Inhibition of chronic lymphocytic leukemia progression by full-length chromogranin A and its N-terminal fragment in mouse models

Mimma Bianco,Eleonora Dondossola,Luca Generoso,Federico Caligaris-Cappio,Pamela Ranghetti,Angelo Corti,Maria T.S Bertilaccio,Barbara Colombo,Paolo Ghia,Emma Assi,Cristina Scielzo,Lydia Scarfò,Anna Gasparri,Maurilio Ponzoni

doi:10.18632/oncotarget.9407

Abstract

Chronic lymphocytic leukemia (CLL) is characterized by the accumulation of leukemic B cells in peripheral blood, bone marrow (BM) and lymphoid tissues, and by their recirculation between these compartments. We observed that circulating chromogranin A (CgA) and its N-terminal fragment (called vasostatin-1, CgA1-76), two neuroendocrine secretory polypeptides that enhance the endothelial barrier function, are present in variable amounts in the blood of CLL patients. Studies in animal models showed that daily administration of full-length human CgA1-439 (0.3 μg, i.v., or 1.5 μg/mouse, i.p.) can reduce the BM/blood ratio of leukemic cells in Eμ-TCL1 mice, a transgenic model, and decrease BM, lung and kidney infiltration in Rag2−/−γc−/− mice engrafted with human MEC1 CLL cells, a xenograft model. This treatment also reduced the loss of body weight and improved animal motility. In vitro, CgA enhanced the endothelial barrier integrity and the trans-endothelial migration of MEC1 cells, with a bimodal dose-response curve. Vasostatin-1, but not a larger fragment consisting of N-terminal and central regions of CgA (CgA1-373), inhibited CLL progression in the xenograft model, suggesting that the C-terminal region is crucial for CgA activity and that the N-terminal domain contains a site that is activated by proteolytic cleavage. These findings suggest that circulating full-length CgA and its fragments may contribute to regulate leukemic cell trafficking and reduce tissue infiltration in CLL.

Highlights

Human chromogranin A (CgA) is a 439-residue long protein stored in the secretory granules of manyendocrine cells and neurons and released in the blood of normal subjects at sub-nanomolar levels [1, 2]
The results show that Chronic lymphocytic leukemia (CLL) patients had increased plasma levels of CgA, compared to normal subjects, those >70-year-old or those treated with proton pump inhibitors (Figure 1A)
When we excluded patients treated with pump inhibitors (PPI) or with renal failure (RF), two conditions known to be associated with increased CgA levels [2, 4,5,6,7,8,9,10,11, 27], we still observed a significant increase of CgA (Figure 1A), suggesting that CLL is a condition per se sufficient to enhance the CgA levels

Summary

Introduction

Human chromogranin A (CgA) is a 439-residue long protein stored in the secretory granules of many (neuro)endocrine cells and neurons and released in the blood of normal subjects at sub-nanomolar levels [1, 2]. CgA has an intracellular function in secretory granule biogenesis [12, 13], as well as important extracellular functions as a precursor of various bioactive peptides involved in the regulation of metabolism, innate immunity, cardiovascular system, vascular contractility, and endothelial barrier function [1, 2]. Using murine models of mouse mammary adenocarcinomas and melanomas we have shown that full-length CgA and VS-1 can enhance the endothelial barrier function and reduce the trans-endothelial migration of tumor cells, thereby reducing the trafficking of cancer cells from tumor-to-blood and from blood-to-tumor/ normal tissues (i.e. the metastasis and the tumor “selfseeding” processes) [19, 20]

Methods

Results

Conclusion