Can olfactory receptors be 'co-opted' in curbing the growth of bladder cancer tumors?
Researchers led by Drs. Hanns Hatt and Lea Weber, from Ruhr-Universität Bochum in Germany, have made a fascinating find.
They have discovered that there is an olfactory receptor in the human bladder, and it occurs more frequently in cancerous than healthy tissue.
The receptor is also found in greater quantities in the urine of those with bladder cancer.
This, the researchers explain, could make it a viable biomarker when it comes to detecting the presence of this type of cancer.
But the study — the findings of which have been published in the journal Frontiers in Physiology — has also revealed that this receptor is a promising therapeutic target for bladder cancer, which is diagnosed in around 55,000 men and 17,000 women in the United States each year, claim the Centers for Disease Control and Prevention (CDC).
Sandalwood odorants inhibit tumors
"In this study, we describe that one [olfactory receptor], OR10H1, is predominantly expressed in the human urinary bladder with a notably higher expression at [messenger RNA] and protein level in bladder cancer tissues," write Drs. Hatt and Weber.
Similar to other olfactory receptors, OR10H1 is essentially a protein that responds to odorants, or substances that are linked to smells.
In particular, the team noted that OR10H1 binds to odorants that are characteristic of sandalwood oil, such as the compounds Sandranol and Santanol.
Working with bladder cancer cell cultures, the team also observed what happened when the receptor found in tumors was exposed to one of the two sandalwood compounds.
What the scientists found intrigued them: after OR10H1 bound to one of these odorants, the cancer cells became rounder and divided with less frequency. They also tended to move around less.
Also, the olfactory receptor's exposure to sandalwood compounds triggered the activation of some immunity-boosting cellular mechanisms. For one, the interaction led to the release of interleukins, which are a type of protein that help to regulate the body's natural immune response.
The scientists also found that more adenosine triphosphate (ATP) was produced. ATP is a molecule that sustains the transfer of energy within cellular units, and it helps to send "danger" signals to a type of immune cell known as T cells.
This suggests that sandalwood compounds show some promise in curbing the development of bladder cancer tumors, and OR10H1 could be a new therapeutic target.
"In our cell culture studies, we successfully inhibited tumor growth using sandalwood scent," says Dr. Hatt.
Olfactory receptors as cancer biomarkers
That OR10H1 can also be found in larger quantities in urine samples collected from people with a bladder cancer diagnosis suggests that screening for this olfactory receptor's presence in the bladder could be a good way of "sniffing out" cancer.
"Consequently," says study co-author Dr. Burkhard Ubrig, the director of the Urology Clinic at the Augusta Hospital in Bochum, "OR10H1 might perhaps be used as biomarker for the diagnosis of bladder cancer with urine samples."
But looking out for an unusual number of olfactory receptors outside the nose may be a good way of detecting other types of cancer in other parts of the body, too.
Moreover, outside of the nose, where smell receptors are normally found, it only ever appears to show up in tumors — specifically, of lung and pancreatic cancer — albeit in small amounts.
All of this evidence, taken together, suggests that specialists might want to consider olfactory receptors as cancer biomarkers.
"Both studies have confirmed [...]," explains Dr. Hatt, "that olfactory receptors occur outside the nose in both healthy and diseased cells of the body and that particularly high amounts of such receptors can be found in tumor cells."
"In [the] future, they will play an important role not only in the diagnosis of diseases, but, first and foremost, they will provide novel approaches in tumor therapy."
Dr. Hanns Hatt