Reactive Oxygen Species or ROS are basically the chemicals that are highly reactive and are formed from oxygen (O2). These include peroxides, singlet oxygen, superoxide, and hydroxyl radicals. ROS naturally belong to cellular functioning and are present in normal cells at stationary levels. More clearly, Reactive Oxygen Species is a group of molecules that have advanced as regulators of certain vital signaling pathways.
ROS and Cancer Tumor
Cancer is a life-threatening condition that, when diagnosed, puts individuals in distress. This is why the current studies focus more on its prevention and promising treatment options.
To understand the impact of ROS on tumors, it is important to know the cause of its high concentration.
Factors like high pressure, hypoxia, acidity, dense blood vessels, and vigorous metabolism constitute the tumor microenvironment. Due to the strong reproduction ability and rapid growth rate, the cancer cells demand more nutrients than the normal cells in the body. As a result of this and anaerobic respiration of tumor cells, a large number of oxidation reactions occur. This leads to a higher concentration of Reactive Oxygen Species free radicals. ROS, thus, clearly produces a therapeutic effect on tumors to some extent.
ROS and Medicines
With the help of the reduction mechanism of the GSH (glutathione) redox system, multiple cells buffer a specific amount of Reactive Oxygen Species. External factors including chemotherapeutic agents can significantly stimulate mitochondria and lead to excessive production of ROS. This further can cause apoptosis (programmed cell death) due to the release of cytochrome C and calcium ions.
Almost all chemotherapeutic agents tend to increase ROS in order to target cancer cells. However, such exposure to ROS may reduce the chemotherapy efficacy to some extent. Further, new delivery techniques including nanoparticle delivery systems can increase cellular Reactive Oxygen Species levels in cancer and evidently reverse drug resistance. Also, other agents can be researched to target some of the cellular compartments for the generation and maintenance of ROS for a while.
ROS and Cell Death
To kill the transformed cells, the activation of PCD (programmed cell death) is necessary. This is done by ROS. Moreover, the Reactive Oxygen Species induce the main three components that are vital for the opening of the voltage-dependent anion-selective channels. It also triggers PCD or apoptosis by increasing or inactivating the ubiquitination of the pivotal protein Bcl-2 that possesses anti-apoptotic properties. This is done by altering the intracellular levels of BAD and BAX (proteins). For example, chemotherapeutic drugs that are platinum-based elevate ROS levels. As a result, this promotes PCD. Furthermore, drugs like bortezomib injection (a proteasome inhibitor) induce programmed cell death in cancer cells by influencing the Bax/Bcl-2 ratio and increasing the level of ROS in the body.
There is a complex interconnection between cancer and Cellular Reactive Oxygen Species. To be specific, cancer cells grow on ROS levels that are high as compared to their normal counterparts. Increasingly, medications are being evaluated in this regard (ROS elevation) for the treatment of different types of cancer.