Surgical treatment of acromioclavicular joint dislocation of Rockwood III/IV: a retrospective study on clavicular hook plate versus arthroscopic TightRope loop titanium button

PURPOSE

To compare the clinical efficacy of arthroscopic TightRope loop titanium button and clavicular hook plate in the treatment of acromioclavicular joint (ACJ) dislocation of Rockwood III/IV.

METHODS

A retrospective analysis of patients with ACJ dislocation in our hospital from January 2018 to December 2020 was conducted. The patients were assigned to be treated with arthroscopic TightRope loop titanium button (TR group) or clavicular hook plate (HP group). The preoperative, intraoperative and postoperative data and imaging findings of the two groups were compared.

RESULTS

A total of 58 eligible patients were enrolled in this study. Compared with HP group, TR group had shorter incision length and less blood loss during operation. Postoperative follow-up ranged from 12 to 24 months (mean 15.4 months). At 6 months and 12months postoperatively, compared with HP group, TR group had lower VAS and higher CMS, and the difference was statistically significant. At 12 months postoperatively, compared with HP group, TR group had lower ACJ gap and coracoclavicular joint(CCJ) distance, and the difference was statistically significant.In HP group, there were 3 cases of subacromial impact, 1 case of redislocation, 2 cases of traumatic arthritis and 2 cases of wound infection. There was 1 case of redislocation in TR group.

CONCLUSIONS

Compared with clavicular hook plate, arthroscopic TightRope loop titanium button is minimally invasive, safe and effective in the treatment of ACJ dislocation, and has a good trend in clinical application.

Melittin Treats Periprosthetic Osteolysis in a Rat Model by Inhibiting the NF-kB Pathway and Regulating the Ratio of Receptor Activator of Nuclear Factor Kappa B Ligand/Osteoprotegerin

BACKGROUND

Aseptic loosening around the prosthesis is a common cause of failure in total joint arthroplasty. Polyethylene wear particles trigger the release of inflammatory factors by macrophages. Key mediators involved in osteoclastogenesis include interleukin-6, tumor necrosis factor-α, receptor activator of nuclear factor kappa B (RANK), RANK ligand (RANKL), and bone protection hormone (Osteoprotegerin [OPG]). The purpose of our experiment was to see whether melittin can slow down the release of inflammatory mediators through the NF-kB pathway, regulate the RANKL/OPG ratio, reduce osteoclast formation, and delay the onset of arthritis in rats.

METHODS

A total of 20 male Sprague-Dawley rats (10 months, Specific Pathogen Free, 350 g ± 20 g) were randomly divided into 5 groups: sham group, model group, melittin concentration 1 group (0.2 mg/kg), concentration 2 group (0.4 mg/kg), and concentration 3 group (0.6 mg/kg). All rats were implanted with TA2 high-purity titanium rods. A drill was used to create a bone canal along the long axis of the femur in the intercondylar notch. The model group and experimental groups were exposed to polyethylene particles, while the sham group did not receive any particles.

RESULTS

The melittin group exhibited significantly increased serum levels of serum P, calcium-phosphorus product, OPG, PINP, PINP/CTX-I, and OPG/RANKKL (P < .05). In the experimental group, micro computed tomography scanning results revealed a decrease in the amount of bone defect around the prosthesis. Immunofluorescence analysis demonstrated a decrease in the expression of IKKα and P65, while the expression of OPG showed an upward trend. Both Hematoxylin-Eosin and Tartrate-Resistant Acid Phosphatase staining revealed less osteoclast and inflammatory cell infiltration in bone resorption pits.

CONCLUSIONS

Our study demonstrates that melittin has the ability to inhibit the NF-kB pathway in a rat model, and reduce the impact of RANKL/OPG, thereby delaying osteoclast activity and alleviating periprosthetic osteolysis.

Knockdown of PRMT1 suppresses the malignant biological behavior of osteosarcoma cells and increases cisplatin sensitivity via c-Myc-mediated BCAT1 downregulation

Increasing evidence indicated that protein arginine methyltransferase-1 (PRMT1) is an oncogene in multiple malignant tumors, including osteosarcoma (OS). The aim of this study was to investigate the underlying mechanism of PRMT1 in OS. The effects of PRMT1 or BCAT1, branched-chain amino acid transaminase 1 (BCAT1) on OS cell proliferation, invasion, autophagy, and apoptosis in vitro were examined. Moreover, molecular control of PRMT1 on c-Myc or transactivation of BCAT1 on c-Myc was assessed by chromatin immunoprecipitation and quantitative reverse transcription PCR assays. The effects of PRMT1 in vivo were examined with a xenograft tumor model. The results showed that PRMT1 was potently upregulated in OS tissues and cells. Upregulation of PRMT1 markedly increased OS cell proliferation and invasion in vitro and reduced cell apoptosis, whereas PRMT1 silencing showed the opposite effects. Cisplatin, one of the most effective chemotherapeutic drugs, improved cell survival rate by inducing the expression of PRMT1 to downregulate the cisplatin sensitivity. Meanwhile, the cisplatin-induced upregulation of PRMT1 expression caused dramatically autophagy induction and autophagy-mediated apoptosis by inactivating the mTOR signaling pathway, which could be reversed by 3-methyladenine, an autophagy inhibitor, or PRMT1 silencing. PRMT1 could activate c-Myc transcription and increase c-Myc-mediated expression of BCAT1. Furthermore, BCAT1 overexpression counteracted the effects of PRMT1 knockdown on cell proliferation, invasion, and apoptosis. Of note, deficiency of PRMT1 suppressed tumor growth in vivo. PRMT1 facilitated the proliferation and invasion of OS cells, inhibited cell apoptosis, and decreased chemotherapy sensitivity through c-Myc/BCAT1 axis, which may become potential target in treating OS.

The hydroxyapatite modified 3D printed poly L-lactic acid porous screw in reconstruction of anterior cruciate ligament of rabbit knee joint: a histological and biomechanical study

BACKGROUND

3D printing technology has become a research hotspot in the field of scientific research because of its personalized customization, maneuverability and the ability to achieve multiple material fabrications. The focus of this study is to use 3D printing technology to customize personalized poly L-lactic acid (PLLA) porous screws in orthopedic plants and to explore its effect on tendon-bone healing after anterior cruciate ligament (ACL) reconstruction.

METHODS

Preparation of PLLA porous screws with good orthogonal pore structure by 3D printer. The hydroxyapatite (HA) was adsorbed on porous screws by electrostatic layer-by-layer self-assembly (ELSA) technology, and PLLA-HA porous screws were prepared. The surface and spatial morphology of the modified screws were observed by scanning electron microscopy (SEM). The porosity of porous screw was measured by liquid displacement method. Thirty New Zealand male white rabbits were divided into two groups according to simple randomization. Autologous tendon was used for right ACL reconstruction, and porous screws were inserted into the femoral tunnel to fix the transplanted tendon. PLLA group was fixed with porous screws, PLLA-HA group was fixed with HA modified porous screws. At 6 weeks and 12 weeks after surgery, 5 animals in each group were sacrificed randomly for histological examination. The remaining 5 animals in each group underwent Micro-CT and biomechanical tests.

RESULTS

The pores of PLLA porous screws prepared by 3D printer were uniformly distributed and connected with each other, which meet the experimental requirements. HA was evenly distributed in the porous screw by ELSA technique. Histology showed that compared with PLLA group, mature bone trabeculae were integrated with grafted tendons in PLLA-HA group. Micro-CT showed that the bone formation index of PLLA-HA group was better than that of PLLA group. The new bone was uniformly distributed in the bone tunnel along the screw channel. Biomechanical experiments showed that the failure load and stiffness of PLLA-HA group were significantly higher than those of PLLA group.

CONCLUSIONS

The 3D printed PLLA porous screw modified by HA can not only fix the grafted tendons, but also increase the inductivity of bone, promote bone growth in the bone tunnel and promote bone integration at the tendon-bone interface. The PLLA-HA porous screw is likely to be used in clinic in the future.

Additive Effect of Parathyroid Hormone and Zoledronate Acid on Prevention Particle Wears-Induced Implant Loosening by Promoting Periprosthetic Bone Architecture and Strength in an Ovariectomized Rat Model

Implant-generated particle wears are considered as the major cause for the induction of implant loosening, which is more susceptible to patients with osteoporosis. Monotherapy with parathyroid hormone (PTH) or zoledronate acid (ZOL) has been proven efficient for preventing early-stage periprosthetic osteolysis, while the combination therapy with PTH and ZOL has exerted beneficial effects on the treatment of posterior lumbar vertebral fusion and disuse osteopenia. However, PTH and ZOL still have not been licensed for the treatment of implant loosening to date clinically. In this study, we have explored the effect of single or combined administration with PTH and ZOL on implant loosening in a rat model of osteoporosis. After 12 weeks of ovariectomized surgery, a femoral particle-induced periprosthetic osteolysis model was established. Vehicle, PTH (5 days per week), ZOL (100 mg/kg per week), or combination therapy was utilized for another 6 weeks before sacrifice, followed by micro-CT, histology, mechanical testing, and bone turnover examination. PTH monotherapy or combined PTH with ZOL exerted a protective effect on maintaining implant stability by elevating periprosthetic bone mass and inhibiting pseudomembrane formation. Moreover, an additive effect was observed when combining PTH with ZOL, resulting in better fixation strength, higher periprosthetic bone mass, and less pseudomembrane than PTH monotherapy. Taken together, our results suggested that a combination therapy of PTH and ZOL might be a promising approach for the intervention of early-stage implant loosening in patients with osteoporosis.

A network pharmacology approach to determine the underlying mechanisms of action of Yishen Tongluo formula for the treatment of oligoasthenozoospermia

Oligoasthenozoospermia is a complex disease caused by a variety of factors, and its incidence is increasing yearly worldwide. Yishen Tongluo formula (YSTLF), created by Professor Sun Zixue, has been used to treat oligoasthenozoospermia in clinical practice for several decades with a good therapeutic effect. However, the chemical and pharmacological profiles of YSTLF remain unclear and need to be elucidated. In this study, a network pharmacology approach was applied to explore the potential mechanisms of YSTLF in oligoasthenozoospermia treatment. All of the compounds in YSTLF were retrieved from the corresponding databases, and the bioactive ingredients were screened according to their oral bioavailability (OB) and drug-likeness (DL). The potential proteins of YSTLF were obtained from the traditional Chinese medicine systems pharmacology (TCMSP) database and the Bioinformatics Analysis Tool for Molecular Mechanism of Traditional Chinese Medicine (BATMAN-TCM) database, while the potential genes of oligoasthenozoospermia were obtained from the GeneCards database and the DisGeNET database. The STRING database was used to construct an interaction network according to the common targets identified by the online tool Venny for YSTLF and oligoasthenozoospermia. The topological characteristics of nodes were visualized and analyzed through Cytoscape. Biological functions and significant pathways were determined and analyzed using the Gene Ontology (GO) knowledgebase, the Kyoto Encyclopedia of Genes and Genomes (KEGG) and Metascape. Finally, the disease-formula-compound-target-pathway network was constructed by Cytoscape. A total of 106 bioactive ingredients and 134 potential targets from YSTLF were associated with oligoasthenozoospermia or considered to be therapeutically relevant. Pathway analysis indicated that the PI3K/Akt, MAPK and apoptosis signaling pathways were significant pathways involved in oligoasthenozoospermia. In conclusion, the current study expounded the pharmacological actions and molecular mechanisms of YSTLF in treating oligoasthenozoospermia from a holistic viewpoint. The potential molecular mechanisms were closely related to antioxidative stress, antiapoptosis and anti-inflammation, with TNF, CCND1, ESR1, NFKBIA, NR3C1, MAPK8, and IL6 being possible targets. This network pharmacology prediction may offer a helpful tool to illustrate the molecular mechanisms of the Chinese herbal compound YSTLF in oligoasthenozoospermia treatment.

Genome sequencing of pancreatic cancer: differential expression by location

The results demonstrated that pancreatic ductal carcinoma (PDAC) of the body/tail was associated with more transcriptional and genomic changes, and correlated with worse prognosis, than PDAC of the pancreatic head. The different mutation types and gene expression of tumour locations provide deep insight into the carcinogenesis or metastasis of PDAC, and suggest different early diagnostic and therapeutic strategies. SNV, single-nucleotide variations; NLS, Nuclear localization sequence; MB, million base-pairs; UTR, untranslated region.

Anterior cruciate ligament reconstruction in a rabbit model using a silk-collagen scaffold modified by hydroxyapatite at both ends: a histological and biomechanical study

Background

To investigate osteointegration at the graft-bone interface and the prevention of osteoarthritis after anterior cruciate ligament (ACL) reconstruction using a silk-collagen scaffold with both ends modified by hydroxyapatite (HA) in a rabbit model.

Methods

The HA/silk-collagen scaffold was fabricated using a degummed, knitted silk scaffold, collagen I matrix, and simulated body fluid (SBF). The HA/silk-collagen scaffold was rolled up to make a graft for replacing the native ACL in the experimental group (HA group), and the silk-collagen scaffold was used in the control (S group). All specimens were harvested at 16 weeks postoperatively to evaluate graft-bone healing and osteoarthritis prevention.

Results

Histological staining revealed the massive formation of more mature bone at the tendon-bone interface, and immunohistochemistry staining revealed more collagen I and osteocalcin deposition in the HA group than in the S group. Higher signals indicating more bone mineral formation were detected in the HA group than in the S group, which was consistent with the results of biomechanical testing. Better osteoarthritis prevention was also observed in the HA group, indicating a more stable knee joint in the HA group than in the S group.

Conclusion

The HA/silk-collagen scaffold promotes osteointegration at the tendon-bone interface after ACL reconstruction and has great potential for clinical applications.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13018-021-02281-0.

Combination of platelet-rich plasma and bone marrow mesenchymal stem cells enhances tendon-bone healing in a rabbit model of anterior cruciate ligament reconstruction

Background

The objective of this study was to investigate the potency of platelet-rich plasma (PRP) combined with bone marrow mesenchymal stem cells (BMSCs) to promote tendon–bone healing in a rabbit model.

Methods

In the in vitro study, the effects of PRP on osteogenic induction of BMSCs were analysed. Later, PRP with or without BMSCs was used in the rabbit model of anterior cruciate ligament reconstruction. Specimens were harvested 8 weeks postoperatively to evaluate tendon–bone healing by histology, radiology, and biomechanical testing.

Results

The in vitro study revealed that collagen I, osteocalcin, and osteopontin expression was higher in BMSCs co-cultured with PRP for 14 days. The in vivo study revealed a more mature tendon–bone interface using light microscopy, a more newly formed bone at the bone tunnel walls detected by micro-computed tomography, and a significantly higher failure load as assessed by biomechanical testing in the BMSC + PRP group than in the control and PRP groups.

Conclusions

These results indicate that the combination of PRP and BMSCs promotes tendon–bone healing and has potential for clinical use.

Electronic supplementary material

The online version of this article (doi:10.1186/s13018-016-0433-7) contains supplementary material, which is available to authorized users.

SeMet mediates anti-inflammation in LPS-induced U937 cells targeting NF-κB signaling pathway

In previous studies, selenium (Se) was reported to play critical roles in anti-inflammatory activities. Nevertheless, limited information could be obtained during inflammation about selenomethionine (SeMet) in U937 human macrophage cells. The purpose of this study was to investigate the effects of SeMet on the inflammatory responses to lipopolysaccharide (LPS)-induced U937 macrophage cells and the signaling pathways targeted. U937 cells were pretreated with SeMet (1 μM) and subsequently induced with LPS (1 μg/ml) for 24 h. In the cell counting kit-8 assay (CCK-8), SeMet significantly inhibits the proliferation of U937 cells. SeMet also inhibited the production of nitric oxide (NO) and prostaglandin E2 (PGE2) stimulated by LPS. In the Western blot assay and real-time polymerase chain reaction (RT-PCR), SeMet significantly reduced protein expression and production of inducible NO synthase (iNOS), tumor necrosis factor-alpha (TNF-α), and COX-2 in U937 cells. Furthermore, SeMet markedly suppressed the LPS-mediated activation of nuclear factor-kappa B (NF-κB) by blocking the degradation of inhibitor-κB proteins (IκBα) and lessening the translocations of P50 subunit content of NF-κB in the nucleus. These findings suggested the anti-inflammatory activity of SeMet in U937 cells; indicating that SeMet might be a potential treatment for inflammation therapy.

Intermittent Administration of Parathyroid Hormone [1-34] Prevents Particle-Induced Periprosthetic Osteolysis in a Rat Model

We examined whether intermittent administration of parathyroid hormone [1-34] (PTH[1-34]; 60 μg/kg/day) can prevent the negative effects of titanium (Ti) particles on implant fixation and periprosthetic osteolysis in a rat model. Eighteen adult male rats (12 weeks old, bones still growing) received intramedullary Ti implants in their bilateral femurs; 6 rats from the blank group received vehicle injections, and 12 rats from the control group and PTH treatment group received Ti particle injections at the time of operation and intra-articular injections 2 and 4 weeks postoperatively. Six of the rats that received Ti particles from the PTH group also received PTH[1-34] treatment. Six weeks postoperatively, all specimens were collected for assessment by X-ray, micro-CT, biomechanical, scanning electron microscopy (SEM), and dynamic histomorphometry. A lower BMD, BV/TV, Tb.N, maximal fixation strength, and mineral apposition rate were observed in the control group compared to the blank group, demonstrating that a periprosthetic osteolysis model had been successfully established. Administration of PTH[1-34] significantly increased the bone mineral density of the distal femur, BV/TV, Tb.N, Tb.Th, Tb.Sp, Con.D, SMI, and maximal fixation strength in the PTH group compared to that in the control group. SEM revealed higher bone-implant contact, thicker lamellar bone, and larger trabecular bone area in the PTH group than in the control group. A higher mineral apposition rate was observed in the PTH group compared to both the blank and control groups. These findings imply that intermittent administration of PTH[1-34] prevents periprosthetic osteolysis by promoting bone formation. The effects of PTH[1-34] were evaluated at a suprapharmacological dosage to the human equivalent in rats; therefore, additional studies are required to demonstrate its therapeutic potential in periprosthetic osteolysis.

Effects of cartilage oligomeric matrix protein on bone morphogenetic protein-2-induced differentiation of mesenchymal stem cells

OBJECTIVE

To investigate the effect of overexpression of cartilage oligomeric matrix protein (COMP) on bone morphogenetic protein-2 (BMP-2) induced osteogenic and chondrogenic differentiation of mesenchymal stem cells (MSCs). In this study, we used liposomes to transfect MSCs with plasmid encoding COMP and then induced the transfected MSCs to differentiate in osteogenic and chondrogenic differentiation media containing BMP-2.

METHODS

MSCs transfected with plasmid DNA encoding recombinant human COMP were induced to differentiate into osteocytes and chondrocytes by BMP-2. Real-time polymerase chain reaction (PCR) assays of osteogenesis-related markers (collagen type I alpha 1, runt-related transcription factor 2, osteopontin, bone gla protein) and chondrogenesis-related markers (collagen type II alpha 1, sry-related high-mobility group box 9, Aggrecan) was performed to evaluate the process of cell differentiation. Cell differentiation was evaluated by alkaline phosphatase (ALP) and Alizarin red S stains for osteogenic differentiation and alcian blue staining for chondrogenic differentiation.

RESULTS

Real-time PCR assay showed significantly greater COMP expression by MSCs when COMP gene had been transfected into the cells (P < 0.01). Overexpression of COMP down-regulated expression of osteogenesis-related markers and up-regulated expression of chondrogenesis-related markers. ALP staining and Alizarin red S staining were weakened, whereas alcian blue staining was enhanced.

CONCLUSION

Overexpression of COMP inhibits BMP-2-induced osteogenic differentiation and promotes BMP-2-induced chondrogenic differentiation. These findings may provide new insights for cartilage tissue engineering. The experiments in the present study were all in vitro, which has potential limitations. Further in vivo studies to investigate the effects of COMP in animal models are necessary, which will be the next step in our research.

Anterior cruciate ligament reconstruction in a rabbit model using silk-collagen scaffold and comparison with autograft

The objective of the present study was to perform an in vivo assessment of a novel silk-collagen scaffold for anterior cruciate ligament (ACL) reconstruction. First, a silk-collagen scaffold was fabricated by combining sericin-extracted knitted silk fibroin mesh and type I collagen to mimic the components of the ligament. Scaffolds were electron-beam sterilized and rolled up to replace the ACL in 20 rabbits in the scaffold group, and autologous semitendinosus tendons were used to reconstruct the ACL in the autograft control group. At 4 and 16 weeks after surgery, grafts were retrieved and analyzed for neoligament regeneration and tendon-bone healing. To evaluate neoligament regeneration, H&E and immunohistochemical staining was performed, and to assess tendon-bone healing, micro-CT, biomechanical test, H&E and Russell-Movat pentachrome staining were performed. Cell infiltration increased over time in the scaffold group, and abundant fibroblast-like cells were found in the core of the scaffold graft at 16 weeks postoperatively. Tenascin-C was strongly positive in newly regenerated tissue at 4 and 16 weeks postoperatively in the scaffold group, similar to observations in the autograft group. Compared with the autograft group, tendon-bone healing was better in the scaffold group with trabecular bone growth into the scaffold. The results indicate that the silk-collagen scaffold has considerable potential for clinical application.

The external rotation immobilisation does not reduce recurrence rates or improve quality of life after primary anterior shoulder dislocation: a systematic review and meta-analysis

PURPOSE

Conducting a systematic review and meta-analysis of prospective randomised controlled trials directly comparing (1) the rates of recurrence and (2) patient-based quality-of-life assessments after the external rotation (ER) or internal rotation (IR) immobilisation after primary anterior shoulder dislocation.

METHODS

PubMed, EMBASE, the Cochrane Library and ISI Web of Science were searched up to January 2013, using the Boolean operators as follows: (bankart lesion OR shoulder anterior dislocation) AND ((external rotation AND internal rotation) OR immobilisation). All prospective randomised controlled trials directly comparing recurrence rate and patient-based quality-of-life assessments between the ER and IR immobilisations were retrieved. No limitation of the language or publication year existed in our analysis.

RESULTS

Seven of 896 studies involving 663 patients were included, 338 in the ER group and 325 in the IR group. No significant difference was observed in the recurrence rate at all ages (risk ratio (RR)=0.65; 95% confidence interval, 0.41-1.03; p=0.067), at the age stratum of ≤30 years (RR=0.70; 95% confidence interval, 0.38-1.29; p=0.250) and >30 years (RR=0.86; 95% confidence interval, 0.38-1.97; p=0.722). Four trials adopted quality-of-life assessments, using the Constant-Murlay functional scoring system, the Rowe scoring system, the Western Ontario Shoulder Instability index (WOSI), the Disabilities of arm, shoulder and hand (DASH) and the American Shoulder and Elbow Surgeons evaluation form (ASES). Only one trial demonstrated borderline statistical significance (p=0.05) and probable superiority of the ER group based on the ASES. No significant difference was observed in other three trials.

CONCLUSION

Based on the results of our analysis, the ER immobilisation could not reduce the rates of recurrence after primary anterior shoulder dislocation or improve the quality of life compared with the IR immobilisation. More rigorous and adequately powered prospective randomised controlled trials with long-term follow-ups are required to elucidate a more objective outcome.

Gemcitabine and capecitabine as third-line treatment in patients with metastatic colorectal cancer after failure of irinotecan and oxaliplatin

620

Background: There is no standard chemotherapeutic regimen for patients with advanced colorectal cancer (CRC) progressing after combination regimens including irinotecan and oxaliplatin and having good performance status. 5-FU and gemcitabine are synergistic in preclinical studies of colon cancer cells. And gemcitabine also increases intracellular release of 5-FU from capecitabine. The aim of this study is to evaluate the efficacy and tolerance of the gemcitabine/capecitabine combination as third-line treatment for patients with advanced colorectal cancer.

Methods: Between May 2007 and September 2009, the data on 12 patients with metastatic colorectal cancer after failure of irinotecan- and oxaliplatin-containing regimens reviewed retrospectively. The median patient age was 54.0 years (range 37-77). The ECOG performance status was 0, 1 or 2. All patients has 2 or more previous chemotherapy. Patients received GemCap regimen (oral capecitabine 1,000 mg/m2 twice daily on days 1 to 14 plus Gem 1,000 mg/m2 on days 1 and 8 every 3 weeks). Eleven patients were evaluable for the response and all patients were evaluable for toxicity.

Results: No partial response was achieved and disease stabilization in 4 (36.4.3%) cases. Median progression-free survival and median overall survival were 9.1 weeks (range 3.0-18.0) and 22.3 weeks (range 10.5- 53.0). Four patients with disease stabilization had longer median progression-free survival than those with disease progression (13 weeks vs. 6.2 weeks). No toxic deaths occurred. Grade 3 toxicities were thrombocytopenia (in 2 patients), neutropenia (in 2 patients) and mucositis (in 1 patient), hand-foot syndrome (in 1 patient) and GI toxicity (in 2 patients).

Conclusions: The combination of gemcitabine and capecitabine was found to be a safe palliative regimen for heavily pretreated patients with metastatic CRC. Despite no patients had radiologic response, patients with disease stabilization achieved better progression-free survival. This regimen seems to be potentially effective regimen in the treatment of CRC.

No significant financial relationships to disclose.

Reversion of the malignant phenotype of gastric cancer cell SGC7901 by c-erbB-2-specific hammerhead ribozyme

The c-erbB-2/neu-encoded protein p185 is closely related to the growth and metastasis of adenocarcinoma. We sought to reverse the malignant phenotype of gastric cancer cell line SGC7901 with c-erbB-2-specific ribozyme. We designed the ribozyme and generated the in vitro transcription vectors of the ribozyme and its substrate. In vitro cleavage reaction indicated that the ribozyme catalyzed 79.3% target RNA in 1 hour at 37 degrees C. Then, we generated the eucaryotic expression vectors of the ribozyme and transfected them into SGC7901 cells, which highly express p185. Analyses showed that the c-erbB-2 mRNA and p185 were reduced remarkably in the ribozyme-transfected cells. The growth rate of the ribozyme-transfected cells was much lower than that of the control group. Tumorigenicity was also decreased dramatically in nude mice. The results demonstrated that c-erbB-2-specific ribozyme may inhibit the malignancy of gastric cancer cells SGC7901.

Autoinhibition mechanism of proto-Dbl

The dbl oncogene encodes a prototype member of the Rho GTPase guanine nucleotide exchange factor (GEF) family. Oncogenic activation of proto-Dbl occurs through truncation of the N-terminal 497 residues. The C-terminal half of proto-Dbl includes residues 498 to 680 and 710 to 815, which fold into the Dbl homology (DH) domain and the pleckstrin homology (PH) domain, respectively, both of which are essential for cell transformation via the Rho GEF activity or cytoskeletal targeting function. Here we have investigated the mechanism of the apparent negative regulation of proto-Dbl imposed by the N-terminal sequences. Deletion of the N-terminal 285 or C-terminal 100 residues of proto-Dbl did not significantly affect either its transforming activity or GEF activity, while removal of the N-terminal 348 amino acids resulted in a significant increase in both transformation and GEF potential. Proto-Dbl displayed a mostly perinuclear distribution pattern, similar to a polypeptide derived from its N-terminal sequences, whereas onco-Dbl colocalized with actin stress fibers, like the PH domain. Coexpression of the N-terminal 482 residues with onco-Dbl resulted in disruption of its cytoskeletal localization and led to inhibition of onco-Dbl transforming activity. The apparent interference with the DH and PH functions by the N-terminal sequences can be rationalized by the observation that the N-terminal 482 residues or a fragment containing residues 286 to 482 binds specifically to the PH domain, limiting the access of Rho GTPases to the catalytic DH domain and masking the intracellular targeting function of the PH domain. Taken together, our findings unveiled an autoinhibitory mode of regulation of proto-Dbl that is mediated by the intramolecular interaction between its N-terminal sequences and PH domain, directly impacting both the GEF function and intracellular distribution.

Oligomerization of DH domain is essential for Dbl-induced transformation

The dbl oncogene product (onco-Dbl) is the prototype member of a family of guanine nucleotide exchange factors (GEFs) for Rho GTPases. The Dbl homology (DH) domain of onco-Dbl is responsible for the GEF catalytic activity, and the DH domain, together with the immediately adjacent pleckstrin homology (PH) domain, constitutes the minimum module bearing transforming function. In the present study, we demonstrate that the onco-Dbl protein exists in oligomeric form in vitro and in cells. The oligomerization is mostly homophilic in nature and is mediated by the DH domain. Mutagenesis studies mapped the region involved in oligomerization to the conserved region 2 of the DH domain, which is located at the opposite side of the Rho GTPase interacting surface. Residue His556 of this region, in particular, is important for this activity, since the H556A mutant retained the GEF catalytic capability and the binding activity toward Cdc42 and RhoA in vitro but was deficient in oligomer formation. Consequently, the Rho GTPase activating potential of the H556A mutant was significantly reduced in cells. The focus-forming and anchorage-independent growth activities of onco-Dbl were completely abolished by the His556-to-Ala mutation, whereas the abilities to stimulate cell growth, activate Jun N-terminal kinase, and cause actin cytoskeletal changes were retained by the mutant. The ability of onco-Dbl to oligomerize allowed multiple Rho GTPases to be recruited to the same signaling complex, and such an ability is defective in the H556A mutant. Taken together, these results suggest that oligomerization of onco-Dbl through the DH domain is essential for cellular transformation by providing the means to generate a signaling complex that further augments and/or coordinates its Rho GTPase activating potential.

[Reversion of the malignant phenotype of gastric cancer by c-erbB-2 specific ribozyme]

OBJECTIVE

To probe the effect of c-erbB-2 specific ribozyme to the malignant phenotype of gastric cancer.

METHODS

The eucaryotic expression vector of c-erbB-2 specific ribozyme RZ1 was designed by computer and named pDOR-RZ1. The transfection of the gastric cancer cell line SGC-7901 was mediated by Lipofect AMINE. Flow cytometry was used to analyse the expression of the c-erbB-2 product P185. In vivo study of tumorogenecity of the transfected cells was performed in nude mice.

RESULTS

pDOR-RZ1 was successfully transfected into the gastric cancer cell line SGC-7901 and then the single clones were selected by G418 and named SGC/RZ1. Flow cytometry analysis showed that the expression of P185 was suppressed by 62.7%. The growth rate of SGC/RZ1 was inhibited by 55%. The tumor-forming time in SGC/RZ1 in nude mice was delayed remarkably and the tumor size was also much smaller than that in the control group, indicating the inhibition of the tumorogenecity of SGC/RZ1 in nude mice.

CONCLUSION

c-erbB-2 specific ribozyme is very efficient in reversing the malignant phenotype of gastric cancer. This might provide a new approach for gene therapy of gastric cancer.

[In vitro cleavage action of c-erbB-2 oncogene-specific ribozyme]

OBJECTIVE

To construct in vitro transcription vectors of genes of c-erbB-2 specific ribozyme and its substrate and to probe its in vitro cleavage action.

METHODS

According to the computer design, a specific restriction site EcoR V was added to the 3' end of the ribozyme gene (RZ1). Then, the RZ1 gene and its substrate gene were cloned into the in vitro transcription vector pGEM3Zf(-) separately. The recombinants containing RZ1 gene were first screened by agrose ge1 electrophoresis through EcoR V digestion and was identified by automatic sequencing. The products of in vitro transcription were labeled with 32P. In vitro cleavage reaction was performed at 37 degrees C for 1 h under the presence of Mg++. The cleavage product was analyzed by polyacrilamide gel electrophoresis. After autoradiography, the cleavage rate was counted by image analysis.

RESULTS

The recombinants containing the RZ1 gene were successfully selected by the EcoR V digestion and were designated as pGM3Z-RZ1. The automatic sequence analysis proved that the synthesized RZ1 gene was correct. The target gene was also cloned into the pGEM3Zf(-) under SP6 promoter. After in vitro transcription, the cleavage reaction was shown to have cut off 79.3% target RNA in 1 h.

CONCLUSION

The c-erbB-2 oncogene-specific ribozyme has a high activity in vitro. It lays a foundation for the study of the therapeutic use of ribozyme in gene therapy of cancer.

[Analysis of the stereoisomers of 14 pyrethroids by capillary gas chromatography]

The separation of stereoisomers of 14 pyrethroids has been studied by capillary gas chromatography. The pyrethroids are cypermethrin (P1), phenothrin (P2), allethrin (P3), prallethrin (P4), tetramethrin (P5), permethrin (P6), cyfluthrin (P7), fenvalerate (P8), flucythrinate (P9), bromofenvalerate (P10), fluvalinate (P11), methothrin (P12), resmethrin (P13) and py115 (P14). The gas chromatographic conditions were as follows. Column 1: fused silica, 10m x 0.53mm x 1.0microm film (QF-1); columntemperature: 180 degrees C-260 degrees C depending on the pyrethroids analysed; the temperature of injector and detector: 280 degrees C; carrier gas: H2 4.6mL/min; detector: FID; spilt ratio: 5:1, sample size 1.0 L. The stereoisomers of P2, P3, P4, P5, P6, P8, P9, P10, P12 and P10 can be completely separated by QF-1 column. However the stereoisomers of P11 can not be separated and the three peaks of P1 and P7 have been only separated by column 1. In comparing with packed column of QF-1, there are advantages in superior resolution, lower oven temperature and shorter analysis time for capillary column of QF-1. Column 2: fused silica HP-5 (crosslinked 5% phenyl methyl silicone) 25m x 0.32mm x 1.0microm film; column temperature: P1 and P7 250 degrees C, P11 260 degrees C, and P14 200 degrees C; carrier gas: H2 2.6mL/min. Other conditions were the same as the column 1 described. The stereoisomers of P1, P7, P11 and P14 can be separated, but the separation of stereoisomers was not sufficient. The stereoisomers of P2, P5, P6, P8, P9, P10, P12 and P13 can be completely separated by HP-5 capillary column. However separation on the HP-5 capillary column is not sufficient for diastereoisomers of P3 and P4.