Implications of cancer stem cells in radiotherapy current understanding and future perspectives

Many theories were put forward about origin of cancer and immense research was carried out to understand the mechanisms involved in the origin and progression of the disease. The gain in scientific knowledge about cancer biology and technical advancement in treatment modalities resulted in improvement of clinical outcome in cancer therapy. However, recurrence and metastasis after therapy poses a major concern to clinicians. Resistant nature against therapeutic modalities and metastatic potential of cancer stem cells (CSCs), which even though form a fraction of tumor mass, result in failure of existing modalities of cancer treatment. The current article reviews the historical background of CSCs, involvement of various signaling pathways in the mechanism(s) of radioresistance and potential targets to be exploited in radiotherapy.