Monitoring the dynamics of hemeoxygenase-1 activation in head and neck cancer cells in real-time using plasmonically enhanced Raman spectroscopy.

We report for the first time the usage of plasmonically enhanced Raman spectroscopy (PERS) to directly monitor the dynamics of pharmacologically generated hemeoxygenase-1 (HO-1) by evaluating the kinetics of formation of carbon monoxide (CO), one of the metabolites of HO-1 activation, in live cells during cisplatin treatment. Being an endogenous signaling molecule, CO plays an important role in cancer regression. Many aspects of HO-1's and CO's functions in biology are still unclear largely due to the lack of technological tools for the real-time monitoring of their dynamics in live cells and tissues. In this study, we found that, together with nuclear region-targeted gold nanocubes (AuNCs), cisplatin treatment can dramatically trigger the activation of HO-1 and thereby the rate and production of CO in mammalian cells in a dose-dependent manner. Though quantitative molecular data revealed that a lower concentration of cisplatin up-regulates HO-1 expression in cancer cells, PERS data suggest that it poorly facilitates the activation of HO-1 and thereby the production of CO. However, at a higher dose, cisplatin along with AuNCs could significantly enhance the activation of HO-1 in cancer cells, which could be probed in real-time by monitoring the CO generation by using PERS. Under the same conditions, the rate of formation of CO in healthy cells was relatively higher in comparison to the cancer cells. Additionally, molecular data revealed that AuNCs have the potential to suppress the up-regulation of HO-1 in cancer cells during cisplatin treatment at a lower concentration. As up-regulation of HO-1 has a significant role in cell adaptation to oxidative stress in cancer cells, the ability of AuNCs in suppressing the HO-1 overexpression will have a remarkable impact in the development of nanoformulations for combination cancer therapy. This exploratory study demonstrates the unique possibilities of PERS in the real-time monitoring of endogenously generated CO and thereby the dynamics of HO-1 in live cells, which could expedite our understanding of the signaling action of CO and HO-1 in cancer progression.