Radiohybridization PET Imaging of KRAS G12D mRNA expression in human pancreas cancer xenografts with [64Cu]DO3A-Peptide nucleic acid-peptide nanoparticles

There is a compelling need to image pancreas cancer at an early stage. Human pancreas cancer cells display elevated levels of KRAS protein due to high copy number: of KRAS mRNA, and elevated levels of insulin-like growth factor 1 receptor (IGFIR) due to overexpression of IGFIR mRNA. Therefore we hypothesized that pancreas cancer could be detected in vivo with a single probe that targets both KRAS mRNA and IGFI R Because positron emission tomography (PET) is a sensitive imaging technique, we designed a probe incorporating the positron-emitting nuclide (CU)-C-64. The KRAS-specific hybridization probe consisted of 1,4,7-tris(carboxymethylaza)cyclododecane-10-azc acetyl (DO3A) on the N-terminus of a peptide nucleic acid (PNA) hybridization sequence (GCCATCAGCTCC) linked to a cyclized IGFl peptide analog (D-Cys-Ser-Lys-Cys) on the C-terminus, for IGFI R-mediated endocytosis. A series of such KRAS radiohybridizatio, probes with 0, 1, 2 or 3 mismatches to KRAS G12D mRNA, including exact matches t( wild type KRAS mRNA and KRAS G12V mRNA, along with a double D(Ala) replacement IGF1 peptide control, were assembled by continuous solid phase synthesis. To test the: hypothesis that KRAS-IGF1 dual probes could specifically image KRAS mRNA expres sion noninvasively in human IGFl R-overexpressing AsPCl pancreas cancer xenograft in immunocompromised mice, [64CU]PNA radiohybridization probes and controls were administered by tail vein. The [Cu-64]KRASIGFI radiohybridization probe yielded strong tumor contrast in PET images, 8.6 +/- 1.4-fold more intense in the center of human, pancreas cancer xenografts than in the contralateral muscle at 4 h post-injection. Control experiments with single base KRAS mismatches, an IGF1 peptide mismatch, and a breast! cancer xenograft lacking KRAS activation yielded weak tumor contrast images. These, experiments are consistent with our hypothesis for noninvasive PET imaging of KRA. oncogene expression in pancreas cancer xenografts. Imaging oncogene mRNAs wits radiolabel-PNA-peptide nanoparticles might provide specific genetic characterization c preinvasive and invasive pancreas cancers for staging and choice of therapy.