Cancer becomes a global problem, so that many researchers focus on this issue. Some researcher also won nobel prizes for their works in this field because of their important finding. To help us understand about recent advances in cancer research this lecture brings an overview of cancer.
Cancer is defined by their character of abnormal cells that divide without control and be able to invade other tissue. Invasiveness is cancer capacity to spread to other parts of the body. This capacity is mediated through lymph and blood vessel. So cancer cells can spread to distant place.
Classification
Hundreds type of cancer have been discovered recently. Basically, they named by their first affected organ:
- Carcinoma : cancer that begins in the skin or tissue that cover (line) internal organ. Histological character of this type is epithelial.
- Sarcoma : cancer that starts from connective tissue, such as bone, fat, cartilage, muscle, blood vessel.
- Leukemia : cancer that starts from blood-forming tissue that produces abnornal blood cells
- Lymphoma and myeloma : cancer that affects immune system cells
- Central nervous system cancer : cancer that begins from central nervous system, brain and spinal cord.
Generally, Naming of cancer always begin with tissue origin and followed by cancer type as mentioned above. For example cancer that originated in striated muscle tissue is called rhabdomyo sarcoma. Further, each cancer type will be classified into several subtypes for clinical importance, Bethesda classification system for cervical cancer etc. In clinical setting they also classified based on stage and grade difference.
Cancer pathology is started from abnormal cell, the basic functional unit of human body. Understanding cellular pathology in cancer formation is essential to design treatment strategy. Normally, human body is composed by many types of cell that grow, divide, and death in controlled mechanism. However, sometimes this process is interrupted. Genetic material of the cells, the DNA, can be damaged by many environmental factors. This event leads to interruption of cell division or cell death. They may divide without control and do not die when they should. So that, these new cells will form an abnormal mass which is called a tumor.
Cancer treatment
Actually tumor means enlargement of tissue, in this case because of increment of cell number. So, not all tumor is cancerous. Some of tumors are benign tumor. Benign tumors are differentiated to the malignant one on their invasiveness. Benign tumors do not spread to other tissue. This tumor will ‘stay’ in their origin tissue and cause mass effect because of enlargement, but none of them can spread to other tissue. So that, benign tumor can be evacuated by surgical procedure only. In the other hand, malignant tumor (cancerous) has capacity to spread to other tissue involving lymphatic or blood vessel (metastasis). That’s why in certain stage of cancer they can’t be eradicated by surgical procedure only. In spite of surgical treatment, today another available treatment modalities are chemotherapy, radiotherapy and immunotherapy.
Overview of treatment modalities
| Therapy | Brief explanation |
| Chemotherapy | Chemotherapy is treatment option that uses drugs to destroy cancer cells. The drug affects cancer cells and other cells that divide quickly. Chemotherapeutic drugs may cure cancer, control cancer cell division or ease cancer symptoms. Example: cisplatin (alkylating agent), taxol (antimicrotubule drug) |
| Radiotherapy | Radiotherapy is given by transferring the beam of ionizing radiation. Radiation of gamma rays and X-rays can be focused to target organ, where the cancer cells reside. Radiation beam is produced by radioactive particle (for example Cobalt-60) in the cyclotrone. Anather way to transfer the radiation is using implant (sealed source radiotherapy) that present very close or inside the tumor. It is called brachytherapy (brachy means near). Brachytherapy commonly used to treat Nasopharyngeal cancer. |
| Immunotherapy | Immunotherapy can be delivered in two ways: stimulating patient’s immune system to reject cancer cells, or administration of antibody in which case the patient’s immune system is recruited. Many monoclonal antibodies have been developed recently, for example: Rifuximab, Cetuximab etc. |
Concept of personalized medicine in cancer patient
Understanding of molecular basis in cancer pathology will give a complete perspective of the disease. Thus support a better treatment strategy, and also the discovery of novel treatment. In Taiwan, The National Cancer Institute (NCI) is developing a concept of personalized treatment based on the biology of individiual patients and their cancers. Not only focus on prevention, diagnosis and treatment, NCI also develop approaches to predict how individual may respond to any given treatment based on molecular biology.
By definition, personalized treatment means a medical model emphasizing in general the customization of healthcare, with all decisions and practices being tailored to individual patients in whatever ways possible. It mainly involves the systematic use of genetic or other information about an individual patient to select or optimize that patient's preventative and therapeutic care. A revolutionary concept of personalized medicine in cancer promises a better therapeutic approach, improve patient outcome and reduce unnecessary treatment. First targeted therapy intruduced was Herceptin for breat cancer treatment. Herceptin is antibody targeted to HER-2. Herceptin combined to chemotherapy effectively reduces reccurance in patients who have specific gene. It means that breast cancer is not a single disease, it’s consists of many subtypes that also need different therapeutic way for optimal cure.
Some of important targets to control cancer cells are cell cycle control and apoptosis. Cell cycle is very important because it is about cell determination, to divide, to stop growing, or to resting cell. Cell cycle mainly divided into two phase: M (mitotic) phase and Interphase (consists of G1, S and G2 phase). In order to determine the progression of cell cycle, there are three check points that will be a critical point to decide the completion of cell cycle. It is just like an ON-OFF switch. Cyclins are proteins that take part in these checkpoint. It binds to Cdk and activate the Cdk active site. Inactivation of Cyclin-Cdks complex may stop the progression of cell cycle. It gives hope in cancer treatment.
In other part, apoptosis also an important issue in cancer treatment. Apoptosis is an integral part of development to maintain homeostasis, in this case to maintain dynamic equilibrium of cell number. If apoptosis is disrupted, cell fail to die then lead to development of tumor. Therefore, cell division and apoptosis should be maintained in a balanced rate. Another way to manage cancer cells is turning on the apoptosis pathway, the caspases pathway. Once caspase is activated, it will become an explosive destroyer that lead cell death.
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