Cancer Causes

What is cancer?

Cancer is the second deadliest disease in the world. The word cancer originated from the Greek word karkinos. It was described by physician Hippocrates (460-370 B.C) as carcinoma tumors.¹ Carcinoma means multiple new cells forming new tissue in the skin layer. This means that cancer is developed from normal cells due to damage in DNA (deoxyribonucleic acid). When  cell growth increases in a particular part of the body, cells begin to develop and multiply abnormally and are then referred to as tumors.¹

Cancer can be inherited from the family, generally from parents. Mostly, people with smoking and alcohol habits can also develop cancer cells. In addition, the disease can be caused by several viruses called cancer-causing viruses, for example, human immunodeficiency (HIV).¹

Cancer causes and risk factors

Some risk factors can elevate cancer growth such as unsafe sex, contaminated injections, obesity, smoking, alcohol, and less nutrient intake:²

• Unprotected sex with an infected partner can lead to HIV and if not treated, it can lead to acquired immunodeficiency syndrome (AIDS). HIV can lead to various types of cancer including lung, liver, and more. Among HIV-infected patients, almost 90% are heavy cigarette smokers.³ As the virus multiplies in the body, the immune system gets affected
• Being overweight can lead to obesity, and according to the International Agency for Research on Cancer obesity is one of the causes of cancer. About 20% of cancer cases are due to being overweight or obese⁴
• Lung cancer is caused by a viral or bacterial (Chlamydophila pneumoniae) infection that triggers the inflammatory system of the body. Infections should be cured during their initial stage to prevent them from spreading into the body. Smoking and consuming alcohol can elevate the chances of developing a malignant tumor⁵
• Eating habits can also be a risk factor to develop cancer, namely, bladder cancer, prostate cancer, and kidney cancer are partly dependent on metabolism⁶

The DNA mutations

Cancer is caused by mutation, an error caused by mutagens in the DNA sequence that leads to dysfunction of the DNA, meaning it destroys the structure and affects its replication and transcription. Mutations can arise in two ways:

1. Spontaneous while the two daughter cells differentiate and mismatch their positions
2. When the mutagen directly attacks the parent DNA.⁷ To prevent this, a mechanism of DNA repair takes place where several pairs of networking repair systems will come together to cope with the damaged DNA

DNA repair mechanism

There are respective pairs assigned to a function, for example, a pair called nucleotide excision repair (NER) will only target DNAs that are damaged by UV rays. Many repair proteins are functioning in the nucleus to keep the DNA working properly. The repair system consists of several processes such as base excision repair (BER), nucleotide excision repair (NER), mismatch repair (MMR), and double-strand break (DSBs), each pair performing their respective role to repair DNA.⁸

DNA proteins

When cancer cells start attacking the DNA, it mainly targets the protein in it, when Alkylguanine DNA methyltransferase (AGT) is elevated, it directly correlates its resistance against the tumor, with AGT as the first repair target for cancer therapeutics. It also creates resistance against the side effects of chemotherapy. During BER, methylpurine DNA glycosylase (MPG) eliminates the damaged part of the DNA and following uracil DNA glycosylase (UNG), and thymine DNA glycosylase (TDG) eliminates specific lesions. Some BER proteins (DNA ligase, XRCC1) act as a sensor when there is a breakage in the DNA.⁹ If these repairing pairs don’t function due to the increased growth of mutagens it leads to cancer.

Conclusion

Cancer is a highly severe disease that is formed from normal cells of the body when cell growth is out of control to form cancer cells. It comes in various forms such as blood cancer, lung cancer, throat cancer, liver cancer, prostate cancer, and more. Cancer can be caused by the transmission of viruses or can be inherited. When cancer cells develop it starts to destroy the immune system, thus attacking the DNA sequence which plays an important role in the body, affecting DNA replication and transcription,  leading to dysfunction of  DNA. Despite the several repair systems with specific DNA protein mechanisms, the process sometimes fails to repair, causing mismatched pairs in sequencing and destruction of proteins in the DNA, due to the dominant mutagens, that lead to the deadliest disease which is cancer.