Early detection of cancer often results in a much better prognosis. In the case of non-small cell lung cancer (NSCLC), early screening can be done through low dose computed tomography (LDCT) for those with high-risk. However, after being diagnosed with pulmonary nodules (PN) in the lung, many patients must undergo an invasive, expensive procedure to diagnose whether they are benign nodules (BN) or malignant nodules (MN). As a very high number of PNs turn out to be benign, new alternative follow-up screenings could be very useful in avoiding undue harm and stress to patients.
The laboratory of Dr. McGarry Houghton (Clinical Research Division) in collaboration with the laboratory of Dr. Paul Lampe (Public Health Sciences) published a study in the American Journal of Respiratory and Critical Care Medicine detailing an alternative screening method. The scientists, led by Drs. Kristin Lastwika and Julia Kargl, looked at cancer antigen-specific antibodies in patients with PN in the lung. Since B cells infiltrate tumors, bind to tumor antigens, and then secrete antigen-specific antibodies, the researchers decided to generate a test which would determine whether PN are malignant by screening patient blood for specific antibodies.
Image provided by Dr. Kristin Lastwika
In order to find which autoantibodies might be the most specific for MN, the scientists isolated CD19+ B cells from NSCLC samples and maintained them in culture. They harvested the supernatant containing antibodies secreted by the B cells. They then lysed the B cells in the culture and combined the lysate with the supernatant to create autoantibody-containing B cell extract (BCE). The authors then incubated either BCE or plasma on the Human Proteome (HuProt) array with ~17,000 human proteins. Protein targets with antibodies bound were detected by secondary fluorescent antibodies.
In order to narrow down targets that would be clinically relevant, the scientists compared these results with the targets bound by plasma autoantibodies in samples from patients with BN or MN. BN and MN plasma samples matched by gender, age, and pack years of smoking showed only 14% autoantibodies in common, suggesting that they could detect malignancy based on plasma autoantibodies. The scientists used this data to narrow it down to 13 targets of interest which were most specifically bound by autoantibodies found in patients with MN and not in patients with BN.
Not all plasma autoantibodies are free to bind protein array targets, as they are often found bound to antigen. In order to detect these autoantibody-antigen complexes, Dr. Houghton and colleagues created an antibody array with commercial antibodies against the targets of interest. They tested which of them would bind to plasma autoantibody-antigen complexes and found 11 of the 13 targets with higher levels of bound autoantibodies in MN than BN.
The authors validated these results by testing 250 independent plasma samples and found a 4-marker panel that was the most accurate in predicting malignant nodules. “This is the first study to demonstrate that autoantibodies produced by tumor-infiltrating B cells are highly specific for lung cancer antigens and are readily identifiable in peripheral blood,” Dr. Lastwika said. “Our panel of autoantibodies could be a cost-effective and non-invasive approach to help clinicians accurately diagnose early stage lung cancer during LDCT screening.”
“Additionally, our high-throughput pipeline is a novel way to comprehensively discover both free and antigen-complexed autoantibodies that serve as excellent blood biomarkers.” Dr. Lastwika said. “While the current study focused on non-small cell lung carcinoma, we are also discovering highly specific autoantibody panels for other types of lung cancer all in effort to detect cancer earlier.”
Lastwika KJ, Kargl J, Zhang Y, Zhu X, Lo E, Shelley D, Ladd JJ, Wu W, Kinahan P, Pipavath SNJ, Randolph TW, Shipley M, Lampe PD, Houghton AM. 2018. Tumor-Derived Autoantibodies Identify Malignant Pulmonary Nodules. American journal of respiratory and critical care medicine. doi: 10.1164/rccm.201804-0628OC. [Epub ahead of print].
Funding for this research was provided by the National Cancer Institute.
Fred Hutch/UW Cancer Consortium members Paul Kinahan, Timothy Randolph, Paul Lampe, and McGarry Houghton contributed to this research.