Abstract B46: Connective Tissue Growth Factor (CTGF/CCN2) is increased in pre-B acute lymphoblastic leukemia and confers a growth advantage within the bone marrow niche

Abstract

Abstract Introduction: Acute lymphoblastic leukaemia (ALL) is the most common form of cancer in children. Despite major improvements in cure rates, a significant number of patients still relapse. ALL originates in the bone marrow and cell-cell interactions in this microenvironment can alter disease progression and treatment efficacy. Connective tissue growth factor (CTGF/CCN2) is expressed at significantly higher levels in approximately 75% of pre-B ALL specimens compared to normal cells. CTGF is a secreted protein associated with the extracellular matrix. Because the role of CTGF in ALL is currently unknown, we developed in vivo model systems to assess the function of CTGF. Method: Pre-B ALL cell lines were derived from patient specimens. They were then modified using lentiviral and short hairpin (sh)RNA technology to express CTGF at elevated or at reduced levels. They were characterised by various in vitro technologies and were examined in a NOD/SCID xenograft model. Outcomes: Expression and secretion of high levels of CTGF in cell line PER-371 did not alter their proliferation rate in vitro. However, when xenografted in NOD/SCID mice, high CTGF-expressing PER-371 cells showed accelerated leukaemic development. The median survival was 70 days, compared to 89 days (p=0.03) for mice injected with PER-371 control cells that express basal levels of CTGF. Leukaemic cell infiltration was measured in the haemopoietic organs of mouse cohorts at various times during disease development. There were no significant differences in leukaemic cell infiltration early in disease, however, high CTGF-expressing PER-371 cells were significantly increased in the bone marrow approximately two weeks before full development of disease, compared to control PER-371 xenografts (44% vs 8%; p=0.01). This suggests that high levels of CTGF in these cells does not influence homing, but confers a growth advantage within the bone marrow niche. Reduced CTGF expression using shRNA significantly reduced proliferation in vitro in PER-371 (0.9%; p<0.005) and PER-377 (4.8%; p<0.005) cell lines compared to their respective controls. Conclusions: CTGF is elevated in approximately 75% of pre-B ALL specimens. We demonstrate that high CTGF confers a growth advantage of pre-B ALL cells within the bone marrow niche. Planned immunohistochemical studies aim to highlight possible differences in vasculature, location of disease or changes to the extracellular matrix. Citation Format: Julia E. Wells, Meegan Howlett, Heloise M. Halse, Jette Ford, Jasmin Heng, Amy L. Samuels, Catherine H. Cole, Ursula R. Kees. Connective Tissue Growth Factor (CTGF/CCN2) is increased in pre-B acute lymphoblastic leukemia and confers a growth advantage within the bone marrow niche. [abstract]. In: Abstracts: AACR Special Conference on Cellular Heterogeneity in the Tumor Microenvironment; 2014 Feb 26-Mar 1; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(1 Suppl):Abstract nr B46. doi:10.1158/1538-7445.CHTME14-B46