Detect cancer earlier
Even with advances in treatment methods, prognosis and cancer outcome still greatly depend on the timing of diagnosis. It could mean the difference between straightforward treatment and invasive surgery, remission and metastasis, and survival and death. Hence, early-stage identification of cancer is a high priority in research, with great efforts directed towards the development of tools for the detection of cancer biomarkers. The world's first iridium(III)-based probes for imaging dopamine receptors in living cells is a successful outcome that has arisen from the commitment of a team led by Dr Edmond Ma, Associate Professor of the Department of Chemistry, to this research area. This discovery has enhanced the understanding of dopamine receptors in carcinogenesis, and the findings can be potentially developed into a novel early cancer detection technology.
Improving odds of survival
Dopamine receptors bind to and transmit signals carried by dopamine, a chemical messenger in the brain with important roles in motivation, cognition and motor control. These receptors have long been implicated in neurodegenerative diseases, such as Parkinson's disease, but a growing body of literature has linked them also with several types of cancer, such as lung, breast and colon cancers.
According to data from the American Cancer Society, patients with early stage non-small cell lung cancer (NSCLC), the most common subtype of lung cancer, have a five-year survival rate of about 92%. This drops significantly to less than 40% when the cancer has progressed to an advanced stage. "Early detection is crucial, especially for hard-to-treat cancers like lung cancer, which is associated with dopamine receptor expression."
The metal-based probes developed by the team are able to selectively bind to dopamine receptors on lung cancer cells to produce a biological response. By "lighting up" the cells, the cancer becomes visible to the naked eye. Research shows that the agonist labelling iridium(III) complex has low cytotoxicity and possesses long luminescence lifetime, even in the presence of an endogenous fluorescence background signal. Therefore, they hold great promise as an alternative tool for real-time monitoring and tracking of dopamine receptors in living cells in a non-invasive fashion, superior to traditional detection methods such as the enzyme-linked immunosorbent assay (ELISA) which suffers from high cost, incompatibility with living systems, and unsuitability for real-time study. Importantly, the metal-based probes avoid the problems of poor photostability and photobleaching that limit conventional fluorescent imaging dyes. Moreover, results demonstrated that the imaging colour intensity correlates with the expression levels of dopamine receptors on cancer cells. Since overexpression tends to increase with the stage of the disease, these probes could be used for studying the role of dopamine receptors in cancer pathogenesis, migration and metastasis.
The research project "Cell imaging of dopamine receptor using agonist labeling iridium(III) complex" was published in the inside front cover of Chemical Science, the flagship journal of the Royal Society of Chemistry. It was led by Dr Edmond Ma together with Professor Leung Chung-hang of the Institute of Chinese Medical Sciences, University of Macau. Other collaborators of the project included researchers from the School of Chinese Medicine of HKBU, the City University of Hong Kong, University of Florida, USA, and Hunan University, China.
Click to learn more: Department of Chemistry