Lung Cancer Research Today is a free monthly online journal that collates and summarizes the latest research about Lung Cancer, including details on symptoms, smoking, genetics, treatment, causes.

Tumor imaging using technetium-99m bound to pH-sensitive peptides.

Mata JE, Dyal LA, Slauson ME, Summerton JE, Loehr C, Tyson AR, Rodriguez-Proteau R, Gustafson SB

Department of Biomedical Sciences, College of Veterinary Medicine, Oregon State University, Corvallis, Oregon 97331, USA. john.mata@oregonstate.edu

Solid tumors often display metabolic abnormalities that consistently produce low pH in the extracellular space of poorly perfused tissue. These acidic regions may provide a mechanism for drug targeting. Peptides have been designed in such a manner that they exist in an anionic hydrophilic form at the pH of normal tissues, but then undergo a sharp transition to a non-ionic lipophilic form at reduced pH. Peptides were labeled with fluorescein or technetium-99m (99mTc) and evaluated in vitro and in two murine models of cancer. Our studies suggest that PAP-1, an 18 amino acid pH activated peptide with a pH of transition between hydrophilic and lipophilic forms (pT) of 6.4, will deliver fluorescein and 99mTc to tumors. Activation of PAP-1 by low pH and penetration into the plasma membrane of cells and tumors were confirmed using flow cytometry, fluorescence microscopy, and gamma scintigraphy. These results support our central hypothesis that PAP-1 may enable the selective delivery of macromolecules to tumors. This technology has potential for exploiting a common property of tumors to achieve highly specific medical intervention.

Published 10 December 2007 in Nanomedicine, 3(4): 297-305.
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