30P - Prostaglandin signaling in tumour stroma interaction in colorectal cancer and its impact on the secretome and functional relevance

Background

One of the risk factors to develop colorectal cancer (CRC), which is one of the deadliest types of cancer, is inflammation. Among the factors involved in the inflammatory response, prostaglandins (PGs) seem to play an important role. The tumor microenvironment (TME) influences the development of the tumor and within the TME, cancer associated fibroblasts (CAFs) represent the major compartment. Despite the importance of the TME, there is limited evidence on the secretome-dependent communication of CRC cells with CAFs and myeloid cells with respect to PG signaling. In this project we mainly focus on PGE2 and PGF2α, that we have previously found are secreted by CAFs.

Methods

By using in vitro 3D cocultures secreted molecules induced by increased or decreased PGE2 and PGF2α expression were identified. The levels of both PGs were measured by ELISA, whereas the expression of the production enzymes was analyzed by Western Blot. Phenotypic analysis and functional assays were carried out using siRNA or specific inhibitors to analyze the effect on angiogenesis and contractility of CAFs, their proliferation, motility, and apoptosis levels. Finally, preliminary in vivo experiments were performed and, additionally, paraffin tissue sections from patient-derived xenografts (PDX) models were stained to prove the stroma expression of the PGs specific synthases.

Results

We demonstrate that a combination of proinflammatory cytokines can increase the expression of COX-2 and mPGES-1 while IL-4 decreases it. Knocking down the specific synthases of PGE2 and PGF2α in the CAFs also leads to a decrease in their proliferation, contractiliy, motility and angiogenesis capacity, but did not induce apoptosis. In vivo, knocking down of the PGs specific synthases seems to lead to a worse survival capacity, and some of these enzymes seem to be only expressed in the stromal cells of PDX models.

Conclusions

More information about the link between cancer and its TME would help us to achieve a higher degree of accuracy in the development of potential future therapies. Here we have proved that the action of PGs, especially PGF2α and PGE2, is involved in tumor development in 2D and 3D suggesting a possible therapeutic target.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Marie Skłodowska-Curie Actions - PhD Research Fellowship. European Commission (Horizon 2020).

Disclosure

All authors have declared no conflicts of interest.