First peripheral drug-eluting stent clinical results from China: 1-year outcomes of the Zilver PTX China study.

Purpose: The benefit of using the Zilver PTX drug-eluting stent (DES) in superficial femoral artery (SFA) lesions has been demonstrated in multiple clinical studies. This prospective, multicenter study evaluated the 1-year safety and effectiveness of the DES for the treatment of femoropopliteal lesions in a Chinese patient population. Methods: Patients with a single de novo or restenotic SFA lesion ≤140 mm and a Rutherford classification of 2 to 4 were treated with the DES. The primary endpoint was primary patency assessed by duplex ultrasound at 1-year. Secondary endpoints included adverse events, event-free survival (EFS), and freedom from target lesion revascularization (TLR). Clinical outcomes included Rutherford classification, ankle-brachial index (ABI), and the walking impairment questionnaire (WIQ). Results: In this study, 178 patients with symptomatic peripheral artery disease were enrolled at nine institutions in China. The average lesion length was 79.0 ± 48.6 mm (range 14.8-245.4 mm) and 50.0% of lesions were total occlusions. The 1-year primary patency rate was 81.9%. Covariate analysis revealed that lesion length (p < 0.01) was the only significant factor for patency. No paclitaxel-related adverse events or amputations were reported. The 1-year rate for EFS was 94.9% and freedom from TLR was 95.5%. Through 1-year, treatment with the DES resulted in statistically significant improvement in ABI and WIQ scores compared with pre-procedure (p < 0.001). Clinical improvement of at least 1 Rutherford class was achieved in 142 of 174 patients (81.6%). Conclusion: This study showed promising short-term results for the treatment of SFA lesions with Zilver PTX DES in Chinese patients. Unique identifier: ClinicalTrials.gov, identifier: NCT02171962.

Prediction Model for Freedom from TLR from a Multi-study Analysis of Long-Term Results with the Zilver PTX Drug-Eluting Peripheral Stent.

PURPOSE: Develop a prediction model to determine the impact of patient and lesion factors on freedom from target lesion revascularization (ffTLR) for patients who are candidates for Zilver PTX drug-eluting stent (DES) treatment for femoropopliteal lesions. METHODS: Patient factors, lesion characteristics, and TLR results from five global studies were utilized for model development. Factors potentially associated with TLR (sex, age, diabetes, hypertension, hypercholesterolemia, renal disease, smoking status, Rutherford classification, lesion length, reference vessel diameter (RVD), popliteal involvement, total occlusion, calcification severity, prior interventions, and number of runoff vessels) were analyzed in a Cox proportional hazards model. Probability of ffTLR was generated for three example patient profiles via combinations of patient and lesion factors. TLR was defined as reintervention performed for ≥ 50% diameter stenosis after recurrent clinical symptoms. RESULTS: The model used records from 2227 patients. The median follow-up time was 23.9 months (range: 0.03-60.8). The Kaplan-Meier estimates for ffTLR were 90.5% through 1 year and 75.2% through 5 years. In a multivariate analysis, sex, age, Rutherford classification, lesion length, RVD, total occlusion, and prior interventions were significant factors. The example patient profiles have predicted 1-year ffTLRs of 97.4, 92.3, and 86.0% and 5-year predicted ffTLRs of 92.8, 79.5, and 64.8%. The prediction model is available as an interactive web-based tool ( https://cooksfa.z13.web.core.windows.net ). CONCLUSIONS: This is the first prediction model that uses an extensive dataset to determine the impact of patient and lesion factors on ffTLR through 5 years and provides an interactive web-based tool for expected patient outcomes with the Zilver PTX DES. CLINICAL TRIAL REGISTRATIONS: Zilver PTX RCT unique identifier: NCT00120406; Zilver PTX single-arm study unique identifier: NCT01094678; Zilver PTX China study unique identifier: NCT02171962; Zilver PTX US post-approval study unique identifier: NCT01901289; Zilver PTX Japan post-market surveillance study unique identifier: NCT02254837. LEVELS OF EVIDENCE: Zilver PTX RCT: Level 2, randomized controlled trial; Single-arm study: Level 4, large case series; China study: Level 4, case series; US post-approval study: Level 4, case series Japan PMS study: Level 4, large case series.

Long-Term Effectiveness of a Drug-Eluting Stent for Femoropopliteal In-Stent Restenosis: Subanalysis of the Zilver PTX Japan Post-Market Surveillance Study.

PURPOSE: To present a subgroup analysis of patients from a large real-world study evaluating the safety and effectiveness of the Zilver PTX drug-eluting stent (DES) for treating femoropopliteal in-stent restenosis (ISR). MATERIALS AND METHODS: This study examined patients enrolled in the Zilver PTX Japan Post-Market Surveillance Study (ClinicalTrials.gov identifier NCT02254837), a prospective, multicenter registry of 904 symptomatic patients with 1082 femoropopliteal lesions treated with the DES at 95 institutions in Japan. Five-year outcomes, including mortality, stent radiography, freedom from target lesion revascularization (TLR), and clinical benefit, were evaluated for 177 patients (mean age 74.2±8.3 years; 118 men) with 204 ISR lesions treated with the Zilver DES. Over half of the patients (108, 61.0%) were diabetic. Mean lesion length was 17.8±10.4 cm, and a third (72, 35.3%) were total occlusions. Outcome measures were all-cause mortality, thrombosis, freedom from TLR, and clinical benefit, defined as freedom from persistent or deteriorating ischemic symptoms. RESULTS: No device-related or procedure-related deaths or paclitaxel-related adverse events were reported. All-cause mortality was 25.1% at 5 years. Stent fracture was observed in 5 stents through 5 years. The 5-year rate of freedom from clinically-driven TLR was 73.4%, and the rate of clinical benefit was 63.6%. Improvement in Rutherford category and ankle-brachial index was sustained through 5 years. CONCLUSION: The safety and effectiveness of the Zilver PTX stent for the treatment of femoropopliteal ISR lesions demonstrated that this device provides a favorable treatment option in this difficult-to-treat subgroup.

Paclitaxel-Coated Zilver PTX Drug-Eluting Stent Treatment Does Not Result in Increased Long-Term All-Cause Mortality Compared to Uncoated Devices.

PURPOSE: Patient-level data from two large studies of the Zilver PTX drug-eluting stent (DES) with long-term follow-up and concurrent non-drug comparator groups were analyzed to determine whether there was an increased mortality risk due to paclitaxel. METHODS: Data from the Zilver PTX randomized controlled trial (RCT) and Zilver PTX and bare metal stent (BMS) Japan post-market surveillance studies were analyzed. Five-year follow-up is complete in both DES studies; follow-up for the BMS study was limited to 3 years and is complete. Kaplan-Meier analyses assessed mortality. A Cox proportional hazards model identified significant factors related to mortality. RESULTS: In the RCT, there were 336 patients treated with the DES and 143 patients treated with percutaneous transluminal angioplasty (PTA) or BMS. In Japan, there were 904 DES patients and 190 BMS patients. There was no difference in all-cause mortality for the DES compared to PTA/BMS in the RCT (19.1% DES versus 17.1% PTA/BMS through 5 years, p = 0.60) or Japan (15.8% DES versus 15.3% BMS through 3 years, p = 0.89). Cox proportional hazard models revealed that age, tissue loss, and congestive heart failure were significantly associated with mortality in the RCT, and critical limb ischemia, age, renal failure, and gender were significantly associated with mortality in Japan (all p < 0.05). Neither treatment with Zilver PTX (p = 0.46 RCT, p = 0.49 Japan) nor paclitaxel dose (p = 0.86 RCT, p = 0.07 Japan) was associated with mortality. CONCLUSION: Analyses of the Zilver PTX patient-level data demonstrated no increase in long-term all-cause mortality. LEVEL OF EVIDENCE: Zilver PTX RCT: Level 1, randomized controlled trial; Japan PMS studies: Level 3, post-market surveillance study.

Zilver PTX Post-market Surveillance Study of Paclitaxel-Eluting Stents for Treating Femoropopliteal Artery Disease in Japan: 2-Year Results.

PURPOSE: A prospective, multicenter post-market surveillance study in Japan evaluated the 2-year safety and effectiveness of the DES in real-world patients with complex femoropopliteal artery lesions. METHODS: There were no exclusion criteria, and consecutive symptomatic patients with femoropopliteal lesions treated with the DES were enrolled in the study. Clinically driven target lesion revascularization (TLR) was defined as reintervention performed for > 50% diameter stenosis after recurrent clinical symptoms of peripheral arterial disease. Clinical benefit was defined as freedom from persistent or deteriorating ischemic symptoms. Patency was evaluated by duplex ultrasound where physicians considered this standard of care. RESULTS: In this study, 905 patients were enrolled at 95 institutions in Japan. There were numerous comorbidities including a high incidence of diabetes (58.8%) and chronic kidney disease (43.6%). Additionally, 21.4% of patients were classified with critical limb ischemia. Lesions were complex, with an average length of 14.6 ± 9.6 cm (range 0.5-40 cm), 41.5% total occlusions, and 18.7% in-stent restenosis. In total, 1861 DES were placed in 1080 lesions. Two-year follow-up was obtained for > 90% of eligible patients. Freedom from TLR was 83.7%, and clinical benefit was 80.0% through 2 years. The 2-year primary patency rate was 70.3%. Rutherford classification significantly improved (p < 0.01), with approximately 80% of patients classified as Rutherford class 0 or 1 at 2 years. CONCLUSION: Despite more challenging lesion characteristics, 2-year results from the current study are similar to outcomes from the previous Zilver PTX studies, confirming the efficacy of the Zilver PTX DES in a complicated femoropopliteal lesion (Zilver PTX Post-Market Study in Japan; NCT02254837). LEVEL OF EVIDENCE: Post-market surveillance study, Level III.

Dilation or biodegradable stent placement for recurrent benign esophageal strictures: a randomized controlled trial.

BACKGROUND: Dilation is the standard of care for recurrent benign esophageal strictures (BES). Biodegradable stents may prolong the effect of dilation and reduce recurrences. Efficacy and safety of dilation and biodegradable stent placement early in the treatment algorithm of recurrent BES were compared. METHODS: This multicenter, randomized study enrolled patients with BES treated with previous dilations to ≥ 16 mm. The primary end point was number of repeat endoscopic dilations for recurrent stricture within 3 and 6 months. Secondary outcomes through 12 months included safety, time to first dilation for recurrent stricture, dysphagia, and level of activity. RESULTS: At 3 months, the biodegradable stent group (n = 32) underwent significantly fewer endoscopic dilations for recurrent stricture compared with the dilation group (n = 34; P < 0.001). By 6 months, the groups were similar. The number of patients experiencing adverse events was similar between the groups. Two patients in the biodegradable stent group died after developing tracheoesophageal fistulas at 95 and 96 days post-placement; no deaths were attributed to the stent. Median time to first dilation of recurrent stricture for the biodegradable stent group was significantly longer (106 vs. 41.5 days; P = 0.003). Dysphagia scores improved for both groups. Patients in the biodegradable stent group had a significantly higher level of activity through 12 months (P < 0.001). CONCLUSION: Biodegradable stent placement is associated with temporary reduction in number of repeat dilations and prolonged time to recurrent dysphagia compared with dilation. Additional studies are needed to better define the exact role of biodegradable stent placement to treat recurrent BES.

Long-Term Effectiveness of the Zilver PTX Drug-Eluting Stent for Femoropopliteal Peripheral Artery Disease in Patients with No Patent Tibial Runoff Vessels-Results from the Zilver PTX Japan Post-Market Surveillance Study.

PURPOSE: To evaluate 2-year results of the Zilver PTX (Cook Medical, Bloomington, Indiana) drug-eluting stent (DES) for femoropopliteal peripheral artery disease (PAD) in patients with no continuous patent infrapopliteal runoff arteries compared with patients with ≥ 1 continuous patent runoff vessels. MATERIALS AND METHODS: A retrospective analysis of patients with femoropopliteal PAD enrolled in the Zilver PTX Post-Market Surveillance Study in Japan was performed. There were no exclusion criteria. Outcomes, including freedom from target lesion revascularization (TLR), patency, and clinical benefit, for the no-runoff group (n = 54) were compared with the runoff group (n = 846). RESULTS: The 2 groups were similar in terms of demographics, lesion characteristics, and comorbidities (P > .05). There was a higher incidence of critical limb ischemia in the no-runoff group compared with the runoff group (44.8% vs 19.7%; P < .01). There were 3 amputations (5.6%) in the no-runoff group versus 7 amputations (0.8%) in the runoff group (P = .02). At 2 years, freedom from TLR rates were 81.3% versus 83.8% (P = .87), patency rates were 68.4% versus 70.7% (P = .95), and clinical benefit rates were 73.7% versus 80.0% (P = .16) in the no-runoff versus runoff group, respectively. CONCLUSIONS: Results in patients with no continuous patent tibial runoff were favorable through 2 years and similar to results for patients with ≥ 1 continuous patent runoff vessels, indicating that the Zilver PTX DES may be a valid treatment option for patients with these difficult-to-treat lesions.

Impact of Chronic Renal Failure on Safety and Effectiveness of Paclitaxel-Eluting Stents for Femoropopliteal Artery Disease: Subgroup Analysis from Zilver PTX Post-Market Surveillance Study in Japan.

PURPOSE: Favorable long-term outcomes of the Zilver PTX drug-eluting stent (DES) in femoropopliteal lesions have been demonstrated. Chronic renal failure (CRF) has been shown to be a risk factor for restenosis and decreased limb salvage. The results of the DES in patients with CRF have not previously been reported. This study compares the results with the DES in patients with CRF and those without CRF. METHODS: This retrospective analysis from the Zilver PTX Japan Post-Market Surveillance Study included 321 patients with CRF and 584 patients without CRF. Outcomes included freedom from target lesion revascularization (TLR) and patency. RESULTS: Of the patients included in this subgroup analysis, 2-year data were available for 209 patients in the CRF group and 453 patients in the non-CRF group. The two groups were similar in terms of lesion length and the frequency of in-stent restenosis. Critical limb ischemia, severe calcification, and diabetes were more common in patients with CRF, whereas total occlusion was more common in patients without CRF. Freedom from TLR rates were 81.4 versus 84.9% (p = 0.24), and patency rates were 70.7 versus 70.3% (p = 0.95) in patients with and without CRF at 2 years, respectively. CONCLUSION: This is the first comparative study of the DES in femoropopliteal artery lesions in patients with and without CRF. These results indicate that the DES placed in femoropopliteal artery lesions of CRF patients is safe and effective with similar patency and TLR rates to patients without CRF. LEVEL OF EVIDENCE: Level 3, Post-Market Surveillance Study.

Durable Clinical Effectiveness With Paclitaxel-Eluting Stents in the Femoropopliteal Artery: 5-Year Results of the Zilver PTX Randomized Trial.

BACKGROUND: This randomized controlled trial evaluated clinical durability of Zilver PTX, a paclitaxel-coated drug-eluting stent (DES), for femoropopliteal artery lesions. Outcomes compare primary DES versus percutaneous transluminal angioplasty (PTA), overall DES (primary and provisional) versus standard care (PTA and provisional Zilver bare metal stent [BMS]), and provisional DES versus provisional BMS. METHODS AND RESULTS: Patients with symptomatic femoropopliteal artery disease were randomly assigned to DES (n=236) or PTA (n=238). Approximately 91% had claudication; 9% had critical limb ischemia. Patients experiencing acute PTA failure underwent secondary randomization to provisional BMS (n=59) or DES (n=61). The 1-year primary end points of event-free survival and patency showed superiority of primary DES in comparison with PTA; these results were sustained through 5 years. Clinical benefit (freedom from persistent or worsening symptoms of ischemia; 79.8% versus 59.3%, P<0.01), patency (66.4% versus 43.4%, P<0.01), and freedom from reintervention (target lesion revascularization, 83.1% versus 67.6%, P<0.01) for the overall DES group were superior to standard care in nonrandomized comparisons. Similarly, clinical benefit (81.8% versus 63.8%, P=0.02), patency (72.4% versus 53.0%, P=0.03), and freedom from target lesion revascularization (84.9% versus 71.6%, P=0.06) with provisional DES were improved over provisional BMS. These results represent >40% relative risk reduction for restenosis and target lesion revascularization through 5 years for the overall DES in comparison with standard care and for provisional DES in comparison with provisional BMS. CONCLUSIONS: The 5-year results from this large study provide long-term information previously unavailable regarding endovascular treatment of femoropopliteal artery disease. The Zilver PTX DES provided sustained safety and clinical durability in comparison with standard endovascular treatments. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT00120406.

Zilver PTX Post-Market Surveillance Study of Paclitaxel-Eluting Stents for Treating Femoropopliteal Artery Disease in Japan: 12-Month Results.

OBJECTIVES: This multicenter, prospective, post-market surveillance study in Japan evaluates the paclitaxel-coated Zilver PTX stent in real-world patients with complex lesions. BACKGROUND: The Zilver PTX stent is the first drug-eluting stent (DES) approved for the superficial femoral artery. Previously, results from a large randomized study and a complementary, large single-arm study supported the safety and effectiveness of the DES. METHODS: There were no exclusion criteria, and consecutive patients with symptomatic peripheral artery disease (PAD) treated with the DES were enrolled in the study. Clinically driven target lesion revascularization (TLR) was defined as reintervention performed for ≥50% diameter stenosis after recurrent clinical symptoms of PAD. Clinical benefit was defined as freedom from persistent or worsening symptoms of ischemia. Patency was evaluated by duplex ultrasound where physicians considered this standard of care. RESULTS: In this study, 907 patients were enrolled at 95 institutions in Japan. There were numerous comorbidities including high incidences of diabetes (58.8%), chronic kidney disease (43.8%), and critical limb ischemia (21.5%). Lesions were also complex, with an average length of 14.7 cm, 41.6% total occlusions, and 18.6% in-stent restenosis. In total, 1,861 DES were placed in 1,075 lesions. Twelve-month follow-up was obtained for >95% of eligible patients. Freedom from TLR was 91.0%, and clinical benefit was 87.7% through 12 months. The 12-month primary patency rate was 86.4%. CONCLUSIONS: Despite more challenging lesions, results from the current study are similar to outcomes from the previous Zilver PTX studies, confirming the benefit of the Zilver PTX DES in a real-world patient population. (Zilver PTX Post-Market Study in Japan; NCT02254837).

Two-year analysis of the Japanese cohort from the Zilver PTX randomized controlled trial supports the validity of multinational clinical trials.

PURPOSE: To report a subgroup analysis comparing safety and effectiveness outcomes in Japanese and non-Japanese patients as part of a prospective, multinational, randomized controlled trial (ClinicalTrials.gov identifier NCT00120406) evaluating a paclitaxel-coated drug-eluting stent (DES) compared to percutaneous transluminal angioplasty (PTA) for treating peripheral artery disease. METHODS: Patients were randomly assigned to primary DES or PTA. In the Japanese cohort, 27 patients (21 men; mean age 71.2±9.6 years) were randomized to PTA and 25 patients (19 men; mean age 69.8±10.2 years) to primary DES. In the non-Japanese cohort, 211 patients (131 men; mean age 67.3±10.6 years) were randomized to PTA and 211 patients (136 men; mean age 67.6±9.5 years) to primary DES. Outcome measures included event-free survival (EFS), freedom from target lesion revascularization (TLR), patency, stent fracture, and sustained clinical benefit through 2 years. RESULTS: Safety and effectiveness outcomes were similar in the Japanese and non-Japanese cohorts, although the outcomes in the Japanese cohort treated with primary DES were numerically better. In the DES group, the 2-year EFS was 92.0% vs. 85.0% (p=0.61), freedom from TLR was 96.0% vs. 85.5% (p=0.55), primary patency was 80.0% vs. 74.3% (p=0.61), and clinical benefit was sustained in 88.5% vs. 80.5% of patients (p=0.31) in the Japanese and non-Japanese cohorts, respectively. Stent fractures were seen in 4 of 457 stents at 12 months: 3 in the Japanese cohort and 1 in the non-Japanese cohort. CONCLUSION: The subgroup analysis comparing Japanese and non-Japanese patients supports the safety and effectiveness of the paclitaxel-coated DES in Japanese patients with stenotic lesions in the femoropopliteal arteries. The lack of major differences associated with ethnicity in these 2-year outcomes supports the validity and value of multinational clinical trials.

Sustained safety and effectiveness of paclitaxel-eluting stents for femoropopliteal lesions: 2-year follow-up from the Zilver PTX randomized and single-arm clinical studies.

OBJECTIVES: A prospective, multinational randomized controlled trial (RCT) and a complementary single-arm study evaluated the 2-year safety and effectiveness of a paclitaxel-coated drug-eluting stent (DES) in patients with superficial femoral artery lesions. The RCT compared the DES with percutaneous transluminal angioplasty (PTA) and provisional bare-metal stent (BMS) placement. BACKGROUND: Local drug delivery for superficial femoral artery lesions has been investigated with the intent of limiting restenosis similarly to DES for the coronary arteries. One-year outcomes of DES in the superficial femoral artery are promising, but longer-term benefits have not been established. METHODS: In the RCT, patients were randomly assigned to primary DES implantation (n = 236) or PTA (n = 238). Acute PTA failure occurred in 120 patients, who underwent secondary randomization to DES (n = 61) or BMS (n = 59) placement. The single-arm study enrolled 787 patients with DES treatment. RESULTS: Compared with the control group, the primary DES group demonstrated significantly superior 2-year event-free survival (86.6% vs. 77.9%, p = 0.02) and primary patency (74.8% vs. 26.5%, p < 0.01). In addition, the provisional DES group exhibited superior 2-year primary patency compared with the provisional BMS group (83.4% vs. 64.1%, p < 0.01) and achieved higher sustained clinical benefit (83.9% vs. 68.4%, p = 0.05). Two-year freedom from target lesion revascularization with primary DES placement was 80.5% in the single-arm study and 86.6% in the RCT. CONCLUSIONS: Two-year outcomes with the paclitaxel-eluting stent support its sustained safety and effectiveness in patients with femoropopliteal artery disease, including the long-term superiority of the DES to PTA and to provisional BMS placement. (Evaluation of the Zilver PTX Drug-Eluting Stent in the Above-the-Knee Femoropopliteal Artery; NCT00120406; Zilver(®) PTX™ Global Registry; NCT01094678).

Identification of steroid-sensitive gene-1/Ccdc80 as a JAK2-binding protein.

The tyrosine kinase Janus kinase 2 (JAK2) is activated by many cytokine receptors, including receptors for GH, leptin, and erythropoietin. However, very few proteins have been identified as binding partners for JAK2. Using a yeast 2-hybrid screen, we identified steroid-sensitive gene-1 (SSG1)/coiled-coil domain-containing protein 80 (Ccdc80) as a JAK2-binding partner. We demonstrate that Ccdc80 preferentially binds activated, tyrosyl-phosphorylated JAK2 but not kinase-inactive JAK2 (K882E) in both yeast and mammalian systems. Ccdc80 is tyrosyl phosphorylated in the presence of JAK2. The binding of Ccdc80 to JAK2 occurs via 1 or more of the 3 DUDES/SRPX (DRO1-URB-DRS-Equarin-SRPUL/sushi repeat containing protein, x-linked) domain 5 domains of Ccdc80. Mutagenesis of the second DUDES domain suggests that the N-terminal third of the DUDES domain is sufficient for JAK2 binding. Ccdc80 does not alter the kinase activity of JAK2. However, Ccdc80 increases GH-dependent phosphorylation of Stat (signal transducer and activator of transcription) 5b on Tyr699 and substantially enhances both basal and GH-dependent phosphorylation/activation of Stat3 on Tyr705. Furthermore, Ccdc80 belongs to the group of proteins that function both in the intracellular compartment and are secreted. Secreted Ccdc80 associates with the extracellular matrix and is also found in the medium. A substantial portion of the Ccdc80 detected in the medium is cleaved. Finally, consistent with the DUDES domain serving as a JAK2-binding domain, we also demonstrate that another protein that contains a DUDES domain, SRPX2, binds preferentially to the activated tyrosyl-phosphorylated form of JAK2.

T-cell factor 4N (TCF-4N), a novel isoform of mouse TCF-4, synergizes with beta-catenin to coactivate C/EBPalpha and steroidogenic factor 1 transcription factors.

We have cloned T-cell factor 4N (TCF-4N), an alternative isoform of TCF-4, from developing pituitary and 3T3-L1 preadipocytes. This protein contains the N-terminal interaction domain for beta-catenin but lacks the DNA binding domain. While TCF-4N inhibited coactivation by beta-catenin of a TCF/lymphoid-enhancing factor (LEF)-dependent promoter, TCF-4N potentiated coactivation by beta-catenin of several non-TCF/LEF-dependent promoters. For example, TCF-4N synergized with beta-catenin to activate the alpha-inhibin promoter through functional and physical interactions with the orphan nuclear receptor steroidogenic factor 1 (SF-1). In addition, TCF-4N and beta-catenin synergized with the adipogenic transcription factor CCAAT/enhancer binding protein alpha (C/EBPalpha) to induce leptin promoter activity. The mechanism by which beta-catenin and TCF-4N coactivated C/EBPalpha appeared to involve p300, based upon synergy between these important transcriptional regulators. Consistent with TCF-4N's redirecting the actions of beta-catenin in cells, ectopic expression of TCF-4N in 3T3-L1 preadipocytes partially relieved the block of adipogenesis caused by beta-catenin. Thus, we propose that TCF-4N inhibits coactivation by beta-catenin of TCF/LEF transcription factors and potentiates the coactivation by beta-catenin of other transcription factors, such as SF-1 and C/EBPalpha.

The roles of Cbl-b and c-Cbl in insulin-stimulated glucose transport.

Previous studies suggest that the stimulation of glucose transport by insulin involves the tyrosine phosphorylation of c-Cbl and the translocation of the c-Cbl/CAP complex to lipid raft subdomains of the plasma membrane. We now demonstrate that Cbl-b also undergoes tyrosine phosphorylation and membrane translocation in response to insulin in 3T3-L1 adipocytes. Ectopic expression of APS facilitated insulin-stimulated phosphorylation of tyrosines 665 and 709 in Cbl-b. The phosphorylation of APS produced by insulin drove the translocation of both c-Cbl and Cbl-b to the plasma membrane. Like c-Cbl, Cbl-b associates constitutively with CAP and interacts with Crk upon insulin stimulation. Cbl proteins formed homo- and heterodimers in vivo, which required the participation of a conserved leucine zipper domain. A Cbl mutant incapable of dimerization failed to interact with APS and to undergo tyrosine phosphorylation in response to insulin, indicating an essential role of Cbl dimerization in these processes. Thus, both c-Cbl and Cbl-b can initiate a phosphatidylinositol 3-kinase/protein kinase B-independent signaling pathway critical to insulin-stimulated GLUT4 translocation.