Cancer stem cells have been identified in brain, breast, colon, ovarian, pancreatic, and prostate tumors, as well as in melanoma, multiple myeloma, nonmelanoma skin cancer, and leukemia.
Cancer stem cell research is ongoing, and new studies are emerging frequently.
What Are Cancer Stem Cells?
The stem cell theory of cancer hypothesizes that cancer stem cells are thought to drive tumor initiation and may be responsible for therapeutic resistance and cancer recurrence.
There are two types of stem cells: embryonic and adult stem cells. Embryonic stem cells come from unused embryos and are created from an in vitro fertilization process. They are pluripotent, meaning they can turn into more than one cell type. Within adult stem cells, there are two different types: one type comes from fully developed tissues such as the brain, skin, and bone marrow, and the other is induced pluripotent stem cells, which have been changed in the lab to be more like embryonic stem cells.
Like many areas of biomedical research, cancer stem cells are an evolving field of study. Multiple studies have indicated that insufficient evidence exists to confirm the existence of cancer stem cells. A review of 1,000 Web of Science publications revealed that only 49% supported the cancer stem cell hypothesis.
Cell surface markers can be used to identify cancer stem cells, as has been done in research that supports the hypothesis that these stem cells do not respond to traditional therapies such as chemotherapy. This research also supports the idea that cancer stem cells are the source of cancer metastasis.
Like all stem cells, cancer cells must have the following characteristics:
Self-renewal: When stem cells divide into more stem cells, this process is referred to as cell renewal. Cell differentiation: Cell differentiation is when a cell changes from a less differentiated to a more differentiated cell type.
Role in Cancer Growth
Cancer stem cells use specific signaling pathways. It is hypothesized that cancer stem cells can also act as a reservoir of cancer cells, which may cause a relapse after surgery, radiation, or chemotherapy has eliminated all observable signs of cancer. Targeting these cells would thus highly improve the chances of a patient’s remission if cancer stem cells are the origin of the tumor.
Resistance to Therapy
Cancer stem cells have the capacity to change into more specialized cell types, so they can potentially lead to tumor cell heterogeneity. Due to this quality, they are cited as a major factor of chemoresistance. Their highly resistant nature can lead to tumors metastasizing and tumor regrowth. As such, the developing research on cancer stem cells could dramatically change the prognosis of multiple cancer types.
Also, many new anticancer therapies are evaluated based on their ability to shrink tumors, but if the therapies are not killing the cancer stem cells, the tumor will soon grow back, often with resistance to the previously used therapy.
Importance of Cancer Stem Cell Research
Cancer stem cell research is critical because it addresses the potential root cause of cancer proliferation and can lead to the development of more effective and safer treatments. Treatments targeting cancer stem cells will likely have fewer side effects compared with existing options because they will leave other kinds of cells untouched.
Understanding these cells can also help modify current treatments for maximum effect. Research has shown that cancer stem cells are resistant to the ionizing radiation used to treat cancer. Understanding this resistance may in the future help researchers find compounds that undermine this process and make cancer stem cells vulnerable to radiation damage.
A Word From Verywell
Cancer stem cell research offers promising hope for the continually evolving field of cancer therapeutics, but more research needs to be done to confirm the stem cell theory of cancer. Cancer stem cell research has the potential to generate better treatments for cancer with fewer side effects, as well as to improve the efficacy of current treatment options. If the theory is proven, therapies targeting cancer stem cells may even be able to lower the rate of cancer recurrence. While its existence is still up for debate, it represents an exciting opportunity to advance cancer care and improve cancer survival.
