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GPI-PLC (glycosylphosphatidylinositol-specific phospholipase C) is expressed in bloodstream-form Trypanosoma brucei, a protozoan that causes human African trypanosomiasis. Loss of genes encoding GPI-PLC reduces the virulence of a pleomorphic strain of the parasite, for reasons that are not clear. In the present paper, we report that GPI-PLC stimulates endocytosis of transferrin by 300–500%. Surprisingly, GPI-PLC is not detected at endosomes, suggesting that the enzyme does not interact directly with the endosomal machinery. We therefore hypothesized that a diffusible product of the GPI-PLC enzyme reaction [possibly DAG (diacylglycerol)] mediated the biological effects of the protein. Two sets of data support this assertion. First, a catalytically inactive Q81L mutant of GPI-PLC, expressed in a GPI-PLC-null background, had no effect on endocytosis, indicating that enzyme activity is essential for the protein to stimulate endocytosis. Secondly, the exogenous DAGs OAG (1-oleyl-2-acetyl-sn-glycerol) and DMG (dimyristoylglycerol) independently stimulated endocytosis of transferrin. Furthermore, the DAG mimic PMA, a phorbol ester, also activated endocytosis in T. brucei. DAG-stimulated endocytosis is a novel pathway in the trypanosome. We surmise that (i) GPI-PLC regulates transferrin endocytosis in T. brucei, (ii) GPI-PLC is a signalling enzyme, and (iii) DAG is a second messenger for GPI-PLC. We propose that regulation of endocytosis is a physiological function of GPI-PLC in bloodstream T. brucei. [ABSTRACT FROM AUTHOR]

Background: Currently, there are no imaging predictors of immunotherapy outcome in hepatocellular carcinoma (HCC). The study aim was to determine if stiffness changes measured by magnetic resonance elastography (MRE) can be a predictor of immunotherapy response in patients with advanced HCC. Materials and methods: This was a prospective study of 15 patients with biopsy proven-advanced HCC treated with Pembrolizumab. All patients had liver MRE and liver biopsy at baseline and at 6 weeks of therapy. Change in HCC stiffness on MRE was compared with overall survival (OS), time to disease progression (TTP), and number of intratumoral CD3+ T lymphocytes. Analysis was performed using descriptive statistics and Spearman correlation (R); p-value < 0.05 was considered statistically significant. Results: Nine patients were evaluable. Median age was 71 years (range, 54–78). Etiology of liver disease was HCV (n = 4), HBV (n = 1) and NASH (n = 4). Median OS and TTP were 44 weeks and 13 weeks, respectively. Average baseline HCC stiffness and change in HCC stiffness were 5.0 kPa and 0.12 kPa, respectively. In contrast, average non-tumor liver stiffness was 3.2 kPa, and did not significantly change at 6 weeks (p = 0.42). Average size of measured tumor and change in size were 4 cm and − 0.32 cm, respectively. Change in HCC stiffness at 6 weeks correlated significantly with OS (R = 0.81), and TTP (R = 0.88,p < 0.01). Abundance of intratumoral T lymphocytes on tumor biopsy correlated significantly with HCC stiffness (R = 0.79,p = 0.007). Conclusion: Our pilot MRE data suggests early change in tumor stiffness may be an indicator of immunotherapy response in patients with advanced HCC. [ABSTRACT FROM AUTHOR]