Cancer is a generic term used to describe a group of diseases which has been mutated from a single cell. These cells differentiate uncontrollably as cell proliferation occurs continuously and spread to other parts of the body (Gabriel, 2007; Macdonald, Ford and Casson, 2004). According to Starr and McMillan (2008), there are two types of tumors, one is the benign tumors which is enclosed within a capsule made up of fibrous or connective tissues and does not spread to other parts of the body. On the other hand , the malignant tumor is life threatening which differentiates rapidly, affects or kill off other cells surrounding it and metastasize in other parts of the body. However , there is also a possibility of the benign tumor transforming into a malignant tumor after some time such as colon cancer if left untreated.
There are many factors that causes cancer such as the use of tobacco which is common among smokers. Currently, eight cancers is known to be caused by tobacco and they are lung, bladder, pancreatic, stomach etc.(Colditz & Fisher, 2005). Carcinogenic substance forms free radicals when exposed to the body causes alteration to the genetic code as certain segments of DNA are being affected due to the damage on the nucleus of the cell. Besides that, cancer may also be inherited as it can be a multigenerational affair. A cancer gene can be inherited which may transform into a malignant tumor over time or when triggered by environmental factors (Ahluwalia, 2005). An example is the BRCA1 and BRCA2 genes which causes the familial breast cancer. BRCA1 leads to both ovarian and breast cancer whereas BRCA2 mainly causes breast cancer only but causes a high risk on the formation of other cancers such as prostate, pancreatic and laryngeal cancer (Macdonald, Ford and Casson, 2004).
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Moreover, environmental factors which are exposures faced daily such as carcinogenic compounds eg. tobacco smoke and asbestos, UV light from the sun as well as radiation contributes to the formation of tumors. High exposure to UV light may lead to skin cancer such as the Nonmelanoma skin cancer. Radiation from the natural environment comes from soil, cosmic rays and radon whereas human-made radiation such as medical procedures, eg. x-ray or jobs such as uranium miners and nuclear industries workers increases the risk of cancer (Ullrich, 2005). Viruses can also be linked to cancer as they have the tendency to cause genetic change to the cells, causing them to become cancerous (Higginson, Muir & Murioz, 1922). Two RNA viruses which are the Retroviridae and Flaviviridae which includes the retroviruses human T-lymphotrophic virus(HTLV) , human immunodeficiency virus(HIV) and the flavivirus hepatitis C virus(HVC). According to Buchschancher & Wong (2005), the HTLV type 1(HTLV-1) directly leads to the T-cell leukemia(ATL) whereas the HIV and HCV contributes to the development of malignant cancers indirectly.
The cell cycle is the fundamentals in controlling proliferation process where cells undergoes differentiation which results in cell division and DNA duplication. The cell cycle involves 4 phases which are the first gap phase (G1), DNA replication (S), second gap phase (G2), and the M phase (mitosis). Besides that, there is also an additional phase known as the resting phase (G0) for cells and it occurs when mitogens are unavailable or the amounts of nutrients available are mediocre. In cancer, mutations and misregulations occurs usually at the cell cycle and checkpoint genes. According to Reed (2005) there are two basic requirements for cells to undergo cell differentiation uncontrollably, firstly the proliferation signals of the cell has to be strong enough to override the restraints internally and environmentally. Secondly, is the dismantling on the barrier of senesces to render tumor cells immortal. Besides that, cancer and genomic instability occurs when the genes involved in the cell cycle components are mutated when the checkpoints are being deregulated (Macdonald, Ford and Casson, 2004).
Apoptosis is the process of cell death which is an active process and are removed through phagocytosis before they disintegrate. Proliferation and apoptosis are cross linked. Example, Retinoblastoma protein (Rb) which is a regulator of the cell-cycle progress promotes apoptosis where it works as a cell-cycle pathway between the G1 and the S phase (Zinkel & Korsmeyer, 2005). According to Macdonald, Ford and Casson (2004), apoptosis is being controlled by tumor suppressor genes and proto-oncogenes. Tumor suppressor genes such as the p53 reduces apoptosis and leads to the growth of tumor as it exerts tumor suppressor activity by not allowing cells which has damaged DNA to go through the cell cycle but along the apoptotic pathway. Apoptotic regulators are important in suppressing tumors and prevent their development.
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In conclusion, cancer may be prevented in many ways such as through the consumption of herbs and vitamins. These agents contains antioxidants which prevents oxidative damage and thus help decreasing the risk of cancer eg. green tea, vitamin A, vitamin C, selenium. As for cancer patients, complementary and alternative medicine (CAM) can also be used as supportive care, treatment and also as secondary preventions by others eg. soy, maitake mushroom extract and beta-glucans, shitake mushroom extracts etc.(Smith, Frankenfield & Souba, 2005).