Stem cells & cancer stem cells
A normal stem cell is defined as a cell that can renew itself indefinitely, while producing cell progeny that mature into more specialized, organ‑specific cell. The division is asymmetric. One of the two daughter cells retains the stem cell characteristics while the other is destined for the limited number of future divisions and will produce the more organ‑specific cells. On the other hand a cancer stem cell may derive from mutations in normal stem cells. Normal stem cells have many of the characteristics of cancer stem cells. They share the ability for self‑renewing cell division, and resistance to programmed cell death. Several of the molecular signaling pathways associated with normal stem cell development, such as Wnt and Notch, are also active in cancer development.
The presence of stem cells within tumors may explain the recurrence of tumor many years after the initial cancer has been removed of treated. One possible explanation for this is the recent identification of stem cells within breast cancers. Stem cells were isolated from primary and metastatic breast cancers from breast cancer patients. Like normal stem cells within normal tissue, cancer stem cells have high self-renewal capacity and proliferate infrequently. The majority of current therapies, including chemotherapy, are designed to kill cells that proliferate quickly which make up the main core of the tumor. Therefore, cancer stem cells are unlikely to be targeted by such drugs which principally affect only the high proliferative cells. Consequently, these cancer stem cells may survive chemotherapy and radiotherapy and proliferate again to produce new tumors several years later. Under this situation, current chemotherapeutic drugs and radiotherapy may not be getting us anywhere, because we have been targeting the wrong cancer cell population. We are therefore, dedicated to developing novel therapeutic modalities which target the cancer stem cell population.
Stem cell research opens a new avenue for novel therapeutic strategies for cancer treatment which promise remarkable clinical implications.