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Cancer Genetics

Cancer Genetics

10% of all cancers are hereditary. This means that pathologic mutations in certain genes specific to that organ pass from one generation to another. If a person carries one of the abnormal genes, they are much more likely to develop cancer at some stage of their life than normal people and may pass the same risk to their own children.

Familial history is important in breast, colon, ovarian , prostate, melanoma and endocrine cancers. If you have one or more of these cancers in your family, second or third degree relatives, it is recommended to consult your doctor.

10% of all cancers are hereditary. This means that pathologic mutations in certain genes specific to that organ pass from one generation to another. If a person carries one of the abnormal genes, they are much more likely to develop cancer at some stage of their life than normal people and may pass the same risk to their own children.

Familial history is important in breast, colon, ovarian , prostate, melanoma and endocrine cancers. If you have one or more of these cancers in your family, second or third degree relatives, it is recommended to consult your doctor.

Basic Concepts in Cancer Genetics

1.“Germline” mutation: These are the mutations that occur in germ cells (germ cells; sperm or ovum) in the gonads. Individuals carrying such a mutation can pass it on to their children. The child who receives the mutation will carry that mutation not only in germ cells, but in all the cells of his body. Germline mutations are responsible for hereditary cancers.

2.Somatic mutation: Mutations that occur in body cells other than germ cells, that is, somatic cells. Such mutations do not pass on to the next generation; their biological consequences only affect the individual from which they arise. Somatic mutations play a role in the development of sporadic cancers that do not have hereditary features.

3.Proto-oncogen: These genes play a role in cell proliferation. Cell proliferation is normally carried out according to physiological requirements and controlled. The major functions of protoncogenes are shown below.

  • Transcription factors
  • Growth factor and growth factor receptors
  • Suppression of apoptosis
  • Modification of chromatin
  • Intracellular signal transduction
  • Membrane-related G proteins
  • Tumor suppressor genes: These genes play a negative role in cell proliferation. Tumor suppressor genes that directly suppress proliferation are called at gatekeeper type genes.

Genetic predisposition to cancer

Cancer is a clonal disease that develops as a result of changes in genetic material and changes in the micro and macro environment. In some cancers, genetic factors cause this multi-step process to begin easily. In this case, there is a “genetic predisposition censer for cancer. Thanks to advances in molecular genetics, different genes have been identified that lead to inheritance of cancer susceptibility. It is known that families / individuals carrying mutations of these genes carry a high risk of cancer. Family studies of different cancers show that the risk of cancer is increased in the first and second degree relatives of the affected patient compared to the normal population. Hereditary form of cancer; The diagnosis is characterized by early diagnosis, high penetrance, bilateral involvement in double organs, inheritance from both parents, and coexistence with other types of tumors. It is defined as hereditary cancer if the same type of cancer is seen in the family and as the cancer family when different types of cancers are seen. The presence of the following in the family should be considered as important clues in case of susceptibility to cancer:

  • Cancer in 3 generations
  • Having 2 or more individuals with cancer in one generation
  • Individuals diagnosed below the average age
  • Having more than one cancer
  • The presence of coexisting cancers in some syndromes
  • Breast and ovary
  • Colon and uterus
  • Breast and thyroid
  • Melanoma and pancreas
  • Sarcoma and leukemia

The genes responsible for the development of cancer susceptibility are tumor suppressor genes. Tumor suppressor genes encode proteins that control cell cycle or provide DNA repair. With these functions, they are responsible for maintaining and sustaining the integrity of the genome. They are divided into two main groups: gate-keepers and care-takers. Loss of heterozygosity (LOH) in these genes causes accumulation of mutations in the cell.