Advanced non-small cell lung cancer (NSCLC) is generally linked with a poor prognosis and one of the leading causes of cancer-related deaths worldwide.
Therapeutic blocking of the interaction between immune checkpoints programmed death-1 (PD-1) with its ligand PD-L1 is a promising approach to restore the anti-tumor immune response. This type of immunotherapy (Nivolumab, Pembrolizumab, Atezolizumab and Durvalumab) has shown improved clinical outcomes in different human cancers, including NSCLC. Unfortunately, still a high number of NSCLC patients are treated with immunotherapy without obtaining clinical benefit. The current use of PD-L1 expressed on tumor cells as sole predictive biomarker to guarantee the success of anti-PD-(L)1 immunotherapy falls short. Therefore, there is a high need for additional predictive biomarkers for a more precise prediction of therapy response in NSCLC patients.
For this purpose, we have performed MALDI mass spectrometry imaging (MSI) on responding and non-responding pretreatment biopsies of NSCLC patients that were treated with anti-PD-(L)1 immunotherapies. With MSI, a molecular profile (proteins, nucleic acids, lipids, etc.) can be generated from the tumor microenvironment while retaining the spatial distribution and without destroying the tissue morphology, making a correlation with histological data possible. This approach has led to the discovery of neutrophil defensin 1, 2 and 3 (also known as human neutrophil peptide (HNP) 1, 2 and 3) to be distinctive between the two response groups: HNPs are significantly higher expressed within the tumor biopsy of responding patients compared to nonresponding patients. These results were verified with both LC-MS/MS and traditional HNP-based immunohistochemical staining.
MSI seems a powerful tool to elucidate unknown response patterns that can lead to the discovery of new (predictive) biomarkers. The discovery of HNPs as additional predictive biomarkers (combined with PD-L1 screening) has led to a fourfold decrease of the false positive response rate (decreased from 64% to 16%; patent pending). This can guide a more precise future therapy decision in NSCLC patients. Finally, we provided insights into the biological activity of these three peptides as immune stimulatory effectors. This illustrates the power of mass spectrometry techniques for both discovery of new predictive biomarkers and potential anticancer therapeutics.