Organoids take on ESCC’s toughest tumours

Oesophageal cancer remains one of the world’s deadliest cancers, ranking 7th in incidence and 6th in cancer-related deaths globally. In East Asia and Japan, over 90 percent of these cases are oesophageal squamous cell carcinoma (ESCC). One reason for poor treatment outcomes is the high recurrence of ESCC, with only 55 percent to 63.6 percent of patients remaining cancer-free five years after treatment. 

A research team led by Professor Toshiaki Ohteki and former Associate Professor Taku Sato at the Institute of Science Tokyo, developed a patient-derived organoid library. These organoids, which are 3D miniatures of patient-derived tumours , were used to investigate mechanisms of drug resistance and to screen potential therapeutic candidates. 

The findings 

The findings, published in Volume 8 of Communications Biology, resulted from a collaboration between researchers at Science Tokyo’s Departments of Gastrointestinal Surgery and Comprehensive Pathology, Keio University, and the Tokyo Metropolitan Cancer and Infectious Diseases Center Komagome Hospital. 

“Unlike artificial models that are developed by repeatedly exposing cancer cell lines to chemotherapy over time, the chemo-resistant ESCC organoids more accurately reflect the traits of the original patient tumours,” explains Professor Ohteki. 

 “Because we have established several chemo-resistant ESCC organoid lines with different oncogenic mutations, they offer a valuable tool for identifying effective drugs tailored to various forms of chemotherapy resistance.” 

Developing organoids from patient tumour samples 

The research team grew organoids from tumour samples of 24 ESCC patients with diverse backgrounds and treatment histories. These lab-grown mini-tumours closely resembled the patient’s original tumours, displaying nuclear p53 protein buildup – a common marker of TP53. Each organoid also carried patient-specific mutations and exhibited gene activity associated with rapid cell growth and DNA replication – hallmarks of cancer cells. 

When transplanted into immunodeficient mice, the organoids formed tumours that retained key features of the original cancers. This included nuclear p53 accumulation and stratified, keratinised tissue structures. 

Testing chemotherapy resistance 

Using the ESCC organoid library, the team tested how each organoid line responded to cisplatin and 5-fluorouracil (CF) – a standard chemotherapy regimen for ESCC. While 71 percent of the organoids (17 lines) were sensitive to treatment, 29 percent (7 lines) showed resistance. Further analysis revealed increased activity in the nuclear factor erythroid 2-related factor 2 (NRF2) pathway in the resistant organoids.  

While NRF2 normally protects cells from oxidative stress, mutations that over activate this pathway can enhance a tumour’s antioxidant defences, increasing resistance to chemotherapy. In all the chemo-resistant organoids, NRF2 target genes, including ALDH3A1, SPP1, and TXNRD1, were overexpressed. This suggests their potential as biomarkers for predicting chemotherapy resistance. 

“About 28 percent of patients with ESCC do not respond well to neoadjuvant chemotherapy. Therefore, identifying biomarkers that can predict which tumours are resistant to this treatment is crucial for ensuring patients get the most appropriate and effective care early on,” says Professor Sato.  

Evaluating new drug candidates 

The organoid model also proved valuable for evaluating new drug candidates. Fedratinib demonstrated greater efficacy than standard CF chemotherapy in inhibiting the growth of chemo-resistant ESCC organoids.  

Interestingly, fedratinib’s effectiveness was not dependent on the NRF2 pathway. Further research suggested that its anti-tumour effect was linked to inhibition of BRD4, a protein involved in cancer cell growth. 

These findings highlight the organoid model’s potential to guide new therapies for chemotherapy-resistant tumours.