Ken Tawara

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.

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.

Oncostatin M binds to extracellular matrix in a bioactive conformation: implications for inflammation and metastasis.

Oncostatin M (OSM) is an interleukin-6-like inflammatory cytokine reported to play a role in a number of pathological processes including cancer. Full-length OSM is expressed as a 26 kDa protein that can be proteolytically processed into 24 kDa and 22 kDa forms via removal of C-terminal peptides. In this study, we examined both the ability of OSM to bind to the extracellular matrix (ECM) and the activity of immobilized OSM on human breast carcinoma cells. OSM was observed to bind to ECM proteins collagen types I and XI, laminin, and fibronectin in a pH-dependent fashion, suggesting a role for electrostatic bonds that involves charged amino acids of both the ECM and OSM. The C-terminal extensions of 24 kDa and 26 kDa OSM, which contains six and thirteen basic amino acids, respectively, enhanced electrostatic binding to ECM at pH 6.5-7.5 when compared to 22 kDa OSM. The highest levels of OSM binding to ECM, though, were observed at acidic pH 5.5, where all forms of OSM bound to ECM proteins to a similar extent. This indicates additional electrostatic binding properties independent of the OSM C-terminal extensions. The reducing agent dithiothreitol also inhibited the binding of OSM to ECM suggesting a role for disulfide bonds in OSM immobilization. OSM immobilized to ECM was protected from cleavage by tumor-associated proteases and maintained activity following incubation at acidic pH for extended periods of time. Importantly, immobilized OSM remained biologically active and was able to induce and sustain the phosphorylation of STAT3 in T47D and ZR-75-1 human breast cancer cells over prolonged periods, as well as increase levels of STAT1 and STAT3 protein expression. Immobilized OSM also induced epithelial-mesenchymal transition-associated morphological changes in T47D cells. Taken together, these data indicate that OSM binds to ECM in a bioactive state that may have important implications for the development of chronic inflammation and tumor metastasis.

Novel Mouse Mammary Cell Lines for in vivo Bioluminescence Imaging (BLI) of Bone Metastasis

BackgroundTumor cell lines that can be tracked in vivo during tumorigenesis and metastasis provide vital tools for studying the specific cellular mechanisms that mediate these processes as well as investigating therapeutic targets to inhibit them. The goal of this study was to engineer imageable mouse mammary tumor cell lines with discrete propensities to metastasize to bone in vivo. Two novel luciferase expressing cell lines were developed and characterized for use in the study of breast cancer metastasis to bone in a syngeneic mouse model.ResultsThe 4 T1.2 luc3 and 66c14 luc2 cell lines were shown to have high levels of bioluminescence intensity in vitro and in vivo after orthotopic injection into mouse mammary fat pads. The 4 T1.2 luc3 cell line was found to closely model the sites of metastases seen in human patients including lung, liver, and bone. Specifically, 4 T1.2 luc3 cells demonstrated a high incidence of metastasis to spine, with an ex-vivo BLI intensity three orders of magnitude above the commercially available 4 T1 luc2 cells. 66c14 luc2 cells also demonstrated metastasis to spine, which was lower than that of 4 T1.2 luc3 cells but higher than 4 T1 luc2 cells, in addition to previously unreported metastases in the liver. High osteolytic activity of the 4 T1.2 luc3 cells in vivo in the bone microenvironment was also detected.ConclusionsThe engineered 4 T1.2 luc3 and 66c14 luc2 cell lines described in this study are valuable tools for studying the cellular events moderating the metastasis of breast tumor cells to bone.

Endoplasmic Reticulum Stress and Unfolded Protein Response in Cartilage Pathophysiology; Contributing Factors to Apoptosis and Osteoarthritis

Chondrocytes of the growth plate undergo apoptosis during the process of endochondral ossification, as well as during the progression of osteoarthritis. Although the regulation of this process is not completely understood, alterations in the precisely orchestrated programmed cell death during development can have catastrophic results, as exemplified by several chondrodystrophies which are frequently accompanied by early onset osteoarthritis. Understanding the mechanisms that underlie chondrocyte apoptosis during endochondral ossification in the growth plate has the potential to impact the development of therapeutic applications for chondrodystrophies and associated early onset osteoarthritis. In recent years, several chondrodysplasias and collagenopathies have been recognized as protein-folding diseases that lead to endoplasmic reticulum stress, endoplasmic reticulum associated degradation, and the unfolded protein response. Under conditions of prolonged endoplasmic reticulum stress in which the protein folding load outweighs the folding capacity of the endoplasmic reticulum, cellular dysfunction and death often occur. However, unfolded protein response (UPR) signaling is also required for the normal maturation of chondrocytes and osteoblasts. Understanding how UPR signaling may contribute to cartilage pathophysiology is an essential step toward therapeutic modulation of skeletal disorders that lead to osteoarthritis.

Stüve-Wiedemann syndrome: LIFR and associated cytokines in clinical course and etiology

Stüve-Wiedemann syndrome (STWS; OMIM #610559) is a rare bent-bone dysplasia that includes radiologic bone anomalies, respiratory distress, feeding difficulties, and hyperthermic episodes. STWS usually results in infant mortality, yet some STWS patients survive into and, in some cases, beyond adolescence. STWS is caused by a mutation in the leukemia inhibitory factor receptor (LIFR) gene, which is inherited in an autosomally recessive pattern. Most LIFR mutations resulting in STWS are null mutations which cause instability of the mRNA and prevent the formation of LIFR, impairing the signaling pathway. LIFR signaling usually follows the JAK/STAT3 pathway, and is initiated by several interleukin-6-type cytokines. STWS is managed on a symptomatic basis since there is no treatment currently available.

The Effect of OSM on MC3T3-E1 Osteoblastic Cells in Simulated Microgravity with Radiation.

Bone deterioration is a challenge in long-term spaceflight with significant connections to patients experiencing disuse bone loss. Prolonged unloading and radiation exposure, defining characteristics of space travel, have both been associated with changes in inflammatory signaling via IL-6 class cytokines in bone. While there is also evidence for perturbed IL-6 class signaling in spaceflight, there has been scant examination of the connections between microgravity, radiation, and inflammatory stimuli in bone. Our lab and others have shown that the IL-6 class cytokine oncostatin M (OSM) is an important regulator of bone remodeling. We hypothesize that simulated microgravity alters osteoblast OSM signaling, contributing to the decoupling of osteolysis and osteogenesis in bone homeostasis. To test this hypothesis, we induced OSM signaling in murine MC3T3-E1 pre-osteoblast cells cultured in modeled microgravity using a rotating wall vessel bioreactor with and without exposure to radiation typical of a solar particle event. We measured effects on inflammatory signaling, osteoblast activity, and mineralization. Results indicated time dependent interactions among all conditions in the regulation of IL-6 production. Furthermore, OSM induced the transcription of OSM receptor ß, IL 6 receptor α subunits, collagen α1(I), osteocalcin, sclerostin, RANKL, and osteoprotegerin. Measurements of osteoid mineralization suggest that the spatial organization of the osteoblast environment is an important consideration in understanding bone formation. Taken together, these results support a role for altered OSM signaling in the mechanism of microgravity-induced bone loss.

OSM potentiates preintravasation events, increases CTC counts, and promotes breast cancer metastasis to the lung

BackgroundSystemic and chronic inflammatory conditions in patients with breast cancer have been associated with reduced patient survival and increased breast cancer aggressiveness. This paper characterizes the role of an inflammatory cytokine, oncostatin M (OSM), in the preintravasation aspects of breast cancer metastasis.MethodsOSM expression levels in human breast cancer tissue samples were assessed using tissue microarrays, and expression patterns based on clinical stage were assessed. To determine the in vivo role of OSM in breast cancer metastasis to the lung, we used three orthotopic breast cancer mouse models, including a syngeneic 4T1.2 mouse mammary cancer model, the MDA-MB-231 human breast cancer xenograft model, and an OSM-knockout (OSM-KO) mouse model. Progression of metastatic disease was tracked by magnetic resonance imaging and bioluminescence imaging. Endpoint analysis included circulating tumor cell (CTC) counts, lung metastatic burden analysis by qPCR, and ex vivo bioluminescence imaging.ResultsUsing tissue microarrays, we found that tumor cell OSM was expressed at the highest levels in ductal carcinoma in situ. This finding suggests that OSM may function during the earlier steps of breast cancer metastasis. In mice bearing MDA-MB-231-Luc2 xenograft tumors, peritumoral injection of recombinant human OSM not only increased metastases to the lung and decreased survival but also increased CTC numbers. To our knowledge, this is the first time that a gp130 family inflammatory cytokine has been shown to directly affect CTC numbers. Using a 4T1.2 syngeneic mouse model of breast cancer, we found that mice bearing 4T1.2-shOSM tumors with knocked down tumor expression of OSM had reduced CTCs, decreased lung metastatic burden, and increased survival compared with mice bearing control tumors. CTC numbers were further reduced in OSM-KO mice bearing the same tumors, demonstrating the importance of both paracrine- and autocrine-produced OSM in this process. In vitro studies further supported the hypothesis that OSM promotes preintravasation aspects of cancer metastasis, because OSM induced both 4T1.2 tumor cell detachment and migration.ConclusionsCollectively, our findings suggest that OSM plays a crucial role in the early steps of metastatic breast cancer progression, resulting in increased CTCs and lung metastases as well as reduced survival. Therefore, early therapeutic inhibition of OSM in patients with breast cancer may prevent breast cancer metastasis.

Abstract 2276: Oncostatin M promotes breast cancer metastasis to lung by affecting initial stages of metastasis

Proceedings: AACR 106th Annual Meeting 2015; April 18-22, 2015; Philadelphia, PA Recent studies suggest that cancer cells destined to establish metastatic lesions may shed early during tumor development, potentially even from carcinoma in situ. Furthermore, these cells may disseminate and lay dormant in a metastatic microenvironment (MME) for years before macrometastases are detectable. While inflammatory cytokines are known to be important in promoting breast cancer metastasis, their effect on tumor cell dissemination needs to be clarified. In this study, we investigate the effect of the interleukin-6-related, inflammatory cytokine oncostatin M (OSM) on early stages of breast cancer metastasis. First, we establish the expression pattern of OSM in human breast tissue using tissue microarrays. OSM is expressed in epithelial cells at higher levels in invasive ductal carcinoma (IDC) than in adjacent normal breast tissue, but is expressed at highest levels in ductal carcinoma in situ (DCIS). This suggests that autocrine-produced OSM may be important in breast tumor invasion and in the promotion of initial steps of metastasis. OSM increases early stage metastatic potential in vitro in aggressive 4T1.2 triple negative breast cancer cells (TNBCs) by inducing tumor cell detachment and migration. These findings are corroborated by in vivo studies using an orthotopic 4T1.2 mouse model of breast cancer. Reduced OSM expression in 4T1.2 (4T1.2-shOSM) cells is sufficient to inhibit the progression and the final number and volume of metastases in the lung, as well as circulating tumor cell (CTC) numbers in Balb/c mice. The number of CTCs is further reduced in a Balb/c OSM knockout background, demonstrating the importance of both paracrine- and autocrine-produced OSM in this process. Furthermore, orthotopic injection of 4T1.2-shOSM cells increases animal survival post-primary tumor resection, while bypassing the early stages of metastasis by injecting cells directly into the systemic circulation does not. As expected, in an orthotopic xenograft MDA-MB-231 human breast cancer mouse model, peri-tumoral injection of recombinant OSM increases the number of CTCs as well as spontaneous metastasis to lung. Taken together, these results suggest that suppression of OSM levels in the tumor microenvironment could be a highly effective therapeutic strategy for halting breast cancer metastasis to lung. Citation Format: Ken Tawara, Celeste Bolin, Jordan Koncinsky, Cheryl L. Jorcyk. Oncostatin M promotes breast cancer metastasis to lung by affecting initial stages of metastasis. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2276. doi:10.1158/1538-7445.AM2015-2276

Abstract 4183: Differential expression of VEGF in breast cancer cells induced by gp130 cytokines

Glycoprotein 130 (gp130) is a glycosylated type 1 membrane protein and functions as a cytokine receptor modulating activity of the interleukin-6 (IL-6) family cytokines, which include IL-6, IL-11, IL-27, oncostatin M (OSM), leukemia inhibitory factor (LIF), ciliary neurotrophic factor (CNTF), cardiotrophin 1 (CT-1), cardiotrophin-like cytokine (CLC), and neuropoietin (NP). This study was designed to determine differential expression of VEGF in breast cancer cells by IL-6 family cytokines, and to elucidate the molecular mechanisms and signaling pathways involved in cytokine-mediated VEGF induction. Triple negative breast cancer (TNBC) MDA-MB-231 and estrogen receptor positive/progesterone receptor positive/Her2 negative (ER+/PR+/Her2-) T47D cells were treated with three cytokines (25 ng/mL), OSM, IL-6, and LIF, and analyzed. Our results showed that all three cytokines increased levels of HIF1α by Western blot analysis. OSM lead to a greater production of VEGF compared to IL-6 and LIF, as measured by enzyme-linked immunosorbent assay (ELISA) and as seen by luciferase reporter assay. Of the three cytokines, OSM alone induced VEGF in TNBC MDA-MB-231 cells, and this effect was mediated by signal transducer activator of transcription 3 (STAT3) signaling. However, both OSM and IL-6 increased VEGF secretion levels in ER+/PR+/Her2- T47D breast cancer cells, and this signaling was mediated by both HIF1α and pSTAT3, utilizing ELISA and Western blot analysis. These results implicate OSM as the key gp130 cytokine inducing VEGF secretion, and also suggest that this induction is not always HIF1α dependent and is cell-line specific. Citation Format: Danielle S. Hedeen, Ken Tawara, Madhuri Nandakumar, Ryan Fox, David Chang, Alex Ide, Andrew Oler, Dollie LaJoie, Cheryl L. Jorcyk. Differential expression of VEGF in breast cancer cells induced by gp130 cytokines. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4183. doi:10.1158/1538-7445.AM2015-4183