Detection of Collateral Tissue Damage in Metastatic and Local Cancer by cfDNA Methylation - הכינוס השנתי הדיגיטלי של החברה הישראלית לפדיאטריה קלינית

Asael Lubotzky ^1,2 Daniel Neiman ¹ Hai Zemmour ¹ Sheina Piyanzin ¹ Bracha-Lea Ochana ¹ Albert Grinshpun ³ Aviad Zick ³ Chen Makranz ³ Raul Mostoslavsky ⁴ Brian Wolpin ⁵ Benjamin Glaser ³ Ruth Shemer ¹ Yuval Dor ¹

¹Department of Developmental Biology and Cancer Research, Institute for Medical Research Israel-Canada, the Hebrew University Medical School, Israel
²Department of Pediatrics, Shaare Zedek Medical Center
³Sharett Institute of Oncology, Hebrew University-Hadassah Medical School, Israel
⁴The Massachusetts General Hospital Cancer Center, Harvard Medical School
⁵Department of Medical Oncology, Dana-Farber Cancer Institute and Harvard Medical School

It is well established that blood contains cell-free DNA fragments derived from dying cells. Most of these DNA fragments are the size of a nucleosome, i.e. 165 bp. cfDNA is short-lived in plasma (half-life of 15-120min), and therefore originates from events that occurred close to the time of sampling.

Analysis of cfDNA is already being used for assessment of chromosomal aberrations in fetuses, for monitoring tumor dynamics (by detecting somatic mutations in plasma) and for early detection of graft rejection. However, existing methods rely on genetic differences between the host and the tissue of interest (fetus, tumor or graft). Therefore, they are blind to events involving cells with normal genome so that cell death cannot be identified in tissues with no sequence differences. We developed a method of detecting tissue-specific cell death in humans based on tissue-specific methylation patterns in cfDNA.

Cancer inflicts damage to surrounding normal tissues, potentially culminating in fatal organ failure. Here we demonstrate the detection of cell death in organs affected by local or metastatic cancer growth, via tissue-specific methylation patterns in circulating cell-free DNA (cfDNA). We identified higher levels of neuron-, oligodendrocyte- and astrocyte-derived cfDNA in the plasma of patients with brain metastasis (n=29), compared with cancer patients without brain metastasis (n=113). We also detected elevated levels of hepatocyte-derived cfDNA in the plasma of patients with different primary tumors that have liver metastases (n=63), compared with cancer patients without liver metastases (n=140). Finally, patients with localized pancreatic cancer show elevated hepatocyte cfDNA, demonstrating collateral tissue damage inflicted by the primary tumor. Cell type-specific cfDNA methylation markers allow the identification of collateral tissue damage in cancer, potentially revealing the presence of metastases in specific locations and even assisting early cancer detection.