and 6 members per species including short-form Grns that have no tetrapod counterparts. Our goals are to elucidate progranulin and granulin module evolution by investigating (i): the origins of metazoan progranulins (ii): the evolutionary relationships between the single Grn of tetrapods and the multiple Grn genes of fish (iii): the evolution of granulin module architectures of vertebrate progranulins (iv): the conservation of mammalian granulin polypeptide sequences and how the conserved granulin amino acid sequences map to the known three dimensional structures of granulin modules. We report that progranulin-like proteins are present in unicellular eukaryotes that are closely related to metazoa suggesting that progranulin is among the earliest extracellular regulatory proteins still employed by multicellular animals. From the genomes of the elephant shark and coelacanth we identified contemporary representatives of a precursor for short-from Grn genes of ray-finned fish that is lost in tetrapods. In vertebrate Grns pathways of exon duplication resulted in a conserved module architecture at the amino-terminus that is frequently accompanied by an unusual pattern of tandem nearly identical module repeats near the carboxyl-terminus. Polypeptide sequence conservation of mammalian granulin modules identified potential structure-activity relationships that may be informative in designing progranulin based therapeutics.

Increased serum GP88 (Progranulin) concentrations in rheumatoid arthritis

GP88 (Progranulin; PGRN) is a secreted glycosylated protein with important functions in several processes, including immune response and cancer growth. Recent reports have shown that PGRN is a therapeutic target for rheumatoid arthritis (RA) because of its capability to bind with tumor necrosis factor receptor (TNFR). However, the serum PGRN level in RA patients has not been investigated. We used enzyme-linked immunosorbent assay (ELISA) to quantify the serum levels of PGRN in 417 healthy subjects, 56 patients with RA and 31 patients with osteoarthritis (OA). In RA patients, we also measured the serum TNF-α and sTNFR concentration. Immunohistochemical staining of PGRN was performed using synovectomy tissue of RA patients. The serum PGRN normal range was established as 40.1 ± 8.7 ng/ml. PGRN levels were not influenced by sex or age. A significant increase in serum PGRN levels was observed in RA (50.2 ± 11.1 ng/ml) and OA (45.4 ± 6.6 ng/ml) groups compared to those in age-matched healthy controls (40.4 ± 9.9 ng/ml) (p<0.05, Tukey). Further, PGRN levels in the synovial fluid of RA patients (68.4 ± 3.4 ng/ml) were found to be significantly higher than those in OA patients (35.9 ± 16.8 ng/ml). Immunohistochemical staining of PGRN revealed that the highest positive signal was detected in macrophages. Circulating PGRN in RA patients was weakly associated with TNF-α and sTNFR 2 concentration. Furthermore, PGRN/TNF-α ratio was correlated the stage of the disease in RA patients. The concentrations of serum PGRN in RA were found to be significantly higher than those in age-matched healthy controls, although it remains to be clarified how blood PGRN is related to the pathogenesis of RA. Our results showed that the serum PGRN may be a useful approach to monitor the disease activity in RA patients.

Granulin, a novel STAT3-interacting protein, enhances STAT3 transcriptional function and correlates with poorer prognosis in breast cancer

Since the neoplastic phenotype of a cell is largely driven by aberrant gene expression patterns, increasing attention has been focused on transcription factors that regulate critical mediators of tumorigenesis such as signal transducer and activator of transcription 3 (STAT3). As proteins that interact with STAT3 may be key in addressing how STAT3 contributes to cancer pathogenesis, we took a proteomics approach to identify novel STAT3-interacting proteins. We performed mass spectrometry-based profiling of STAT3-containing complexes from breast cancer cells that have constitutively active STAT3 and are dependent on STAT3 function for survival. We identified granulin (GRN) as a novel STAT3-interacting protein that was necessary for both constitutive and maximal leukemia inhibitory factor (LIF)induced STAT3 transcriptional activity. GRN enhanced STAT3 DNA binding and also increased the time-integrated amount of LIF-induced STAT3 activation in breast cancer cells. Furthermore, silencing GRN neutralized STAT3-mediated tumorigenic phenotypes including viability, clonogenesis, and migratory capacity. In primary breast cancer samples, GRN mRNA levels were positively correlated with STAT3 gene expression signatures and with reduced patient survival. These studies identify GRN as a functionally important STAT3-interacting protein that may serve as an important prognostic biomarker and potential therapeutic target in breast cancer.

GP88 (progranulin): a novel tissue and circulating biomarker for non-small cell lung carcinoma

GP88 (progranulin) is a growth and survival factor implicated in tumorigenesis and drug resistance. Previous studies showed that GP88 was expressed in breast cancer tissue in inverse correlation with survival. This study evaluates GP88 tissue expression in localized/locally advanced lung cancer and GP88 serum levels in advanced disease. GP88 expression was determined by immunohistochemistry in tumor tissue from non-small cell lung carcinoma (NSCLC) patients, 85 with localized (stage I-II), and 40 with locally advanced disease (stage IIIa) and correlated with clinical outcome. Serum GP88 levels from stage IIIb/IV patients, quantified by enzyme immunoassay were compared with GP88 levels from patients with chronic obstructive pulmonary disease and healthy individuals. GP88 was expressed in more than 80% adenocarcinoma and squamous cell carcinoma in contrast to normal lung or small cell lung cancer. There was a statistically significant inverse association of GP88 expression (GP88 immunohistochemistry score, 3+ versus < 3+) with survival for patients with localized resected NSCLC with hazard ratio (HR) = 2.28 (P = .0076) for disease-free survival and HR = 2.17 (P = .014) for overall survival. A statistically significant decrease in progression-free survival (HR = 2.9; P = .022) for GP88 scores of 3+ versus less than 3+ was observed for stage IIIa after chemoradiotherapy. In addition, serum GP88 was significantly elevated in stage IIIb/IV NSCLC compared with control subjects (49.9 ng/mL versus 28.4 ng/mL; P < .0001). This is the first study demonstrating GP88 tissue and serum expression as a prognostic biomarker in localized and advanced disease. Future research will determine utility of monitoring GP88 and the potential of GP88 expression as a predictive marker for anti-GP88 therapeutics.

The anti-adipogenic effect of PGRN on porcine preadipocytes involves ERK1,2 mediated PPARγ phosphorylation

Recent researches indicate that PGRN is closely related to diabetes and is regarded as a novel adipokine associated with obesity development, affecting adipocyte biology. In the present study, we investigated the effects and mechanisms of PGRN on porcine preadipocytes differentiation. Porcine preadipocytes were induced to differentiation with the addition of lentivirius-expressed PGRN shRNA at the early or late stage of induction period, and in the presence or absence of recombinant PGRN protein. The effects of PGRN on adipogenic genes expression and ERK activation were investigated. At the early stage of induction, knockdown of PGRN promoted differentiation, evidenced by enhanced lipid accumulation, upregulation of adipocyte markers, as well as master adipogenic transcription factors, PPARγ and C/EBPα. While, decreasing PGRN expression at the late stage of induction (day 3) had no effect on differentiation. These results suggested that PGRN functions in the early adipogenic events. Conversely, porcine preadipocytes differentiation was impaired by MDI and recombinant PGRN protein induction, the expressions of adipocyte markers were decreased. Further studies revealed that PGRN can specifically facilitate ERK1,2 activation, and this activation can be abolished by U0126. Moreover, PPARγ phosphorylation at serine 112 site was increased by PGRN treatment, which could reduce the transcriptional activity of PPARγ. We conclude that PGRN inhibits adipogenesis in porcine preadipocytes partially through ERK activation mediated PPARγ phosphorylation.

Progranulin: a proteolytically processed protein at the crossroads of inflammation and neurodegeneration

GRN mutations cause frontotemporal lobar degeneration with TDP-43-positive inclusions. The mechanism of pathogenesis is haploinsufficiency. Recently, homozygous GRN mutations were detected in two patients with neuronal ceroid lipofuscinosis, a lysosomal storage disease. It is unknown whether the pathogenesis of these two conditions is related. Progranulin is cleaved into smaller peptides called granulins. Progranulin and granulins are attributed with roles in cancer, inflammation, and neuronal physiology. Cell surface receptors for progranulin, but not granulin peptides, have been reported. Revealing the cell surface receptors and the intracellular functions of granulins and progranulin is crucial for understanding their contributions to neurodegeneration.

GEP constitutes a negative feedback loop with MyoD and acts as a novel mediator in controlling skeletal muscle differentiation

Granulin-epithelin precursor (GEP) is an autocrine growth factor that has been implicated in embryonic development, tissue repair, tumorigenesis, and inflammation. Here we report that GEP was expressed in skeletal muscle tissue and its level was differentially altered in the course of C2C12 myoblast fusion. The GEP expression during myoblast fusion was a consequence of MyoD transcription factor binding to several E-box (CANNTG) sequences in the 5'-flanking regulatory region of GEP gene, followed by transcription. Recombinant GEP potently inhibited myotube formation from C2C12 myoblasts whereas the knockdown of endogenous of GEP via a siRNA approach accelerated the fusion of myoblasts to myotubes. Interestingly, the muscle fibers of GEP knockdown mice were larger in number but noticeably smaller in size when compared to the wild-type. Mechanistic studies revealed that during myoblast fusion, the addition of GEP led to remarkable reductions in the expressions of muscle-specific transcription factors, including MyoD. In addition, the regulation of myotube formation by GEP is mediated by the anti-myogenic factor JunB, which is upregulated following GEP stimulation. Thus, GEP growth factor, JunB, and MyoD transcription factor form a regulatory loop and act in concert in the course of myogenesis.

Progranulin (GP88) tumor tissue expression is associated with increased risk of recurrence in breast cancer patients diagnosed with estrogen receptor positive invasive ductal carcinoma

Introduction

GP88 (progranulin) has been implicated in tumorigenesis and resistance to anti-estrogen therapies for estrogen receptor positive (ER⁺) breast cancer. Previous pathological studies showed that GP88 is expressed in invasive ductal carcinoma (IDC), but not in normal mammary epithelial tissue, benign lesions or lobular carcinoma. Based on these results, the present study examines GP88 prognostic significance in association with recurrence and death risks for ER⁺ IDC patients.

Methods

Two retrospective multi-site clinical studies examined GP88 expression by immunohistochemistry (IHC) analysis of paraffin-embedded breast tumor tissue sections from ER⁺ IDC patients (lymph node positive and negative, stage 1 to 3) in correlation with patients' survival outcomes. The training study established a GP88 cut-off value associated with decreased disease-free (DFS) and overall (OS) survivals. The validation study verified the GP88 cut-off value and compared GP88 prognostic information with other prognostic factors, particularly tumor size, grade, disease stage and lymph node status in multivariate analysis.

Results

GP88 expression is associated with a statistically significant increase in recurrence risk for ER⁺ IDC patients. The training study established that GP88 3+ score was associated with decreased DFS (P = 0.0004) and OS (P = 0.0036). The independent validation study verified that GP88 3+ score was associated with a 5.9-fold higher hazard of disease recurrence and a 2.5-fold higher mortality hazard compared to patients with tumor GP88 < 3+. GP88 remained an independent risk predictor after considering age, ethnicity, nodal status, tumor size, tumor grade, disease stage, progesterone receptor expression and treatments.

Conclusions

The survival factor GP88 is a novel prognostic biomarker, predictive of recurrence risk and increased mortality for non-metastatic ER⁺ IDC patients. Of importance, our data show that GP88 continues to be a prognostic factor even after five years. These results also provide evidence that GP88 provides prognostic information independent of tumor and clinical characteristics and would support prospective study to examine whether GP88 expression could help stratify patients with ER⁺ tumors for adjuvant therapy.

Progranulin: a growth factor, a novel TNFR ligand and a drug target

Progranulin (PGRN) is abundantly expressed in epithelial cells, immune cells, neurons, and chondrocytes, and reportedly contributes to tumorigenesis. PGRN is a crucial mediator of wound healing and tissue repair. PGRN also functions as a neurotrophic factor and mutations in the PGRN gene resulting in partial loss of the PGRN protein cause frontotemporal dementia. PGRN has been found to be a novel chondrogenic growth factor and to play an important role in cartilage development and inflammatory arthritis. Although research has shown that PGRN exhibits anti-inflammatory properties, the details about the exact molecular pathway of such effects, and, in particular, the PGRN binding receptor, have not been identified so far. Recently, researchers have shown that PGRN binds to tumor necrosis factor (TNF)-receptors (TNFR), interfering with the interaction between TNFα and TNFR. They further demonstrated that mice deficient in PGRN are susceptible to collagen-induced arthritis, an experimental model of rheumatoid arthritis, and that administration of PGRN reversed the arthritic process. An engineered protein made of three PGRN fragments (Atsttrin), displayed selective TNFR binding and was more active than natural PGRN. Both PGRN and Atsttrin prevented inflammation in various arthritis mouse models and inhibited TNFα-induced intracellular signaling pathways. Thus, PGRN is a key regulator of inflammation and it may mediate its anti-inflammatory effects, at least in part, by blocking TNF binding to its receptors. As we discuss here, TNFR-based interventions may both stimulate and suppress the growth of cancer cells, and the same may be true in analogy for Atsttrin as a new player.

Upregulation of progranulin by Helicobacter pylori in human gastric epithelial cells via p38MAPK and MEK1/2 signaling pathway: role in epithelial cell proliferation and migration

Helicobacter pylori is a major human pathogen associated with gastric diseases such as chronic active gastritis, peptic ulcer, and gastric carcinoma. The growth factor progranulin (PGRN) is a secreted glycoprotein that functions as an important regulator of cell growth, migration, and transformation. We aimed to determine the molecular mechanisms by which H. pylori upregulates the expression of PGRN and the relationship between H. pylori infection and production of PGRN in controlling cell proliferation and migration. Levels of PGRN were examined in gastric tissues from patients and in vitro in gastric epithelial cells. Cell proliferation was measured by colony formation assay. Cell migration was monitored by wound healing migration assay. PGRN protein levels were increased in patients with gastritis and gastric cancer tissue. Infection of gastric epithelial cells with H. pylori significantly increased PGRN expression in a time-dependent manner. Blockade of the p38 and MEK1/2 pathway by inhibitor inhibited H. pylori-mediated PGRN upregulation. Activation of p38 and MEK1/2 pathway by H. pylori was also identified. Knockdown of PGRN attenuated the H. pylori-induced proliferative activity and migration of cancer cells. These findings suggest that the upregulation of PGRN in H. pylori-infected gastric epithelial cells may contribute to the carcinogenic process.

Increased Circulating Level of the Survival Factor GP88 (Progranulin) in the Serum of Breast Cancer Patients When Compared to Healthy Subjects

Introduction:

GP88 (PC-Cell Derived Growth Factor, progranulin) is a glycoprotein overexpressed in breast tumors and involved in their proliferation and survival. Since GP88 is secreted, an exploratory study was established to compare serum GP88 level between breast cancer patients (BC) and healthy volunteers (HV).

Methods:

An IRB approved prospective study enrolled 189 stage 1–4 BC patients and 18 HV. GP88 serum concentration was determined by immunoassay.

Results:

Serum GP88 level was 28.7 + 5.8 ng/ml in HV and increased to 40.7 + 16.0 ng/ml (P = 0.007) for stage 1–3 and 45.3 + 23.3 ng/ml (P = 0.0007) for stage 4 BC patients. There was no correlation between the GP88 level and BC characteristics such as age, race, tumor grade, ER, PR and HER-2 expression.

Conclusion:

These data suggest that serial testing of serum GP88 levels may have value as a circulating biomarker for detection, monitoring and follow up of BC.

Structure, function, and mechanism of progranulin; the brain and beyond

Mutation of human GRN, the gene encoding the secreted glycoprotein progranulin, results in a form of frontotemporal lobar degeneration that is characterized by the presence of ubiquitinated inclusions containing phosphorylated and cleaved fragments of the transactivation response element DNA-binding protein-43. This has stimulated interest in understanding the role of progranulin in the central nervous system, and in particular, how this relates to neurodegeneration. Progranulin has many roles outside the brain, including regulation of cellular proliferation, survival, and migration, in cancer, including cancers of the brain, in wound repair, and inflammation. It often acts through the extracellular signal-regulated kinase and phopshatidylinositol-3-kinases pathways. The neurobiology of progranulin has followed a similar pattern with proposed roles for progranulin (PGRN) in the central nervous system as a neuroprotective agent and in neuroinflammation. Here we review the structure, biology, and mechanism of progranulin action. By understanding PGRN in a wider context, we may be better able to delineate its roles in the normal brain and in neurodegenerative disease.

GP88 (PC-Cell Derived Growth Factor, progranulin) stimulates proliferation and confers letrozole resistance to aromatase overexpressing breast cancer cells

Background

Aromatase inhibitors (AI) that inhibit breast cancer cell growth by blocking estrogen synthesis have become the treatment of choice for post-menopausal women with estrogen receptor positive (ER⁺) breast cancer. However, some patients display de novo or acquired resistance to AI. Interactions between estrogen and growth factor signaling pathways have been identified in estrogen-responsive cells as one possible reason for acquisition of resistance. Our laboratory has characterized an autocrine growth factor overexpressed in invasive ductal carcinoma named PC-Cell Derived Growth Factor (GP88), also known as progranulin. In the present study, we investigated the role GP88 on the acquisition of resistance to letrozole in ER⁺ breast cancer cells

Methods

We used two aromatase overexpressing human breast cancer cell lines MCF-7-CA cells and AC1 cells and their letrozole resistant counterparts as study models. Effect of stimulating or inhibiting GP88 expression on proliferation, anchorage-independent growth, survival and letrozole responsiveness was examined.

Results

GP88 induced cell proliferation and conferred letrozole resistance in a time- and dose-dependent fashion. Conversely, naturally letrozole resistant breast cancer cells displayed a 10-fold increase in GP88 expression when compared to letrozole sensitive cells. GP88 overexpression, or exogenous addition blocked the inhibitory effect of letrozole on proliferation, and stimulated survival and soft agar colony formation. In letrozole resistant cells, silencing GP88 by siRNA inhibited cell proliferation and restored their sensitivity to letrozole.

Conclusion

Our findings provide information on the role of an alternate growth and survival factor on the acquisition of aromatase inhibitor resistance in ER⁺ breast cancer.

Cellular effects of progranulin in health and disease

Progranulin is a fascinating multifunctional protein, which has been implicated in cell growth, wound repair, tumorigenesis, inflammation, neurodevelopment, and more recently in neurodegeneration. The mechanism of action of this protein is still largely unknown, but the knowledge about the cellular effects on various cell types is expanding. In the current review, we will summarize what is known about the cell biology of progranulin. A better understanding of the biology of progranulin will impact diverse areas of research.

Biomarker-based dissection of neurodegenerative diseases

The diagnosis of neurodegenerative diseases within neurology and psychiatry are hampered by the difficulty in getting biopsies and thereby validating the diagnosis by pathological findings. Biomarkers for other types of disease have been readily adopted into the clinical practice where for instance troponins are standard tests when myocardial infarction is suspected. However, the use of biomarkers for neurodegeneration has not been fully incorporated into the clinical routine. With the development of cerebrospinal fluid (CSF) biomarkers that reflect pathological events within the central nervous system (CNS), important clinical diagnostic tools are becoming available. This review summarizes the most promising biomarker candidates that may be used to monitor different types of neurodegeneration and protein inclusions, as well as different types of metabolic changes, in living patients in relation to the clinical phenotype and disease progression over time. Our aim is to provide the reader with an updated lexicon on currently available biomarker candidates, how far they have come in development and how well they reflect pathogenic processes in different neurodegenerative diseases. Biomarkers for specific pathogenetic processes would also be valuable tools both to study disease pathogenesis directly in patients and to identify and monitor the effect of novel treatment strategies.

Growing a tumor stroma: a role for granulin and the bone marrow

The tumor stroma is critical in cancer progression; understanding its formation is therefore important biologically and therapeutically. In this issue of the JCI, Elkabets et al. report on the generation of data in mice that lead them to propose that certain tumors can stimulate the growth of a second otherwise quiescent or indolent tumor in the same animal by stimulating stromal formation. Granulin-expressing Sca+Kit- hematopoietic progenitor cells in the bone marrow of the tumor host were required to mediate this effect. These data shed new light on the importance of the bone marrow in tumor growth and the role of granulin in carcinogenesis.

Granulin-epithelin precursor and ATP-dependent binding cassette (ABC)B5 regulate liver cancer cell chemoresistance

BACKGROUND & AIMS

Chemotherapy is used to treat unresectable liver cancer with marginal efficacy; this might result from hepatic cancer cells with stem cell and chemoresistant features. Gene expression profiling studies have shown that hepatic cancer cells express granulin-epithelin precursor (GEP); we investigated its role in hepatic cancer stem cell functions and chemoresistance.

METHODS

The effects of GEP and drug transporter signaling on chemoresistance were investigated in hepatic cancer stem cells. We analyzed the expression patterns of 142 clinical samples from liver tumors, adjacent nontumorous liver tissue, and liver tissue from patients who did not have cancer.

RESULTS

GEP regulated the expression of the adenosine triphosphate-dependent binding cassette (ABC)B5 drug transporter in liver cancer cells. Chemoresistant cells that expressed GEP had increased levels of ABCB5; suppression of ABCB5 sensitized the cells to doxorubicin uptake and apoptosis. Most cells that expressed GEP and ABCB5 also expressed the hepatic cancer stem cell markers CD133 and EpCAM; blocking ABCB5 reduced their expression. Expression levels of GEP and ABCB5 were correlated in human liver tumor samples. ABCB5 levels were increased in liver cancer cells compared with nontumor liver tissue from patients with cirrhosis or hepatitis, or normal liver tissue. ABCB5 expression was associated with the recurrence of hepatocellular carcinoma after partial hepatectomy.

CONCLUSIONS

Expression of GEP and ABCB5 in liver cancer stem cells is associated with chemoresistance and reduced survival times of patients with hepatocellular carcinoma. Reagents designed to target these proteins might be developed as therapeutics and given in combination with chemotherapy to patients with liver cancer.