A broad group of diseases involving unregulated cell growth is known as cancer or as malignant neoplasia. In cancer, cells divide and grow uncontrollably, causing the cells to form lumps or tumors. The cancer may also spread to more distant parts of the body through the lymphatic system or bloodstream. Not all tumors are cancerous; benign tumors do not invade neighboring tissues and do not spread throughout the body.
Metastatic cancer is a prevalent disease and a major cause of cancer-related deaths amongst cancer patients. At present, most non-operable advanced metastatic cancers are considered incurable and search for alternative therapeutic options is currently at the forefront of drug discovery research.
Metastasis is a regulated process involving a rare genetically programmed cancer cell variant with intrinsic invasive capacity. Studies have identified such rare metastatic cell populations to be enriched in specific biomarkers, including cell surface receptors that are often seen in stem cell/progenitor cells. These cell variants are interchangeably referred to as tumor-initiating cells with stem cell-like properties, cancer stem-like cells or cancer stem cells (CSC). In many instances, these tumor-initiating cells with stem cell-like properties have been correlated with cancer heterogeneity, poor prognosis and also found as the culprit to building resistance to many current chemo- and radiation therapies, which ultimately fail since they are not able to eliminate these cells.
For the treatment of cancer, chemotherapeutic, immunotherapeutic or immunomodulatory and antiangiogenic agents have been reported. Agents can be used as monotherapy (treatment with one agent) or as combination therapy (simultaneous, separate or sequential treatment with another agent). The treatments may also be combined with radiotherapy.