Head and neck cancer stem cells were discovered in 2007 by scientists at the U-M Comprehensive Cancer Center and Stanford University
About 40,000 Americans are diagnosed with head and neck cancer every year. These malignant tumors develop in mucous membranes that line the mouth, throat and sinuses. More than 90% of head and neck tumors are a type of cancer called squamous cell carcinoma.
Survival rates for head and neck cancer are about 50% and have not changed much in the last 50 years. This means that about half of people diagnosed with this disease will die from it within five years.
Are all head and neck cancers the same?
There are two main types of head and neck cancer. The first type includes cancers of the lips, mouth, throat, voice box, nose or sinuses. These cancers most often develop in older men who smoke or chew tobacco. Scientists believe this type of cancer is caused by genetic mutations triggered by cancer-causing agents in tobacco.
The second type of head and neck cancer affects young adults and is not related to tobacco use. These cancers usually develop at the back of the throat or in the tonsils. They are caused by the human papilloma virus, which also causes cervical cancer.
One of the unique things about head and neck cancer is that, although these tumors all look the same under a microscope, they behave differently in the body and respond differently to treatment, depending on where the tumor originally develops. Scientists don't understand why this happens.
Laryngeal cancer - cancer of the voice box - is a good example. If it develops in the vocal cords and if it is treated in the early stages, it has an 80%t to 90% survival rate. If the same type of cancer develops in the mouth, it is very likely to spread to lymph nodes and the patient is much less likely to survive.
What makes head and neck cancer so deadly?
1. Resistant to treatment
Tumors are often resistant to chemotherapy and radiation therapy, especially tumors in the mouth.
Head and neck cancer tends to spread or metastasize easily -- most often to lymph nodes in the neck, but also to other places throughout the body.
Many people with head and neck cancer continue to smoke or use chewing tobacco. This increases their risk of developing new cancers, even if the original tumor is treated successfully.
How were the cancer stem cells discovered?
In 2007, a team of scientists from the U-M Comprehensive Cancer Center and Stanford University led by Mark Prince analyzed cells from head and neck tumors removed from seven patients. They looked for cell surface markers previously found in breast cancer stem cells. Another team of scientists at the U-M Cancer Center discovered in 2004 that breast cancer stem cells had three specific surface markers. When U-M and Stanford scientists looked for the CD44 marker, they found it on a small number of cells in head and neck cancer tumors, also.
Then the scientists injected cells from these tumors into mice with deficient immune systems. Mice injected with CD44-positive tumor cells developed tumors that were identical to the patient's original tumor, while mice given CD44-negative cells did not form tumors. This indicated that cells with the CD44 marker included stem cells for head and neck cancer. Scientists are looking for other markers to help them find the pure population of cancer stem cells within the CD44-positive group.
Were the stem cells in a specific location in these tumors?
Cancer stem cells were located in the basal, or bottom, layer of skin or mucosal cells lining the mouth and throat. This is important, because cells divide and produce new replacement cells in this cell layer. Because normal stem cells are found in the basal layer, it's significant that cancer stem cells were found there, also. It suggests that cancer stem cells probably originate from normal mucosal stem cells in the basal layer and then gain mutations, which makes them behave abnormally.
In 2007, a team of scientists from the U-M Comprehensive Cancer Center and Stanford University identified cancer stem cells in tumors removed from patients with head and neck cancer. Scientists believe these stem cells are the "root cause" of cancer - the cells that drive its growth and are responsible for metastasis and resistance to therapy.
Because they were discovered so recently, less is known about head and neck cancer stem cells than breast cancer stem cells. Cancer Center researchers are studying head and neck cancer stem cells to learn how they work and how to kill them without harming normal cells.
What are your goals for research on head and neck cancer stem cells?
At the U-M Comprehensive Cancer Center, the ultimate goal is to understand how cancer stem cells arise and prevent that process from happening. This would be the cure for cancer, but achieving that goal is still a long way off. At least now scientists are looking at the right cells -- the critical population. If researchers can find a way to kill them, the rest of the cancer cells will die off and the cancer will fade away or, at the least, not grow.
Continue reading about current and possible future methods of treating head and neck cancer: Treatment and Stem Cells.