Novel synthesis of fluorochrome-coupled zoledronate with preserved functional activity on gamma/delta T cells and tumor cells

In addition to their effects on bone resorption, nitrogen-containing bisphosphonates (N-BP) selectively activate gamma delta T cells, an innate-like immune cell population with potent anti-tumor activity. N-BP stimulate gamma delta T cells through induction of intracellular accumulation of mevalonate pathway-derived pyrophosphates, which are strong and selective antigens for human gamma delta T cells. The most potent among several classes of N-BP is zoledronate (ZOL). To study the uptake of ZOL and its immunological consequences in the gamma delta T cell/tumor cell interplay, we have synthesized a novel fluorescently labeled ZOL derivative termed FluorZOL by covalently coupling ZOL to carboxyfluorescein succinidimyl ester. Here we describe in detail the synthesis of FluorZOL and we further show that FluorZOL is functionally fully active as revealed by the selective expansion of gamma delta T cells and the enhancement of tumor cell lysis by gamma delta T cells.