Role of tumor microenvironment in cancer stem cell chemoresistance and recurrence.

Chemoresistance to the anticancer therapy is the main challenge for the recurrence of cancer and it is responsible for treatment failure and unfavorable clinical outcome. Understanding the mechanisms of chemoresistance in cancer would help to predict disease progression, develop new therapies and personalize systemic therapy. In the last few decades, cancer stem cells (CSC) have proven to play a key role in tumor initiation and may also act as a key factor for chemoresistance and recurrence of the disease following chemotherapy. Resistance to anticancer therapy in patients has been attributed towards a number of factors controlling the stemness character of the cancer stem cells which leads to therapeutic resistance. Accumulating evidences show that the bone marrow (BM) niche is critical to the maintenance and retention of cancer stem cells. Undeniably, stromal cells within the BM niche provide a sanctuary where different signaling pathways and cell-cell interaction gives a protective nature to the diseased condition, and thereby evade chemotherapy-induced death. In this review we have tried to highlight the factors which have important role in chemoresistance and are associated with bone marrow microenvironment. We have also discussed about the recent progresses regarding CSC-targeted therapies to throw light toward developing more effective therapeutic strategies to eradicate cancer in the patients concerned.