Table 2. Key under-explored areas of research into the effects exerted by stromal cells in the tumour microenvironment.

Key under-explored areas of research into the effects exerted by MSCs in the tumour microenvironment (TME) The identification of definitive markers of cancer-associated fibroblasts Precise mechanisms by which MSCs are recruited to the TME The exact ratio of MSCs present in the TME at various stages of cancer progression The factors responsible for MSC-mediated M2 polarisation of macrophages The factors that allow MSCs supress innate immune functions The mechanisms by which MSCs suppress T cell proliferation and effector functions The ability of MSCs to behave as immune cells and the consequences of this for tumour growth and progression The role played by both tumour- and MSC-derived exosomes in tumour progression The influence of MSCs on chemo- redio- and immuno-therapy resistance in colon tumours