Heart-type fatty acid-binding protein: an overlooked cardiac biomarker

Abstract

Cardiac troponins (cTn) are currently the standard of care for the diagnosis of acute coronary syndromes (ACS) in patients presenting to the emergency department (ED) with chest pain (CP). However, their plasma kinetics necessitate a prolonged ED stay or overnight hospital admission, especially in those presenting early after CP onset. Moreover, ruling out ACS in low-risk patients requires prolonged ED observation or overnight hospital admission to allow serial measurements of c-Tn, adding cost. Heart-type fatty acid-binding protein (H-FABP) is a novel marker of myocardial injury with putative advantages over cTn. Being present in abundance in the myocellular cytoplasm, it is released rapidly (<1?h) after the onset of myocardial injury and could potentially play an important role in both earlier diagnosis of high-risk patients presenting early after CP onset, as well as in risk-stratifying low-risk patients rapidly. Like cTn, H-FABP also has a potential role as a prognostic marker in other conditions where the myocardial injury occurs, such as acute congestive heart failure (CHF) and acute pulmonary embolism (PE). This review provides an overview of the evidence examining the role of H-FABP in early diagnosis and risk stratification of patients with CP and in non-ACS conditions associated with myocardial injury.

• Key messages

• Heart-type fatty acid-binding protein is a biomarker that is elevated early in myocardial injury

• The routine use in the emergency department complements the use of troponins in ruling out acute coronary syndromes in patients presenting early with chest pain

• It also is useful in risk stratifying patients with other conditions such as heart failure and acute pulmonary embolism.

     

Exosomes secreted by prostate cancer cells under hypoxia promote matrix metalloproteinases activity at pre-metastatic niches

Approximately, 30 000 men die from prostate cancer (PCa) every year in the United States, mainly due to the metastasis. Thus, the key events associated with PCa metastasis are under rigorous investigation, with recent studies showing that preparation of pre-metastatic niches (PMN) in distant organs is an important step. However, the molecular basis for PMN preparation is still unclear. Hypoxia in primary tumors promotes aggressiveness; however, its precise role in metastasis is not clear. We recently reported that exosomes secreted by PCa cells under hypoxia promote stemness and invasiveness in naïve PCa cells; however, whether these extracellular vesicles also influence PMN remains unknown. In the present study, we isolated exosomes from human PCa PC3 cells under normoxic (21% O₂, exosomes secreted under normoxic condition [Exo^Normoxic]) and hypoxic (1% O₂, exosomes secreted under hypoxic condition [Exo^Hypoxic]) conditions, and characterized their effect (10 µg exosomes, intraperitoneal (IP) treatment every 48 hours for 4 weeks) on key biomarkers associated with PMN in nude mice. Whole animal fluorescence imaging showed that Exo^Hypoxic treatment promotes matrix metalloproteinases (MMPs) activity in several putative metastatic sites. Histological studies confirmed that Exo^Hypoxic treatment enhanced the level of MMP2, MMP9, and extracellular matrix proteins (fibronectin and collagen) as well as increased the number of CD11b+ cells at selective PMN sites. Furthermore, proteomic profiling of exosomes by liquid chromatography/mass spectrometry identified cargo proteins in Exo^Normoxic and Exo^Hypoxic as well as distinct canonical pathways targeted by them. These results suggest that exosomes secreted by PCa cells under hypoxia plausibly remodel distant PMN, and thus, could be a potential target to control metastatic PCa.