Human tumors instigate granulin-expressing hematopoietic cells that promote malignancy by activating stromal fibroblasts in mice

The biomechanical properties of 3d extracellular matrices and embedded cells regulate the invasiveness of cancer cells

The malignancy of tumors depends on the biomechanical properties of cancer cells and their microenvironment, which enable cancer cells to migrate through the connective tissue, transmigrate through basement membranes and endothelial monolayers and form metastases in targeted organs. The current focus of cancer research is still based on biological capabilities such as molecular genetics and gene signaling, but these approaches ignore the mechanical nature of the invasion process of cancer cells. This review will focus on how structural, biochemical and mechanical properties of extracellular matrices (ECMs), and adjacent cells regulate the invasiveness of cancer cells. In addition, it presents how cancer cells create their own microenvironment by restructuring of the ECM and by interaction with stromal cells, which then further contribute to the progression of cancer disease. Finally, this review will point out that mechanical properties are a critical determinant for the efficiency of cancer cell invasion and the progression of cancer which might affect the future development of new cancer treatments.

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.

Abnormal tumor vasculatures and bone marrow-derived pro-angiogenic cells in cancer

Tumor-derived factors affect the stroma of cancer tissue by activating pro-angiogenic signals. One of the key components of this response is the mobilization of the pro-angiogenic cells from bone marrow (BM), which contribute to the development of abnormal tumor vasculature. Evidence is accumulating that the pro-angiogenic cells derived from BM are involved in the physiological processes of tissue repair and wound healing. However, vascular structure in cancer tissue is impaired, resulting in the formation of chaotic neo-vessels and hypoxic microenvironments. Ultimately, these structural and functional abnormalities result in the limited delivery of chemotherapeutic agents and create regions of metabolic derangement, both of which enhance resistance to chemotherapy. In spite of recent advances in targeted therapy using anti-vascular agents, clinical results from studies using individual agents have unsatisfactory, necessitating the combinatorial use of anti-cancer drugs and a targeting agent. We suggest the possibility of a new therapeutic approach in which aberrant tumor vessels are normalized by BM-derived pro-angiogenic cells, and the delivery of anti-cancer drugs is maximized. In this review, we focus on the current understanding of the structure and function of tumor vessels, and an alternative approach to the repair of abnormal tumor vasculature by the use of BM-derived pro-angiogenic cells. This approach may improve both the delivery and the efficacy of anti-cancer drugs by restoring aberrant tumor vascularization and hypoxia.

Dermal mast cells affect the development of sunlight-induced skin tumours

Ultraviolet (UV) radiation contained in sunlight is considered a major risk in the induction of skin cancer. While mast cells are best known for their role in allergic responses, they have also been shown to play a crucial role in suppressing the anti-tumour immune response following UV exposure. Evidence is now emerging that UV may also trigger mast cell release of cutaneous tissue remodelling and pro-angiogenic factors. In this review, we will focus on the cellular and molecular mechanisms by which UV recruits and then activates mast cells to initiate and promote skin cancer development.

Progranulin stimulated by LPA promotes the migration of aggressive breast cancer cells

Activator and inhibitor roles for the 88-kDa-secreted glycoprotein progranulin (PGRN) have been demonstrated in ovarian cancer cells. Here, we investigated the effects of PGRN in breast cancer migration. Testing MCF7, MDA-MB-453, and MDA-MB-231 human breast cancer cells and the MCF10A breast epithelial cell line, we demonstrate that LPA-induced PGRN stimulation led to a significant increase in cell invasion of MDA-MB-453 and MDA-MB-231 cells only (p<0.05). Moreover, incubation with an anti-PGRN antibody, an inhibitor of the ERK pathway (PD98059) or both in combination inhibited the ability of MDA-MB-231 cells to invade. Furthermore, the expression of focal adhesion kinases promoted by LPA-induced PGRN was also inhibited by PD98059 alone or in combination with an anti-PGRN antibody (p<0.05). Taken together, these results suggest that the LPA activation of PGRN involving the ERK pathway is critical to promote MDA-MB-231 breast cancer cell invasion.

Progranulin overexpression predicts overall survival in patients with glioblastoma

Despite multimodal treatment, patients with astrocytoma still face a poor survival, and identification of valuable prognostic factors is crucial to yield effective individual therapy strategies. The aim of this study was to investigate progranulin (PGRN) expression in astrocytomas and explore its association with tumor grade and overall patient survival by scoring the PGRN immunoreactivity of both tumor cells and blood vessels. About 210 astrocytoma samples with different WHO grades and 14 normal brain tissues were studied by immunohistochemistry for PGRN. Semi-quantitative RT-PCR and Western blot were carried out to confirm its expression in 35 tumor specimens. Serum levels of PGRN in glioblastoma were examined by enzyme immunometric assay. PGRN expression was almost undetectable in the normal brain tissues by immunohistochemistry but increased in both astrocytoma cells and tumor blood vessels with pathological grading. Sera in glioblastoma were significantly higher than in healthy control. In grade II astrocytoma, strong vascular PGRN expression was closely related to tumor recurrence. In glioblastoma, high total PGRN expression, strong vascular PGRN expression, and strong tumor cellular PGRN expression all correlated with decreased patient survival in univariate analysis. However, only total PGRN expression as well as vascular PGRN expression status was independently associated with patient's survival in the multivariate analysis. These results suggest that PGRN, involved in astrocytoma progression, may serve as a prognostic biomarker for glioblastoma.

Lineage(-)Sca1+c-Kit(-)CD25+ cells are IL-33-responsive type 2 innate cells in the mouse bone marrow

IL-33 promotes type 2 immune responses, both protective and pathogenic. Recently, targets of IL-33, including several newly discovered type 2 innate cells, have been characterized in the periphery. In this study, we report that bone marrow cells from wild-type C57BL/6 mice responded with IL-5 and IL-13 production when cultured with IL-33. IL-33 cultures of bone marrow cells from Rag1 KO and Kit(W-sh/W-sh) mice also responded similarly; hence, eliminating the possible contributions of T, B, and mast cells. Rather, intracellular staining revealed that the IL-5- and IL-13-positive cells display a marker profile consistent with the Lineage(-)Sca-1(+)c-Kit(-)CD25(+) (LSK(-)CD25(+)) cells, a bone marrow cell population of previously unknown function. Freshly isolated LSK(-)CD25(+) cells uniformly express ST2, the IL-33 receptor. In addition, culture of sorted LSK(-)CD25(+) cells showed that they indeed produce IL-5 and IL-13 when cultured with IL-33 plus IL-2 and IL-33 plus IL-7. Furthermore, i.p. injections of IL-33 or IL-25 into mice induced LSK(-)CD25(+) cells to expand, in both size and frequency, and to upregulate ST2 and α(4)β(7) integrin, a mucosal homing marker. Thus, we identify the enigmatic bone marrow LSK(-)CD25(+) cells as IL-33 responsive, both in vitro and in vivo, with attributes similar to other type 2 innate cells described in peripheral tissues.

The microenvironment in breast cancer progression: biology and implications for treatment

Breast cancer comprises a heterogeneous group of malignancies derived from the ductal epithelium. The microenvironment of these cancers is now recognized as a critical participant in tumor progression and therapeutic responses. Recent data demonstrate significant gene expression and epigenetic alterations in cells composing the microenvironment during disease progression, which can be explored as biomarkers and targets for therapy. Indeed, gene expression signatures derived from tumor stroma have been linked to clinical outcomes. There is increasing interest in translating our current understanding of the tumor microenvironment to the development of novel therapies.

The Human Protein Atlas as a proteomic resource for biomarker discovery

The analysis of tissue-specific expression at both the gene and protein levels is vital for understanding human biology and disease. Antibody-based proteomics provides a strategy for the systematic generation of antibodies against all human proteins to combine with protein profiling in tissues and cells using tissue microarrays, immunohistochemistry and immunofluorescence. The Human Protein Atlas project was launched in 2003 with the aim of creating a map of protein expression patterns in normal cells, tissues and cancer. At present, 11,200 unique proteins corresponding to over 50% of all human protein-encoding genes have been analysed. All protein expression data, including underlying high-resolution images, are published on the free and publically available Human Protein Atlas portal (http://www.proteinatlas.org). This database provides an important source of information for numerous biomedical research projects, including biomarker discovery efforts. Moreover, the global analysis of how our genome is expressed at the protein level has provided basic knowledge on the ubiquitous expression of a large proportion of our proteins and revealed the paucity of cell- and tissue-type-specific proteins.

Mesenchymal stem cells promote formation of colorectal tumors in mice

BACKGROUND & AIMS

Tumor-initiating cells are a subset of tumor cells with the ability to form new tumors; however, they account for less than 0.001% of the cells in colorectal or other types of tumors. Mesenchymal stem cells (MSCs) integrate into the colorectal tumor stroma; we investigated their involvement in tumor initiation.

METHODS

Human colorectal cancer cells, MSCs, and a mixture of both cell types were injected subcutaneously into immunodeficient mice. We compared the ability of each injection to form tumors and investigated the signaling pathway involved in tumor initiation.

RESULTS

A small number (≤ 10) of unsorted, CD133⁻, CD166⁻, epithelial cell adhesion molecule⁻(EpCAM⁻), or CD133⁻/CD166⁻/EpCAM⁻ colorectal cancer cells, when mixed with otherwise nontumorigenic MSCs, formed tumors in mice. Secretion of interleukin (IL)-6 by MSCs increased the expression of CD133 and activation of Janus kinase 2-signal transducer and activator of transcription 3 (STAT3) in the cancer cells, and promoted sphere and tumor formation. An antibody against IL-6 or lentiviral-mediated transduction of an interfering RNA against IL-6 in MSCs or STAT3 in cancer cells prevented the ability of MSCs to promote sphere formation and tumor initiation.

CONCLUSIONS

IL-6, secreted by MSCs, signals through STAT3 to increase the numbers of colorectal tumor-initiating cells and promote tumor formation. Reagents developed to disrupt this process might be developed to treat patients with colorectal cancer.

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.

Waking up dormant tumors

As appreciation grows for the contribution of the tumor microenvironment to the progression of cancer, new evidence accumulates to support that the participation of stromal cells can extend beyond the local environment. Recently, Elkabets and colleagues demonstrated a systemic interaction between cancer cells and distant bone marrow cells to support the growth of otherwise indolent tumor cells at a secondary site, raising thought-provoking questions regarding the involvement of stromal cells in maintaining metastatic dormancy.

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.

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.