Cheryl L. Jorcyk

Breast cancer cells stimulate neutrophils to produce oncostatin M: potential implications for tumor progression.

Tumor-associated and tumor-infiltrating neutrophils (TAN) and macrophages (TAM) can account for as much as 50% of the total tumor mass in invasive breast carcinomas. It is thought that tumors secrete factors that elicit a wound-repair response from TAMs and TANs and that this response inadvertently stimulates tumor progression. Oncostatin M is a pleiotropic cytokine belonging to the interleukin-6 family that is expressed by several cell types including activated human T lymphocytes, macrophages, and neutrophils. Whereas oncostatin M can inhibit the proliferation of breast cancer cells in vitro, recent studies suggest that oncostatin M may promote tumor progression by enhancing angiogenesis and metastasis. In addition, neutrophils can be stimulated to synthesize and rapidly release large quantities of oncostatin M. In this article, we show that human neutrophils secrete oncostatin M when cocultured with MDA-MB-231 and T47D human breast cancer cells. Neutrophils isolated from whole blood or breast cancer cells alone express little oncostatin M by immunocytochemistry and ELISA, but neutrophils express and release high levels of oncostatin M when they are cocultured with breast cancer cells. In addition, we show that granulocyte-macrophage colony-stimulating factor produced by breast cancer cells and cell-cell contact are both necessary for the release of oncostatin M from neutrophils. Importantly, neutrophil-derived oncostatin M induces vascular endothelial growth factor from breast cancer cells in coculture and increases breast cancer cell detachment and invasive capacity, suggesting that neutrophils and oncostatin M may promote tumor progression in vivo.

The C3(1)/SV40 T-antigen transgenic mouse model of mammary cancer: ductal epithelial cell targeting with multistage progression to carcinoma.

The 5′ flanking region of the C3(1) component of the rat prostate steroid binding protein (PSBP) has been used to successfully target the expression of the SV40 large T-antigen (Tag) to the epithelium of both the mammary and prostate glands resulting in models of mammary and prostate cancers which histologically resemble the human diseases. Atypia of the mammary ductal epithelium develops at about 8 weeks of age, progressing to mammary intraepithelial neoplasia (resembling human ductal carcinoma in situ [DCIS]) at about 12 weeks of age with the development of invasive carcinomas at about 16 weeks of age in 100% of female mice. The carcinomas share features to what has been classified in human breast cancer as infiltrating ductal carcinomas. All FVB/N female mice carrying the transgene develop mammary cancer with about a 15% incidence of lung metastases. Approximately 10% of older male mice develop anaplastic mammary carcinomas. Unlike many other transgenic models in which hormones and pregnancy are used to induce a mammary phenotype, C3(1)/Tag mice develop mammary tumors in the mammary epithelium of virgin animals without hormone supplementation or pregnancy. Although mammary tumor development appears hormone-responsive at early stages, invasive carcinomas are hormone-independent, which corresponds to the loss of estrogen receptor-α expression during tumor progression. Molecular and biologic factors related to mammary tumor progression can be studied in this model since lesions evolve over a predictable time course. Genomic alterations have been identified during tumor progression, including an amplification of the distal portion of chromosome 6 containing ki-ras and loss of heterozygosity (LOH) in other chromosomal regions. We have demonstrated that stage specific alterations in the expression of genes which are critical regulators of the cell cycle and apoptosis are functionally important in vivo. C3(1)/Tag mice appear useful for testing particular therapies since growth of the mammary tumors can be reduced using chemopreventive agents, cytokines, and an anti-angiogenesis agent.

Bleach Gel: A Simple Agarose Gel for Analyzing RNA Quality

RNA‐based applications requiring high‐quality, non‐degraded RNA are a foundational element of many research studies. As such, it is paramount that the integrity of experimental RNA is validated prior to cDNA synthesis or other downstream applications. In the absence of expensive equipment such as microfluidic electrophoretic devices, and as an alternative to the costly and time‐consuming standard formaldehyde gel, RNA quality can be quickly analyzed by adding small amounts of commercial bleach to TAE buffer‐based agarose gels prior to electrophoresis. In the presence of low concentrations of bleach, the secondary structure of RNA is denatured and potential contaminating RNases are destroyed. Because of this, the ‘bleach gel’ is a functional approach that addresses the need for an inexpensive and safe way to evaluate RNA integrity and will improve the ability of researchers to rapidly analyze RNA quality.

Clinical Significance of Interleukin (IL)-6 in Cancer Metastasis to Bone: Potential of Anti-IL-6 Therapies

Metastatic events to the bone occur frequently in numerous cancer types such as breast, prostate, lung, and renal carcinomas, melanoma, neuroblastoma, and multiple myeloma. Accumulating evidence suggests that the inflammatory cytokine interleukin (IL)-6 is frequently upregulated and is implicated in the ability of cancer cells to metastasize to bone. IL-6 is able to activate various cell signaling cascades that include the STAT (signal transducer and activator of transcription) pathway, the PI3K (phosphatidylinositol-3 kinase) pathway, and the MAPK (mitogen-activated protein kinase) pathway. Activation of these pathways may explain the ability of IL-6 to mediate various aspects of normal and pathogenic bone remodeling, inflammation, cell survival, proliferation, and pro-tumorigenic effects. This review article will discuss the role of IL-6: 1) in bone metabolism, 2) in cancer metastasis to bone, 3) in cancer prognosis, and 4) as potential therapies for metastatic bone cancer.

Suppression of mammary carcinoma growth in vitro and in vivo by inducible expression of the Cdk inhibitor p21

Mammary carcinomas that develop in C3(1)/SV40 T-antigen (TAg) transgenic mice have lost the p53-mediated induction of p21, leading to increased cellular proliferation and significant elevations of cyclins and Cdks. To test whether p21 could serve as a target for anticancer therapy for this mammary cancer model, a retroviral delivery system for the inducible expression of p21 was developed. We demonstrate that overexpression of p21 in C3(1)/TAg mammary tumor cells using the retroviral inducible p21 expression system results in increased apoptosis, reduced cell proliferation in vitro and reduced tumor growth in vivo associated with reduced expression of cyclins D1 and E, and Cdks 2, 4, and 6. Reciprocal changes in the expression of p21 and p27Kip1, another cell-cycle regulator, were also observed. Because reduced p21 expression occurs frequently in human breast cancer, restoration of the Cdk inhibitor p21 by gene therapy approaches may provide a method for inhibiting mammary tumor progression. Cancer Gene Therapy (2001) 8, 23–35

Complete Regression of Established Spontaneous Mammary Carcinoma and the Therapeutic Prevention of Genetically Programmed Neoplastic Transition by IL-12/Pulse IL-2: Induction of Local T Cell Infiltration, Fas/Fas Ligand Gene Expression, and Mammary Epithelial Apoptosis

Using a novel transgenic mouse model of spontaneous mammary carcinoma, we show here that the IL-12/pulse IL-2 combination can induce rapid and complete regression of well-established autochthonous tumor in a setting where the host immune system has been conditioned by the full dynamic process of neoplastic progression and tumorigenesis. Further, this regimen inhibits neovascularization of established mammary tumors, and does so in conjunction with potent local induction of genes encoding the IFN-γ- and TNF-α-inducible antiangiogenic chemokines IFN-inducible protein 10 and monokine induced by IFN-γ. In contrast to untreated juvenile C3(1)TAg mice in which histologically normal mammary epithelium predictably undergoes progressive hyperplasia, atypical changes, and ultimately transition to overt carcinoma, the current studies also demonstrate a unique preventative therapeutic role for IL-12/pulse IL-2. In juvenile mice, early administration of IL-12/pulse IL-2 markedly limits the expected genetically programmed neoplastic transition within the mammary epithelium and does so in conjunction with enhancement of constitutive Fas and pronounced induction of local Fas ligand gene expression, T cell infiltration, and induction of apoptosis within the mammary epithelium. These events occur in the absence of a durable Ag-specific memory response. Thus, this novel model system demonstrates that the potent therapeutic activity of the IL-12/pulse IL-2 combination rapidly engages potent apoptotic and antiangiogenic mechanisms that remain active during the delivery of IL-12/pulse IL-2. The results also demonstrate that these mechanisms are active against established tumor as well as developing preneoplastic lesions.

The C3(1)/SV40 T Antigen Transgenic Mouse Model of Prostate and Mammary Cancer*

BACKGROUND Prostate and mammary cancers are the most common malignant diseases in the Western world and have increased dramatically during the past decade (23). Both cancers are now the second leading cause of cancer deaths in men and women in the United States and their incidences continue to rise. According to recent estimates (23), approximately 317,000 men will be diagnosed with prostate cancer and 41,000 will die of the disease in the United States this year. For women, the cumulative lifetime risk of developing breast cancer is 12%, whereas the lifetime mortality risk has been estimated to be 3.5% (1 1). Despite this serious situation, the etiologies and risk factors for cancer in these organs have remained largely unknown. Some hereditary factors appear to be involved, but other unknown genetic alterations and environmental and life-style factors appear to be the most important causative factors. Although transgenic models for mammary cancer have been developed, no transgenic animal for prostate cancer has been available until recently. Several useful animal models for prostate cancer have been developed using chemical carcinogens (2, 30), but these models are labor intensive and generally require tumor promotion with pharmacologic doses of steroid hormone. Therefore, we developed a transgenic mouse model for prostate cancer by targeting the expression of the simian virus 40 (SV40) early region to the mouse prostate epithelium using the 5‘ flanking region of the rat C3(1) gene, a gene which is very highly expressed in the rat ventral prostate (20). This was the first reported transgenic model for prostate cancer. Other transgenic mouse models for prostate cancer have also been developed (Table I; see Ref. #7 for review). In addition to the development of prostate cancers, aged male C3( l)/TAg transgenic mice develop tumors of the urethral, bulbourethral, and salivary ‘glands, whereas 100% of female transgenic mice develop mammary adenocarcinomas.

Amplification of Ki-ras and elevation of MAP kinase activity during mammary tumor progression in C3(1)/SV40 Tag transgenic mice

We have previously documented that transgenic mice expressing SV40 Tag regulated by the rat prostatic steroid-binding protein C3(1) 5′-flanking region display multistage mammary tumorigenesis. To delineate genetic changes associated with mammary tumor progression, comparative genomic hybridization (CGH) was performed. CGH revealed a consistent gain of the telomeric region of chromosome 6. This region contains the Ki-ras proto-oncogene. Analyses of genomic DNA by Southern blot demonstrated up to 40-fold amplification of the Ki-ras gene. Ki-ras amplification was detected in 12, 46 and 68% of tumors from 4, 5 and 6 month old mice, respectively, whereas no amplifications were found in any preneoplastic mammary tissues. Tumors bearing Ki-ras gene amplification exhibited high levels of Ki-ras RNA and protein. The over-expressed Ki-Ras protein in these tumors appeared functionally active as indicated by the elevated MAP kinase activity. These data demonstrate that while Ki-ras amplification might not be an early event, there is a strong association between Ki-ras amplification and over-expression and mammary tumor progression in this model. This study also shows that CGH is a powerful and useful technique for identifying chromosomal copy number changes during tumor progression, and that this model may provide a predictable in vivo system for studying gene amplification.

Oncostatin M Promotes Mammary Tumor Metastasis to Bone and Osteolytic Bone Degradation

Oncostatin M (OSM) is an interleukin-6 (IL-6) family cytokine that has been implicated in a number of biological processes including inflammation, hematopoiesis, immune responses, development, and bone homeostasis. Recent evidence suggests that OSM may promote breast tumor invasion and metastasis. We investigated the role of OSM in the formation of bone metastases in vivo using the 4T1.2 mouse mammary tumor model in which OSM expression was knocked down using shRNA (4T1.2-OSM). 4T1.2-OSM cells were injected orthotopically into Balb/c mice, resulting in a greater than 97% decrease in spontaneous metastasis to bone compared to control cells. Intratibial injection of these same 4T1.2-OSM cells also dramatically reduced the osteolytic destruction of trabecular bone volume compared to control cells. Furthermore, in a tumor resection model, mice bearing 4T1.2-OSM tumors showed an increase in survival by a median of 10 days. To investigate the specific cellular mechanisms important for OSM-induced osteolytic metastasis to bone, an in vitro model was developed using the RAW 264.7 preosteoclast cell line co-cultured with 4T1.2 mouse mammary tumor cells. Treatment of co-cultures with OSM resulted in a 3-fold induction of osteoclastogenesis using the TRAP assay. We identified several tumor cell-induced factors including vascular endothelial growth factor, IL-6, and a previously uncharacterized OSM-regulated bone metastasis factor, amphiregulin (AREG), which increased osteoclast differentiation by 4.5-fold. In addition, pretreatment of co-cultures with an anti-AREG neutralizing antibody completely reversed OSM-induced osteoclastogenesis. Our results suggest that one mechanism for OSM-induced osteoclast differentiation is via an AREG autocrine loop, resulting in decreased osteoprotegerin secretion by the 4T1.2 cells. These data provide evidence that OSM might be an important therapeutic target for the prevention of breast cancer metastasis to bone.

Development and Characterization of a Progressive Series of Mammary Adenocarcinoma Cell Lines Derived from the C3(1)/SV40 Large T-antigen Transgenic Mouse Model

We have developed four new mammary adenocarcinoma cell lines from the C3(1)/SV40 Large T-antigen (Tag) transgenic mouse model: M28N2 and M27H4 (weakly tumorigenic), M6 (carcinoma), and M6C (metastatic). The C3(1) promoter directs Tag expression to the mammary epithelium and 100% of female C3(1)/Tag transgenic mice develop mammary adenocarcinoma in a predictable and progressive manner. The cell lines we developed from this model are demonstrated to be of epithelial origin and display growth rates, both in vitro and following subcutaneous inoculation into nude mice, that are consistent with their representative stage of tumor progression. The more tumorigenic cell lines, M6 and M6C, both express the sodium/iodide symporter, a mammary carcinoma cell marker with potential therapeutic and diagnostic applications. All of the cell lines express estrogen receptor (ER) α and ER β mRNA, and Western blot analysis demonstrates that the ER α protein is down-regulated in the M6 and M6C cell lines. M28N2 cells also express progesterone receptor (PgR), which is very unusual in a mouse mammary carcinoma cell line. In addition, all of the cell lines display growth inhibition when plated in media supplemented with charcoal-stripped fetal calf serum (CS FBS). When CS FBS is supplemented with β estradiol or the progestin MPA, no significant difference in growth rates is observed relative to growth in CS FBS. The development and characterization of a progressive series of new mammary carcinoma cell lines will aid in the study of mammary carcinoma progression both in vitro and in vivo.