Nuclear medicine communications
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It is well established that accumulation of 99Tcm-sestamibi (99Tcm-MIBI) is much higher in sensitive than multidrug-resistant tumour cells expressing the permeability glycoprotein 170 (Pgp 170) as well as a multidrug-resistance related protein (MRP). Thus 99Tcm-MIBI is a good candidate for diagnosing the multidrug-resistance phenotype by in vivo imaging. However, the blood clearance of 99Tcm-MIBI is too rapid to achieve optimal accumulation in tumours and uptake in the liver, spleen, heart and muscle is too high for it to be an excellent in vivo tumour tracer. ⋯ In both experimental cases, 99Tcm-MIBI accumulation was similar to that obtained in the presence of free 99Tcm-MIBI only: it was much higher in sensitive than in resistant Pgp 170-positive and MRP-positive cells. Encapsulation in liposomes does not alter the potency of 99Tcm-MIBI to distinguish the sensitive and resistant tumour cells. Our results suggest that future studies should assess the usefulness of the encapsulated form of 99Tcm-MIBI for in vivo imaging of tumours.