Protein biomarker validation via proximity ligation assays.

The ability to detect minute amounts of specific proteins or protein modifications in blood as biomarkers for a plethora of human pathological conditions holds great promise for future medicine. Despite a large number of plausible candidate protein biomarkers published annually, the translation to clinical use is impeded by factors such as the required size of the initial studies, and limitations of the technologies used. The proximity ligation assay (PLA) is a versatile molecular tool that has the potential to address some obstacles, both in validation of biomarkers previously discovered using other techniques, and for future routine clinical diagnostic needs. The enhanced specificity of PLA extends the opportunities for large-scale, high-performance analyses of proteins. Besides advantages in the form of minimal sample consumption and an extended dynamic range, the PLA technique allows flexible assay reconfiguration. The technology can be adapted for detecting protein complexes, proximity between proteins in extracellular vesicles or in circulating tumor cells, and to address multiple post-translational modifications in the same protein molecule. We discuss herein requirements for biomarker validation, and how PLA may play an increasing role in this regard. We describe some recent developments of the technology, including proximity extension assays, the use of recombinant affinity reagents suitable for use in proximity assays, and the potential for single cell proteomics. This article is part of a Special Issue entitled: Biomarkers: A Proteomic Challenge.

Growth differentiation factor 15: a prognostic marker for recurrence in colorectal cancer.

BACKGROUND: Growth differentiation factor 15 (GDF15) belongs to the transforming growth factor beta superfamily and has been associated with activation of the p53 pathway in human cancer. The aim of this study was to assess the prognostic value of GDF15 in patients with colorectal cancer (CRC). METHODS: Immunohistochemistry and tissue microarrays were used to analyse GDF15 protein expression in 320 patients with CRC. In a subgroup of 60 patients, the level of GDF15 protein in plasma was also measured using a solid-phase proximity ligation assay. RESULTS: Patients with CRC with moderate to high intensity of GDF15 immunostaining had a higher recurrence rate compared with patients with no or low intensity in all stages (stages I-III) (HR, 3.9; 95% CI, 1.16-13.15) and in stage III (HR, 10.32; 95% CI, 1.15-92.51). Patients with high plasma levels of GDF15 had statistically shorter time to recurrence (P=0.041) and reduced overall survival (P=0.002). CONCLUSION: Growth differentiation factor 15 serves as a negative prognostic marker in CRC. High expression of GDF15 in tumour tissue and high plasma levels correlate with an increased risk of recurrence and reduced overall survival.

Corona mortis: an anatomical study with clinical implications in approaches to the pelvis and acetabulum.

The "corona mortis" is an anatomical variant, an anastomosis between the obturator and the external iliac or inferior epigastric arteries or veins. It is located behind the superior pubic ramus at a variable distance from the symphysis pubis (range 40-96 mm). The name "corona mortis" or crown of death testifies to the importance of this feature, as significant hemorrhage may occur if accidentally cut and it is difficult to achieve subsequent hemostasis. It constitutes a hazard for orthopedic surgeons especially in the anterior approach to the acetabulum. We carried out forty cadaver dissections (80 hemi-pelvises) through the ilioinguinal approach. A vascular anastomosis was found in 83% of specimens. Of these, 60% had a large diameter (>3 mm) channel along the posterior aspect of the superior pubic ramus. In clinical practice, however, 492 anterior approaches (to the best of our knowledge the largest series described) have been carried out over the last 15 years by the senior author (MB) and only five of these problematic vessels were discovered, and in only two cases was there troublesome bleeding. This study confirms a paradox: in anatomical dissections a large vessel was identified behind the superior pubic ramus, whereas in clinical practice this vessel does not seem to be as great a threat as initially perceived. Orthopedic surgeons planning an anterior approach to the acetabulum, such as the ilioinguinal or the intrapelvic approach (modified Stoppa), have to be cautious when dissecting near the superior pubic ramus. Despite the high prevalence of these large retropubic vessels in the dissecting room, surgeons should exercise caution but not alter their surgical approach for fear of excessive hemorrhage.

Fractures of the acetabulum in osteogenesis imperfecta.

We describe two patients aged 16 and 25 years with osteogenesis imperfecta who sustained displaced fractures of the acetabulum following minor trauma. The femoral heads were deformed by impact against the acetabular margin and both cases underwent surgical reconstruction. The quality of the bone and soft tissues made the operations challenging. There were potential complications specific to osteogenesis imperfecta, including bleeding, the creation of secondary fracture lines and shredding of the soft-tissue. The cases provide useful guidelines for addressing these difficulties.

Beware of the ulno-palmar distal radial fragment.

Five patients sustained isolated fractures of the ulnopalmar rim of the distal radius. In three cases the fragment was small and was classed as an avulsion fracture of the short radiolunate ligament. Palmar wrist subluxation occurred in all cases, four during treatment in a cast or splint. The ulnopalmar rim of the distal radius contributes to the stability of the radiocarpal joint and fractures in this region merit particular attention.

Does the term scaphocapitate syndrome need to be revised? A report of 6 cases.

This is a retrospective study of six patients with displaced fractures of the neck of the capitate. In four of the six patients the diagnosis was delayed by at least 1 week. After open reduction and internal fixation the results were assessed as excellent (three cases), fair (two cases) or poor (one case). In all cases there was a concomitant injury to the radial side of the wrist: in four cases this was a fracture of the waist of the scaphoid. In five of the six cases there was also an injury to the ulnar side of the wrist. As a scaphoid fracture does not always occur with the fracture of the neck of the capitate, we consider the term "scaphocapitate syndrome" inappropriate for this injury.

Effectiveness of suction drainage after primary or revision total hip and total knee arthroplasty.

Postoperative suction drainage of a surgical wound is aimed at evacuation of wound hematoma. This study evaluated the effectiveness of suction drainage in joint replacement surgery. Surgical wounds in 206 patients with primary or revision hip and knee arthroplasty were assessed according to a set criteria. Forty-eight hours postoperatively, wound hematoma and exudate formation were not related to the use of suction drains. A greater tendency of wound oozing was seen in revision hip arthroplasty performed with postoperative suction drainage. Therefore, postoperative suction drainage did not affect hematoma formation or wound oozing and is thus considered an unnecessary practice.