Abstract

Background

Majority of patients who undergo neoadjuvant chemotherapy for oesophageal adenocarcinoma (OAC) do not complete treatment. For those who do, there is a low response rate of less than 40%. This is thought to be attributable to chemoresistance mediated by cancer cells and the tumour microenvironment.

Our aims were to demonstrate if cancer-associated fibroblasts (CAFs) support resistance to chemotherapy for OAC, and to determine if phosphodiesterase 5 inhibitors (PDE5i), by reverting the CAF phenotype, could increase sensitivity of oesophageal adenocarcinoma cells to chemotherapy agents.

Method

Concentration of drug required to kill 50% of cells (IC50) for chemotherapy agents used in the MAGIC and CROSS trials were individually assessed using MFD1, an oesophageal adenocarcinoma cell line. Cell viability was assessed using MTS assays. Dose-response experiments and colony forming assays (CFA) were performed using normal media, CAF-conditioned medium (CAF-CM) and medium retrieved after CAFs have been treated with Vardenafil (PDE5i) for 72 hours (V-CM). Expression of αSMA, a marker of CAF differentiation, was assessed by Western blotting to determine CAF de-differentiation after Vardenafil treatment. Colony forming assays were also performed with chemotherapy agents in normal medium and CAF-CM, and colonies were counted.

Results

IC50 of cisplatin was observed to be higher in CAF-CM than in normal media. This was reflected in CFA, whereby more colonies had formed when CAF-CM was used. A similar trend was observed with Carboplatin and 5FU.

When V-CM is used, MFD1 cells appear to be more sensitive to 5FU and carboplatin.

Conclusion

Secreted factors from CAF-CM can promote chemoresistance of MFD1 cells to cisplatin, carboplatin and 5FU.

CM from PDE5i-treated CAFs can increase sensitivity of MFD1 cells to carboplatin and 5FU.

Little response of MFD1 to other chemotherapy agents, despite a reduction in CAF differentiation with PDE5i, leads us to believe that a more complex model encompassing cell-cell contact may be required.