Characterization of the tumor microenvironment and liquid biopsy in head and neck and non-small cell lung cancer

Metastasis in cancer patients is reflected by measurable levels of circulating tumor cells (CTCs) in the blood of cancer patients. CTCs represent cancer cells from the primary and metastatic sites, thereby providing a comprehensive representation of the tumor burden of an individual patient. Recent advancements have shown that PD-1/PD-L1 immune checkpoint therapies have durable responses in a number of solid tumor types. Our study was designed to use multiple CTC enrichment platforms for the capture of CTCs and novel culture formulations for the ex vivo expansion of CTCs. Head and Neck cancer (n=350) and lung cancer (n=150) patients were recruited to investigate the prognostic role of CTCs. In parallel, a subset of HNC tumors were profiled using the NanoString GeoMx Digital Spatial Profiling (DSP) technology using a 44-plex antibody cocktail. We evaluated multiple CTC isolation technologies (CellSearch, filtration, CD45 depletion, Spiral, Straight and novel microfluidic chip technology) using matched patient samples which showed that epitope-independent CTC isolation captured a greater proportion of CTCs. Molecular alterations present in the primary tissue were confirmed in the CTCs by 3D-DNA FISH (EGFR-amplification, ALK-translocations). In HNC, the presence of CTC clusters associated with the development of distant metastatic disease (P=0.0313). HNC CTC-positive patients had shorter progression free survival (Hazard ratio [HR]: 4.946; 95% [CI]:1.571-15.57; P=0.0063) and PD-L1-positive CTCs were found to be significantly associated with worse outcome ([HR]:5.159; 95% [CI]:1.011-26.33; P=0.0485). In a proof of principle study, we were able to demonstrate for the first time, short-term patient derived CTC cultures outside the patient's body and exome sequencing of CTCs cultures confirmed the presence of mutational signatures consistent with The Cancer Genome Atlas (TCGA). Spatial characterization of the tumor microenvironment revealed immune subsets predictive of outcome to immunotherapy. Comprehensive characterization of the tumor microenvironment and liquid biopsy allows for the recapitulation of the molecular diversity present within the tumor, understanding of the disease progression and testing of therapies.