Dual-specificity phosphatase 26 is a novel p53 phosphatase and inhibits p53 tumor suppressor functions in human neuroblastoma.

Chemoresistance is a major cause of treatment failure and poor outcome in neuroblastoma. In this study, we investigated the expression and function of dual-specificity phosphatase 26 (DUSP26), also known as mitogen-activated protein kinase phophatase-8, in human neuroblastoma. We found that DUSP26 was expressed in a majority of neuroblastoma cell lines and tissue specimens. Importantly, we found that DUSP26 promotes the resistance of human neuroblastoma to doxorubicin-induced apoptosis by acting as a p53 phosphatase to downregulate p53 tumor suppressor function in neuroblastoma cells. Inhibiting DUSP26 expression in the IMR-32 neuroblastoma cell line enhanced doxorubicin-induced p53 phosphorylation at Ser20 and Ser37, p21, Puma, Bax expression as well as apoptosis. In contrast, DUSP26 overexpression in the SK-N-SH cell line inhibited doxorubicin-induced p53 phosphorylation at Ser20 and Ser37, p21, Puma, Bax expression and apoptosis. Using in vitro and in vivo assays, we found that DUSP26 binds to p53 and dephosphorylates p53 at Ser20 and Ser37. In this report, we show that DUSP26 functions as a p53 phosphatase, which suppresses downstream p53 activity in response to genotoxic stress. This suggests that inhibition of this phosphatase may increase neuroblastoma chemosensitivity and DUSP26 is a novel therapeutic target for this aggressive pediatric malignancy.

Synovial sarcoma in children and adolescents: thirty three years of experience with multimodal therapy.

BACKGROUND: Synovial sarcoma (SS) is the most common type of non-rhabdomyosarcoma soft tissue sarcoma in childhood, with controversies about its prognosis and treatment. PROCEDURE: We reviewed medical records of 42 children and adolescents with SS treated at our institution between 1966 and 1999 to determine treatment results and assess prognostic factors. RESULTS: With a median follow-up duration of 7.8 years (range 0.2-22.4 years), 5-year progression free survival (PFS) and overall survival (OS) rates were 75.6% (95% Confidence Interval [CI] 62-89.2%) and 87.7% (95% CI 77.3-98.1%) respectively. Eleven patients were dead and four others had progressed but were alive without evidence of disease after further therapy. IRS grouping and tumor invasiveness were found to be significant prognostic indicators (P < 0.01 and = 0.02, respectively). Patients with initial gross total resection (IRS I and II) and non-invasive tumors (T1) were most likely to have prolonged PFS and OS. Patients with small tumors (< 5 cm) (P = 0.09) or with monophasic histology (P = 0.14) had better PFS and OS. CONCLUSIONS: Achieving a complete resection or gross total resection with microscopic residual disease is vital for survival of patients with localized SS. Patients with localized disease who received radiotherapy had improved local control. Chemotherapy did not seem to impact PFS or OS. Future large multi-institutional trials are needed to address whether post-operative chemotherapy is necessary for patients with localized, surgically removed tumors, whether radiotherapy is necessary for patients with completely resected tumors, and to ascertain the order of importance of all the candidate prognostic markers. Med Pediatr Oncol 2001;37:90-96.

Synovial sarcoma in children: surgical lessons from a single institution and review of the literature.

BACKGROUND: Synovial sarcomas are malignant high-grade, soft-tissue neoplasms that account for 7% to 8% of all malignant soft-tissue tumors and are the most common nonrhabdomyosarcoma soft-tissue sarcomas in pediatric patients. STUDY DESIGN: A retrospective review of the records of children younger than 17 years with synovial sarcoma treated at the University of Texas MD Anderson Cancer Center from 1966 until 1999 was undertaken. Primary site, tumor size, tumor margins, surgical treatment, adjuvant therapy, local and distant recurrence, and survival were recorded for 42 patients. Overall survival (OS) and progression-free survival (PFS) rates were calculated by the Kaplan-Meier method. The PFS and OS comparisons were performed using the log-rank test. RESULTS: Forty-four patients were identified, but two patients were excluded because of incomplete records. The median followup duration for the 42 patients was 8.8 years (range 0.2 to 22.4 years). The 5-year progression-free survival and overall survival rates were 75.6% and 87.7%, respectively. Eleven patients were dead and four others had progressed but were alive without evidence of disease after further therapy. Intergroup Rhabdomyosarcoma Study (IRS) grouping and tumor invasiveness were found to be significant prognostic indicators (p < 0.01 and p = 0.02, respectively). Patients with initial gross total resection (IRS Groups I and II) and noninvasive tumors (T1) were most likely to have prolonged PFS and OS. Patients with small tumors (<5 cm) (p = 0.09) had better PFS and OS. Adjuvant radiation therapy appeared to be of benefit, and chemotherapy did not seem to impact PFS or OS. Tumors > or = 5 cm are associated with increased risk of local recurrence and distant metastases. CONCLUSIONS: Complete resection with clear, yet not necessarily large, margins remains the treatment of choice for synovial sarcoma in children. Adjuvant radiation therapy should possibly be considered in patients with clear margins (IRS Group I) and in patients with microscopic residual tumor (IRS Group II). Chemotherapy did not seem to impact PFS or OS. Lymph nodes should be evaluated for local regional disease.

Expression of Bcl-2-related genes in normal and AML progenitors: changes induced by chemotherapy and retinoic acid.

The expression of Bcl-2 family members was examined in normal and leukemic hematopoietic cells. Immature hematopoietic progenitor cells (CD34+/33-/13-) did not express Bcl-2 but Bcl-XL, the majority of CD34 cells expressed Bcl-2, Bcl-XL and BAD, and normal promyelocytes (CD34-/33+) lacked expression of both Bcl-2 and Bcl-XL, while leukemic CD34+progenitors and promyelocytes expressed these anti-apoptotic proteins. In AML, Bcl-2 expression was higher on CD34+ than on all AML cells, however, expression of Bcl-2 or Bcl-XL did not predict achievement of complete remission. Surprisingly, low Bcl-2 content was associated with poor survival in a group of patients with poor prognosis cytogenetics. The anti-apoptotic BAD protein was found to be expressed in AML, but was phosphorylated in 41/42 samples. Phosphorylation was found at both sites, Ser 112 and Ser 136. During induction chemotherapy, Bcl-2 levels of CD34 cells increased significantly. In the context of evidence for small numbers of leukemic CD34+ cells expressing very high levels of Bcl-2 prior to therapy, this finding is interpreted as a survival advantage of Bcl-2 overexpressing progenitors and rapid elimination of cells with low Bcl-2. Bcl-2 and Bcl-XL were both expressed in minimal residual disease cells. Downregulation of Bcl-2 mRNA and protein was observed by ATRA and the combination of Ara-C, followed by ATRA, resulted in markedly increased cytotoxicity in HL-60 cells, as compared to Ara-C alone or ATRA followed by Ara-C. Implications of these findings for the development of new therapeutic strategies for AML are discussed.

Differential increase of Fas ligand expression on metastatic and thin or thick primary melanoma cells compared with interleukin-10.

Fas ligand (FasL), a cell surface molecule belonging to the tumour necrosis factor family, binds to its receptor Fas and thus induces apoptosis of Fas-bearing cells such as activated lymphocytes. In this paper, we report the expression of FasL on melanoma cell lines and patient tumour specimens, and compare it with the expression of interleukin-10 (IL-10), a putative immunosuppressive factor. Apoptosis of Fas-bearing Jurkat cells was increased after interferon-alpha treatment of the FasL-positive melanoma cell line A375, suggesting a regulation of FasL function. We also tested whether FasL and IL-10 were ever co-expressed. Immunohistochemistry studies showed that IL-10 expression was highly positive in the same tumour samples which expressed FasL. In the melanoma patients with thin primaries, 10 of the 12 primaries and six of the seven metastatic lesions were positive for IL-10. In the melanoma patients with thick primaries (> 0.75 mm), four of the five primary lesions and nine of the 10 metastatic lesions were positive for IL-10. In contrast, FasL was generally negative in primary tumours and positive in metastatic tumours. In the thin primary melanoma patients, two of the 12 primaries and five of the seven metastatic tumours were positive for FasL. From the thick melanomas, one of the five primaries and five of the 10 metastatic lesions were positive for FasL. The function of melanoma-derived FasL was confirmed by four different cytotoxicity assays.

Attenuation of WAF1/Cip1 expression by an antisense adenovirus expression vector sensitizes glioblastoma cells to apoptosis induced by chemotherapeutic agents 1,3-bis(2-chloroethyl)-1-nitrosourea and cisplatin.

Previous studies have shown that the negative cell cycle regulator WAF1/Cip1 is often overexpressed in human gliomas and that WAF1/Cip1 overexpression renders glioma cells resistant to chemotherapy agents. In this study, we investigated whether down-regulation of WAF1/Cip1 would sensitize gliomas to chemotherapy. An adenoviral vector expressing antisense WAF1/Cip1 was constructed and used to infect D54 glioma cells, which express a high level of endogenous WAF1/Cip1. After D54 cells were infected with antisense WAF1/Cip1 adenovirus, Western blotting revealed a significant decrease in the WAF1/Cip1 protein level. Down-regulation of WAF1/Cip1 alone resulted in the cells rounding up and detaching from plates. Electron microscopy revealed some nuclear fragmentation in antisense WAF1/Cip1-infected cells, indicating the initiation of apoptosis. The antisense WAF1/Cip1-infected cells were then treated with the chemotherapeutic agents 1,3-bis(2-chloroethyl)-1-nitrosourea and cisplatin. Other cells were infected with sense WAF1/Cip1 adenovirus or control virus and served as controls. Trypan blue exclusion assay revealed significant cell death in antisense WAF1/Cip1-infected cells. In situ end-labeling assay by flow cytometry revealed that many cells died of apoptosis. Our results show that the attenuation of WAF1/Cip1 expression initiated glioma cell death and sensitized glioma cells to apoptosis induced by 1,3-bis(2-chloroethyl)-1-nitrosourea and cisplatin. Thus, blocking WAF1/Cip1 production may serve as a useful chemosensitization regimen for treating glioma.

Overexpressed WAF1/Cip1 renders glioblastoma cells resistant to chemotherapy agents 1,3-bis(2-chloroethyl)-1-nitrosourea and cisplatin.

Previous studies have shown that the negative cell cycle regulator WAF1/Cip1 is often overexpressed in human gliomas and that WAF1/Cip1 overexpression may be a factor in cancer chemoresistance. We established a doxycycline-inducible WAF1/Cip1 expression system in two glioblastoma cell lines and examined the role of WAF1/Cip1 in their response to the chemotherapy agents 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) and cis-diamminedichloroplatinum (cisplatin), in an isogeneic background. Our results showed that the induction of WAF1/Cip1 expression rendered glioma cells resistant to cell death induced by BCNU and cisplatin. Using an in vivo host-cell reactivation DNA repair assay, we demonstrated that WAF1/Cip1 enhances the repair of BCNU-induced DNA damage. We conclude that WAF1/Cip1 allows repair of BCNU- and cisplatin-damaged DNA and protects glioma cells from chemotherapy agent-induced apoptosis. Thus, blocking WAF1/Cip1 production or function may serve as a useful chemosensitization regimen for glioma.