Cancer-associated fibroblasts: Secretions, interactions, and therapy.

Tumor microenvironment (TME) could impose a great challenge for cancer targeted therapies. Immunosuppression within the TME creates a barrier between cancer cells and therapeutic approaches. A number of cells are hosted within this milieu, among them cancer-associated fibroblasts (CAFs) are the most abundant cell populations playing major roles in mediating an immunosuppressive TME. CAFs have cross-talks with almost all cells within the TME for reprogramming them into being tumorigenic. This reprogramming reduces the pre-existing tumor immunity and dampens the efficacy of chemotherapeutic approaches. CAFs would do this through releasing a myriad of factors to the TME making it an appropriate nest for tumor growth. The cells degrade and deposit extracellular matrix components, both of which are tumorigenic. Therefore, disruption of cross-talks between CAFs with other cells within the TME would be a promising approach in cancer targeted therapies. This approach is applicable through dampening dominant signals mediated by CAFs. Another interesting approach would be reprogramming of CAFs toward their normal counterpart. This would need identification of different subtypes for these cells and their functions. More knowledge is also required about selective markers for each CAF subtype.