• Squamous cell carcinoma is the second most common skin cancer in the United States.
• In a recent study, researchers exposed mice to UVB radiation and treated them with drugs that target dopamine D2 receptors.
• The study showed a reduction of squamous cell carcinomas in the treated mice.
• While more research is necessary to confirm the findings, this is the first time a study has shown that activating dopamine receptors may help prevent squamous cell carcinoma.

According to the Skin Cancer Foundation, squamous cell carcinoma is the second most common form of skin cancer in the U.S., behind basal cell carcinoma.

The organization notes that approximately 1.8 million people get a diagnosis of squamous cell carcinoma in the U.S. each year.

Taking steps to prevent skin cancer, such as wearing sunscreen and avoiding the sun during the hottest part of the day, is of utmost importance. However, new research indicates that a drug may also help prevent squamous cell carcinoma.

A group of researchers at The Ohio State University Comprehensive Cancer Center (OSUCCC) in Columbus studied a drug called quinpirole, which doctors typically use to treat people with Parkinson’s disease.

Squamous cell carcinoma

There are multiple types of skin cancer, including carcinomas and melanomas. Carcinoma cancers are less able than melanomas to spread quickly to other areas of the body, so they typically have a higher survival rate.

Carcinoma cancers occur in the epithelial tissue, which is present throughout the body. In addition to being part of the skin, this tissue also makes up the covering and lining of organs in the body, such as the stomach.

Squamous cells are part of what makes up the epidermis, which is the outermost layer of skin.

According to the Centers for Disease Control and Prevention (CDC), squamous cell carcinoma is most often due to “overexposure to [UV] light.” In other words, spending too much time on tanning beds or unprotected in the sun can increase the risk of developing skin cancer.

“Cancer control experts have been stressing the importance of reducing exposure to the sun and practicing sun-safe habits for many years, but scientific data show us that cumulative damage of UV rays ultimately leads to skin cancer for many people,” says Dr. Sujit Basu, Ph.D., the senior author of the study. Dr. Basu is a researcher at OSUCCC and a professor of pathology at The Ohio State University College of Medicine.

“Finding better ways to prevent these cancers from developing is critical to reduce the global burden of this disease,” says Dr. Basu.

Skin cancer study 

The team’s study, which appears in Cancer Prevention Research, indicates that a drug that activates dopamine D2 receptors may aid in the prevention of squamous cell carcinoma.

Dopamine is a neurotransmitter that naturally occurs in the body. Some conditions, such as Parkinson’s, involve reduced dopamine levels in the body. People with these conditions may receive treatment in the form of a D2 receptor agonist, such as quinpirole.

The study exposed three groups of mice to UVB radiation, which is responsible for skin cancers.

One group of mice served as a control group, while the second group of mice received quinpirole treatment. The researchers pretreated the third group of mice with a D2 receptor antagonist drug called eticlopride. This drug blocks D2 receptors, preventing other compounds from binding to and activating them. The researchers later gave this third group of mice quinpirole.

The mice who received quinpirole alone showed a reduction in tumor size. However, mice that received eticlopride first did not experience the benefits.

As the authors explain, this supports the idea that the benefits of quinpirole occurred because of its action at dopamine D2 receptors.

The authors note that “[t]he number of cutaneous tumors and the tumor burden significantly decreased” in the mice that they treated with quinpirole.

Additionally, these mice had reduced rates of papillomas. Papillomas are benign skin growths, but they are associated with higher cancer risk.

The mice in the control group displayed:

• hyperplasia: 13.3%
• grade 1 papilloma: 26.5%
• grade 2 papilloma: 23.3%
• grade 3 papilloma: 20.0%
• squamous cell carcinoma: 16.6%

In contrast, in the quinpirole treatment group, these percentages were markedly lower:

• hyperplasia: 6.6%
• grade 1 papilloma: 3.3%
• grade 2 papilloma: 3.3%
• grade 3 papilloma: 0%
• squamous cell carcinoma: 0%

“These results demonstrate that treatment with a selective [dopamine] D2 receptor agonist can considerably inhibit development and progression of UVB-induced premalignant squamous cell skin lesions,” write the authors.

Dr. Basu believes that the findings support the possibility of preventing squamous cell carcinoma one day.

“Our study suggests that a commonly used drug that activates specific dopamine receptors could help reduce squamous cell skin cancer recurrence and possibly even prevent the disease entirely,” says Dr. Basu.

“This is especially exciting because this is a drug that is already readily used in clinical settings and is relatively inexpensive. We are excited to continue momentum in this area of research,” Dr. Basu concludes.

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