Targeting of cancer stem/progenitor cells plus stem cell-based therapies: the ultimate hope for treating and curing aggressive and recurrent cancers.

The rapid progression from aggressive primary cancers into locally advanced and invasive and/or metastatic diseases remains a big obstacle for an early diagnosis and curative therapeutic intervention for cancer patients. The late-stage leukemias and disseminated and metastatic sarcomas, melanomas, brain tumors and epithelial cancers are the devastating diseases associated with a high rate of recurrence after treatment with the conventional clinical therapies including surgery, ionizing radiation, hormonal therapy and systemic chemotherapy, which generally lead to the death of patients. Therefore, the establishment of the molecular events underlying cancer initiation and progression into locally invasive and metastatic diseases is of major interest in basic cancer research as well as for the development of new effective clinical therapeutic options against the recurrent and lethal cancers. Recent advances have led to the identification of specific oncogenic products that are implicated in the malignant transformation of adult stem/progenitor cells into leukemic or tumorigenic and migrating cancer stem/progenitor cells during cancer progression. Of therapeutic interest, the molecular targeting of deregulated signaling elements in cancer stem/progenitor cells and their local microenvironment represents a new potential strategy for the development of more effective clinical treatments against aggressive cancers. Particularly, the combined use of chemotherapeutic drugs to eradicate cancer-initiating cells with hematopoietic stem cell or genetically-modified stem cell transplant is emerging as potential cancer treatments that hold great promise in the area of clinical cancer research. These targeting and stem cell-based therapies may offer the ultimate hope for treating and even curing the patients diagnosed with locally advanced cancers at high risk of recurrence, metastatic and/or relapsed cancers in the clinics.