Last month we celebrated World Cancer Day. There isn’t much awareness. Almost everyone has heard about this disease yet most seem to know very little about it. Cancer is a condition wherein cells start growing and dividing in an uncontrolled manner. It is a leading cause of death worldwide. 9.6 million deaths were estimated to be caused by cancer alone in 2018. 70% of these deaths were noticed in low- and middle-income countries. Smoking is the most serious risk factor and has led to 22% of cancer related complications.
The starting point of cancer is gene change, which can trigger just one or a few cells to grow and multiply faster than the normal cells. This can lead to a growth or extrusion known as tumor. This event usually starts in a specific part of the body, but in most cases, cancer cells begin to spread to the surrounding healthy cells, tissues, and organs. This process is called secondary tumor or metastasis and it may result in serious damage of the immune system and other harmful effects in body systems which can be fatal. Cancers are divided into different categories depending on the cell type they start from: carcinomas, lymphomas, leukemias, brain tumors and sarcomas.
Lifestyle increases cancer risks besides affecting quality of life. High body mass index, low fruit and vegetable intake, lack of physical activity, tobacco use, and alcohol represent the top 5 risk factors that are responsible for one-third of cancer deaths. Cancer treatment is influenced by many factors such as the location and the size of the tumor, metastasis, patient’s health condition. Different treatment types applied by doctors are surgery, chemotherapy, radiotherapy, hormone therapy, immunotherapy, and stem cell transplants. Radiation is usually the first recommended option and is quite effective in avoiding the surgical route as it can easily prevent the spread of the disease. However, short or long term side effects due to the exposure to radiation are common and the long term effects can be permanent. Chemotherapy is another preferable treatment option but its adverse effects are more severe and may persist for many months or even years after completion.
The methods as mentioned above can quite effectively treat cancer but they often cause damages in non-malignant tissues, cells, and organs. Researchers very recently started focusing on the development of better alternative treatment methods, such as precision or personalized medicine. The goal of this very new procedure — that is not aimed only at cancer — is to create a more custom-shaped cure for each patient. In theory, a test of the patient’s genes are carried out at the beginning of the process and according to its results, the most appropriate treatment is selected. This approach is in its very first stages at the moment and researchers need to prove that it can be effectively applied for all types of cancer.
A quite novel and promising research area in pharmaceuticals is nanomedicine, which can be defined as nanotechnology — technology involving materials sized between 1 and 100 nm — for the use in fields of health and medicine. The nanocarriers have quite interesting and useful properties; their nanoscale size — one nanometer is about as long as your fingernail grows in one second — and their shape and surface can be easily modified for better targeting to the diseased areas and the release of the drug in a desired and more controlled way. How do nanoparticles selectively gather in the diseased areas? Tumor tissues differ a lot from the healthy ones. The environment in the surrounding area of the cancer cells is acidic in contrast to the neutral conditions that are present in the normal cells. Apart from that, their structure is different. Tumor cells are leaky and have pores on their surface — Enhanced Permeability and Retention effect (EPR effect) — which can favor nanocarriers accumulation.
A way to protect the healthy tissues from the highly toxic chemotherapeutic drugs is by applying stimuli. Internal and external stimuli can be used in order to guide the nanoparticles to the desired region for targeted controlled drug release and consequently, to reduce the exposure of the healthy areas to the cancer drugs. Internal stimuli include changes in pH, redox, ionic strength, and stress in target tissues. The acidic environment of the tumors compared to the neutral environment of the blood and the healthy tissues may be the starting point for the development of drug carriers that are designed to selectively release the drug in the cancer cells. Temperature, light, ultrasound, magnetic force, and electric fields are external (physical) stimuli. Hyperthermia in the tumor caused by increasing the temperature up to 42 ºC results in increased permeability of blood vessels thereby making the delivery of the nanocarriers to these areas feasible. Near-IR light can enhance their distribution into the body compared to UV light. Ultrasound systems may be used for cancer diagnosis by activating the release of contrast agents. The accumulation of the nanoparticles in specific places can be contributed by magnetic and electric fields.
Most of these drugs are almost water insoluble, making drug delivery difficult. By loading these drugs in these tiny but miraculous drug carriers, their “journey” in the blood circulation becomes easier, as they are not detected as “bad agents” by the immune system and they are not removed before they reach the desired site. Nanomedicines can also be used as ‘theranostics’ with appropriate modification, which means that they have the potential for detection of cancer in early stages besides effective treatment.
Various types of nanocarriers such as lipid-based, polymer-based, inorganic, viral and drug-conjugated nanoparticles are currently being explored. Some of these systems have successfully proved their merit and worth during clinical trials and have been recently approved for cancer treatment. Big things come in small packages. Nanomedicines are expected to dramatically change cancer treatment in the next years.