# Cancer Treatment: An Overview of Pulsed Electric Field Utilization and Generation
## 2 The Main Hallmarks of Cancer  
Cancer is a genetic disease that makes cells divide and grow abnormally without being regulated by the human body and disrupts the control of cellular proliferation, differentiation, and death. This genetic disease can develop in any part of the body and travel to other parts (metastasis) through the bloodstream or lymph system [20]. Cancer results from mutations in DNA and genes. There are 14 hallmarks of cancer, shown in Figure 1, that have been defined; among the differences between normal and cancer cells are that cancer cells [21; 22]:  
* Ignore signals that tell them to grow as normal cells, resulting in their undergoing abnormal growth and proliferation.
* Ignore signals that tell them to stop dividing or to undergo programmed cell death (apoptosis).  
* Deceive the immune system and reprogram it to support the growth and proliferation of cancer cells and prevent immune cells from killing them.
* Can induce the generation of new blood vessels (angiogenesis) near the tumour to supply the growing tumour with nutrients and oxygen and facilitate the removal of waste products.  
Normal and cancer cells have different electrical properties, and even these characteristics change with cancer cell development; thus they can be used as indicators of infection and cancer development level. In general, a normal cell has higher electrical capacitance than a cancer cell. Studies report that this is for many reasons, including: (1) the diameter of a cancer cell is typically larger than that of its counterpart normal cell (e.g., a lung cell), although the diameters of certain cancer cells, such as those in breast and liver cancer, are smaller than those of their counterpart normal cells, which shows that the diameter of the cell is not the only parameter that affects capacitance [12]; (2) the permittivity of cancer cells is lower than that of a normal cells, (3) cancer cells have a higher water concentration; and (4) cancer induces changes in cell permeability, which imply changes in the concentration of ions; in addition, it has been found that cancer cells have higher concentrations of chlorine and sodium and lower concentrations of magnesium, potassium, calcium, and zinc [12]. All normal cells of different tissue types show higher electric capacitance in comparison to their counterpart cancer cells [12], while both types of cells show negative relations with the electric field frequency (i.e., the cell capacitance decays as the frequency increases). Generally speaking, measuring the capacitance and voltage response of cells can help dif  
Figure 1: The fourteen hallmarks of cancer, according to the last update in 2022 [22].  
ferentiate between normal and cancer cells; however, it cannot help differentiate between different cancer types, as they share a narrow capacity range [12].  
Tumours can be benign, which is usually not harmful unless they are in parts of the body that can lead to blockages (e.g., the hepatic portal vein or coronary artery) [23]. Among malignant tumours, some can be controlled/treated; in general, however, they are difficult to cure/eradicate. Cancer usually starts with a malignant tumour. Malignant cancer can start from benign tumours as well, such as in the case of colon cancer starting from colon polyps. Table 1 compares and summarizes benign and malignant tumours. Treatment modalities vary widely, and include surgery, chemotherapy, radiotherapy, immunotherapy, and hormonotherapy [24; 25]. Treatment via TTF is an emerging non-invasive technology that generates a pulsed electric field to target and disrupt tumour cell division in order to prevent cancer cell growth and proliferation.