Modification of peptide nucleic acid (PNA) monomers

Project information

  • Publication: An Efficient, Convenient Solid-Phase Synthesis of Amino Acid Modified PNA Monomers, Baghavathy S. Balaji, Fabio Gallazzi, Fang Jia, and Michael R. Lewis, BioConjugate Chem., 2006, 17, 551 – 558.

An efficient and highly versatile method for the synthesis of amino acid-modified peptide nucleic acid (PNA) monomers is developed. By using solid-phase Fmoc techniques, such monomers can be assembled readily in a stepwise manner and obtained in high yield with minimal purification. Protected neutral hydrophilic, acidic, and basic amino acids were coupled to the resin. The mild reaction conditions utilized were compatible with sensitive and labile functional groups. Two of these PNA monomers were incorporated with high coupling efficiency into a variety of modified PNA oligomers, including four tetradecamers designed to target bcl-2 mRNA.

Molecular imaging of bcl-2 using 111In-Labeled PNA–Peptide Conjugates

Project information

  • Publication: Molecular Imaging of bcl-2 Expression in Small Lymphocytic Lymphoma Using 111In-Labeled PNA–Peptide Conjugates, Fang Jia, Said D. F., Fabio Gallazzi, B. S. Balaji, Mark Hannink, Susan Z. Lever, Timothy J. Hoffman, and Michael R. Lewis, J. Nucl. Med., 2008, 49, 430-438.

(Top) MicroSPECT/CT im- ages of 111In-DOTA–PNA–peptide conju- gates in Mec-1–bearing SCID mice (n 5 3). (A) 111In-DOTA-Tyr3-octreotate (1 h). (B) 111In-DOTA-anti-bcl-2-PNA-Tyr3- octreotate (48 h). (C) 11 1In-DOTA- nonsense-PNA-Tyr3-octreotate (48 h). (D ) 111 In-D OTA-anti- bcl - 2 -P NA- Ala[3,4,5,6] (48 h). (Bottom) Correspond- ing transaxial slices through the centers of the tumors.

The bcl-2 gene is overexpressed in non-Hodgkin’s lymphoma (NHL), such as small lymphocytic lymphoma (SLL), and many other cancers. Noninvasive imaging of bcl-2 expression has the potential to identify patients at risk for relapse or treatment failure. The purpose of this study was to synthesize and evaluate radiolabeled peptide nucleic acid (PNA)-peptide conjugates targeting bcl-2 gene expression. An 111In-labeled PNA complementary to the translational start site of bcl-2 messenger RNA was attached to Tyr3-octreotate for somatostatin receptor-mediated intracellular delivery. This new111In-labeled antisense PNA–peptide conjugate demonstrated proof of principle for molecular imaging of bcl-2 expression in a new mouse model of human SLL. This imaging agent may be useful for identifying NHL patients at risk for relapse and conventional treatment failure.

Copper-64-labeled anti-bcl-2 PNA-peptide conjugates

Project information

  • Publication: Copper-64-labeled anti-bcl-2 PNA-peptide conjugates selectively localize to bcl-2-positive tumors in mouse models of B-cell lymphoma, Fang Jia, Baghavathy S. Balaji, Fabio Gallazzi, Michael R. Lewis, Nucl. Med. Biol., 2015, 42, 809-15 . Appeared in the cover page.

Fifteen-minute micro-PET/CT scans of mice bearing either Mec-1 or Ramos tumors. The mice were administered isoflurane anesthesia then 250 μCi of [64Cu]DOTA-anti-bcl-2- PNA-Ts-Tyr3-octreotate. Arrows indicate the locations of tumors.

The bcl-2 gene is overexpressed in non-Hodgkin's lymphoma (NHL). In order to reduce normal organ accumulation and improve imaging contrast of our earlier reported [111In]DOTA-anti-bcl-2-PNA-Tyr3-octreotate, we modified the monomers with neutral hydrophilic (serine, TS) or negatively charged (aspartic acid, TD) residues as substitutes for glycine at T14 in the PNA sequence. The parent and modified PNA-peptide conjugates were labeled with 64Cu and evaluated in biodistribution studies and high resolution PET/CT imaging of SCID mice bearing bcl-2-postive Mec-1 xenografts as well as bcl-2-negative Ramos xenografts.