Cancer cell growth depends on high expression of cancer genes. Overexpression of epithelial growth factor receptor (EGFR) stimulates lung cancer cell growth. Anti-EGFR antibodies or tyrosine kinase inhibitors (TKIs) fail in most lung cancer patients. KRAS2 activation makes cancer cell proliferation independent of EGFR activity. As a result, treating lung cancer with anti-EGFR antibodies or TKIs fails when KRAS2 has been mutated. We hypothesize that determining KRAS2 cancer gene mutation status by external genetic PET imaging of mutant KRAS2 mRNA overexpression, as an adjunct to biopsy, will enable physicians to decide on alternatives to EGFR-directed therapies. We have imaged high levels of mutant KRAS2 mRNA and other oncogenes in malignant pancreas cancer xenografts. We designed radionuclide-chelator-spacer- peptide nucleic acid (PNA)-spacer-insulin-like growth factor 1 (IGF1) analogs to enable IGF1R-mediated cellular uptake and genetic radioimaging of mutant KRAS2 mRNA in suspect masses. We demonstrated sequence-specific PNA genetic imaging and quantitation of high levels of mutant KRAS2 mRNA in pancreas cancer xenografts after tail vein injection of 99mTc (SPECT) or 64Cu (PET) PNA-spacer-IGF1 probes. To extend this technology platform to lung cancer, we propose to carry out essential preclinical steps to maximize the sensitivity of imaging multiple mutants of KRAS2 mRNA with a codon 12 redundant chelator-KRAS2 genetic imaging agent in lung cancer xenografts. Our team includes an experienced radiopharmaceutical company, Molecular Targeting Technologies, which will submit an exploratory IND to FDA for a future trial of the KRAS2 genetic imaging agent in patients with suspect lung masses.
Specific Aim 1 : Test the sensitivity and specificity of a codon 12 multimutant KRAS2 genetic imaging agent in lung cancer xenografts. TJU will synthesize a novel KRAS2 genetic imaging agent designed to detect multiple KRAS2 codon 12 mutations, and control sequences. MTTI will purify and analyze large scale batches of KRAS2 genetic imaging agent and controls.
Specific Aim 2 : Determine whether genetic imaging of KRAS2 mRNA in lung cancer xenografts provides an early indication of the efficacy of antiproliferative chemotherapy. TJU will determine whether lowered KRAS2 mRNA, measured by genetic imaging, provides an earlier indication of the efficacy of antiproliferative chemotherapy, compared with [18F]FDG measurement of metabolic activity.
Specific Aim 3 : Obtain an eIND number from FDA for a future feasibility study. MTTI will acquire a dedicated cGMP batch of the KRAS2 genetic imaging agent, direct a microdose toxicology study in rats, compile and submit the eIND application for the KRAS2 genetic imaging agent to FDA, then address FDA questions and concerns. Early external imaging of lung cancer gene activity might (1) improve diagnosis of early lung cancer, (2) avoid biopsy trauma in patients with benign masses, (3) guide EGFR targeted therapy, and (4) ultimately reduce deaths from lung cancer.

Public Health Relevance

We propose to detect a particular activated cancer gene in lung tumors from outside the body by nuclear medicine genetic imaging. If KRAS2 cancer gene has been activated by mutation, therapies directed against epidermal growth factor receptor will fail. In a mouse lung cancer model, we will test for the possibility of KRAS2 cancer gene signals from lung tissues that are resistant to therapies directed against epidermal growth factor receptor. In the future, imaging multiple cancer genes might guide early treatment according to which cancer genes are active in solid tumors, and might even identify developing cancers before they form a tumor mass.

National Institute of Health (NIH)
National Cancer Institute (NCI)
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Special Emphasis Panel (ZRG1-SBIB-U (50))
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Menkens, Anne E
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Thomas Jefferson University
Schools of Medicine
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Sonar, Mahesh V; Wampole, Matthew E; Jin, Yuan-Yuan et al. (2014) Fluorescence detection of KRAS2 mRNA hybridization in lung cancer cells with PNA-peptides containing an internal thiazole orange. Bioconjug Chem 25:1697-708
Sanders, Jeffrey M; Wampole, Matthew E; Chen, Chang-Po et al. (2013) Effects of hypoxanthine substitution in peptide nucleic acids targeting KRAS2 oncogenic mRNA molecules: theory and experiment. J Phys Chem B 117:11584-95
Sanders, Jeffrey M; Wampole, Matthew E; Thakur, Mathew L et al. (2013) Molecular determinants of epidermal growth factor binding: a molecular dynamics study. PLoS One 8:e54136