CAUSES OF CANCER GENETIC AND CHEMICAL CARCINOGENS

CAUSES OF CANCER GENETIC AND CHEMICAL CARCINOGENS

Aetiology or causes of cancer
The aetiology of cancers can be classified into four main categories

Genetic causes or carcinogens


Chemical causes or carcinogens

Physical causes or carcinogens

Viral causes or carcinogens


 Genetic causes or cancer

One widely held opinion is that cancer is a genetic disease that arises from an accumulation of mutations that leads to the selection of cells with increasingly aggressive behavior. These mutations may lead ei­ther to a gain of function by oncogenes or to a loss of function by tumor suppressor genes. Most mutations in cancer are somatic and are found only in the cancer cells. Most of our information on human cancer genes has been gained from hereditary cancers. In the case of hereditary cancers, the individual carries a particular germline mutation in every cell. In the past decade, more than 30 genes for autosomal dominant hereditary cancers have been identified A few of these hereditary cancer genes are oncogenes, but most are tumor suppressor genes, Though hereditary cancer

syndromes are rare, somatic mutations that occur in sporadic cancer have been found to disrupt the cellular pathways altered in heredi­tary cancer syndromes. suggesting that these pathways are critical to normal cell growth. cell cycle and proliferation

The following criteria may suggest the presence of a hereditary cancer
. Tumor development at a much younger age than usual
. Presence of bilateral disease
. Presence of multiple primary mutiguancies
. Presentation of a cancer in the less affected sex (e.g.,male breast cancer
 Clustering of the same cancer type in relatives

. Cancer associated with other conditions such as mental retardation or pathognomic skin lesions

It is crucial that all surgeons taking care of cancer patients be aware of hereditary cancer syndromes, since a patient's genetic background has significant implications for patient counseling , planing of surgical therapy


Some examples of the more common hereditary cancer syndromes like as

1- rb1 Gene and Hereditary Retinoblastoma

2- P53 and U-Fraumeni Syndrome

hCHK2 li-fraumeni Syndrome. and Hereditary Breast cancer-3

BRCA1, BRCA2, and Hereditary Breast-Ovarian -4
Cancer Syndrome

5- APC Gene and Familial Adenomatous Polyposis

6- Mismatch Repair Genes and Hereditary Non polyposis Colorectal Cancer
7- P16 and Hereditary Malignant Melanoma
8- E- Cadherin and Hereditary Diffuse Gastric Cancer

Chemical Causes or Carcinogenes

the report that cancer could be caused by environmental factors it found that 60­ to 90% of cancers all! thought to be due to environmental factors
chemicals carcinogens are classified into three groups based on how they contribute to tumour formation
the first group of chemical agents the genotoxins which can initiate carcinogenesis by causing a mutations
the second group the co-carcinogens by themselves can not causes cancer but potentiate carcinogenesis by
enhancing the potency of the genotoxins
the third group tumour promoters enhance tumour formation when given after exposure to genotoxins
some important examples for chemical agents or carcinogens  and it is relation to cancer causing
1- Aflatoxins related to liver cancer
2- Aresnic related to skin cancer
3-Benzene related to leukemia
4-Benzidine related to bladder cancer
5- Berylium related to lung cancer
6- Diethylstilbestrol  related to vaginal and cervical clear cell adenocarcinoma
7- Estrogen replacement therapy related to endometrial and breast cancers
8- tobacco products smokeless related to oral cancer
9- Tobacco smoke related to lung cancer oral cancer pharyngeal laryngeal esophageal cancers pancreatic liver renal bladder cervical cancers and leukemia
Coal tar related to skin and scrotal cancers -10

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