Head & Neck Cancer: Light Targets Cancer Stem Cells

Head & neck cancer (HNC) refers to a broad group of cancers that typically arise in the moist linings of the mouth, nose and throat.  These tumors can limit the individual’s ability to eat, drink and breathe.  Head & neck tumors that recur or metastasize can be very aggressive and are often described as incurable. Men are at least twice as likely to be diagnosed as women, and both tobacco smoke and alcohol are major risk factors for the disease.

HNC is one of the most common cancers worldwide and a major cause of cancer-related death.  Modern oncology’s poor track record against this group of cancers may be traced to frequent recurrences along with the common phenomenon of resistance to chemotherapy (chemoresistance).  Despite some improvements in the diagnosis and treatment of this disease, long-term survival rates have improved very little over the past few decades.


Targeting Cancer Stem Cells with PDT

In recent years, researchers have become strongly focused on ways to curb chemoresistance and thus enhance the effectiveness of chemotherapy and the prospects for long-term survival.  Cancer biologists have traced the problem of chemoresistance to cancer stems cells.  These self-renewing cells are intimately involved in tumor invasion, metastasis and treatment resistance.  The existence of cancer stem cells might also account for tumor recurrences that take place following the completion of either chemotherapy or radiotherapy, as reported in the 10 January 2014 issue of Anticancer Drugs.

Researchers from Chung Shan Medical University Hospital in Taichung, Taiwan, recently sought to evaluate photodynamic therapy (PDT) as a way to target HNC-derived cancer stem cells.  Previous studies in animals and humans had suggested that PDT might be able to block the growth and metastatic spread of incompletely treated HNC.  The new study was aimed at determining whether PDT could improve chemosensitization through some effect on the HNC-derived cancer stem cells—thus potentially enhancing the chemotherapeutic treatment of HNC.

The Taiwanese researchers were able to demonstrate that PDT had a therapeutic impact on the HNC-derived cancer stem cells, inhibiting various properties of these cells such the stemness signature, migration ability, and chemoresistance.  This represents the first study to demonstrate the critical role of a PDT-based therapy in targeting HNC-derived cancer stem cells and in blocking their tumor-invasive activity.  PDT also led to reduced levels of the multi-drug resistance protein within the cancer stem cells following chemotherapy, indicating a mechanism for reducing chemoresistance, as reported in the 24 January 2014 issue of Plos One.

As noted above, the presence of cancer stem cells has been linked with the low efficacy of anti-cancer treatments against HNC as well as the eventual development of tumor recurrence and metastasis.  The Taiwanese researchers showed that PDT sensitized highly aggressive HNC-derived cancer stem cells to conventional chemotherapy.

Moreover, there was a synergism between PDT and cisplatin (a chemo drug often used for HNC) that further curbed the invasive behavior of the cancer stem cells.  These findings offer insight into the clinical potential of PDT as a potential chemo-supportive therapy against head and neck tumors by targeting the cancer stem cells.

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Yu CH, Yu CC. Photodynamic Therapy with 5-Aminolevulinic acid (ALA) Impairs Tumor Initiating and Chemo-Resistance Property in Head and Neck Cancer-Derived Cancer Stem Cells. PLoS One. 2014 Jan 24;9(1):e87129.

Mertins SD. Cancer stem cells: a systems biology view of their role in prognosis and therapy. Anticancer Drugs. 2014 Jan 10. [Epub ahead of print]


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