Kenichiro Hamada

Synovial sarcoma is a stem cell malignancy.

Synovial sarcoma (SS) is a malignant soft tissue tumor characterized by its unique t(X;18)(p11;q11) chromosomal translocation leading to the formation of the SS18‐SSX fusion gene. The resulting fusion protein product is considered to play as an aberrant transcription factor and transform target cells by perturbing their gene expression program. However, the cellular origin of SS is highly debated. We herein established two novel human SS cell lines, named Yamato‐SS and Aska‐SS, and investigated their biological properties. We found the self‐renewal ability of these cells to generate sarcospheres, to form tumors in serial xenotransplantation and reconstitute the tumor phenotypes without fractionation by any surface markers. Both SS cells as well as clinical tissue specimens from 15 patients expressed the marker genes‐associated stem cell identity, Oct3/4, Nanog, and Sox2. We also found that both SS cells displayed limited differentiation potentials for mesenchymal lineages into osteocytes and chondrocytes albeit with the expression of early mesenchymal and hematopoietic lineage genes. Upon SS18‐SSX silencing with sequence‐specific siRNAs, these SS cells exhibited morphological transition from spherical growth in suspension to adherent growth in monolayer, additional expression of later mesenchymal and hematopoietic lineage genes, and broader differentiation potentials into osteocytes, chondrocytes, adipocytes, and macrophages in appropriate differentiation cocktails. Collectively, these data suggest that a human multipotent mesenchymal stem cell can serve as a cell of origin for SS and SS is a stem cell malignancy resulting from dysregulation of self‐renewal and differentiation capacities driven by SS18‐SSX fusion protein. STEM CELLS 2010;28:1119–1131

Evaluation of chemotherapy response in osteosarcoma with FDG-PET.

ObjectiveThe objective of this study is to evaluate the utility of positron emission tomography (PET) with 2-deoxy-[18F] fl uoro-D-glucose (FDG) in the assessment of the chemotherapy response of osteosarcoma when compared with the degree of necrosis determined histologically.MethodsWhole-body FDG-PET scan was performed on 11 patients with osteosarcoma. All patients received neoadjuvant chemotherapy. The tumor size changes on magnetic resonance imaging; FDG-PET standardized uptake values prior to (SUV1) and following (SUV2) chemotherapy were analyzed and correlated with response to chemotherapy as assessed using histopathology in surgically excised tumors. Nine patients underwent FDG-PET scan both prior to and following neoadjuvant chemotherapy. The remaining two patients were examined only prior to surgery.ResultsHistologically, five patients had a good histologic response to chemotherapy (≧90% necrosis). The changes in tumor size did not correlate with histologic response (P > 0.05). SUV2 with good response was significantly lower than that with poor response (1.93 ± 0.50, 5.86 ± 2.55, respectively). Both the positive and negative predictive values of the SUV2 of less than 2.5 for a good response were 100%. Patients with good response showed a significantly higher ratio of SUV2 to SUV1 (SUV2:1) than patients with poor response (0.74 ± 0.11, 0.26 ± 0.39, respectively, P < 0.05). The positive and negative predictive values of SUV2:1 ≤ 0.5 for good and poor responses were 80% and 100%, respectively.ConclusionsFDG-PET imaging of osteosarcoma correlates positively with histologic response to neoadjuvant chemotherapy. SUV2 and SUV2:1 could be feasible as non-invasive surrogate predictors of response in osteosarcoma patients.

Prognostic significance of activated AKT expression in soft-tissue sarcoma.

Purpose: AKT is a serine/threonine kinase which is important in tumorigenesis. Several molecules involved in AKT pathway are dysregulated in various kinds of human cancers. Patients and Methods: Ninety-three patients (53 males and 40 females), ages ranging from 19 to 77 years (median, 57 years), with localized soft-tissue sarcomas arising in the trunk and extremities, were analyzed. Immunoperoxidase procedure (avidin-biotin complex method) was done on paraffin-embedded sections with anti–phosphorylated AKT (Thr308), anti–phosphorylated p44/42 extracellular signal–regulated kinase 1 and 2 (ERK1/2) (Thr202/Tyr204), anti–phosphorylated forkhead in rhabdomyosarcoma (FKHR) (Ser256), and anti-Ki 67 antibodies. Expression levels of phosphorylated AKT (p-AKT), phosphorylated ERK1/2 (p-ERK1/2), and phosphorylated FKHR (p-FKHR) were categorized as either weaker (level 1) or equal to or stronger (level 2) compared with those in the endothelial cells of the same specimens. Percentage of cells showing intranuclear staining with Ki-67 was shown as the Ki-67 labeling index (LI). Cases were divided into two groups: level 1, Ki-67 LI < 20%; level 2, Ki-67 LI ≥ 20%. Results: Twenty-six (28.0%), 6 (6.5%), and 46 (44.1%) of the tumors showed level 2 expression for p-AKT, p-ERK1/2, and Ki-67 LI, respectively. Tumors with level 2 p-AKT expression showed a higher ratio of level 2 p-FKHR expression (P < 0.01). Multivariate analysis revealed p-AKT expression and Ki-67 LI to be independent prognosticators for overall survival, and p-AKT expression for disease-free survival. Conclusion: p-AKT expression level is a significant prognosticator in soft-tissue sarcoma.

Mucosa-associated lymphoid tissue lymphoma studied with FDG-PET: a comparison with CT and endoscopic findings

ObjectiveWe investigated the accumulation of 2-deoxy-2-[18F] fluoro-d-glucose positron emission tomography (FDG-PET) in patients with mucosa-associated lymphoid tissue (MALT) lymphoma patients as compared with computerized tomography (CT) and endoscopic imaging.MethodsFDG-PET was performed on 13 untreated patients with MALT lymphoma. CT scanning of the affected areas was performed in all the patients to compare with the FDG-PET images. In five patients with gastric MALT lymphoma, comparison was also made with the endoscopic findings.ResultsOf the 13 untreated MALT lymphoma patients, all 8 non-gastric MALT lymphoma patients exhibited abnormal accumulation of FDG. However, in the five gastric MALT lymphoma patients, no abnormal FDG accumulation was observed. Although lesions could be confirmed on CT images from the patients other than those with gastric MALT lymphoma, the mucosal lesions of gastric MALT lymphoma could be observed only by endoscopy.ConclusionsFDG-PET can be used to detect MALT lymphoma when it forms mass lesions, whereas it is difficult to detect non-massive MALT lymphoma of gastrointestinal origin.

Prognostic significance of CD100 expression in soft tissue sarcoma

CD100, a class IV semaphorin, promotes angiogenesis, invasive growth, proliferation, and antiapoptosis of cancer cells in vitro. The expression of CD100 in soft tissue sarcoma (STS) and its correlation with clinicopathologic factors and prognostic significance were evaluated.

Evaluation of delayed18F-FDG PET in differential diagnosis for malignant soft-tissue tumors

ObjectivePositron emission tomography (PET) with 2-deoxy-2-[18F]fiuoro-D-glucose (18F-FDG) has been used for the evaluation of soft-tissue tumors. However, the range of accumulation of18F-FDG for malignant soft-tissue lesions overlaps with that of benign lesions. The aim of this study is to investigate the usefulness of delayed18F-FDG PET imaging in the differentiation between malignant and benign soft-tissue tumors.MethodsFifty-six patients with soft-tissue tumors underwent whole body18F-FDG PET scan at 1 hour (early scan) and additional scan at 2 hours after injection (delayed scan). The standardized uptake value (SUVmax) of the tumor was determined, and the retention index (RI) was defined as the ratio of the increase in SUVmax between early and delayed scans to the SUVmax in the early scan. Surgical resection with histopathologic analysis confirmed the diagnosis.ResultsHistological examination proved 19 of 56 patients to have malignant soft-tissue tumors and the rest benign ones. In the scans of all 56 patients, there was a statistically significant difference in the SUVmax between malignant and benign lesions in the early scan (5.50 ± 5.32 and 3.10 ± 2.64, respectively, p < 0.05) and in the delayed scan (5.95 ± 6.40 and 3.23 ± 3.20, respectively, p < 0.05). The mean RI was not significantly different between malignant and benign soft-tissue tumors (0.94 ± 23.04 and -2.03 ± 25.33, respectively).ConclusionsIn the current patient population, no significant difference in the RI was found between malignant and benign soft-tissue lesions. Although the mean SUVmax in the delayed scan for malignant soft-tissue tumors was significantly higher than that for benign ones, there was a marked overlap. The delayed18F-FDG PET scan may have limited capability to differentiate malignant soft-tissue tumors from benign ones.

18F-FDG-PET of musculoskeletal tumors: a correlation with the expression of glucose transporter 1 and hexokinase II

ObjectiveIt remains controversial whether positron emission tomography (PET) with 2-deoxy-2-[F-18]fluoro-d-glucose (F-18-FDG) can differentiate between benign and malignant musculoskeletal tumors. To uncover the mechanism of F-18-FDG accumulations, we analyzed the correlation between the F-18-FDG accumulation and the expression of glucose transporter 1 (Glut-1) and hexokinase II (HK-II) in benign and malignant musculoskeletal tumors.MethodsThe maximum standardized uptake values (SUVmax) of F-18-FDG in 24 benign and 26 malignant musculoskeletal tumors were compared with the histologic malignancies, and the expression of Glut-1 and HK-II was analyzed by immunohistochemistry.ResultsThe SUVmax for malignant tumors (6.33 ± 4.79) was significantly higher than those with benign tumors (3.47 ± 3.12, P < 0.01). The expression of Glut-1 was high in 12 patients (all malignant) and low in 38 patients (24 benign and 14 malignant), and the expression of HK-II was high in 36 patients (11 benign and 25 malignant) and low in 14 patients (13 benign and 1 malignant). Cases with high expression of Glut-1 and HK-II at immunohistochemistry showed a higher SUVmax than those with low expression (Glut-1 8.03 ± 5.10 and 3.98 ± 3.53, P < 0.01; HK-II 5.73 ± 4.49 and 2.99 ± 3.02, P < 0.01). No significant dividing threshold of the SUVmax of F-18 FDG was found for the differential diagnosis between benign and malignant tumors or for the expression of Glut-1 and HK-II.ConclusionsThe limited capability of F-18 FDG-PET in the differential diagnosis of musculoskeletal tumors is owing partly to the various levels of Glut-1 and HK-II expression in individual tumors.

Combined targeting of mTOR and c-MET signaling pathways for effective management of epithelioid sarcoma.

BackgroundEpithelioid sarcoma (EpS) is a high-grade malignant soft-tissue sarcoma characterized by local recurrences and distant metastases. Effective treatments for EpS have not been established and thus novel therapeutic approaches against EpS are urgently required. mTOR inhibitors exert antitumor effects on several malignancies but AKT reactivation by mTOR inhibition attenuates the antitumor effects of mTOR inhibitors. This reactivation is receptor tyrosine kinase (RTK)-dependent due to a release of negative feedback inhibition. We found that c-MET was the most highly activated RTK in two human EpS cell lines, Asra-EPS and VAESBJ. Here we investigated the functional and therapeutic relevance of mTOR and/or c-MET signaling pathways in EpS both in vitro and in vivo.MethodsWe first examined the effects of an mTOR inhibitor, RAD001 (everolimus), on cell proliferation, cell cycle, AKT/mTOR signaling, and xenograft tumor growth in EpS cell lines. Next, we determined whether RAD001-induced AKT reactivation was blocked by silencing of c-MET or treatment with a selective c-MET inhibitor, INC280. Finally, we evaluated the antitumor effects of RAD001 combined with INC280 on EpS cell lines compared with either single agent or control in vitro and in vivo.ResultsConstitutive AKT phosphorylation was observed in Asra-EPS and VAESBJ cells. RAD001 suppressed EpS cell growth by inducing cell cycle arrest but enhanced AKT phosphorylation, which resulted in intrinsic resistance to mTOR inhibitors. In both EpS cell lines, RAD001-induced AKT phosphorylation was dependent on c-MET signaling. INC280 inhibited phosphorylation of c-MET and its downstream molecules, and decreased RAD001-induced phosphorylation of both AKT and ERK in EpS. Compared with a single agent or control, the combination of RAD001 and INC280 exerted superior antitumor effects on the growth of EpS cell lines in vitro and in vivo.ConclusionsTargeting of mTOR and c-MET signaling pathways significantly abrogates the growth of EpS in preclinical models and may be a promising therapeutic approach for patients with EpS.

Prognostic Value of FDG-PET in Patients with Oropharyngeal Carcinoma Treated with Concurrent Chemoradiotherapy

The purpose of this study was to evaluate the predictive value of 2-deoxy-2-[F-18]fluoro-d-glucose-positron emission tomography (FDG-PET) following concurrent chemoradiotherapy (CRT) on survival in patients with carcinoma of the oropharynx (OPC). Eighteen patients with primary OPC who underwent PET pre- and post-CRT were evaluated prospectively for survival. The prognostic performance of post-CRT PET and CT for recurrence was compared. Patients with positive post-CRT PET exhibited significantly lower 2-year cause-specific survival and disease-free survival (50% vs. 91%, P < 0.05 and 0% vs. 83%, P < 0.0001); however, patients with positive post-CRT CT did not exhibit any significant difference (67% vs. 83%, P = 0.416 and 50% vs. 75%, P = 0.070). Other factors, such as clinical and pre-CRT PET variables, also did not indicate any significant difference. The accuracy of prediction of residual and local recurrence for post-CRT PET and CT (local%/regional%) was 83%/94% and 83%/78%, respectively. OPC patients with positive post-CRT PET exhibit poor survival. The prognostic accuracy of post-CRT PET is superior to that of CT. The results of post-CRT FDG-PET should be included in the management of the OPC patients.

Eleven Cases of Cardiac Metastases from Soft-tissue Sarcomas

OBJECTIVE Cardiac metastasis is a highly life-threatening condition because it leads to cardiac failure. However, it is difficult to diagnose because its precise clinical features are unknown. Here, we report 11 cases of cardiac metastasis from soft-tissue sarcoma, and discuss its diagnosis and treatment. METHODS Of 641 patients with soft-tissue sarcoma treated in our institute between 1996 and 2009, we retrospectively reviewed the medical records of 11 patients whose cardiac metastases were diagnosed while they were alive. RESULTS The most common primary tumor was leiomyosarcoma (n= 5), followed by clear cell sarcoma (n= 2). In all cases, metastases to other organs, including lungs (n= 10), soft tissues (n= 5) and bones (n= 4) were found along with cardiac metastases. Cardiac metastasis was diagnosed by echocardiography in six cases and by computed tomography in four cases. In four patients, cardiac metastasis was not detected by chest computed tomography as follow-up to lung metastases and echocardiography was required to make the diagnosis. Although five patients complained of exertional dyspnea, four were asymptomatic. Seven cases were treated with radiotherapy. No patient had surgery for their cardiac metastasis. The median survival of patients who received radiation therapy was 10.5 months; that of those who did not was 3.5 months. CONCLUSIONS Cardiac metastasis is often asymptomatic. Echocardiography is better than computed tomography for diagnosing cardiac metastasis, and should be considered in all patients presenting with soft-tissue metastases. Owing to the highly life-threatening nature of cardiac metastases and the possibility of soft-tissue dissemination, treatment with radiation therapy is recommended immediately on diagnosis.