Treatments for cancer using methods other than surgery, chemotherapy, and radiation are being heavily researched. Among such research, using the body’s own immune system to destroy tumors is the one that is most talked about. According to a new study, nanoparticles may be able to aid the immune system in its fight against tumors. The study conducted experimented on mice, which revealed incredible findings. The nanoparticles destroyed the primary tumor cells as well as the distant metastasized tumor cells. The results of the study have made the researchers believe that human clinical trials could soon begin.
Immunotherapy using nanoparticles
The T cells target any foreign bodies or objects that look suspicious, including bacteria, viruses, and tumor cells. When T cells identify a potentially harmful foreign body, they initiate an immunological response cascade that calls upon other immune cells to attack the foreign body. Unfortunately, the response of the T cells is often disrupted by immune checkpoints to prevent any harmful destruction of healthy cells. Tumor cells enhance the expression of these checkpoints and halt the immune response to tumor cells.
Targeting this particular issue, many immunotherapy drugs are currently available to block the overexpression of these checkpoints. These drugs are antibody proteins that inhibit the action of tumor cells on immune checkpoints to enable the immune system to attack tumors. T cells normally surround the tumor and reside in the vicinity of the tumor. Sometimes, tumor cells mutate to large numbers, which in turn creates further targets for the immune cells. Employing this therapeutic technique prolongs the life of cancer patients by several years.
Why has immunotherapy not been used in cancer patients yet?
Although the theory sounds simple, there are various individual patient factors that affect the treatment. Some patients do not respond to the immunotherapy drugs as it has been found to be effective in less than 30% of cancer patients. While in some patients, the checkpoint molecules are successfully blocked, but the T cells are too few to attack the tumor cells. In some patients, the drug works well to block the checkpoint, the T cells are in surplus number but the tumor cells do not express any antigens on their surface to attract the T cells.
In a handful of cases across the globe, the immune system in some cancer patients has miraculously eradicated the tumor cells and any distant metastasis of the tumor cells. These patients had all received radiotherapy to the primary tumor cell, which somehow activated the body’s immune system to aggressively attack the tumor cells specifically. Scientists believe the radiation resulted in the introduction of new tumor antigens that attracted the T cells to attack them.
The study by Lin was conducted with an aim to observe whether nontoxic nanoparticles could activate the immune system to act in the same manner. However, introducing the nanoparticles to the body proved to be difficult as the immune system would recognize it as a foreign object and it would subsequently be engulfed by macrophages. Therefore, it was crucial to minimize the size of the nanoparticles to between 20 and 40 nanometers in size in order to make them undetectable to the immune system. In addition to the extremely minute size, the nanoparticle was coated with a polyethylene glycol shell, which facilitated their survival in blood circulation. The tumor-killing light-absorbing, chlorine-based molecules were inserted deep into the core of the nanoparticles.
With such highly specialized nanoparticles, the tumor killers circulated long enough in the system to attach to the tumor cells. Once the nanoparticles are within the range of the tumor cells, the researchers used infrared light to excite nearby oxygen molecules due to the absorption of the light by the chlorine-based molecules. The excitation of the oxygen molecules resulted in the creation of singlet oxygen, which is a highly reactive form of oxygen that destroys all biomolecules in its vicinity including tumor cells. Not only does it destroy the adjacent tumor cells, but it also results in the release of numerous new tumor antigens that attracts the T cells.
In their latest experiment with the nanoparticles on mice with breast cancer, the researchers didn’t add any chemotherapeutic drugs to the nanoparticles. Next, the tumors were blasted with infrared rays of light, and the results were astounding. The nanoparticles not only destroyed the tumor cells in the breast but also eradicated all metastasized tumor cells from the lungs.
The results have made the researchers hopeful that human clinical trials will soon begin.
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