Person:

Tseng, Jen-Chieh

Many fluorescent sensors are currently available for in vitro bio-physiological microscopic imaging. The ability to label cells in living animals with these fluorescent sensors would help translate some of these assays into in vivo applications. To achieve this goal, the first step is to establish a method for selectively labeling target cells with exogenous fluorophores. Here we tested whether the HaloTag® protein tagging system provides specific labeling of xenograft tumors in living animals. After systemic delivery of fluorophore-conjugated ligands, we performed whole animal planar fluorescent imaging to determine uptake in tag-expressing HCT116 xenografts. Our results demonstrate that HaloTag ligands containing red or near-infrared fluorophores have enhanced tumor uptake and are suitable for non-invasive in vivo imaging. Our proof-of-concept results establish feasibility for using HaloTag technology for bio-physiological imaging in living animals.

T cell acute lymphoblastic leukemia (T-ALL) is an aggressive cancer of immature T cells that often shows aberrant activation of Notch1 and PI3K–Akt pathways. Although mutations that activate PI3K–Akt signaling have previously been identified, the relative contribution of growth factor-dependent activation is unclear. We show here that pharmacologic inhibition or genetic deletion of insulin-like growth factor 1 receptor (IGF1R) blocks the growth and viability of T-ALL cells, whereas moderate diminution of IGF1R signaling compromises leukemia-initiating cell (LIC) activity as defined by transplantability in syngeneic/congenic secondary recipients. Furthermore, IGF1R is a Notch1 target, and Notch1 signaling is required to maintain IGF1R expression at high levels in T-ALL cells. These findings suggest effects of Notch on LIC activity may be mediated in part by enhancing the responsiveness of T-ALL cells to ambient growth factors, and provide strong rationale for use of IGF1R inhibitors to improve initial response to therapy and to achieve long-term cure of patients with T-ALL.