One of These Things is Not Like the Other: Tagging Cancerous Lung Tissue Gets Easier
New method may help clinicians detect non-small cell lung cancer much sooner, enabling diagnosis at earlier stages.
Of all cancers, lung cancer has the second highest incidence and the highest mortality rate, and non-small cell lung cancer (NSCLC) constitutes about 80 percent of all lung cancers. Yet radiographers have not had an effective means of visualizing NSCLC cells in patients. Currently a lung biopsy is the only reliable method of diagnosis.
Overexpression of a gene involved in the c-Met signaling pathway is known to enhance tumor initiation and growth, and the c-Met receptor has been used as a biomarker for imaging of other cancers, but not lung cancer. Previous biomarker-based methods have included monoclonal antibodies, but the uptake and clearance of these large molecules has been very slow. A c-Met receptor peptide has been used in optical imaging but not in nuclear imaging. Now a team at the Stanford University School of Medicine and Harbin Medical University in China have developed a radiotracer that labels NSCLC cells’ c-Met receptors for diagnostic imaging with speed and precision. Their study was published May 18 in the Journal of Nuclear Medicine.
The investigators developed a new peptide incorporating 99mTc-hydrazine nicotinamide cMBP for use with single-photon emission computed tomography (SPECT). First they showed in vitro that the peptide can differentiate between two NSCLC cell lines, H1993 (high expression of the c-Met receptor) and H1299 (no expression). They took SPECT images at half an hour and one hour after tracer dosing. Uptake of the tracer in the high-expressing cell line was far higher than in the other cell line, producing clear images of the high-expressing cell line and none of the other line.
Next, the researchers grafted human NSCLC tumor cells into mice and injected the tracer. Images taken half an hour after injection showed the same rapid tracer uptake in the high c-Met expressing cells and none in the non-C-Met expressing cells.
The team’s method may help clinicians detect NSCLC much sooner, making invasive screening biopsy unnecessary and enabling diagnosis at earlier stages. The tracer’s absorption and excretion were so fast that the authors suggest adding something to slow down the pharmacokinetics to give radiologists plenty of time to conduct the SPECT.