Oncogenisis and Tumor Markers

Oncogenesis

• Human cancer development is a result of a genetic disease

• protoncogenes• Tumour suppressor genes.• Regulatory expression of these genes can be

seen in the normal cells and protein products of these genes are fundamental for normal cell function.

Examples:

• Oncogenes:

Ras, Myc, EGFR,c-erbB1,2,3.

• Tumour suppressor genes:

p53, Rb genes

Carcinogenesis• Multifactorial etiology.

• The tumour suppressor genes or oncogenes would be altered in the presence of carcinogens:

• Chemical carcinogens• Physical agents• Ionizing radiation • Viral agents• Others

Four common types of genetic changes

• Deletion : Loss of tumour suppressor genes • Mutation :p53, Ras• Inversion :Relocate the the oncogenes in• Translocation to DNA areas which will leads

inappropriate transcription.

• Subsequent accumulation of such growth promoting genetic defects forms the basis of current multi step process of tumourigenesis.

• This multi step process includes.

Initiation.

Promotion.

Tumour progression.

• Many of the known oncogenes and oncosupressor genes help control mitosis and apoptosis.

• Lack of this control would leads to development of malignancy.

• Genetic disease.

Tumour marker

• Substance or group of substance produced by the tumour

• Which can be used as a indicator to detect the presence of the tumour.

A tumour marker should be indicative of :

• Tumour susceptibility of the patient.

• Severity or virulence of the tumour.

• Prognosis of the disease.

• Tumour burden (Including metastasis) .

• Treatment response.

Types of tumour markers:

• Histopathological markers.

• Immuno markers.

• Genetic markers.

• Hormonal markers.

• Protein products of tumours

Carcino-embrionic antigen

Apoptosis related genes

• Bcl2 family:

Bcl2, Bcl XL , Bax , Bad.

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