Usefulness of daily teriparatide treatment in elderly patients over 80 years of age

The percent and absolute lumbar spine and femoral neck bone mineral densities and procollagen type I N-terminal propeptide (PINP) and urinary N-telopeptide level increases noted after teriparatide 20 μg/day treatment for 24 months were similar in the older (age ≥ 80 years) and younger (age < 80 years) subgroups.

INTRODUCTION

Many individuals are living into their eighth and ninth decades, but little is known about the efficacy of osteoporosis medication for this population. We retrospectively compared usefulness of daily teriparatide therapy in osteoporosis patients ≥80 and <80 years to detect possible age-related differences.

METHODS

We analyzed 628 osteoporosis patients treated with teriparatide 20 μg/day for 24 months. The primary efficacy measures were changes in lumbar spine (LS) and femoral neck (FN) bone mineral density (BMD) over 24 months. Changes in serum procollagen type I N-terminal propeptide levels and urinary N-telopeptide (uNTX) excretion were also measured. Patients were divided into age subgroups (older, ≥80 years; younger, <80 years) for BMD and bone turnover marker comparison.

RESULTS

In the older subgroup, the percent LS BMD significantly increased by 14.6 ± 10.4 % (mean ± SD) and FN BMD significantly increased by 4.5 ± 10.7 % at 24 months. In the younger subgroup, the percent LS BMD significantly increased by 12.2 ± 8.5 % and FN BMD significantly increased by 2.9 ± 8.3 % at 24 months. In the older subgroup, the mean absolute LS BMD change was 0.111 ± 0.071 g/cm(2) and FN BMD change was 0.019 ± 0.043 g/cm(2). In the younger subgroup, the mean absolute LS BMD change was 0.098 ± 0.065 g/cm(2) and FN BMD change was 0.016 ± 0.045 g/cm(2). The percent and absolute BMD increases in LS and FN and changes in PINP and uNTX were similar between the subgroups.

CONCLUSIONS

The usefulness of daily teriparatide treatment is not age dependent.

The value of the high-sensitivity modified Glasgow prognostic score in predicting the survival of patients with a soft-tissue sarcoma

The aim of this study was to determine whether the high-sensitivity modified Glasgow prognostic score (Hs-mGPS) could predict the disease-specific survival and oncological outcome in adult patients with non-metastatic soft-tissue sarcoma before treatment. A total of 139 patients treated between 2001 and 2012 were retrospectively reviewed. The Hs-mGPS varied between 0 and 2. Patients with a score of 2 had a poorer disease-specific survival than patients with a score of 0 (p < 0.001). The estimated five-year rate of disease-specific survival for those with a score of 2 was 0%, compared with 85.4% (95% CI 77.3 to 93.5) for those with a score of 0. Those with a score of 2 also had a poorer disease-specific survival than those with a score of 1 (75.3%, 95% CI 55.8 to 94.8; p < 0.001). Patients with a score of 2 also had a poorer event-free rate than those with a score of 0 (p < 0.001). Those with a score of 2 also had a poorer event-free survival than did those with a score of 1 (p = 0.03). A multivariate analysis showed that the Hs-mGPS remained an independent predictor of survival and recurrence. The Hs-mGPS could be a useful prognostic marker in patients with a soft-tissue sarcoma.

Analysis of daily teriparatide treatment for osteoporosis in men

The percent and absolute lumbar spine and femoral neck bone mineral densities and absolute procollagen type I N-terminal propeptide (PINP) increases following a 20-μg/day teriparatide treatment for 12 months were similar in men and women regardless of sex differences.

INTRODUCTION

Several placebo-controlled studies have measured the effects of daily teriparatide in men and postmenopausal women with osteoporosis but none have directly compared the effects between these groups. We retrospectively compared the effects of daily teriparatide therapy in men and postmenopausal women with osteoporosis and investigated biochemical markers of bone turnover to detect possible sex differences.

METHODS

Patients (563; 75 men and 488 women) with osteoporosis were retrospectively investigated. All patients were administered with teriparatide at 20 μg/day for 12 months. The primary efficacy measure was changed in lumbar spine (LS) and femoral neck (FN) bone mineral density (BMD) after 12 months of treatment. The change in serum levels of procollagen type I N-terminal propeptide (PINP) and urinary N-telopeptide (uNTX) excretion after 4, 8 and 12 months of treatment were also measured.

RESULTS

In men, the percent LS BMD significantly increased by 11.3 ± 9.9 % (mean ± standard deviation (SD)) and the FN BMD increased by 0.4 ± 6.4 % without a significant difference at 12 months. In postmenopausal women, the percent LS BMD significantly increased by 9.6 ± 8.1 % and the FN BMD significantly increased by 2.4 ± 7.8 % at 12 months. The percent and absolute BMD increases in LS and FN between men and women were similar. The absolute increases in PINP were similar in both groups at 4, 8 and 12 months. However, the absolute increases in uNTX were significantly lower in men than in women at 8 and 12 months.

CONCLUSION

Daily teriparatide treatment was as effective in men as in postmenopausal women regardless of sex differences.

Efficacy of the dynamic radiographs for diagnosing acute osteoporotic vertebral fractures

We investigated the efficacy of dynamic radiographs for diagnosing acute osteoporotic vertebral fractures (OVFs) compared with supine radiographs or sitting radiographs alone. Evaluation of the dynamic radiographs was superior to the other evaluations. Dynamic radiographs provide a convenient and useful method of diagnosing acute OVFs.

INTRODUCTION

Identifying acute OVFs on plain radiographs is difficult. We studied a new approach to identify acute OVFs on the basis of fracture mobility.

METHODS

We performed a retrospective radiographic analysis of 472 acute OVFs (<3 weeks after onset), which were diagnosed on the basis of magnetic resonance imaging of T5 through L5 (a total of 5,239 vertebrae). Supine lateral radiographs were compared with sitting lateral radiographs to determine the presence or absence of mobility. Vertebrae showing changes in the vertebral body height were diagnosed as acute OVFs. We analyzed the diagnostic accuracy on the basis of comparative supine and sitting lateral radiographs and compared it with that of radiographs obtained in the supine or the sitting position alone.

RESULTS

Of the 472 acute OVFs diagnosed, 313 (66 %) exhibited vertebral mobility on supine lateral and sitting lateral radiographs. Correct diagnoses of acute OVFs or no acute OVFs were made in 4,883 vertebrae. There were 159 unreadable OVFs (3 %), and 197 previous OVFs (4 %) were misdiagnosed as acute OVFs. The sensitivity was 66 % and the specificity was 96 %. Evaluation of the mobility of acute OVFs in the supine and the sitting position was superior to evaluation using radiographs in either the supine or the sitting position alone.

CONCLUSIONS

Dynamic radiographs provide a convenient way to identify acute OVFs.

An algorithm using the early changes in PINP to predict the future BMD response for patients treated with daily teriparatide

About two thirds of patients with a procollagen type I N-terminal propeptide (PINP) increase of >80 μg/l at 1 month after starting teriparatide therapy showed a ≥10 % increase in lumbar spine (LS) bone mineral density (BMD) from baseline at 12 months. We recommend this algorithm as an aid in the clinical management of patients treated with daily teriparatide.

INTRODUCTION

An algorithm using PINP is provided in osteoporotic patients with teriparatide treatment. The correlations between the early changes in PINP and the subsequent BMD changes after daily teriparatide therapy were studied to develop an algorithm to monitor patients.

METHODS

We evaluated whether early changes in PINP correlated with the changes in BMD at 12 months and developed an algorithm using the early changes in PINP to predict the upcoming BMD increases.

RESULTS

The highest correlation coefficient for the relationship between PINP and LS BMD response was determined for the absolute change in PINP at 1 month and the percent change in LS BMD at 12 months (r = 0.36, p <0.01). Using a receiver operator curve analysis, we determined that an 80 μg/l increase in PINP was the most convenient predictor of a 10% increase in LS BMD from baseline (area under curve = 0.72). Using a cut-off value of 80 μg/l, the positive predictive value for predicting a 10% increase in LS BMD from baseline to 12 months was 65%.

CONCLUSION

Greater short-term changes in PINP with teriparatide therapy are associated with greater 12-month increases in LS BMD. About two thirds of patients with a PINP increase of >80 μg/l at 1 month after starting treatment showed a ≥10 % increase in LS BMD from baseline at 12 months. We recommend this algorithm as an aid in the clinical management of patients treated with teriparatide.

Deep-vein thrombosis after resection of musculoskeletal tumours of the lower limb

The aim of this study was to define the incidence of venous thromboembolism (VTE) and risk factors for the development of deep-vein thrombosis (DVT) after the resection of a musculoskeletal tumour. A total of 94 patients who underwent resection of a musculoskeletal tumour between January 2003 and December 2005 were prospectively studied. There were 42 men and 52 women with a mean age of 54.4 years (18 to 86). All patients wore intermittent pneumatic compression devices and graduated compression stockings. Ultrasound examination of the lower limbs was conducted to screen for DVT between the fifth and ninth post-operative days. DVT was detected in 21 patients (22%). Of these, two were symptomatic (2%). One patient (1%) had a fatal pulmonary embolism. Patients aged ≥ 70 years had an increased risk of DVT (p = 0.004). The overall incidence of DVT (both symptomatic and asymptomatic) after resection of a musculoskeletal tumour with mechanical prophylaxis was high. It seems that both mechanical and anticoagulant prophylaxis is needed to prevent VTE in patients who have undergone the resection of a musculoskeletal tumour.

Expression of ADAMTS4 in Ewing's sarcoma

Ewing's sarcoma (EWS) is a malignant bone tumor that frequently occurs in teenagers. Genetic mutations which cause EWS have been investigated, and the most frequent one proved to be a fusion gene between EWS gene of chromosome 22 and the FLI1 gene of chromosome 11. However, a limited numbers of useful biological markers for diagnosis of EWS are available. In this study, we identified ADAMTS4 (a disintegrin and metalloproteinase with thrombospondin motifs) as a possible tumor marker for EWS using the retrovirus-mediated signal sequence trap method. ADAMTS4 is a secreted protein of 837 amino acids with a predicted molecular mass of 98-100 kDa. It is a member of metalloprotease family, is expressed mainly in cartilage and brain, and regulates the degradation of aggrecans. ADAMTS4 has been suggested to be involved in arthritic diseases and gliomas. Herein, we show that ADAMTS4 mRNA was expressed in all primary EWS samples and all EWS-derived cell lines examined, while its expression was detected only in small subpopulations of other solid tumors. Furthermore, ADAMTS4 expression was found to be regulated by EWS-FLI1 fusion gene-dependent manner. We also demonstrated that ADAMTS4 protein was highly expressed in tumor samples of the patients with EWS by using immunohistochemistry. These results suggest that ADAMTS4 is a novel tumor marker for EWS.

Photodynamic therapy with acridine orange in musculoskeletal sarcomas

Limb salvage involving wide resection and reconstruction is now well established for managing musculoskeletal sarcomas. However, involvement of major nerves and vessels with a large volume of muscle and skin may result in a useless limb, contributing to depression and a low quality of life. We have been studying alternative treatments for musculoskeletal sarcoma since 1990, and have recently established a regime using photodynamic surgery with cells labelled with acridine orange, photodynamic therapy with cells treated similarly and radiodynamic treatment using the effect of X-rays on such cells. These techniques have been used after marginal or intralesional resection of tumours since 1999 and have enabled maintenance of excellent limb function in patients with sarcomas.

Diffuse gliomas in an adolescent with multiple enchondromatosis (Ollier's disease)

Ollier's disease is characterized by the hamartomatous proliferation of cartilage cells, producing masses termed chondromas. A patient presented with Ollier's disease which was found to be associated with diffuse gliomas. Investigating this disease is crucial as there is a high risk of sarcomatous transformation of the skeletal lesions as well as an increased risk of developing extra-osseous malignancies.

Histiocytic osteolysis secondary to hyperbilirubinaemia: a case report

A 6-year-old boy with Alagille syndrome, characterised by marked hyperbilirubinaemia, presented with malunion of a pathological fracture of the femur with local bone atrophy and insufficient callus formation. During corrective osteotomy, it was noted that the femur was stained dark green, suggestive of bilirubin deposition. Histology of the resected bone revealed the presence of many histiocytes and osteoclast-like multinucleate giant cells containing bilirubin particles in the cytoplasm causing bone resorption. These findings suggest that bilirubin may activate macrophages to form osteoclast-like multinucleate giant cells, resulting in histiocytic osteolysis.

Asymptomatic disseminated carcinomatosis of bone marrow presenting as hyperphosphatasia: report of a case

Metastatic involvement of the musculoskeletal system is one of the most significant clinical issues facing orthopaedic oncologists. The number of patients with metastasis to the skeletal system from a carcinoma is 15 times greater than the number of patients with primary bone tumours of all types. However, progression patterns like disseminated carcinomatosis of bone marrow are comparatively rare. The pathophysiology for disseminated carcinomatosis of bone marrow, with a prognosis reported to be very poor, is still unknown. We describe a patient who had no symptoms with hyperphosphatasia. Bone scintigraphy showed a so-called super bone scan and a needle biopsy from the ileum showed adenocarcinoma cells. Additional endoscopic investigation was performed and signet cell gastric cancer was found. From the bone scan and biopsy, we established the diagnosis of disseminated carcinomatosis of the bone marrow. From the experience of this case, we believe that intensive stomach investigation should be considered in cases with hyperphosphatasia, even when the patient has no symptoms.

Foreign-body granulomas in the trunk and extremities may simulate malignant soft-tissue tumors: report of three cases

Three cases of foreign-body granulomas arising from soft tissues of the extremities or trunk are reported. All patients had a history of having undergone surgery 19 to 35 years ago. It was difficult to distinguish these granulomas from malignant soft-tissue tumors preoperatively by magnetic resonance (MR) images, as the tumors were over 10 cm in diameter and degenerated foreign bodies could not be detected on MR images. Finally, a histological diagnosis of foreign-body granuloma was made by preoperative or intraoperative biopsy in all cases. A palpable tumor adjacent to a previous surgery scar is therefore a warning that it might represent a granuloma, in spite of various image findings.

Large-scale gene expression profiles, differentially represented in osteoarthritic synovium of the knee joint using cDNA microarray technology

Osteoarthritis (OA) is one of the most common age-related chronic disorders of articular cartilage, joints and bone tissue. Diagnosis of OA commonly depends on clinical and radiographic findings. However, changes in cartilage associated with the early stage of OA cannot be detected using radiographs, because significant cartilage degeneration must occur before radiographic findings show alterations of the appearance of cartilage. To identify new biomarkers of OA, we analysed gene expression profiles of synovium from 43 patients with OA, ten patients with rheumatoid arthritis (RA), and eight non-OA/non-RA patients using a novel cDNA microarray chip. We identified 21 genes with simultaneous significant differences in expression between OA and non-OA/non-RA groups and between OA and RA groups. Linear discriminant analysis showed that the three groups could be well separated using those 21 genes. Statistical analysis also revealed that several of the 21 genes were associated with disease progression and clinical presentation. The graphical modelling method indicated that some of the 21 genes are significantly associated with a particular clinical presentation, suggesting biological relationships among those genes. This is the first report of the use of cDNA microarray technology to create large-scale gene expression profiles differentially expressed in situ in OA synovium of the knee joint.

Quality of life in children with osteosarcoma after limb salvage operation

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Background: There are several options for the surgical management of osteosarcoma (OS) especially in the skeletally immature patients. We evaluate the clinical results and quality of life (QOL) of OS patients with limb salvage operations. Methods: From 1996 to 2005, ten children with newly diagnosed previously untreated nonmetastatic (stage IIB) OS of extremities were reviewed. There were 5 females and 5 males. The median age was 12 years (range, 8 to 14). Tumor locations: proximal humerus in 2, proximal femur in 1, distal femur in 2, proximal tibia in 3, distal tibia in 1, and tibial shaft in 1. Patients received neoadjuvant and adjuvant chemotherapy, and local wide resection of tumor. Limb salvage procedures: intraoperative extracorporeal autogenous irradiated bone graft (IORBG) in 4 and prosthetic replacement in 6. The functional results were measured for the patients accordance with the Musculoskeletal Tumor Society rating score. Results: With a median follow up of 4 years (range, 1 to 9), 7 were continuously disease free, 2 died of disease and in one there was no evidence of disease. No local recurrence was seen. Mean functional rating scores of patients with IORBG and prosthetic replacement were 82% (range 77 to 90) and 82% (range 57 to 93), respectively. Functional results were not different between these study groups and relatively good. There was one infection in patients with prosthetic replacement. There were subchondral collapse in 2 (50%), fracture in 1 (25%) and infection in 1 (25%) with IORBG. Conclusions: Limb salvage operation with neoadjuvant chemotherapy is the optimum treatment. However there remain several problems of function after limb salvage operations, with improvement of survival of pediatric osteosarcoma patient. We should select the most suitable surgical procedure to achieve the good function of limbs as well as local control.

No significant financial relationships to disclose.

Clear cell sarcoma of tendons and aponeuroses: An analysis of 75 cases

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Background: Clear cell sarcoma (CCS) of tendons and aponeuroses is a rare malignant tumor that occurs most commonly in the extremities of young adults. Because of the rarity of the disease (1% of all soft tissue sarcomas), most reports about CCS have dealt with a few cases during a long time period. We conducted a multi-institutional study of CCS to clarify the clinical findings and prognostic factors of CCS treated during the era of modern multidisciplinary treatment. Methods: The records of 75 consecutive patients with histologically confirmed CCS treated at the JMOG affiliated institutions between 1980 and 2004 (follow-up; average 44 months) were reviewed. There were 41 men and 34 women with an average age of 36 years (range, 10–71 years). 65 tumors were in the extremities (foot 22, hand 13, thigh 9, others 21) and 10 were in the trunk. The tumor size ranged from 1 to 11 cm (mean, 4 cm). 52 patients presented with localized disease (M0) and 23 with metastatic disease (M1). Results: Surgical excision of the primary tumor was performed in 71 patients (limb-sparing surgery; 56, amputation; 15). Microscopic surgical margin was negative in 60 and positive in 11. 56 patients received chemotherapy (30 with measurable disease) and 17 had radiotherapy. Local recurrence occurred in 16 patients and 48 patients developed metastasis. The 5-year overall survival rate was 47% (M0; 55%, M1; 20%). On univariate analysis, sex (p=0.02), size (p=0.001), depth (p=0.002), TNM stage (p=0.001), IRS group (p=0.001) and surgical margin (p=0.04) were prognostic factors. On multivariate analysis, size (p=0.02) remained to be a significant prognostic factor. Objective response to chemotherapy was observed in 8 (27%) patients. In the group of M0 patients, those who received adjuvant chemotherapy had better prognosis (5-year survival, 65%) than those without chemotherapy (5-year survival, 23%)(p=0.03). Conclusions: The results support the contention that early diagnosis and initial excision with negative surgical margin are essential for favorable outcome of CCS. The role of chemotherapy for CCS should be further investigated.

No significant financial relationships to disclose.

Soft-tissue sarcoma mimicking large haematoma: a report of two cases and review of the literature

We report on 2 patients with soft-tissue sarcomas mimicking large haematomas. Neither patient had a medical history of trauma or bleeding tendency. In a patient with a large leiomyosarcoma in the buttock, insufficient biopsy material from initial surgeries precluded a correct diagnosis. In the second patient with epithelioid sarcoma of the forearm, fasciotomy was repeatedly performed for compartment syndrome arising from the tumour. It is important to reconfirm prior trauma and investigate the clinical course and images of patients with an unusual history of haematoma in the extremities. The possibility of a malignant tumour should be suspected, and repeated biopsies should be performed if necessary.

Intraneural metastasis of a synovial sarcoma to a peripheral nerve

We describe a case of intraneural metastasis of a synovial sarcoma, the first published case of a metastasis of a soft-tissue sarcoma to a peripheral nerve.

Intraneural metastasis of a synovial sarcoma to a peripheral nerve

We describe a case of intraneural metastasis of a synovial sarcoma, the first published case of a metastasis of a soft-tissue sarcoma to a peripheral nerve.

Calcium hydroxyapatite ceramic implants in bone tumour surgery. A long-term follow-up study

We reviewed the results of 51 patients with benign bone tumours treated by curettage and implantation of calcium hydroxyapatite ceramic (CHA). The mean follow-up was 11.4 years (10 to 15.5). Post-operative fractures occurred in two patients and three had local recurrences; three had slightly limited movement of the adjacent joint and one had mild osteoarthritis. There were no allergic or neoplastic complications. In all cases, radiographs showed that the CHA was well incorporated into the host bone. Statistical analysis showed that absorption of the implanted CHA was greater in males (odds ratio, 6.2; 95% CI, 1.6 to 23.7) and younger patients (odds ratio, 0.6 for increase in age of 10 years; 95% CI, 0.91 to 0.99). However, the implanted CHA was not completely absorbed in any patient. We conclude that CHA is a useful and safe bone substitute for the treatment of benign bone tumours.

The expression and prognostic significance of bone morphogenetic protein-2 in patients with malignant fibrous histiocytoma

We investigated the rates of expression of bone morphogenetic protein-2 (BMP-2) in 29 adult patients with high-grade malignant fibrous histiocytoma of soft tissue, using the BMP-2-specific monoclonal antibody, AbH3b2/17, and found that they ranged from 1.9% to 78.9%. The survival at five years of the groups expressing high (≥30%) and low (< 30%) levels of BMP-2 was 85.7% and 36.3%, respectively. Multivariable analysis showed that only BMP-2 had prognostic significance for continuous disease-free survival and for overall survival (p < 0.05). Our findings indicate that over-expression of BMP-2 in malignant fibrous histiocytoma of soft tissue is the most reliable prognostic indicator of the parameters assessed.

The expression and prognostic significance of bone morphogenetic protein-2 in patients with malignant fibrous histiocytoma

We investigated the rates of expression of bone morphogenetic protein-2 (BMP-2) in 29 adult patients with high-grade malignant fibrous histiocytoma of soft tissue, using the BMP-2-specific monoclonal antibody, AbH3b2/17, and found that they ranged from 1.9% to 78.9%. The survival at five years of the groups expressing high (> or = 30%) and low (< 30%) levels of BMP-2 was 85.7% and 36.3%, respectively. Multivariable analysis showed that only BMP-2 had prognostic significance for continuous disease-free survival and for overall survival (p < 0.05). Our findings indicate that over-expression of BMP-2 in malignant fibrous histiocytoma of soft tissue is the most reliable prognostic indicator of the parameters assessed.

The colorectal tumour suppressor APC is present in the NMDA-receptor-PSD-95 complex in the brain

BACKGROUND

The synaptic protein PSD-95/SAP90 interacts with ion channels such as the N-methyl-D-aspartate-receptor (NMDA-R) via its PDZ domain, and is involved in their clustering. Moreover, it interacts with signalling molecules and plays an important role in coupling NMDA-R to pathways that control synaptic plasticity and learning.

RESULTS

We report that PSD-95 interacts with the adenomatous polyposis coli (APC) tumour suppressor protein via its PDZ domain. Furthermore, we found that PSD-95, NMDA-R and APC are contained in the same complex in vivo. PSD-95-NMDA-R-APC association was found to require two cysteine residues conserved in the amino-terminus of PSD-95 that are known to be critical for its multimerization.

CONCLUSION

Our findings suggest that the PSD-95-NMDA-R-APC complex forms due to the multimerization of PSD-95 monomers, each of which can associate with either NMDA-R or APC. It is possible that APC is involved in the regulation of ion channel clustering and/or organization of signalling molecules.

SYT-SSX fusion proteins in synovial sarcomas: detection and characterization with new antibodies

To identify and characterize the SYT-SSX fusion proteins in synovial sarcomas, we developed two polyclonal antibodies against the N-terminal part and for the C-terminal part of the SYT-SSX2 protein. Specificity was demonstrated on COS-7 cells transfected with two subtypes of SYT-SSX fusion genes, SYT-SSX1 and SYT-SSX2. Both antibodies recognized a single protein of 61 kDa in an immunoprecipitation of the transfected COS-7 cell lysates. These antibodies also detected the native protein of 61 kDa in the lysate of a human synovial sarcoma cell line (HS-SY41) with immunoprecipitation, and in extracts of human synovial sarcomas with western blot analysis. An immunohistochemical study, using human synovial sarcoma tissues, demonstrated that the SYT-SSX fusion proteins localized in the nucleus of the tumor cells. These antibodies provide a useful method for studying the expression of the SYT-SSX fusion proteins.

The APC-hDLG complex negatively regulates cell cycle progression from the G0/G1 to S phase

The adenomatous polyposis coli (APC) gene is mutated in familial adenomatous polyposis and in many sporadic colorectal tumors. The carboxyl-terminal S/TXV motif of the APC gene product interacts with the PDZ domain of hDLG, the human homolog of the Drosophila lethal (1) discs larige-1 (dlg) tumor suppressor. In the present study, we found that overexpression of hDLG suppresses cell proliferation by blocking cell cycle progression from the G0/G1 to S phase. This inhibition of cell cycle progression was abolished when the PDZ, SH3 or guanylate kinase-like domain of hDLG was mutated. Moreover, overexpression of these mutant hDLGs partially interfered with the cell cycle blocking activity of APC. Consistent with this result, mutant APC lacking the S/TXV motif exhibited weaker cell cycle blocking activity than the intact APC. These results suggest that APC-hDLG complex formation plays an important role in transducing the APC cell cycle blocking signal.

Localization of MCC (mutated in colorectal cancer) in various tissues of mice and its involvement in cell differentiation

Localization of the MCC (mutated in colorectal cancer) gene product, a cell cycle-regulating protein mutated in several colorectal tumors, in various mouse tissues was examined by immunohistochemistry and immunoelectron microscopy. MCC was localized on microvilli and in the apical cytoplasm in renal proximal tubule epithelial cells and pancreatic acinar cells. In hepatocytes, MCC was exclusively detected on microvilli. MCC was highly expressed in the cerebral cortex and the molecular layer of the cerebellar cortex and was partially associated with membrane organelles in neuronal elements. Adrenal chromaffin cells showed little expression of MCC. MCC was localized to the cell margins of ependymal cells, thyroid follicular cells, and anterior pituitary cells. In parotid acinar cells, only the apical surface was immunopositive. MCC was not expressed in skeletal and cardiac muscle. MCC was present at lateral cell borders in the duodenum and colon epithelium. In addition, the apical cytoplasm of colon epithelial cells exhibited intense immunoreactivity. The amount of MCC increased during differentiation of NGF-treated PC12 cells. In conclusion, MCC was expressed in differentiated cells and was associated with the plasma membrane and membrane organelles. In addition to the negative regulation of the cell cycle, MCC may be involved in cell differentiation.

Localization of the adenomatous polyposis coli tumour suppressor protein in the mouse central nervous system

The adenomatous polyposis coli gene is mutated in familial adenomatous polyposis and in sporadic colorectal tumours. The adenomatous polyposis coli gene product is a 300,000 mol. wt cytoplasmic protein that binds to at least three other proteins; beta-catenin, a cytoplasmic E-cadherin-associated protein; hDLG, a human homologue of the Drosophila discs large tumour suppressor protein and glycogen synthase kinase 3 beta, a mammalian homologue of the Drosophila ZESTE WHITE 3 protein. The adenomatous polyposis coli gene is highly expressed in the brain, suggesting that it may be involved in nerve function. Here we show that adenomatous polyposis coli is localized in the pericapillary astrocytic endfeet throughout the mouse central nervous system. Adenomatous polyposis coli is also localized in the astrocytic processes in the cerebellar granular layer, and displays concentrated expression in the terminal plexuses of the basket cell fibres around Purkinje cells. Adenomatous polyposis coli is further expressed in neuronal cell bodies and/or nerve fibres in the olfactory bulb, hippocampus, brain stem, spinal cord and dorsal root ganglia. Adenomatous polyposis coli is demonstrated to be co-localized with beta-catenin and/or hDLG in neurons and nerve fibres, but not in astrocytes. From these results, adenomatous polyposis coli is suggested to participate in a signal transduction pathway in astrocytes which is independent of beta-catenin and hDLG, and also in regulation of neuronal functions in association with beta-catenin and hDLG.

DAP-1, a novel protein that interacts with the guanylate kinase-like domains of hDLG and PSD-95

BACKGROUND

The human homologue of the Drosophila discs large tumour suppressor protein (hDLG) and closely related proteins such as postsynaptic density protein 95 kDa (PSD-95) are associated with N-methyl-D-aspartate receptors (NMDA-R) and Shaker-type K+ channels, and are thought to be involved in their clustering.

RESULTS

We have identified a protein named DAP-1 that binds to the guanylate kinase-like domains of hDLG and PSD-95. DAP-1 was found to associate with hDLG, PSD-95, NMDA-R and adenomatous polyposis coli protein (APC). Furthermore, we found that DAP-1 is specifically expressed in the brain and colocalizes with PSD-95 and APC in mouse cerebellum. We also found that DAP-1 is colocalized with PSD-95 and NMDA-R at the synapses in cultured rat hippocampal neurons.

CONCLUSION

Our findings suggest that DAP-1 may play several roles in the molecular organization of synapses and neuronal cell signalling by interacting with hDLG and PSD-95, which in turn are associated with receptors, ion channels and APC.

The tumor suppressor protein APC colocalizes with beta-catenin in the colon epithelial cells

The APC gene is mutated in familial adenomatous polyposis and sporadic colorectal tumors. The product of this gene is a 300 kDa cytoplasmic protein associated with catenin. In the present study, we examined the subcellular localization of the APC protein and beta-catenin in the mouse colon by double-labeling immunocytochemistry. While the APC protein was localized in the lateral and apical cytoplasm and in microvilli of the epithelial cells, beta-catenin was present exclusively in the lateral cytoplasm. Double-labeling-immunoelectron microscopy demonstrated precise colocalization of the APC protein and beta-catenin along the lateral plasma membrane. These results suggest that the APC protein functions in cooperation with beta-catenin in the lateral cytoplasm but has other functions independent of beta-catenin in the apical cytoplasm and in microvilli.

Binding of APC to the human homolog of the Drosophila discs large tumor suppressor protein

The adenomatous polyposis coli gene (APC) is mutated in familial adenomatous polyposis and in sporadic colorectal tumors, and its product binds to the adherens junction protein beta-catenin. Overexpression of APC blocks cell cycle progression. The APC-beta-catenin complex was shown to bind to DLG, the human homolog of the Drosophila discs large tumor suppressor protein. This interaction required the carboxyl-terminal region of APC and the DLG homology repeat region of DLG. APC colocalized with DLG at the lateral cytoplasm in rat colon epithelial cells and at the synapse in cultured hippocampal neurons. These results suggest that the APC-DLG complex may participate in regulation of both cell cycle progression and neuronal function.

MCC, a cytoplasmic protein that blocks cell cycle progression from the G0/G1 to S phase

The MCC gene was isolated from the human chromosome 5q21 by positional cloning and was found to be mutated in several colorectal tumors. In this study, we prepared specific antibodies and detected the MCC gene product as a cytoplasmic 100-kDa phosphoprotein in mouse NIH3T3 cells. Immunoelectron microscopic analysis showed that the MCC protein is associated with the plasma membrane and membrane organelles in mouse intestinal epithelial cells and neuronal cells. The amount of the MCC protein remained constant during the cell cycle progression of NIH3T3 cells, while its phosphorylation state changed markedly in a cell cycle-dependent manner, being weakly phosphorylated in the G0/G1 and highly phosphorylated during the G1 to S transition. Overexpression of the MCC protein blocked the serum-induced cell cycle transition from the G1 to S phase, whereas a mutant MCC, initially identified in a colorectal tumor, did not exhibit this activity. These results suggest that the MCC protein may play a role in the signaling pathway negatively regulating cell cycle progression.

[Characterization of the MCC gene product]

MCC is a gene located within human chromosome band 5q21 that shows somatically acquired mutations in colorectal cancer. Here we report the identification, tissue specific distribution, subcellular localization, and growth regulating activity of MCC protein. Immunohistochemical analysis of MCC protein in various tissues of mouse revealed heavy cytoplasmic staining of brain neuronal cells and intestinal epithelial cells. Ectopic expression of the MCC gene by microinjection in normal NIH3T3 cell lines leads to inhibition of DNA synthesis. These studies provide some initial clues to the function of the MCC protein and demonstrate that it negatively controls the cell cycle progression.

Isolation and mapping of a human gene (RPD3L1) that is homologous to RPD3, a transcription factor in Saccharomyces cerevisiae

We have isolated a novel human gene RPD3L1, that is highly homologous to a transcription factor in Saccharomyces cerevisiae, RPD3 (reduced potassium dependency 3), from a human fetal lung cDNA library. The cDNA clone, hRPD3, consists of 2,100 nucleotides that contain an open reading frame of 1446 nucleotides encoding 482 amino acids. It shares 62% identity in nucleotide sequence and 52% identity in amino acid sequence to RPD3. This gene is expressed at various levels in all tissues examined. Furthermore, we were able to map it to chromosome band 1p34.1 by FISH.

The tumour suppressor gene product APC blocks cell cycle progression from G0/G1 to S phase

The APC gene is mutated in familial adenomatous polyposis (FAP) as well as in sporadic colorectal tumours. The product of the APC gene is a 300 kDa cytoplasmic protein associated with the adherence junction protein catenin. Here we show that overexpression of APC blocks serum-induced cell cycle progression from G0/G1 to the S phase. Mutant APCs identified in FAP and/or colorectal tumours were less inhibitory and partially obstructed the activity of the normal APC. The cell-cycle blocking activity of APC was alleviated by the overexpression of cyclin E/CDK2 or cyclin D1/CDK4. Consistent with this result, kinase activity of CDK2 was significantly down-regulated in cells overexpressing APC although its synthesis remained unchanged, while CDK4 activity was barely affected. These results suggest that APC may play a role in the regulation of the cell cycle by negatively modulating the activity of cyclin-CDK complexes.

Constitutive overexpression of CDK2 inhibits neuronal differentiation of rat pheochromocytoma PC12 cells

Changes in the levels of cyclins A, D, and E, p21, and cyclin-dependent kinase 2 (CDK2) were examined in rat pheochromocytoma PC12 cells during neuronal differentiation induced by nerve growth factor (NGF). Expression of cyclin A decreased to an undetectable level after 5 days of exposure to NGF, while expression of CDK2 decreased gradually after day 3. In contrast, the levels of cyclins D1 and E increased gradually through day 10, yet the amount of cyclin E associated with CDK2 decreased concomitant with a decrease in the CDK2 protein level. p21 expression increased gradually after day 7, while the level of CDK2-associated p21 remained unchanged. When human cDNAs encoding cyclins and CDK2 were introduced into PC12 cells, only CDK2 overexpression inhibited NGF-induced differentiation. The cell lines overexpressing CDK2 showed stable and high levels of CDK2 kinase activity during differentiation, whereas parental and vector-transfected cell lines displayed a marked decline in CDK2 kinase activity 1 day after NGF treatment. In cell lines overexpressing cyclins A, D, and E, this reduction of the kinase activity was not apparent until day 3. These results suggest that down-regulation of CDK2 activity is a crucial event for the neuronal differentiation of PC12 cells.

Subcellular localization of the APC protein: immunoelectron microscopic study of the association of the APC protein with catenin

Mutations in the APC gene are linked to the development of sporadic colorectal tumors as well as to familial adenomatous polyposis. Recently, the APC protein was reported to associated with catenins, proteins that bind to the cell adhesion molecule E-cadherin. In the present study, we examined the distribution and localization of the APC protein and alpha -catenin in the normal mouse intestine by light and immunoelectron microscopy using specific antibodies. The APC protein was found to be localized in microvilli and in the apical and lateral cytoplasm of the epithelial cells, whereas alpha-catenin was detected only in the lateral cytoplasm. Double-labeling immunoelectron microscopy showed colocalization of the APC protein with alpha-catenin in the lateral cytoplasm, especially along the lateral plasma membrane, although a certain portion of the APC protein in this region was distributed independently of alpha-catenin. These results suggest that a portion of the APC protein localized in the lateral cytoplasm of intestinal epithelial cells functions in cooperation with catenins, whereas the APC protein in microvilli and in the apical cytoplasm has other functions independent of catenins.