Human cancer development, or oncogenesis, results from genetic changes in oncogenes and tumor suppressor genes. Oncogenes like Ras, Myc, and EGFR promote cancer when overexpressed, while tumor suppressors like p53 and Rb inhibit cancer when functioning normally. Genetic changes from carcinogens, radiation, viruses, or other sources can delete or mutate these genes, altering the control of mitosis and apoptosis and leading to uncontrolled cell growth and the multi-step development of tumors over time. Tumor markers in the blood can indicate the presence, severity, or progression of cancers and help guide treatment responses.

1. 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.

2. Examples: Oncogenes: Ras, Myc, EGFR,c-erbB1,2,3. Tumour suppressor genes: p53, Rb genes

3. 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

4. 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.

5. 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.

6. 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.

7. 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.

8. 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.

9. Types of tumour markers: Histopathological markers. Immuno markers. Genetic markers. Hormonal markers. Protein products of tumours Carcino-embrionic antigen

12. Apoptosis related genes Bcl2 family: Bcl 2 , Bcl XL , Bax , Bad. ---ve ++ Apoptosis Bcl2 Bax Bcl xL p53 Bad