A single amino acid substitution in the group 1 Trypanosoma brucei gambiense haptoglobin-hemoglobin receptor abolishes TLF-1 binding.

Critical to human innate immunity against African trypanosomes is a minor subclass of human high-density lipoproteins, termed Trypanosome Lytic Factor-1 (TLF-1). This primate-specific molecule binds to a haptoglobin-hemoglobin receptor (HpHbR) on the surface of susceptible trypanosomes, initiating a lytic pathway. Group 1 Trypanosoma brucei gambiense causes human African Trypanosomiasis (HAT), escaping TLF-1 killing due to reduced uptake. Previously, we found that group 1 T. b. gambiense HpHbR (TbgHpHbR) mRNA levels were greatly reduced and the gene contained substitutions within the open reading frame. Here we show that a single, highly conserved amino acid in the TbgHpHbR ablates high affinity TLF-1 binding and subsequent endocytosis, thus evading TLF-1 killing. In addition, we show that over-expression of TbgHpHbR failed to rescue TLF-1 susceptibility. These findings suggest that the single substitution present in the TbgHpHbR directly contributes to the reduced uptake and resistance to TLF-1 seen in these important human pathogens.

Phase I/II trial of formoterol fumarate combined with megestrol acetate in cachectic patients with advanced malignancy.

PURPOSE: The aim of this study was to test the safety, tolerability and efficacy of a novel combination of an anabolic ß2-agonist and an appetite stimulant in patients with cancer cachexia. METHODS: Thirteen patients (M/F 5:8) with advanced malignancy and involuntary weight loss received oral formoterol (80 µg/day) and megestrol acetate (480 mg/day) for up to 8 weeks. Quadriceps size (MRI), quadriceps and hand-grip strength, lower limb extensor power, physical activity and quality of life were measured at baseline and at 8 weeks. Response criteria were specified pre-trial, with a major response defined as an increase in muscle size ≥ 4 % or function ≥ 10 %. RESULTS: Six patients withdrew before 8 weeks, reflecting the frail, comorbid population. In contrast, six out of seven (86 %) patients completing the course achieved a major response for muscle size and/or function. In the six responders, mean quadriceps volume increased significantly (left 0.99 vs. 1.05 L, p=0.012; right 1.02 vs. 1.06 L, p=0.004). There was a trend towards an increase in quadriceps and handgrip strength (p>0.05). The lack of appetite symptom score declined markedly (76.2 vs. 23.8; p=0.005), indicating improvement. Adverse reactions were few, the commonest being tremor (eight reports), peripheral oedema (three), tachycardia (two) and dyspepsia (two). CONCLUSIONS: In this frail cohort with advanced cancer cachexia, an 8-week course of megestrol and formoterol in combination was safe and well tolerated. Muscle mass and/or function were improved to a clinically significant extent in most patients completing the course. This combination regimen warrants further investigation in larger, randomized trials.

Defining a positive circumferential resection margin in oesophageal cancer and its implications for adjuvant treatment.

BACKGROUND: A positive circumferential resection margin (CRM) has been associated with a poorer prognosis in oesophageal and oesophagogastric junctional (OGJ) cancer. The College of American Pathologists defines the CRM as positive if tumour cells are present at the margin, whereas the Royal College of Pathologists also include tumour cells within 1 mm of this margin. The relevance of these differences is not clear and no study has investigated the impact of adjuvant therapy. The aim was to identify the optimal definition of an involved CRM in patients undergoing resection for oesophageal or OGJ cancer, and to determine whether adjuvant radiotherapy improved survival in patients with an involved CRM. METHODS: This was a single-centre retrospective study of patients who had undergone attempted curative resection for a pathological T3 oesophageal or OGJ cancer. Clinicopathological variables and distance from the tumour to the CRM, measured to ± 0.1 mm, were correlated with survival. RESULTS: A total of 226 patients were included. Sex (P = 0·018), tumour differentiation (P = 0·019), lymph node status (P < 0·001), number of positive nodes (P < 0·001), and CRM distance (P = 0·042) were independently predictive of prognosis. No significant survival difference was observed between positive CRM 0-mm and 0·1-0·9-mm groups after controlling for other prognostic variables. Both groups had poorer survival than matched patients with a CRM at least 1 mm clear of tumour cells. Among patients with a positive CRM of less than 1 mm, those undergoing observation alone had a median survival of 18·6 months, whereas survival was a median of 10 months longer in patients undergoing adjuvant radiotherapy, but otherwise matched for prognostic variables (P = 0·009). CONCLUSION: A positive CRM of 1 mm or less should be regarded as involved. Adjuvant radiotherapy confers a significant survival benefit in selected patients with an involved CRM.

A novel oral tracer procedure for measurement of habitual myofibrillar protein synthesis.

RATIONALE: Conventionally, myofibrillar protein synthesis is measured over time periods of hours. In clinical studies, interventions occur over weeks. Functional measures over such periods may be more representative. We aimed to develop a novel method to determine myofibrillar protein fractional synthetic rate (FSR) to estimate habitual rates, while avoiding intravenous tracer infusions. METHODS: Four healthy males were given 100 g water enriched to 70 Atom % with (2)H2O as a single oral bolus. Vastus-lateralis needle biopsies were performed and plasma samples collected, 3-13 days post-dose. (2)H enrichment in body water was measured in plasma using continuous flow isotope ratio mass spectrometry (IRMS). Myofibrillar protein was isolated from muscle biopsies and acid hydrolysed. (2)H enrichment of protein-bound and plasma-free alanine was measured by gas chromatography (GC)/pyrolysis/IRMS. Myofibrillar protein FSR was calculated (% day(-1)). RESULTS: The tracer bolus raised the initial enrichment of body water to 1514 ppm (2)H excess. Water elimination followed a simple exponential. The average elimination half-time was 8.3 days. Plasma alanine, labelled during de novo synthesis, followed the same elimination kinetics as water. The weighted average myofibrillar protein FSR from the four subjects was 1.38 % day(-1) (range, 1.0-1.9 % day(-1) ). CONCLUSIONS: Myofibrillar protein FSR was measured in free-living healthy individuals over 3-13 days. Using a single oral (2)H2O bolus, endogenous labelling of alanine occurred in a predictable manner giving estimates of synthesis comparable with published values. Furthermore, the protocol does not compromise the ability to measure other important metabolic processes such as total energy expenditure.

Enhanced ZAG production by subcutaneous adipose tissue is linked to weight loss in gastrointestinal cancer patients.

BACKGROUND: Profound loss of adipose tissue is a hallmark of cancer cachexia. Zinc-α2-glycoprotein (ZAG), a recently identified adipokine, is suggested as a candidate in lipid catabolism. METHODS: In the first study, eight weight-stable and 17 cachectic cancer patients (weight loss 5% in previous 6 months) were recruited. Zinc-α2-glycoprotein mRNA and protein expression were assessed in subcutaneous adipose tissue (SAT), subcutaneous adipose tissue morphology was examined and serum ZAG concentrations were quantified. In the second cohort, ZAG release by SAT was determined in 18 weight-stable and 15 cachectic cancer patients. The effect of ZAG on lipolysis was evaluated in vitro. RESULTS: Subcutaneous adipose tissue remodelling in cancer cachexia was evident through shrunken adipocytes with increased fibrosis. In cachectic cancer patients, ZAG mRNA was upregulated (2.7-fold, P=0.028) while leptin mRNA decreased (2.2-fold, P=0.018); serum ZAG levels were found to be unaffected. Zinc-α2-glycoprotein mRNA correlated positively with weight loss (r=0.51, P=0.01) and serum glycerol levels (r=0.57, P=0.003). Zinc-α2-glycoprotein release by SAT was also elevated in cachectic patients (1.5-fold, P=0.024) and correlated with weight loss (r=0.50, P=0.003). Recombinant ZAG stimulated lipolysis in human adipocytes. CONCLUSIONS: Zinc-α2-glycoprotein expression and secretion by adipose tissue is enhanced in cachectic cancer patients. Given its lipid-mobilising effect, ZAG may contribute to adipose atrophy associated with cancer cachexia in human beings.

Cross sectional imaging of truncal and quadriceps muscles relates to different functional outcomes in cancer.

INTRODUCTION: Following the consensus definition of cancer cachexia, more studies are using CT scan analysis of truncal muscles as a marker of muscle wasting. However, how CT-derived body composition relates to function, strength and power in patients with cancer is largely unknown. AIMS: We aimed to describe the relationship between CT truncal (L3) skeletal muscle index (SMI) and MRI quadriceps cross sectional area with lower limb strength, power and measures of complex function. METHODS: Patients undergoing assessment for potentially curative surgery for oesophagogastric or pancreatic cancer were recruited from the regional upper gastrointestinal (UGI) or hepatopancreaticobiliary (HPB) multi-disciplinary team meetings. Maximum Isometric Knee Extensor Strength (IKES) and Maximum Leg Extensor Power (Nottingham Power Rig) (LEP) were used as measures of lower limb performance. Both Sit to Stand (STS) and Timed Up and Go (TUG) were used as measures of global complex muscle function. Muscle SMI was measured from routine CT scans at the level of the third lumbar vertebrae (L3) and MRI scan was used for the assessment of quadriceps muscles. Linear regression analysis was performed for CT SMI or MRI quadriceps as a predictor of each measure of performance. RESULTS: Forty-four patients underwent assessment. Height and weight were significantly related to function in terms of quadriceps power, while only weight was associated with strength (P < 0.001). CT SMI was not related to measures of quadriceps strength or power but had significant association with more complex functional measures (P = 0.006, R2 = 0.234 and 0.0019, R2 = 0.175 for STS and TUG respectively). In comparison, both gross and fat-subtracted measures of quadriceps muscle mass from MRI were significantly correlated with quadriceps strength and power (P < 0.001), but did not show any significant association with complex functional measures. CONCLUSION: CT SMI and MRI quadriceps have been shown to reflect different aspects of functional ability with CT SMI being a marker of global muscle function and MRI quadriceps being specific to quadriceps power and strength. This should therefore be considered when choosing outcome measures for trials or definitions of muscle mass and function.

Muscle wasting in cancer.

Skeletal muscle loss appears to be the most significant clinical event in cancer cachexia and is associated with a poor outcome. With regard to such muscle loss, despite extensive study in a range of models, there is ongoing debate as to whether a reduction in protein synthesis, an increase in degradation or a combination of both is the more relevant. Each model differs in terms of key mediators and the pathways activated in skeletal muscle. Certain models do suggest that decreased synthesis accompanied by enhanced protein degradation via the ubiquitin proteasome pathway (UPP) is important. Murine models tend to involve rapid development of cachexia and may represent more acute muscle atrophy rather than the chronic wasting observed in humans. There is a paucity of human data both at a basic descriptive level and at a molecular/mechanism level. Progress in treating the human form of cancer cachexia can only move forwards through carefully designed large randomised controlled clinical trials of specific therapies with validated biomarkers of relevance to underlying mechanisms. This article is part of a Directed Issue entitled: Molecular basis of muscle wasting.

The relationship between hospital volume and post-operative mortality rates for upper gastrointestinal cancer resections: Scotland 1982-2003.

BACKGROUND: Centralisation of surgical treatment of cancer has resulted in improved outcomes. We aimed to determine evidence of benefit for specialised management of upper gastrointestinal cancer in high-volume centres in Scotland. METHODS: Discharge records of patients undergoing oesophagectomy, gastrectomy, hepatectomy or pancreatectomy between 1982 and 2003 were identified. Hospital data were analysed on a year-by-year basis to derive 'hospital-years'. Hospital-years were divided into quartiles by volume, and were analysed with regard to in-hospital mortality during the operative admission [Chi-square test (chi(2)) and Chi-square test for trend (chi(2)(trend))]. RESULTS: 10,625 patients and 982 in-hospital deaths were included. In-hospital mortality rates declined during the study period: oesophagectomy 11.7-7.9%; gastrectomy 11.2-7.2%; hepatectomy 11.1-3.0%; and pancreatectomy 8.3-4.9%. For all resections except gastrectomy, mortality decreased as quartile of hospital-year volume increased (oesophagectomy: chi(2)p=0.006, chi(2)(trend)p=0.001; hepatectomy: chi(2)p=0.004, chi(2)(trend)p=0.003; pancreatectomy: chi(2)p=0.002, chi(2)(trend)p=0.001). ORs of death were lower for oesophagectomy (OR=0.58; 95%CI=0.39, 0.88; p=0.009) and pancreatectomy (OR=0.35; 95%CI=0.19, 0.64; p<0.001) in hospital-years within highest-volume quartiles compared with lowest. Scattergraphs of all resection types demonstrated inverse power relationships between number of resections per hospital-year and mortality. CONCLUSION: Concentration of cancer care has had major effects on health service delivery in Scotland. Centralisation should be supported in surgical management of upper gastrointestinal cancer.