Conversion to resection post radioembolization in patients with HCC: recommendations from a multidisciplinary working group

BACKGROUND

Transarterial radioembolization (TARE) with yttrium-90 (⁹⁰Y) glass microspheres is an efficacious option for converting appropriately selected patients with borderline-resectable hepatocellular carcinoma (HCC) to surgical candidacy.

METHODS

In 2018 and 2019, a diverse multidisciplinary group of surgical and interventional experts with experience using ⁹⁰Y for downstaging and bridging to liver transplant convened to review peer-reviewed literature and personal experience in the use of ⁹⁰Y to convert borderline resectable liver cancer patients to surgical candidacy. The working group included surgical oncologists specializing in liver cancer, liver transplant surgeons with experience in complex hepatobiliary surgery, and interventional radiologists with experience using ⁹⁰Y.

RESULTS

This document presents expert recommendations based upon the group's experience and consensus.

CONCLUSIONS

By combining related evidence from the literature with expert experiences with TARE in surgical candidates, these recommendations aim to demonstrate the safety, efficacy, and feasibility of TARE in converting borderline-resectable patients to surgical options. The document also addresses the concerns about potential complications associated with TARE during the surgical intervention.

Impact of resection margin on outcomes in high-grade soft tissue sarcomas of the extremity-A USSC analysis

BACKGROUND

The optimal margin of resection for high-grade extremity sarcomas and its impact on survival has long been questioned in the setting of adjuvant radiotherapy. The objective of this study was to investigate the impact of resection status on recurrence and survival.

METHODS

All patients with primary, nonmetastatic, high-grade extremity sarcomas that underwent surgical resection from January 2000 to April 2016 in the U.S. Sarcoma Collaborative (USSC) were retrospectively reviewed. Recurrence patterns, recurrence-free survival (RFS), and overall survival (OS) were examined in multivariate analyses (MVA).

RESULTS

A cohort of 959 patients was identified with a median follow-up of 34.7 months from diagnosis. R0 resection was achieved in 86.7% (831) while R1 resection in 13.3% (128). Locoregional recurrence for R0 and R1 groups occurred in 9.1% (76) versus 14.8% (19; p = .05) while distant recurrence occurred in 24.7% (205) versus 26.6% (34; p = .65), respectively. Median RFS was 171.2 versus 48.5 (p = .01) while median OS was 149.8 versus 71.5 months (p = .02) for the R0 versus R1 group, respectively. On MVA, female gender (hazard ratio [HR] = 0.69, p = .007) and adjuvant radiotherapy (0.7, p = .04) were associated with improved OS, whereas older age (HR = 1.03, p < .001) and tumor size (HR = 1.01, p < .001) were associated with worse OS. R0 resection status was associated with improved locoregional RFS (HR = 0.56, p = .03) but not with distant RFS (HR = 0.84, p = .4) or OS (HR = 0.7, p = .052).

CONCLUSIONS

In high-grade extremity sarcomas, tumor size and gender are predictive of OS while R0 resection status is associated with improved locoregional recurrence rate without a significant impact on distant RFS or OS.

Comparison of overall survival in gallbladder carcinoma at academic versus community cancer centers: An analysis of the National Cancer Data Base

BACKGROUND AND OBJECTIVES

Gallbladder carcinoma (GBC) has a poor prognosis. Studies demonstrated that teaching facilities may provide a lower risk of mortality in patients undergoing pancreatic and colon resection vs nonteaching facilities. We hypothesized that survival rates are higher in academic cancer centers (ACCs) vs community cancer centers (CCCs).

METHODS

Patients with all stages of GBC were identified from the National Cancer Database (2007-2012). Propensity score matching adjusted for selection bias. Descriptive statistics were calculated for all variables. Overall survival (OS) was compared by facility type (ACC vs CCC) and case volume (low vs high) via multivariable Cox proportional hazards regression.

RESULTS

A total of 7967 patients met the inclusion criteria. Following propensity matching, 2801 patients were analyzed from each facility type. Median OS following surgery was higher for ACC (20.99 months, 95% confidence interval [CI], 19.61-22.64, P = .002) than CCC (17.68 months, 95% CI, 16.46-19.25). Following Cox modeling, GBC treatment at ACCs was a protective factor for OS (adjusted hazard ratio 0.876, 95% CI, 0.801-0.958, P = .004).

DISCUSSION

GBC treatment at ACCs is an independent predictor of OS. High volume ACCs are associated with improved OS compared with low volume ACCs. The site of care and case volume in ACCs may contribute to improved survival outcomes.

Recurrence patterns after resection of retroperitoneal sarcomas: An eight-institution study from the US Sarcoma Collaborative

BACKGROUND AND OBJECTIVES

Resection of primary retroperitoneal sarcomas (RPS) has a high incidence of recurrence. This study aims to identify patterns of recurrence and its impact on overall survival.

METHODS

Adult patients with primary retroperitoneal soft tissue sarcomas who underwent resection in 2000-2016 at eight institutions of the US Sarcoma Collaborative were evaluated.

RESULTS

Four hundred and ninety-eight patients were analyzed, with 56.2% (280 of 498) having recurrences. There were 433 recurrences (1-8) in 280 patients with 126 (25.3%) being locoregional, 82 (16.5%) distant, and 72 (14.5%) both locoregional and distant. Multivariate analyses revealed the following: Patient age P = .0002), tumor grade (P = .02), local recurrence (P = .0003) and distant recurrence (P < .0001) were predictors of disease-specific survival. The 1-, 3-, and 5-year survival rate for patients who recurred vs not was 89.6% (standard error [SE] 1.9) vs 93.5% (1.8), 66.0% (3.2) vs 88.4% (2.6), and 51.8% (3.6) vs 83.9% (3.3), respectively, P < .0001. Median survival was 5.3 years for the recurrence vs 11.3+ years for the no recurrence group (P < .0001). Median survival from the time of recurrence was 2.5 years.

CONCLUSIONS

Recurrence after resection of RPS occurs in more than half of patients independently of resection status or perioperative chemotherapy and is equally distributed between locoregional and distant sites. Recurrence is primarily related to tumor biology and is associated with a significant decrease in overall survival.

RAS Mutation Status Confers Prognostic Relevance in Patients Treated With Cytoreductive Surgery and Hyperthermic Intraperitoneal Chemotherapy for Colorectal Cancer

BACKGROUND

Metastatic colorectal cancer (mCRC) with peritoneal carcinomatosis is an increasingly prevalent disease that carries significant mortality if left untreated. Cytoreductive surgery with hyperthermic intraperitoneal chemotherapy (CRS/HIPEC) in this patient population is associated with improved outcomes but high morbidity. We sought to study the prognostic significance of the known genomic driver, RAS, in patients with mCRC undergoing CRS/HIPEC to allow for improved assessment of risk-benefit ratio in this patient population.

METHODS

Patients undergoing CRS/HIPEC for mCRC between 2010 and 2017 at our institution were identified. Patient demographics, RAS mutation status, perioperative morbidity, overall survival (OS), and relapse-free survival (RFS) were evaluated.

RESULTS

Forty-seven patients met inclusion criteria. RAS mutant versus RAS wild-type groups were well matched with no difference in the clinicopathologic factors between groups. RAS mutation was associated with decreased RFS but no difference in OS.

CONCLUSIONS

RAS mutation is an independent marker of early recurrence in patients undergoing CRS/HIPEC for mCRC and may identify patients who do not derive benefit from this high-risk procedure.

Stereotactic body radiation therapy for hepatocellular carcinoma: Practice patterns, dose selection and factors impacting survival

Background

Stereotactic body radiation therapy (SBRT) is an emerging option for unresectable hepatocellular carcinoma (HCC) without consensus regarding optimal dose schemas. This analysis identifies practice patterns and factors that influence dose selection and overall survival, with particular emphasis on dose and tumor size.

Materials/Methods

Query of the National Cancer Database (NCDB) identified patients with unresectable, nonmetastatic HCC who received SBRT from 2004 to 2013. Biological Effective Dose (BED) was calculated for each patient in order to uniformly analyze different fractionation regimens.

Results

A total of 456 patients met the inclusion criteria. The median BED was 100 Gy (22.5‐208.0), which corresponded to the most common dose fractionation (50 Gy in five fractions). Various factors influenced dose selection including tumor size (P < 0.001), tumor stage (P = 0.002), and facility case volume (<0.001). On multivariate analysis, low BED (<75 Gy, HR 2.537, P < 0.001; 75‐100 Gy, HR 1.986, P = 0.007), increasing tumor size (HR 1.067, P = 0.032), elevated AFP (HR 1.585, P = 0.019), stage 3 (HR 1.962, P < 0.001), low‐volume facilities (1‐5 cases HR 1.687, P = 0.006), and a longer time interval from diagnosis to SBRT (>2 to ≤4 months, HR 1.456, P = 0.048; >4 months, HR 2.192, P < 0.001) were associated with worse survival.

Conclusion

SBRT use is increasing for HCC, and multiple regimens are clinically employed. Although high BED was associated with improved outcomes, multiple factors contributed to the dose selection with favorable patients receiving higher doses. Continued efforts to enhance radiation planning and delivery may help improve utilization, safety, and efficacy.

Is long-term survival possible after margin-positive resection of retroperitoneal sarcoma (RPS)?

BACKGROUND/OBJECTIVES

For various reasons, some patients undergo a gross margin positive resection (R2) leading to a dilemma in care. We hypothesized that there is a subset of patients who have long-term survival (LTS, ≥5 years) after R2 resection for retroperitoneal sarcoma (RPS).

METHODS

National Cancer Database data from 1998 to 2011 were reviewed to identify patients with RPS who had R2 resections. Logistic and Cox regression models were used to compare LTS with short-term survival.

RESULTS

Of 12,028 patients, R2 resection rate was 3.28% (4.9% in 1998; 2.5% in 2011). Median survival for RPS with R2 resection was 21 months versus 69 months for those with R0/R1 resections (P < 0.001). Of 272 patients with available survival, 24% (n = 64) survived ≥5 years with 64% alive at follow-up. LTS was most often seen in younger patients (<65 years) with well-differentiated liposarcoma. Chemotherapy appeared to improve survival in the first 3 postoperative years, but paradoxical effects were seen in LTS (Hazards Ratio [HR] 0.69, 95%CI: 0.50-0.95, P = 0.024) in first 3 years versus (HR 2.15, 95%CI: 1.21-3.81, P = 0.009).

CONCLUSION

Long-term survival is possible for a subset of patients after an R2 resection for RPS, especially with favorable histology characteristics. Benefits of chemotherapy in margin positive settings need to be investigated. J. Surg. Oncol. 2016;113:823-827. © 2016 Wiley Periodicals, Inc.

Role of Akt inhibition on Notch1 expression in hepatocellular carcinoma: potential role for dual targeted therapy

BACKGROUND

We have shown that an Akt inhibitor, MK2206, reduces hepatocellular carcinoma (HCC) proliferation. To further delineate MK2206, we sought to investigate the Notch1 pathway and hypothesize that MK2206 treatment will result in Notch1 inhibition with either subsequent or parallel Akt suppression.

METHODS

HCC cell lines were treated with various concentrations of MK2206. Cell proliferation was determined via real-time live cell imaging. Knockdown of Notch1 was used to observe interaction between Notch1 and pAkt. Cell lysates were analyzed via Western blotting for Notch and Akt pathway targets.

RESULTS

After treatment with MK2206 (up to 2 μM), there was a 60% reduction in cell viability at 48 hours with a concomitant reduction in Notch1 expression. Knockdown of Notch1 in HCC cell lines correlated with reduction in Akt phosphorylation.

CONCLUSIONS

MK2206 inhibits both the PI3-K/Akt and Notch1 pathways. Therefore, further characterization of MK2206 comparing the 2 pathways is warranted and the effect of dual targeting in HCC.

Patency rates of portal vein/superior mesenteric vein reconstruction after pancreatectomy for pancreatic cancer

BACKGROUND

Pancreatectomy with venous reconstruction (VR) for pancreatic cancer (PC) is occurring more commonly. Few studies have examined the long-term patency of the superior mesenteric-portal vein confluence following reconstruction.

METHODS

From 2007 to 2013, patients who underwent pancreatic resection with VR for PC were classified by type of reconstruction. Patency of VR was assessed using surveillance computed tomographic imaging obtained from date of surgery to last follow-up.

RESULTS

VR was performed in 43 patients and included the following: tangential resection with primary repair (7, 16%) or saphenous vein patch (9, 21%); segmental resection with splenic vein division and either primary anastomosis (10, 23%) or internal jugular vein interposition (8, 19%); or segmental resection with splenic vein preservation and either primary anastomosis (3, 7%) or interposition grafting (6, 14%). All patients were instructed to take aspirin after surgery; low molecular weight heparin was not routinely used. An occluded VR was found in four (9%) of the 43 patients at a median follow-up of 13 months; median time to detection of thrombosis in the four patients was 72 days (range 16-238).

CONCLUSIONS

Pancreatectomy with VR can be performed with high patency rates. The optimal postoperative pharmacologic therapy to prevent thrombosis requires further investigation.

MK2206 inhibits hepatocellular carcinoma cellular proliferation via induction of apoptosis and cell cycle arrest

BACKGROUND

Hepatocellular carcinoma (HCC) is commonly diagnosed at an advanced stage and has limited effective treatment options. The aberrant regulation of the phosphoinositide 3-kinase/Akt pathway in HCC makes it an attractive therapeutic target. The effect of MK2206, a novel, allosteric Akt inhibitor, on HCC cells is not yet fully understood. We hypothesized that inhibition of Akt by MK2206 would impact cellular viability.

MATERIALS AND METHODS

Human Huh7, Hep3B, and HepG2 cell lines were treated with 0-2 μM of MK2206 for 96 h. Cell viability was determined by using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Western blot analysis was used to examine the expression level of various protein markers to assess the mechanism of drug action and proliferation inhibition.

RESULTS

3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay showed a reduction in cellular viability by ≥55% for all cell lines (control versus 2 μM MK2206; P <0.001). Western blot analysis revealed reduction in the level of phosphorylated AKT-Ser473 with no change in AKT-thr308 expression confirming the specificity of MK2206. There was an observed reduction in caspase-9 and survivin. Importantly, there were increases in p21 and p27 along with decreased cyclinD1 expression after treatment.

CONCLUSIONS

This study demonstrates the anti-tumor activity of MK2206 in HCC cells. The observed reduction in survivin and pro-caspase 9 suggests that MK2206 induces apoptosis. However, HCC proliferation is also halted via induction of cell cycle arrest as indicated by the increase in p21 and p27 expression and decrease in cyclinD1. Importantly, the concentration needed to achieve growth inhibition in HCC is lower than that needed for other cancer types.

Microwave ablation for hepatic malignancies: a call for standard reporting and outcomes

BACKGROUND

Clinical standards of reporting microwave ablation outcomes have not been defined with regard to ablation success, 90-day morbidity, local recurrence after ablation, and nonablation hepatic recurrence. We propose recommendations for microwave ablation reporting and quality standards.

METHODS

Literature review of clinical studies focusing on microwave ablation of primary and metastatic hepatic tumors was reported.

RESULTS

Ablation success remains the highest quality reporting standard with variations in nomenclature, but with a universal agreement of complete destruction of the target lesion within 1 month after initial microwave ablation. Local recurrence after ablation remains highly variable, with reports as low as 2.2% to as high as 22%; standards lack a common, clearly defined distance from the initial target ablated lesion and the requirement that the target lesion be defined as an ablation success before it can be called a recurrence. Nonablation hepatic recurrence, nonhepatic recurrence, and 90-day morbidity and mortality remain limited in the current literature.

CONCLUSIONS

Standardization of hepatic microwave ablation reporting standards are proposed. Current reporting standards in microwave ablation of hepatic malignancies are suboptimal and lack standardization for comparison across institutions.

Ciliated hepatic cyst leading to squamous cell carcinoma of the liver - A case report and review of the literature

INTRODUCTION

Ciliated hepatic foregut cysts (CHFC) are rare, typically benign liver lesions. Primary squamous cell carcinoma (SCC) of the liver is also a rare entity with only approximately 25 reported cases in the literature. Recently, there have been four reports of malignant transformation of CHFC into primary squamous cell carcinoma of the liver. Here we report a fifth with unique presentation and review the literature.

PRESENTATION OF CASE

A 34 year-old man, with a history of ulcerative colitis, was incidentally found to have a 10 cm lesion in the right anterior sector plus left medial section of the liver on computerized tomography (CT) scan. The patient was asymptomatic at presentation and neoplastic markers were not elevated. Sequential transarterial chemoembolization (TACE) and portal vein embolization (PVE) allowed for left lateral section plus segment 1 hypertrophy and subsequent resection. Histology later revealed the cyst to be a CHFC and showed its malignant transformation. At 6 month follow-up, the patient has lung and abdominal recurrence.

DISCUSSION

With now the fifth case of malignant transformation of CHFC being reported, approximately 5% of all reported CHFC have undergone malignant transformation. This frequency, taken together with the aggressive disease course and poor prognosis, suggests that CHFC must not be presumed benign and should be regarded with clinical suspicion.

CONCLUSION

Accurate diagnosis of CHFC is mandatory given its potential malignant transformation. Even in asymptomatic CHFC, surgical excision is recommended. In addition, in cases of otherwise unresectable lesions, sequential TACE and PVE may provide optimal hypertrophy of future liver remnant.

Surgical management of leiomyosarcoma of the inferior vena cava

INTRODUCTION

Leiomyosarcoma of the inferior vena cava (IVC) is a rare tumor for which en bloc resection offers the only chance of cure. Due to its rarity, however, optimal strategies for the management of the primary tumor and subsequent recurrences are not well defined.

METHODS

We performed a retrospective review of patients who underwent surgical resection of IVC leiomyosarcoma. We evaluated clinical presentations, operative techniques, patterns of recurrence and survival.

RESULTS

From 1990 to 2008, nine patients (four females) were identified. Median age was 55 years (40-76). Presentations included abdominal pain (n = 5), back pain (n = 2), leg swelling (n = 4) and abdominal mass (n = 2). Pre-operative imaging studies showed tumor location to be from the right atrium to renal veins (n = 1), retrohepatic (n = 5), and from hepatic veins to the iliac bifurcations (n = 3). En bloc resection included right nephrectomy (n = 5), right adrenalectomy (n = 4), pancreaticoduodenectomy (n = 1), right hepatic trisectionectomy (n = 1) and right hemicolectomy (n = 1). The IVC was ligated in six patients, and a prosthetic graft was used for IVC reconstruction in three patients. Resection margins were negative in seven cases. Median length of stay was 12 days (range, 6-22 days). Major morbidity included renal failure (n = 1) and there was one post-operative mortality. Five patients had leg edema post-operatively, four of whom had IVC ligation. Median survival was 47 months (range, 1-181 months). Four patients had recurrence and the median time to recurrence was 14 months (range, 3-25 months). Two patients underwent successful resection of recurrence.

CONCLUSIONS

Curative resection of IVC leiomyosarcoma can lead to long-term survival. However, recurrence is common, and effective adjuvant treatments are needed. In selected cases, aggressive surgical treatment of recurrence should be considered.

Biliary Inflammatory Pseudotumor: Imaging Features in Seven Patients

OBJECTIVE

Hepatic biliary pseudotumor is a benign, rare, and poorly understood tumor that is typically diagnosed after aggressive surgical intervention. The purpose of this report is to describe the clinical and imaging features of this tumor in seven patients.

CONCLUSION

Although secondary clinical features may rarely suggest inflammatory pseudotumor, the typical presenting symptom--painless obstructive jaundice--is indicative of malignancy. The imaging appearance of hepatic hilar biliary pseudotumor is also indistinguishable from that of cholangiocarcinoma.

The L266V tau mutation is associated with frontotemporal dementia and Pick-like 3R and 4R tauopathy

We report a case of rapidly progressive frontotemporal dementia presenting at age 33 years. At autopsy there was severe atrophy of the frontal and temporal lobes. Tau-positive Pick bodies, which ultrastructurally were composed of straight filaments, were present, accompanied by severe neuronal loss and gliosis. RD3, a tau antibody specific for the three-repeat (3R) isoforms, labeled the Pick bodies. ET3, a four-repeat (4R) isoform-specific tau antibody, did not label Pick bodies, but highlighted rare astrocytes, and threads in white matter bundles in the corpus striatum. Analysis of the tau gene revealed an L266V mutation in exon 9. Analysis of brain tissue from this case revealed elevated levels of exon 10+ tau RNA and soluble 4R tau. However, both 3R and 4R isoforms were present in sarkosyl-insoluble tau fractions with a predominance of the shortest 3R isoform. The L266V mutation is associated with decreased rate and extent of tau-induced microtubule assembly, and a 3R isoform-specific increase in tau self assembly as measured by an in vitro assay. Combined, these data indicate that L266V is a pathogenic tau mutation that is associated with Pick-like pathology. In addition, the results of the RD3 and ET3 immunostains clearly explain for the first time the presence of both 3R and 4R tau isoforms in preparations of insoluble tau from some Pick's disease cases.

Inhibition of tau polymerization by its carboxy-terminal caspase cleavage fragment

Abnormal aggregation of the microtubule-associated protein, tau, occurs in many neurodegenerative diseases, making it important to understand the mechanisms of tau polymerization. Previous work has indicated that the C-terminal region of tau inhibits polymerization in vitro, and a growing body of evidence implicates caspase cleavage of tau at Asp 421 in the C-terminus as an important inducer of tau polymerization in Alzheimer's disease. In the present study, we provide evidence that the C-terminal peptide fragment produced by caspase cleavage inhibits tau polymerization, suggesting that caspase cleavage of tau enhances its polymerization by removing the inhibitory control element. Moreover, we provide evidence that the peptide assumes an alpha-helical configuration and inhibits tau assembly by interacting with residues 321-375 in the microtubule binding repeat region. These findings indicate that formation of the fibrillar pathologies during the course of Alzheimer's disease may be driven or sustained by apoptotic events leading to caspase activation.

Accurate deployment of vena cava filters: comparison of intravascular ultrasound and contrast venography

BACKGROUND

The increasing use of vena cava filters by trauma surgeons has led to reports of filter placement using intravascular ultrasound (IVUS). Although attractive because of its ease of use and elimination of contrast and radiation, no studies have examined the accuracy of filter placement by IVUS as compared with contrast venography (CV). The purpose of this study was to compare the anatomic information obtained by both techniques during filter placement.

METHODS

Twenty-one patients meeting trauma service criteria for filter placement were studied (11 women and 10 men; mean age, 46.8 years). All procedures were performed in the operating room by trauma surgeons. Vascular access was obtained by percutaneous placement of an 8 French sheath in the right femoral vein. CV, IVUS, and bilateral selective renal venography were performed before deployment of a Greenfield filter. Localization and diameter measurements were made in reference to a radiopaque ruler placed on the patient's abdomen. We chose the "best location" for filter deployment as 1 cm below the junction of the lowest renal vein and the vena cava. Measurements by CV and IVUS were compared with the "gold standard" of selective renal venography.

RESULTS

As compared with selective renal venography, the difference between best location by CV and IVUS was 16.3 +/- 13.8 mm and 3.7 +/- 5.6 mm, respectively (p = 0.001). In four cases (19%) the CV missed best location by 3 cm or more. CV overestimated the diameter of the vena cava in all cases. Average vena cava diameter was 26.4 +/- 3.3 mm by venography and 20.6 +/- 3.1 mm by IVUS (p < 0.0001). CV incorrectly identified four patients as having vena cava diameters too large (>2.8 cm) for the placement of a Greenfield filter. The two renal vein anomalies (one double left renal vein and one absent left renal vein) were correctly diagnosed by IVUS.

CONCLUSION

IVUS is a more accurate method of localizing the renal veins and measuring vena cava diameter for placement of vena cava filters than contrast venography.

Magnetically guided nasoenteral feeding tubes: a new technique

Our objective was to evaluate a new technique for the bedside placement of nasoenteral feeding tubes into the duodenum using an external hand-held magnet to maneuver the tube from the stomach to the distal duodenum. We conducted a prospective case series of 20 consecutive patients requiring nasoenteral tube feeding in the intensive care units of a university-affiliated hospital. Twenty patients were entered into the study after the attending physician requested assistance in tube placement. A flexible nasoenteral feeding tube (12 F), modified to include a magnet and a magnetic field sensor in the distal tip connected by a thin insulated wire to a small light at the proximal end, was passed per nares into the stomach. A larger hand-held magnet held over the epigastrium was used to magnetically "capture" the tube tip, indicated by the illumination of the proximal light. The tube tip was then maneuvered by the hand-held magnet along the lesser curvature of the stomach, through the pylorus, and into the duodenum. Procedure time and anatomic location of the tube tip as determined by an abdominal radiograph was recorded. The 12 men and eight women had a mean age of 60 years (range 30-84). The procedure time averaged 9.6 minutes (range 1-30). In 19 of the 20 patients (95%) radiographs revealed successful placement of the tip of the feeding tube into the duodenum. There were no complications related to the procedure. Using a novel magnetically guided nasoenteral feeding tube transpyloric tube placement was achieved in 95 per cent of cases with an average procedure time of 9.6 minutes. This new and inexpensive bedside technique will allow prompt and safe initiation of enteral nutrition.

Oxidative regulation of fatty acid-induced tau polymerization

Alzheimer's disease (AD) is characterized by the presence of amyloid-positive senile plaques and tau-positive neurofibrillary tangles. Aside from these two pathological hallmarks, a growing body of evidence indicates that the amount of oxidative alteration of vulnerable molecules such as proteins, DNA, and fatty acids is elevated in the brains of AD patients. It has been hypothesized that the elevated amounts of protein oxidation could lead directly to the formation of neurofibrillary tangles through a cysteine-dependent mechanism. We have tested this hypothesis in an in vitro system in which tau assembly is induced by fatty acids. Using sulfhydryl protective agents and site-directed mutagenesis, we found that cysteine-dependent oxidation of the tau molecule is not required for its polymerization and may even be inhibitory. However, by adjusting the oxidative environment of the polymerization reaction through the addition of a strong antioxidant or through the addition of an oxidizing system consisting of iron, adenosine diphosphate, and ascorbate, we found that oxidation does play a major role in our in vitro paradigm. The results indicated that fatty acid oxidation, the amount of which is found to be elevated in AD patients, can facilitate the polymerization of tau. However, "overoxidation" of the fatty acids can inhibit the process. Therefore, we postulate that specific fatty acid oxidative products could provide a direct link between oxidative stress mechanisms and the formation of neurofibrillary tangles in AD.

C-terminal inhibition of tau assembly in vitro and in Alzheimer's disease

Alzheimer's disease (AD) is, in part, defined by the polymerization of tau into paired helical and straight filaments (PHF/SFs) which together comprise the fibrillar pathology in degenerating brain regions. Much of the tau in these filaments is modified by phosphorylation. Additionally, a subset also appears to be proteolytically truncated, resulting in the removal of its C terminus. Antibodies that recognize tau phosphorylated at S(396/404)or truncated at E(391) do not stain control brains but do stain brain sections very early in the disease process. We modeled these phosphorylation and truncation events by creating pseudo-phosphorylation and deletion mutants derived from a full-length recombinant human tau protein isoform (ht40) that contains N-terminal exons 2 and 3 and all four microtubule-binding repeats. In vitro assembly experiments demonstrate that both modifications greatly enhance the rates of tau filament formation and that truncation increases the mass of polymer formed, as well. Removal of as few as 12 or as many as 121 amino acids from the C terminus of tau greatly increases the rate and extent of tau polymerization. However, deletion of an additional 7 amino acids, (314)DLSKVTS(320), from the third microtubule-binding repeat results in the loss of tau's ability to form filaments in vitro. These results suggest that only part of the microtubule-binding domain (repeats 1, 2 and a small portion of 3) is crucial for tau polymerization. Moreover, the C terminus of tau clearly inhibits the assembly process; this inhibition can be partially reversed by site-specific phosphorylation and completely removed by truncation events at various sites from S(320) to the end of the molecule.

In vitro polymerization of tau protein monitored by laser light scattering: method and application to the study of FTDP-17 mutants

Tau polymerization into the filaments that compose neurofibrillary tangles is seminal to the development of many neurodegenerative diseases. It is therefore important to understand the mechanisms involved in this process. However, a consensus method for monitoring tau polymerization in vitro has been lacking. Here we demonstrate that illuminating tau polymerization reactions with laser light and measuring the increased scattering at 90 degrees to the incident beam with a digital camera results in data that closely approximate the mass of tau polymer formation in vitro. The validity of the technique was demonstrated over a range of tau concentrations and through multiple angle scattering measurements. In addition, laser light scattering data closely correlated with quantitative electron microscopy measurements of the mass of tau filaments. Laser light scattering was then used to measure the efficiency with which the mutant tau proteins found in frontotemporal dementia and Parkinsonism linked to chromosome 17 (FTDP-17) form filamentous structures. Several of these mutant proteins display enhanced polymerization in the presence of arachidonic acid, suggesting a direct role for these mutations in tau the filament formation that characterizes FTDP-17.

Differential assembly of human tau isoforms in the presence of arachidonic acid

Six tau isoforms arise from the alternative splicing of a single gene in humans. Insoluble, filamentous deposits of tau protein occur in a number of neurodegenerative diseases, and in some of these diseases, the deposition of polymers enriched in certain tau isoforms has been documented. Because of these findings, we have undertaken studies on the efficacy of fatty acid-induced polymerization of the individual tau isoforms found in the adult human CNS. The polymerization of each tau isoform in the presence of two concentrations of arachidonic acid indicated that isoforms lacking N-terminal exons e2 and e3 formed small, globular oligomers that did not go on to elongate into straight (SF) or paired helical (PHF) filaments under our buffer conditions. The polymerization of all isoforms containing e2 or e2 and e3 occurred readily at a high arachidonic acid concentration. Conversely, at a lower arachidonic acid concentration, only tau isoforms containing four microtubule binding repeats assembled well. Under all buffer conditions employed, filaments formed from three of the isoforms containing e2 and e3 resembled SFs in morphology but began to form PHF-like structures following extended incubation at 37 degrees C. These results indicate that polymerization of the intact tau molecule may be facilitated by e2 and e3. Moreover, tau isoforms containing three versus four microtubule binding repeats display different assembly properties depending on the solvent conditions employed.

Recombinant microtubule-associated protein 2c reduces the dynamic instability of individual microtubules

The effects of purified recombinant microtubule-associated protein 2c (rMAP2c) on the dynamic instability of microtubules were examined by direct observation of individual microtubules in vitro by video-enhanced differential interference contrast light microscopy. Microtubules were grown in the absence or presence of varying concentrations of rMAP2c and were analyzed to determine growth rates, shortening rates, and the frequencies of conversion between growing and shortening phases. We found rMAP2c to stabilize microtubules dramatically. The most notable effect is a reduction in both the frequency of catastrophes (transitions from growth to shortening) and the mean length of shortening events: no microtubule catastrophes were observed at concentrations of rMAP2c as low as 1.06 microM in a solution of 10 microM tubulin. Even at lower rMAP2c concentrations, there is a marked stabilizing effect. As the concentration of rMAP2c increases, average growth rates increase slightly, shortening rates decrease, and the frequency of rescues (transitions from shortening to growth) increases significantly. Together, these changes in parameters produce a population of extremely stable microtubules in the presence of rMAP2c. This stabilization is consistent with a structural role for MAP2c during early postnatal neural development.

Determination of microtubule polarity in vitro by the use of video-enhanced differential-interference contrast light microscopy and Chlamydomonas flagellar axonemal pieces

Microtubules nucleated by sea urchin sperm-tail axonemes have polar ends that differ both functionally and structurally but cannot be distinguished from one another when viewed by light microscopy. Ambiguity and circularity surround any classification of microtubule polarity by conventional methods. Chlamydomonas flagellar axonemal pieces have distinct morphological differences at their plus- and minus-ends, and microtubules nucleated from these pieces can be distinguished as plus- or minus-ended based on the morphological differences present in the Chlamydomonas flagellar axonemal pieces. Plus- and minus-ended microtubules were polymerized in this fashion and analyzed for differences in growth rates, shortening rates, and frequencies of transitions. The results were in good agreement with similar data generated by the more time-consuming and difficult use of kinesin-coated beads (R. J. Kowalski, and R. C. Williams, Jr. (1993) Cell Motil. Cytoskeleton 26, 282-290) to determine microtubule polarity. This is a relatively simple and effective method for determining the polarity of microtubules in vitro by video-enhanced differential-interference contrast light microscopy.