Very Late Antigen-4 (α<inf>4</inf>β<inf>1</inf> Integrin) Targeted PET Imaging of Multiple Myeloma

Biomedical imaging techniques such as skeletal survey and 18F-fluorodeoxyglucose (FDG)/Positron Emission Tomography (PET) are frequently used to diagnose and stage multiple myeloma (MM) patients. However, skeletal survey has limited sensitivity as it can detect osteolytic lesions only after 30-50% cortical bone destruction, and FDG is a marker of cell metabolism that has limited sensitivity for intramedullary lesions in MM. Targeted, and non-invasive novel probes are needed to sensitively and selectively image the unique molecular signatures and cellular processes associated with MM. Very late antigen-4 (VLA-4; also called α4β1 integrin) is over-expressed on MM cells, and is one of the key mediators of myeloma cell adhesion to the bone marrow (BM) that promotes MM cell trafficking and drug resistance. Here we describe a proof-of-principle, novel molecular imaging strategy for MM tumors using a VLA-4 targeted PET radiopharmaceutical, 64Cu-CB-TE1A1P-LLP2A. Cell uptake studies in a VLA-4-positive murine MM cell line, 5TGM1, demonstrated receptor specific uptake (P<0.0001, block vs. non-block). Tissue biodistribution at 2 h of 64Cu-CB-TE1A1P-LLP2A in 5TGM1 tumor bearing syngeneic KaLwRij mice demonstrated high radiotracer uptake in the tumor (12±4.5%ID/g), and in the VLA-4 rich organs, spleen (8.8±1.0%ID/g) and marrow (11.6±2.0%ID/g). Small animal PET/CT imaging with 64Cu-CB-TE1A1P-LLP2A demonstrated high uptake in the 5TGM1 tumors (SUV 6.6±1.1). There was a 3-fold reduction in the in vivo tumor uptake in the presence of blocking agent (2.3±0.4). Additionally, 64Cu-CB-TE1A1P-LLP2A demonstrated high binding to the human MM cell line RPMI-8226 that was significantly reduced in the presence of the cold targeting agent. These results provide pre-clinical evidence that VLA-4-targeted imaging using 64Cu-CB-TE1A1P-LLP2A is a novel approach to imaging MM tumors. © 2013 Soodgupta et al

Mammary stem cells, self-renewal pathways, and carcinogenesis

The mammary gland epithelial components are thought to arise from stem cells that undergo both self-renewal and differentiation. Self-renewal has been shown to be regulated by the Hedgehog, Notch, and Wnt pathways and the transcription factor B lymphoma Mo-MLV insertion region 1 (Bmi-1). We review data about the existence of stem cells in the mammary gland and the pathways regulating the self-renewal of these cells. We present evidence that deregulation of the self-renewal in stem cells/progenitors might be a key event in mammary carcinogenesis. If 'tumor stem cells' are inherently resistant to current therapies, targeting stem cell self-renewal pathways might provide a novel approach for breast cancer treatment

Adhesion molecules on human myeloma cells: significant changes in expression related to malignancy, tumor spreading, and immortalization

International audienceIn order to evaluate putative changes of major adhesion molecule expression on plasma cells (PCs) associated with malignant transformation, tumor spreading, and immortalization, we have quantified and compared the expression of CD56, CD44, CD11a, CD49e, and CD45 RO/RA on normal PCs, malignant PCs from multiple myeloma patients in chronic phase, in accelerated phase with or without extramedullary progression, and from human myeloma cell lines. Plasma cell phenotype was defined with the use of two-color immunofluorescence in combination with B-B4 or anti-CD38 antibodies. We found that all the adhesion antigens were expressed on normal PCs. Malignancy was characterized by an overexpression of CD56, whereas extramedullary spreading was associated with a dramatic down expression of CD56. Although CD44 remained unchanged, the subpopulation of PCs expressing CD11a, CD49e, and CD45RA/RO were significantly reduced during malignancy, and each of these negative subpopulations increased during disease acceleration. We demonstrated that CD11a and CD49e expression were correlated and defined the same subpopulation of PCs. The phenotype of HMCLs was similar to the expression profile of patients in accelerated phase with extramedullary spreading. In conclusion, we show that significant changes of PC phenotype were associated with malignancy, were correlated with the disease evolution, and could be of diagnostic and prognostic value in individuals with monoclonal gammopathy and patients with multiple myeloma