Improving outcomes in carcinoid heart disease - learning from a single centre.

INTRODUCTION: A significant proportion of patients with carcinoid syndrome develop carcinoid heart disease (CHD). Valve degeneration can lead to right heart failure, and worsening prognosis. Replacement of affected valves is an effective therapy. We reviewed patients treated with valve replacement to assess prognostic factors. METHODS: CHD patients records who underwent valve replacement from 2003-2019 were reviewed. RESULTS: Twenty-six patients underwent valve replacement. Mean (SD) age was 61 (11) years, 54% female. Eleven tumours were grade G1, with the remaining G2. NYHA pre-surgery mean (SD) 2.0 (0.7); post-surgery mean 1.2; follow-up mean (SD) 1.6 (0.8). Mean NYHA score difference from pre- to post-surgery -0.71 ( P  = 0.002). 88.5% two (PR & TR), 3.9% one, 3.9% three and 3.9% four valves replaced. 13 patients received Lu177 oxodotreotide; 27% completed four cycles. Mortality at 1 and 5 years follow up was 42% and 50% respectively. Cox proportional hazards model of survival from surgery, adjusting for age [hazard ratio (HR) 0.96 (0.89-1.03) ( P  = 0.25)], four cycles of Lu177 oxodotreotide demonstrated HR 0.087 (0.0079-0.95) ( P  = 0.045) indicating improved survival. DISCUSSION: Surgical patients were often NYHA grade II, and symptoms improved post-surgery. Four cycles of Lu177 oxodotreotide improved survival, although the confidence interval was wide. Further studies should be performed to assess Lu177 oxodotreotide in CHD.

Functional evolution of IGF2:IGF2R domain 11 binding generates novel structural interactions and a specific IGF2 antagonist.

Among the 15 extracellular domains of the mannose 6-phosphate/insulin-like growth factor-2 receptor (M6P/IGF2R), domain 11 has evolved a binding site for IGF2 to negatively regulate ligand bioavailability and mammalian growth. Despite the highly evolved structural loops of the IGF2:domain 11 binding site, affinity-enhancing AB loop mutations suggest that binding is modifiable. Here we examine the extent to which IGF2:domain 11 affinity, and its specificity over IGF1, can be enhanced, and we examine the structural basis of the mechanistic and functional consequences. Domain 11 binding loop mutants were selected by yeast surface display combined with high-resolution structure-based predictions, and validated by surface plasmon resonance. We discovered previously unidentified mutations in the ligand-interacting surface binding loops (AB, CD, FG, and HI). Five combined mutations increased rigidity of the AB loop, as confirmed by NMR. When added to three independently identified CD and FG loop mutations that reduced the koff value by twofold, these mutations resulted in an overall selective 100-fold improvement in affinity. The structural basis of the evolved affinity was improved shape complementarity established by interloop (AB-CD) and intraloop (FG-FG) side chain interactions. The high affinity of the combinatorial domain 11 Fc fusion proteins functioned as ligand-soluble antagonists or traps that depleted pathological IGF2 isoforms from serum and abrogated IGF2-dependent signaling in vivo. An evolved and reengineered high-specificity M6P/IGF2R domain 11 binding site for IGF2 may improve therapeutic targeting of the frequent IGF2 gain of function observed in human cancer.