Eisuke Arai

Inhibition of hyaluronan synthesis in breast cancer cells by 4‐methylumbelliferone suppresses tumorigenicity in vitro and metastatic lesions of bone in vivo

Hyaluronan (HA) has been shown to play crucial roles in the tumorigenicity of malignant tumors. Previous studies demonstrated that inhibition of HA suppressed the tumorigenicity of various malignant tumors including breast cancer. 4‐methylumbelliferone (MU) has been reported to inhibit HA synthesis in several cell types. However, few studies have focused on the effects of HA inhibition in breast cancer cells by MU, nor the effects on bone metastasis. We hypothesized that MU would suppress the progression of bone metastasis via inhibition of HA synthesis. Here, we investigated the effects of MU on HA expression in MDA‐MB‐231 breast cancer cell line in addition to their tumorigenicity in vitro and in vivo. HAS2 mRNA expression was downregulated after 6 and 24 hr treatment with MU. Quantitative analysis of HA revealed that MU significantly inhibited the intracellular and cell surface HA. MU significantly inhibited cell growth and induced apoptosis as determined by cell proliferation and TUNEL assays, respectively. Phosphorylation of Akt was suppressed after 12 and 24 hr treatment with MU. MU treatment also inhibited cell motility as well as cell invasiveness. MU also inhibited cell growth and motility in murine fibroblast cell line NIH3T3. In vivo, administration of MU inhibited the expansion of osteolytic lesions on soft X‐rays in mouse breast cancer xenograft models. HA accumulation in bone metastatic lesions was perturbed peripherally. These data suggest that MU might be a therapeutic candidate for bone metastasis of breast cancer via suppression of HA synthesis and accumulation.

Inhibition of hyaluronan retention by 4-methylumbelliferone suppresses osteosarcoma cells in vitro and lung metastasis in vivo.

Background:Hyaluronan (HA) plays crucial roles in the tumourigenicity of many types of malignant tumours. 4-Methylumbelliferone (MU) is an inhibitor of HA synthesis. Several studies have shown its inhibitory effects on malignant tumours; however, none have focused on its effects on osteosarcoma.Methods:We investigated the effects of MU on HA accumulation and tumourigenicity of highly metastatic murine osteosarcoma cells (LM8) that have HA-rich cell-associated matrix, and human osteosarcoma cell lines (MG-63 and HOS).Results:In vitro, MU inhibited HA retention, thereby reducing the formation of functional cell-associated matrices, and also inhibited cell proliferation, migration, and invasion. Akt phosphorylation was suppressed by MU (1.0 mM). In vivo, although MU showed only a mild inhibitory effect on the growth of the primary tumour, it markedly inhibited (75% reduction) the development of lung metastasis. Hyaluronan retention in the periphery of the primary tumour was markedly suppressed by MU.Conclusion:These findings suggested that MU suppressed HA retention and cell-associated matrix formation in osteosarcoma cells, resulting in a reduction of tumourigenicity, including lung metastasis. 4-Methylumbelliferone is a promising therapeutic agent targeting both primary tumours and distant metastasis of osteosarcoma, possibly via suppression of HA retention.

Osteoarthritic change is delayed in a Ctsk‐knockout mouse model of osteoarthritis

OBJECTIVE Several studies have shown that cathepsin K (CTK) is overexpressed in osteoarthritic (OA) cartilage and subchondral bone. However, it has not been well established whether CTK expression is harmful or beneficial. We undertook this study to investigate the direct involvement of CTK in OA development using Ctsk-knockout (Ctsk(-/-)) mice in a joint instability-induced model of OA. METHODS We analyzed the natural course of the phenotype of 25-week-old Ctsk(-/-) mice. OA development was evaluated with a modified Mankin histologic score up to 8 weeks after surgery was performed to destabilize the knee in Ctsk(-/-) and Ctsk(+/+) mice. Histologic analysis was used to evaluate expression of CTK, matrix metalloproteinase 13 (MMP-13), ADAMTS-5, and tartrate-resistant acid phosphatase (TRAP) proteins in chondrocytes, synovial cells, and osteoclasts. Bone architecture was analyzed by histomorphometry. RESULTS Bone mineral content and bone volume were higher in Ctsk(-/-) mice at 25 weeks, whereas OA did not develop spontaneously in either Ctsk(-/-) or Ctsk(+/+) mice. In a model of destabilization-induced OA, OA progression was significantly delayed in Ctsk(-/-) mice. CTK was overexpressed in chondrocytes and synovial cells of knee joints developing OA in Ctsk(+/+) mice. MMP-13 and ADAMTS-5 were less strongly expressed in chondrocytes of Ctsk(-/-) mice, and MMP-13 was less strongly expressed in synovial cells. TRAP-positive osteoclasts were overexpressed in Ctsk(-/-) mice. CONCLUSION These results indicate that CTK plays crucial direct roles in the early to intermediate stage of OA development. CTK-positive chondrocytes and synovial cells may be a possible target to prevent disease progression in OA.

Therapeutic potential of hyaluronan oligosaccharides for bone metastasis of breast cancer

Hyaluronan (HA) oligosaccharides were reported to have suppressive effects on various malignant tumors via disruption of receptor HA interactions. However, no studies have focused on the effects of HA oligosaccharides on bone metastasis of breast cancer. In this study, we clarified the effective size of HA oligosaccharides required to inhibit cell growth in the highly invasive breast cancer cell line, MDA‐MB‐231 cells. Based on the results of cell growth assay, we subsequently analyzed the effects of HA tetrasaccharides, HA decasaccharides, and high molecular weight HA on the other breast cancer cell behaviors in vitro and breast cancer bone metastasis in vivo. HA decasaccharides significantly inhibited cell growth, motility, and invasion, whereas tetrasaccharides did not. HAS2 mRNA expression was altered after the treatment with both tetrasaccharides and decasaccharides. Phosphorylation of Akt was suppressed after 1 h treatment with HA decasaccharides, and the effect was partially reversed by anti‐CD44 monoclonal antibody. In vivo, local application of HA decasaccharides inhibited the expansion of osteolytic lesions in tibia on soft X‐rays using mouse bone metastasis model of breast cancer. Histological analysis revealed HA accumulation in bone metastatic lesions was perturbed by decasaccharides. These results suggest that HA oligosaccharides suppressed progression of bone metastasis in breast cancer via interruption of endogenous HA–CD44 interaction, and as such, can be a novel therapeutic candidate to limit bone metastasis of breast cancer.

Osteochondral destruction in pigmented villonodular synovitis during the clinical course.

Objective. In pigmented villonodular synovitis (PVNS), some cases recur and progress to osteochondral destruction. The aim of our study was to clarify the occurrence of osteochondral destruction according to the location of PVNS during the clinical course. Methods. Seventy-two patients with PVNS (43 female, 29 male) with a mean age of 40 years (range 3–87 yrs) had been referred to our institutions. Factors influencing the occurrence of osteochondral destruction were investigated. Results. Mean followup was 60 months (range 12–190 mo). Adjacent bone change occurred in 24 (42%) of 57 patients, who were evaluated at the time of the first consultation. Eight (89%) of 9 patients with hip lesions initially had bone lesions, significantly more frequently than those with other lesions (p = 0.038). Duration of symptoms was significantly correlated with the occurrence of bone lesions in diffuse knee lesions (p = 0.005). During followup, patients with location in the knee had a significantly higher incidence of osteoarthritic change (73%) compared to those with foot and ankle involvement (p = 0.027). Re-operation was more frequently required for knee lesions due to the high recurrence rate (32%). Patients who required re-operation had significantly more marked osteoarthritic change in knees (p = 0.001) during followup than those who did not. Conclusion. For PVNS arising in knees, repeated recurrences followed by re-operation resulted in the progression of osteoarthritic change. PVNS arising in hips, feet, and ankles developed bone lesions initially, probably due to the limited volume of these joints. The indications for re-operation for recurrent knee lesions require careful consideration regarding progression of osteoarthritic change.

Regenerating the fibula with beta-tricalcium phosphate minimizes morbidity after fibula resection.

The aim of this study was to assess the radiologic and clinical outcome when beta-tricalcium phosphate is used as a bone graft substitute to backfill the fibular defect that is created by harvesting the fibula. Fourteen patients who had fibula resections to be used as bone grafts for bone tumor resections were assessed radiographically. Callus formation bridging the beta-tricalcium phosphate was seen in 12 of 14 patients at an average of 1.4 months after surgery. In these 12 patients the beta-tricalcium phosphate mostly was absorbed and replaced by newly formed bone at an average of 9.3 months after surgery. In all children, beta-tricalcium phosphate was replaced by newly formed bone at an average of 3.2 months after surgery. Only one adult patient had complete regeneration of the fibula. Few patients had continuity between the regenerated fibula and the native fibula. In one patient in whom free vascularized fibula was harvested, regeneration of the fibula was not observed. Clinical functional outcome was not correlated with successful fibula regeneration and union with the native fibula, as determined using radiographs. The results of the study suggest that, in children, regeneration of the fibula by implanting beta-tricalcium phosphate into a bone defect can reduce morbidity of the fibula harvest sites. Level of Evidence: Therapeutic study, Level IV (case series—no, or historical control group)

Versican V1 isoform regulates cell-associated matrix formation and cell behavior differentially from aggrecan in Swarm rat chondrosarcoma cells

Versican, a large chondroitin sulfate proteoglycan that binds hyaluronan and is composed of large extracellular matrix aggregates, has been shown to correlate with tumor progression. No studies have examined the roles of versican in chondrosarcoma nor compared them to those of aggrecan. In clinical specimens of human chondromatous tumors, versican expression was significantly increased in malignant tumors, moreover, as the tumor grade increased. To clarify the roles of versican in chondrosarcoma, versican splicing variant 1, variant 3 or only GFP was stably transfected to Swarm rat chondrosarcoma cells with Trap‐In System. Forced expression of versican V1 isoform in Swarm rat chondrosarcoma cells induced a marked increase of cell‐associated matrix compared to V3‐, GFP‐ transfected or RCS cells. Versican was immunolocalized in a fashion similar to that of hyaluronan and more diffusively than aggrecan. Anchor‐dependent and ‐independent growth was not affected by versican isoform expression, whereas cell motility and migration were significantly enhanced by V1 isoform transfection. Tumors formed in vivo with V1‐transfected cells exhibited more myxomatous area and included more spindle shaped cells. These results support the concept that versican has the capacity to form more extensive cell‐associated matrix than aggrecan, and the prominent matrix formation alters the cell behavior of chondrosarcoma more aggressively. These observations suggest that versican expression may serve as a marker of tumor grade determination in chondrosarcoma and possibly help to decide on therapeutic targets in higher grades of chondrosarcoma.

Increased expression and activation of cathepsin K in human osteoarthritic cartilage and synovial tissues

Few studies have analyzed Cathepsin K (CatK) expression in human osteoarthritic tissues. We investigated CatK expression and activation in human articular cartilage using clinical specimens. Human osteoarthritic cartilage was obtained during surgery of total hip arthroplasty (n = 10), and control cartilage was from that of femoral head replacement for femoral neck fracture (n = 10). CatB, CatK, CatL, CatS, and Cystatin C (CysC) expressions were evaluated immunohistochemically and by real‐time PCR. Intracellular CatK protein was quantified by ELISA. Intracellular CatK activity was also investigated. Osteoarthritis (OA) chondrocytes were strongly stained with CatK, particularly in the superficial layer and more damaged areas. CatB, CatL, CatS, and CysC were weakly stained. CatK mRNA expression was significantly higher in OA group compared to that in control group (p = 0.043), whereas those of CatB, CatL, CatS, and CysC did not differ significantly. Mean CatK concentration (4.83 pmol/g protein) in OA chondrocytes was higher than that (3.91 pmol/g protein) in control chondrocytes (p = 0.001). CatK was enzymatically more activated in OA chondrocytes as compared with control chondrocytes. This study, for the first time, revealed increased CatK expression and activation in human OA cartilage, suggesting possible crucial roles for it in the pathogenesis of osteoarthritic change in articular cartilage.

Hyaluronan synthesis inhibitor supplements the inhibitory effects of zoledronic acid on bone metastasis of lung cancer

Hyaluronan is known to have pivotal roles in the growth, migration and invasion of malignant tumors. Bone metastases are critical lesions greatly impairing the quality of patients with malignancies. We investigated whether hyaluronan synthesis inhibitor supplements the inhibitory effects of zoledronic acid, which is a conventional therapeutic agent for bone metastasis. We examined the effects of methylumbelliferone, an inhibitor of hyaluronan synthesis and/or ZA on the tumorigenicity of one murine lung carcinoma and two human (A549, SK-MES-1) lung cancer cell lines in vitro. The interaction between methylumbelliferone and zoledronic acid was analyzed using Calcucyn software. With a murine bone metastasis model of lung cancer in vivo, we investigated the inhibitory effects and interaction of the two drugs on the progression of metastatic bone lesions. Methylumbelliferone or zoledronic acid treatment individually suppressed proliferation, migration and invasion of 3 cell lines, and combination treatment showed synergistic effects. Although methylumbelliferone as a single agent did not enhance apoptotic activity, it showed additive effects on apoptotic activity to those of zoledronic acid. Co-localization of CD44 and ezrin, which might be a pathway of hyaluronan signaling, was abrogated by methylumbelliferone treatment. Combination therapy showed additive inhibitory effects on metastatic bone lesions in vivo, which paralleled the inhibition of hyaluronan accumulation by methylumbelliferone, and inhibition of osteoclastogenesis. Although the detailed mechanisms underlying the synergistic or additive inhibitory effects of these two drugs should be further analyzed, inhibition of hyaluronan synthesis by methylumbelliferone is a promising novel therapeutic candidate for bone metastasis of lung cancer in addition to zoledronic acid.

Is It Possible to Identify Clinically Useful Prognostic Groups for Patients With Desmoid Tumors

TO THE EDITOR: In their recent article, Salas et al 1 report the results of a retrospective study of 426 patients with extra-abdominal desmoid tumors from 24 participating centers. To our knowledge, this is the largest such cohort ever reported. Three hundred seventy patients (86.9%) had surgical treatment initially; a wait-and-see policy was adopted for only 27 patients (6.3%). Patients who had non–lifethreatening tumors or who were at risk for mutilation were selected for the wait-and-see approach. Detailed characteristics of the patients in the wait-and-see group were not provided. Factors that had a significant impact on progression-free survival were age, tumor size, and tumor site in multivariate analysis. It can be understood that there are different prognostic subgroups of patients with desmoid tumors who could benefit from different therapeutic strategies. However, given that these factors are associated mainly with the results of surgical treatment (86.9% of patients) rather than the wait-and-see policy (6.3% of patients), it seems inappropriate to apply the factors extracted by the authors for the determination of the optimal treatment modality, particularly a wait-and-see policy. The constitutional host environment differed with respect to factors such as released growth factors 2 between tumors treated surgically, those treated with the wait-and-see approach, and possibly those treated medically. Therefore, factors determined by the cohort treated surgically are not applicable when another treatment modality is chosen. A previous study 3 revealed the results of a wait-and-see policy for patients with desmoid tumors. Fiore et al 3 retrospectively demonstrated that the 5-year progression-free survival in 83 such patients was 49.9%, in contrast to 58.6% in medically treated patients, with no statistical significance between the two groups. However, Fiore et al indicated that the characteristics of the patients in the wait-and-see group differed from those of the medical therapy group, suggesting that it is impossible from a retrospective series to extract patients who are suitable for a wait-and-see approach, conservative medical therapy, or surgical treatment. We have previously reported (prospectively) 22 consecutive patients with extra-abdominal desmoid tumors who were treated with meloxicam, a cyclooxygenase-2 selective inhibitor. 4 At the time of submission, the median period of meloxicam administration was 20 months (range, 3 to 66 months), and currently is 36 months (range, 3 to 81 months). Excluding the patients with unavailable evaluation information, the previous results were one patient with complete remission, seven with partial remission (PR), 11 patients with stable disease (SD), and one patient with progressive disease. The current results are one patient with complete remission, 10 patients with PR, seven patients with SD, and one patient with progressive disease, representing a slight improvement compared with the previous results. Salas et al 1 demonstrated that the location had a significant impact on prognosis. Limb tumors had a poor prognosis, which is consistent with the results reported by Balo et al. 5 However, these results were based mostly on treatment with surgery, surgery plus radiotherapy, or radiotherapy alone, and do not seem applicable to the cohort treated with a wait-and-see policy or conservative medical therapy. In fact, in our study, 4 seven of 22 patients had limb lesions, four of whom achieved PR and three of whom achieved SD with meloxicam, which is satisfactory compared with the results reported by Salas et al. These results (ours 4 and those of Salas et al 1 ) suggest that the different prognostic subgroups of patients with desmoid tumors should be determined independently and be recipients of different treatment modalities, whereas a prospective cohort study in which all patients receive identical treatment is required to extract the genuine prognostic factors in each treatment modality– dependent subgroup.