Northwestern Medicine develops liquid biopsy blood test for small cell lung cancer

Researchers from Northwestern Medicine and Hebrew University of Jerusalem have demonstrated a cell-free chromatin immunoprecipitation sequencing (cfChIP-seq) blood test that detects small cell lung cancer (SCLC) burden and molecular subtypes. Published in the Journal of Clinical Investigation, the technique analyzes gene expression from active chromatin marks in 1 milliliter of blood across 441 plasma samples, offering a noninvasive alternative to tissue biopsies for tracking SCLC progression and treatment resistance.

Development of the cfChIP-seq biopsy technique

• ▪Northwestern Medicine scientists and collaborators from Hebrew University of Jerusalem demonstrated a cell-free chromatin immunoprecipitation sequencing (cfChIP-seq) liquid biopsy technique for small cell lung cancer in a study published in the Journal of Clinical Investigation.
• ▪The cfChIP-seq liquid biopsy technique, developed by Hebrew University of Jerusalem researcher Nir Friedman and tested with Northwestern Medicine, identifies key gene-expression features of small cell lung cancer using 1 milliliter of blood.

Validation of the cfChIP-seq technique

• ▪Researchers validated the cfChIP-seq liquid biopsy technique by analyzing 441 plasma samples from healthy controls, small cell lung cancer patients, and other cancers against matched tumor tissue samples.
• ▪In a study published in the Journal of Clinical Investigation, blood-based measurements from the cfChIP-seq technique correlated strongly with small cell lung cancer tumor burden shown on imaging.

How cfChIP-seq analyzes gene expression

• ▪Unlike conventional liquid biopsies that examine tumor DNA mutations, cfChIP-seq analyzes DNA fragments and active chromatin marks shed into the bloodstream to determine which genes are active in tumor cells.
• ▪Senior study author Anish Thomas noted that while most existing liquid biopsy technologies detect DNA mutations, small cell lung cancer biology is largely driven by differences in gene expression.

Clinical applications and future implementation

• ▪Blood-based molecular profiling using cfChIP-seq may allow clinicians to monitor small cell lung cancer progression, treatment response, and emerging therapy resistance without invasive repeat biopsies.
• ▪Researchers stated that larger prospective studies repeatedly sampling patients during treatment are required before cfChIP-seq can be incorporated into routine clinical care for small cell lung cancer.
• ▪The cfChIP-seq liquid biopsy technique identified molecular subtypes and gene-expression features of small cell lung cancer without requiring repeated tissue biopsies.

Characteristics of small cell lung cancer

• ▪Small cell lung cancer accounts for roughly 15% of lung cancer cases according to estimates from the Centers for Disease Control and Prevention.
• ▪Small cell lung cancer is marked by rapid growth, early spread, and poor survival outcomes, making repeated tissue biopsies for molecular testing challenging.

Advantages of liquid biopsies

• ▪Liquid biopsy enables frequent cancer monitoring and can be administered in local clinics or community health centers without requiring specialized hospital surgical facilities.
• ▪Liquid biopsy detects genetic traces released by tumor cells into the bloodstream through a simple blood test, offering a minimally invasive alternative to surgical tissue biopsies.

Challenges in analyzing circulating DNA

• ▪Detecting circulating tumor DNA requires distinguishing faint cancer genetic signals from normal background DNA and analyzing billions of DNA fragments per patient using artificial intelligence and bioinformatics.
• ▪Circulating DNA in blood samples is often fragmented and degraded, requiring purification and experimental bias correction before sequencing and computational analysis.

Canadian Cancer statistics

• ▪According to the Canadian Cancer Society, lung, breast, prostate, and colorectal cancers are the most commonly diagnosed cancers in Canada.
• ▪According to the Canadian Cancer Society, cancer is the leading cause of death in Canada, where two in five Canadians will develop cancer during their lifetime and nearly 700 people are diagnosed daily.