Rearranged EML4-ALK fusion transcripts sequester in circulating blood platelets and enable blood-based crizotinib response monitoring in non-small-cell lung cancer

Abstract

Purpose: Non-small-cell lung cancers harboring EML4-ALK rearrangements are sensitive to crizotinib. However, despite initial response, most patients will eventually relapse, and monitoring EML4-ALK rearrangements over the course of treatment may help identify these patients. However, challenges associated with serial tumor biopsies have highlighted the need for blood-based assays for the monitoring of biomarkers. Platelets can sequester RNA released by tumor cells and are thus an attractive source for the non-invasive assessment of biomarkers. Methods: EML4-ALK rearrangements were analyzed by RT-PCR in platelets and plasma isolated from blood obtained from 77 patients with non-small-cell lung cancer, 38 of whom had EML4-ALK-rearranged tumors. In a subset of 29 patients with EML4-ALK-rearranged tumors who were treated with crizotinib, EML4-ALK rearrangements in platelets were correlated with progression-free and overall survival. Results: RT-PCR demonstrated 65% sensitivity and 100% specificity for the detection of EML4-ALK rearrangements in platelets. In the subset of 29 patients treated with crizotinib, progression-free survival was 3.7 months for patients with EML4-ALK+ platelets and 16 months for those with EML4-ALK− platelets (hazard ratio, 3.5; P = 0.02). Monitoring of EML4-ALK rearrangements in the platelets of one patient over a period of 30 months revealed crizotinib resistance two months prior to radiographic disease progression. Conclusions: Platelets are a valuable source for the non-invasive detection of EML4-ALK rearrangements and may prove useful for predicting and monitoring outcome to crizotinib, thereby improving clinical decisions based on radiographic imaging alone.

Possible application of circulating free tumor DNA in non-small cell lung cancer patients

“…For instance, platelets can sequester tumor RNA through a microvesicle driven mechanism and can be transformed to TEPs. We have worked extensively in order to demonstrate that genetic alterations such as EML4-ALK fusion transcripts can be detected in RNA isolated from platelets (62,63). Furthermore, platelet RNA biomarker signatures can be altered in the presence of cancer and can be used for cancer detection (64,65).…”

Critical issues in the clinical application of liquid biopsy in non-small cell lung cancer

“…In principle, the concordance of genomic alterations between tumor biopsies and CTCs/ctDNA has been demonstrated by several reports, both for EGFR mutations (62)(63)(64) and ALK translocations (50,54,65), leading to the inclusion of CTCs/ ctDNA in clinical trials as prognostic/predictive biomarkers. The results of these studies suggest that monitoring EGFR mutations or EML4-ALK rearrangements in the circulating compartment can reveal therapy resistance also prior to radiological progression evidence, thus guiding the therapeutic decision in the patient clinical course (62,65) (32,68). Notably, these studies also indicate the mandatory need to use methods that are more sensitive in the analysis of tumor biopsies at diagnosis, rather than Sanger sequencing.…”

Liquid Biopsy in Lung Cancer: A Perspective From Members of the Pulmonary Pathology Society

“…20 Notably, platelets can also sequester free nucleic acids and thus may serve as an alternative source of circulating RNA released by tumor cells. 21 Small noncoding RNAs, including microRNAs, are stabilized by microRNA-processing proteins in the circulation. 22 The microRNAs have oncogenic and tumor suppressor gene function and exhibit specific expression profiles in lung cancer, and thus have been proposed as diagnostic and prognostic markers.…”