Epigenetic mechanisms governing interactions between cancer and microenvironmental cells

Thesis

It is now well-established in the field of oncology that the tumour microenvironment (TME) plays a vital role in cancer pathogenesis. However, whilst the immune TME has been an area of intense study, substantially less work has been carried out other TME cell types, particularly those which are tissue specific. In this study, we implemented an intercellular fate-mapping system to examine interactions between cancer cells and TME cells, with a focus on melanoma-keratinocyte crosstalk. We engineered melanoma cells with a form of Cre recombinase enriched in extracellular vesicles (EVs), and keratinocytes with a CMV-loxP-dsRed-loxP-eGFP construct. Thus, transfer of Cre recombinase containing EVs from melanoma cells to recipient keratinocytes induced a permanent colour change within keratinocytes which we could track using imaging methods. Use of this system in previous work revealed stark epigenetic differences arising between non-interacting and interacting keratinocytes, which we chose to probe further here using a high throughput epigenetic compound screen. This screen identified two compounds, CAY10603 and TC-E 5003, which were able to significantly enhance melanoma-keratinocyte interactions in co-culture. Later work then demonstrated that this increased crosstalk was likely to arise through the effects of both drugs on recipient keratinocytes as opposed to donor melanoma populations. RNA sequencing of keratinocytes treated with these compounds then revealed that both evoked a stark repression of interferon and innate immune related pathways. Subsequent knockdown of ELF3, a protein with known roles in immune regulation, in recipient keratinocytes revealed that this perturbation alone was able to significantly increase their interaction frequency with donor melanoma cells. Thus, we highlight here a previously undescribed role of innate immune signalling in governing cancer-TME interactions, knowledge of which may be useful in the development of future TME-targeting therapies.

Authors: Pook, H

• DOI: 10.5287/ora-vjvzxammg
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: melanoma; extracellular vesicle; keratinocyte; ELF3; TME; EV; tumour microenvironment
• Subjects: Melanoma; Oncology